Prof Hugh Watkins FRS FMedSci

Research Area: Genetics and Genomics
Technology Exchange: Human genetics and Mouse models
Scientific Themes: Genes, Genetics, Epigenetics & Genomics and Cardiovascular Science
Keywords: Genetics, genomics, inherited heart disease
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My interest is in using molecular genetic analysis of cardiovascular disease as a tool to define disease mechanisms and therapeutic targets. I have had a longstanding focus on inherited heart muscle diseases, in particular hypertrophic cardiomyopathy, which is a relatively common Mendelian condition which puts affected individuals at risk of sudden cardiac death.  My group's work, using molecular biological, model organism and clinical research approaches, has lead to the idea that energy compromise is a key disease mechanism; clinical trials are underway to test new medical therapies based on this finding.  Our work on genetic causes of ‘sudden cardiac death’ syndromes has been translated into clinical practice through the Oxford BRC, leading to an NHS commissioned national DNA diagnostic service. This area of my work is integrally linked with the groups of Dr. Charles Redwood and Dr. Houman Ashrafian as we have worked closely together for many years.

I also lead a research group investigating susceptibility genes for coronary artery disease, now the main cause of premature mortality worldwide. With colleagues in Oxford (Profs Farrall and Collins) and in Europe (Prof Hamsten, Karolinska) I established the Procardis study to assemble the large scale clinical collections needed to tackle this challenge; I have since chaired a large international collaboration in this area (the C4D Consortium). Recent findings include evidence that lipoprotein Lp(a) levels are causally related to coronary disease risk and identification of multiple novel common susceptibility variants for coronary artery disease risk. This work is now entering an exciting phase where we can use functional genomic tools to understand new biology, thus drawing on some of the approaches we have developed in our Mendelian genetic work.

Name Department Institution Country
Prof Charles Redwood Cardiovascular Medicine Oxford University, West Wing, John Radcliffe Hospital United Kingdom
Prof Houman Ashrafian Cardiovascular Medicine Oxford University, West Wing, John Radcliffe Hospital United Kingdom
Prof Stefan Neubauer FMedSci FRCP Cardiovascular Medicine Oxford University, John Radcliffe Hospital United Kingdom
Prof Barbara Casadei FMedSci FRCP Cardiovascular Medicine Oxford University, West Wing, John Radcliffe Hospital United Kingdom
Dr Ed Blair Clinical Genetics Oxford University Hospitals United Kingdom
Professor Jenny Taylor (NDM) Wellcome Trust Centre for Human Genetics Oxford University, Henry Wellcome Building of Genomic Medicine United Kingdom
Prof Bill McKenna UCL United Kingdom
Prof Martin Farrall Cardiovascular Medicine Oxford University, Henry Wellcome Building of Genomic Medicine United Kingdom
Prof Anders Hamsten FRCP Atherosclerosis Research Unit, Department of Medicine Karolinska Institutet Sweden
Professor Sir Rory E Collins (NDM) Oxford University, Richard Doll Building United Kingdom
Prof Keith Channon FMedSci FRCP Cardiovascular Medicine Oxford University, John Radcliffe Hospital United Kingdom
Prof Shoumo Bhattacharya FMedSci FRCP Cardiovascular Medicine Oxford University, Henry Wellcome Building of Genomic Medicine United Kingdom
Dr Ben Davies (NDM) Wellcome Trust Centre for Human Genetics Oxford University, Henry Wellcome Building of Genomic Medicine United Kingdom
Golbus JR, Stitziel NO, Zhao W, Xue C, Farrall M, McPherson R, Erdmann J, Deloukas P, Watkins H, Schunkert H et al. 2016. Common and Rare Genetic Variation in CCR2, CCR5, or CX3CR1 and Risk of Atherosclerotic Coronary Heart Disease and Glucometabolic Traits. Circ Cardiovasc Genet, pp. CIRCGENETICS.115.001374-CIRCGENETICS.115.001374. | Show Abstract | Read more

BACKGROUND: -The chemokine receptorsCCR2,CCR5, andCX3CR1coordinate monocyte trafficking in homeostatic and inflammatory states. Multiple small human genetic studies have variably linked single nucleotide polymorphisms (SNPs) in these genes to cardiometabolic disease. We interrogated genome-wide association, exome sequencing, and exome array genotyping studies to ascertain the relationship between variation in these genes and coronary artery disease (CAD), myocardial infarction (MI), and glucometabolic traits. METHODS AND RESULTS: -We interrogated the CARDIoGRAMplusC4D (60,801 cases, 123,504 controls), the MIGen and CARDIoGRAM Exome consortia (42,335 cases, 78,240 controls), and ESP EOMI (4,703 cases, 5,090 controls) datasets to ascertain the relationship between common, low frequency, and rare variation inCCR2,CCR5, orCX3CR1with CAD and MI. We did not identify any variant associated with CAD or MI. We then explored common and low frequency variation in South Asians through PROMIS (9,058 cases, 8,379 controls), identifying six variants associated with MI includingCX3CR1V249I. Finally, reanalysis of the European HapMap imputed DIAGRAM, GLGC, GIANT and MAGIC datasets revealed no association with glucometabolic traits though three SNPs in PROMIS were associated with type II diabetes mellitus (DM). CONCLUSIONS: -No chemokine receptor variant was associated with CAD, MI, or glucometabolic traits in large European ancestry cohorts. In a South Asian cohort, we identified SNP associations with MI and type II DM but these did not meet significance in cohorts of European ancestry. These findings suggest the need for larger studies in South Asians but exclude clinically meaningful associations with CAD and glucometabolic traits in Europeans.

Nikpay M, Goel A, Won HH, Hall LM, Willenborg C, Kanoni S, Saleheen D, Kyriakou T, Nelson CP, Hopewell JC et al. 2015. A comprehensive 1,000 Genomes-based genome-wide association meta-analysis of coronary artery disease. Nat Genet, 47 (10), pp. 1121-1130. | Show Abstract | Read more

Existing knowledge of genetic variants affecting risk of coronary artery disease (CAD) is largely based on genome-wide association study (GWAS) analysis of common SNPs. Leveraging phased haplotypes from the 1000 Genomes Project, we report a GWAS meta-analysis of ∼185,000 CAD cases and controls, interrogating 6.7 million common (minor allele frequency (MAF) > 0.05) and 2.7 million low-frequency (0.005 < MAF < 0.05) variants. In addition to confirming most known CAD-associated loci, we identified ten new loci (eight additive and two recessive) that contain candidate causal genes newly implicating biological processes in vessel walls. We observed intralocus allelic heterogeneity but little evidence of low-frequency variants with larger effects and no evidence of synthetic association. Our analysis provides a comprehensive survey of the fine genetic architecture of CAD, showing that genetic susceptibility to this common disease is largely determined by common SNPs of small effect size.

Huffman JE, de Vries PS, Morrison AC, Sabater-Lleal M, Kacprowski T, Auer PL, Brody JA, Chasman DI, Chen MH, Guo X et al. 2015. Rare and low-frequency variants and their association with plasma levels of fibrinogen, FVII, FVIII, and vWF. Blood, 126 (11), pp. e19-e29. | Show Abstract | Read more

Fibrinogen, coagulation factor VII (FVII), and factor VIII (FVIII) and its carrier von Willebrand factor (vWF) play key roles in hemostasis. Previously identified common variants explain only a small fraction of the trait heritabilities, and additional variations may be explained by associations with rarer variants with larger effects. The aim of this study was to identify low-frequency (minor allele frequency [MAF] ≥0.01 and <0.05) and rare (MAF <0.01) variants that influence plasma concentrations of these 4 hemostatic factors by meta-analyzing exome chip data from up to 76,000 participants of 4 ancestries. We identified 12 novel associations of low-frequency (n = 2) and rare (n = 10) variants across the fibrinogen, FVII, FVIII, and vWF traits that were independent of previously identified associations. Novel loci were found within previously reported genes and had effect sizes much larger than and independent of previously identified common variants. In addition, associations at KCNT1, HID1, and KATNB1 identified new candidate genes related to hemostasis for follow-up replication and functional genomic analysis. Newly identified low-frequency and rare-variant associations accounted for modest amounts of trait variance and therefore are unlikely to increase predicted trait heritability but provide new information for understanding individual variation in hemostasis pathways.

D'Alessandro LC, Al Turki S, Manickaraj AK, Manase D, Mulder BJ, Bergin L, Rosenberg HC, Mondal T, Gordon E, Lougheed J et al. 2016. Exome sequencing identifies rare variants in multiple genes in atrioventricular septal defect. Genet Med, 18 (2), pp. 189-198. | Show Abstract | Read more

PURPOSE: The genetic etiology of atrioventricular septal defect (AVSD) is unknown in 40% cases. Conventional sequencing and arrays have identified the etiology in only a minority of nonsyndromic individuals with AVSD. METHODS: Whole-exome sequencing was performed in 81 unrelated probands with AVSD to identify potentially causal variants in a comprehensive set of 112 genes with strong biological relevance to AVSD. RESULTS: A significant enrichment of rare and rare damaging variants was identified in the gene set, compared with controls (odds ratio (OR): 1.52; 95% confidence interval (CI): 1.35-1.71; P = 4.8 × 10(-11)). The enrichment was specific to AVSD probands, compared with a cohort without AVSD with tetralogy of Fallot (OR: 2.25; 95% CI: 1.84-2.76; P = 2.2 × 10(-16)). Six genes (NIPBL, CHD7, CEP152, BMPR1a, ZFPM2, and MDM4) were enriched for rare variants in AVSD compared with controls, including three syndrome-associated genes (NIPBL, CHD7, and CEP152). The findings were confirmed in a replication cohort of 81 AVSD probands. CONCLUSION: Mutations in genes with strong biological relevance to AVSD, including syndrome-associated genes, can contribute to AVSD, even in those with isolated heart disease. The identification of a gene set associated with AVSD will facilitate targeted genetic screening in this cohort.

Taylor JC, Martin HC, Lise S, Broxholme J, Cazier JB, Rimmer A, Kanapin A, Lunter G, Fiddy S, Allan C et al. 2015. Factors influencing success of clinical genome sequencing across a broad spectrum of disorders. Nat Genet, 47 (7), pp. 717-726. | Show Abstract | Read more

To assess factors influencing the success of whole-genome sequencing for mainstream clinical diagnosis, we sequenced 217 individuals from 156 independent cases or families across a broad spectrum of disorders in whom previous screening had identified no pathogenic variants. We quantified the number of candidate variants identified using different strategies for variant calling, filtering, annotation and prioritization. We found that jointly calling variants across samples, filtering against both local and external databases, deploying multiple annotation tools and using familial transmission above biological plausibility contributed to accuracy. Overall, we identified disease-causing variants in 21% of cases, with the proportion increasing to 34% (23/68) for mendelian disorders and 57% (8/14) in family trios. We also discovered 32 potentially clinically actionable variants in 18 genes unrelated to the referral disorder, although only 4 were ultimately considered reportable. Our results demonstrate the value of genome sequencing for routine clinical diagnosis but also highlight many outstanding challenges.

Dass S, Cochlin LE, Suttie JJ, Holloway CJ, Rider OJ, Carden L, Tyler DJ, Karamitsos TD, Clarke K, Neubauer S, Watkins H. 2015. Exacerbation of cardiac energetic impairment during exercise in hypertrophic cardiomyopathy: a potential mechanism for diastolic dysfunction. Eur Heart J, 36 (24), pp. 1547-1554. | Show Abstract | Read more

AIMS: Hypertrophic cardiomyopathy (HCM) is the commonest cause of sudden cardiac death in the young, with an excess of exercise-related deaths. The HCM sarcomere mutations increase the energy cost of contraction and impaired resting cardiac energetics has been documented by measurement of phosphocreatine/ATP (PCr/ATP) using (31)Phosphorus MR Spectroscopy ((31)P MRS). We hypothesized that cardiac energetics are further impaired acutely during exercise in HCM and that this would have important functional consequences. METHODS AND RESULTS: (31)P MRS was performed in 35 HCM patients and 20 age- and gender-matched normal volunteers at rest and during leg exercise with 2.5 kg ankle weights. Peak left-ventricular filling rates (PFRs) and myocardial perfusion reserve (MPRI) were calculated during adenosine stress. Resting PCr/ATP was significantly reduced in HCM (HCM: 1.71 ± 0.35, normal 2.14 ± 0.35 P < 0.0001). During exercise, there was a further reduction in PCr/ATP in HCM (1.56 ± 0.29, P = 0.02 compared with rest) but not in normals (2.16 ± 0.26, P = 0.98 compared with rest). There was no correlation between PCr/ATP reduction and cardiac mass, wall thickness, MPRI, or late-gadolinium enhancement. PFR and PCr/ATP were significantly correlated at rest (r = 0.48, P = 0.02) and stress (r = 0.53, P = 0.01). CONCLUSION: During exercise, the pre-existing energetic deficit in HCM is further exacerbated independent of hypertrophy, perfusion reserve, or degree of fibrosis. This is in keeping with the change at the myofilament level. We offer a potential explanation for exercise-related diastolic dysfunction in HCM.

Nüesch E, Dale C, Palmer TM, White J, Keating BJ, van Iperen EP, Goel A, Padmanabhan S, Asselbergs FW, EPIC-Netherland Investigators et al. 2015. Adult height, coronary heart disease and stroke: a multi-locus Mendelian randomization meta-analysis. Int J Epidemiol, | Show Abstract | Read more

BACKGROUND: We investigated causal effect of completed growth, measured by adult height, on coronary heart disease (CHD), stroke and cardiovascular traits, using instrumental variable (IV) Mendelian randomization meta-analysis. METHODS: We developed an allele score based on 69 single nucleotide polymorphisms (SNPs) associated with adult height, identified by the IBCCardioChip, and used it for IV analysis against cardiovascular risk factors and events in 21 studies and 60 028 participants. IV analysis on CHD was supplemented by summary data from 180 height-SNPs from the GIANT consortium and their corresponding CHD estimates derived from CARDIoGRAMplusC4D. RESULTS: IV estimates from IBCCardioChip and GIANT-CARDIoGRAMplusC4D showed that a 6.5-cm increase in height reduced the odds of CHD by 10% [odds ratios 0.90; 95% confidence intervals (CIs): 0.78 to 1.03 and 0.85 to 0.95, respectively],which agrees with the estimate from the Emerging Risk Factors Collaboration (hazard ratio 0.93; 95% CI: 0.91 to 0.94). IV analysis revealed no association with stroke (odds ratio 0.97; 95% CI: 0.79 to 1.19). IV analysis showed that a 6.5-cm increase in height resulted in lower levels of body mass index (P < 0.001), triglycerides (P < 0.001), non high-density (non-HDL) cholesterol (P < 0.001), C-reactive protein (P = 0.042), and systolic blood pressure (P = 0.064) and higher levels of forced expiratory volume in 1 s and forced vital capacity (P < 0.001 for both). CONCLUSIONS: Taller individuals have a lower risk of CHD with potential explanations being that taller people have a better lung function and lower levels of body mass index, cholesterol and blood pressure.

Nelson CP, Hamby SE, Saleheen D, Hopewell JC, Zeng L, Assimes TL, Kanoni S, Willenborg C, Burgess S, Amouyel P et al. 2015. Genetically determined height and coronary artery disease. N Engl J Med, 372 (17), pp. 1608-1618. | Show Abstract | Read more

BACKGROUND: The nature and underlying mechanisms of an inverse association between adult height and the risk of coronary artery disease (CAD) are unclear. METHODS: We used a genetic approach to investigate the association between height and CAD, using 180 height-associated genetic variants. We tested the association between a change in genetically determined height of 1 SD (6.5 cm) with the risk of CAD in 65,066 cases and 128,383 controls. Using individual-level genotype data from 18,249 persons, we also examined the risk of CAD associated with the presence of various numbers of height-associated alleles. To identify putative mechanisms, we analyzed whether genetically determined height was associated with known cardiovascular risk factors and performed a pathway analysis of the height-associated genes. RESULTS: We observed a relative increase of 13.5% (95% confidence interval [CI], 5.4 to 22.1; P<0.001) in the risk of CAD per 1-SD decrease in genetically determined height. There was a graded relationship between the presence of an increased number of height-raising variants and a reduced risk of CAD (odds ratio for height quartile 4 versus quartile 1, 0.74; 95% CI, 0.68 to 0.84; P<0.001). Of the 12 risk factors that we studied, we observed significant associations only with levels of low-density lipoprotein cholesterol and triglycerides (accounting for approximately 30% of the association). We identified several overlapping pathways involving genes associated with both development and atherosclerosis. CONCLUSIONS: There is a primary association between a genetically determined shorter height and an increased risk of CAD, a link that is partly explained by the association between shorter height and an adverse lipid profile. Shared biologic processes that determine achieved height and the development of atherosclerosis may explain some of the association. (Funded by the British Heart Foundation and others.).

Notari M, Hu Y, Sutendra G, Dedeić Z, Lu M, Dupays L, Yavari A, Carr CA, Zhong S, Opel A et al. 2015. iASPP, a previously unidentified regulator of desmosomes, prevents arrhythmogenic right ventricular cardiomyopathy (ARVC)-induced sudden death. Proc Natl Acad Sci U S A, 112 (9), pp. E973-E981. | Show Abstract | Read more

Desmosomes are anchoring junctions that exist in cells that endure physical stress such as cardiac myocytes. The importance of desmosomes in maintaining the homeostasis of the myocardium is underscored by frequent mutations of desmosome components found in human patients and animal models. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a phenotype caused by mutations in desmosomal components in ∼ 50% of patients, however, the causes in the remaining 50% of patients still remain unknown. A deficiency of inhibitor of apoptosis-stimulating protein of p53 (iASPP), an evolutionarily conserved inhibitor of p53, caused by spontaneous mutation recently has been associated with a lethal autosomal recessive cardiomyopathy in Poll Hereford calves and Wa3 mice. However, the molecular mechanisms that mediate this putative function of iASPP are completely unknown. Here, we show that iASPP is expressed at intercalated discs in human and mouse postmitotic cardiomyocytes. iASPP interacts with desmoplakin and desmin in cardiomyocytes to maintain the integrity of desmosomes and intermediate filament networks in vitro and in vivo. iASPP deficiency specifically induces right ventricular dilatation in mouse embryos at embryonic day 16.5. iASPP-deficient mice with exon 8 deletion (Ppp1r13l(Δ8/Δ8)) die of sudden cardiac death, displaying features of ARVC. Intercalated discs in cardiomyocytes from four of six human ARVC cases show reduced or loss of iASPP. ARVC-derived desmoplakin mutants DSP-1-V30M and DSP-1-S299R exhibit weaker binding to iASPP. These data demonstrate that by interacting with desmoplakin and desmin, iASPP is an important regulator of desmosomal function both in vitro and in vivo. This newly identified property of iASPP may provide new molecular insight into the pathogenesis of ARVC.

Shungin D, Winkler TW, Croteau-Chonka DC, Ferreira T, Locke AE, Mägi R, Strawbridge RJ, Pers TH, Fischer K, Justice AE et al. 2015. New genetic loci link adipose and insulin biology to body fat distribution. Nature, 518 (7538), pp. 187-196. | Show Abstract | Read more

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms.

Locke AE, Kahali B, Berndt SI, Justice AE, Pers TH, Day FR, Powell C, Vedantam S, Buchkovich ML, Yang J et al. 2015. Genetic studies of body mass index yield new insights for obesity biology. Nature, 518 (7538), pp. 197-206. | Show Abstract | Read more

Obesity is heritable and predisposes to many diseases. To understand the genetic basis of obesity better, here we conduct a genome-wide association study and Metabochip meta-analysis of body mass index (BMI), a measure commonly used to define obesity and assess adiposity, in up to 339,224 individuals. This analysis identifies 97 BMI-associated loci (P < 5 × 10(-8)), 56 of which are novel. Five loci demonstrate clear evidence of several independent association signals, and many loci have significant effects on other metabolic phenotypes. The 97 loci account for ∼2.7% of BMI variation, and genome-wide estimates suggest that common variation accounts for >20% of BMI variation. Pathway analyses provide strong support for a role of the central nervous system in obesity susceptibility and implicate new genes and pathways, including those related to synaptic function, glutamate signalling, insulin secretion/action, energy metabolism, lipid biology and adipogenesis.

Nethononda RM, Lewandowski AJ, Stewart R, Kylinterias I, Whitworth P, Francis J, Leeson P, Watkins H, Neubauer S, Rider OJ. 2015. Gender specific patterns of age-related decline in aortic stiffness: a cardiovascular magnetic resonance study including normal ranges. J Cardiovasc Magn Reson, 17 (1), pp. 20. | Show Abstract | Read more

BACKGROUND: Young females exhibit lower cardiovascular event rates that young men, a pattern which is lost, or even reversed with advancing age. As aortic stiffness is a powerful risk factor for cardiovascular events, a gender difference with advancing age could provide a plausible explanation for this pattern. METHODS: 777 subjects (♀n = 408, ♂n = 369) across a wide range of age (21-85 years) underwent cardiovascular magnetic resonance to assess aortic pulse wave velocity (PWV) and, in addition, aortic distensibility at three levels; 1) ascending aorta (Ao) and 2) proximal descending aorta (PDA) at the level of the pulmonary artery and 3) the abdominal aorta (DDA). RESULTS: There was a strong negative correlation between increasing age and regional aortic distensibility (Ao♀R-0.84, ♂R-0.80, PDA♀R-0.82, ♂R-0.77, DDA♀R-0.80, ♂R-0.71 all p < 0.001) and a strong positive correlation with PWV, (♀R0.53, ♂R 0.63 both p < 0.001). Even after adjustment for mean arterial pressure, body mass index, heart rate, smoking and diabetes, females exhibited a steeper decrease in all distensibility measures in response to increasing age (Ao♀-1.3 vs ♂-1.1 mmHg-1, PDA ♀-1.2 vs ♂-1.0 mmHg, DDA ♀-1.8 vs ♂-1.4 mmHg-1 per 10 years increase in age all p < 0.001). No gender difference in PWV increase with age was observed (p = 0.11). CONCLUSION: Although advancing age is accompanied by increased aortic stiffness in both males and females, a significant sex difference in the rate of change exists, with females showing a steeper decline in aortic elasticity. As aortic stiffness is strongly related to cardiovascular events our observations may explain the increase in cardiovascular event rates that accompanies the menopausal age in women.

Kramer CM, Appelbaum E, Desai MY, Desvigne-Nickens P, DiMarco JP, Friedrich MG, Geller N, Heckler S, Ho CY, Jerosch-Herold M et al. 2015. Hypertrophic Cardiomyopathy Registry: The rationale and design of an international, observational study of hypertrophic cardiomyopathy. Am Heart J, 170 (2), pp. 223-230. | Show Abstract | Read more

Hypertrophic cardiomyopathy (HCM) is the most common monogenic heart disease with a frequency as high as 1 in 200. In many cases, HCM is caused by mutations in genes encoding the different components of the sarcomere apparatus. Hypertrophic cardiomyopathy is characterized by unexplained left ventricular hypertrophy, myofibrillar disarray, and myocardial fibrosis. The phenotypic expression is quite variable. Although most patients with HCM are asymptomatic, serious consequences are experienced in a subset of affected individuals who present initially with sudden cardiac death or progress to refractory heart failure. The Hypertrophic Cardiomyopathy Registry study is a National Heart, Lung, and Blood Institute-sponsored 2,750-patient, 44-site, international registry and natural history study designed to address limitations in extant evidence to improve prognostication in HCM (NCT01915615). In addition to the collection of standard demographic, clinical, and echocardiographic variables, patients will undergo state-of-the-art cardiac magnetic resonance for assessment of left ventricular mass and volumes as well as replacement scarring and interstitial fibrosis. In addition, genetic and biomarker analyses will be performed. The Hypertrophic Cardiomyopathy Registry has the potential to change the paradigm of risk stratification in HCM, using novel markers to identify those at higher risk.

Watkins H. 2015. Tackling the achilles' heel of genetic testing. Sci Transl Med, 7 (270), pp. 270fs1. | Show Abstract | Read more

Assigning pathogenicity to rare genetic variants is at its hardest with the enormous titin gene, but comprehensive genomic analysis makes the task more tractable (Roberts et al., this issue).

Kramer CM, Appelbaum E, Desai MY, Desvigne-Nickens P, DiMarco JP, Friedrich MG, Geller N, Heckler S, Ho CY, Jerosch-Herold M et al. 2015. Hypertrophic Cardiomyopathy Registry: The rationale and design of an international, observational study of hypertrophic cardiomyopathy American Heart Journal, 170 (2), pp. 223-230. | Show Abstract | Read more

© 2015 Elsevier Inc. All rights reserved.Hypertrophic cardiomyopathy (HCM) is the most common monogenic heart disease with a frequency as high as 1 in 200. In many cases, HCM is caused by mutations in genes encoding the different components of the sarcomere apparatus. Hypertrophic cardiomyopathy is characterized by unexplained left ventricular hypertrophy, myofibrillar disarray, and myocardial fibrosis. The phenotypic expression is quite variable. Although most patients with HCM are asymptomatic, serious consequences are experienced in a subset of affected individuals who present initially with sudden cardiac death or progress to refractory heart failure. The Hypertrophic Cardiomyopathy Registry study is a National Heart, Lung, and Blood Institute-sponsored 2,750-patient, 44-site, international registry and natural history study designed to address limitations in extant evidence to improve prognostication in HCM (NCT01915615). In addition to the collection of standard demographic, clinical, and echocardiographic variables, patients will undergo state-of-the-art cardiac magnetic resonance for assessment of left ventricular mass and volumes as well as replacement scarring and interstitial fibrosis. In addition, genetic and biomarker analyses will be performed. The Hypertrophic Cardiomyopathy Registry has the potential to change the paradigm of risk stratification in HCM, using novel markers to identify those at higher risk.

Pitcher A, Emberson J, Lacro RV, Sleeper LA, Stylianou M, Mahony L, Pearson GD, Groenink M, Mulder BJ, Zwinderman AH et al. 2015. Design and rationale of a prospective, collaborative meta-analysis of all randomized controlled trials of angiotensin receptor antagonists in Marfan syndrome, based on individual patient data: A report from the Marfan Treatment Trialists' Collaboration American Heart Journal, 169 (5), pp. 605-612. | Show Abstract | Read more

© 2015 The Authors.Rationale A number of randomized trials are underway, which will address the effects of angiotensin receptor blockers (ARBs) on aortic root enlargement and a range of other end points in patients with Marfan syndrome. If individual participant data from these trials were to be combined, a meta-analysis of the resulting data, totaling approximately 2,300 patients, would allow estimation across a number of trials of the treatment effects both of ARB therapy and of β-blockade. Such an analysis would also allow estimation of treatment effects in particular subgroups of patients on a range of end points of interest and would allow a more powerful estimate of the effects of these treatments on a composite end point of several clinical outcomes than would be available from any individual trial. Design A prospective, collaborative meta-analysis based on individual patient data from all randomized trials in Marfan syndrome of (i) ARBs versus placebo (or open-label control) and (ii) ARBs versus β-blockers will be performed. A prospective study design, in which the principal hypotheses, trial eligibility criteria, analyses, and methods are specified in advance of the unblinding of the component trials, will help to limit bias owing to data-dependent emphasis on the results of particular trials. The use of individual patient data will allow for analysis of the effects of ARBs in particular patient subgroups and for time-to-event analysis for clinical outcomes. The meta-analysis protocol summarized in this report was written on behalf of the Marfan Treatment Trialists' Collaboration and finalized in late 2012, without foreknowledge of the results of any component trial, and will be made available online (http://www.ctsu.ox.ac.uk/research/meta-trials).

Huffman JE, Albrecht E, Teumer A, Mangino M, Kapur K, Johnson T, Kutalik Z, Pirastu N, Pistis G, Lopez LM et al. 2015. Modulation of genetic associations with serum urate levels by body-mass-index in humans. PLoS One, 10 (3), pp. e0119752. | Show Abstract | Read more

We tested for interactions between body mass index (BMI) and common genetic variants affecting serum urate levels, genome-wide, in up to 42569 participants. Both stratified genome-wide association (GWAS) analyses, in lean, overweight and obese individuals, and regression-type analyses in a non BMI-stratified overall sample were performed. The former did not uncover any novel locus with a major main effect, but supported modulation of effects for some known and potentially new urate loci. The latter highlighted a SNP at RBFOX3 reaching genome-wide significant level (effect size 0.014, 95% CI 0.008-0.02, Pinter= 2.6 x 10-8). Two top loci in interaction term analyses, RBFOX3 and ERO1LB-EDARADD, also displayed suggestive differences in main effect size between the lean and obese strata. All top ranking loci for urate effect differences between BMI categories were novel and most had small magnitude but opposite direction effects between strata. They include the locus RBMS1-TANK (men, Pdifflean-overweight= 4.7 x 10-8), a region that has been associated with several obesity related traits, and TSPYL5 (men, Pdifflean-overweight= 9.1 x 10-8), regulating adipocytes-produced estradiol. The top-ranking known urate loci was ABCG2, the strongest known gout risk locus, with an effect halved in obese compared to lean men (Pdifflean-obese= 2 x 10-4). Finally, pathway analysis suggested a role for N-glycan biosynthesis as a prominent urate-associated pathway in the lean stratum. These results illustrate a potentially powerful way to monitor changes occurring in obesogenic environment.

Freitag DF, Butterworth AS, Willeit P, Howson JMM, Burgess S, Kaptoge S, Young R, Ho WK, Wood AM, Sweeting M et al. 2015. Cardiometabolic effects of genetic upregulation of the interleukin 1 receptor antagonist: a Mendelian randomisation analysis LANCET DIABETES & ENDOCRINOLOGY, 3 (4), pp. 243-253. | Show Abstract | Read more

© 2015 The Interleukin 1 Genetics Consortium.To investigate potential cardiovascular and other effects of long-term pharmacological interleukin 1 (IL-1) inhibition, we studied genetic variants that produce inhibition of IL-1, a master regulator of inflammation. Methods: We created a genetic score combining the effects of alleles of two common variants (rs6743376 and rs1542176) that are located upstream of IL1RN, the gene encoding the IL-1 receptor antagonist (IL-1Ra; an endogenous inhibitor of both IL-1α and IL-1β); both alleles increase soluble IL-1Ra protein concentration. We compared effects on inflammation biomarkers of this genetic score with those of anakinra, the recombinant form of IL-1Ra, which has previously been studied in randomised trials of rheumatoid arthritis and other inflammatory disorders. In primary analyses, we investigated the score in relation to rheumatoid arthritis and four cardiometabolic diseases (type 2 diabetes, coronary heart disease, ischaemic stroke, and abdominal aortic aneurysm; 453 411 total participants). In exploratory analyses, we studied the relation of the score to many disease traits and to 24 other disorders of proposed relevance to IL-1 signalling (746 171 total participants). Findings: For each IL1RN minor allele inherited, serum concentrations of IL-1Ra increased by 0·22 SD (95% CI 0·18-0·25; 12·5%; p=9·3 × 10-33), concentrations of interleukin 6 decreased by 0·02 SD (-0·04 to -0·01; -1·7%; p=3·5 × 10-3), and concentrations of C-reactive protein decreased by 0·03 SD (-0·04 to -0·02; -3·4%; p=7·7 × 10-14). We noted the effects of the genetic score on these inflammation biomarkers to be directionally concordant with those of anakinra. The allele count of the genetic score had roughly log-linear, dose-dependent associations with both IL-1Ra concentration and risk of coronary heart disease. For people who carried four IL-1Ra-raising alleles, the odds ratio for coronary heart disease was 1·15 (1·08-1·22; p=1·8 × 10-6) compared with people who carried no IL-1Ra-raising alleles; the per-allele odds ratio for coronary heart disease was 1·03 (1·02-1·04; p=3·9 × 10-10). Per-allele odds ratios were 0·97 (0·95-0·99; p=9·9 × 10-4) for rheumatoid arthritis, 0·99 (0·97-1·01; p=0·47) for type 2 diabetes, 1·00 (0·98-1·02; p=0·92) for ischaemic stroke, and 1·08 (1·04-1·12; p=1·8 × 10-5) for abdominal aortic aneurysm. In exploratory analyses, we observed per-allele increases in concentrations of proatherogenic lipids, including LDL-cholesterol, but no clear evidence of association for blood pressure, glycaemic traits, or any of the 24 other disorders studied. Modelling suggested that the observed increase in LDL-cholesterol could account for about a third of the association observed between the genetic score and increased coronary risk. Interpretation: Human genetic data suggest that long-term dual IL-1α/β inhibition could increase cardiovascular risk and, conversely, reduce the risk of development of rheumatoid arthritis. The cardiovascular risk might, in part, be mediated through an increase in proatherogenic lipid concentrations. Funding: UK Medical Research Council, British Heart Foundation, UK National Institute for Health Research, National Institute for Health Research Cambridge Biomedical Research Centre, European Research Council, and European Commission Framework Programme 7.

Gigante B, Strawbridge RJ, Velasquez IM, Golabkesh Z, Silveira A, Goel A, Baldassarre D, Veglia F, Tremoli E, Clarke R et al. 2015. Analysis of the role of interleukin 6 receptor haplotypes in the regulation of circulating levels of inflammatory biomarkers and risk of coronary heart disease. PLoS One, 10 (3), pp. e0119980. | Show Abstract | Read more

Variants at the interleukin 6 receptor (IL6R) gene regulate inflammation and are associated with risk of coronary heart disease (CHD). The aim of the present study was to investigate the effects of IL6R haplotypes on circulating levels of inflammatory biomarkers and risk of CHD. We performed a discovery analysis in SHEEP, a myocardial infarction (MI) case control study (n = 2,774) and replicated our results in two large, independent European populations, PROCARDIS, a CHD case control study (n = 7,998), and IMPROVE (n = 3,711) a prospective cardiovascular cohort study. Two major haplotype blocks (rs12083537A/G and rs4075015A/T--block 1; and rs8192282G/A, rs4553185T/C, rs8192284A/C, rs4240872T/C and rs7514452T/C--block 2) were identified in the IL6R gene. IL6R haplotype associations with C-reactive protein (CRP), fibrinogen, IL6, soluble IL6R (sIL6R), IL6, IL8 and TNF-α in SHEEP, CRP and fibrinogen in PROCARDIS and CRP in IMPROVE as well as association with risk of MI and CHD, were analyzed by THESIAS. Haplotypes in block 1 were associated neither with circulating inflammatory biomarkers nor with the MI/CHD risk. Haplotypes in block 2 were associated with circulating levels of CRP, in all three study populations, with fibrinogen in SHEEP and PROCARDIS, with IL8 and sIL6Rin SHEEP and with a modest, non significant, increase (7%) in MI/CHD risk in the three populations studied. Our results indicate that IL6R haplotypes regulate the circulating levels of inflammatory biomarkers. Lack of association with the risk of CHD may be explained by the combined effect of SNPs with opposite effect on the CHD risk, the sample size as well as by structural changes affecting sIL6R stability in the circulation.

Wessel J, Chu AY, Willems SM, Wang S, Yaghootkar H, Brody JA, Dauriz M, Hivert MF, Raghavan S, Lipovich L et al. 2015. Low-frequency and rare exome chip variants associate with fasting glucose and type 2 diabetes susceptibility. Nat Commun, 6 pp. 5897. | Show Abstract | Read more

Fasting glucose and insulin are intermediate traits for type 2 diabetes. Here we explore the role of coding variation on these traits by analysis of variants on the HumanExome BeadChip in 60,564 non-diabetic individuals and in 16,491 T2D cases and 81,877 controls. We identify a novel association of a low-frequency nonsynonymous SNV in GLP1R (A316T; rs10305492; MAF=1.4%) with lower FG (β=-0.09±0.01 mmol l(-1), P=3.4 × 10(-12)), T2D risk (OR[95%CI]=0.86[0.76-0.96], P=0.010), early insulin secretion (β=-0.07±0.035 pmolinsulin mmolglucose(-1), P=0.048), but higher 2-h glucose (β=0.16±0.05 mmol l(-1), P=4.3 × 10(-4)). We identify a gene-based association with FG at G6PC2 (pSKAT=6.8 × 10(-6)) driven by four rare protein-coding SNVs (H177Y, Y207S, R283X and S324P). We identify rs651007 (MAF=20%) in the first intron of ABO at the putative promoter of an antisense lncRNA, associating with higher FG (β=0.02±0.004 mmol l(-1), P=1.3 × 10(-8)). Our approach identifies novel coding variant associations and extends the allelic spectrum of variation underlying diabetes-related quantitative traits and T2D susceptibility.

Do R, Stitziel NO, Won HH, Jørgensen AB, Duga S, Angelica Merlini P, Kiezun A, Farrall M, Goel A, Zuk O et al. 2015. Exome sequencing identifies rare LDLR and APOA5 alleles conferring risk for myocardial infarction. Nature, 518 (7537), pp. 102-106. | Show Abstract | Read more

Myocardial infarction (MI), a leading cause of death around the world, displays a complex pattern of inheritance. When MI occurs early in life, genetic inheritance is a major component to risk. Previously, rare mutations in low-density lipoprotein (LDL) genes have been shown to contribute to MI risk in individual families, whereas common variants at more than 45 loci have been associated with MI risk in the population. Here we evaluate how rare mutations contribute to early-onset MI risk in the population. We sequenced the protein-coding regions of 9,793 genomes from patients with MI at an early age (≤50 years in males and ≤60 years in females) along with MI-free controls. We identified two genes in which rare coding-sequence mutations were more frequent in MI cases versus controls at exome-wide significance. At low-density lipoprotein receptor (LDLR), carriers of rare non-synonymous mutations were at 4.2-fold increased risk for MI; carriers of null alleles at LDLR were at even higher risk (13-fold difference). Approximately 2% of early MI cases harbour a rare, damaging mutation in LDLR; this estimate is similar to one made more than 40 years ago using an analysis of total cholesterol. Among controls, about 1 in 217 carried an LDLR coding-sequence mutation and had plasma LDL cholesterol > 190 mg dl(-1). At apolipoprotein A-V (APOA5), carriers of rare non-synonymous mutations were at 2.2-fold increased risk for MI. When compared with non-carriers, LDLR mutation carriers had higher plasma LDL cholesterol, whereas APOA5 mutation carriers had higher plasma triglycerides. Recent evidence has connected MI risk with coding-sequence mutations at two genes functionally related to APOA5, namely lipoprotein lipase and apolipoprotein C-III (refs 18, 19). Combined, these observations suggest that, as well as LDL cholesterol, disordered metabolism of triglyceride-rich lipoproteins contributes to MI risk.

Myocardial Infarction Genetics Consortium Investigators. 2014. Inactivating mutations in NPC1L1 and protection from coronary heart disease. N Engl J Med, 371 (22), pp. 2072-2082. | Show Abstract | Read more

BACKGROUND: Ezetimibe lowers plasma levels of low-density lipoprotein (LDL) cholesterol by inhibiting the activity of the Niemann-Pick C1-like 1 (NPC1L1) protein. However, whether such inhibition reduces the risk of coronary heart disease is not known. Human mutations that inactivate a gene encoding a drug target can mimic the action of an inhibitory drug and thus can be used to infer potential effects of that drug. METHODS: We sequenced the exons of NPC1L1 in 7364 patients with coronary heart disease and in 14,728 controls without such disease who were of European, African, or South Asian ancestry. We identified carriers of inactivating mutations (nonsense, splice-site, or frameshift mutations). In addition, we genotyped a specific inactivating mutation (p.Arg406X) in 22,590 patients with coronary heart disease and in 68,412 controls. We tested the association between the presence of an inactivating mutation and both plasma lipid levels and the risk of coronary heart disease. RESULTS: With sequencing, we identified 15 distinct NPC1L1 inactivating mutations; approximately 1 in every 650 persons was a heterozygous carrier for 1 of these mutations. Heterozygous carriers of NPC1L1 inactivating mutations had a mean LDL cholesterol level that was 12 mg per deciliter (0.31 mmol per liter) lower than that in noncarriers (P=0.04). Carrier status was associated with a relative reduction of 53% in the risk of coronary heart disease (odds ratio for carriers, 0.47; 95% confidence interval, 0.25 to 0.87; P=0.008). In total, only 11 of 29,954 patients with coronary heart disease had an inactivating mutation (carrier frequency, 0.04%) in contrast to 71 of 83,140 controls (carrier frequency, 0.09%). CONCLUSIONS: Naturally occurring mutations that disrupt NPC1L1 function were found to be associated with reduced plasma LDL cholesterol levels and a reduced risk of coronary heart disease. (Funded by the National Institutes of Health and others.).

Wood AR, Esko T, Yang J, Vedantam S, Pers TH, Gustafsson S, Chu AY, Estrada K, Luan J, Kutalik Z et al. 2014. Defining the role of common variation in the genomic and biological architecture of adult human height. Nat Genet, 46 (11), pp. 1173-1186. | Show Abstract | Read more

Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated ∼2,000, ∼3,700 and ∼9,500 SNPs explained ∼21%, ∼24% and ∼29% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/β-catenin and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.

Schick UM, Auer PL, Bis JC, Lin H, Wei P, Pankratz N, Lange LA, Brody J, Stitziel NO, Kim DS et al. 2015. Association of exome sequences with plasma C-reactive protein levels in >9000 participants. Hum Mol Genet, 24 (2), pp. 559-571. | Show Abstract | Read more

C-reactive protein (CRP) concentration is a heritable systemic marker of inflammation that is associated with cardiovascular disease risk. Genome-wide association studies have identified CRP-associated common variants associated in ∼25 genes. Our aims were to apply exome sequencing to (1) assess whether the candidate loci contain rare coding variants associated with CRP levels and (2) perform an exome-wide search for rare variants in novel genes associated with CRP levels. We exome-sequenced 6050 European-Americans (EAs) and 3109 African-Americans (AAs) from the NHLBI-ESP and the CHARGE consortia, and performed association tests of sequence data with measured CRP levels. In single-variant tests across candidate loci, a novel rare (minor allele frequency = 0.16%) CRP-coding variant (rs77832441-A; p.Thr59Met) was associated with 53% lower mean CRP levels (P = 2.9 × 10(-6)). We replicated the association of rs77832441 in an exome array analysis of 11 414 EAs (P = 3.0 × 10(-15)). Despite a strong effect on CRP levels, rs77832441 was not associated with inflammation-related phenotypes including coronary heart disease. We also found evidence for an AA-specific association of APOE-ε2 rs7214 with higher CRP levels. At the exome-wide significance level (P < 5.0 × 10(-8)), we confirmed associations for reported common variants of HNF1A, CRP, IL6R and TOMM40-APOE. In gene-based tests, a burden of rare/lower frequency variation in CRP in EAs (P ≤ 6.8 × 10(-4)) and in retinoic acid receptor-related orphan receptor α (RORA) in AAs (P = 1.7 × 10(-3)) were associated with CRP levels at the candidate gene level (P < 2.0 × 10(-3)). This inquiry did not elucidate novel genes, but instead demonstrated that variants distributed across the allele frequency spectrum within candidate genes contribute to CRP levels.

Pitcher A, Emberson J, Lacro RV, Sleeper LA, Stylianou M, Mahony L, Pearson GD, Groenink M, Mulder BJ, Zwinderman AH et al. 2015. Design and rationale of a prospective, collaborative meta-analysis of all randomized controlled trials of angiotensin receptor antagonists in Marfan syndrome, based on individual patient data: A report from the Marfan Treatment Trialists' Collaboration. Am Heart J, 169 (5), pp. 605-612. | Show Abstract | Read more

RATIONALE: A number of randomized trials are underway, which will address the effects of angiotensin receptor blockers (ARBs) on aortic root enlargement and a range of other end points in patients with Marfan syndrome. If individual participant data from these trials were to be combined, a meta-analysis of the resulting data, totaling approximately 2,300 patients, would allow estimation across a number of trials of the treatment effects both of ARB therapy and of β-blockade. Such an analysis would also allow estimation of treatment effects in particular subgroups of patients on a range of end points of interest and would allow a more powerful estimate of the effects of these treatments on a composite end point of several clinical outcomes than would be available from any individual trial. DESIGN: A prospective, collaborative meta-analysis based on individual patient data from all randomized trials in Marfan syndrome of (i) ARBs versus placebo (or open-label control) and (ii) ARBs versus β-blockers will be performed. A prospective study design, in which the principal hypotheses, trial eligibility criteria, analyses, and methods are specified in advance of the unblinding of the component trials, will help to limit bias owing to data-dependent emphasis on the results of particular trials. The use of individual patient data will allow for analysis of the effects of ARBs in particular patient subgroups and for time-to-event analysis for clinical outcomes. The meta-analysis protocol summarized in this report was written on behalf of the Marfan Treatment Trialists' Collaboration and finalized in late 2012, without foreknowledge of the results of any component trial, and will be made available online (http://www.ctsu.ox.ac.uk/research/meta-trials).

Robinson P, Liu X, Zhang YH, Khandelwal A, Blagg B, Casadei B, Watkins H, Redwood C. 2014. P123The rescue of Ca2+ cycling abnormalities conferred by HCM-causing mutations with analogues of the green tea polyphenol epigallocatechin-3-gallate. Cardiovasc Res, 103 Suppl 1 (suppl 1), pp. S21. | Show Abstract | Read more

Mutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) confer distinct primary alterations of cardiac contractility. We have shown that altered Ca2+-buffering by mutant thin filaments leads to altered Ca2+ handling and results in stimulation of Ca2+-dependent signalling pathways. To do this we have used adenoviral mediated expression of cTnT R92Q, cTnI R145G and α-TM D175N in adult guinea pig cardiomyocytes at a ratio of 1:1 with the endogenous protein. Simultaneous measurement of unloaded sarcomere-shortening and Ca2+ transients using fura-2 loading, showed the HCM mutations caused a significant decrease in the basal sarcomere length coupled with an increase in the diastolic Ca2+ concentration. The mechanism of alterations to EC-coupling was also investigated using tetracaine and caffeine challenging combined with simultaneous whole cell patch clamping. HCM mutant cells displayed reduced SR load (~1.4fold), slowed NCX calcium extrusion (~2.5fold), unchanged SERCA2 activity, increased ryanodine receptor leak (~5fold) and increased calcium buffering (~3fold). This was coupled to an increase in Ca2+ dependent NFAT nuclear localisation. Further studies using the green tea catechin, epigallocatechin gallate (EGCg) and sister compound epicatechin-3-gallate (ECG), have shown that the compounds can partiality reverse the increase in diastolic Ca2+ observed in cardiomyocytes containing HCM causing mutations. The mechanism is thought to be via an interaction with cTnC (measured using intrinsic cTnC tyrosine fluorescence) which in turn causes a reduction of in vitro thin filament Ca2+ affinity (measured using cTnC labelled with IAANS fluorophore at Cys 35). Data acquired so far suggests that catechins and their derivative compounds may provide a possible therapeutic approach for correcting Ca2+ regulation and Ca2+ dependent remodelling in HCM. We have recently obtained library of 37 EGCg analogues which we have screened for cTnC affinity and thin filament Ca2+ affinity. We have now identified several catechins with potentially greater efficacy than the parent compound, and plan to test their ability to rescue the cellular HCM phenotype characterised above.

Turtle C, Robinson P, Yavari A, Ghaffari S, Pinter K, Watkins H, Redwood C. 2014. P387Knock-in mouse model of PRKAG2 cardiomyopathy (R299Q) exhibits altered Ca2+-dependent cardiac contractility and reduced protein kinase A activity. Cardiovasc Res, 103 Suppl 1 (suppl 1), pp. S71. | Show Abstract | Read more

Familial hypertrophic cardiomyopathy (HCM) is most commonly caused by mutations in sarcomeric proteins; however, a unifying mechanism of disease pathogenesis has yet to be identified. Beyond the sarcomere, mutations in the gene (PRKAG2) encoding the γ2 subunit of AMP-activated protein kinase (AMPK), an enzyme involved in energy balance regulation and cell signalling, cause ventricular hypertrophy and contractile dysfunction mimicking HCM. These AMPK γ2 mutations also result in glycogen accumulation and aberrant electrical conduction, obfuscating the cause of hypertrophy and dysfunction. Given our recent finding that cardiac troponin I (cTnI) is phosphorylated by AMPK at S150 and this phosphorylation enhances Ca2+ sensitivity of activation, we hypothesise that alterations at the myofilament level may contribute to disease pathogenesis in PRKAG2 cardiomyopathy as they do in HCM. To test this, we have used a mouse model possessing an AMPK γ2 mutation (R299Q knock-in) and measured demembranated trabeculae mechanics and cardiomyocyte contractility using heterozygous and homozygous male mice, along with littermate wild type controls, between 6-8 weeks of age (prior to hypertrophy and significant glycogen accumulation). In trabeculae, we observed increased Ca2+ sensitivity of force production in fibres from mutant mice (ΔpCa50 = +0.05 (Het) and +0.06 (Homo), p < 0.01). After treating fibres with protein kinase A (PKA), no differences in Ca2+ sensitivity of force production were observed between WT and mutant groups. Intact cardiomyocytes isolated from mutant hearts exhibited little difference in shortening or Ca2+ transient magnitudes but significantly slowed kinetics of both contraction and relaxation. Cardiomyocytes from mutant mice exhibited a greater response to isoproterenol. Biochemical analyses of untreated tissues indicated reduced phosphorylation of cTnI S23/S24 (Δmol P/mol TnI = -0.17 (Het) and -0.28 (Homo), p < 0.05) and phospholamban S16, indicating reduced basal PKA activity in mutant animals. This work provides evidence that the R299Q PRKAG2 mutation causes altered cardiac contractile function irrespective of glycogen accumulation and therefore supports the hypothesis that impaired contractility contributes to disease pathogenesis. Further, the observed Ca2+ sensitization and reduction in phosphorylation of PKA target sites mimics similar alterations found in HCM caused by sarcomeric mutations. The reduction in PKA activity in the mutant hearts may be caused by novel crosstalk between the AMPK and PKA pathways, in particular as this occurs prior to hypertrophy.

Söderström LÅ, Gertow K, Folkersen L, Sabater-Lleal M, Sundman E, Sheikine Y, Goel A, Baldassarre D, Humphries SE, de Faire U et al. 2014. Human genetic evidence for involvement of CD137 in atherosclerosis. Mol Med, 20 (JULY-DECEMBER 2014), pp. 456-465. | Show Abstract | Read more

Atherosclerosis is an inflammatory disease and the main cause of cardiovascular disease. Inflammation promotes plaque instability and clinical disease, such as myocardial infarction, stroke and peripheral vascular disease. Subclinical atherosclerosis begins with thickening of the arterial intimal layer, and increased intima-media thickness (IMT) in the carotid artery is a widely used measurement of subclinical atherosclerosis. Activation of CD137 (tumor necrosis factor receptor super family 9) promotes inflammation and disease development in murine atherosclerosis. CD137 is expressed in human atherosclerosis, but its role is largely unknown. This study uses a genetic approach to investigate CD137 in human atherosclerotic disease. In publicly available data on genotype and gene expression from the HapMap project, the minor T allele of rs2453021, a single nucleotide polymorphism in CD137, was significantly associated with CD137 gene expression. In the PROCARDIS and Wellcome Trust Case Control Consortium (WTCCC) cohorts of 13,029 cases and controls, no significant association was detected between the minor T allele of rs2453021 and risk for coronary artery disease or myocardial infarction. However, in the IMPROVE multicenter study of 3,418 individuals, the minor T allele of rs2453021 was associated with increased IMT of the common carotid artery (CCA), as measured by ultrasonography, with presence of plaque in CCA and with increased incidence of adverse noncardiac vascular events. Taken together, this study shows that the minor T allele of rs2453021 is associated with increased IMT in the CCA and increased risk of incident noncardiac vascular events, thus providing the first human genetic evidence for involvement of CD137 in atherosclerosis.

TG and HDL Working Group of the Exome Sequencing Project, National Heart, Lung, and Blood Institute, Crosby J, Peloso GM, Auer PL, Crosslin DR, Stitziel NO, Lange LA, Lu Y, Tang ZZ, Zhang H et al. 2014. Loss-of-function mutations in APOC3, triglycerides, and coronary disease. N Engl J Med, 371 (1), pp. 22-31. | Show Abstract | Read more

BACKGROUND: Plasma triglyceride levels are heritable and are correlated with the risk of coronary heart disease. Sequencing of the protein-coding regions of the human genome (the exome) has the potential to identify rare mutations that have a large effect on phenotype. METHODS: We sequenced the protein-coding regions of 18,666 genes in each of 3734 participants of European or African ancestry in the Exome Sequencing Project. We conducted tests to determine whether rare mutations in coding sequence, individually or in aggregate within a gene, were associated with plasma triglyceride levels. For mutations associated with triglyceride levels, we subsequently evaluated their association with the risk of coronary heart disease in 110,970 persons. RESULTS: An aggregate of rare mutations in the gene encoding apolipoprotein C3 (APOC3) was associated with lower plasma triglyceride levels. Among the four mutations that drove this result, three were loss-of-function mutations: a nonsense mutation (R19X) and two splice-site mutations (IVS2+1G→A and IVS3+1G→T). The fourth was a missense mutation (A43T). Approximately 1 in 150 persons in the study was a heterozygous carrier of at least one of these four mutations. Triglyceride levels in the carriers were 39% lower than levels in noncarriers (P<1×10(-20)), and circulating levels of APOC3 in carriers were 46% lower than levels in noncarriers (P=8×10(-10)). The risk of coronary heart disease among 498 carriers of any rare APOC3 mutation was 40% lower than the risk among 110,472 noncarriers (odds ratio, 0.60; 95% confidence interval, 0.47 to 0.75; P=4×10(-6)). CONCLUSIONS: Rare mutations that disrupt APOC3 function were associated with lower levels of plasma triglycerides and APOC3. Carriers of these mutations were found to have a reduced risk of coronary heart disease. (Funded by the National Heart, Lung, and Blood Institute and others.).

Simino J, Shi G, Bis JC, Chasman DI, Ehret GB, Gu X, Guo X, Hwang SJ, Sijbrands E, Smith AV et al. 2014. Gene-age interactions in blood pressure regulation: A large-scale investigation with the CHARGE, global BPgen, and ICBP consortia American Journal of Human Genetics, 95 (1), pp. 24-38. | Show Abstract | Read more

Although age-dependent effects on blood pressure (BP) have been reported, they have not been systematically investigated in large-scale genome-wide association studies (GWASs). We leveraged the infrastructure of three well-established consortia (CHARGE, GBPgen, and ICBP) and a nonstandard approach (age stratification and metaregression) to conduct a genome-wide search of common variants with age-dependent effects on systolic (SBP), diastolic (DBP), mean arterial (MAP), and pulse (PP) pressure. In a two-staged design using 99,241 individuals of European ancestry, we identified 20 genome-wide significant (p≤ 5 10) loci by using joint tests of the SNP main effect and SNP-age interaction. Nine of the significant loci demonstrated nominal evidence of age-dependent effects on BP by tests of the interactions alone. Index SNPs in the EHBP1L1 (DBP and MAP), CASZ1 (SBP and MAP), and GOSR2 (PP) loci exhibited the largest age interactions, with opposite directions of effect in the young versus the old. The changes in the genetic effects over time were small but nonnegligible (up to 1.58 mm Hg over 60 years). The EHBP1L1 locus was discovered through gene-age interactions only in whites but had DBP main effects replicated (p = 8.3 10) in 8,682 Asians from Singapore, indicating potential interethnic heterogeneity. A secondary analysis revealed 22 loci with evidence of age-specific effects (e.g., only in 20 to 29-year-olds). Age can be used to select samples with larger genetic effect sizes and more homogenous phenotypes, which may increase statistical power. Age-dependent effects identified through novel statistical approaches can provide insight into the biology and temporal regulation underlying BP associations. © 2014 The American Society of Human Genetics.

Lim ET, Würtz P, Havulinna AS, Palta P, Tukiainen T, Rehnström K, Esko T, Mägi R, Inouye M, Lappalainen T et al. 2014. Distribution and medical impact of loss-of-function variants in the Finnish founder population. PLoS Genet, 10 (7), pp. e1004494. | Show Abstract | Read more

Exome sequencing studies in complex diseases are challenged by the allelic heterogeneity, large number and modest effect sizes of associated variants on disease risk and the presence of large numbers of neutral variants, even in phenotypically relevant genes. Isolated populations with recent bottlenecks offer advantages for studying rare variants in complex diseases as they have deleterious variants that are present at higher frequencies as well as a substantial reduction in rare neutral variation. To explore the potential of the Finnish founder population for studying low-frequency (0.5-5%) variants in complex diseases, we compared exome sequence data on 3,000 Finns to the same number of non-Finnish Europeans and discovered that, despite having fewer variable sites overall, the average Finn has more low-frequency loss-of-function variants and complete gene knockouts. We then used several well-characterized Finnish population cohorts to study the phenotypic effects of 83 enriched loss-of-function variants across 60 phenotypes in 36,262 Finns. Using a deep set of quantitative traits collected on these cohorts, we show 5 associations (p<5×10⁻⁸) including splice variants in LPA that lowered plasma lipoprotein(a) levels (P = 1.5×10⁻¹¹⁷). Through accessing the national medical records of these participants, we evaluate the LPA finding via Mendelian randomization and confirm that these splice variants confer protection from cardiovascular disease (OR = 0.84, P = 3×10⁻⁴), demonstrating for the first time the correlation between very low levels of LPA in humans with potential therapeutic implications for cardiovascular diseases. More generally, this study articulates substantial advantages for studying the role of rare variation in complex phenotypes in founder populations like the Finns and by combining a unique population genetic history with data from large population cohorts and centralized research access to National Health Registers.

Simino J, Shi G, Bis JC, Chasman DI, Ehret GB, Gu X, Guo X, Hwang SJ, Sijbrands E, Smith AV et al. 2014. Gene-age interactions in blood pressure regulation: a large-scale investigation with the CHARGE, Global BPgen, and ICBP Consortia. Am J Hum Genet, 95 (1), pp. 24-38. | Show Abstract | Read more

Although age-dependent effects on blood pressure (BP) have been reported, they have not been systematically investigated in large-scale genome-wide association studies (GWASs). We leveraged the infrastructure of three well-established consortia (CHARGE, GBPgen, and ICBP) and a nonstandard approach (age stratification and metaregression) to conduct a genome-wide search of common variants with age-dependent effects on systolic (SBP), diastolic (DBP), mean arterial (MAP), and pulse (PP) pressure. In a two-staged design using 99,241 individuals of European ancestry, we identified 20 genome-wide significant (p ≤ 5 × 10(-8)) loci by using joint tests of the SNP main effect and SNP-age interaction. Nine of the significant loci demonstrated nominal evidence of age-dependent effects on BP by tests of the interactions alone. Index SNPs in the EHBP1L1 (DBP and MAP), CASZ1 (SBP and MAP), and GOSR2 (PP) loci exhibited the largest age interactions, with opposite directions of effect in the young versus the old. The changes in the genetic effects over time were small but nonnegligible (up to 1.58 mm Hg over 60 years). The EHBP1L1 locus was discovered through gene-age interactions only in whites but had DBP main effects replicated (p = 8.3 × 10(-4)) in 8,682 Asians from Singapore, indicating potential interethnic heterogeneity. A secondary analysis revealed 22 loci with evidence of age-specific effects (e.g., only in 20 to 29-year-olds). Age can be used to select samples with larger genetic effect sizes and more homogenous phenotypes, which may increase statistical power. Age-dependent effects identified through novel statistical approaches can provide insight into the biology and temporal regulation underlying BP associations.

Kyriakou T, Seedorf U, Goel A, Hopewell JC, Clarke R, Watkins H, Farrall M, PROCARDIS Consortium. 2014. A common LPA null allele associates with lower lipoprotein(a) levels and coronary artery disease risk. Arterioscler Thromb Vasc Biol, 34 (9), pp. 2095-2099. | Show Abstract | Read more

OBJECTIVE: Increased levels of lipoprotein(a) are a highly heritable risk factor for coronary artery disease (CAD). The genetic determinants of lipoprotein(a) levels are mainly because of genetic variation in the apolipoprotein(a) gene (LPA). We have tested the association of a relatively common null allele of LPA with lipoprotein(a) levels and CAD risk in a large case-control cohort. We have also examined how null allele genotyping complements apolipoprotein(a) isoform typing to refine the relationship between LPA isoform size and circulating lipoprotein(a) levels. APPROACH AND RESULTS: The LPA null allele (rs41272114) was genotyped in the PROCARDIS (Precocious Coronary Artery Disease) case-control cohort (4073 CAD cases and 4225 controls). Lipoprotein(a) levels were measured in 909 CAD cases and 922 controls; apolipoprotein(a) isoform size was estimated using sodium dodecyl sulfate-agarose gel electrophoresis and a high-throughput quantitative polymerase chain reaction-based method. Null carriers are common (null allele frequency, 3%) and have significantly lower circulating lipoprotein(a) levels (P=2.1×10(-10)) and reduced CAD risk (odds ratio, 0.79 [0.66-0.97]; P=0.023) compared with noncarriers. An additive allelic model of apolipoprotein(a) isoform size, refined by null allele genotype and quantitative polymerase chain reaction values, showed a sigmoid relationship with lipoprotein(a) levels, with baseline levels for longer isoform alleles and progressively higher levels of lipoprotein(a) for shorter isoform alleles. CONCLUSIONS: The LPA null allele (rs41272114) is associated with decreased circulating lipoprotein(a) levels and decreased CAD risk. Incorporating rs41272114 refined apolipoprotein(a) isoform size typing obtained by immunoblotting and quantitative polymerase chain reaction. A joint genomic and isoform analysis revealed details of the relationship between apolipoprotein(a) isoform size and circulating lipoprotein(a) level consistent with a threshold effect on lipoprotein secretion.

Al Turki S, Manickaraj AK, Mercer CL, Gerety SS, Hitz MP, Lindsay S, D'Alessandro LC, Swaminathan GJ, Bentham J, Arndt AK et al. 2014. Rare variants in NR2F2 cause congenital heart defects in humans. Am J Hum Genet, 94 (4), pp. 574-585. | Show Abstract | Read more

Congenital heart defects (CHDs) are the most common birth defect worldwide and are a leading cause of neonatal mortality. Nonsyndromic atrioventricular septal defects (AVSDs) are an important subtype of CHDs for which the genetic architecture is poorly understood. We performed exome sequencing in 13 parent-offspring trios and 112 unrelated individuals with nonsyndromic AVSDs and identified five rare missense variants (two of which arose de novo) in the highly conserved gene NR2F2, a very significant enrichment (p = 7.7 × 10(-7)) compared to 5,194 control subjects. We identified three additional CHD-affected families with other variants in NR2F2 including a de novo balanced chromosomal translocation, a de novo substitution disrupting a splice donor site, and a 3 bp duplication that cosegregated in a multiplex family. NR2F2 encodes a pleiotropic developmental transcription factor, and decreased dosage of NR2F2 in mice has been shown to result in abnormal development of atrioventricular septa. Via luciferase assays, we showed that all six coding sequence variants observed in individuals significantly alter the activity of NR2F2 on target promoters.

Peloso GM, Auer PL, Bis JC, Voorman A, Morrison AC, Stitziel NO, Brody JA, Khetarpal SA, Crosby JR, Fornage M et al. 2014. Association of low-frequency and rare coding-sequence variants with blood lipids and coronary heart disease in 56,000 whites and blacks. Am J Hum Genet, 94 (2), pp. 223-232. | Show Abstract | Read more

Low-frequency coding DNA sequence variants in the proprotein convertase subtilisin/kexin type 9 gene (PCSK9) lower plasma low-density lipoprotein cholesterol (LDL-C), protect against risk of coronary heart disease (CHD), and have prompted the development of a new class of therapeutics. It is uncertain whether the PCSK9 example represents a paradigm or an isolated exception. We used the "Exome Array" to genotype >200,000 low-frequency and rare coding sequence variants across the genome in 56,538 individuals (42,208 European ancestry [EA] and 14,330 African ancestry [AA]) and tested these variants for association with LDL-C, high-density lipoprotein cholesterol (HDL-C), and triglycerides. Although we did not identify new genes associated with LDL-C, we did identify four low-frequency (frequencies between 0.1% and 2%) variants (ANGPTL8 rs145464906 [c.361C>T; p.Gln121*], PAFAH1B2 rs186808413 [c.482C>T; p.Ser161Leu], COL18A1 rs114139997 [c.331G>A; p.Gly111Arg], and PCSK7 rs142953140 [c.1511G>A; p.Arg504His]) with large effects on HDL-C and/or triglycerides. None of these four variants was associated with risk for CHD, suggesting that examples of low-frequency coding variants with robust effects on both lipids and CHD will be limited.

Cited:

41

Scopus

Liu DJ, Peloso GM, Zhan X, Holmen OL, Zawistowski M, Feng S, Nikpay M, Auer PL, Goel A, Zhang H et al. 2014. Meta-analysis of gene-level tests for rare variant association Nature Genetics, 46 (2), pp. 200-204. | Show Abstract | Read more

The majority of reported complex disease associations for common genetic variants have been identified through meta-analysis, a powerful approach that enables the use of large sample sizes while protecting against common artifacts due to population structure and repeated small-sample analyses sharing individual-level data. As the focus of genetic association studies shifts to rare variants, genes and other functional units are becoming the focus of analysis. Here we propose and evaluate new approaches for performing meta-analysis of rare variant association tests, including burden tests, weighted burden tests, variable-threshold tests and tests that allow variants with opposite effects to be grouped together. We show that our approach retains useful features from single-variant meta-analysis approaches and demonstrate its use in a study of blood lipid levels in ∼18,500 individuals genotyped with exome arrays. © 2014 Nature America, Inc.

Holmes MV, Asselbergs FW, Palmer TM, Drenos F, Lanktree MB, Nelson CP, Dale CE, Padmanabhan S, Finan C, Swerdlow DI et al. 2015. Mendelian randomization of blood lipids for coronary heart disease. Eur Heart J, 36 (9), pp. 539-550. | Show Abstract | Read more

AIMS: To investigate the causal role of high-density lipoprotein cholesterol (HDL-C) and triglycerides in coronary heart disease (CHD) using multiple instrumental variables for Mendelian randomization. METHODS AND RESULTS: We developed weighted allele scores based on single nucleotide polymorphisms (SNPs) with established associations with HDL-C, triglycerides, and low-density lipoprotein cholesterol (LDL-C). For each trait, we constructed two scores. The first was unrestricted, including all independent SNPs associated with the lipid trait identified from a prior meta-analysis (threshold P < 2 × 10(-6)); and the second a restricted score, filtered to remove any SNPs also associated with either of the other two lipid traits at P ≤ 0.01. Mendelian randomization meta-analyses were conducted in 17 studies including 62,199 participants and 12,099 CHD events. Both the unrestricted and restricted allele scores for LDL-C (42 and 19 SNPs, respectively) associated with CHD. For HDL-C, the unrestricted allele score (48 SNPs) was associated with CHD (OR: 0.53; 95% CI: 0.40, 0.70), per 1 mmol/L higher HDL-C, but neither the restricted allele score (19 SNPs; OR: 0.91; 95% CI: 0.42, 1.98) nor the unrestricted HDL-C allele score adjusted for triglycerides, LDL-C, or statin use (OR: 0.81; 95% CI: 0.44, 1.46) showed a robust association. For triglycerides, the unrestricted allele score (67 SNPs) and the restricted allele score (27 SNPs) were both associated with CHD (OR: 1.62; 95% CI: 1.24, 2.11 and 1.61; 95% CI: 1.00, 2.59, respectively) per 1-log unit increment. However, the unrestricted triglyceride score adjusted for HDL-C, LDL-C, and statin use gave an OR for CHD of 1.01 (95% CI: 0.59, 1.75). CONCLUSION: The genetic findings support a causal effect of triglycerides on CHD risk, but a causal role for HDL-C, though possible, remains less certain.

Baumert J, Huang J, McKnight B, Sabater-Lleal M, Steri M, Chu AY, Trompet S, Lopez LM, Fornage M, Teumer A et al. 2014. No evidence for genome-wide interactions on plasma fibrinogen by smoking, alcohol consumption and body mass index: results from meta-analyses of 80,607 subjects. PLoS One, 9 (12), pp. e111156. | Show Abstract | Read more

Plasma fibrinogen is an acute phase protein playing an important role in the blood coagulation cascade having strong associations with smoking, alcohol consumption and body mass index (BMI). Genome-wide association studies (GWAS) have identified a variety of gene regions associated with elevated plasma fibrinogen concentrations. However, little is yet known about how associations between environmental factors and fibrinogen might be modified by genetic variation. Therefore, we conducted large-scale meta-analyses of genome-wide interaction studies to identify possible interactions of genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentration. The present study included 80,607 subjects of European ancestry from 22 studies. Genome-wide interaction analyses were performed separately in each study for about 2.6 million single nucleotide polymorphisms (SNPs) across the 22 autosomal chromosomes. For each SNP and risk factor, we performed a linear regression under an additive genetic model including an interaction term between SNP and risk factor. Interaction estimates were meta-analysed using a fixed-effects model. No genome-wide significant interaction with smoking status, alcohol consumption or BMI was observed in the meta-analyses. The most suggestive interaction was found for smoking and rs10519203, located in the LOC123688 region on chromosome 15, with a p value of 6.2 × 10(-8). This large genome-wide interaction study including 80,607 participants found no strong evidence of interaction between genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentrations. Further studies are needed to yield deeper insight in the interplay between environmental factors and gene variants on the regulation of fibrinogen concentrations.

Kyriakou T, Seedorf U, Goel A, Hopewell JC, Clarke R, Watkins H, Farrall M. 2014. A common LPA null allele associates with lower lipoprotein(a) levels and coronary artery disease risk Arteriosclerosis, Thrombosis, and Vascular Biology, 34 (9), pp. 2095-2099. | Show Abstract | Read more

OBJECTIVE - Increased levels of lipoprotein(a) are a highly heritable risk factor for coronary artery disease (CAD). The genetic determinants of lipoprotein(a) levels are mainly because of genetic variation in the apolipoprotein(a) gene (LPA). We have tested the association of a relatively common null allele of LPA with lipoprotein(a) levels and CAD risk in a large case-control cohort. We have also examined how null allele genotyping complements apolipoprotein(a) isoform typing to refine the relationship between LPA isoform size and circulating lipoprotein(a) levels. APPROACH AND RESULTS - The LPA null allele (rs41272114) was genotyped in the PROCARDIS (Precocious Coronary Artery Disease) case-control cohort (4073 CAD cases and 4225 controls). Lipoprotein(a) levels were measured in 909 CAD cases and 922 controls; apolipoprotein(a) isoform size was estimated using sodium dodecyl sulfate-agarose gel electrophoresis and a high-throughput quantitative polymerase chain reaction-based method. Null carriers are common (null allele frequency, 3%) and have significantly lower circulating lipoprotein(a) levels (P=2.1×10) and reduced CAD risk (odds ratio, 0.79 [0.66-0.97]; P=0.023) compared with noncarriers. An additive allelic model of apolipoprotein(a) isoform size, refined by null allele genotype and quantitative polymerase chain reaction values, showed a sigmoid relationship with lipoprotein(a) levels, with baseline levels for longer isoform alleles and progressively higher levels of lipoprotein(a) for shorter isoform alleles. CONCLUSIONS - The LPA null allele (rs41272114) is associated with decreased circulating lipoprotein(a) levels and decreased CAD risk. Incorporating rs41272114 refined apolipoprotein(a) isoform size typing obtained by immunoblotting and quantitative polymerase chain reaction. A joint genomic and isoform analysis revealed details of the relationship between apolipoprotein(a) isoform size and circulating lipoprotein(a) level consistent with a threshold effect on lipoprotein secretion. © 2014 American Heart Association, Inc.

Lewis AJM, Finlayson S, Mahmod M, Karamitsos TD, Dass S, Ashrafian H, Francis JM, Watkins H, Beeson D, Palace J, Neubauer S. 2014. A novel cardiac phenotype in patients with GFPT1 or DPAGT1 mutations Experimental and Clinical Cardiology, 20 (8), pp. 3139-3145. | Show Abstract

Mutations in the GFPT1 and DPAGT1 genes, which encode enzymes associated with roles in protein N-linked glycosylation, have been recently identified in a rare subgroup of patients with congenital myasthenic syndromes (CMSs). Aberrant glycosylation is implicated in the development of cardiomyopathies in the congenital disorders of glycosylation. We investigated whether patients with CMS and GFPT1 or DPAGT1 mutations also had evidence of a cardiac phenotype. Cardiovascular magnetic resonance and echocardiography were used to evaluate cardiac structure and function in patients with GFPT1 (n=2) and DPAGT1 (n=2) mutations. Electrocardiography was abnormal in all, with abnormal repolarization and deep S waves (n=3) or left ventricular hypertrophy by voltage criteria (n=1). Despite normal biventricular size and systolic function, GFPT1/DPAGT1 patients demonstrated late gadolinium enhancement suggestive of myocardial fibrosis (n=4), diastolic dysfunction (n=3) and impaired phosphocreatine to adenosine triphosphate ratio (an indicator of myocardial energetic state), assessed using 31P magnetic resonance spectroscopy (n=2). These findings may reflect incipient cardiomyopathy due to aberrant cardiac glycoprotein function and reinforce the need for cardiac surveillance in patients with disorders due to glycosylation pathway defects. © 2013 et al.; licensee Cardiology Academic Press.

Hopewell JC, Seedorf U, Farrall M, Parish S, Kyriakou T, Goel A, Hamsten A, Collins R, Watkins H, Clarke R. 2014. Impact of lipoprotein(a) levels and apolipoprotein(a) isoform size on risk of coronary heart disease Journal of Internal Medicine, 276 (3), pp. 260-268. | Show Abstract | Read more

Observational and genetic studies have shown that lipoprotein(a) [Lp(a)] levels and apolipoprotein(a) [apo(a)] isoform size are both associated with coronary heart disease (CHD) risk, but the relative independence of these risk factors remains unclear. Clarification of this uncertainty is relevant to the potential of future Lp(a)-lowering therapies for the prevention of CHD. Methods: Plasma Lp(a) levels and apo(a) isoform size, estimated by the number of kringle IV (KIV) repeats, were measured in 995 patients with CHD and 998 control subjects. The associations between CHD risk and fifths of Lp(a) levels were assessed before and after adjustment for KIV repeats and, conversely, the associations between CHD risk and fifths of KIV repeats were assessed before and after adjustment for Lp(a) levels. Results: Individuals in the top fifth of Lp(a) levels had more than a twofold higher risk of CHD compared with those in the bottom fifth, and this association was materially unaltered after adjustment for KIV repeats [odds ratio (OR) 2.05, 95% confidence interval (CI) 1.38-3.04, P < 0.001]. Furthermore, almost all of the excess risk was restricted to the two-fifths of the population with the highest Lp(a) levels. Individuals in the bottom fifth of KIV repeats had about a twofold higher risk of CHD compared with those in the top fifth, but this association was no longer significant after adjustment for Lp(a) levels (OR 1.13, 95% CI 0.77-1.66, P = 0.94). Conclusions: The effect of KIV repeats on CHD risk is mediated through their impact on Lp(a) levels, suggesting that absolute levels of Lp(a), rather than apo(a) isoform size, are the main determinant of CHD risk. © 2013 The Association for the Publication of the Journal of Internal Medicine.

Sabater-Lleal M, Mälarstig A, Folkersen L, Soler Artigas M, Baldassarre D, Kavousi M, Almgren P, Veglia F, Brusselle G, Hofman A et al. 2014. Common genetic determinants of lung function, subclinical atherosclerosis and risk of coronary artery disease. PLoS One, 9 (8), pp. e104082. | Show Abstract | Read more

Chronic obstructive pulmonary disease (COPD) independently associates with an increased risk of coronary artery disease (CAD), but it has not been fully investigated whether this co-morbidity involves shared pathophysiological mechanisms. To identify potential common pathways across the two diseases, we tested all recently published single nucleotide polymorphisms (SNPs) associated with human lung function (spirometry) for association with carotid intima-media thickness (cIMT) in 3,378 subjects with multiple CAD risk factors, and for association with CAD in a case-control study of 5,775 CAD cases and 7,265 controls. SNPs rs2865531, located in the CFDP1 gene, and rs9978142, located in the KCNE2 gene, were significantly associated with CAD. In addition, SNP rs9978142 and SNP rs3995090 located in the HTR4 gene, were associated with average and maximal cIMT measures. Genetic risk scores combining the most robustly spirometry-associated SNPs from the literature were modestly associated with CAD, (odds ratio (OR) (95% confidence interval (CI95) = 1.06 (1.03, 1.09); P-value = 1.5 × 10(-4), per allele). In conclusion, our study suggests that some genetic loci implicated in determining human lung function also influence cIMT and susceptibility to CAD. The present results should help elucidate the molecular underpinnings of the co-morbidity observed across COPD and CAD.

Holmes MV, Dale CE, Zuccolo L, Silverwood RJ, Guo Y, Ye Z, Prieto-Merino D, Dehghan A, Trompet S, Wong A et al. 2014. Association between alcohol and cardiovascular disease: Mendelian randomisation analysis based on individual participant data. BMJ, 349 (jul10 6), pp. g4164. | Show Abstract | Read more

OBJECTIVE: To use the rs1229984 variant in the alcohol dehydrogenase 1B gene (ADH1B) as an instrument to investigate the causal role of alcohol in cardiovascular disease. DESIGN: Mendelian randomisation meta-analysis of 56 epidemiological studies. PARTICIPANTS: 261 991 individuals of European descent, including 20 259 coronary heart disease cases and 10 164 stroke events. Data were available on ADH1B rs1229984 variant, alcohol phenotypes, and cardiovascular biomarkers. MAIN OUTCOME MEASURES: Odds ratio for coronary heart disease and stroke associated with the ADH1B variant in all individuals and by categories of alcohol consumption. RESULTS: Carriers of the A-allele of ADH1B rs1229984 consumed 17.2% fewer units of alcohol per week (95% confidence interval 15.6% to 18.9%), had a lower prevalence of binge drinking (odds ratio 0.78 (95% CI 0.73 to 0.84)), and had higher abstention (odds ratio 1.27 (1.21 to 1.34)) than non-carriers. Rs1229984 A-allele carriers had lower systolic blood pressure (-0.88 (-1.19 to -0.56) mm Hg), interleukin-6 levels (-5.2% (-7.8 to -2.4%)), waist circumference (-0.3 (-0.6 to -0.1) cm), and body mass index (-0.17 (-0.24 to -0.10) kg/m(2)). Rs1229984 A-allele carriers had lower odds of coronary heart disease (odds ratio 0.90 (0.84 to 0.96)). The protective association of the ADH1B rs1229984 A-allele variant remained the same across all categories of alcohol consumption (P=0.83 for heterogeneity). Although no association of rs1229984 was identified with the combined subtypes of stroke, carriers of the A-allele had lower odds of ischaemic stroke (odds ratio 0.83 (0.72 to 0.95)). CONCLUSIONS: Individuals with a genetic variant associated with non-drinking and lower alcohol consumption had a more favourable cardiovascular profile and a reduced risk of coronary heart disease than those without the genetic variant. This suggests that reduction of alcohol consumption, even for light to moderate drinkers, is beneficial for cardiovascular health.

Tragante V, Barnes MR, Ganesh SK, Lanktree MB, Guo W, Franceschini N, Smith EN, Johnson T, Holmes MV, Padmanabhan S et al. 2014. Gene-centric meta-analysis in 87,736 individuals of European ancestry identifies multiple blood-pressure-related loci. Am J Hum Genet, 94 (3), pp. 349-360. | Show Abstract | Read more

Blood pressure (BP) is a heritable risk factor for cardiovascular disease. To investigate genetic associations with systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP), we genotyped ~50,000 SNPs in up to 87,736 individuals of European ancestry and combined these in a meta-analysis. We replicated findings in an independent set of 68,368 individuals of European ancestry. Our analyses identified 11 previously undescribed associations in independent loci containing 31 genes including PDE1A, HLA-DQB1, CDK6, PRKAG2, VCL, H19, NUCB2, RELA, HOXC@ complex, FBN1, and NFAT5 at the Bonferroni-corrected array-wide significance threshold (p < 6 × 10(-7)) and confirmed 27 previously reported associations. Bioinformatic analysis of the 11 loci provided support for a putative role in hypertension of several genes, such as CDK6 and NUCB2. Analysis of potential pharmacological targets in databases of small molecules showed that ten of the genes are predicted to be a target for small molecules. In summary, we identified previously unknown loci associated with BP. Our findings extend our understanding of genes involved in BP regulation, which may provide new targets for therapeutic intervention or drug response stratification.

Ormondroyd E, Oates S, Parker M, Blair E, Watkins H. 2014. Pre-symptomatic genetic testing for inherited cardiac conditions: A qualitative exploration of psychosocial and ethical implications European Journal of Human Genetics, 22 (1), pp. 88-93. | Show Abstract | Read more

Inherited cardiac conditions (ICCs) can lead to sudden cardiac death at any age, yet are often asymptomatic and clinically undetected. Prophylactic interventions are available and cascade testing is recommended to identify family members at risk. When a disease-causing mutation has been identified in a family, pre-symptomatic genetic testing (PSGT) is available. This study explores perceptions of the cascade process, impact of PSGT and attitudes towards direct contact as an alternative to family-mediated dissemination for ICCs. In depth, interviews were conducted with 22 participants eligible for PSGT for Hypertrophic Cardiomyopathy or Long QT syndrome. Data were analysed using an inductive, thematic approach. Risk is perceived to be low pre-test in the absence of symptoms, and participants frequently test with the aim of ruling out risk to self and children. Testing of children is a complex decision; although older participants have concerns about possible adverse effects of genetic testing early in the life course, young participants are pragmatic about their result. The meaning of a positive genetic test result may be difficult to conceptualise in the absence of clinical evidence of disease, and this may deter further dissemination to at-risk family members. A majority of participants see advantages in direct contact from health professionals and support it in principle. Implications for practice include addressing risk perception pre-test, and presenting genetic test information as part of a risk stratification process rather than a binary outcome. Families may require more support or intervention in cascading genetic test information. © 2014 Macmillan Publishers Limited.

Hopewell JC, Seedorf U, Farrall M, Parish S, Kyriakou T, Goel A, Hamsten A, Collins R, Watkins H, Clarke R, PROCARDIS Consortium. 2014. Impact of lipoprotein(a) levels and apolipoprotein(a) isoform size on risk of coronary heart disease. J Intern Med, 276 (3), pp. 260-268. | Show Abstract | Read more

OBJECTIVES: Observational and genetic studies have shown that lipoprotein(a) [Lp(a)] levels and apolipoprotein(a) [apo(a)] isoform size are both associated with coronary heart disease (CHD) risk, but the relative independence of these risk factors remains unclear. Clarification of this uncertainty is relevant to the potential of future Lp(a)-lowering therapies for the prevention of CHD. METHODS: Plasma Lp(a) levels and apo(a) isoform size, estimated by the number of kringle IV (KIV) repeats, were measured in 995 patients with CHD and 998 control subjects. The associations between CHD risk and fifths of Lp(a) levels were assessed before and after adjustment for KIV repeats and, conversely, the associations between CHD risk and fifths of KIV repeats were assessed before and after adjustment for Lp(a) levels. RESULTS: Individuals in the top fifth of Lp(a) levels had more than a twofold higher risk of CHD compared with those in the bottom fifth, and this association was materially unaltered after adjustment for KIV repeats [odds ratio (OR) 2.05, 95% confidence interval (CI) 1.38-3.04, P < 0.001]. Furthermore, almost all of the excess risk was restricted to the two-fifths of the population with the highest Lp(a) levels. Individuals in the bottom fifth of KIV repeats had about a twofold higher risk of CHD compared with those in the top fifth, but this association was no longer significant after adjustment for Lp(a) levels (OR 1.13, 95% CI 0.77-1.66, P = 0.94). CONCLUSIONS: The effect of KIV repeats on CHD risk is mediated through their impact on Lp(a) levels, suggesting that absolute levels of Lp(a), rather than apo(a) isoform size, are the main determinant of CHD risk.

Liu DJ, Peloso GM, Zhan X, Holmen OL, Zawistowski M, Feng S, Nikpay M, Auer PL, Goel A, Zhang H et al. 2014. Meta-analysis of gene-level tests for rare variant association. Nat Genet, 46 (2), pp. 200-204. | Show Abstract | Read more

The majority of reported complex disease associations for common genetic variants have been identified through meta-analysis, a powerful approach that enables the use of large sample sizes while protecting against common artifacts due to population structure and repeated small-sample analyses sharing individual-level data. As the focus of genetic association studies shifts to rare variants, genes and other functional units are becoming the focus of analysis. Here we propose and evaluate new approaches for performing meta-analysis of rare variant association tests, including burden tests, weighted burden tests, variable-threshold tests and tests that allow variants with opposite effects to be grouped together. We show that our approach retains useful features from single-variant meta-analysis approaches and demonstrate its use in a study of blood lipid levels in ∼18,500 individuals genotyped with exome arrays.

Pinter K, Grignani RT, Watkins H, Redwood C. 2013. Localisation of AMPK γ subunits in cardiac and skeletal muscles Journal of Muscle Research and Cell Motility, 34 (5-6), pp. 369-378. | Show Abstract | Read more

The trimeric protein AMP-activated protein kinase (AMPK) is an important sensor of energetic status and cellular stress, and mutations in genes encoding two of the regulatory γ subunits cause inherited disorders of either cardiac or skeletal muscle. AMPKγ2 mutations cause hypertrophic cardiomyopathy with glycogen deposition and conduction abnormalities; mutations in AMPKγ3 result in increased skeletal muscle glycogen. In order to gain further insight into the roles of the different γ subunits in muscle and into possible disease mechanisms, we localised the γ2 and γ3 subunits, along with the more abundant γ1 subunit, by immunofluorescence in cardiomyocytes and skeletal muscle fibres. The predominant cardiac γ2 variant, γ2-3B, gave a striated pattern in cardiomyocytes, aligning with the Z-disk but with punctate staining similar to T-tubule (L-type Ca 2+ channel) and sarcoplasmic reticulum (SERCA2) markers. In skeletal muscle fibres AMPKγ3 localises to the I band, presenting a uniform staining that flanks the Z-disk, also coinciding with the position of Ca 2+ influx in these muscles. The localisation of γ2-3B- and γ3-containing AMPK suggests that these trimers may have similar functions in the different muscles. AMPK containing γ2-3B was detected in oxidative skeletal muscles which had low expression of γ3, confirming that these two regulatory subunits may be co-ordinately regulated in response to metabolic requirements. Compartmentalisation of AMPK complexes is most likely dependent on the regulatory γ subunit and this differential localisation may direct substrate selection and specify particular functional roles. © 2013 The Author(s).

Cited:

26

Scopus

Stitziel NO, Fouchier SW, Sjouke B, Peloso GM, Moscoso AM, Auer PL, Goel A, Gigante B, Barnes TA, Melander O et al. 2013. Exome Sequencing and Directed Clinical Phenotyping Diagnose Cholesterol Ester Storage Disease Presenting as Autosomal Recessive Hypercholesterolemia Arteriosclerosis, Thrombosis, and Vascular Biology, 33 (12), pp. 2909-2914. | Show Abstract | Read more

OBJECTIVE - : Autosomal recessive hypercholesterolemia is a rare inherited disorder, characterized by extremely high total and low-density lipoprotein cholesterol levels, that has been previously linked to mutations in LDLRAP1. We identified a family with autosomal recessive hypercholesterolemia not explained by mutations in LDLRAP1 or other genes known to cause monogenic hypercholesterolemia. The aim of this study was to identify the molecular pathogenesis of autosomal recessive hypercholesterolemia in this family. APPROACH AND RESULTS - : We used exome sequencing to assess all protein-coding regions of the genome in 3 family members and identified a homozygous exon 8 splice junction mutation (c.894G>A, also known as E8SJM) in LIPA that segregated with the diagnosis of hypercholesterolemia. Because homozygosity for mutations in LIPA is known to cause cholesterol ester storage disease, we performed directed follow-up phenotyping by noninvasively measuring hepatic cholesterol content. We observed abnormal hepatic accumulation of cholesterol in the homozygote individuals, supporting the diagnosis of cholesterol ester storage disease. Given previous suggestions of cardiovascular disease risk in heterozygous LIPA mutation carriers, we genotyped E8SJM in >27 000 individuals and found no association with plasma lipid levels or risk of myocardial infarction, confirming a true recessive mode of inheritance. CONCLUSIONS - : By integrating observations from Mendelian and population genetics along with directed clinical phenotyping, we diagnosed clinically unapparent cholesterol ester storage disease in the affected individuals from this kindred and addressed an outstanding question about risk of cardiovascular disease in LIPA E8SJM heterozygous carriers. © 2013 American Heart Association, Inc.

Dass S, Holloway CJ, Suttie J, Mahmod M, Dwight JF, Watkins H, Neubauer S, Karamitsos TD. 2013. Is the Myocardium Oxygen Deprived in Non Ischemic Heart Failure? CIRCULATION, 128 (22),

Dichgans M, Malik R, König IR, Rosand J, Clarke R, Gretarsdottir S, Thorleifsson G, Mitchell BD, Assimes TL, Levi C et al. 2014. Shared genetic susceptibility to ischemic stroke and coronary artery disease: a genome-wide analysis of common variants. Stroke, 45 (1), pp. 24-36. | Show Abstract | Read more

BACKGROUND AND PURPOSE: Ischemic stroke (IS) and coronary artery disease (CAD) share several risk factors and each has a substantial heritability. We conducted a genome-wide analysis to evaluate the extent of shared genetic determination of the two diseases. METHODS: Genome-wide association data were obtained from the METASTROKE, Coronary Artery Disease Genome-wide Replication and Meta-analysis (CARDIoGRAM), and Coronary Artery Disease (C4D) Genetics consortia. We first analyzed common variants reaching a nominal threshold of significance (P<0.01) for CAD for their association with IS and vice versa. We then examined specific overlap across phenotypes for variants that reached a high threshold of significance. Finally, we conducted a joint meta-analysis on the combined phenotype of IS or CAD. Corresponding analyses were performed restricted to the 2167 individuals with the ischemic large artery stroke (LAS) subtype. RESULTS: Common variants associated with CAD at P<0.01 were associated with a significant excess risk for IS and for LAS and vice versa. Among the 42 known genome-wide significant loci for CAD, 3 and 5 loci were significantly associated with IS and LAS, respectively. In the joint meta-analyses, 15 loci passed genome-wide significance (P<5×10(-8)) for the combined phenotype of IS or CAD and 17 loci passed genome-wide significance for LAS or CAD. Because these loci had prior evidence for genome-wide significance for CAD, we specifically analyzed the respective signals for IS and LAS and found evidence for association at chr12q24/SH2B3 (PIS=1.62×10(-7)) and ABO (PIS=2.6×10(-4)), as well as at HDAC9 (PLAS=2.32×10(-12)), 9p21 (PLAS=3.70×10(-6)), RAI1-PEMT-RASD1 (PLAS=2.69×10(-5)), EDNRA (PLAS=7.29×10(-4)), and CYP17A1-CNNM2-NT5C2 (PLAS=4.9×10(-4)). CONCLUSIONS: Our results demonstrate substantial overlap in the genetic risk of IS and particularly the LAS subtype with CAD.

Stitziel NO, Fouchier SW, Sjouke B, Peloso GM, Moscoso AM, Auer PL, Goel A, Gigante B, Barnes TA, Melander O et al. 2013. Exome sequencing and directed clinical phenotyping diagnose cholesterol ester storage disease presenting as autosomal recessive hypercholesterolemia. Arterioscler Thromb Vasc Biol, 33 (12), pp. 2909-2914. | Show Abstract | Read more

OBJECTIVE: Autosomal recessive hypercholesterolemia is a rare inherited disorder, characterized by extremely high total and low-density lipoprotein cholesterol levels, that has been previously linked to mutations in LDLRAP1. We identified a family with autosomal recessive hypercholesterolemia not explained by mutations in LDLRAP1 or other genes known to cause monogenic hypercholesterolemia. The aim of this study was to identify the molecular pathogenesis of autosomal recessive hypercholesterolemia in this family. APPROACH AND RESULTS: We used exome sequencing to assess all protein-coding regions of the genome in 3 family members and identified a homozygous exon 8 splice junction mutation (c.894G>A, also known as E8SJM) in LIPA that segregated with the diagnosis of hypercholesterolemia. Because homozygosity for mutations in LIPA is known to cause cholesterol ester storage disease, we performed directed follow-up phenotyping by noninvasively measuring hepatic cholesterol content. We observed abnormal hepatic accumulation of cholesterol in the homozygote individuals, supporting the diagnosis of cholesterol ester storage disease. Given previous suggestions of cardiovascular disease risk in heterozygous LIPA mutation carriers, we genotyped E8SJM in >27 000 individuals and found no association with plasma lipid levels or risk of myocardial infarction, confirming a true recessive mode of inheritance. CONCLUSIONS: By integrating observations from Mendelian and population genetics along with directed clinical phenotyping, we diagnosed clinically unapparent cholesterol ester storage disease in the affected individuals from this kindred and addressed an outstanding question about risk of cardiovascular disease in LIPA E8SJM heterozygous carriers.

Pinter K, Grignani RT, Watkins H, Redwood C. 2013. Localisation of AMPK γ subunits in cardiac and skeletal muscles. J Muscle Res Cell Motil, 34 (5-6), pp. 369-378. | Show Abstract | Read more

The trimeric protein AMP-activated protein kinase (AMPK) is an important sensor of energetic status and cellular stress, and mutations in genes encoding two of the regulatory γ subunits cause inherited disorders of either cardiac or skeletal muscle. AMPKγ2 mutations cause hypertrophic cardiomyopathy with glycogen deposition and conduction abnormalities; mutations in AMPKγ3 result in increased skeletal muscle glycogen. In order to gain further insight into the roles of the different γ subunits in muscle and into possible disease mechanisms, we localised the γ2 and γ3 subunits, along with the more abundant γ1 subunit, by immunofluorescence in cardiomyocytes and skeletal muscle fibres. The predominant cardiac γ2 variant, γ2-3B, gave a striated pattern in cardiomyocytes, aligning with the Z-disk but with punctate staining similar to T-tubule (L-type Ca(2+) channel) and sarcoplasmic reticulum (SERCA2) markers. In skeletal muscle fibres AMPKγ3 localises to the I band, presenting a uniform staining that flanks the Z-disk, also coinciding with the position of Ca(2+) influx in these muscles. The localisation of γ2-3B- and γ3-containing AMPK suggests that these trimers may have similar functions in the different muscles. AMPK containing γ2-3B was detected in oxidative skeletal muscles which had low expression of γ3, confirming that these two regulatory subunits may be co-ordinately regulated in response to metabolic requirements. Compartmentalisation of AMPK complexes is most likely dependent on the regulatory γ subunit and this differential localisation may direct substrate selection and specify particular functional roles.

Cahill TJ, Ashrafian H, Watkins H. 2013. Genetic cardiomyopathies causing heart failure. Circ Res, 113 (6), pp. 660-675. | Show Abstract | Read more

Despite the striking advances in medical and surgical therapy, the morbidity, mortality, and economic burden of heart failure (HF) remain unacceptably high. There is increasing evidence that the risk and course of HF depend on genetic predisposition; however, the genetic contribution to HF is heterogeneous and complex. At one end of the spectrum are the familial monogenic HF syndromes in which causative mutations are rare but highly penetrant. At the other, HF susceptibility and course may be influenced by more common, less penetrant genetic variants. As detailed in this review, efforts to unravel the basis of the familial cardiomyopathies at the mendelian end of the spectrum already have begun to deliver on the promise of informative mechanisms, novel gene-based diagnostics, and therapies for distinct subtypes of HF. However, continued progress requires the differentiation of pathogenic mutations, disease modifiers, and rare, benign variants in the deluge of data emerging from increasingly accessible novel sequencing technologies. This represents a significant challenge and demands a sustained effort in analysis of extended family pedigrees, diligent clinical phenotyping, and systematic annotation of human genetic variation.

Sabater-Lleal M, Huang J, Chasman D, Naitza S, Dehghan A, Johnson AD, Teumer A, Reiner AP, Folkersen L, Basu S et al. 2013. Multiethnic meta-analysis of genome-wide association studies in >100 000 subjects identifies 23 fibrinogen-associated Loci but no strong evidence of a causal association between circulating fibrinogen and cardiovascular disease. Circulation, 128 (12), pp. 1310-1324. | Show Abstract | Read more

BACKGROUND: Estimates of the heritability of plasma fibrinogen concentration, an established predictor of cardiovascular disease, range from 34% to 50%. Genetic variants so far identified by genome-wide association studies explain only a small proportion (<2%) of its variation. METHODS AND RESULTS: We conducted a meta-analysis of 28 genome-wide association studies including >90 000 subjects of European ancestry, the first genome-wide association meta-analysis of fibrinogen levels in 7 studies in blacks totaling 8289 samples, and a genome-wide association study in Hispanics totaling 1366 samples. Evaluation for association of single-nucleotide polymorphisms with clinical outcomes included a total of 40 695 cases and 85 582 controls for coronary artery disease, 4752 cases and 24 030 controls for stroke, and 3208 cases and 46 167 controls for venous thromboembolism. Overall, we identified 24 genome-wide significant (P<5×10(-8)) independent signals in 23 loci, including 15 novel associations, together accounting for 3.7% of plasma fibrinogen variation. Gene-set enrichment analysis highlighted key roles in fibrinogen regulation for the 3 structural fibrinogen genes and pathways related to inflammation, adipocytokines, and thyrotrophin-releasing hormone signaling. Whereas lead single-nucleotide polymorphisms in a few loci were significantly associated with coronary artery disease, the combined effect of all 24 fibrinogen-associated lead single-nucleotide polymorphisms was not significant for coronary artery disease, stroke, or venous thromboembolism. CONCLUSIONS: We identify 23 robustly associated fibrinogen loci, 15 of which are new. Clinical outcome analysis of these loci does not support a causal relationship between circulating levels of fibrinogen and coronary artery disease, stroke, or venous thromboembolism.

Holmes MV, Simon T, Exeter HJ, Folkersen L, Asselbergs FW, Guardiola M, Cooper JA, Palmen J, Hubacek JA, Carruthers KF et al. 2013. Secretory phospholipase A(2)-IIA and cardiovascular disease: a mendelian randomization study. J Am Coll Cardiol, 62 (21), pp. 1966-1976. | Show Abstract | Read more

OBJECTIVES: This study sought to investigate the role of secretory phospholipase A2 (sPLA2)-IIA in cardiovascular disease. BACKGROUND: Higher circulating levels of sPLA2-IIA mass or sPLA2 enzyme activity have been associated with increased risk of cardiovascular events. However, it is not clear if this association is causal. A recent phase III clinical trial of an sPLA2 inhibitor (varespladib) was stopped prematurely for lack of efficacy. METHODS: We conducted a Mendelian randomization meta-analysis of 19 general population studies (8,021 incident, 7,513 prevalent major vascular events [MVE] in 74,683 individuals) and 10 acute coronary syndrome (ACS) cohorts (2,520 recurrent MVE in 18,355 individuals) using rs11573156, a variant in PLA2G2A encoding the sPLA2-IIA isoenzyme, as an instrumental variable. RESULTS: PLA2G2A rs11573156 C allele associated with lower circulating sPLA2-IIA mass (38% to 44%) and sPLA2 enzyme activity (3% to 23%) per C allele. The odds ratio (OR) for MVE per rs11573156 C allele was 1.02 (95% confidence interval [CI]: 0.98 to 1.06) in general populations and 0.96 (95% CI: 0.90 to 1.03) in ACS cohorts. In the general population studies, the OR derived from the genetic instrumental variable analysis for MVE for a 1-log unit lower sPLA2-IIA mass was 1.04 (95% CI: 0.96 to 1.13), and differed from the non-genetic observational estimate (OR: 0.69; 95% CI: 0.61 to 0.79). In the ACS cohorts, both the genetic instrumental variable and observational ORs showed a null association with MVE. Instrumental variable analysis failed to show associations between sPLA2 enzyme activity and MVE. CONCLUSIONS: Reducing sPLA2-IIA mass is unlikely to be a useful therapeutic goal for preventing cardiovascular events.

van Meurs JB, Pare G, Schwartz SM, Hazra A, Tanaka T, Vermeulen SH, Cotlarciuc I, Yuan X, Mälarstig A, Bandinelli S et al. 2013. Common genetic loci influencing plasma homocysteine concentrations and their effect on risk of coronary artery disease. Am J Clin Nutr, 98 (3), pp. 668-676. | Show Abstract | Read more

BACKGROUND: The strong observational association between total homocysteine (tHcy) concentrations and risk of coronary artery disease (CAD) and the null associations in the homocysteine-lowering trials have prompted the need to identify genetic variants associated with homocysteine concentrations and risk of CAD. OBJECTIVE: We tested whether common genetic polymorphisms associated with variation in tHcy are also associated with CAD. DESIGN: We conducted a meta-analysis of genome-wide association studies (GWAS) on tHcy concentrations in 44,147 individuals of European descent. Polymorphisms associated with tHcy (P < 10(⁻⁸) were tested for association with CAD in 31,400 cases and 92,927 controls. RESULTS: Common variants at 13 loci, explaining 5.9% of the variation in tHcy, were associated with tHcy concentrations, including 6 novel loci in or near MMACHC (2.1 × 10⁻⁹), SLC17A3 (1.0 × 10⁻⁸), GTPB10 (1.7 × 10⁻⁸), CUBN (7.5 × 10⁻¹⁰), HNF1A (1.2 × 10⁻¹²)), and FUT2 (6.6 × 10⁻⁹), and variants previously reported at or near the MTHFR, MTR, CPS1, MUT, NOX4, DPEP1, and CBS genes. Individuals within the highest 10% of the genotype risk score (GRS) had 3-μmol/L higher mean tHcy concentrations than did those within the lowest 10% of the GRS (P = 1 × 10⁻³⁶). The GRS was not associated with risk of CAD (OR: 1.01; 95% CI: 0.98, 1.04; P = 0.49). CONCLUSIONS: We identified several novel loci that influence plasma tHcy concentrations. Overall, common genetic variants that influence plasma tHcy concentrations are not associated with risk of CAD in white populations, which further refutes the causal relevance of moderately elevated tHcy concentrations and tHcy-related pathways for CAD.

Chan K, Patel RS, Newcombe P, Nelson CP, Qasim A, Epstein SE, Burnett S, Vaccarino VL, Zafari AM, Shah SH et al. 2013. CHROMOSOME 9P21 LOCUS AND ANGIOGRAPHIC CORONARY ARTERY DISEASE BURDEN: A COLLABORATIVE META-ANALYSIS HEART, 99 (Suppl 2), pp. A75-A75. | Read more

Leon DA, Shkolnikov VM, Borinskaya S, Casas JP, Evans A, Gil A, Kee F, Kiryanov N, McKee M, O'Doherty MG et al. 2013. Hazardous alcohol consumption is associated with increased levels of B-type natriuretic peptide: Evidence from two population-based studies European Journal of Epidemiology, 28 (5), pp. 393-404. | Show Abstract | Read more

Russia has very high mortality from cardiovascular disease (CVD), with evidence that heavy drinking may play a role. To throw further light on this association we have studied the association of alcohol with predictors of CVD risk including B-type natriuretic peptide (BNP). Levels of BNP increase primarily in response to abnormal cardiac chamber wall stretch which can occur both as a result of atherosclerosis as well as due to other types of damage to the myocardium. No previous population-based studies have investigated the association with alcohol. We analysed cross-sectional data on drinking behaviour in 993 men aged 25-60 years from the Izhevsk Family Study 2 (IFS2), conducted in the Russian city of Izhevsk in 2008-2009. Relative to non-drinkers, men who drank hazardously had an odds ratio (OR) of being in the top 20 % of the BNP distribution of 4.66 (95 % CI 2.13, 10.19) adjusted for age, obesity, waist-hip ratio, and smoking. Further adjustment for class of hypertension resulted in only slight attenuation of the effect, suggesting that this effect was not secondary to the influence of alcohol on blood pressure. In contrast hazardous drinking was associated with markedly raised ApoA1 and HDL cholesterol levels, but had little impact on levels of ApoB and LDL cholesterol. Similar but less pronounced associations were found in the Belfast (UK) component of the PRIME study conducted in 1991. These findings suggest that the association of heavy drinking with increased risk of cardiovascular disease may be partly due to alcohol-induced non-atherosclerotic damage to the myocardium. © 2013 The Author(s).

Ormondroyd E, Oates S, Parker M, Blair E, Watkins H. 2014. Pre-symptomatic genetic testing for inherited cardiac conditions: a qualitative exploration of psychosocial and ethical implications. Eur J Hum Genet, 22 (1), pp. 88-93. | Show Abstract | Read more

Inherited cardiac conditions (ICCs) can lead to sudden cardiac death at any age, yet are often asymptomatic and clinically undetected. Prophylactic interventions are available and cascade testing is recommended to identify family members at risk. When a disease-causing mutation has been identified in a family, pre-symptomatic genetic testing (PSGT) is available. This study explores perceptions of the cascade process, impact of PSGT and attitudes towards direct contact as an alternative to family-mediated dissemination for ICCs. In depth, interviews were conducted with 22 participants eligible for PSGT for Hypertrophic Cardiomyopathy or Long QT syndrome. Data were analysed using an inductive, thematic approach. Risk is perceived to be low pre-test in the absence of symptoms, and participants frequently test with the aim of ruling out risk to self and children. Testing of children is a complex decision; although older participants have concerns about possible adverse effects of genetic testing early in the life course, young participants are pragmatic about their result. The meaning of a positive genetic test result may be difficult to conceptualise in the absence of clinical evidence of disease, and this may deter further dissemination to at-risk family members. A majority of participants see advantages in direct contact from health professionals and support it in principle. Implications for practice include addressing risk perception pre-test, and presenting genetic test information as part of a risk stratification process rather than a binary outcome. Families may require more support or intervention in cascading genetic test information.

Berndt SI, Gustafsson S, Mägi R, Ganna A, Wheeler E, Feitosa MF, Justice AE, Monda KL, Croteau-Chonka DC, Day FR et al. 2013. Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture. Nat Genet, 45 (5), pp. 501-512. | Show Abstract | Read more

Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.

Karamitsos TD, Dass S, Suttie J, Sever E, Birks J, Holloway CJ, Robson MD, Jerosch-Herold M, Watkins H, Neubauer S. 2013. Blunted myocardial oxygenation response during vasodilator stress in patients with hypertrophic cardiomyopathy. J Am Coll Cardiol, 61 (11), pp. 1169-1176. | Show Abstract | Read more

OBJECTIVES: This study sought to assess myocardial perfusion and tissue oxygenation during vasodilator stress in patients with overt hypertrophic cardiomyopathy (HCM), as well as in HCM mutation carriers without left ventricular (LV) hypertrophy, and to compare findings to those in athletes with comparable hypertrophy and normal controls. BACKGROUND: Myocardial perfusion under vasodilator stress is impaired in patients with HCM. Whether this is associated with impaired myocardial oxygenation and tissue ischemia is unknown. Furthermore, it is not known whether perfusion and oxygenation are impaired in HCM mutation carriers without left ventricular hypertrophy (LVH). METHODS: A total of 27 patients with overt HCM, 10 HCM mutation carriers without LVH, 11 athletes, and 20 healthy controls underwent cardiovascular magnetic resonance (CMR) scanning at 3-T. Myocardial function, perfusion (perfusion reserve index [MPRI]), and oxygenation (blood-oxygen level dependent signal intensity [SI] change) under adenosine stress were assessed. RESULTS: MPRI was significantly reduced in HCM (1.3 ± 0.1) compared to controls (1.8 ± 0.1, p < 0.001) and athletes (2.0 ± 0.1, p < 0.001), but remained normal in HCM mutation carriers without LVH (1.7 ± 0.1; p = 0.61 vs. controls, p = 0.02 vs. overt HCM). Oxygenation response was attenuated in overt HCM (SI change 6.9 ± 1.4%) compared to controls (18.9 ± 1.4%, p < 0.0001) and athletes (18.7 ± 2.0%, p < 0.001). Interestingly, HCM mutation carriers without LVH also showed an impaired oxygenation response to adenosine (10.4 ± 2.0%; p = 0.001 vs. controls, p = 0.16 vs. overt HCM, p = 0.003 vs. athletes). CONCLUSIONS: In overt HCM, both perfusion and oxygenation are impaired during vasodilator stress. However, in HCM mutation carriers without LVH, only oxygenation is impaired. In athletes, stress perfusion and oxygenation are normal. CMR assessment of myocardial oxygenation has the potential to become a novel risk factor in HCM.

Dass S, Suttie JJ, Piechnik SK, Ferreira VM, Holloway CJ, Banerjee R, Mahmod M, Cochlin L, Karamitsos TD, Robson MD et al. 2013. Response to letter regarding article, "myocardial tissue characterization using magnetic resonance noncontrast t1 mapping in hypertrophic and dilated cardiomyopathy". Circ Cardiovasc Imaging, 6 (2), pp. e2. | Read more

Watkins H. 2013. Assigning a causal role to genetic variants in hypertrophic cardiomyopathy. Circ Cardiovasc Genet, 6 (1), pp. 2-4. | Read more

Lygate CA, Aksentijevic D, Dawson D, ten Hove M, Phillips D, de Bono JP, Medway DJ, Sebag-Montefiore L, Hunyor I, Channon KM et al. 2013. Living without creatine: unchanged exercise capacity and response to chronic myocardial infarction in creatine-deficient mice. Circ Res, 112 (6), pp. 945-955. | Show Abstract | Read more

RATIONALE: Creatine is thought to be involved in the spatial and temporal buffering of ATP in energetic organs such as heart and skeletal muscle. Creatine depletion affects force generation during maximal stimulation, while reduced levels of myocardial creatine are a hallmark of the failing heart, leading to the widely held view that creatine is important at high workloads and under conditions of pathological stress. OBJECTIVE: We therefore hypothesised that the consequences of creatine-deficiency in mice would be impaired running capacity, and exacerbation of heart failure following myocardial infarction. METHODS AND RESULTS: Surprisingly, mice with whole-body creatine deficiency due to knockout of the biosynthetic enzyme (guanidinoacetate N-methyltransferase [GAMT]) voluntarily ran just as fast and as far as controls (>10 km/night) and performed the same level of work when tested to exhaustion on a treadmill. Furthermore, survival following myocardial infarction was not altered, nor was subsequent left ventricular (LV) remodelling and development of chronic heart failure exacerbated, as measured by 3D-echocardiography and invasive hemodynamics. These findings could not be accounted for by compensatory adaptations, with no differences detected between WT and GAMT(-/-) proteomes. Alternative phosphotransfer mechanisms were explored; adenylate kinase activity was unaltered, and although GAMT(-/-) hearts accumulated the creatine precursor guanidinoacetate, this had negligible energy-transfer activity, while mitochondria retained near normal function. CONCLUSIONS: Creatine-deficient mice show unaltered maximal exercise capacity and response to chronic myocardial infarction, and no obvious metabolic adaptations. Our results question the paradigm that creatine is essential for high workload and chronic stress responses in heart and skeletal muscle.

Chan K, Patel RS, Newcombe P, Nelson CP, Qasim A, Epstein SE, Burnett S, Vaccarino VL, Zafari AM, Shah SH et al. 2013. Association between the chromosome 9p21 locus and angiographic coronary artery disease burden: a collaborative meta-analysis. J Am Coll Cardiol, 61 (9), pp. 957-970. | Show Abstract | Read more

OBJECTIVES: This study sought to ascertain the relationship of 9p21 locus with: 1) angiographic coronary artery disease (CAD) burden; and 2) myocardial infarction (MI) in individuals with underlying CAD. BACKGROUND: Chromosome 9p21 variants have been robustly associated with coronary heart disease, but questions remain on the mechanism of risk, specifically whether the locus contributes to coronary atheroma burden or plaque instability. METHODS: We established a collaboration of 21 studies consisting of 33,673 subjects with information on both CAD (clinical or angiographic) and MI status along with 9p21 genotype. Tabular data are provided for each cohort on the presence and burden of angiographic CAD, MI cases with underlying CAD, and the diabetic status of all subjects. RESULTS: We first confirmed an association between 9p21 and CAD with angiographically defined cases and control subjects (pooled odds ratio [OR]: 1.31, 95% confidence interval [CI]: 1.20 to 1.43). Among subjects with angiographic CAD (n = 20,987), random-effects model identified an association with multivessel CAD, compared with those with single-vessel disease (OR: 1.10, 95% CI: 1.04 to 1.17)/copy of risk allele). Genotypic models showed an OR of 1.15, 95% CI: 1.04 to 1.26 for heterozygous carrier and OR: 1.23, 95% CI: 1.08 to 1.39 for homozygous carrier. Finally, there was no significant association between 9p21 and prevalent MI when both cases (n = 17,791) and control subjects (n = 15,882) had underlying CAD (OR: 0.99, 95% CI: 0.95 to 1.03)/risk allele. CONCLUSIONS: The 9p21 locus shows convincing association with greater burden of CAD but not with MI in the presence of underlying CAD. This adds further weight to the hypothesis that 9p21 locus primarily mediates an atherosclerotic phenotype.

Guo Y, Lanktree MB, Taylor KC, Hakonarson H, Lange LA, Keating BJ, IBC 50K SNP array BMI Consortium. 2013. Gene-centric meta-analyses of 108 912 individuals confirm known body mass index loci and reveal three novel signals. Hum Mol Genet, 22 (1), pp. 184-201. | Show Abstract | Read more

Recent genetic association studies have made progress in uncovering components of the genetic architecture of the body mass index (BMI). We used the ITMAT-Broad-Candidate Gene Association Resource (CARe) (IBC) array comprising up to 49 320 single nucleotide polymorphisms (SNPs) across ~2100 metabolic and cardiovascular-related loci to genotype up to 108 912 individuals of European ancestry (EA), African-Americans, Hispanics and East Asians, from 46 studies, to provide additional insight into SNPs underpinning BMI. We used a five-phase study design: Phase I focused on meta-analysis of EA studies providing individual level genotype data; Phase II performed a replication of cohorts providing summary level EA data; Phase III meta-analyzed results from the first two phases; associated SNPs from Phase III were used for replication in Phase IV; finally in Phase V, a multi-ethnic meta-analysis of all samples from four ethnicities was performed. At an array-wide significance (P < 2.40E-06), we identify novel BMI associations in loci translocase of outer mitochondrial membrane 40 homolog (yeast) - apolipoprotein E - apolipoprotein C-I (TOMM40-APOE-APOC1) (rs2075650, P = 2.95E-10), sterol regulatory element binding transcription factor 2 (SREBF2, rs5996074, P = 9.43E-07) and neurotrophic tyrosine kinase, receptor, type 2 [NTRK2, a brain-derived neurotrophic factor (BDNF) receptor gene, rs1211166, P = 1.04E-06] in the Phase IV meta-analysis. Of 10 loci with previous evidence for BMI association represented on the IBC array, eight were replicated, with the remaining two showing nominal significance. Conditional analyses revealed two independent BMI-associated signals in BDNF and melanocortin 4 receptor (MC4R) regions. Of the 11 array-wide significant SNPs, three are associated with gene expression levels in both primary B-cells and monocytes; with rs4788099 in SH2B adaptor protein 1 (SH2B1) notably being associated with the expression of multiple genes in cis. These multi-ethnic meta-analyses expand our knowledge of BMI genetics.

Song C, Pedersen NL, Reynolds CA, Sabater-Lleal M, Kanoni S, Willenborg C, CARDIoGRAMplusC4D Consortium, Syvänen AC, Watkins H, Hamsten A et al. 2013. Genetic variants from lipid-related pathways and risk for incident myocardial infarction. PLoS One, 8 (3), pp. e60454. | Show Abstract | Read more

BACKGROUND: Circulating lipids levels, as well as several familial lipid metabolism disorders, are strongly associated with initiation and progression of atherosclerosis and incidence of myocardial infarction (MI). OBJECTIVES: We hypothesized that genetic variants associated with circulating lipid levels would also be associated with MI incidence, and have tested this in three independent samples. SETTING AND SUBJECTS: Using age- and sex-adjusted additive genetic models, we analyzed 554 single nucleotide polymorphisms (SNPs) in 41 candidate gene regions proposed to be involved in lipid-related pathways potentially predisposing to incidence of MI in 2,602 participants of the Swedish Twin Register (STR; 57% women). All associations with nominal P<0.01 were further investigated in the Uppsala Longitudinal Study of Adult Men (ULSAM; N = 1,142). RESULTS: In the present study, we report associations of lipid-related SNPs with incident MI in two community-based longitudinal studies with in silico replication in a meta-analysis of genome-wide association studies. Overall, there were 9 SNPs in STR with nominal P-value <0.01 that were successfully genotyped in ULSAM. rs4149313 located in ABCA1 was associated with MI incidence in both longitudinal study samples with nominal significance (hazard ratio, 1.36 and 1.40; P-value, 0.004 and 0.015 in STR and ULSAM, respectively). In silico replication supported the association of rs4149313 with coronary artery disease in an independent meta-analysis including 173,975 individuals of European descent from the CARDIoGRAMplusC4D consortium (odds ratio, 1.03; P-value, 0.048). CONCLUSIONS: rs4149313 is one of the few amino acid changing variants in ABCA1 known to associate with reduced cholesterol efflux. Our results are suggestive of a weak association between this variant and the development of atherosclerosis and MI.

Athanasiadis G, Sabater-Lleal M, Buil A, Souto JC, Borrell M, Lathrop M, Watkins H, Almasy L, Hamsten A, Soria JM. 2013. Genetic determinants of plasma β₂-glycoprotein I levels: a genome-wide association study in extended pedigrees from Spain. J Thromb Haemost, 11 (3), pp. 521-528. | Show Abstract | Read more

BACKGROUND: β2 -Glycoprotein I (β2 -GPI), also designated apolipoprotein H, is a 50-kDa protein that circulates in blood at high concentrations, playing important roles in autoimmune diseases, hemostasis, atherogenesis, and angiogenesis, as well as in host defense against bacteria and in protein/cellular waste removal. Plasma β2 -GPI levels have a significant genetic component (heritability of ~ 80%). OBJECTIVES: To present the results of a genome-wide association study for plasma β2 -GPI levels in a set of extended pedigrees from the Genetic Analysis of Idiopathic Thrombophilia (GAIT) Project. PATIENTS/METHODS: A total of 306 individuals for whom β2 -GPI plasma measurements were available were typed for 307,984 single-nucleotide polymorphisms (SNPs) with the Infinium 317k Beadchip (Illumina). Association with the β2 -GPI phenotype was investigated through variance component analysis, and the most significant results were followed up for association with coronary artery disease (CAD) in an independent in silico analysis involving 5765 CAD cases from the PROCARDIS Project and 7264 controls from the PROCARDIS Project and the Wellcome Trust Case Control Consortium (WTCCC) collection. RESULTS: After correction for multiple testing, three SNPs located in/around two genes (ELF5 and SCUBE2) reached genome-wide significance. Moreover, an SNP in the APOH gene showed suggestive association with the β2 -GPI phenotype. Some of the identified genes are plausible biological candidates, as they are actually or potentially involved in inflammatory processes. CONCLUSIONS: Our results represent a first step towards identifying common variants reflecting the genetic architecture influencing plasma β2 -GPI levels, and warrant further validation by functional experiments, as the functions of some of the discovered loci are still unknown.

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Lygate CA, Aksentijevic D, Dawson D, Ten Hove M, Phillips D, De Bono JP, Medway DJ, Sebag-Montefiore L, Hunyor I, Channon KM et al. 2013. Living without creatine: Unchanged exercise capacity and response to chronic myocardial infarction in creatine-deficient mice Circulation Research, 112 (6), pp. 945-955. | Show Abstract | Read more

RATIONALE:: Creatine is thought to be involved in the spatial and temporal buffering of ATP in energetic organs such as heart and skeletal muscle. Creatine depletion affects force generation during maximal stimulation, while reduced levels of myocardial creatine are a hallmark of the failing heart, leading to the widely held view that creatine is important at high workloads and under conditions of pathological stress. OBJECTIVE:: We therefore hypothesised that the consequences of creatine-deficiency in mice would be impaired running capacity, and exacerbation of heart failure following myocardial infarction. METHODS AND RESULTS:: Surprisingly, mice with whole-body creatine deficiency due to knockout of the biosynthetic enzyme (guanidinoacetate N-methyltransferase [GAMT]) voluntarily ran just as fast and as far as controls (>10 km/night) and performed the same level of work when tested to exhaustion on a treadmill. Furthermore, survival following myocardial infarction was not altered, nor was subsequent left ventricular (LV) remodelling and development of chronic heart failure exacerbated, as measured by 3D-echocardiography and invasive hemodynamics. These findings could not be accounted for by compensatory adaptations, with no differences detected between WT and GAMT proteomes. Alternative phosphotransfer mechanisms were explored; adenylate kinase activity was unaltered, and although GAMT hearts accumulated the creatine precursor guanidinoacetate, this had negligible energy-transfer activity, while mitochondria retained near normal function. CONCLUSIONS:: Creatine-deficient mice show unaltered maximal exercise capacity and response to chronic myocardial infarction, and no obvious metabolic adaptations. Our results question the paradigm that creatine is essential for high workload and chronic stress responses in heart and skeletal muscle. © 2013 American Heart Association, Inc.

Dodd MS, Ball V, Bray R, Ashrafian H, Watkins H, Clarke K, Tyler DJ. 2013. In vivo mouse cardiac hyperpolarized magnetic resonance spectroscopy. J Cardiovasc Magn Reson, 15 (1), pp. 19. | Show Abstract | Read more

BACKGROUND: Alterations in cardiac metabolism accompany many diseases of the heart. The advent of cardiac hyperpolarized magnetic resonance spectroscopy (MRS), via dynamic nuclear polarization (DNP), has enabled a greater understanding of the in vivo metabolic changes that occur as a consequence of myocardial infarction, hypertrophy and diabetes. However, all cardiac studies performed to date have focused on rats and larger animals, whereas more information could be gained through the study of transgenic mouse models of heart disease. Translation from the rat to the mouse is challenging, due in part to the reduced heart size (1/10(th)) and the increased heart rate (50%) in the mouse compared to the rat. METHODS AND RESULTS: In this study, we have investigated the in vivo metabolism of [1-(13)C]pyruvate in the mouse heart. To demonstrate the sensitivity of the method to detect alterations in pyruvate dehydrogenase (PDH) flux, two well characterised methods of PDH modulation were performed; overnight fasting and infusion of sodium dichloroacetate (DCA). Fasting resulted in an 85% reduction in PDH flux, whilst DCA infusion increased PDH flux by 123%. A comparison of three commonly used control mouse strains was performed revealing significant metabolic differences between strains. CONCLUSIONS: We have successfully demonstrated a hyperpolarized DNP protocol to investigate in vivo alterations within the diseased mouse heart. This technique offers a significant advantage over existing in vitro techniques as it reduces animal numbers and decreases biological variability. Thus [1-(13)C]pyruvate can be used to provide an in vivo cardiac metabolic profile of transgenic mice.

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Deloukas P, Kanoni S, Willenborg C, Farrall M, Assimes TL, Thompson JR, Ingelsson E, Saleheen D, Erdmann J, Goldstein BA et al. 2013. Large-scale association analysis identifies new risk loci for coronary artery disease Nature Genetics, 45 (1), pp. 25-33. | Show Abstract | Read more

Coronary artery disease (CAD) is the commonest cause of death. Here, we report an association analysis in 63,746 CAD cases and 130,681 controls identifying 15 loci reaching genome-wide significance, taking the number of susceptibility loci for CAD to 46, and a further 104 independent variants (r 2 < 0.2) strongly associated with CAD at a 5% false discovery rate (FDR). Together, these variants explain approximately 10.6% of CAD heritability. Of the 46 genome-wide significant lead SNPs, 12 show a significant association with a lipid trait, and 5 show a significant association with blood pressure, but none is significantly associated with diabetes. Network analysis with 233 candidate genes (loci at 10% FDR) generated 5 interaction networks comprising 85% of these putative genes involved in CAD. The four most significant pathways mapping to these networks are linked to lipid metabolism and inflammation, underscoring the causal role of these activities in the genetic etiology of CAD. Our study provides insights into the genetic basis of CAD and identifies key biological pathways. © 2013 Nature America, Inc. All rights reserved.

Köttgen A, Albrecht E, Teumer A, Vitart V, Krumsiek J, Hundertmark C, Pistis G, Ruggiero D, O'Seaghdha CM, Haller T et al. 2013. Genome-wide association analyses identify 18 new loci associated with serum urate concentrations. Nat Genet, 45 (2), pp. 145-154. | Show Abstract | Read more

Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SFMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional excretion of urate. Network analyses implicate the inhibins-activins signaling pathways and glucose metabolism in systemic urate control. New candidate genes for serum urate concentration highlight the importance of metabolic control of urate production and excretion, which may have implications for the treatment and prevention of gout.

Clarke R, Hopewell JC, Hill M, Farrall M, Watkins H. 2012. Independent Relevance of Cytokines for Risk of Coronary Heart Disease CIRCULATION, 126 (21),

Bissell MM, Pitcher A, Davis A, Francis JM, Prendergast B, Watkins H, Myerson SG, Neubauer S. 2012. Familial Bicuspid Aortic Valve Disease Frequently Shows Discordance of Leaflet Fusion Pattern and Extent: Insights from Cardiovascular Magnetic Resonance CIRCULATION, 126 (21),

Gertow K, Sennblad B, Strawbridge RJ, Ohrvik J, Zabaneh D, Shah S, Veglia F, Fava C, Kavousi M, McLachlan S et al. 2012. Identification of the BCAR1-CFDP1-TMEM170A locus as a determinant of carotid intima-media thickness and coronary artery disease risk. Circ Cardiovasc Genet, 5 (6), pp. 656-665. | Show Abstract | Read more

BACKGROUND: Carotid intima-media thickness (cIMT) is a widely accepted marker of subclinical atherosclerosis. To date, large-scale investigations of genetic determinants of cIMT are sparse. METHODS AND RESULTS: To identify cIMT-associated genes and genetic variants, a discovery analysis using the Illumina 200K CardioMetabochip was conducted in 3430 subjects with detailed ultrasonographic determinations of cIMT from the IMPROVE (Carotid Intima Media Thickness [IMT] and IMT-Progression as Predictors of Vascular Events in a High Risk European Population) study. Segment-specific IMT measurements of common carotid, bifurcation, and internal carotid arteries, and composite IMT variables considering the whole carotid tree (IMT(mean), IMT(max), and IMT(mean-max)), were analyzed. A replication stage investigating 42 single-nucleotide polymorphisms for association with common carotid IMT was undertaken in 5 independent European cohorts (total n=11,590). A locus on chromosome 16 (lead single-nucleotide polymorphism rs4888378, intronic in CFDP1) was associated with cIMT at significance levels passing multiple testing correction at both stages (array-wide significant discovery P=6.75 × 10(-7) for IMT(max); replication P=7.24×10(-6) for common cIMT; adjustments for sex, age, and population substructure where applicable; minor allele frequency 0.43 and 0.41, respectively). The protective minor allele was associated with lower carotid plaque score in a replication cohort (P=0.04, n=2120) and lower coronary artery disease risk in 2 case-control studies of subjects with European ancestry (odds ratio [95% confidence interval] 0.83 [0.77-0.90], P=6.53 × 10(-6), n=13 591; and 0.95 [0.92-0.98], P=1.83 × 10(-4), n=82 297, respectively). Queries of human biobank data sets revealed associations of rs4888378 with nearby gene expression in vascular tissues (n=126-138). CONCLUSIONS: This study identified rs4888378 in the BCAR1-CFDP1-TMEM170A locus as a novel genetic determinant of cIMT and coronary artery disease risk in individuals of European descent.

Dass S, Suttie JJ, Piechnik SK, Ferreira VM, Holloway CJ, Banerjee R, Mahmod M, Cochlin L, Karamitsos TD, Robson MD et al. 2012. Myocardial tissue characterization using magnetic resonance noncontrast t1 mapping in hypertrophic and dilated cardiomyopathy. Circ Cardiovasc Imaging, 5 (6), pp. 726-733. | Show Abstract | Read more

BACKGROUND: Noncontrast magnetic resonance T1 mapping reflects a composite of both intra- and extracellular signal. We hypothesized that noncontrast T1 mapping can characterize the myocardium beyond that achieved by the well-established late gadolinium enhancement (LGE) technique (which detects focal fibrosis) in both hypertrophic (HCM) and dilated (DCM) cardiomyopathy, by detecting both diffuse and focal fibrosis. METHODS AND RESULTS: Subjects underwent Cardiovascular Magnetic Resonance imaging at 3T (28 HCM, 18 DCM, and 12 normals). Matching short-axis slices were acquired for cine, T1 mapping, and LGE imaging (0.1 mmol/kg). Circumferential strain was measured in the midventricular slice, and (31)P magnetic resonance spectroscopy was acquired for the septum of the midventricular slice. Mean T1 relaxation time was increased in HCM and DCM (HCM 1209±28 ms, DCM 1225±42 ms, normal 1178±13 ms, P<0.05). There was a weak correlation between mean T1 and LGE (r=0.32, P<0.001). T1 values were higher in segments with LGE than in those without (HCM with LGE 1228±41 ms versus no LGE 1192±79 ms, P<0.01; DCM with LGE 1254±73 ms versus no LGE 1217±52 ms, P<0.01). However, in both HCM and DCM, even in segments unaffected by LGE, T1 values were significantly higher than normal (P<0.01). T1 values correlated with disease severity, being increased as wall thickness increased in HCM; conversely, in DCM, T1 values were highest in the thinnest myocardial segments. T1 values also correlated significantly with circumferential strain (r=0.42, P<0.01). Interestingly, this correlation remained statistically significant even for the slices without LGE (r=0.56, P=0.04). Finally, there was also a statistically significant negative correlation between T1 values and phosphocreatine/adenosine triphosphate ratios (r=-0.59, P<0.0001). CONCLUSIONS: In HCM and DCM, noncontrast T1 mapping detects underlying disease processes beyond those assessed by LGE in relatively low-risk individuals.

Huang J, Sabater-Lleal M, Asselbergs FW, Tregouet D, Shin SY, Ding J, Baumert J, Oudot-Mellakh T, Folkersen L, Johnson AD et al. 2012. Genome-wide association study for circulating levels of PAI-1 provides novel insights into its regulation. Blood, 120 (24), pp. 4873-4881. | Show Abstract | Read more

We conducted a genome-wide association study to identify novel associations between genetic variants and circulating plasminogen activator inhibitor-1 (PAI-1) concentration, and examined functional implications of variants and genes that were discovered. A discovery meta-analysis was performed in 19 599 subjects, followed by replication analysis of genome-wide significant (P < 5 × 10(-8)) single nucleotide polymorphisms (SNPs) in 10 796 independent samples. We further examined associations with type 2 diabetes and coronary artery disease, assessed the functional significance of the SNPs for gene expression in human tissues, and conducted RNA-silencing experiments for one novel association. We confirmed the association of the 4G/5G proxy SNP rs2227631 in the promoter region of SERPINE1 (7q22.1) and discovered genome-wide significant associations at 3 additional loci: chromosome 7q22.1 close to SERPINE1 (rs6976053, discovery P = 3.4 × 10(-10)); chromosome 11p15.2 within ARNTL (rs6486122, discovery P = 3.0 × 10(-8)); and chromosome 3p25.2 within PPARG (rs11128603, discovery P = 2.9 × 10(-8)). Replication was achieved for the 7q22.1 and 11p15.2 loci. There was nominal association with type 2 diabetes and coronary artery disease at ARNTL (P < .05). Functional studies identified MUC3 as a candidate gene for the second association signal on 7q22.1. In summary, SNPs in SERPINE1 and ARNTL and an SNP associated with the expression of MUC3 were robustly associated with circulating levels of PAI-1.

Yang J, Loos RJ, Powell JE, Medland SE, Speliotes EK, Chasman DI, Rose LM, Thorleifsson G, Steinthorsdottir V, Mägi R et al. 2012. FTO genotype is associated with phenotypic variability of body mass index. Nature, 490 (7419), pp. 267-272. | Show Abstract | Read more

There is evidence across several species for genetic control of phenotypic variation of complex traits, such that the variance among phenotypes is genotype dependent. Understanding genetic control of variability is important in evolutionary biology, agricultural selection programmes and human medicine, yet for complex traits, no individual genetic variants associated with variance, as opposed to the mean, have been identified. Here we perform a meta-analysis of genome-wide association studies of phenotypic variation using ∼170,000 samples on height and body mass index (BMI) in human populations. We report evidence that the single nucleotide polymorphism (SNP) rs7202116 at the FTO gene locus, which is known to be associated with obesity (as measured by mean BMI for each rs7202116 genotype), is also associated with phenotypic variability. We show that the results are not due to scale effects or other artefacts, and find no other experiment-wise significant evidence for effects on variability, either at loci other than FTO for BMI or at any locus for height. The difference in variance for BMI among individuals with opposite homozygous genotypes at the FTO locus is approximately 7%, corresponding to a difference of ∼0.5 kilograms in the standard deviation of weight. Our results indicate that genetic variants can be discovered that are associated with variability, and that between-person variability in obesity can partly be explained by the genotype at the FTO locus. The results are consistent with reported FTO by environment interactions for BMI, possibly mediated by DNA methylation. Our BMI results for other SNPs and our height results for all SNPs suggest that most genetic variants, including those that influence mean height or mean BMI, are not associated with phenotypic variance, or that their effects on variability are too small to detect even with samples sizes greater than 100,000.

Lygate CA, Bohl S, ten Hove M, Faller KM, Ostrowski PJ, Zervou S, Medway DJ, Aksentijevic D, Sebag-Montefiore L, Wallis J et al. 2012. Moderate elevation of intracellular creatine by targeting the creatine transporter protects mice from acute myocardial infarction. Cardiovasc Res, 96 (3), pp. 466-475. | Show Abstract | Read more

AIMS: Increasing energy storage capacity by elevating creatine and phosphocreatine (PCr) levels to increase ATP availability is an attractive concept for protecting against ischaemia and heart failure. However, testing this hypothesis has not been possible since oral creatine supplementation is ineffectual at elevating myocardial creatine levels. We therefore used mice overexpressing creatine transporter in the heart (CrT-OE) to test for the first time whether elevated creatine is beneficial in clinically relevant disease models of heart failure and ischaemia/reperfusion (I/R) injury. METHODS AND RESULTS: CrT-OE mice were selected for left ventricular (LV) creatine 20-100% above wild-type values and subjected to acute and chronic coronary artery ligation. Increasing myocardial creatine up to 100% was not detrimental even in ageing CrT-OE. In chronic heart failure, creatine elevation was neither beneficial nor detrimental, with no effect on survival, LV remodelling or dysfunction. However, CrT-OE hearts were protected against I/R injury in vivo in a dose-dependent manner (average 27% less myocardial necrosis) and exhibited greatly improved functional recovery following ex vivo I/R (59% of baseline vs. 29%). Mechanisms contributing to ischaemic protection in CrT-OE hearts include elevated PCr and glycogen levels and improved energy reserve. Furthermore, creatine loading in HL-1 cells did not alter antioxidant defences, but delayed mitochondrial permeability transition pore opening in response to oxidative stress, suggesting an additional mechanism to prevent reperfusion injury. CONCLUSION: Elevation of myocardial creatine by 20-100% reduced myocardial stunning and I/R injury via pleiotropic mechanisms, suggesting CrT activation as a novel, potentially translatable target for cardiac protection from ischaemia.

Scott RA, Lagou V, Welch RP, Wheeler E, Montasser ME, Luan J, Mägi R, Strawbridge RJ, Rehnberg E, Gustafsson S et al. 2012. Large-scale association analyses identify new loci influencing glycemic traits and provide insight into the underlying biological pathways. Nat Genet, 44 (9), pp. 991-1005. | Show Abstract | Read more

Through genome-wide association meta-analyses of up to 133,010 individuals of European ancestry without diabetes, including individuals newly genotyped using the Metabochip, we have increased the number of confirmed loci influencing glycemic traits to 53, of which 33 also increase type 2 diabetes risk (q < 0.05). Loci influencing fasting insulin concentration showed association with lipid levels and fat distribution, suggesting impact on insulin resistance. Gene-based analyses identified further biologically plausible loci, suggesting that additional loci beyond those reaching genome-wide significance are likely to represent real associations. This conclusion is supported by an excess of directionally consistent and nominally significant signals between discovery and follow-up studies. Functional analysis of these newly discovered loci will further improve our understanding of glycemic control.

Voight BF, Peloso GM, Orho-Melander M, Frikke-Schmidt R, Barbalic M, Jensen MK, Hindy G, Hólm H, Ding EL, Johnson T et al. 2012. Erratum: Plasma HDL cholesterol and risk of myocardial infarction: A mendelian randomisation study (The Lancet (2012) DOI:10.1016/S0140-6736(12) 60312-2) The Lancet, 380 (9841), pp. 564.

Pinter K, Grignani RT, Czibik G, Farza H, Watkins H, Redwood C. 2012. Embryonic expression of AMPK γ subunits and the identification of a novel γ2 transcript variant in adult heart. J Mol Cell Cardiol, 53 (3), pp. 342-349. | Show Abstract | Read more

AMP-activated protein kinase (AMPK), the key sensor and regulator of cellular energy status, is a heterotrimeric enzyme with multiple isoforms for each subunit (α1/α 2; β1/β2; γ1/γ2/γ3). Mutations in PRKAG2, which encodes the γ2 regulatory subunit, cause a cardiomyopathy characterized by hypertrophy and conduction abnormalities. The two reported PRKAG2 transcript variants, γ2-short and γ2-long (encoding 328 and 569 amino acids respectively), are both widely expressed in adult tissues. We show that both γ2 variants are also expressed during cardiogenesis in mouse embryos; expression of the γ3 isoform was also detected unexpectedly at this stage. As neither γ2 transcript is cardiac specific nor differentially expressed during embryogenesis, it is paradoxical that the disease is largely restricted to the heart. However, a recently annotated γ2 transcript, termed γ2-3B as transcription starts at an alternative exon 3b, has been identified; it is spliced in-frame to exon 4 thus generating a protein of 443 residues in mouse with the first 32 residues being unique. It is increasingly expressed in the developing mouse heart and quantitative PCR analysis established that γ2-3B is the major PRKAG2 transcript (~60%) in human heart. Antibody against the novel N-terminal sequence showed that γ2-3B is predominantly expressed in the heart where it is the most abundant γ2 protein. The abundance of γ2-3B and its tissue specificity indicate that γ2-3B may have non-redundant role in the heart and hence mediate the predominantly cardiac phenotype caused by PRKAG2 mutations.

Voight BF, Peloso GM, Orho-Melander M, Frikke-Schmidt R, Barbalic M, Jensen MK, Hindy G, Hólm H, Ding EL, Johnson T et al. 2012. Plasma HDL cholesterol and risk of myocardial infarction: a mendelian randomisation study. Lancet, 380 (9841), pp. 572-580. | Show Abstract | Read more

BACKGROUND: High plasma HDL cholesterol is associated with reduced risk of myocardial infarction, but whether this association is causal is unclear. Exploiting the fact that genotypes are randomly assigned at meiosis, are independent of non-genetic confounding, and are unmodified by disease processes, mendelian randomisation can be used to test the hypothesis that the association of a plasma biomarker with disease is causal. METHODS: We performed two mendelian randomisation analyses. First, we used as an instrument a single nucleotide polymorphism (SNP) in the endothelial lipase gene (LIPG Asn396Ser) and tested this SNP in 20 studies (20,913 myocardial infarction cases, 95,407 controls). Second, we used as an instrument a genetic score consisting of 14 common SNPs that exclusively associate with HDL cholesterol and tested this score in up to 12,482 cases of myocardial infarction and 41,331 controls. As a positive control, we also tested a genetic score of 13 common SNPs exclusively associated with LDL cholesterol. FINDINGS: Carriers of the LIPG 396Ser allele (2·6% frequency) had higher HDL cholesterol (0·14 mmol/L higher, p=8×10(-13)) but similar levels of other lipid and non-lipid risk factors for myocardial infarction compared with non-carriers. This difference in HDL cholesterol is expected to decrease risk of myocardial infarction by 13% (odds ratio [OR] 0·87, 95% CI 0·84-0·91). However, we noted that the 396Ser allele was not associated with risk of myocardial infarction (OR 0·99, 95% CI 0·88-1·11, p=0·85). From observational epidemiology, an increase of 1 SD in HDL cholesterol was associated with reduced risk of myocardial infarction (OR 0·62, 95% CI 0·58-0·66). However, a 1 SD increase in HDL cholesterol due to genetic score was not associated with risk of myocardial infarction (OR 0·93, 95% CI 0·68-1·26, p=0·63). For LDL cholesterol, the estimate from observational epidemiology (a 1 SD increase in LDL cholesterol associated with OR 1·54, 95% CI 1·45-1·63) was concordant with that from genetic score (OR 2·13, 95% CI 1·69-2·69, p=2×10(-10)). INTERPRETATION: Some genetic mechanisms that raise plasma HDL cholesterol do not seem to lower risk of myocardial infarction. These data challenge the concept that raising of plasma HDL cholesterol will uniformly translate into reductions in risk of myocardial infarction. FUNDING: US National Institutes of Health, The Wellcome Trust, European Union, British Heart Foundation, and the German Federal Ministry of Education and Research.

Dodd MS, Ball DR, Schroeder MA, Le Page LM, Atherton HJ, Heather LC, Seymour AM, Ashrafian H, Watkins H, Clarke K, Tyler DJ. 2012. In vivo alterations in cardiac metabolism and function in the spontaneously hypertensive rat heart. Cardiovasc Res, 95 (1), pp. 69-76. | Show Abstract | Read more

AIMS: The aim of this work was to use hyperpolarized carbon-13 ((13)C) magnetic resonance (MR) spectroscopy and cine MR imaging (MRI) to assess in vivo cardiac metabolism and function in the 15-week-old spontaneously hypertensive rat (SHR) heart. At this time point, the SHR displays hypertension and concentric hypertrophy. One of the cellular adaptations to hypertrophy is a reduction in β-oxidation, and it has previously been shown that in response to hypertrophy the SHR heart switches to a glycolytic/glucose-oxidative phenotype. METHODS AND RESULTS: Cine-MRI (magnetic resonance imaging) was used to assess cardiac function and degree of cardiac hypertrophy. Wistar rats were used as controls. SHRs displayed functional changes in stroke volume, heart rate, and late peak-diastolic filling alongside significant hypertrophy (a 56% increase in left ventricular mass). Using hyperpolarized [1-(13)C] and [2-(13)C]pyruvate, an 85% increase in (13)C label flux through pyruvate dehydrogenase (PDH) was seen in the SHR heart and (13)C label incorporation into citrate, acetylcarnitine, and glutamate pools was elevated in proportion to the increase in PDH flux. These findings were confirmed using biochemical analysis of PDH activity and protein expression of PDH regulatory enzymes. CONCLUSIONS: Functional and structural alterations in the SHR heart are consistent with the hypertrophied phenotype. Our in vivo work indicates a preference for glucose metabolism in the SHR heart, a move away from predominantly fatty acid oxidative metabolism. Interestingly, (13)C label flux into lactate was unchanged, indicating no switch to an anaerobic glycolytic phenotype, but rather an increased reliance on glucose oxidation in the SHR heart.

Manning AK, Hivert MF, Scott RA, Grimsby JL, Bouatia-Naji N, Chen H, Rybin D, Liu CT, Bielak LF, Prokopenko I et al. 2012. A genome-wide approach accounting for body mass index identifies genetic variants influencing fasting glycemic traits and insulin resistance. Nat Genet, 44 (6), pp. 659-669. | Show Abstract | Read more

Recent genome-wide association studies have described many loci implicated in type 2 diabetes (T2D) pathophysiology and β-cell dysfunction but have contributed little to the understanding of the genetic basis of insulin resistance. We hypothesized that genes implicated in insulin resistance pathways might be uncovered by accounting for differences in body mass index (BMI) and potential interactions between BMI and genetic variants. We applied a joint meta-analysis approach to test associations with fasting insulin and glucose on a genome-wide scale. We present six previously unknown loci associated with fasting insulin at P < 5 × 10(-8) in combined discovery and follow-up analyses of 52 studies comprising up to 96,496 non-diabetic individuals. Risk variants were associated with higher triglyceride and lower high-density lipoprotein (HDL) cholesterol levels, suggesting a role for these loci in insulin resistance pathways. The discovery of these loci will aid further characterization of the role of insulin resistance in T2D pathophysiology.

Kowalczyk MS, Hughes JR, Babbs C, Sanchez-Pulido L, Szumska D, Sharpe JA, Sloane-Stanley JA, Morriss-Kay GM, Smoot LB, Roberts AE et al. 2012. Nprl3 is required for normal development of the cardiovascular system. Mamm Genome, 23 (7-8), pp. 404-415. | Show Abstract | Read more

C16orf35 is a conserved and widely expressed gene lying adjacent to the human α-globin cluster in all vertebrate species. In-depth sequence analysis shows that C16orf35 (now called NPRL3) is an orthologue of the yeast gene Npr3 (nitrogen permease regulator 3) and, furthermore, is a paralogue of its protein partner Npr2. The yeast Npr2/3 dimeric protein complex senses amino acid starvation and appropriately adjusts cell metabolism via the TOR pathway. Here we have analysed a mouse model in which expression of Nprl3 has been abolished using homologous recombination. The predominant effect on RNA expression appears to involve genes that regulate protein synthesis and cell cycle, consistent with perturbation of the mTOR pathway. Embryos homozygous for this mutation die towards the end of gestation with a range of cardiovascular defects, including outflow tract abnormalities and ventriculoseptal defects consistent with previous observations, showing that perturbation of the mTOR pathway may affect development of the myocardium. NPRL3 is a candidate gene for harbouring mutations in individuals with developmental abnormalities of the cardiovascular system.

IL6R Genetics Consortium Emerging Risk Factors Collaboration, Sarwar N, Butterworth AS, Freitag DF, Gregson J, Willeit P, Gorman DN, Gao P, Saleheen D, Rendon A et al. 2012. Interleukin-6 receptor pathways in coronary heart disease: a collaborative meta-analysis of 82 studies. Lancet, 379 (9822), pp. 1205-1213. | Show Abstract | Read more

BACKGROUND: Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling. METHODS: In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125,222 participants. We also compared the frequency of Asp358Ala in 51,441 patients with coronary heart disease and in 136,226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6. FINDINGS: The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele ≥0·04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34·3% (95% CI 30·4-38·2) and of interleukin 6 by 14·6% (10·7-18·4), and mean concentration of C-reactive protein was reduced by 7·5% (5·9-9·1) and of fibrinogen by 1·0% (0·7-1·3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3·4% (1·8-5·0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes. INTERPRETATION: Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease. FUNDING: British Heart Foundation; UK Medical Research Council; UK National Institute of Health Research, Cambridge Biomedical Research Centre; BUPA Foundation.

Ashrafian H, Czibik G, Bellahcene M, Aksentijević D, Smith AC, Mitchell SJ, Dodd MS, Kirwan J, Byrne JJ, Ludwig C et al. 2012. Fumarate is cardioprotective via activation of the Nrf2 antioxidant pathway. Cell Metab, 15 (3), pp. 361-371. | Show Abstract | Read more

The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents.

Pinter K, Jefferson A, Czibik G, Watkins H, Redwood C. 2012. Subunit composition of AMPK trimers present in the cytokinetic apparatus: Implications for drug target identification. Cell Cycle, 11 (5), pp. 917-921. | Show Abstract | Read more

AMP-activated protein kinase has been shown to be a key regulator of energy homeostasis; it has also been identified as a tumor suppressor and is required for correct cell division and chromosome segregation during mitosis. The enzyme is a heterotrimer, with each subunit having more than one isoform, each encoded by a separate gene (two α, two β and three γ isoforms). In human endothelial cells, the activated kinase subunit of AMPK in the cytokinetic apparatus is α2, the minority α subunit, which co-localizes with β2 and γ2. This is the first demonstration of a trimeric complex of AMPK containing the γ2 regulatory subunit becoming selectively activated and being linked to mitotic processes. We also show that α1 and γ1, the predominant AMPK subunits, are almost exclusively localized in the cytoskeleton, while α2 and γ2 are present in all subcellular fractions, including the nuclei. These data suggest that pharmacological interventions targeted to specific AMPK subunit isoforms have the potential to modify selective functions of AMPK.

Saxena R, Elbers CC, Guo Y, Peter I, Gaunt TR, Mega JL, Lanktree MB, Tare A, Castillo BA, Li YR et al. 2012. Large-scale gene-centric meta-analysis across 39 studies identifies type 2 diabetes loci. Am J Hum Genet, 90 (3), pp. 410-425. | Show Abstract | Read more

To identify genetic factors contributing to type 2 diabetes (T2D), we performed large-scale meta-analyses by using a custom ∼50,000 SNP genotyping array (the ITMAT-Broad-CARe array) with ∼2000 candidate genes in 39 multiethnic population-based studies, case-control studies, and clinical trials totaling 17,418 cases and 70,298 controls. First, meta-analysis of 25 studies comprising 14,073 cases and 57,489 controls of European descent confirmed eight established T2D loci at genome-wide significance. In silico follow-up analysis of putative association signals found in independent genome-wide association studies (including 8,130 cases and 38,987 controls) performed by the DIAGRAM consortium identified a T2D locus at genome-wide significance (GATAD2A/CILP2/PBX4; p = 5.7 × 10(-9)) and two loci exceeding study-wide significance (SREBF1, and TH/INS; p < 2.4 × 10(-6)). Second, meta-analyses of 1,986 cases and 7,695 controls from eight African-American studies identified study-wide-significant (p = 2.4 × 10(-7)) variants in HMGA2 and replicated variants in TCF7L2 (p = 5.1 × 10(-15)). Third, conditional analysis revealed multiple known and novel independent signals within five T2D-associated genes in samples of European ancestry and within HMGA2 in African-American samples. Fourth, a multiethnic meta-analysis of all 39 studies identified T2D-associated variants in BCL2 (p = 2.1 × 10(-8)). Finally, a composite genetic score of SNPs from new and established T2D signals was significantly associated with increased risk of diabetes in African-American, Hispanic, and Asian populations. In summary, large-scale meta-analysis involving a dense gene-centric approach has uncovered additional loci and variants that contribute to T2D risk and suggests substantial overlap of T2D association signals across multiple ethnic groups.

Clarke R, Bennett DA, Parish S, Verhoef P, Dötsch-Klerk M, Lathrop M, Xu P, Nordestgaard BG, Holm H, Hopewell JC et al. 2012. Homocysteine and coronary heart disease: meta-analysis of MTHFR case-control studies, avoiding publication bias. PLoS Med, 9 (2), pp. e1001177. | Show Abstract | Read more

BACKGROUND: Moderately elevated blood levels of homocysteine are weakly correlated with coronary heart disease (CHD) risk, but causality remains uncertain. When folate levels are low, the TT genotype of the common C677T polymorphism (rs1801133) of the methylene tetrahydrofolate reductase gene (MTHFR) appreciably increases homocysteine levels, so "Mendelian randomization" studies using this variant as an instrumental variable could help test causality. METHODS AND FINDINGS: Nineteen unpublished datasets were obtained (total 48,175 CHD cases and 67,961 controls) in which multiple genetic variants had been measured, including MTHFR C677T. These datasets did not include measurements of blood homocysteine, but homocysteine levels would be expected to be about 20% higher with TT than with CC genotype in the populations studied. In meta-analyses of these unpublished datasets, the case-control CHD odds ratio (OR) and 95% CI comparing TT versus CC homozygotes was 1.02 (0.98-1.07; p = 0.28) overall, and 1.01 (0.95-1.07) in unsupplemented low-folate populations. By contrast, in a slightly updated meta-analysis of the 86 published studies (28,617 CHD cases and 41,857 controls), the OR was 1.15 (1.09-1.21), significantly discrepant (p = 0.001) with the OR in the unpublished datasets. Within the meta-analysis of published studies, the OR was 1.12 (1.04-1.21) in the 14 larger studies (those with variance of log OR<0.05; total 13,119 cases) and 1.18 (1.09-1.28) in the 72 smaller ones (total 15,498 cases). CONCLUSIONS: The CI for the overall result from large unpublished datasets shows lifelong moderate homocysteine elevation has little or no effect on CHD. The discrepant overall result from previously published studies reflects publication bias or methodological problems.

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Manning AK, Hivert MF, Scott RA, Grimsby JL, Bouatia-Naji N, Chen H, Rybin D, Liu CT, Bielak LF, Prokopenko I et al. 2012. A genome-wide approach accounting for body mass index identifies genetic variants influencing fasting glycemic traits and insulin resistance Nature Genetics, 44 (6), pp. 659-669. | Show Abstract | Read more

Recent genome-wide association studies have described many loci implicated in type 2 diabetes (T2D) pathophysiology and β-cell dysfunction but have contributed little to the understanding of the genetic basis of insulin resistance. We hypothesized that genes implicated in insulin resistance pathways might be uncovered by accounting for differences in body mass index (BMI) and potential interactions between BMI and genetic variants. We applied a joint meta-analysis approach to test associations with fasting insulin and glucose on a genome-wide scale. We present six previously unknown loci associated with fasting insulin at P < 5 × 10 -8 in combined discovery and follow-up analyses of 52 studies comprising up to 96,496 non-diabetic individuals. Risk variants were associated with higher triglyceride and lower high-density lipoprotein (HDL) cholesterol levels, suggesting a role for these loci in insulin resistance pathways. The discovery of these loci will aid further characterization of the role of insulin resistance in T2D pathophysiology. © 2012 Nature America, Inc. All rights reserved.

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Oliveira SM, Zhang Y-H, Solis RS, Isackson H, Bellahcene M, Yavari A, Pinter K, Davies JK, Ge Y, Ashrafian H et al. 2012. AMP-Activated Protein Kinase Phosphorylates Cardiac Troponin I and Alters Contractility of Murine Ventricular Myocytes CIRCULATION RESEARCH, 110 (9), pp. 1192-1201. | Read more

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Oliveira SM, Zhang YH, Solis RS, Isackson H, Bellahcene M, Yavari A, Pinter K, Davies JK, Ge Y, Ashrafian H et al. 2012. AMP-Activated protein kinase phosphorylates cardiac troponin i and alters contractility of murine ventricular myocytes Circulation Research, 110 (9), pp. 1192-1201. | Show Abstract | Read more

Rationale: AMP-activated protein kinase (AMPK) is an important regulator of energy balance and signaling in the heart. Mutations affecting the regulatory γ2 subunit have been shown to cause an essentially cardiac-restricted phenotype of hypertrophy and conduction disease, suggesting a specific role for this subunit in the heart. Objective: The γ isoforms are highly conserved at their C-termini but have unique N-terminal sequences, and we hypothesized that the N-terminus of γ2 may be involved in conferring substrate specificity or in determining intracellular localization. Methods and Results: A yeast 2-hybrid screen of a human heart cDNA library using the N-terminal 273 residues of γ2 as bait identified cardiac troponin I (cTnI) as a putative interactor. In vitro studies showed that cTnI is a good AMPK substrate and that Ser150 is the principal residue phosphorylated. Furthermore, on AMPK activation during ischemia, Ser150 is phosphorylated in whole hearts. Using phosphomimics, measurements of actomyosin ATPase in vitro and force generation in demembraneated trabeculae showed that modification at Ser150 resulted in increased Ca sensitivity of contractile regulation. Treatment of cardiomyocytes with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) resulted in increased myocyte contractility without changing the amplitude of Ca transient and prolonged relaxation despite shortening the time constant of Ca transient decay (tau). Compound C prevented the effect of AICAR on myocyte function. These results suggest that AMPK activation increases myocyte contraction and prolongs relaxation by increasing myofilament Ca sensitivity. Conclusions: We conclude that cTnI phosphorylation by AMPK may represent a novel mechanism of regulation of cardiac function. © 2012 American Heart Association, Inc.

Helgadottir A, Gretarsdottir S, Thorleifsson G, Holm H, Patel RS, Gudnason T, Jones GT, van Rij AM, Eapen DJ, Baas AF et al. 2012. Apolipoprotein(a) genetic sequence variants associated with systemic atherosclerosis and coronary atherosclerotic burden but not with venous thromboembolism. J Am Coll Cardiol, 60 (8), pp. 722-729. | Show Abstract | Read more

OBJECTIVES: The purpose of this study is investigate the effects of variants in the apolipoprotein(a) gene (LPA) on vascular diseases with different atherosclerotic and thrombotic components. BACKGROUND: It is unclear whether the LPA variants rs10455872 and rs3798220, which correlate with lipoprotein(a) levels and coronary artery disease (CAD), confer susceptibility predominantly via atherosclerosis or thrombosis. METHODS: The 2 LPA variants were combined and examined as LPA scores for the association with ischemic stroke (and TOAST [Trial of Org 10172 in Acute Stroke Treatment] subtypes) (effective sample size [n(e)] = 9,396); peripheral arterial disease (n(e) = 5,215); abdominal aortic aneurysm (n(e) = 4,572); venous thromboembolism (n(e) = 4,607); intracranial aneurysm (n(e) = 1,328); CAD (n(e) = 12,716), carotid intima-media thickness (n = 3,714), and angiographic CAD severity (n = 5,588). RESULTS: LPA score was associated with ischemic stroke subtype large artery atherosclerosis (odds ratio [OR]: 1.27; p = 6.7 × 10(-4)), peripheral artery disease (OR: 1.47; p = 2.9 × 10(-14)), and abdominal aortic aneurysm (OR: 1.23; p = 6.0 × 10(-5)), but not with the ischemic stroke subtypes cardioembolism (OR: 1.03; p = 0.69) or small vessel disease (OR: 1.06; p = 0.52). Although the LPA variants were not associated with carotid intima-media thickness, they were associated with the number of obstructed coronary vessels (p = 4.8 × 10(-12)). Furthermore, CAD cases carrying LPA risk variants had increased susceptibility to atherosclerotic manifestations outside of the coronary tree (OR: 1.26; p = 0.0010) and had earlier onset of CAD (-1.58 years/allele; p = 8.2 × 10(-8)) than CAD cases not carrying the risk variants. There was no association of LPA score with venous thromboembolism (OR: 0.97; p = 0.63) or intracranial aneurysm (OR: 0.85; p = 0.15). CONCLUSIONS: LPA sequence variants were associated with atherosclerotic burden, but not with primarily thrombotic phenotypes.

Chen CM, Bentham J, Cosgrove C, Braganca J, Cuenda A, Bamforth SD, Schneider JE, Watkins H, Keavney B, Davies B, Bhattacharya S. 2012. Functional significance of SRJ domain mutations in CITED2. PLoS One, 7 (10), pp. e46256. | Show Abstract | Read more

CITED2 is a transcriptional co-activator with 3 conserved domains shared with other CITED family members and a unique Serine-Glycine Rich Junction (SRJ) that is highly conserved in placental mammals. Loss of Cited2 in mice results in cardiac and aortic arch malformations, adrenal agenesis, neural tube and placental defects, and partially penetrant defects in left-right patterning. By screening 1126 sporadic congenital heart disease (CHD) cases and 1227 controls, we identified 19 variants, including 5 unique non-synonymous sequence variations (N62S, R92G, T166N, G180-A187del and A187T) in patients. Many of the CHD-specific variants identified in this and previous studies cluster in the SRJ domain. Transient transfection experiments show that T166N mutation impairs TFAP2 co-activation function and ES cell proliferation. We find that CITED2 is phosphorylated by MAPK1 in vitro at T166, and that MAPK1 activation enhances the coactivation function of CITED2 but not of CITED2-T166N. In order to investigate the functional significance in vivo, we generated a T166N mutation of mouse Cited2. We also used PhiC31 integrase-mediated cassette exchange to generate a Cited2 knock-in allele replacing the mouse Cited2 coding sequence with human CITED2 and with a mutant form deleting the entire SRJ domain. Mouse embryos expressing only CITED2-T166N or CITED2-SRJ-deleted alleles surprisingly show no morphological abnormalities, and mice are viable and fertile. These results indicate that the SRJ domain is dispensable for these functions of CITED2 in mice and that mutations clustering in the SRJ region are unlikely to be the sole cause of the malformations observed in patients with sporadic CHD. Our results also suggest that coding sequence mutations observed in case-control studies need validation using in vivo models and that predictions based on structural conservation and in vitro functional assays, or even in vivo global loss of function models, may be insufficient.

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Scott RA, Lagou V, Welch RP, Wheeler E, Montasser ME, Luan J, MäGi R, Strawbridge RJ, Rehnberg E, Gustafsson S et al. 2012. Large-scale association analyses identify new loci influencing glycemic traits and provide insight into the underlying biological pathways Nature Genetics, 44 (9), pp. 991-1005. | Show Abstract | Read more

Through genome-wide association meta-analyses of up to 133,010 individuals of European ancestry without diabetes, including individuals newly genotyped using the Metabochip, we have increased the number of confirmed loci influencing glycemic traits to 53, of which 33 also increase type 2 diabetes risk (q < 0.05). Loci influencing fasting insulin concentration showed association with lipid levels and fat distribution, suggesting impact on insulin resistance. Gene-based analyses identified further biologically plausible loci, suggesting that additional loci beyond those reaching genome-wide significance are likely to represent real associations. This conclusion is supported by an excess of directionally consistent and nominally significant signals between discovery and follow-up studies. Functional analysis of these newly discovered loci will further improve our understanding of glycemic control. © 2012 Nature America, Inc. All rights reserved.

Deloukas P, Kanoni S, Willenborg C, Farrall M, Assimes TL, Thompson JR, Ingelsson E, Saleheen D, Erdmann J, Goldstein BA et al. 2012. Large-scale association analysis identifies new risk loci for coronary artery disease Nature Genetics,

Asselbergs FW, Guo Y, van Iperen EP, Sivapalaratnam S, Tragante V, Lanktree MB, Lange LA, Almoguera B, Appelman YE, Barnard J et al. 2012. Large-scale gene-centric meta-analysis across 32 studies identifies multiple lipid loci. Am J Hum Genet, 91 (5), pp. 823-838. | Show Abstract | Read more

Genome-wide association studies (GWASs) have identified many SNPs underlying variations in plasma-lipid levels. We explore whether additional loci associated with plasma-lipid phenotypes, such as high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglycerides (TGs), can be identified by a dense gene-centric approach. Our meta-analysis of 32 studies in 66,240 individuals of European ancestry was based on the custom ∼50,000 SNP genotyping array (the ITMAT-Broad-CARe array) covering ∼2,000 candidate genes. SNP-lipid associations were replicated either in a cohort comprising an additional 24,736 samples or within the Global Lipid Genetic Consortium. We identified four, six, ten, and four unreported SNPs in established lipid genes for HDL-C, LDL-C, TC, and TGs, respectively. We also identified several lipid-related SNPs in previously unreported genes: DGAT2, HCAR2, GPIHBP1, PPARG, and FTO for HDL-C; SOCS3, APOH, SPTY2D1, BRCA2, and VLDLR for LDL-C; SOCS3, UGT1A1, BRCA2, UBE3B, FCGR2A, CHUK, and INSIG2 for TC; and SERPINF2, C4B, GCK, GATA4, INSR, and LPAL2 for TGs. The proportion of explained phenotypic variance in the subset of studies providing individual-level data was 9.9% for HDL-C, 9.5% for LDL-C, 10.3% for TC, and 8.0% for TGs. This large meta-analysis of lipid phenotypes with the use of a dense gene-centric approach identified multiple SNPs not previously described in established lipid genes and several previously unknown loci. The explained phenotypic variance from this approach was comparable to that from a meta-analysis of GWAS data, suggesting that a focused genotyping approach can further increase the understanding of heritability of plasma lipids.

Saxena R, Elbers CC, Guo Y, Peter I, Gaunt TR, Mega JL, Lanktree MB, Tare A, Castillo BA, Li YR et al. 2012. Large-scale gene-centric meta-analysis across 39 studies identifies type 2 diabetes loci American Journal of Human Genetics, 90 (3), pp. 410-425.

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Saxena R, Elbers CC, Guo Y, Peter I, Gaunt TR, Mega JL, Lanktree MB, Tare A, Castillo BA, Li YR et al. 2012. Large-scale gene-centric meta-analysis across 39 studies identifies type 2 diabetes loci American Journal of Human Genetics, 90 (3), pp. 410-425. | Show Abstract | Read more

To identify genetic factors contributing to type 2 diabetes (T2D), we performed large-scale meta-analyses by using a custom ∼50,000 SNP genotyping array (the ITMAT-Broad-CARe array) with ∼2000 candidate genes in 39 multiethnic population-based studies, case-control studies, and clinical trials totaling 17,418 cases and 70,298 controls. First, meta-analysis of 25 studies comprising 14,073 cases and 57,489 controls of European descent confirmed eight established T2D loci at genome-wide significance. In silico follow-up analysis of putative association signals found in independent genome-wide association studies (including 8,130 cases and 38,987 controls) performed by the DIAGRAM consortium identified a T2D locus at genome-wide significance (GATAD2A/CILP2/PBX4; p = 5.7 × 10 -9) and two loci exceeding study-wide significance (SREBF1, and TH/INS; p < 2.4 × 10 -6). Second, meta-analyses of 1,986 cases and 7,695 controls from eight African-American studies identified study-wide-significant (p = 2.4 × 10 -7) variants in HMGA2 and replicated variants in TCF7L2 (p = 5.1 × 10 -15). Third, conditional analysis revealed multiple known and novel independent signals within five T2D-associated genes in samples of European ancestry and within HMGA2 in African-American samples. Fourth, a multiethnic meta-analysis of all 39 studies identified T2D-associated variants in BCL2 (p = 2.1 × 10 -8). Finally, a composite genetic score of SNPs from new and established T2D signals was significantly associated with increased risk of diabetes in African-American, Hispanic, and Asian populations. In summary, large-scale meta-analysis involving a dense gene-centric approach has uncovered additional loci and variants that contribute to T2D risk and suggests substantial overlap of T2D association signals across multiple ethnic groups. © 2012 The American Society of Human Genetics.

Salari K, Watkins H, Ashley EA. 2012. Personalized medicine: hope or hype? Eur Heart J, 33 (13), pp. 1564-1570. | Show Abstract | Read more

Medicine has always been personalized. For years, physicians have incorporated environmental, behavioural, and genetic factors that affect disease and drug response into patient management decisions. However, until recently, the 'genetic' data took the form of family history and self-reported race/ethnicity. As genome sequencing declines in cost, the availability of specific genomic information will no longer be limiting. Rather, our ability to parse these data and our decision whether to use it will become primary. As our understanding of genetic association with drug responses and diseases continues to improve, clinically useful genetic tests may emerge to improve upon our previous methods of assessing genetic risks. Indeed, genetic tests for monogenic disorders have already proven useful. Such changes may usher in a new era of personalized medicine. In this review, we will discuss the utility and limitations of personal genomic data in three domains: pharmacogenomics, assessment of genetic predispositions for common diseases, and identification of rare disease-causing genetic variants.

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Voight BF, Peloso GM, Orho-Melander M, Frikke-Schmidt R, Barbalic M, Jensen MK, Hindy G, Hólm H, Ding EL, Johnson T et al. 2012. Plasma HDL cholesterol and risk of myocardial infarction: A mendelian randomisation study The Lancet, 380 (9841), pp. 572-580. | Show Abstract | Read more

Background High plasma HDL cholesterol is associated with reduced risk of myocardial infarction, but whether this association is causal is unclear. Exploiting the fact that genotypes are randomly assigned at meiosis, are independent of non-genetic confounding, and are unmodified by disease processes, mendelian random isation can be used to test the hypothesis that the association of a plasma biomarker with disease is causal. Methods We performed two mendelian randomisation analyses. First, we used as an instrument a single nucleotide polymorphism (SNP) in the endothelial lipase gene (LIPG Asn396Ser) and tested this SNP in 20 studies (20 913 myocardial infarction cases, 95 407 controls). Second, we used as an instrument a genetic score consisting of 14 common SNPs that exclusively associate with HDL cholesterol and tested this score in up to 12 482 cases of myocardial infarction and 41 331 controls. As a positive control, we also tested a genetic score of 13 common SNPs exclusively associated with LDL cholesterol. Findings Carriers of the LIPG 396Ser allele (2·6% frequency) had higher HDL cholesterol (0·14 mmol/L higher p=8×10-13) but similar levels of other lipid and non-lipid risk factors for myocardial infarction compared with noncarriers. This difference in HDL cholesterol is expected to decrease risk of myocardial infarction by 13% (odds ratio [OR] 0·87, 95% CI 0·84-0·91). However, we noted that the 396Ser allele was not associated with risk of myocardial infarction (OR 0·99, 95% CI 0·88-1·11, p=0·85). From observational epidemiology, an increase of 1 SD in HDL cholesterol was associated with reduced risk of myocardial infarction (OR 0·62, 95% CI 0·58-0·66). However, a 1 SD increase in HDL cholesterol due to genetic score was not associated with risk of myocardial infarction (OR 0·93 95% CI 0·68-1·26, p=0·63). For LDL cholesterol, the estimate from observational epidemiology (a 1 SD increase in LDL cholesterol associated with OR 1·54, 95% CI 1·45-1·63) was concordant with that from genetic score (OR 2·13 95% CI 1·69-2·69, p=2×10 -10). Interpretation Some genetic mechanisms that raise plasma HDL cholesterol do not seem to lower risk of myocardial infarction. These data challenge the concept that raising of plasma HDL cholesterol will uniformly translate into reductions in risk of myocardial infarction.

Dastani Z, Hivert MF, Timpson N, Perry JR, Yuan X, Scott RA, Henneman P, Heid IM, Kizer JR, Lyytikäinen LP et al. 2012. Novel loci for adiponectin levels and their influence on type 2 diabetes and metabolic traits: a multi-ethnic meta-analysis of 45,891 individuals. PLoS Genet, 8 (3), pp. e1002607. | Show Abstract | Read more

Circulating levels of adiponectin, a hormone produced predominantly by adipocytes, are highly heritable and are inversely associated with type 2 diabetes mellitus (T2D) and other metabolic traits. We conducted a meta-analysis of genome-wide association studies in 39,883 individuals of European ancestry to identify genes associated with metabolic disease. We identified 8 novel loci associated with adiponectin levels and confirmed 2 previously reported loci (P = 4.5×10(-8)-1.2×10(-43)). Using a novel method to combine data across ethnicities (N = 4,232 African Americans, N = 1,776 Asians, and N = 29,347 Europeans), we identified two additional novel loci. Expression analyses of 436 human adipocyte samples revealed that mRNA levels of 18 genes at candidate regions were associated with adiponectin concentrations after accounting for multiple testing (p<3×10(-4)). We next developed a multi-SNP genotypic risk score to test the association of adiponectin decreasing risk alleles on metabolic traits and diseases using consortia-level meta-analytic data. This risk score was associated with increased risk of T2D (p = 4.3×10(-3), n = 22,044), increased triglycerides (p = 2.6×10(-14), n = 93,440), increased waist-to-hip ratio (p = 1.8×10(-5), n = 77,167), increased glucose two hours post oral glucose tolerance testing (p = 4.4×10(-3), n = 15,234), increased fasting insulin (p = 0.015, n = 48,238), but with lower in HDL-cholesterol concentrations (p = 4.5×10(-13), n = 96,748) and decreased BMI (p = 1.4×10(-4), n = 121,335). These findings identify novel genetic determinants of adiponectin levels, which, taken together, influence risk of T2D and markers of insulin resistance.

Johnson T, Gaunt TR, Newhouse SJ, Padmanabhan S, Tomaszewski M, Kumari M, Morris RW, Tzoulaki I, O'Brien ET, Poulter NR et al. 2011. Blood pressure loci identified with a gene-centric array. Am J Hum Genet, 89 (6), pp. 688-700. | Show Abstract | Read more

Raised blood pressure (BP) is a major risk factor for cardiovascular disease. Previous studies have identified 47 distinct genetic variants robustly associated with BP, but collectively these explain only a few percent of the heritability for BP phenotypes. To find additional BP loci, we used a bespoke gene-centric array to genotype an independent discovery sample of 25,118 individuals that combined hypertensive case-control and general population samples. We followed up four SNPs associated with BP at our p < 8.56 × 10(-7) study-specific significance threshold and six suggestively associated SNPs in a further 59,349 individuals. We identified and replicated a SNP at LSP1/TNNT3, a SNP at MTHFR-NPPB independent (r(2) = 0.33) of previous reports, and replicated SNPs at AGT and ATP2B1 reported previously. An analysis of combined discovery and follow-up data identified SNPs significantly associated with BP at p < 8.56 × 10(-7) at four further loci (NPR3, HFE, NOS3, and SOX6). The high number of discoveries made with modest genotyping effort can be attributed to using a large-scale yet targeted genotyping array and to the development of a weighting scheme that maximized power when meta-analyzing results from samples ascertained with extreme phenotypes, in combination with results from nonascertained or population samples. Chromatin immunoprecipitation and transcript expression data highlight potential gene regulatory mechanisms at the MTHFR and NOS3 loci. These results provide candidates for further study to help dissect mechanisms affecting BP and highlight the utility of studying SNPs and samples that are independent of those studied previously even when the sample size is smaller than that in previous studies.

Suttie JJ, Dass S, Bull S, Holloway C, Banerjee R, Cox P, Pitcher A, Franco BR, Francis J, Schneider J et al. 2011. Cardiac Steatosis Detected in Hypertrophic Cardiomyopathy, Dilated Cardiomyopathy and Aortic Stenosis CIRCULATION, 124 (21),

Bown MJ, Jones GT, Harrison SC, Wright BJ, Bumpstead S, Baas AF, Gretarsdottir S, Badger SA, Bradley DT, Burnand K et al. 2011. Abdominal aortic aneurysm is associated with a variant in low-density lipoprotein receptor-related protein 1. Am J Hum Genet, 89 (5), pp. 619-627. | Show Abstract | Read more

Abdominal aortic aneurysm (AAA) is a common cause of morbidity and mortality and has a significant heritability. We carried out a genome-wide association discovery study of 1866 patients with AAA and 5435 controls and replication of promising signals (lead SNP with a p value < 1 × 10(-5)) in 2871 additional cases and 32,687 controls and performed further follow-up in 1491 AAA and 11,060 controls. In the discovery study, nine loci demonstrated association with AAA (p < 1 × 10(-5)). In the replication sample, the lead SNP at one of these loci, rs1466535, located within intron 1 of low-density-lipoprotein receptor-related protein 1 (LRP1) demonstrated significant association (p = 0.0042). We confirmed the association of rs1466535 and AAA in our follow-up study (p = 0.035). In a combined analysis (6228 AAA and 49182 controls), rs1466535 had a consistent effect size and direction in all sample sets (combined p = 4.52 × 10(-10), odds ratio 1.15 [1.10-1.21]). No associations were seen for either rs1466535 or the 12q13.3 locus in independent association studies of coronary artery disease, blood pressure, diabetes, or hyperlipidaemia, suggesting that this locus is specific to AAA. Gene-expression studies demonstrated a trend toward increased LRP1 expression for the rs1466535 CC genotype in arterial tissues; there was a significant (p = 0.029) 1.19-fold (1.04-1.36) increase in LRP1 expression in CC homozygotes compared to TT homozygotes in aortic adventitia. Functional studies demonstrated that rs1466535 might alter a SREBP-1 binding site and influence enhancer activity at the locus. In conclusion, this study has identified a biologically plausible genetic variant associated specifically with AAA, and we suggest that this variant has a possible functional role in LRP1 expression.

International Consortium for Blood Pressure Genome-Wide Association Studies, Ehret GB, Munroe PB, Rice KM, Bochud M, Johnson AD, Chasman DI, Smith AV, Tobin MD, Verwoert GC et al. 2011. Genetic variants in novel pathways influence blood pressure and cardiovascular disease risk. Nature, 478 (7367), pp. 103-109. | Show Abstract | Read more

Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140 mm Hg systolic blood pressure or  ≥90 mm Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention.

IBC 50K CAD Consortium. 2011. Large-scale gene-centric analysis identifies novel variants for coronary artery disease. PLoS Genet, 7 (9), pp. e1002260. | Show Abstract | Read more

Coronary artery disease (CAD) has a significant genetic contribution that is incompletely characterized. To complement genome-wide association (GWA) studies, we conducted a large and systematic candidate gene study of CAD susceptibility, including analysis of many uncommon and functional variants. We examined 49,094 genetic variants in ∼2,100 genes of cardiovascular relevance, using a customised gene array in 15,596 CAD cases and 34,992 controls (11,202 cases and 30,733 controls of European descent; 4,394 cases and 4,259 controls of South Asian origin). We attempted to replicate putative novel associations in an additional 17,121 CAD cases and 40,473 controls. Potential mechanisms through which the novel variants could affect CAD risk were explored through association tests with vascular risk factors and gene expression. We confirmed associations of several previously known CAD susceptibility loci (eg, 9p21.3:p<10(-33); LPA:p<10(-19); 1p13.3:p<10(-17)) as well as three recently discovered loci (COL4A1/COL4A2, ZC3HC1, CYP17A1:p<5×10(-7)). However, we found essentially null results for most previously suggested CAD candidate genes. In our replication study of 24 promising common variants, we identified novel associations of variants in or near LIPA, IL5, TRIB1, and ABCG5/ABCG8, with per-allele odds ratios for CAD risk with each of the novel variants ranging from 1.06-1.09. Associations with variants at LIPA, TRIB1, and ABCG5/ABCG8 were supported by gene expression data or effects on lipid levels. Apart from the previously reported variants in LPA, none of the other ∼4,500 low frequency and functional variants showed a strong effect. Associations in South Asians did not differ appreciably from those in Europeans, except for 9p21.3 (per-allele odds ratio: 1.14 versus 1.27 respectively; P for heterogeneity = 0.003). This large-scale gene-centric analysis has identified several novel genes for CAD that relate to diverse biochemical and cellular functions and clarified the literature with regard to many previously suggested genes.

Rahman TJ, Walker EA, Mayosi BM, Hall DH, Avery PJ, Connell JM, Watkins H, Stewart PM, Keavney B. 2011. Genotype at the P554L variant of the hexose-6 phosphate dehydrogenase gene is associated with carotid intima-medial thickness. PLoS One, 6 (8), pp. e23248. | Show Abstract | Read more

OBJECTIVE: The combined thickness of the intima and media of the carotid artery (carotid intima-medial thickness, CIMT) is associated with cardiovascular disease and stroke. Previous studies indicate that carotid intima-medial thickness is a significantly heritable phenotype, but the responsible genes are largely unknown. Hexose-6 phosphate dehydrogenase (H6PDH) is a microsomal enzyme whose activity regulates corticosteroid metabolism in the liver and adipose tissue; variability in measures of corticosteroid metabolism within the normal range have been associated with risk factors for cardiovascular disease. We performed a genetic association study in 854 members of 224 families to assess the relationship between polymorphisms in the gene coding for hexose-6 phosphate dehydrogenase (H6PD) and carotid intima-medial thickness. METHODS: Families were ascertained via a hypertensive proband. CIMT was measured using B-mode ultrasound. Single nucleotide polymorphisms (SNPs) tagging common variation in the H6PD gene were genotyped. Association was assessed following adjustment for significant covariates including "classical" cardiovascular risk factors. Functional studies to determine the effect of particular SNPs on H6PDH were performed. RESULTS: There was evidence of association between the single nucleotide polymorphism rs17368528 in exon five of the H6PD gene, which encodes an amino-acid change from proline to leucine in the H6PDH protein, and mean carotid intima-medial thickness (p = 0.00065). Genotype was associated with a 5% (or 0.04 mm) higher mean carotid intima-medial thickness measurement per allele, and determined 2% of the population variability in the phenotype. CONCLUSIONS: Our results suggest a novel role for the H6PD gene in atherosclerosis susceptibility.

Leon D, Borinskaya S, Gil A, Kiryanov N, McKee M, Oralov A, Saburova L, Savenko O, Shkolnikov V, Vasilev M, Watkins H. 2011. ALCOHOL-INDUCED DAMAGE TO HEART MUSCLE RATHER THAN ATHEROSCLEROSIS MAY DRIVE THE ASSOCIATION OF CIRCULATORY DISEASE WITH HAZARDOUS DRINKING IN RUSSIA JOURNAL OF EPIDEMIOLOGY AND COMMUNITY HEALTH, 65 (Suppl 1), pp. A15-A15. | Read more

Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R et al. 2011. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Heart Rhythm, 8 (8), pp. 1308-1339. | Read more

Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R et al. 2011. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies: this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Europace, 13 (8), pp. 1077-1109. | Read more

Ashrafian H, McKenna WJ, Watkins H. 2011. Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy. Circ Res, 109 (1), pp. 86-96. | Show Abstract | Read more

As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.

Watkins H, Ashrafian H, Redwood C. 2011. Inherited cardiomyopathies. N Engl J Med, 364 (17), pp. 1643-1656. | Read more

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Watkins H, Ashrafian H, Redwood C. 2011. MECHANISMS OF DISEASE Inherited Cardiomyopathies NEW ENGLAND JOURNAL OF MEDICINE, 364 (17), pp. 1643-1656.

Rahman TJ, Mayosi BM, Hall D, Avery PJ, Stewart PM, Connell JM, Watkins H, Keavney B. 2011. Common variation at the 11-β hydroxysteroid dehydrogenase type 1 gene is associated with left ventricular mass. Circ Cardiovasc Genet, 4 (2), pp. 156-162. | Show Abstract | Read more

BACKGROUND: Polymorphisms in 11-β hydroxysteroid dehydrogenase type 1 (11β-HSD1, encoded by HSD11B1) have been reported to be associated with obesity-related cardiovascular risk factors, such as type II diabetes and hypertension. Left ventricular hypertrophy (LVH) is an independent risk factor for cardiovascular death associated with these factors but has significant additional heritability, the cause of which is undetermined. The 11β-HSD1 is believed to maintain tonic inhibition of the mineralocorticoid receptor in cardiomyocytes, and mineralocorticoid receptor activation is involved in the pathophysiology of LVH. We assessed the association between polymorphisms in the HSD11B1 gene and left ventricular mass (LVM) in 248 families ascertained through a proband with hypertension. METHODS AND RESULTS: LVM was measured by electrocardiography and echocardiography in 868 and 829 participants, respectively. Single-nucleotide polymorphisms (SNPs) tagging common variation in the HSD11B1 gene were genotyped by mass spectrometry. The rs846910 SNP, which lies in the flanking region 5' to exon 1B of HSD11B1, was associated with LVM both by electrocardiography (≈5% lower LVM per copy of the rare allele, P=0.02) and by echocardiography (≈10% lower LVM per copy of the rare allele, P=0.003). Genotype explained 1% to 2% of the population variability in LVM, or approximately 5% of the heritable fraction. There were no significant associations between any HSD11B1 SNP and blood pressure or body mass index that could have confounded the association with LVM. CONCLUSIONS: Genotype at HSD11B1 has a small, but significant effect on LVM, apparently independently of any effect on obesity-related traits. These findings suggest a novel action of 11β-HSD1 in the human cardiomyocyte, which may be of therapeutic importance.

Hall D, Mayosi BM, Rahman TJ, Avery PJ, Watkins HC, Keavney B. 2011. Common variation in the CD36 (fatty acid translocase) gene is associated with left-ventricular mass. J Hypertens, 29 (4), pp. 690-695. | Show Abstract | Read more

AIMS: Genetic variation in the fatty acid translocase (CD36) gene has been shown in animal models to affect several risk factors for the development of left-ventricular hypertrophy, but this phenotype has not, thus far, been investigated in humans. We examined the relationship between common genetic polymorphisms in the CD36 gene and left-ventricular mass. METHODS AND RESULTS: We studied a cohort of 255 families comprising 1425 individuals ascertained via a hypertensive proband. Seven single-nucleotide polymorphisms which together tagged common genetic variation in the CD36 gene were genotyped using a SEQUENOM MALDI-TOF instrument. There was evidence of association between the rs1761663 polymorphism in intron 1 of the CD36 gene and left-ventricular mass determined either by echocardiography (P=0.003, N=780) or electrocardiography (P=0.001, N=814). There was also association between rs1761663 genotype and body mass index (P<0.001, N=1354). Genotype was associated with between 2 and 8% differences in these phenotypes per allele. After adjustment for the effect of body mass index, there remained significant associations between genotype and left ventricular mass measured either by echo (P=0.017) or ECG (P=0.007). CONCLUSIONS: Genotype at the rs1761663 polymorphism has independent effects both on body mass index and left-ventricular mass. Genes with such pleiotropic effects may be particularly attractive therapeutic targets for interventions to modify multiple risk factors for cardiovascular events.

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Wensley F, Gao P, Burgess S, Kaptoge S, Di Angelantonio E, Shah T, Engert JC, Clarke R, Davey-Smith G, Nordestgaard BG et al. 2011. Association between C reactive protein and coronary heart disease: mendelian randomisation analysis based on individual participant data BRITISH MEDICAL JOURNAL, 342 (feb15 2), pp. d548-d548. | Show Abstract | Read more

To use genetic variants as unconfounded proxies of C reactive protein concentration to study its causal role in coronary heart disease. Mendelian randomisation meta-analysis of individual participant data from 47 epidemiological studies in 15 countries. 194418 participants, including 46557 patients with prevalent or incident coronary heart disease. Information was available on four CRP gene tagging single nucleotide polymorphisms (rs3093077, rs1205, rs1130864, rs1800947), concentration of C reactive protein, and levels of other risk factors. Risk ratios for coronary heart disease associated with genetically raised C reactive protein versus risk ratios with equivalent differences in C reactive protein concentration itself, adjusted for conventional risk factors and variability in risk factor levels within individuals. CRP variants were each associated with up to 30% per allele difference in concentration of C reactive protein (P<10(-34)) and were unrelated to other risk factors. Risk ratios for coronary heart disease per additional copy of an allele associated with raised C reactive protein were 0.93 (95% confidence interval 0.87 to 1.00) for rs3093077; 1.00 (0.98 to 1.02) for rs1205; 0.98 (0.96 to 1.00) for rs1130864; and 0.99 (0.94 to 1.03) for rs1800947. In a combined analysis, the risk ratio for coronary heart disease was 1.00 (0.90 to 1.13) per 1 SD higher genetically raised natural log (ln) concentration of C reactive protein. The genetic findings were discordant with the risk ratio observed for coronary heart disease of 1.33 (1.23 to 1.43) per 1 SD higher circulating ln concentration of C reactive protein in prospective studies (P=0.001 for difference). Human genetic data indicate that C reactive protein concentration itself is unlikely to be even a modest causal factor in coronary heart disease.

Ormerod JO, Ashrafian H, Maher AR, Arif S, Steeples V, Born GV, Egginton S, Feelisch M, Watkins H, Frenneaux MP. 2011. The role of vascular myoglobin in nitrite-mediated blood vessel relaxation. Cardiovasc Res, 89 (3), pp. 560-565. | Show Abstract | Read more

AIMS: This work investigates the role of myoglobin in mediating the vascular relaxation induced by nitrite. Nitrite, previously considered an inert by-product of nitric oxide metabolism, is now believed to play an important role in several areas of pharmacology and physiology. Myoglobin can act as a nitrite reductase in the heart, where it is plentiful, but it is present at a far lower level in vascular smooth muscle-indeed, its existence in the vessel wall is controversial. Haem proteins have been postulated to be important in nitrite-induced vasodilation, but the specific role of myoglobin is unknown. The current study was designed to confirm the presence of myoglobin in murine aortic tissue and to test the hypothesis that vascular wall myoglobin is important for nitrite-induced vasodilation. METHODS AND RESULTS: Aortic rings from wild-type and myoglobin knockout mice were challenged with nitrite, before and after exposure to the haem-protein inhibitor carbon monoxide (CO). CO inhibited vasodilation in wild-type rings but not in myoglobin-deficient rings. Restitution of myoglobin using a genetically modified adenovirus both increased vasodilation to nitrite and reinstated the wild-type pattern of response to CO. CONCLUSION: Myoglobin is present in the murine vasculature and contributes significantly to nitrite-induced vasodilation.

Lanktree MB, Guo Y, Murtaza M, Glessner JT, Bailey SD, Onland-Moret NC, Lettre G, Ongen H, Rajagopalan R, Johnson T et al. 2011. Meta-analysis of Dense Genecentric Association Studies Reveals Common and Uncommon Variants Associated with Height. Am J Hum Genet, 88 (1), pp. 6-18. | Show Abstract | Read more

Height is a classic complex trait with common variants in a growing list of genes known to contribute to the phenotype. Using a genecentric genotyping array targeted toward cardiovascular-related loci, comprising 49,320 SNPs across approximately 2000 loci, we evaluated the association of common and uncommon SNPs with adult height in 114,223 individuals from 47 studies and six ethnicities. A total of 64 loci contained a SNP associated with height at array-wide significance (p < 2.4 × 10(-6)), with 42 loci surpassing the conventional genome-wide significance threshold (p < 5 × 10(-8)). Common variants with minor allele frequencies greater than 5% were observed to be associated with height in 37 previously reported loci. In individuals of European ancestry, uncommon SNPs in IL11 and SMAD3, which would not be genotyped with the use of standard genome-wide genotyping arrays, were strongly associated with height (p < 3 × 10(-11)). Conditional analysis within associated regions revealed five additional variants associated with height independent of lead SNPs within the locus, suggesting allelic heterogeneity. Although underpowered to replicate findings from individuals of European ancestry, the direction of effect of associated variants was largely consistent in African American, South Asian, and Hispanic populations. Overall, we show that dense coverage of genes for uncommon SNPs, coupled with large-scale meta-analysis, can successfully identify additional variants associated with a common complex trait.

Soranzo N, Sanna S, Wheeler E, Gieger C, Radke D, Dupuis J, Bouatia-Naji N, Langenberg C, Prokopenko I, Stolerman E et al. 2011. Common variants at 10 genomic loci influence hemoglobin A<inf>1C</inf> levels via glycemic and nonglycemic pathways (Diabetes (2010) 59, (3229-3239)) Diabetes, 60 (3), pp. 1051.

Strawbridge RJ, Dupuis J, Prokopenko I, Barker A, Ahlqvist E, Rybin D, Petrie JR, Travers ME, Bouatia-Naji N, Dimas AS et al. 2011. Genome-wide association identifies nine common variants associated with fasting proinsulin levels and provides new insights into the pathophysiology of type 2 diabetes. Diabetes, 60 (10), pp. 2624-2634. | Show Abstract | Read more

OBJECTIVE: Proinsulin is a precursor of mature insulin and C-peptide. Higher circulating proinsulin levels are associated with impaired β-cell function, raised glucose levels, insulin resistance, and type 2 diabetes (T2D). Studies of the insulin processing pathway could provide new insights about T2D pathophysiology. RESEARCH DESIGN AND METHODS: We have conducted a meta-analysis of genome-wide association tests of ∼2.5 million genotyped or imputed single nucleotide polymorphisms (SNPs) and fasting proinsulin levels in 10,701 nondiabetic adults of European ancestry, with follow-up of 23 loci in up to 16,378 individuals, using additive genetic models adjusted for age, sex, fasting insulin, and study-specific covariates. RESULTS: Nine SNPs at eight loci were associated with proinsulin levels (P < 5 × 10(-8)). Two loci (LARP6 and SGSM2) have not been previously related to metabolic traits, one (MADD) has been associated with fasting glucose, one (PCSK1) has been implicated in obesity, and four (TCF7L2, SLC30A8, VPS13C/C2CD4A/B, and ARAP1, formerly CENTD2) increase T2D risk. The proinsulin-raising allele of ARAP1 was associated with a lower fasting glucose (P = 1.7 × 10(-4)), improved β-cell function (P = 1.1 × 10(-5)), and lower risk of T2D (odds ratio 0.88; P = 7.8 × 10(-6)). Notably, PCSK1 encodes the protein prohormone convertase 1/3, the first enzyme in the insulin processing pathway. A genotype score composed of the nine proinsulin-raising alleles was not associated with coronary disease in two large case-control datasets. CONCLUSIONS: We have identified nine genetic variants associated with fasting proinsulin. Our findings illuminate the biology underlying glucose homeostasis and T2D development in humans and argue against a direct role of proinsulin in coronary artery disease pathogenesis.

Chambers JC, Zhang W, Sehmi J, Li X, Wass MN, Van der Harst P, Holm H, Sanna S, Kavousi M, Baumeister SE et al. 2011. Genome-wide association study identifies loci influencing concentrations of liver enzymes in plasma Nature Genetics,

Chambers JC, Zhang W, Sehmi J, Li X, Wass MN, Van der Harst P, Holm H, Sanna S, Kavousi M, Baumeister SE et al. 2011. Genome-wide association study identifies loci influencing concentrations of liver enzymes in plasma. Nat Genet, 43 (11), pp. 1131-1138. | Show Abstract | Read more

Concentrations of liver enzymes in plasma are widely used as indicators of liver disease. We carried out a genome-wide association study in 61,089 individuals, identifying 42 loci associated with concentrations of liver enzymes in plasma, of which 32 are new associations (P = 10(-8) to P = 10(-190)). We used functional genomic approaches including metabonomic profiling and gene expression analyses to identify probable candidate genes at these regions. We identified 69 candidate genes, including genes involved in biliary transport (ATP8B1 and ABCB11), glucose, carbohydrate and lipid metabolism (FADS1, FADS2, GCKR, JMJD1C, HNF1A, MLXIPL, PNPLA3, PPP1R3B, SLC2A2 and TRIB1), glycoprotein biosynthesis and cell surface glycobiology (ABO, ASGR1, FUT2, GPLD1 and ST3GAL4), inflammation and immunity (CD276, CDH6, GCKR, HNF1A, HPR, ITGA1, RORA and STAT4) and glutathione metabolism (GSTT1, GSTT2 and GGT), as well as several genes of uncertain or unknown function (including ABHD12, EFHD1, EFNA1, EPHA2, MICAL3 and ZNF827). Our results provide new insight into genetic mechanisms and pathways influencing markers of liver function.

Wain LV, Verwoert GC, O'Reilly PF, Shi G, Johnson T, Johnson AD, Bochud M, Rice KM, Henneman P, Smith AV et al. 2011. Genome-wide association study identifies six new loci influencing pulse pressure and mean arterial pressure. Nat Genet, 43 (10), pp. 1005-1011. | Show Abstract | Read more

Numerous genetic loci have been associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP) in Europeans. We now report genome-wide association studies of pulse pressure (PP) and mean arterial pressure (MAP). In discovery (N = 74,064) and follow-up studies (N = 48,607), we identified at genome-wide significance (P = 2.7 × 10(-8) to P = 2.3 × 10(-13)) four new PP loci (at 4q12 near CHIC2, 7q22.3 near PIK3CG, 8q24.12 in NOV and 11q24.3 near ADAMTS8), two new MAP loci (3p21.31 in MAP4 and 10q25.3 near ADRB1) and one locus associated with both of these traits (2q24.3 near FIGN) that has also recently been associated with SBP in east Asians. For three of the new PP loci, the estimated effect for SBP was opposite of that for DBP, in contrast to the majority of common SBP- and DBP-associated variants, which show concordant effects on both traits. These findings suggest new genetic pathways underlying blood pressure variation, some of which may differentially influence SBP and DBP.

Rahman TJ, Walker EA, Mayosi BM, Hall DH, Avery PJ, Connell JMC, Watkins H, Stewart PM, Keavney B. 2011. Genotype at the P554L variant of the hexose-6 phosphate dehydrogenase gene is associated with carotid intima-medial thickness PLoS ONE, 6 (8), | Show Abstract | Read more

Objective: The combined thickness of the intima and media of the carotid artery (carotid intima-medial thickness, CIMT) is associated with cardiovascular disease and stroke. Previous studies indicate that carotid intima-medial thickness is a significantly heritable phenotype, but the responsible genes are largely unknown. Hexose-6 phosphate dehydrogenase (H6PDH) is a microsomal enzyme whose activity regulates corticosteroid metabolism in the liver and adipose tissue; variability in measures of corticosteroid metabolism within the normal range have been associated with risk factors for cardiovascular disease. We performed a genetic association study in 854 members of 224 families to assess the relationship between polymorphisms in the gene coding for hexose-6 phosphate dehydrogenase (H6PD) and carotid intima-medial thickness. Methods: Families were ascertained via a hypertensive proband. CIMT was measured using B-mode ultrasound. Single nucleotide polymorphisms (SNPs) tagging common variation in the H6PD gene were genotyped. Association was assessed following adjustment for significant covariates including "classical" cardiovascular risk factors. Functional studies to determine the effect of particular SNPs on H6PDH were performed. Results: There was evidence of association between the single nucleotide polymorphism rs17368528 in exon five of the H6PD gene, which encodes an amino-acid change from proline to leucine in the H6PDH protein, and mean carotid intima-medial thickness (p = 0.00065). Genotype was associated with a 5% (or 0.04 mm) higher mean carotid intima-medial thickness measurement per allele, and determined 2% of the population variability in the phenotype. Conclusions: Our results suggest a novel role for the H6PD gene in atherosclerosis susceptibility. © 2011 Rahman et al.

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Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R et al. 2011. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies Europace, 13 (8), pp. 1077-1109. | Read more

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Ackerman MJ, Priori SG, Willems S, Berul C, Brugada R, Calkins H, Camm AJ, Ellinor PT, Gollob M, Hamilton R et al. 2011. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies: This document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA) Heart Rhythm, 8 (8), pp. 1308-1339. | Read more

Coronary Artery Disease (C4D) Genetics Consortium. 2011. A genome-wide association study in Europeans and South Asians identifies five new loci for coronary artery disease. Nat Genet, 43 (4), pp. 339-344. | Show Abstract | Read more

Genome-wide association studies have identified 11 common variants convincingly associated with coronary artery disease (CAD)¹⁻⁷, a modest number considering the apparent heritability of CAD⁸. All of these variants have been discovered in European populations. We report a meta-analysis of four large genome-wide association studies of CAD, with ∼575,000 genotyped SNPs in a discovery dataset comprising 15,420 individuals with CAD (cases) (8,424 Europeans and 6,996 South Asians) and 15,062 controls. There was little evidence for ancestry-specific associations, supporting the use of combined analyses. Replication in an independent sample of 21,408 cases and 19,185 controls identified five loci newly associated with CAD (P < 5 × 10⁻⁸ in the combined discovery and replication analysis): LIPA on 10q23, PDGFD on 11q22, ADAMTS7-MORF4L1 on 15q25, a gene rich locus on 7q22 and KIAA1462 on 10p11. The CAD-associated SNP in the PDGFD locus showed tissue-specific cis expression quantitative trait locus effects. These findings implicate new pathways for CAD susceptibility.

CARDIoGRAMplusC4D Consortium, Deloukas P, Kanoni S, Willenborg C, Farrall M, Assimes TL, Thompson JR, Ingelsson E, Saleheen D, Erdmann J et al. 2013. Large-scale association analysis identifies new risk loci for coronary artery disease. Nat Genet, 45 (1), pp. 25-33. | Show Abstract | Read more

Coronary artery disease (CAD) is the commonest cause of death. Here, we report an association analysis in 63,746 CAD cases and 130,681 controls identifying 15 loci reaching genome-wide significance, taking the number of susceptibility loci for CAD to 46, and a further 104 independent variants (r(2) < 0.2) strongly associated with CAD at a 5% false discovery rate (FDR). Together, these variants explain approximately 10.6% of CAD heritability. Of the 46 genome-wide significant lead SNPs, 12 show a significant association with a lipid trait, and 5 show a significant association with blood pressure, but none is significantly associated with diabetes. Network analysis with 233 candidate genes (loci at 10% FDR) generated 5 interaction networks comprising 85% of these putative genes involved in CAD. The four most significant pathways mapping to these networks are linked to lipid metabolism and inflammation, underscoring the causal role of these activities in the genetic etiology of CAD. Our study provides insights into the genetic basis of CAD and identifies key biological pathways.

Kiechl S, Laxton RC, Xiao Q, Hernesniemi JA, Raitakari OT, Kähönen M, Mayosi BM, Jula A, Moilanen L, Willeit J et al. 2010. Coronary artery disease-related genetic variant on chromosome 10q11 is associated with carotid intima-media thickness and atherosclerosis. Arterioscler Thromb Vasc Biol, 30 (12), pp. 2678-2683. | Show Abstract | Read more

OBJECTIVE: To investigate whether chromosome 10q11.21 influences common carotid intima-media thickness (IMT) and atherosclerosis and whether it is associated with stromal cell-derived factor-1α (SDF-1α) plasma levels. METHODS AND RESULTS: Variation on chromosome 10q11.21 has been consistently associated with coronary artery disease. The genetic variant lies upstream of the gene encoding SDF-1α. We genotyped 3 population cohorts (Bruneck [age range, 45 to 94 years; 50.0% men; n=738], Health2000 [age range, 46 to 76 years; 55.4% men; n=1237], and essential hypertension in families collected in the region of Oxford [HTO] [age range, 19 to 88 years; 47.9% men; n=770]) for single-nucleotide polymorphism rs501120 at the 10q11.21 locus and conducted a meta-analysis in these cohorts to ascertain a relationship between the polymorphism and carotid IMT. The analysis showed that individuals with the T/T genotype had a significantly higher carotid IMT than individuals with the C/T or C/C genotype (pooled weighted mean difference, 23 μm [95% CI, 9 to 37 μm], P=0.0014 under a fixed-effects model; and 23 μm [95% CI, 6 to 41 μm], P=0.009 under a random-effects model). In the Bruneck cohort, in which data for carotid atherosclerosis and plasma SDF-1α levels were available, we observed an association of the T/T genotype with a higher burden of atherosclerosis and increased susceptibility to the development of atherosclerosis during a 5-year follow-up (multivariable odds ratio, 1.73 [95% CI, 1.18 to 2.52]; P=0.005 for the recessive model) and an association between the T/T genotype and lower SDF-1α levels (2.62 ng/mL for T/T versus 2.74 ng/mL for C/C or C/T; P=0.023). CONCLUSIONS: The coronary heart disease-related variant at the 10q11.21 locus is associated with carotid IMT and atherosclerosis.

Hopewell JC, Peden J, Saleheen D, Chambers J, Clarke R, Collins R, Danesh J, Deloukas P, Elliott P, Farrall M et al. 2010. A Genome-Wide Association Study of Risk of Coronary Artery Disease in European and South Asian Populations CIRCULATION, 122 (21),

Hopewell JC, Clarke R, Seedorf U, Farrall M, Hamsten A, Collins R, Watkins H, Consortium PROCARDIS. 2010. Association of Apolipoprotein(a) Isoforms With Coronary Heart Disease is Mediated Through Plasma Lipoprotein(a) Levels CIRCULATION, 122 (21),

Hoskins AC, Jacques A, Bardswell SC, McKenna WJ, Tsang V, dos Remedios CG, Ehler E, Adams K, Jalilzadeh S, Avkiran M et al. 2010. Normal passive viscoelasticity but abnormal myofibrillar force generation in human hypertrophic cardiomyopathy. J Mol Cell Cardiol, 49 (5), pp. 737-745. | Show Abstract | Read more

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy, increased ventricular stiffness and impaired diastolic filling. We investigated to what extent myocardial functional defects can be explained by alterations in the passive and active properties of human cardiac myofibrils. Skinned ventricular myocytes were prepared from patients with obstructive HCM (two patients with MYBPC3 mutations, one with a MYH7 mutation, and three with no mutation in either gene) and from four donors. Passive stiffness, viscous properties, and titin isoform expression were similar in HCM myocytes and donor myocytes. Maximal Ca(2+)-activated force was much lower in HCM myocytes (14 ± 1 kN/m(2)) than in donor myocytes (23 ± 3 kN/m(2); P<0.01), though cross-bridge kinetics (k(tr)) during maximal Ca(2)(+) activation were 10% faster in HCM myocytes. Myofibrillar Ca(2)(+) sensitivity in HCM myocytes (pCa(50)=6.40 ± 0.05) was higher than for donor myocytes (pCa(50)=6.09 ± 0.02; P<0.001) and was associated with reduced phosphorylation of troponin-I (ser-23/24) and MyBP-C (ser-282) in HCM myocytes. These characteristics were common to all six HCM patients and may therefore represent a secondary consequence of the known and unknown underlying genetic variants. Some HCM patients did however exhibit an altered relationship between force and cross-bridge kinetics at submaximal Ca(2+) concentrations, which may reflect the primary mutation. We conclude that the passive viscoelastic properties of the myocytes are unlikely to account for the increased stiffness of the HCM ventricle. However, the low maximum Ca(2+)-activated force and high Ca(2+) sensitivity of the myofilaments are likely to contribute substantially to any systolic and diastolic dysfunction, respectively, in hearts of HCM patients.

Abozguia K, Elliott P, McKenna W, Phan TT, Nallur-Shivu G, Ahmed I, Maher AR, Kaur K, Taylor J, Henning A et al. 2010. Metabolic modulator perhexiline corrects energy deficiency and improves exercise capacity in symptomatic hypertrophic cardiomyopathy. Circulation, 122 (16), pp. 1562-1569. | Show Abstract | Read more

BACKGROUND: Hypertrophic cardiomyopathy patients exhibit myocardial energetic impairment, but a causative role for this energy deficiency in the pathophysiology of hypertrophic cardiomyopathy remains unproven. We hypothesized that the metabolic modulator perhexiline would ameliorate myocardial energy deficiency and thereby improve diastolic function and exercise capacity. METHODS AND RESULTS: Forty-six consecutive patients with symptomatic exercise limitation (peak Vo(2) <75% of predicted) caused by nonobstructive hypertrophic cardiomyopathy (mean age, 55±0.26 years) were randomized to perhexiline 100 mg (n=24) or placebo (n=22). Myocardial ratio of phosphocreatine to adenosine triphosphate, an established marker of cardiac energetic status, as measured by (31)P magnetic resonance spectroscopy, left ventricular diastolic filling (heart rate normalized time to peak filling) at rest and during exercise using radionuclide ventriculography, peak Vo(2), symptoms, quality of life, and serum metabolites were assessed at baseline and study end (4.6±1.8 months). Perhexiline improved myocardial ratios of phosphocreatine to adenosine triphosphate (from 1.27±0.02 to 1.73±0.02 versus 1.29±0.01 to 1.23±0.01; P=0.003) and normalized the abnormal prolongation of heart rate normalized time to peak filling between rest and exercise (0.11±0.008 to -0.01±0.005 versus 0.15±0.007 to 0.11±0.008 second; P=0.03). These changes were accompanied by an improvement in primary end point (peak Vo(2)) (22.2±0.2 to 24.3±0.2 versus 23.6±0.3 to 22.3±0.2 mL · kg(-1) · min(-1); P=0.003) and New York Heart Association class (P<0.001) (all P values ANCOVA, perhexiline versus placebo). CONCLUSIONS: In symptomatic hypertrophic cardiomyopathy, perhexiline, a modulator of substrate metabolism, ameliorates cardiac energetic impairment, corrects diastolic dysfunction, and increases exercise capacity. This study supports the hypothesis that energy deficiency contributes to the pathophysiology and provides a rationale for further consideration of metabolic therapies in hypertrophic cardiomyopathy.

Lango Allen H, Estrada K, Lettre G, Berndt SI, Weedon MN, Rivadeneira F, Willer CJ, Jackson AU, Vedantam S, Raychaudhuri S et al. 2010. Hundreds of variants clustered in genomic loci and biological pathways affect human height. Nature, 467 (7317), pp. 832-838. | Show Abstract | Read more

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.

Figtree GA, Robinson BG, Channon KM, Watkins H. 2010. Polymorphism upstream of estrogen receptor alpha reverses negative regulation of transcription. Int J Cardiol, 144 (1), pp. 86-88. | Read more

Figtree GA, Guzik T, Robinson BG, Channon KM, Watkins H. 2010. Functional estrogen receptor alpha promoter polymorphism is associated with improved endothelial-dependent vasolidation. Int J Cardiol, 143 (2), pp. 207-208. | Show Abstract | Read more

Estrogen receptor alpha (ERalpha) mediates beneficial actions on endothelial nitric oxide synthase (eNOS) and cholesterol metabolism. Genetic variations in the promoter of the ERalpha may therefore influence vascular function. We have identified a single nucleotide polymorphism (T>C) in the transcriptional element "ERNE" upstream of ERalpha which abolished the negative effect of this element in luciferase reporter assays and was associated with reduction in LDL cholesterol in a small association study. We have now examined for the association of this putative functional polymorphism with endothelial function. Endothelial-dependent relaxation (EDR) was measured in organ bath preparations of human saphenous vein obtained from 101 individuals (81 males and 20 females) undergoing coronary artery bypass surgery. The presence of the variant C allele was associated with enhanced EDR independently of hypercholesterolaemia, smoking and diabetes, as well as sex (ANOVA for ACh induced relaxation: p=0.033). In males, the presence of the C allele was associated with a 225% augmentation of endothelial-dependent relaxation compared to wild-type (55.5+/-10%; n=3 vs. 24.7+/-1%; n=78; p<0.001). In summary, a polymorphism in the ERalpha negative transcriptional element which results in increased transcription in vitro is associated with substantial augmentation of endothelial-dependent vasorelaxation.

Sliwa K, Hilfiker-Kleiner D, Petrie MC, Mebazaa A, Pieske B, Buchmann E, Regitz-Zagrosek V, Schaufelberger M, Tavazzi L, van Veldhuisen DJ et al. 2010. Current state of knowledge on aetiology, diagnosis, management, and therapy of peripartum cardiomyopathy: a position statement from the Heart Failure Association of the European Society of Cardiology Working Group on peripartum cardiomyopathy. Eur J Heart Fail, 12 (8), pp. 767-778. | Show Abstract | Read more

Peripartum cardiomyopathy (PPCM) is a cause of pregnancy-associated heart failure. It typically develops during the last month of, and up to 6 months after, pregnancy in women without known cardiovascular disease. The present position statement offers a state-of-the-art summary of what is known about risk factors for potential pathophysiological mechanisms, clinical presentation of, and diagnosis and management of PPCM. A high index of suspicion is required for the diagnosis, as shortness of breath and ankle swelling are common in the peripartum period. Peripartum cardiomyopathy is a distinct form of cardiomyopathy, associated with a high morbidity and mortality, but also with the possibility of full recovery. Oxidative stress and the generation of a cardiotoxic subfragment of prolactin may play key roles in the pathophysiology of PPCM. In this regard, pharmacological blockade of prolactin offers the possibility of a disease-specific therapy.

Garratt CJ, Elliott P, Behr E, Camm AJ, Cowan C, Cruickshank S, Grace A, Griffith MJ, Jolly A, Lambiase P et al. 2010. Heart Rhythm UK position statement on clinical indications for implantable cardioverter defibrillators in adult patients with familial sudden cardiac death syndromes. Europace, 12 (8), pp. 1156-1175. | Show Abstract | Read more

Whilst the decision regarding defibrillator implantation in a patient with a familial sudden cardiac death syndrome is likely to be most significant for any particular individual, the clinical decision-making process itself is complex and requires interpretation and extrapolation of information from a number of different sources. This document provides recommendations for adult patients with the congenital Long QT syndromes, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy. Although these specific conditions differ in terms of clinical features and prognosis, it is possible and logical to take an approach to determining a threshold for implantable cardioveter-defibrillator implantation that is common to all of the familial sudden cardiac death syndromes based on estimates of absolute risk of sudden death.

Burgess S, Thompson SG, CRP CHD Genetics Collaboration, Burgess S, Thompson SG, Andrews G, Samani NJ, Hall A, Whincup P, Morris R et al. 2010. Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables. Stat Med, 29 (12), pp. 1298-1311. | Show Abstract | Read more

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

Triglyceride Coronary Disease Genetics Consortium and Emerging Risk Factors Collaboration, Sarwar N, Sandhu MS, Ricketts SL, Butterworth AS, Di Angelantonio E, Boekholdt SM, Ouwehand W, Watkins H, Samani NJ et al. 2010. Triglyceride-mediated pathways and coronary disease: collaborative analysis of 101 studies. Lancet, 375 (9726), pp. 1634-1639. | Show Abstract | Read more

BACKGROUND: Whether triglyceride-mediated pathways are causally relevant to coronary heart disease is uncertain. We studied a genetic variant that regulates triglyceride concentration to help judge likelihood of causality. METHODS: We assessed the -1131T>C (rs662799) promoter polymorphism of the apolipoprotein A5 (APOA5) gene in relation to triglyceride concentration, several other risk factors, and risk of coronary heart disease. We compared disease risk for genetically-raised triglyceride concentration (20,842 patients with coronary heart disease, 35,206 controls) with that recorded for equivalent differences in circulating triglyceride concentration in prospective studies (302 430 participants with no history of cardiovascular disease; 12,785 incident cases of coronary heart disease during 2.79 million person-years at risk). We analysed -1131T>C in 1795 people without a history of cardiovascular disease who had information about lipoprotein concentration and diameter obtained by nuclear magnetic resonance spectroscopy. FINDINGS: The minor allele frequency of -1131T>C was 8% (95% CI 7-9). -1131T>C was not significantly associated with several non-lipid risk factors or LDL cholesterol, and it was modestly associated with lower HDL cholesterol (mean difference per C allele 3.5% [95% CI 2.6-4.6]; 0.053 mmol/L [0.039-0.068]), lower apolipoprotein AI (1.3% [0.3-2.3]; 0.023 g/L [0.005-0.041]), and higher apolipoprotein B (3.2% [1.3-5.1]; 0.027 g/L [0.011-0.043]). By contrast, for every C allele inherited, mean triglyceride concentration was 16.0% (95% CI 12.9-18.7), or 0.25 mmol/L (0.20-0.29), higher (p=4.4x10(-24)). The odds ratio for coronary heart disease was 1.18 (95% CI 1.11-1.26; p=2.6x10(-7)) per C allele, which was concordant with the hazard ratio of 1.10 (95% CI 1.08-1.12) per 16% higher triglyceride concentration recorded in prospective studies. -1131T>C was significantly associated with higher VLDL particle concentration (mean difference per C allele 12.2 nmol/L [95% CI 7.7-16.7]; p=9.3x10(-8)) and smaller HDL particle size (0.14 nm [0.08-0.20]; p=7.0x10(-5)), factors that could mediate the effects of triglyceride. INTERPRETATION: These data are consistent with a causal association between triglyceride-mediated pathways and coronary heart disease. FUNDING: British Heart Foundation, UK Medical Research Council, Novartis.

Wordsworth S, Leal J, Blair E, Legood R, Thomson K, Seller A, Taylor J, Watkins H. 2010. DNA testing for hypertrophic cardiomyopathy: a cost-effectiveness model. Eur Heart J, 31 (8), pp. 926-935. | Show Abstract | Read more

Aims To explore the cost-effectiveness of alternative methods of screening family members for hypertrophic cardiomyopathy (HCM), the most common monogenic cardiac disorder and the most frequent cause of sudden cardiac death (SCD) in young people. Methods and results Economic decision model comparing cascade screening by genetic, as opposed to clinical methods. The incremental cost per life year saved was 14,397 euro for the cascade genetic compared with the cascade clinical approach. Genetic diagnostic strategies are more likely to be cost-effective than clinical tests alone. The costs for cascade molecular genetic testing were slightly higher than clinical testing in the short run, but this was largely because the genetic approach is more effective and identifies more individuals at risk. Conclusion The use of molecular genetic information in the diagnosis and management of HCM is a cost-effective approach to the primary prevention of SCD in these patients.

Phillips D, Ten Hove M, Schneider JE, Wu CO, Sebag-Montefiore L, Aponte AM, Lygate CA, Wallis J, Clarke K, Watkins H et al. 2010. Mice over-expressing the myocardial creatine transporter develop progressive heart failure and show decreased glycolytic capacity. J Mol Cell Cardiol, 48 (4), pp. 582-590. | Show Abstract | Read more

The metabolic phenotype of the failing heart includes a decrease in phosphocreatine and total creatine concentration [Cr], potentially contributing to contractile dysfunction. Surprisingly, in 32- week-old mice over-expressing the myocardial creatine transporter (CrT-OE), we previously demonstrated that elevated [Cr] correlates with left ventricular (LV) hypertrophy and failure. The aim of this study was to determine the temporal relationship between elevated [Cr] and the onset of cardiac dysfunction and to screen for potential molecular mechanisms. CrT-OE mice were compared with wild-type (WT) littermate controls longitudinally using cine-MRI to measure cardiac function and single-voxel (1)H-MRS to measure [Cr] in vivo at 6, 16, 32, and 52 weeks of age. CrT-OE mice had elevated [Cr] at 6 weeks (mean 1.9-fold), which remained constant throughout life. Despite this increased [Cr], LV dysfunction was not apparent until 16 weeks and became more pronounced with age. Additionally, LV tissue from 12 to 14 week old CrT-OE mice was compared to WT using 2D difference in-gel electrophoresis (DIGE). These analyses detected a majority of the heart's metabolic enzymes and identified seven proteins that were differentially expressed between groups. The most pronounced protein changes were related to energy metabolism: alpha- and beta-enolase were selectively decreased (p<0.05), while the remaining enzymes of glycolysis were unchanged. Consistent with a decrease in enolase content, its activity was significantly lower in CrT-OE hearts (in WT, 0.59+/-0.02 micromol ATP produced/microg protein/min; CrT-OE, 0.31+/-0.06; p<0.01). Additionally, anaerobic lactate production was decreased in CrT-OE mice (in WT, 102+/-3 micromol/g wet myocardium; CrT-OE, 78+/-13; p=0.02), consistent with decreased glycolytic capacity. Finally, we found that enolase may be regulated by increased expression of the beta-enolase repressor transcription factor, which was significantly increased in CrT-OE hearts. This study demonstrates that chronically increased myocardial [Cr] in the CrT-OE model leads to the development of progressive hypertrophy and heart failure, which may be mediated by a compromise in glycolytic capacity at the level of enolase.

Farrall M, Clarke R, Watkins H. 2010. Genetic Variants in Lp(a) Lipoprotein and Coronary Disease REPLY NEW ENGLAND JOURNAL OF MEDICINE, 362 (12), pp. 1147-1147.

Dupuis J, Langenberg C, Prokopenko I, Saxena R, Soranzo N, Jackson AU, Wheeler E, Glazer NL, Bouatia-Naji N, Gloyn AL et al. 2010. New genetic loci implicated in fasting glucose homeostasis and their impact on type 2 diabetes risk. Nat Genet, 42 (2), pp. 105-116. | Show Abstract | Read more

Levels of circulating glucose are tightly regulated. To identify new loci influencing glycemic traits, we performed meta-analyses of 21 genome-wide association studies informative for fasting glucose, fasting insulin and indices of beta-cell function (HOMA-B) and insulin resistance (HOMA-IR) in up to 46,186 nondiabetic participants. Follow-up of 25 loci in up to 76,558 additional subjects identified 16 loci associated with fasting glucose and HOMA-B and two loci associated with fasting insulin and HOMA-IR. These include nine loci newly associated with fasting glucose (in or near ADCY5, MADD, ADRA2A, CRY2, FADS1, GLIS3, SLC2A2, PROX1 and C2CD4B) and one influencing fasting insulin and HOMA-IR (near IGF1). We also demonstrated association of ADCY5, PROX1, GCK, GCKR and DGKB-TMEM195 with type 2 diabetes. Within these loci, likely biological candidate genes influence signal transduction, cell proliferation, development, glucose-sensing and circadian regulation. Our results demonstrate that genetic studies of glycemic traits can identify type 2 diabetes risk loci, as well as loci containing gene variants that are associated with a modest elevation in glucose levels but are not associated with overt diabetes.

Lakdawala NK, Dellefave L, Redwood CS, Sparks E, Cirino AL, Depalma S, Colan SD, Funke B, Zimmerman RS, Robinson P et al. 2010. Familial dilated cardiomyopathy caused by an alpha-tropomyosin mutation: the distinctive natural history of sarcomeric dilated cardiomyopathy. J Am Coll Cardiol, 55 (4), pp. 320-329. | Show Abstract | Read more

OBJECTIVES: We sought to further define the role of sarcomere mutations in dilated cardiomyopathy (DCM) and associated clinical phenotypes. BACKGROUND: Mutations in several contractile proteins contribute to DCM, but definitive evidence for the roles of most sarcomere genes remains limited by the lack of robust genetic support. METHODS: Direct sequencing of 6 sarcomere genes was performed on 334 probands with DCM. A novel D230N missense mutation in the gene encoding alpha-tropomyosin (TPM1) was identified. Functional assessment was performed by the use of an in vitro reconstituted sarcomere complex to evaluate ATPase regulation and Ca(2+) affinity as correlates of contractility. RESULTS: TPM1 D230N segregated with DCM in 2 large unrelated families. This mutation altered an evolutionarily conserved residue and was absent in >1,000 control chromosomes. In vitro studies demonstrated major inhibitory effects on sarcomere function with reduced Ca(2+) sensitivity, maximum activation, and Ca(2+) affinity compared with wild-type TPM1. Clinical manifestations ranged from decompensated heart failure or sudden death in those presenting early in life to asymptomatic left ventricular dysfunction in those diagnosed during adulthood. Notably, several affected infants had remarkable improvement. CONCLUSIONS: Genetic segregation in 2 unrelated families and functional analyses conclusively establish a pathogenic role for TPM1 mutations in DCM. In vitro results demonstrate contrasting effects of DCM and hypertrophic cardiomyopathy mutations in TPM1, suggesting that specific functional consequences shape cardiac remodeling. Along with previous reports, our data support a distinctive, age-dependent phenotype with sarcomere-associated DCM where presentation early in life is associated with severe, sometimes lethal, disease. These observations have implications for the management of familial DCM.

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Ashrafian H, Docherty L, Leo V, Towlson C, Neilan M, Steeples V, Lygate CA, Hough T, Townsend S, Williams D et al. 2010. A mutation in the mitochondrial fission gene Dnm1l leads to cardiomyopathy PLoS Genetics, 6 (6), pp. 1-18. | Show Abstract | Read more

Mutations in a number of genes have been linked to inherited dilated cardiomyopathy (DCM). However, such mutations account for only a small proportion of the clinical cases emphasising the need for alternative discovery approaches to uncovering novel pathogenic mutations in hitherto unidentified pathways. Accordingly, as part of a large-scale N-ethyl-Nnitrosourea mutagenesis screen, we identified a mouse mutant, Python, which develops DCM. We demonstrate that the Python phenotype is attributable to a dominant fully penetrant mutation in the dynamin-1-like (Dnm1l) gene, which has been shown to be critical for mitochondrial fission. The C452F mutation is in a highly conserved region of the M domain of Dnm1l that alters protein interactions in a yeast two-hybrid system, suggesting that the mutation might alter intramolecular interactions within the Dnm1l monomer. Heterozygous Python fibroblasts exhibit abnormal mitochondria and peroxisomes. Homozygosity for the mutation results in the death of embryos midway though gestation. Heterozygous Python hearts show reduced levels of mitochondria enzyme complexes and suffer from cardiac ATP depletion. The resulting energy deficiency may contribute to cardiomyopathy. This is the first demonstration that a defect in a gene involved in mitochondrial remodelling can result in cardiomyopathy, showing that the function of this gene is needed for the maintenance of normal cellular function in a relatively tissue-specific manner. This disease model attests to the importance of mitochondrial remodelling in the heart; similar defects might underlie human heart muscle disease. © 2010 Ashrafian et al.

Ashrafian H, Docherty L, Leo V, Towlson C, Neilan M, Steeples V, Lygate CA, Hough T, Townsend S, Williams D et al. 2010. A mutation in the mitochondrial fission gene Dnm1l leads to cardiomyopathy. PLoS Genet, 6 (6), pp. e1001000. | Show Abstract | Read more

Mutations in a number of genes have been linked to inherited dilated cardiomyopathy (DCM). However, such mutations account for only a small proportion of the clinical cases emphasising the need for alternative discovery approaches to uncovering novel pathogenic mutations in hitherto unidentified pathways. Accordingly, as part of a large-scale N-ethyl-N-nitrosourea mutagenesis screen, we identified a mouse mutant, Python, which develops DCM. We demonstrate that the Python phenotype is attributable to a dominant fully penetrant mutation in the dynamin-1-like (Dnm1l) gene, which has been shown to be critical for mitochondrial fission. The C452F mutation is in a highly conserved region of the M domain of Dnm1l that alters protein interactions in a yeast two-hybrid system, suggesting that the mutation might alter intramolecular interactions within the Dnm1l monomer. Heterozygous Python fibroblasts exhibit abnormal mitochondria and peroxisomes. Homozygosity for the mutation results in the death of embryos midway though gestation. Heterozygous Python hearts show reduced levels of mitochondria enzyme complexes and suffer from cardiac ATP depletion. The resulting energy deficiency may contribute to cardiomyopathy. This is the first demonstration that a defect in a gene involved in mitochondrial remodelling can result in cardiomyopathy, showing that the function of this gene is needed for the maintenance of normal cellular function in a relatively tissue-specific manner. This disease model attests to the importance of mitochondrial remodelling in the heart; similar defects might underlie human heart muscle disease.

Cited:

1216

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Speliotes EK, Willer CJ, Berndt SI, Monda KL, Thorleifsson G, Jackson AU, Allen HL, Lindgren CM, Luan J, Maegi R et al. 2010. Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index NATURE GENETICS, 42 (11), pp. 937-U53. | Show Abstract | Read more

Obesity is globaLy prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined aSociations betwEn body maS index and ĝ̂1/42.8 miLion SNPs in up to 123,865 individuals with targeted foLow up of 42 SNPs in up to 125,931 aDitional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci aSociated with body maS index (P < 5-10-8), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly aSociated loci may provide new insights into human body weight regulation. © 2010 Nature America, Inc. All rights reserved.

Fischer A, Ten Hove M, Sebag-Montefiore L, Wagner H, Clarke K, Watkins H, Lygate CA, Neubauer S. 2010. Changes in creatine transporter function during cardiac maturation in the rat. BMC Dev Biol, 10 (1), pp. 70. | Show Abstract | Read more

BACKGROUND: It is well established that the immature myocardium preferentially utilises non-oxidative energy-generating pathways. It exhibits low energy-transfer capacity via the creatine kinase (CK) shuttle, reflected in phosphocreatine (PCr), total creatine and CK levels that are much lower than those of adult myocardium. The mechanisms leading to gradually increasing energy transfer capacity during maturation are poorly understood. Creatine is not synthesised in the heart, but taken up exclusively by the action of the creatine transporter protein (CrT). To determine whether this transporter is ontogenically regulated, the present study serially examined CrT gene expression pattern, together with creatine uptake kinetics and resulting myocardial creatine levels, in rats over the first 80 days of age. RESULTS: Rats were studied during the late prenatal period (-2 days before birth) and 7, 13, 21, 33, 50 and 80 days after birth. Activity of cardiac citrate synthase, creatine kinase and its isoenzymes as well as lactate dehydrogenase (LDH) and its isoenzymes demonstrated the well-described shift from anaerobic towards aerobic metabolism. mRNA levels of CrT in the foetal rat hearts, as determined by real-time PCR, were about 30% of the mRNA levels in the adult rat heart and gradually increased during development. Creatine uptake in isolated perfused rat hearts increased significantly from 3.0 nmol/min/gww at 13 days old to 4.9 nmol/min/gww in 80 day old rats. Accordingly, total creatine content in hearts, measured by HPLC, increased steadily during maturation (30 nmol/mg protein (-2 days) vs 87 nmol/mg protein (80 days)), and correlated closely with CrT gene expression. CONCLUSIONS: The maturation-dependant alterations of CK and LDH isoenzyme activities and of mitochondrial oxidative capacity were paralleled by a progressive increase of CrT expression, creatine uptake kinetics and creatine content in the heart.

Vickers AJ, Eastham JA, Scardino PT, Lilja H. 2016. Author Reply. Urology, 91 (12), pp. 17-18. | Read more

Robinson PJ, Zhang YH, Casadei B, Watkins H, Redwood C. 2010. Investigating the Effect of Cardiomyopathy-Causing Mutations in Cardiac Troponin-T on Calcium Buffering In Situ BIOPHYSICAL JOURNAL, 98 (3), pp. 352A-352A.

Griffiths PJ, Isackson H, Redwood CS, Watkins H, Ashley CC. 2010. Force, Ca-Sensitivity and Contractile Efficiency in Human Myocardium Expressing a Truncated Cardiac Myosin Binding Protein-C BIOPHYSICAL JOURNAL, 98 (3), pp. 554A-554A.

Clarke R, Peden JF, Hopewell JC, Kyriakou T, Goel A, Heath SC, Parish S, Barlera S, Franzosi MG, Rust S et al. 2009. Genetic variants associated with Lp(a) lipoprotein level and coronary disease. N Engl J Med, 361 (26), pp. 2518-2528. | Show Abstract | Read more

BACKGROUND: An increased level of Lp(a) lipoprotein has been identified as a risk factor for coronary artery disease that is highly heritable. The genetic determinants of the Lp(a) lipoprotein level and their relevance for the risk of coronary disease are incompletely understood. METHODS: We used a novel gene chip containing 48,742 single-nucleotide polymorphisms (SNPs) in 2100 candidate genes to test for associations in 3145 case subjects with coronary disease and 3352 control subjects. Replication was tested in three independent populations involving 4846 additional case subjects with coronary disease and 4594 control subjects. RESULTS: Three chromosomal regions (6q26-27, 9p21, and 1p13) were strongly associated with the risk of coronary disease. The LPA locus on 6q26-27 encoding Lp(a) lipoprotein had the strongest association. We identified a common variant (rs10455872) at the LPA locus with an odds ratio for coronary disease of 1.70 (95% confidence interval [CI], 1.49 to 1.95) and another independent variant (rs3798220) with an odds ratio of 1.92 (95% CI, 1.48 to 2.49). Both variants were strongly associated with an increased level of Lp(a) lipoprotein, a reduced copy number in LPA (which determines the number of kringle IV-type 2 repeats), and a small Lp(a) lipoprotein size. Replication studies confirmed the effects of both variants on the Lp(a) lipoprotein level and the risk of coronary disease. A meta-analysis showed that with a genotype score involving both LPA SNPs, the odds ratios for coronary disease were 1.51 (95% CI, 1.38 to 1.66) for one variant and 2.57 (95% CI, 1.80 to 3.67) for two or more variants. After adjustment for the Lp(a) lipoprotein level, the association between the LPA genotype score and the risk of coronary disease was abolished. CONCLUSIONS: We identified two LPA variants that were strongly associated with both an increased level of Lp(a) lipoprotein and an increased risk of coronary disease. Our findings provide support for a causal role of Lp(a) lipoprotein in coronary disease.

Hudsmith LE, Tyler DJ, Emmanuel Y, Petersen SE, Francis JM, Watkins H, Clarke K, Robson MD, Neubauer S. 2009. (31)P cardiac magnetic resonance spectroscopy during leg exercise at 3 Tesla. Int J Cardiovasc Imaging, 25 (8), pp. 819-826. | Show Abstract | Read more

Investigation of phosphorus ((31)P) magnetic resonance spectroscopy under stress conditions provides a non-invasive tool to examine alterations in cardiac high-energy phosphate metabolism that may not be evident at rest. Our aim was to establish cardiac (31)P MR spectroscopy during leg exercise at 3T. The increased field strength should provide a higher signal to noise ratio than at lower field strengths. Furthermore, relatively high temporal resolution at a sufficiently fine spatial resolution should be feasible. (31)P MR spectra were obtained with a 3D acquisition weighted chemical shift imaging sequence in 20 healthy volunteers at rest, during dynamic physiological leg exercise and after recovery at 3T. Haemodynamic measurements were made throughout and the rate pressure product calculated. With exercise, the mean heart rate increased by 73%, achieving a mean increase in rate pressure product of 115%. The corrected PCr/ATP ratio for subjects at rest was 2.02 +/- 0.43, exercise 2.14 +/- 0.67 (P = 0.54 vs. rest) and at recovery 2.03 +/- 0.52 (P = 0.91 vs. rest, P = 0.62 vs. exercise). A cardiac (31)P MR spectroscopy physiological exercise-recovery protocol is feasible at 3T. There was no significant change in high-energy cardiac phosphate metabolite concentrations in healthy volunteers at rest, during physiological leg exercise or during recovery. When applied to patients with heart disease, this protocol should provide insights into physiological and pathological cardiac metabolism.

Griffiths PJ, Isackson H, Pelc R, Redwood CS, Funari SS, Watkins H, Ashley CC. 2009. Synchronous in situ ATPase activity, mechanics, and Ca2+ sensitivity of human and porcine myocardium. Biophys J, 97 (9), pp. 2503-2512. | Show Abstract | Read more

Flash-frozen myocardium samples provide a valuable means of correlating clinical cardiomyopathies with abnormalities in sarcomeric contractile and biochemical parameters. We examined flash-frozen left-ventricle human cardiomyocyte bundles from healthy donors to determine control parameters for isometric tension (P(o)) development and Ca(2+) sensitivity, while simultaneously measuring actomyosin ATPase activity in situ by a fluorimetric technique. P(o) was 17 kN m(-2) and pCa(50%) was 5.99 (28 degrees C, I = 130 mM). ATPase activity increased linearly with tension to 132 muM s(-1). To determine the influence of flash-freezing, we compared the same parameters in both glycerinated and flash-frozen porcine left-ventricle trabeculae. P(o) in glycerinated porcine myocardium was 25 kN m(-2), and maximum ATPase activity was 183 microM s(-1). In flash-frozen porcine myocardium, P(o) was 16 kN m(-2) and maximum ATPase activity was 207 microM s(-1). pCa(50%) was 5.77 in the glycerinated and 5.83 in the flash-frozen sample. Both passive and active stiffness of flash-frozen porcine myocardium were lower than for glycerinated tissue and similar to the human samples. Although lower stiffness and isometric tension development may indicate flash-freezing impairment of axial force transmission, we cannot exclude variability between samples as the cause. ATPase activity and pCa(50%) were unaffected by flash-freezing. The lower ATPase activity measured in human tissue suggests a slower actomyosin turnover by the contractile proteins.

Alvarez-Madrazo S, Padmanabhan S, Mayosi BM, Watkins H, Avery P, Wallace AM, Fraser R, Davies E, Keavney B, Connell JM. 2009. Familial and phenotypic associations of the aldosterone Renin ratio. J Clin Endocrinol Metab, 94 (11), pp. 4324-4333. | Show Abstract | Read more

CONTEXT: The aldosterone to renin ratio (ARR) is a marker of aldosterone excess, widely used to screen for primary aldosteronism (PA). The significance of a raised ARR in normotensive and hypertensive subjects and the phenotypic and familial factors affecting it are unclear. OBJECTIVE: We estimated the distribution and heritability of the ARR and tested for associations between ARR and blood pressure (BP) with 11 polymorphisms at the CYP11B1/CYP11B2 locus. DESIGN AND SETTING: A total of 1172 individuals from 248 Caucasian families ascertained via a hypertensive proband were evaluated. MAIN OUTCOME MEASURE: Plasma aldosterone was measured by RIA, and plasma renin concentration was measured by the LIAISON Direct Renin chemiluminescent immunoassay. RESULTS: Unadjusted and adjusted ARR were continuously distributed in normotensives and hypertensives, with no evidence of a cutoff that would identify a separate population with PA. Median ARR was 4.19 ng/liter per mIU/liter (range, 0.04-253.16). ARR levels were higher in females and associated with age, body mass index, and potassium. Antihypertensive agents had significant predictable effects on the ARR. Renin was negatively associated, and ARR was positively associated with ambulatory BP readings (P < 0.001) in subjects not taking antihypertensives. The heritability of the ARR was 38.1% (P < 10(-8)). Plasma aldosterone, but not ARR, was influenced by the intron 2 conversion variation in the CYP11B2 gene (beta = -0.07; P = 0.04). CONCLUSIONS: The ARR is continuously distributed, is influenced by genetic and environmental factors, and is not a marker of a distinct pathological abnormality but possibly reflects the long-term influence of aldosterone on cardiovascular homeostasis.

Parker M, Kinnear C, Keavney B, Watkins H, Mayosi BM, Moolman-Smook J. 2009. The growth hormone inducible transmembrane gene is a novel genetic modifier of left ventricular hypertrophy in families with hypertrophic cardiomyopathy EUROPEAN HEART JOURNAL, 30 pp. 542-542.

Ormerod JOM, Ashrafian H, Steeples V, Egginton S, Watkins H, Frenneaux MP. 2009. Myoglobin is involved in vasodilatation by nitrite EUROPEAN HEART JOURNAL, 30 pp. 648-648.

Abozguia K, Phan TT, Ahmed I, Shivu GN, Maher AR, Kalra R, Mckenna W, Watkins H, Elliott PM, Frenneaux MP. 2009. Cardiac energetic impairment in non-obstructive hypertrophic cardiomyopathy: relation to exercise capacity and dynamic diastolic dysfunction EUROPEAN HEART JOURNAL, 30 pp. 255-255.

Carballo S, Robinson P, Otway R, Fatkin D, Jongbloed JD, de Jonge N, Blair E, van Tintelen JP, Redwood C, Watkins H. 2009. Identification and functional characterization of cardiac troponin I as a novel disease gene in autosomal dominant dilated cardiomyopathy. Circ Res, 105 (4), pp. 375-382. | Show Abstract | Read more

RATIONALE: Idiopathic dilated cardiomyopathy (DCM) is inherited in approximately one third of cases, usually as an autosomal dominant trait. More than 30 loci have been identified, several of which encode sarcomeric proteins which can also be mutated to cause hypertrophic cardiomyopathy. One contractile protein gene well known as a hypertrophic cardiomyopathy disease gene, but with no reported mutation in autosomal dominant DCM, is TNNI3 which encodes cardiac troponin I. OBJECTIVE: To test TNNI3 as a candidate gene, a panel of 96 probands with DCM was analyzed. METHODS AND RESULTS: Genomic DNA was isolated and TNNI3 exons screened by heteroduplex analysis. Exons with aberrant profiles were sequenced and variants evaluated by segregation analysis and study of normal controls. We report 2 novel TNNI3 missense mutations, Lys36Gln and Asn185Lys, each associated with severe and early onset familial DCM. Of the 5 mutation carriers, cardiac transplantation was required in 3, at ages 6, 15, and 24 years. Analysis of Ca(2+) regulation of actin-tropomyosin-activated myosin ATPase by troponin revealed that troponin reconstituted with either mutant troponin I gave lower maximum ATPase rates and lower Ca(2+) sensitivity than wild type. Furthermore, mutant thin filaments had reduced Ca(2+) affinity compared with normal. CONCLUSIONS: The functional alterations mirror closely a consistent phenotype found in proven DCM mutations in other thin filament proteins, thus supporting the interpretation that these mutations are disease-causing. These are the first reported autosomal dominant DCM-causing mutations in TNNI3, and so the findings expand the spectrum of disease-causing genes that lead to either hypertrophic cardiomyopathy or DCM depending on the specific mutation.

Mälarstig A, Buil A, Souto JC, Clarke R, Blanco-Vaca F, Fontcuberta J, Peden J, Andersen M, Silveira A, Barlera S et al. 2009. Identification of ZNF366 and PTPRD as novel determinants of plasma homocysteine in a family-based genome-wide association study. Blood, 114 (7), pp. 1417-1422. | Show Abstract | Read more

Total plasma homocysteine concentration (tHcy) is a biomarker for atherothrombotic disease, but causality remains uncertain. Polymorphisms in the genes involved in methionine metabolism explain only a small fraction of the heritability of tHcy levels. In a genome-wide association study, we examined the genetic determinants of tHcy using a 2-stage design. First, 283 437 single nucleotide polymorphisms (SNPs) were tested for association with tHcy in 387 persons recruited from 21 large Spanish families. Of those, 17 SNPs showed equal or stronger association with tHcy level compared with the MTHFR 677C>T SNP (beta = 0.10, P = .0001). Second, a replication analysis of these 17 SNPs was performed in patients with premature myocardial infarction (n = 1238). Novel associations were found for SNPs near the ZNF366 gene (lead SNP rs7445013; discovery stage: adjusted beta = -0.12, P = 5.30 x 10(-6), replication stage: adjusted beta = -0.13, P = .004) and the PTPRD gene (lead SNP rs973117; discovery stage: adjusted beta = 0.11, P = 5.5 x 10(-6), replication stage: adjusted beta = 0.10, P = .005). These associations were independent of known confounders, including creatinine clearance and plasma fibrinogen concentration. Our findings implicate novel pathways in homocysteine metabolism, and highlight the need for investigation of the associated genes in the etiology of vascular diseases.

Renz B, Davies JK, Carling D, Watkins H, Redwood C. 2009. Determination of AMP-activated protein kinase phosphorylation sites in recombinant protein expressed using the pET28a vector: a cautionary tale. Protein Expr Purif, 66 (2), pp. 181-184. | Show Abstract | Read more

AMP-activated protein kinase (AMPK) is responsible for sensing of the cell's energetic status and it phosphorylates numerous substrates involved in anabolic and catabolic processes as well as interacting with signaling cascades. Mutations in the gene encoding the gamma 2 regulatory subunit have been shown to cause hypertrophic cardiomyopathy (HCM) with conduction abnormalities. As part of a study to examine the role of AMPK in the heart, we tested whether specific domains of the thick filament component cardiac myosin binding protein-C (cMyBP-C) were good in vitro AMPK substrates. The commercially available pET28a expression vector was used to generate a recombinant form of the cMyBP-C C8 domain as a fusion protein with a hexahistidine tag. In vitro phosphorylation with activated kinase showed that the purified fusion protein was a good AMPK substrate, phosphorylated at a similar rate to the control SAMS peptide and with phosphate incorporation specifically in serine residues. However, subsequent analysis of alanine replacement mutants and thrombin digestion revealed that the strong AMPK phosphorylation site was contained within the thrombin cleavage sequence encoded by the vector. As this sequence is common to many commercial pET vectors, caution is advised in the mapping of AMPK phosphorylation sites when this sequence is present.

Marston S, Copeland O, Jacques A, Livesey K, Tsang V, McKenna WJ, Jalilzadeh S, Carballo S, Redwood C, Watkins H. 2009. Evidence from human myectomy samples that MYBPC3 mutations cause hypertrophic cardiomyopathy through haploinsufficiency. Circ Res, 105 (3), pp. 219-222. | Show Abstract | Read more

RATIONALE: Most sarcomere gene mutations that cause hypertrophic cardiomyopathy are missense alleles that encode dominant negative proteins. The potential exceptions are mutations in the MYBPC3 gene (encoding cardiac myosin-binding protein-C [MyBP-C]), which frequently encode truncated proteins. OBJECTIVE: We sought to determine whether there was evidence of haploinsufficiency in hypertrophic cardiomyopathy caused by MYBPC3 mutations by comparing left ventricular muscle from patients undergoing surgical myectomy with samples from donor hearts. METHODS AND RESULTS: MyBP-C protein and mRNA levels were quantitated using immunoblotting and RT-PCR. Nine of 37 myectomy samples had mutations in MYBPC3: 2 missense alleles (Glu258Lys, Arg502Trp) and 7 premature terminations. No specific truncated MyBP-C peptides were detected in whole muscle homogenates of hypertrophic cardiomyopathy tissue. However, the overall level of MyBP-C in myofibrils was significantly reduced (P<0.0005) in tissue containing either a truncation or missense MYBPC3 mutation: 0.76+/-0.03 compared with 1.00+/-0.05 in donor and 1.01+/-0.06 in non-MYBPC3 mutant myectomies. CONCLUSIONS: The absence of any detectable truncated MyBP-C argues against its incorporation in the myofiber and any dominant negative effect. In contrast, the lowered relative level of full length protein in both truncation and missense MYBPC3 mutations argues strongly that haploinsufficiency is sufficient to cause the disease.

Elliott P, Chambers JC, Zhang W, Clarke R, Hopewell JC, Peden JF, Erdmann J, Braund P, Engert JC, Bennett D et al. 2009. Genetic Loci associated with C-reactive protein levels and risk of coronary heart disease. JAMA, 302 (1), pp. 37-48. | Show Abstract | Read more

CONTEXT: Plasma levels of C-reactive protein (CRP) are independently associated with risk of coronary heart disease, but whether CRP is causally associated with coronary heart disease or merely a marker of underlying atherosclerosis is uncertain. OBJECTIVE: To investigate association of genetic loci with CRP levels and risk of coronary heart disease. DESIGN, SETTING, AND PARTICIPANTS: We first carried out a genome-wide association (n = 17,967) and replication study (n = 13,615) to identify genetic loci associated with plasma CRP concentrations. Data collection took place between 1989 and 2008 and genotyping between 2003 and 2008. We carried out a mendelian randomization study of the most closely associated single-nucleotide polymorphism (SNP) in the CRP locus and published data on other CRP variants involving a total of 28,112 cases and 100,823 controls, to investigate the association of CRP variants with coronary heart disease. We compared our finding with that predicted from meta-analysis of observational studies of CRP levels and risk of coronary heart disease. For the other loci associated with CRP levels, we selected the most closely associated SNP for testing against coronary heart disease among 14,365 cases and 32,069 controls. MAIN OUTCOME MEASURE: Risk of coronary heart disease. RESULTS: Polymorphisms in 5 genetic loci were strongly associated with CRP levels (% difference per minor allele): SNP rs6700896 in LEPR (-14.8%; 95% confidence interval [CI], -17.6% to -12.0%; P = 6.2 x 10(-22)), rs4537545 in IL6R (-11.5%; 95% CI, -14.4% to -8.5%; P = 1.3 x 10(-12)), rs7553007 in the CRP locus (-20.7%; 95% CI, -23.4% to -17.9%; P = 1.3 x 10(-38)), rs1183910 in HNF1A (-13.8%; 95% CI, -16.6% to -10.9%; P = 1.9 x 10(-18)), and rs4420638 in APOE-CI-CII (-21.8%; 95% CI, -25.3% to -18.1%; P = 8.1 x 10(-26)). Association of SNP rs7553007 in the CRP locus with coronary heart disease gave an odds ratio (OR) of 0.98 (95% CI, 0.94 to 1.01) per 20% lower CRP level. Our mendelian randomization study of variants in the CRP locus showed no association with coronary heart disease: OR, 1.00; 95% CI, 0.97 to 1.02; per 20% lower CRP level, compared with OR, 0.94; 95% CI, 0.94 to 0.95; predicted from meta-analysis of the observational studies of CRP levels and coronary heart disease (z score, -3.45; P < .001). SNPs rs6700896 in LEPR (OR, 1.06; 95% CI, 1.02 to 1.09; per minor allele), rs4537545 in IL6R (OR, 0.94; 95% CI, 0.91 to 0.97), and rs4420638 in the APOE-CI-CII cluster (OR, 1.16; 95% CI, 1.12 to 1.21) were all associated with risk of coronary heart disease. CONCLUSION: The lack of concordance between the effect on coronary heart disease risk of CRP genotypes and CRP levels argues against a causal association of CRP with coronary heart disease.

Lindgren CM, Heid IM, Randall JC, Lamina C, Steinthorsdottir V, Qi L, Speliotes EK, Thorleifsson G, Willer CJ, Herrera BM et al. 2009. Genome-wide association scan meta-analysis identifies three Loci influencing adiposity and fat distribution. PLoS Genet, 5 (6), pp. e1000508. | Show Abstract | Read more

To identify genetic loci influencing central obesity and fat distribution, we performed a meta-analysis of 16 genome-wide association studies (GWAS, N = 38,580) informative for adult waist circumference (WC) and waist-hip ratio (WHR). We selected 26 SNPs for follow-up, for which the evidence of association with measures of central adiposity (WC and/or WHR) was strong and disproportionate to that for overall adiposity or height. Follow-up studies in a maximum of 70,689 individuals identified two loci strongly associated with measures of central adiposity; these map near TFAP2B (WC, P = 1.9x10(-11)) and MSRA (WC, P = 8.9x10(-9)). A third locus, near LYPLAL1, was associated with WHR in women only (P = 2.6x10(-8)). The variants near TFAP2B appear to influence central adiposity through an effect on overall obesity/fat-mass, whereas LYPLAL1 displays a strong female-only association with fat distribution. By focusing on anthropometric measures of central obesity and fat distribution, we have identified three loci implicated in the regulation of human adiposity.

Newton-Cheh C, Johnson T, Gateva V, Tobin MD, Bochud M, Coin L, Najjar SS, Zhao JH, Heath SC, Eyheramendy S et al. 2009. Genome-wide association study identifies eight loci associated with blood pressure. Nat Genet, 41 (6), pp. 666-676. | Show Abstract | Read more

Elevated blood pressure is a common, heritable cause of cardiovascular disease worldwide. To date, identification of common genetic variants influencing blood pressure has proven challenging. We tested 2.5 million genotyped and imputed SNPs for association with systolic and diastolic blood pressure in 34,433 subjects of European ancestry from the Global BPgen consortium and followed up findings with direct genotyping (N ≤ 71,225 European ancestry, N ≤ 12,889 Indian Asian ancestry) and in silico comparison (CHARGE consortium, N = 29,136). We identified association between systolic or diastolic blood pressure and common variants in eight regions near the CYP17A1 (P = 7 × 10(-24)), CYP1A2 (P = 1 × 10(-23)), FGF5 (P = 1 × 10(-21)), SH2B3 (P = 3 × 10(-18)), MTHFR (P = 2 × 10(-13)), c10orf107 (P = 1 × 10(-9)), ZNF652 (P = 5 × 10(-9)) and PLCD3 (P = 1 × 10(-8)) genes. All variants associated with continuous blood pressure were associated with dichotomous hypertension. These associations between common variants and blood pressure and hypertension offer mechanistic insights into the regulation of blood pressure and may point to novel targets for interventions to prevent cardiovascular disease.

Kolz M, Johnson T, Sanna S, Teumer A, Vitart V, Perola M, Mangino M, Albrecht E, Wallace C, Farrall M et al. 2009. Meta-analysis of 28,141 individuals identifies common variants within five new loci that influence uric acid concentrations. PLoS Genet, 5 (6), pp. e1000504. | Show Abstract | Read more

Elevated serum uric acid levels cause gout and are a risk factor for cardiovascular disease and diabetes. To investigate the polygenetic basis of serum uric acid levels, we conducted a meta-analysis of genome-wide association scans from 14 studies totalling 28,141 participants of European descent, resulting in identification of 954 SNPs distributed across nine loci that exceeded the threshold of genome-wide significance, five of which are novel. Overall, the common variants associated with serum uric acid levels fall in the following nine regions: SLC2A9 (p = 5.2x10(-201)), ABCG2 (p = 3.1x10(-26)), SLC17A1 (p = 3.0x10(-14)), SLC22A11 (p = 6.7x10(-14)), SLC22A12 (p = 2.0x10(-9)), SLC16A9 (p = 1.1x10(-8)), GCKR (p = 1.4x10(-9)), LRRC16A (p = 8.5x10(-9)), and near PDZK1 (p = 2.7x10(-9)). Identified variants were analyzed for gender differences. We found that the minor allele for rs734553 in SLC2A9 has greater influence in lowering uric acid levels in women and the minor allele of rs2231142 in ABCG2 elevates uric acid levels more strongly in men compared to women. To further characterize the identified variants, we analyzed their association with a panel of metabolites. rs12356193 within SLC16A9 was associated with DL-carnitine (p = 4.0x10(-26)) and propionyl-L-carnitine (p = 5.0x10(-8)) concentrations, which in turn were associated with serum UA levels (p = 1.4x10(-57) and p = 8.1x10(-54), respectively), forming a triangle between SNP, metabolites, and UA levels. Taken together, these associations highlight additional pathways that are important in the regulation of serum uric acid levels and point toward novel potential targets for pharmacological intervention to prevent or treat hyperuricemia. In addition, these findings strongly support the hypothesis that transport proteins are key in regulating serum uric acid levels.

Paré G, Chasman DI, Parker AN, Zee RR, Mälarstig A, Seedorf U, Collins R, Watkins H, Hamsten A, Miletich JP, Ridker PM. 2009. Novel associations of CPS1, MUT, NOX4, and DPEP1 with plasma homocysteine in a healthy population: a genome-wide evaluation of 13 974 participants in the Women's Genome Health Study. Circ Cardiovasc Genet, 2 (2), pp. 142-150. | Show Abstract | Read more

BACKGROUND: Homocysteine is a sulfur amino acid whose plasma concentration has been associated with the risk of cardiovascular diseases, neural tube defects, and loss of cognitive function in epidemiological studies. Although genetic variants of MTHFR and CBS are known to influence homocysteine concentration, common genetic determinants of homocysteine remain largely unknown. METHODS AND RESULTS: To address this issue comprehensively, we performed a genome-wide association analysis, testing 336 469 single-nucleotide polymorphisms in 13 974 healthy white women. Although we confirm association with MTHFR (1p36.22; rs1801133; P=8.1 x 10(-35)) and CBS (21q22.3; rs6586282; P=3.2 x 10(-10)), we found novel associations with CPS1 (2q34; rs7422339; P=1.9 x 10(-11)), MUT (6p12.3; rs4267943; P=2.0 x 10(-9)), NOX4 (11q14.3; rs11018628; P=9.6 x 10(-12)), and DPEP1 (16q24.3; rs1126464; P=1.2 x 10(-12)). The associations at MTHFR, DPEP1, and CBS were replicated in an independent sample from the PROCARDIS study, whereas the association at CPS1 was only replicated among the women. CONCLUSIONS: These associations offer new insight into the biochemical pathways involved in homocysteine metabolism and provide opportunities to better delineate the role of homocysteine in health and disease.

Petersen SE, Watkins H, Neubauer S. 2009. Impaired left ventricular energy metabolism in hypertrophic cardiomyopathy is not due to fibrosis. Heart, 95 (6), pp. 505.

Cunnington MS, Mayosi BM, Hall DH, Avery PJ, Farrall M, Vickers MA, Watkins H, Keavney B. 2009. Novel genetic variants linked to coronary artery disease by genome-wide association are not associated with carotid artery intima-media thickness or intermediate risk phenotypes. Atherosclerosis, 203 (1), pp. 41-44. | Show Abstract | Read more

BACKGROUND: It is uncertain whether the novel single nucleotide polymorphisms (SNPs) that have recently been associated with coronary artery disease (CAD) in genome-wide studies also influence carotid atheroma and stroke risk. The mechanisms of their association with CAD are unknown; relationships to other cardiovascular phenotypes may give mechanistic clues. Carotid artery intima-media thickness (CIMT) is a subclinical marker of atherosclerosis associated with stroke. We investigated association of reported CAD risk variants with CIMT, and with other intermediate phenotypes that may implicate causative pathways. METHODS: We studied 1425 members of 248 British Caucasian families ascertained through a hypertensive proband. We genotyped CAD risk SNPs on chromosomes 9 (rs1333049, rs7044859, rs496892, rs7865618), 6 (rs6922269) and 2 (rs2943634) using TaqMan. Merlin software was used for family-based association testing. RESULTS: No significant association was found between genotype at any SNP and CIMT in 846 individuals with acceptable measurements. Nor were SNPs significantly associated with blood pressure, obesity, cholesterol, CRP, interleukin-6, TNF-alpha, or leptin. CONCLUSIONS: These novel CAD variants are not associated with CIMT and do not appear to mediate the risk of atherothrombosis through known risk factors.

Folkersen L, Kyriakou T, Goel A, Peden J, Mälarstig A, Paulsson-Berne G, Hamsten A, Hugh Watkins, Franco-Cereceda A, Gabrielsen A et al. 2009. Relationship between CAD risk genotype in the chromosome 9p21 locus and gene expression. Identification of eight new ANRIL splice variants. PLoS One, 4 (11), pp. e7677. | Show Abstract | Read more

BACKGROUND: Several genome-wide association studies have recently linked a group of single nucleotide polymorphisms in the 9p21 region with cardiovascular disease. The molecular mechanisms of this link are not fully understood. We investigated five different expression microarray datasets in order to determine if the genotype had effect on expression of any gene transcript in aorta, mammary artery, carotid plaque and lymphoblastoid cells. METHODOLOGY/PRINCIPAL FINDINGS: After multiple testing correction, no genes were found to have relation to the rs2891168 risk genotype, either on a genome-wide scale or on a regional (8 MB) scale. The neighbouring ANRIL gene was found to have eight novel transcript variants not previously known from literature and these varied by tissue type. We therefore performed a detailed probe-level analysis and found small stretches of significant relation to genotype but no consistent associations. In all investigated tissues we found an inverse correlation between ANRIL and the MTAP gene and a positive correlation between ANRIL and CDKN2A and CDKN2B. CONCLUSIONS/SIGNIFICANCE: Investigation of relation of the risk genotype to gene expression is complicated by the transcript complexity of the locus. With our investigation of a range of relevant tissue we wish to underscore the need for careful attention to the complexity of the alternative splicing issues in the region and its implications to the design of future gene expression studies.

Palomino-Doza J, Rahman TJ, Avery PJ, Mayosi BM, Farrall M, Watkins H, Edwards CR, Keavney B. 2008. Ambulatory blood pressure is associated with polymorphic variation in P2X receptor genes. Hypertension, 52 (5), pp. 980-985. | Show Abstract | Read more

The P2X receptor gene family encodes a series of proteins that function as ATP-gated nonselective ion channels. P2X receptor channels are involved in transducing aldosterone-mediated signaling in the distal renal tubule and are potential candidate genes for blood pressure regulation. We performed a family based quantitative genetic association study in 248 families ascertained through a proband with hypertension to investigate the relationship between common genetic variation in the P2X4, P2X6, and P2X7 genes and ambulatory blood pressure. We genotyped 28 single nucleotide polymorphisms, which together captured the common genetic variability in the 3 genes. We corrected our results for multiple comparisons specifying a false discovery rate of 5%. We found significant evidence of association between the single nucleotide polymorphism rs591874 in the first intron of the P2X7 gene and blood pressure. The strongest association was found for nighttime diastolic blood pressure (P=0.0032), although association was present for both systolic and diastolic blood pressures measured by an observer during the day and at night. Genotypes were associated with a 0.2 SD ( approximately 2.5 mm Hg) difference in night diastolic blood pressure per allele and accounted for approximately 1% of the total variability in this measurement. Other suggestive associations were found, but these were nonsignificant after correction for multiple testing. These genetic data suggest that drugs affecting P2X receptor signaling may have promise as clinical antihypertensive agents.

Ashrafian H, Watkins H. 2008. Exercise-induced ventricular dysfunction in hypertrophic cardiomyopathy: stunning by any other name? Heart, 94 (10), pp. 1251-1253. | Read more

Watkins H, Ashrafian H, McKenna WJ. 2008. The genetics of hypertrophic cardiomyopathy: Teare redux. Heart, 94 (10), pp. 1264-1268. | Read more

Figtree GA, Grieve SM, Speller B, Geiger MJ, Robinson BG, Channon KM, Ragoussis J, Collins P, Watkins H. 2008. A commonly occurring polymorphism upstream of the estrogen receptor alpha alters transcription and is associated with increased HDL. Atherosclerosis, 199 (2), pp. 354-361. | Show Abstract | Read more

OBJECTIVE: Given the role of estrogen in the regulation of lipid metabolism, we screened for functional polymorphisms in the estrogen receptor alpha (ER*), and examined for their influence on serum cholesterol. METHODS AND RESULTS: We identified a novel C>T polymorphism (ERNE-145), with a minor allele frequency of 41%. This polymorphism was immediately adjacent to a putative glucocorticoid receptor (GR) binding site, which we showed to be functional by electrophoretic mobility shift analysis. The C allele was associated with glucocorticoid-induced reduction in promoter activity compared to control in luciferase reporter studies (p<0.05; n=7). This effect was abolished by the T allele. To investigate the functional significance of ERNE-145, its association with serum cholesterol levels was examined in 1662 post-menopausal women enrolled in the RUTH trial. ERNE-145 genotype (p=0.001), BMI (p<0.001), diabetes mellitus (p<0.001), and ethnicity (p=0.002) were significantly associated with HDL cholesterol. ERNE-145 genotype explained 8.2% of the variability of HDL: each copy of the variant T allele was associated with a 0.041 mmol/L (CI 0.017-0.066) increase in HDL. CONCLUSION: A novel polymorphism upstream of ER* abolished negative transcriptional regulation by an adjacent GR binding sequence, and was strongly associated with HDL levels in a large cohort of post-menopausal women.

Broadbent HM, Peden JF, Lorkowski S, Goel A, Ongen H, Green F, Clarke R, Collins R, Franzosi MG, Tognoni G et al. 2008. Susceptibility to coronary artery disease and diabetes is encoded by distinct, tightly linked SNPs in the ANRIL locus on chromosome 9p. Hum Mol Genet, 17 (6), pp. 806-814. | Show Abstract | Read more

Genome-wide association studies have identified a region on chromosome 9p that is associated with coronary artery disease (CAD). The region is also associated with type 2 diabetes (T2D), a risk factor for CAD, although different SNPs were reported to be associated to each disease in separate studies. We have undertaken a case-control study in 4251 CAD cases and 4443 controls in four European populations using previously reported ('literature') and tagging SNPs. We replicated the literature SNPs (P = 8x10(-13); OR = 1.29; 95% CI: 1.20-1.38) and showed that the strong consistent association detected by these SNPs is a consequence of a 'yin-yang' haplotype pattern spanning 53 kb. There was no evidence of additional CAD susceptibility alleles over the major risk haplotype. CAD patients without myocardial infarction (MI) showed a trend towards stronger association than MI patients. The CAD susceptibility conferred by this locus did not differ by sex, age, smoking, obesity, hypertension or diabetes. A simultaneous test of CAD and diabetes susceptibility with CAD and T2D-associated SNPs indicated that these associations were independent of each other. Moreover, this region was not associated with differences in plasma levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fibrinogen, albumin, uric acid, bilirubin or homocysteine, although the CAD-high-risk allele was paradoxically associated with lower triglyceride levels. A large antisense non-coding RNA gene (ANRIL) collocates with the high-risk haplotype, is expressed in tissues and cell types that are affected by atherosclerosis and is a prime candidate gene for the chromosome 9p CAD locus.

Flashman E, Korkie L, Watkins H, Redwood C, Moolman-Smook JC. 2008. Support for a trimeric collar of myosin binding protein C in cardiac and fast skeletal muscle, but not in slow skeletal muscle. FEBS Lett, 582 (3), pp. 434-438. | Show Abstract | Read more

Myosin-binding protein C (MyBPC) is proposed to take on a trimeric collar arrangement around the thick filament backbone in cardiac muscle, based on interactions between cardiac MyBPC domains C5 and C8. We have now determined, using yeast two-hybrid and in vitro binding assays, that the C5:C8 interaction is not dependent on the 28-residue cardiac-specific insert in C5. Furthermore, an interaction of similar affinity occurs between domains C5 and C8 of fast skeletal muscle MyBPC, but not between these domains of the slow skeletal muscle protein. These data have implications for the role and quaternary structure of MyBPC in skeletal muscle.

Mayosi BM, Avery PJ, Farrall M, Keavney B, Watkins H. 2008. Genome-wide linkage analysis of electrocardiographic and echocardiographic left ventricular hypertrophy in families with hypertension. Eur Heart J, 29 (4), pp. 525-530. | Show Abstract | Read more

AIMS: To localize chromosomal regions (or quantitative trait loci) that harbour genetic variants influencing the variability of electrocardiographic (ECG) and echocardiographic left ventricular hypertrophy (LVH). METHODS AND RESULTS: We evaluated genetic linkage to ECG Sokolow-Lyon voltage, ECG Cornell voltage product, ECG left ventricular (LV) mass, and to echocardiographic septal wall thickness, LV cavity size, and LV mass in 868 members of 224 white British families. A genome-wide scan was performed with microsatellite markers that covered the genome at 10-cM intervals and linkage was assessed by variance components analysis. We identified chromosomal regions suggestive of linkage for Sokolow-Lyon voltage on chromosome 10q23.1 [log(10) of the odds (LOD = 2.21, P = 0.0007)], for ECG Cornell voltage product on chromosome 17p13.3 (LOD = 2.67; P = 0.0002), and for ECG LV mass on chromosome 12q14.1 (LOD = 2.19; P = 0.0007). There was a single region of possible linkage for echocardiographic LV mass on chromosome 5p14.1 (LOD = 1.6; P = 0.003). CONCLUSION: Stronger genetic signals for LVH were found using electrocardiographic than echocardiographic measurements, and the genetic determinants of each of these appear to be distinct. Chromosomes 10, 12, and 17 are likely to harbour genetic loci that exert a major influence on electrocardiographic LVH.

Schneider JE, Stork LA, Bell JT, ten Hove M, Isbrandt D, Clarke K, Watkins H, Lygate CA, Neubauer S. 2008. Cardiac structure and function during ageing in energetically compromised Guanidinoacetate N-methyltransferase (GAMT)-knockout mice - a one year longitudinal MRI study. J Cardiovasc Magn Reson, 10 (1), pp. 9. | Show Abstract | Read more

BACKGROUND: High-resolution magnetic resonance imaging (cine-MRI) is well suited for determining global cardiac function longitudinally in genetically or surgically manipulated mice, but in practice it is seldom used to its full potential. In this study, male and female guanidinoacetate N-methyltransferase (GAMT) knockout, and wild type littermate mice were subjected to a longitudinal cine-MRI study at four time points over the course of one year. GAMT is an essential enzyme in creatine biosynthesis, such that GAMT deficient mice are entirely creatine-free. Since creatine plays an important role in the buffering and transfer of high-energy phosphate bonds in the heart, it was hypothesized that lack of creatine would be detrimental for resting cardiac performance during ageing. METHODS: Measurements of cardiac structure (left ventricular mass and volumes) and function (ejection fraction, stroke volume, cardiac output) were obtained using high-resolution cine-MRI at 9.4 T under isoflurane anaesthesia. RESULTS: There were no physiologically significant differences in cardiac function between wild type and GAMT knockout mice at any time point for male or female groups, or for both combined (for example ejection fraction: 6 weeks (KO vs. WT): 70 +/- 6% vs. 65 +/- 7%; 4 months: 70 +/- 6% vs. 62 +/- 8%; 8 months: 62 +/- 11% vs. 62 +/- 6%; 12 months: 61 +/- 7% vs. 59 +/- 11%, respectively). CONCLUSION: These findings suggest the presence of comprehensive adaptations in the knockout mice that can compensate for a lack of creatine. Furthermore, this study clearly demonstrates the power of cine-MRI for accurate non-invasive, serial cardiac measurements. Cardiac growth curves could easily be defined for each group, in the same set of animals for all time points, providing improved statistical power, and substantially reducing the number of mice required to conduct such a study. This technique should be eminently useful for following changes of cardiac structure and function during ageing.

Specchia C, Barlera S, Chiodini BD, Nicolis EB, Farrall M, Peden J, Collins R, Watkins H, Tognoni G, Franzosi MG, PROCARDIS Consortium. 2008. Quantitative trait genetic linkage analysis of body mass index in familial coronary artery disease. Hum Hered, 66 (1), pp. 19-24. | Show Abstract | Read more

OBJECTIVE: Body mass index (BMI) is one of the most reproducible and commonly used proxies for obesity and is known to be influenced by many environmental causes as well as genetic factors. Identification of susceptibility genes for BMI regulation has been difficult. Reasons for these inconclusive results are both methodological and related to obesity aetiology. A genome-wide linkage analysis was performed to localise Quantitative trait loci influencing BMI in a large cohort collected in the PROCARDIS coronary heart disease study consisting of 1,812 informative families. METHODS: Multipoint linkage analysis for BMI was conducted using both a variance component approach and a model-free regression method, and the resulting LOD scores were compared. RESULTS: The strongest evidence for linkage was detected on chromosomes 13 (LOD 1.6). Other regions showing a LOD score greater than 1 were observed on chromosomes 3, 5, 11, 12 and 15. These results were mainly confirmed by the three different approaches used in the analysis. CONCLUSION: Our study did not find any locus with strongly supporting evidence for linkage to BMI even in such a large sample. Our results confirm the substantial genetic heterogeneity influencing BMI regulation that has emerged from the majority of genome scans so far published.

Robinson P, Griffiths PJ, Watkins H, Redwood CS. 2007. Dilated and hypertrophic cardiomyopathy mutations in troponin and alpha-tropomyosin have opposing effects on the calcium affinity of cardiac thin filaments. Circ Res, 101 (12), pp. 1266-1273. | Show Abstract | Read more

Dilated cardiomyopathy and hypertrophic cardiomyopathy (HCM) can be caused by mutations in thin filament regulatory proteins of the contractile apparatus. In vitro functional assays show that, in general, the presence of dilated cardiomyopathy mutations decreases the Ca(2+) sensitivity of contractility, whereas HCM mutations increase it. To assess whether this functional phenomenon was a direct result of altered Ca(2+) affinity or was caused by altered troponin-tropomyosin switching, we assessed Ca(2+) binding of the regulatory site of cardiac troponin C in wild-type or mutant troponin complex and thin filaments using a fluorescent probe (2-[4'-{iodoacetamido}aniline]-naphthalene-6-sulfonate) attached to Cys35 of cardiac troponin C. The Ca(2+)-binding affinity (pCa(50)=6.57+/-0.03) of reconstituted troponin complex was unaffected by all of the HCM and dilated cardiomyopathy troponin mutants tested, with the exception of the troponin I Arg145Gly HCM mutation, which caused an increase (DeltapCa(50)=+0.31+/-0.05). However, when incorporated into regulated thin filaments, all but 1 of the 10 troponin and alpha-tropomyosin mutants altered Ca(2+)-binding affinity. Both HCM mutations increased Ca(2+) affinity (DeltapCa(50)=+0.41+/-0.02 and +0.51+/-0.01), whereas the dilated cardiomyopathy mutations decreased affinity (DeltapCa(50)=-0.12+/-0.04 to -0.54+/-0.04), which correlates with our previous functional in vitro assays. The exception was the troponin T Asp270Asn mutant, which caused a significant decrease in cooperativity. Because troponin is the major Ca(2+) buffer in the cardiomyocyte sarcoplasm, we suggest that Ca(2+) affinity changes caused by cardiomyopathy mutant proteins may directly affect the Ca(2+) transient and hence Ca(2+)-sensitive disease state remodeling pathways in vivo. This represents a novel mechanism for this class of mutation.

Baker M, Rahman T, Hall D, Avery PJ, Mayosi BM, Connell JM, Farrall M, Watkins H, Keavney B. 2007. The C-532T polymorphism of the angiotensinogen gene is associated with pulse pressure: a possible explanation for heterogeneity in genetic association studies of AGT and hypertension. Int J Epidemiol, 36 (6), pp. 1356-1362. | Show Abstract | Read more

BACKGROUND: Many previous studies have investigated whether there is an association between genotypes at the angiotensinogen (AGT) gene and hypertensive status, but few have incorporated quantitative data. Although meta-analyses support a possible effect of AGT variants on blood pressure (BP), substantial unexplained between-study heterogeneity has been observed. We hypothesized that a primary effect of AGT variants on arterial stiffness (and thus pulse pressure) might explain such heterogeneity, and tested for such an effect in a family study. METHODS: We studied 1425 individuals from 248 families ascertained through a proband with essential hypertension. BP was measured using 24 h ambulatory monitoring, and polymorphisms of the AGT gene that had been previously associated with hypertension and/or plasma angiotensinogen levels were typed. Pulse pressure was used as a measurement of arterial stiffness. RESULTS: We observed a highly significant association between genotypes at the AGT C-532T polymorphism and pulse pressure (p = 0.00006). Each T allele was associated with a 5% lower pulse pressure (that is, an additive effect). This resulted from opposing genotypic effects to (slightly) lower systolic BP and (slightly) elevate DBP. CONCLUSIONS: These results suggest that genetic variation at the angiotensinogen locus may primarily affect arterial stiffness, and therefore pulse pressure. The heterogeneity between previous genetic studies of AGT and hypertension status could in part be explained by this finding, since case selection criteria based on systolic BP, diastolic BP, or both would result in different levels of selection for the -532T allele.

Nethononda MR, Whitworth P, Keavney BD, Neubauer S, Watkins H, Doll HA. 2007. Predictors of death in hypertensive families followed up over 14 years EUROPEAN HEART JOURNAL, 28 pp. 264-264.

Brown M, Boon N, Brooks N, Camm J, Corris P, Caulfield M, Chilvers E, Ewan P, Gibson J, Griffin G et al. 2007. Medical training in the UK: sleepwalking to disaster. Lancet, 369 (9574), pp. 1673-1675. | Read more

Petersen SE, Jerosch-Herold M, Hudsmith LE, Robson MD, Francis JM, Doll HA, Selvanayagam JB, Neubauer S, Watkins H. 2007. Evidence for microvascular dysfunction in hypertrophic cardiomyopathy: new insights from multiparametric magnetic resonance imaging. Circulation, 115 (18), pp. 2418-2425. | Show Abstract | Read more

BACKGROUND: Microvascular dysfunction in hypertrophic cardiomyopathy (HCM) may create an ischemic substrate conducive to sudden death, but it remains unknown whether the extent of hypertrophy is associated with proportionally poorer perfusion reserve. Comparisons between magnitude of hypertrophy, impairment of perfusion reserve, and extent of fibrosis may offer new insights for future clinical risk stratification in HCM but require multiparametric imaging with high spatial and temporal resolution. METHODS AND RESULTS: Degree of hypertrophy, myocardial blood flow at rest and during hyperemia (hMBF), and myocardial fibrosis were assessed with magnetic resonance imaging in 35 HCM patients (9 [26%] male/26 female) and 14 healthy controls (4 [29%] male/10 female), aged 18 to 78 years (mean+/-SD, 42+/-14 years) with the use of the American Heart Association left ventricular 16-segment model. Resting MBF was similar in HCM patients and controls. hMBF was lower in HCM patients (1.84+/-0.89 mL/min per gram) than in healthy controls (3.42+/-1.76 mL/min per gram, with a difference of -0.95+/-0.30 [SE] mL/min per gram; P<0.001) after adjustment for multiple variables, including end-diastolic segmental wall thickness (P<0.001). In HCM patients, hMBF decreased with increasing end-diastolic wall thickness (P<0.005) and preferentially in the endocardial layer. The frequency of endocardial hMBF falling below epicardial hMBF rose with wall thickness (P=0.045), as did the incidence of fibrosis (P<0.001). CONCLUSIONS: In HCM the vasodilator response is reduced, particularly in the endocardium, and in proportion to the magnitude of hypertrophy. Microvascular dysfunction and subsequent ischemia may be important components of the risk attributable to HCM.

Mirza M, Robinson P, Kremneva E, Copeland O, Nikolaeva O, Watkins H, Levitsky D, Redwood C, El-Mezgueldi M, Marston S. 2007. The effect of mutations in alpha-tropomyosin (E40K and E54K) that cause familial dilated cardiomyopathy on the regulatory mechanism of cardiac muscle thin filaments. J Biol Chem, 282 (18), pp. 13487-13497. | Show Abstract | Read more

E40K and E54K mutations in alpha-tropomyosin cause inherited dilated cardiomyopathy. Previously we showed, using Ala-Ser alpha-tropomyosin (AS-alpha-Tm) expressed in Escherichia coli, that both mutations decrease Ca(2+) sensitivity. E40K also reduces V(max) of actin-Tm-activated S-1 ATPase by 18%. We investigated cooperative allosteric regulation by native Tm, AS-alpha-Tm, and the two dilated cardiomyopathy-causing mutants. AS-alpha-Tm has a lower cooperative unit size (6.5) than native alpha-tropomyosin (10.0). The E40K mutation reduced the size of the cooperative unit to 3.7, whereas E54K increased it to 8.0. For the equilibrium between On and Off states, the K(T) value was the same for all actin-Tm species; however, the K(T) value of actin-Tm-troponin at pCa 5 was 50% less for AS-alpha-Tm E40K than for AS-alpha-Tm and AS-alpha-Tm E54K. K(b), the "closed" to "blocked" equilibrium constant, was the same for all tropomyosin species. The E40K mutation reduced the affinity of tropomyosin for actin by 1.74-fold, but only when in the On state (in the presence of S-1). In contrast the E54K mutation reduced affinity by 3.5-fold only in the Off state. Differential scanning calorimetry measurements of AS-alpha-Tm showed that domain 3, assigned to the N terminus of tropomyosin, was strongly destabilized by both mutations. Additionally with AS-alpha-Tm E54K, we observed a unique new domain at 55 degrees C accounting for 25% of enthalpy indicating stabilization of part of the tropomyosin. The disease-causing mechanism of the E40K mutation may be accounted for by destabilization of the On state of the thin filaments; however, the E54K mutation has a more complex effect on tropomyosin structure and function.

Ashrafian H, Watkins H. 2007. Reviews of translational medicine and genomics in cardiovascular disease: new disease taxonomy and therapeutic implications cardiomyopathies: therapeutics based on molecular phenotype. J Am Coll Cardiol, 49 (12), pp. 1251-1264. | Show Abstract | Read more

The enduring subdivision of cardiomyopathies into hypertrophic (HCM), dilated (DCM), and restrictive (RCM) categories reflects the emphasis of traditional classifications on morphology. Rapid advances in the genetic interrogation of these disorders have redefined their taxonomy and revealed potential conflicts between the old and new classifications. Hypertrophic cardiomyopathy has been redefined as a disease of perturbed sarcomere function. Dilated cardiomyopathy is a disease that results from more varied perturbations, including, but not limited to, defects of the cytoskeleton. Positional cloning and candidate gene approaches have been successful in identifying >40 disease loci, many of which have led to disease genes in HCM, DCM, RCM, and arrhythmogenic right ventricular cardiomyopathy. These findings provide mechanistic insights, permit genetic screening, and to a limited extent, facilitate prognostication. Although single gene analyses rapidly focus down to the underlying mechanistic pathways, they do not take account of all relevant variation in the human genome. Correspondingly, advances in genomics, through microarrays, have facilitated characterization of these broader downstream elements. As well as refining the taxonomic reclassification of cardiomyopathies, these genomic approaches, coupled with functional studies, have identified novel potential therapeutic targets, such as cardiac energetics, calcium handling, and apoptosis. We review the successes and pitfalls of genetic and genomic approaches to cardiomyopathy and their impact on current and future clinical care.

Brown M, Boon N, Brooks N, Brown E, Camm J, Caulfield M, Chilvers E, Gibson J, Griffin G, Grossman A et al. 2007. Modernising medical careers, medical training application service, and the postgraduate medical education and training board: time for the emperors to don their clothes. Lancet, 369 (9566), pp. 967-968. | Read more

Preston LC, Lipscomb S, Robinson P, Mogensen J, McKenna WJ, Watkins H, Ashley CC, Redwood CS. 2007. Functional effects of the DCM mutant Gly159Asp troponin C in skinned muscle fibres. Pflugers Arch, 453 (6), pp. 771-776. | Show Abstract | Read more

We recently reported a dilated cardiomyopathy (DCM) causing mutation in a novel disease gene, TNNC1, which encodes cardiac troponin C (TnC). We have determined how this mutation, Gly159Asp, affects contractile regulation when incorporated into muscle fibres. Endogenous troponin in rabbit skinned psoas fibres was partially replaced by recombinant human cardiac troponin containing either wild-type or Gly159Asp TnC. We measured both the force-pCa relationship of these fibres and the activation rate using the caged-Ca(2+) compound nitrophenyl-EGTA. Gly159Asp TnC had no significant effect on either the Ca(2+) sensitivity or cooperativity of force generation when compared to wild type. However, the mutation caused a highly significant (ca. 50%) decrease in the rate of activation. This study shows that whilst not affecting the force-pCa relationship, the mutation Gly159Asp causes a significant decrease in the rate of force production and a change in the relationship between the rate of force production and generated force. In vivo, this mutation may cause both a slowing of force generation and reduction in total systolic force. This represents a novel mechanism by which a cardiomyopathy-causing mutation can affect contractility.

Robinson P, Lipscomb S, Preston LC, Altin E, Watkins H, Ashley CC, Redwood CS. 2007. Mutations in fast skeletal troponin I, troponin T, and beta-tropomyosin that cause distal arthrogryposis all increase contractile function. FASEB J, 21 (3), pp. 896-905. | Show Abstract | Read more

Distal arthrogryposes (DAs) are a group of disorders characterized by congenital contractures of distal limbs without overt neurological or muscle disease. Unexpectedly, mutations in genes encoding the fast skeletal muscle regulatory proteins troponin T (TnT), troponin I (TnI), and beta-tropomyosin (beta-TM) have been shown to cause autosomal dominant DA. We tested how these mutations affect contractile function by comparing wild-type (WT) and mutant proteins in actomyosin ATPase assays and in troponin-replaced rabbit psoas fibers. We have analyzed all four reported mutants: Arg63His TnT, Arg91Gly beta-TM, Arg174Gln TnI, and a TnI truncation mutant (Arg156ter). Thin filaments, reconstituted using actin and WT troponin and beta-TM, activated myosin subfragment-1 ATPase in a calcium-dependent, cooperative manner. Thin filaments containing either a troponin or beta-TM DA mutant produced significantly enhanced ATPase rates at all calcium concentrations without alternating calcium-sensitivity or cooperativity. In troponin-exchanged skinned fibers, each mutant caused a significant increase in Ca2+ sensitivity, and Arg156ter TnI generated significantly higher maximum force. Arg91Gly beta-TM was found to have a lower actin affinity than WT and form a less stable coiled coil. We propose the mutations cause increased contractility of developing fast-twitch skeletal muscles, thus causing muscle contractures and the development of the observed limb deformities.

Barlera S, Specchia C, Farrall M, Chiodini BD, Franzosi MG, Rust S, Green F, Nicolis EB, Peden J, Assmann G et al. 2007. Multiple QTL influence the serum Lp(a) concentration: a genome-wide linkage screen in the PROCARDIS study. Eur J Hum Genet, 15 (2), pp. 221-227. | Show Abstract | Read more

The serum concentration of lipoprotein Lp (a) is known to be highly heritable and associated with cardiovascular risk. A genome-wide variance component linkage analysis was performed to localise quantitative trait loci (QTLs) influencing Lp(a) levels in a large cohort collected in the PROCARDIS coronary heart disease study. Highly significant linkage was detected at the previously described LP(a) locus on chromosome 6q27 (LOD 108). Taking into account the effect of the locus detected on chromosome 6, a highly significant LOD score was detected on chromosome 13q22-31 (LOD 7.0). Another significant region of linkage was observed on chromosomes 11p14-15 (LOD 3.5). The significant peak at 13q22-31 shows an essential overlap with a locus modulating cholesterol in familial hypercholesterolemia. If the gene underlying these loci is the same, it will be a promising candidate target for manipulating LDL-cholesterol and Lp(a). We also detected linkage at a previously identified locus influencing Lp(a) on chromosome 1q23 (LOD 1.5). Our findings provide new and confirmatory information about genomic regions involved in the quantitative variation of Lp(a) and serve as a basis for further studies of candidate genes in these regions.

Figtree GA, Kindmark A, Lind L, Grundberg E, Speller B, Robinson BG, Channon KM, Watkins H. 2007. Novel estrogen receptor alpha promoter polymorphism increases ventricular hypertrophic response to hypertension. J Steroid Biochem Mol Biol, 103 (2), pp. 110-118. | Show Abstract | Read more

Given the strong genetic contribution to blood pressure and left ventricular hypertrophy (LVH), and the influence of estrogen on these parameters, we hypothesized that polymorphisms in the estrogen receptor alpha (ERalpha) promoter may influence LVH. Three novel polymorphisms were identified upstream of the ERalpha alternatively spliced exon 1E, within sequence which demonstrated significant promoter activity in vitro. Demonstration of ERalpha E isoform expression in human ventricle by RT-PCR supported a possible functional role for the 1E novel polymorphisms in estrogen signaling in the heart. Indeed, G>A (-721 E) was significantly associated with LVH after controlling for systolic blood pressure and sex in a healthy population (n=74), contributing to 23% of interventricular septum (IVS) width variance (p<0.001) and 9.4% of left ventricular mass index (LVMI) variance (p=0.035). In a separate hypertensive cohort, male carriers of the A allele (n=8) had a 17% increase in IVS (95% CI: 6-28%) and a 19% increase in LVMI (3-34%) compared to GG homozygotes (n=84). We conclude that a novel polymorphism in the promoter of a cardiac mRNA splice isoform of ERalpha is associated with LVH.

Flashman E, Watkins H, Redwood C. 2007. Localization of the binding site of the C-terminal domain of cardiac myosin-binding protein-C on the myosin rod. Biochem J, 401 (1), pp. 97-102. | Show Abstract | Read more

cMyBP-C [cardiac (MyBP-C) myosin-binding protein-C)] is a sarcomeric protein involved both in thick filament structure and in the regulation of contractility. It is composed of eight IgI-like and three fibronectin-3-like domains (termed C0-C10). Mutations in the gene encoding cMyBP-C are a principal cause of HCM (hypertrophic cardiomyopathy). cMyBP-C binds to the LMM (light meromyosin) portion of the myosin rod via its C-terminal domain, C10. We investigated this interaction in detail to determine whether HCM mutations in beta myosin heavy chain located within the LMM portion alter the binding of cMyBP-C, and to define the precise region of LMM that binds C10 to aid in developing models of the arrangement of MyBP-C on the thick filament. In co-sedimentation experiments recombinant C10 bound full-length LMM with a K(d) of 3.52 microM and at a stoichiometry of 1.14 C10 per LMM. C10 was also shown to bind with similar affinity to LMM containing either the HCM mutations A1379T or S1776G, suggesting that these HCM mutations do not perturb C10 binding. Using a range of N-terminally truncated LMM fragments, the cMyBP-C-binding site on LMM was shown to lie between residues 1554 and 1581. Since it had been reported previously that acidic residues on myosin mediate the C10 interaction, three clusters of acidic amino acids (Glu1554/Glu1555, Glu1571/Glu1573 and Glu1578/Asp1580/Glu1581/Glu1582) were mutated in full-length LMM and the proteins tested for C10 binding. No effect of these mutations on C10 binding was however detected. We interpret our results with respect to the localization of the proposed trimeric collar on the thick filament.

Imrie H, Freel M, Mayosi BM, Davies E, Fraser R, Ingram M, Cordell HJ, Farrall M, Avery PJ, Watkins H et al. 2006. Association between aldosterone production and variation in the 11beta-hydroxylase (CYP11B1) gene. J Clin Endocrinol Metab, 91 (12), pp. 5051-5056. | Show Abstract | Read more

CONTEXT: Variation in the region of chromosome 8 including the genes steroid 11beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) influences mineralocorticoid and glucocorticoid metabolism. However, the relative importance of polymorphisms in CYP11B1 and CYP11B2 in determining these phenotypes is unknown. OBJECTIVE: Our objective was to investigate genetic influences of the CYP11B1 and CYP11B2 genes on mineralocorticoid metabolism. DESIGN: We measured 24-h urinary excretion of the key metabolites of the principal mineralocorticoids, glucocorticoids and androgens secreted by the adrenal cortex. We genotyped polymorphisms spanning the CYP11B1 and CYP11B2 genes, which together capture all common variations at the locus. PARTICIPANTS: Participants included 573 members of 105 British Caucasian families ascertained on a hypertensive proband. MAIN OUTCOME MEASURES: We assessed heritability of urinary tetrahydroaldosterone (THAldo) excretion and association of THAldo excretion with genotype. RESULTS: The heritability of THAldo excretion was 52% (P < 10(-6)). There was significant association between THAldo and genotype at several of the CYP11B1/B2 polymorphisms. The strongest association was observed at the rs6387 (2803A/G) polymorphism in intron 3 of CYP11B1 (P = 0.0004). Association followed a codominant model with a 21% higher THAldo excretion per G allele. Genotype at rs6387 accounted for 2.1% of the total population variability of THAldo. We found significant association between THAldo excretion and urinary total androgen excretion, urinary tetrahydrodeoxycortisol level, and urinary cortisol metabolites (all P < 0.001). CONCLUSIONS: Aldosterone synthesis is highly heritable and is affected by genotype at CYP11B1. Our findings support the hypothesis that genetically determined differences in 11-hydroxylation efficiency can have downstream effects on mineralocorticoid synthesis. Such effects may be of relevance to the development of low-renin essential hypertension.

Petersen SE, Hudsmith LE, Robson MD, Doll HA, Francis JM, Wiesmann F, Jung BA, Hennig J, Watkins H, Neubauer S. 2006. Sex-specific characteristics of cardiac function, geometry, and mass in young adult elite athletes. J Magn Reson Imaging, 24 (2), pp. 297-303. | Show Abstract | Read more

PURPOSE: To study young adult elite athletes with age- and sex-matched sedentary controls to assess sex-specific differences for left ventricular (LV) and right ventricular (RV) volumes and mass as well as for LV contraction and relaxation. MATERIALS AND METHODS: A total of 23 male athletes (mean age 25 +/- 4 years, training 22 +/- 7 hours/week in rowing, swimming, or triathlon) and 20 female athletes (mean age 24 +/- 4 years, training 19 +/- 5 hours/week in rowing, swimming, or triathlon) and age- and sex-matched sedentary controls (21 male/17 female) underwent cardiovascular magnetic resonance (CMR) imaging (1.5 Tesla). Cardiac phase contrast imaging using a black-blood k-space segmented gradient echo sequence was used for analysis of cardiac contraction and relaxation and steady-state free-precession cine images were acquired for determination of cardiac volumes and mass. RESULTS: Male and female athletes showed similar increases in LV and RV volume and mass indices when compared to controls (ranging between 15% and 42%). No sex-specific differences in training effect on LV and RV volumes, mass indices, and ejection fractions, as well as LV to RV ratios of these volume and mass indices (parameters of balanced LV and RV dilatation and hypertrophy) were observed (all P for interaction >0.05). Similarly, no sex-specific differences in training effect on cardiac contraction and relaxation were found (all P for interaction >0.05). CONCLUSION: Young adult elite athletes do not show sex-specific adaptive structural and functional changes to exercise training in accordance with the benign nature of the hypertrophy associated with athlete's heart.

Hudsmith LE, Petersen SE, Francis JM, Robson MD, Watkins H, Neubauer S. 2006. Hypertrophic cardiomyopathy in Noonan Syndrome closely mimics familial hypertrophic cardiomyopathy due to sarcomeric mutations. Int J Cardiovasc Imaging, 22 (3-4), pp. 493-495. |