Chao-Yu Guo

Contribution of Clinical Correlates and 13 C-Reactive Protein Gene Polymorphisms to Interindividual Variability in Serum C-Reactive Protein Level

Background— Serum C-reactive protein (CRP) level is a heritable complex trait that predicts incident cardiovascular disease. We investigated the clinical and genetic sources of interindividual variability in serum CRP. Methods and Results— We studied serum CRP in 3301 Framingham Heart Study (FHS) participants (mean age 61 years, 53% women). Twelve clinical covariates explained 26% of the variability in CRP level, with body mass index alone explaining 15% (P<0.0001) of the variance. To investigate the influence of genetic variation at the CRP gene on CRP levels, we first constructed a dense linkage disequilibrium map for common single-nucleotide polymorphisms (SNPs) spanning the CRP locus (1 SNP every 850 bases, 26 kilobase [kb] genomic region). Thirteen CRP SNPs were genotyped in 1640 unrelated FHS participants with measured CRP levels. After adjustment for clinical covariates, 9 of 13 SNPs were associated with CRP level (P<0.05). To account for correlation among SNPs, we conducted forward stepwise selection among all 13 SNPs; a triallelic SNP (rs3091244) remained associated with CRP level (stepwise P<0.0001). The triallelic SNP (C→T→A; allele frequencies 62%, 31%, and 7%), located in the promoter sequence, explained 1.4% of total serum CRP variation; haplotypes harboring the minor T and A alleles of this SNP were associated with higher CRP level (haplotype P=0.0002 and 0.004). Conclusions— In our community-based sample, clinical variables explained 26% of the interindividual variation in CRP, whereas a common triallelic CRP SNP contributed modestly. Studies of larger samples are warranted to assess the association of genetic variation in CRP and risk of cardiovascular disease.

Cross-Sectional Correlates of Increased Aortic Stiffness in the Community The Framingham Heart Study

Background— Increased aortic stiffness is associated with numerous common diseases of aging, including heart disease, stroke, and renal disease. However, the prevalence and correlates of abnormally high aortic stiffness are incompletely understood. Methods and Results— We evaluated 2 aortic stiffness measures, carotid-femoral pulse wave velocity and forward pressure wave amplitude, in a pooled sample of the Framingham Original, Offspring, and minority Omni cohorts (mean age, 62 years; 56% women). Abnormal stiffness of each measure was defined as a value exceeding the sex-specific 90th percentile of a reference group with a low burden of conventional cardiovascular disease risk factors. Applying this criterion to the entire sample identified a 24% to 33% prevalence of abnormal stiffness measures. The prevalence of abnormal stiffness increased markedly with age, eg, for pulse wave velocity, from a few percent in both sexes aged <50 years to 64% (men) to 74% (women) in those aged ≥70 years. With adjustment for age, important correlates of abnormal aortic stiffness included higher mean arterial pressure, greater body mass index, impaired glucose metabolism, and abnormal lipids. Correlates of aortic stiffness were similar if we used age-specific rather than fixed criteria for defining abnormal stiffness. Conclusions— The prevalence of abnormal aortic stiffness increases steeply with advancing age in the community, especially in the presence of obesity or diabetes. Our data suggest that the burden of disease attributable to aortic stiffness is likely to increase considerably over the next few years as the population ages.

The Framingham Heart Study 100K SNP Genome-Wide Association Study Resource: Overview of 17 Phenotype Working Group Reports

BackgroundThe Framingham Heart Study (FHS), founded in 1948 to examine the epidemiology of cardiovascular disease, is among the most comprehensively characterized multi-generational studies in the world. Many collected phenotypes have substantial genetic contributors; yet most genetic determinants remain to be identified. Using single nucleotide polymorphisms (SNPs) from a 100K genome-wide scan, we examine the associations of common polymorphisms with phenotypic variation in this community-based cohort and provide a full-disclosure, web-based resource of results for future replication studies.MethodsAdult participants (n = 1345) of the largest 310 pedigrees in the FHS, many biologically related, were genotyped with the 100K Affymetrix GeneChip. These genotypes were used to assess their contribution to 987 phenotypes collected in FHS over 56 years of follow up, including: cardiovascular risk factors and biomarkers; subclinical and clinical cardiovascular disease; cancer and longevity traits; and traits in pulmonary, sleep, neurology, renal, and bone domains. We conducted genome-wide variance components linkage and population-based and family-based association tests.ResultsThe participants were white of European descent and from the FHS Original and Offspring Cohorts (examination 1 Offspring mean age 32 ± 9 years, 54% women). This overview summarizes the methods, selected findings and limitations of the results presented in the accompanying series of 17 manuscripts. The presented association results are based on 70,897 autosomal SNPs meeting the following criteria: minor allele frequency ≥ 10%, genotype call rate ≥ 80%, Hardy-Weinberg equilibrium p-value ≥ 0.001, and satisfying Mendelian consistency. Linkage analyses are based on 11,200 SNPs and short-tandem repeats. Results of phenotype-genotype linkages and associations for all autosomal SNPs are posted on the NCBI dbGaP website at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007.ConclusionWe have created a full-disclosure resource of results, posted on the dbGaP website, from a genome-wide association study in the FHS. Because we used three analytical approaches to examine the association and linkage of 987 phenotypes with thousands of SNPs, our results must be considered hypothesis-generating and need to be replicated. Results from the FHS 100K project with NCBI web posting provides a resource for investigators to identify high priority findings for replication.

Genetic correlates of longevity and selected age-related phenotypes: a genome-wide association study in the Framingham Study

BackgroundFamily studies and heritability estimates provide evidence for a genetic contribution to variation in the human life span.MethodsWe conducted a genome wide association study (Affymetrix 100K SNP GeneChip) for longevity-related traits in a community-based sample. We report on 5 longevity and aging traits in up to 1345 Framingham Study participants from 330 families. Multivariable-adjusted residuals were computed using appropriate models (Cox proportional hazards, logistic, or linear regression) and the residuals from these models were used to test for association with qualifying SNPs (70, 987 autosomal SNPs with genotypic call rate ≥80%, minor allele frequency ≥10%, Hardy-Weinberg test p ≥ 0.001).ResultsIn family-based association test (FBAT) models, 8 SNPs in two regions approximately 500 kb apart on chromosome 1 (physical positions 73,091,610 and 73, 527,652) were associated with age at death (p-value < 10-5). The two sets of SNPs were in high linkage disequilibrium (minimum r2 = 0.58). The top 30 SNPs for generalized estimating equation (GEE) tests of association with age at death included rs10507486 (p = 0.0001) and rs4943794 (p = 0.0002), SNPs intronic to FOXO1A, a gene implicated in lifespan extension in animal models. FBAT models identified 7 SNPs and GEE models identified 9 SNPs associated with both age at death and morbidity-free survival at age 65 including rs2374983 near PON1. In the analysis of selected candidate genes, SNP associations (FBAT or GEE p-value < 0.01) were identified for age at death in or near the following genes: FOXO1A, GAPDH, KL, LEPR, PON1, PSEN1, SOD2, and WRN. Top ranked SNP associations in the GEE model for age at natural menopause included rs6910534 (p = 0.00003) near FOXO3a and rs3751591 (p = 0.00006) in CYP19A1. Results of all longevity phenotype-genotype associations for all autosomal SNPs are web posted at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007.ConclusionLongevity and aging traits are associated with SNPs on the Affymetrix 100K GeneChip. None of the associations achieved genome-wide significance. These data generate hypotheses and serve as a resource for replication as more genes and biologic pathways are proposed as contributing to longevity and healthy aging.

Framingham Heart Study 100K Project: Genome-Wide Associations for Cardiovascular Disease Outcomes

BackgroundCardiovascular disease (CVD) and its most common manifestations – including coronary heart disease (CHD), stroke, heart failure (HF), and atrial fibrillation (AF) – are major causes of morbidity and mortality. In many industrialized countries, cardiovascular disease (CVD) claims more lives each year than any other disease. Heart disease and stroke are the first and third leading causes of death in the United States. Prior investigations have reported several single gene variants associated with CHD, stroke, HF, and AF. We report a community-based genome-wide association study of major CVD outcomes.MethodsIn 1345 Framingham Heart Study participants from the largest 310 pedigrees (54% women, mean age 33 years at entry), we analyzed associations of 70,987 qualifying SNPs (Affymetrix 100K GeneChip) to four major CVD outcomes: major atherosclerotic CVD (n = 142; myocardial infarction, stroke, CHD death), major CHD (n = 118; myocardial infarction, CHD death), AF (n = 151), and HF (n = 73). Participants free of the condition at entry were included in proportional hazards models. We analyzed model-based deviance residuals using generalized estimating equations to test associations between SNP genotypes and traits in additive genetic models restricted to autosomal SNPs with minor allele frequency ≥0.10, genotype call rate ≥0.80, and Hardy-Weinberg equilibrium p-value ≥ 0.001.ResultsSix associations yielded p < 10-5. The lowest p-values for each CVD trait were as follows: major CVD, rs499818, p = 6.6 × 10-6; major CHD, rs2549513, p = 9.7 × 10-6; AF, rs958546, p = 4.8 × 10-6; HF: rs740363, p = 8.8 × 10-6. Of note, we found associations of a 13 Kb region on chromosome 9p21 with major CVD (p 1.7 – 1.9 × 10-5) and major CHD (p 2.5 – 3.5 × 10-4) that confirm associations with CHD in two recently reported genome-wide association studies. Also, rs10501920 in CNTN5 was associated with AF (p = 9.4 × 10-6) and HF (p = 1.2 × 10-4). Complete results for these phenotypes can be found at the dbgap website http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007.ConclusionNo association attained genome-wide significance, but several intriguing findings emerged. Notably, we replicated associations of chromosome 9p21 with major CVD. Additional studies are needed to validate these results. Finding genetic variants associated with CVD may point to novel disease pathways and identify potential targeted preventive therapies.

Functional Variant of CYP4A11 20-Hydroxyeicosatetraenoic Acid Synthase Is Associated With Essential Hypertension

Background—The CYP4A11 arachidonic acid monooxygenase oxidizes endogenous arachidonic acid (AA) to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite with renovascular and tubular functions. Mice with targeted disruption of Cyp4a14, a murine homologue of CYP4A11, have severe hypertension. We combined molecular and biochemical approaches to identify a functional variant of the CYP4A11 20-HETE synthase and determine its association with hypertensive status in 2 independent human populations. Methods and Results—A thymidine-to-cytosine polymorphism at nucleotide 8590 resulted in a phenylalanine-to-serine substitution at amino acid 434. Expression of cDNA with serine 434 resulted in a protein with a significantly reduced AA and lauric acid metabolizing activity. In a population of 512 whites from Tennessee, the age, body mass index, and gender-adjusted OR of having hypertension attributable to the 8590C variant was 2.31 (95% CI 1.41 to 3.78) compared with the reference 8590TT genotype. In subjects from the Framingham Heart Study, the adjusted ORs of hypertension associated with the 8590C variant were 1.23 (CI 0.94 to 1.59; n=1538) in all subjects and 1.33 (CI 1.01 to 1.77; n=1331) when subjects with diabetes were excluded. No association of the variant with hypertension was detected in a population of 120 blacks. Conclusions—We identified a variant of the human CYP4A11 (T8590C) that encodes for a monooxygenase with reduced 20-HETE synthase activity. The association of the T8590C variant with hypertension supports its role as a polygenic determinant of blood pressure control in humans, and results obtained from the large population database suggest that the relevance of the variant may vary according to hypertension comorbidity.

Clinical and Genetic Correlates of Aldosterone-to-Renin Ratio and Relations to Blood Pressure in a Community Sample

Aldosterone:renin ratio (ARR) is used to screen for hyperaldosteronism. Data regarding correlates of ambulatory ARR in the community and its relation to hypertension incidence are limited. We defined clinical correlates of ARR, determined its heritability, tested for association and linkage, and related ARR to blood pressure (BP) progression in nonhypertensive individuals among 3326 individuals from the Framingham Heart Study (53% women; mean age: 59 years). Ambulatory morning ARR (serum aldosterone and plasma renin concentrations) were related to clinical covariates, genetic variation across the REN locus, a 10-cM linkage map, and among nonhypertensive participants (n=1773) to progression of ≥1 Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure BP category (optimal: <120/80 mm Hg, normal: 120 to 129/80 to 84 mm Hg, high normal: 130 to 139/85 to 89 mm Hg, hypertension: ≥140/90 mm Hg), or incident hypertension (systolic BP: ≥140 mm Hg, diastolic BP: ≥90 mm Hg, or use of antihypertensive treatment). ARR was positively associated with age, female sex, untreated hypertension, total/high-density lipoprotein cholesterol ratio, hormone replacement therapy, and &bgr;-blocker use, but negatively associated with angiotensin-converting enzyme inhibitor and diuretic use. ARR was heritable (h2=0.40), had modest linkage to chromosome 11p (logarithm of the odds: 1.89), but was not associated with 17 common variants in REN (n=1729). On follow-up (mean: 3 years), 607 nonhypertensive individuals (34.2%) developed BP progression, and 283 (16.0%) developed hypertension. Higher baseline logARR was associated with increased risk of BP progression (odds ratio per SD increment: 1.23; 95% CI: 1.11 to 1.37) and hypertension incidence (odds ratio per SD increment: 1.16; 95% CI: 1.00 to 1.33). ARR is a heritable trait influenced by clinical and genetic factors. There is a continuous gradient of increasing risk of BP progression across ARR levels in nonhypertensive individuals.

Genomewide Linkage Analysis to Serum Creatinine, GFR, and Creatinine Clearance in a Community-Based Population: The Framingham Heart Study

Kidney disease is a risk factor for the development of cardiovascular disease, all-cause mortality, and ESRD. It is not known to what extent genetic factors play a role in the development of kidney disease in the general population. Multipoint variance components linkage analysis was performed using Genehunter on 330 families from the Framingham Heart Study offspring cohort, using a 10-cM genomewide scan for serum creatinine, GFR, and creatinine clearance (CRCL) measured from 1998 to 2001. GFR was estimated using the simplified Modification of Diet in Renal Disease Study equation, and CRCL was estimated using the Cockcroft-Gault equation. Covariates in the adjustment included age, gender, body mass index, diabetes, systolic BP, hypertension treatment, tobacco use, and HDL cholesterol. Overall, 1224 subjects (52% women), mean age 59, were available for analysis. Mean creatinine was 0.87 mg/dl, mean GFR was 87 ml/min per 1.73 m(2), and mean creatinine clearance was 100 ml/min. The multivariable-adjusted heritability estimates for creatinine, GFR, and CRCL were 0.29, 0.33, and 0.46, respectively. The peak log of the odds ratio (LOD) scores for serum creatinine, GFR, and CRCL were 2.28 at 176 cM on chromosome 4, 2.19 at 78 cM on chromosome 4, and 1.91 at 103 cM on chromosome 3, respectively. In a community-based sample, measures of serum creatinine, GFR, and CRCL are heritable, suggesting an underlying genetic component. These results also provide suggestive evidence for linkage to measures of kidney function. Further research is necessary to identify the genes involved in the development of kidney disease and to understand their roles in this complex process.

Cross-sectional association of kidney function with valvular and annular calcification : The Framingham Heart Study

Valvular calcification is common in the setting of end-stage kidney disease and is associated with increased risks for cardiovascular disease events. It is unknown whether the prevalence of valvular calcification is increased in milder kidney disease after accounting for cardiovascular risk factors. Participants who attended the sixth examination of the Framingham Offspring Study (1995 to 1998) were eligible. Kidney function was estimated by GFR using the simplified Modification of Diet in Renal Disease Study equation. Mitral annular calcification (MAC), aortic sclerosis, and aortic annular calcification were assessed by two-dimensional echocardiography. Logistic regression was used to examine the odds of valvular calcification among participants with chronic kidney disease (CKD; GFR < 60 ml/min per 1.73 m(2)). A total of 3047 participants (52% women; mean age 59 +/- 10 yr) were available for analysis. CKD was present in 8.6% (n = 262) of the sample. Among participants with valve/annular calcification (n = 284; 9.3%), 20% had CKD, compared with 7% in patients without valvular calcification. After adjustment for age, gender, systolic and diastolic BP, hypertension treatment, total/HDL cholesterol, body mass index, diabetes, smoking status, and cardiovascular disease, participants with CKD had a 60% increased odds of MAC (odds ratio 1.6; 95% confidence interval 1.03 to 2.5). There was no significant association between CKD and either aortic sclerosis or aortic annular calcification (odds ratio 1.1 and 1.1, respectively). After age and gender adjustment, the combination of both CKD and MAC was associated with a three-fold increased risk for death compared with those with neither condition (P = 0.0004). In the community, CKD is associated with presence of MAC before the onset of ESRD. Further research is warranted to understand whether traditional and novel vascular risk factor burden, as well as metabolic derangements found in early kidney disease, can account for the CKD-MAC association.

Common Genetic Variation in KCNH2 Is Associated With QT Interval Duration The Framingham Heart Study

Background— QT prolongation is associated with increased risk of sudden cardiac death in the general population and in people exposed to QT-prolonging drugs. Mutations in the KCNH2 gene encoding the HERG potassium channel cause 30% of long-QT syndrome, and binding to this channel leads to drug-induced QT prolongation. We tested common KCNH2 variants for association with continuous QT interval duration. Methods and Results— We selected 17 single nucleotide polymorphisms and rs1805123, a previously associated missense single nucleotide polymorphism, for genotyping in 1730 unrelated men and women from the Framingham Heart Study. rs3807375 genotypes were associated with continuous QT interval duration in men and women (2-df P=0.002), with a dominant model suggested (P=0.0004). An independent sample of 871 Framingham Heart Study men and women replicated the association (1-sided dominant P=0.02). On combined analysis of 2123 subjects, individuals with AA or AG genotypes had a 0.14-SD (SE, 0.04) or 3.9-ms higher age-, sex- and RR-adjusted QT interval compared with GG individuals (P=0.00006). The previously reported association of rs1805123 (K897T) replicated under a dominant (AA/AC, 0.12 SD [SE, 0.07] or 3.1 ms higher versus CC; 1-sided P=0.04) or additive model (0.06 SD [SE, 0.03] or 1.6 ms higher per A allele; 1-sided P=0.01). Conclusions— Two common genetic variants at the KCNH2 locus are associated with continuous QT interval duration in an unselected community-based sample. Studies to determine the influence of these variants on risk of sudden cardiac death and drug-induced arrhythmias should be considered.