The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal Mendelian Long QT Syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals we identified 35 common variant QT interval loci, that collectively explain ∼8-10% of QT variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 novel QT loci in 298 unrelated LQTS probands identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode for proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies novel candidate genes for ventricular arrhythmias, LQTS,and SCD.
genome-wide association study; QT interval; Long QT Syndrome; sudden cardiac death; myocardial repolarization; arrhythmias
DNA methylation is one of several epigenetic mechanisms that contribute to the regulation of gene expression; however, the extent to which methylation of CpG dinucleotides correlates with gene expression at the genome-wide level is still largely unknown. Using purified primary monocytes from subjects in a large community-based cohort (n = 1264), we characterized methylation (>485 000 CpG sites) and mRNA expression (>48K transcripts) and carried out genome-wide association analyses of 8370 expression phenotypes. We identified 11 203 potential cis-acting CpG loci whose degree of methylation was associated with gene expression (eMS) at a false discovery rate threshold of 0.001. Most of the associations were consistent in effect size and direction of effect across sex and three ethnicities. Contrary to expectation, these eMS were not predominately enriched in promoter regions, or CpG islands, but rather in the 3′ UTR, gene bodies, CpG shores or ‘offshore’ sites, and both positive and negative correlations between methylation and expression were observed across all locations. eMS were enriched for regions predicted to be regulatory by ENCODE (Encyclopedia of DNA Elements) data in multiple cell types, particularly enhancers. One of the strongest association signals detected (P < 2.2 × 10−308) was a methylation probe (cg17005068) in the promoter/enhancer region of the glutathione S-transferase theta 1 gene (GSTT1, encoding the detoxification enzyme) with GSTT1 mRNA expression. Our study provides a detailed description of the epigenetic architecture in human monocytes and its relationship to gene expression. These data may help prioritize interrogation of biologically relevant methylation loci and provide new insights into the epigenetic basis of human health and diseases.
Statins effectively lower LDL cholesterol levels in large studies and the observed interindividual response variability may be partially explained by genetic variation. Here we perform a pharmacogenetic meta-analysis of genome-wide association studies (GWAS) in studies addressing the LDL cholesterol response to statins, including up to 18,596 statin-treated subjects. We validate the most promising signals in a further 22,318 statin recipients and identify two loci, SORT1/CELSR2/PSRC1 and SLCO1B1, not previously identified in GWAS. Moreover, we confirm the previously described associations with APOE and LPA. Our findings advance the understanding of the pharmacogenetic architecture of statin response.
Statins are effectively used to prevent and manage cardiovascular disease, but patient response to these drugs is highly variable. Here, the authors identify two new genes associated with the response of LDL cholesterol to statins and advance our understanding of the genetic basis of drug response.
Vitamin D deficiency has been associated with hypertension, diabetes mellitus, and incident stroke. Little is known about the association between vitamin D and subclinical cerebrovascular disease.
To examine the relationship of 25-hydroxyvitamin D (25[OH]D) levels with cerebrovascular abnormalities as assessed on brain magnetic resonance imaging (MRI) among participants of the Atherosclerosis Risk in Communities (ARIC) Brain MRI study.
DESIGN, SETTING, AND PARTICIPANTS
Participants were white and black adults aged 55 to 72 years with no history of clinical stroke who underwent a cerebral MRI at ARIC visit 3 (n = 1622) and a second cerebral MRI approximately 10 years later (n = 888).
The 25(OH)D level was measured by mass spectrometry at visit 3, with levels adjusted for calendar month and categorized using race-specific quartiles.
MAIN OUTCOMES AND MEASURES
The cross-sectional and prospective associations of 25(OH)D levels with white matter hyperintensities (WMHs) and MRI-defined infarcts were investigated using multivariable regression models.
The mean age of the participants was 62 years, 59.6% were women, and 48.6% were black. Lower 25(OH)D levels were not significantly associated with WMH score of severity, prevalent high-grade WMH score (≥3), or prevalent infarcts in cross-sectional, multivariable-adjusted models (all P > .05). Similarly, no significant prospective associations were found for lower 25(OH)D levels with change in WMH volume, incident high WMH score (≥3), or incident infarcts on the follow-up MRI, which occurred approximately 10 years later.
CONCLUSIONS AND RELEVANCE
A single measure of 25(OH)D was not cross-sectionally associated with WMH grade or prevalent subclinical infarcts and was not prospectively associated with WMH progression or subclinical brain infarcts seen on serial cerebral MRIs obtained approximately 10 years apart. These findings do not support optimizing vitamin D levels for brain health.
Human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) may increase the risk of fatty liver disease. We determined the prevalence of and risk factors for fatty liver by comparing HIV-infected men with HIV-uninfected men who have sex with men in the Multicenter AIDS Cohort Study (MACS).
In 719 MACS participants who consumed less than three alcoholic drinks daily, fatty liver was defined as a liver-to-spleen attenuation ratio < 1 on noncontrast computed tomography (CT). We genotyped single nucleotide polymorphisms in the patatin-like phospholipase domain-containing 3 (PNPLA3) gene and in other genes previously associated with nonalcoholic fatty liver disease. Risk factors for fatty liver were determined using multivariable logistic regression.
Among 254 HIV-uninfected men and 465 HIV-infected men, 56 % were White with median age 53 years and median body mass index 25.8 kg/m 2. The vast majority of HIV-infected men (92 %) were on ART, and 87 % of the HIV-infected men were treated with a nucleoside reverse transcriptase inhibitor for a median duration of 8.5 years. Overall, 15 % of the cohort had fatty liver, which was more common in the HIV-uninfected compared with the HIV-infected men (19 vs. 13 %, P= 0.02). In multivariable analysis, HIV infection was associated with a lower prevalence of fatty liver (odds ratio (OR) = 0.44, P= 0.002), whereas a higher prevalence of fatty liver was seen in participants with PNPLA3 (rs738409) non-CC genotype (OR = 2.06, P= 0.005), more abdominal visceral adipose tissue (OR = 1.08 per 10 cm2, P< 0.001), and homeostatic model assessment of insulin resistance (HOMA-IR) ≥ 4.9 (OR = 2.50, P= 0.001). Among HIV-infected men, PNPLA3 (rs738409) non-CC genotype was associated with a higher prevalence of fatty liver (OR = 3.30, P= 0.001) and cumulative dideoxynucleoside exposure (OR = 1.44 per 5 years, P= 0.02).
CT-defined fatty liver is common among men at risk for HIV infection and is associated with greater visceral adiposity, HOMA-IR, and PNPLA3 (rs738409). Although treated HIV infection was associated with a lower prevalence of fatty liver, prolonged exposure to dideoxynucleo side analogs is associated with higher prevalence.
Coronary artery disease (CAD) has been associated with HIV infection; however data are not consistent.
We performed cardiac CT to determine whether HIV-infected men have more coronary atherosclerosis than uninfected men.
Cross-sectional study within the Multicenter AIDS Cohort Study(MACS).
HIV-infected (n=618) and –uninfected (n=383) men who have sex with men (MSM) had non-contrast and contrast enhanced cardiac CT if they were between 40–70 years, weighed <300 pounds, and had no history of coronary revascularization.
Presence and extent, for those with plaque, of coronary artery calcium (CAC) on non-contrast CT, and of any plaque, non-calcified, mixed or calcified plaque and stenosis on CT angiography.
1001 men underwent non-contrast CT of whom 759 had coronary CT angiography. After adjusting for age, race, center, and cohort, HIV-infected men had a greater prevalence of CAC [Prevalence ratio(PR)=1.21, 95% confidence interval (CI) 1.08–1.35, p=0.001], and any plaque [PR=1.14(1.05–1.24),p=0.001], including non-calcified plaque [PR=1.28(1.13–1.45),p<0.001) and mixed plaque [PR=1.35(1.10–1.65),p=0.004] than HIV-uninfected men. Associations between HIV-infection and any plaque and non-calcified plaque remained significant (p<0.005) after CAD risk factor adjustment. HIV-infected men also had a greater extent of non-calcified plaque after CAD risk factor adjustment (p=0.026). HIV-infected men had a greater prevalence of coronary artery stenosis>50% than HIV-uninfected men [PR=1.48(1.06–2.07),p=0.020), but not after CAD risk factor adjustment. Longer duration of highly active antiretroviral therapy [PR=1.09(1.02–1.17), p=0.007,per year] and lower nadir CD4+ T-cell count [PR=0.80(0.69–0.94),p=0.005, per 100 cells] were associated with coronary stenosis>50%.
Coronary artery plaque, especially non-calcified plaque, is more prevalent and extensive in HIV-infected men, independent of CAD risk factors.
Cross-sectional observational study design and inclusion of only men.
Primary Funding Source
NHLBI and NIAID
We assess the improvement in discrimination afforded by the addition thoracic aorta calcium (TAC), aortic valve calcification (AVC), mitral annular calcification (MAC), pericardial adipose tissue volume (PAT) and liver attenuation (LA) to Framingham risk score(FRS) + coronary artery calcium (CAC) for incident CHD/CVD in a multi ethnic cohort.
Methods and Results
A total 5745(2710 were intermediate Framingham risk, 210 CVD and 155 CHD events) 251 had adjudicated CHD, 346 had CVD events, 321 died after 9 years of follow-up. Cox proportional hazard, receiver operator curve (ROC) and net reclassification improvement (NRI) analyses.
In the whole cohort and also when the analysis was restricted to only the intermediate risk participants: CAC, TAC, AVC and MAC were all significantly associated with incident CVD/CHD/ mortality; CAC had the strongest association. When added to the FRS, CAC had the highest area under the curve (AUC) for the prediction of incident CHD/CVD; LA had the least. The addition of TAC, AVC, MAC, PAT and LA to FRS + CAC all resulted in a significant reduction in AUC for incident CHD [0.712 vs. 0.646, 0.655, 0.652, 0.648 and 0.569; all p<0.01 respectively] in participants with intermediate FRS. The addition of CAC to FRS resulted in an NRI of 0.547 for incident CHD in the intermediate risk group. The NRI when TAC, AVC, MAC, PAT and LA were added to FRS + CAC were 0.024, 0.026, 0.019, 0.012 and 0.012 respectively, for incident CHD in the intermediate risk group. Similar results were obtained for incident CVD in the intermediate risk group and also when the whole cohort was used instead of the intermediate FRS group.
The addition of CAC to the FRS provides superior discrimination especially in intermediate risk individuals compared with the addition of TAC, AVC, MAC, PAT or LA for incident CHD/CVD. Compared with FRS + CAC, the addition of TAC, AVC, MAC, PAT or LA individually to FRS + CAC worsens the discrimination for incident CHD/CVD. These CT risk markers are unlikely to be useful for improving cardiovascular risk prediction.
cardiac CT derived risk factors; coronary heart disease; cardiovascular events; risk prediction
How 9p21 variation affects risk of cardiovascular disease is unclear, so we assessed whether 9p21 variants are associated with arterial elasticity or retinal microvascular findings.
In the prospective Multi-Ethnic Study of Atherosclerosis (MESA) we assessed 378 SNPs in the 9p21 locus. Within four ethnic groups, we used an additive genetic model to relate the 9p21 SNPs to five vascular phenotypes: small and large elasticity derived from radial diastolic pulse contour analysis; Young’s elastic modulus from carotid artery ultrasound measurements; and the diameter of the central retinal arteries and veins.
In neither ethnic-specific nor pooled data was there any statistically significant association between any of the 9p21 SNPs and any of the five vascular phenotypes.
Our study does not support an association of 9p21 variation with arterial elasticity or retinal microvascular abnormalities.
Prospective study; 9p21 SNP; retinal microvascular abnormalities; arterial elasticity
Coronary artery calcium (CAC) predicts coronary heart disease (CHD) events and serial measurement of CAC has been proposed to evaluate atherosclerosis progression. We examined whether progression of CAC is a predictor of future CHD events.
Methods and Results
We studied 6,778 persons (52.8% female) aged 45–84 years from the Multi-Ethnic Study of Atherosclerosis. 5,682 persons had baseline and follow-up CAC scans approximately 2.5 ± 0.8 years apart; multiple imputation was used to account for the remainder (n=1,096) missing follow-up scans. Median follow-up duration from the baseline was 7.6 (max=9.0) years. CAC change was assessed by absolute change between baseline and follow-up CAC. Cox proportional hazards regression providing hazard ratios (HR) examined the relation of change in CAC with CHD events, adjusting for age, gender, ethnicity, baseline calcium score, and other risk factors. 343 total and 206 hard CHD events occurred. The annual change in CAC averaged 24.9 ± 65.3 units. Among persons without CAC at baseline (n=3,396), a 5 unit annual change in CAC was associated with an adjusted HR of 1.4 (1.0–1.9) for total and 1.5 (1.1–2.1) for hard CHD. Among those with CAC>0 at baseline HR’s (per 100 unit annual change) were 1.2 (1.1–1.4) and 1.3 (1.1–1.5), respectively. Among participants with baseline CAC, those with annual progression of ≥300 units had adjusted HR’s of 3.8 (1.5–9.6) for total and 6.3 (1.9–21.5) for hard CHD compared to those without progression.
Progression of CAC is associated with an increased risk for future hard and total CHD events.
coronary calcification; atherosclerosis; imaging; coronary heart disease
To test the predictive accuracy of the Framingham Risk Score for Stroke (FRS-S) in HIV-infected (HIV+) vs HIV-uninfected (HIV−) men.
The Multicenter AIDS Cohort Study (MACS) is an ongoing prospective study of HIV+ and HIV− men who have sex with men (MSM) enrolled in 4 US cities. We ascertained all reported stroke events during a recent 15-year timeframe (July 1, 1996 to June 30, 2011) among 3,945 participants (1,776 HIV+ and 2,169 HIV−). For those with strokes, FRS-S were calculated 10 years before the stroke event and assessed according to HIV status.
A total of 114 stroke events occurred, including 57 HIV+ and 37 HIV− participants with first-ever strokes and 19 fatal strokes. The incidence of first-ever stroke was 1.7/1,000 person-years among HIV− and 3.3/1,000 person-years among HIV+ participants. Among those with strokes, HIV+ participants were younger than HIV− participants (median age 51.3 vs 61.8 years, p < 0.0001). For these men with stroke, the average 10-year risk of stroke was higher for HIV− MSM (6.6% [range 3%–26%] vs 4.9% for HIV+ MSM [range 0%–15%], p < 0.04). Traditional risk factors for stroke were similar among the Framingham cohort and the MACS HIV+ and HIV− participants.
FRS-S prediction was systematically different in HIV+ vs HIV− men with stroke events. The FRS-S underestimates the long-term risk of stroke in HIV+ men.
Coronary artery calcification (CAC) is associated with an increased risk of cardiovascular disease; little is known, however, about thoracic aortic calcification (AC). Our goal was to characterize risk factors for CAC and AC and to estimate the genetic contribution to their variation.
Methods and Results
The presence and quantity of CAC and AC were measured with electron beam computed tomography and fasting blood tests and cardiovascular risk factors were obtained in 614 asymptomatic Amish subjects. CAC prevalence was higher in men than women (55% versus 41%; P<0.0001), although there was no sex difference in AC prevalence (51% and 56% in men and women, respectively; P=0.95). Age was more strongly associated with AC presence (odds ratio [OR], 2.7 for 5 years) than CAC presence (OR, 1.9 for 5 years) (homogeneity P=0.001). Subjects with AC had a 3.3-fold higher odds of having CAC. Heritabilities of CAC and AC presence were 0.27±0.17 (P=0.04) and 0.55±0.18 (P=0.0008), respectively, whereas the heritabilities of quantity of CAC and AC were 0.30±0.10 (P=0.001) and 0.40±0.10 (P<0.0001), respectively. The genetic correlation between CAC and AC quantity was 0.34±0.19, whereas the environmental correlation between these 2 traits was 0.38±0.09.
CAC and AC have similar risk factors, except male gender is associated only with CAC and age is more strongly associated with AC. The patterns of correlations suggest that CAC and AC share some common sets of genes and environmental factors, although it is likely that separate genes and environmental factors also influence calcification at each site.
aging; aorta; atherosclerosis; coronary disease; epidemiology; genetics; imaging
Evaluating disparities in health care is an important aspect of understanding differences in disease risk. The purpose of this study is to describe methodology for estimating such disparities, with application to a large multi-ethnic cohort study.
The Multi-Ethnic Study of Atherosclerosis (MESA) includes 6814 participants aged 45–84 years free of cardiovascular disease. Prevalence ratio (PR) regression was used to model baseline lipid lowering medication (LLM) or anti-hypertensive medication use at baseline as a function of gender, race, risk factors and estimated pre-treatment biomarker values.
Hispanics and African-Americans had lower prevalence of medication use than non-Hispanic whites, even at the same risk factor profile. This became non-significant after adjustment for socio-economic status. Although gender did not influence the prevalence of LLM use (PR=1.09, 95% CI 0.95 to 1.25), there were differences in the association of diabetes and HDL with LLM use by gender. Men were significantly less likely to be on anti-hypertensive medications than women (PR=0.86, 95% CI 0.80 to 0.92, p<0.001) and this was not explained by risk factors or socioeconomic status. Lack of health insurance strongly influenced medication use, controlling for risk factors and other markers of socio-economic status.
Disparities exist in the treatment of cholesterol and hypertension. Hispanics and African Americans had less use of LLM, men had less use of anti-hypertensives. Risk factors have differential associations with medication use depending on gender. Methods described in this paper can provide improved disparity estimation in observational cohort studies.
disparities; medication; statistical methods; statins; anti-hypertensives
Coronary heart disease (CHD) incidence has declined significantly in the US, as have levels of major coronary risk factors, including LDL-cholesterol, hypertension and smoking, but whether trends in subclinical atherosclerosis mirror these trends is not known.
Methods and Findings
To describe recent secular trends in subclinical atherosclerosis as measured by serial evaluations of coronary artery calcification (CAC) prevalence in a population over 10 years, we measured CAC using computed tomography (CT) and CHD risk factors in five serial cross-sectional samples of men and women from four race/ethnic groups, aged 55–84 and without clinical cardiovascular disease, who were members of Multi-Ethnic Study of Atherosclerosis (MESA) cohort from 2000 to 2012. Sample sizes ranged from 1062 to 4837. After adjusting for age, gender, and CT scanner, the prevalence of CAC increased across exams among African Americans, whose prevalence of CAC was 52.4% in 2000–02, 50.4% in 2003–04, 60.0% is 2005–06, 57.4% in 2007–08, and 61.3% in 2010–12 (p for trend <0.001). The trend was strongest among African Americans aged 55–64 [prevalence ratio for 2010–12 vs. 2000–02, 1.59 (95% confidence interval 1.06, 2.39); p = 0.005 for trend across exams]. There were no consistent trends in any other ethnic group. Risk factors generally improved in the cohort, and adjustment for risk factors did not change trends in CAC prevalence.
There was a significant secular trend towards increased prevalence of CAC over 10 years among African Americans and no change in three other ethnic groups. Trends did not reflect concurrent general improvement in risk factors. The trend towards a higher prevalence of CAC in African Americans suggests that CHD risk in this population is not improving relative to other groups.
Specific constellations of lipoprotein particle features, reflected as differences in mean lipoprotein particle diameters, are associated with risk of insulin resistance (IR) and cardiovascular disease (CVD). The associations of lipid profiles with disease risk differ by race/ethnicity, the reason for this is not clear. We aimed to examine whether there were additional genetic differences between racial / ethnic groups on lipoprotein profile.
Methods and results
Genotypes were assessed using the Affymetrix 6.0 array in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN). Association analysis was conducted on fasting mean particle diameters using linear models, adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. Replication of associations reaching P<1.97 * 10−05 (the level at which we achieved at least 80% power to replicate SNP-phenotype associations) was conducted in the Caucasian population of the Multi-Ethnic Study of Atherosclerosis (MESA; N=2430). Variants which replicated across both Caucasian populations were subsequently tested for association in the African-American (N=1594), Chinese (N=758) and Hispanic (N=1422) populations of MESA. Variants in the APOB gene region were significantly associated with mean VLDL diameter in GOLDN, and in the Caucasian and Hispanic populations of MESA, while variation in the hepatic lipase (LIPC) gene was associated with mean HDL diameter in both Caucasians populations only.
Our findings suggest the genetic underpinnings of mean lipoprotein diameter differ by race/ethnicity. As lipoprotein diameters are modifiable, this may lead new strategies to modify lipoprotein profiles during the reduction of IR that are sensitive to race / ethnicity.
Lipoprotein size; race / ethnicity; ApoB; Hepatic Lipase; NMR
Aspirin or dual antiplatelet therapy (DAPT) with aspirin and clopidogrel is standard therapy for patients at increased risk for cardiovascular events. However, the genetic determinants of variable response to aspirin (alone and in combination with clopidogrel) are not known.
Methods and Results
We measured ex-vivo platelet aggregation before and after DAPT in individuals (n=565) from the Pharmacogenomics of Antiplatelet Intervention (PAPI) Study and conducted a genome-wide association study (GWAS) of drug response. Significant findings were extended by examining genotype and cardiovascular outcomes in two independent aspirin-treated cohorts: 227 percutaneous coronary intervention (PCI) patients, and 1,000 patients of the International VErapamil SR/trandolapril Study (INVEST) GENEtic Substudy (INVEST-GENES). GWAS revealed a strong association between single nucleotide polymorphisms on chromosome 1q23 and post-DAPT platelet aggregation. Further genotyping revealed rs12041331 in the platelet endothelial aggregation receptor-1 (PEAR1) gene to be most strongly associated with DAPT response (P=7.66×10−9). In Caucasian and African American patients undergoing PCI, A-allele carriers of rs12041331 were more likely to experience a cardiovascular event or death compared to GG homozygotes (hazard ratio = 2.62, 95%CI 0.96-7.10, P=0.059 and hazard ratio = 3.97, 95%CI 1.10-14.31, P=0.035 respectively). In aspirin-treated INVEST-GENES patients, rs12041331 A-allele carriers had significantly increased risk of myocardial infarction compared to GG homozygotes (OR=2.03, 95%CI 1.01-4.09, P=0.048).
Common genetic variation in PEAR1 may be a determinant of platelet response and cardiovascular events in patients on aspirin, alone and in combination with clopidogrel.
Clinical Trial Registration Information
clinicaltrials.gov; Identifiers: NCT00799396 and NCT00370045
pharmacogenomics; platelets; percutaneous coronary intervention; PEAR1; CYP2C19
To examine if altered levels of adipokines, adipose-derived peptides associated with myocardial infarction in the general population, may contribute to subclinical coronary atherosclerosis in HIV-infected persons.
Nested cohort study.
We studied HIV-infected(HIV+) and HIV-uninfected(HIV−) men in the Multicenter AIDS Cohort Study with noncontrast CT to measure coronary artery calcium and regional adiposity; 75% additionally underwent coronary CT angiography to measure plaque composition and stenosis. Adiponectin and leptin levels were assessed. Multiple regression models were used to assess associations between adipokine levels and HIV disease parameters, regional adiposity, and plaque adjusted for age, race, HIV serostatus and CVD risk factors (RFs).
Significant findings were limited to adiponectin. HIV+ men (n=493) had lower adiponectin levels than HIV− men (n=250) after adjusting for CVD RFs (p<0.0001), which became non-significant after adjustment for abdominal visceral and thigh subcutaneous adipose tissue. Among HIV+ men, lower adiponectin levels were associated with higher CD4+ T cell counts (p= 0.004), longer duration of antiretroviral therapy (p= 0.006) and undetectable HIV RNA levels (p = 0.04) after adjusting for age, race and CVD RFs; only CD4+ cell count remained significant after further adjustment for adipose tissue. In both groups, lower adiponectin levels were associated with increased odds of coronary stenosis > 50% (p <0.007). Lower adiponectin levels were associated with increased extent of plaque in HIV+ and of mixed plaque in HIV− men.
Adiponectin levels were lower in HIV-infected men and related to the severity of subclinical atherosclerosis, independent of traditional CVD risk factors.
Adipokines; adiponectin; leptin; heart; subclinical coronary atherosclerosis; metabolic side effects of HIV infection; coronary CT angiography; cardiac CT
Using data from four community-based cohorts of African Americans (AA), we tested the association between genome-wide markers (SNPs) and cardiac phenotypes in the Candidate-gene Association REsource (CARe) study.
Methods and Results
Among 6,765 AA, we related age, sex, height and weight-adjusted residuals for nine cardiac phenotypes (assessed by echocardiogram or MRI) to 2.5 million SNPs genotyped using Genome-Wide Affymetrix Human SNP Array 6.0 (Affy6.0) and the remainder imputed. Within cohort genome-wide association analysis was conducted followed by meta-analysis across cohorts using inverse variance weights (genome-wide significance threshold=4.0 ×10−07). Supplementary pathway analysis was performed. We attempted replication in 3 smaller cohorts of African ancestry and tested look-ups in one consortium of European ancestry (EchoGEN). Across the 9 phenotypes, variants in 4 genetic loci reached genome-wide significance: rs4552931 in UBE2V2 (p=1.43 × 10−07) for left ventricular mass (LVM); rs7213314 in WIPI1 (p=1.68 × 10−07) for LV internal diastolic diameter (LVIDD); rs1571099 in PPAPDC1A (p= 2.57 × 10−08) for interventricular septal wall thickness (IVST); and rs9530176 in KLF5 (p=4.02 × 10−07) for ejection fraction (EF). Associated variants were enriched in three signaling pathways involved in cardiac remodeling. None of the 4 loci replicated in cohorts of African ancestry were confirmed in look-ups in EchoGEN.
In the largest GWAS of cardiac structure and function to date in AA, we identified 4 genetic loci related to LVM, IVST, LVIDD and EF that reached genome-wide significance. Replication results suggest that these loci may represent unique to individuals of African ancestry. Additional large-scale studies are warranted for these complex phenotypes.
echocardiography; ethnic; genome-wide association studies; Left atrium genetics; left ventricular mass genetics
QT is a risk factor for sudden cardiac death (SCD). A genome wide association study identified NOS1AP variants associated with QT, which have been replicated in predominantly Caucasian (CAU) populations. We used MESA to examine association of QT with NOS1AP variants in an ethnically diverse cohort.
Twenty-eight tagging SNPs spanning NOS1AP were genotyped in 2847 MESA participants (approximately equal numbers of CAU, African-Americans (AFA), Hispanics (HIS) and Chinese (CHN)), age 45–84 years, without cardiovascular disease. QT was measured using 12-lead ECG. Associations between QT and NOS1AP variants were evaluated using linear regression, adjusted for heart rate, age, gender, and field center stratified by ancestry, using an additive inheritance model. Ancestry informative markers (AIMs) and principal components using AIMs were used as additional covariates.
More NOS1AP SNPs were associated with QT in CAU than the other races. In CAU, each copy of rs1932933 risk allele was associated with an increase in QT (4.9msec, p= 7.20×10-7). Significant associations in CAU and HIS were located at the 5′ end, while associations in CHN were located at the 3′ end.
NOS1AP variants were associated with QT in CAU, with weaker evidence for selected variants in HIS and CHN. Location of significant SNPs varied across ancestry. We identified possible novel associations at the 3′ end of NOS1AP, where we observed significant association with QT in CHN only. Genotyping within these regions may determine functional variants affecting QT and SCD risk. Further investigations are needed across ethnically diverse population cohorts.
Genetics; Electrocardiography; Arrhythmia; Electrophysiology
Ethnic differences in cardiac arrhythmia incidence have been reported, with a particularly high incidence of sudden cardiac death (SCD) and low incidence of atrial fibrillation in individuals of African ancestry. We tested the hypotheses that African ancestry and common genetic variants are associated with prolonged duration of cardiac repolarization, a central pathophysiological determinant of arrhythmia, as measured by the electrocardiographic QT interval.
Methods and Results
First, individual estimates of African and European ancestry were inferred from genome-wide single nucleotide polymorphism (SNP) data in seven population-based cohorts of African Americans (n=12 097) and regressed on measured QT interval from electrocardiograms. Second, imputation was performed for 2.8 million SNPs and a genome-wide association (GWA) study of QT interval performed in ten cohorts (n=13 105). There was no evidence of association between genetic ancestry and QT interval (p=0.94). Genome-wide significant associations (p<2.5×10−8) were identified with SNPs at two loci, upstream of the genes NOS1AP (rs12143842, p=2×10−15) and ATP1B1 (rs1320976, p=2×10−10). The most significant SNP in NOS1AP was the same as the strongest SNP previously associated with QT interval in individuals of European ancestry. Low p-values (p<10−5) were observed for SNPs at several other loci previously identified in GWA studies in individuals of European ancestry, including KCNQ1, KCNH2, LITAF and PLN.
We observed no difference in duration of cardiac repolarization with global genetic indices of African ancestry. In addition, our GWA study extends the association of polymorphisms at several loci associated with repolarization in individuals of European ancestry to include African Americans.
electrocardiography; electrophysiology; genome-wide association studies; ion channels; repolarization
To determine whether long-term exposure to moderate elevations in plasma plant sterol levels increases risk for atherosclerosis.
Methods and Results
In Old Order Amish participants aged 18 to 85 years, with (n=110) and without (n=181) 1 copy of the ABCG8 G574R variant, we compared mean plasma levels of plant sterols and cholesterol precursors and carotid intima-media wall thickness. Carriers of a single 574R allele had increased plant sterol levels (eg, 35%–37% higher plasma levels of sitosterol, campesterol, and stigmasterol) and increased plant sterol/cholesterol ratios (P<0.001 for all). 574R carriers had significantly decreased levels of lathosterol and lanosterol, precursors in a pathway for endogenous cholesterol synthesis, suggesting that plant sterols may alter regulation of genes involved in cholesterol synthesis. The G574R variant was not associated with high-density lipoprotein cholesterol or low-density lipoprotein cholesterol levels. Compared with noncarriers, 574R carriers had decreased carotid intima-media wall thickness (0.62 versus 0.66 mm; age- and sex-adjusted P=0.03). Adjustment for body weight, blood pressure, and standard lipid measures (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides) did not alter this association.
Although the G574R variant is associated with moderately elevated plant sterol levels, carriers of the 574R allele had modestly lower levels of carotid wall thickness compared with noncarriers.
ABC transporter; atherosclerosis; lipids; plant sterols; sitosterol
In cross-sectional studies, patients with rheumatoid arthritis (RA) have higher coronary artery calcium (CAC) than controls. However, their rate of progression of CAC and the predictors of CAC progression have heretofore remained unknown.
Incidence and progression of CAC were compared in 155 patients with RA and 835 control participants. The association of demographic characteristics, traditional cardiovascular risk factors, RA disease characteristics and selected inflammatory markers with incidence and progression of CAC were evaluated.
The incidence rate of newly detected CAC was 8.2/100 person-years in RA and 7.3/100 person-years in non-RA control subjects [IRR 1.1 (0.7-1.8)]. RA patients who developed newly detectable CAC were older (59±7 vs. 55±6 years old, p=0.03), had higher triglyceride levels (137±86 vs. 97±60 mg/dL, p=0.03), and higher systolic blood pressure (129±17 vs. 117±15 mm Hg, p=0.01) compared to those who did not develop incident CAC. Differences in blood pressure and triglyceride levels remained significant after adjustment for age (p<=0.05). RA patients with any CAC at baseline had a median rate of yearly progression of 21 (7–62) compared to 21 (5–70) Agatston units in controls. No statistical differences between RA progressors and RA non-progressors were observed for inflammatory markers or for RA disease characteristics.
The incidence and progression of CAC did not differ between RA and non-RA participants. In patients with RA, incident CAC was associated with older age, higher triglyceride levels, and higher blood pressure, but not with inflammatory markers or RA disease characteristics.
Limited information is available regarding genetic contributions to valvular calcification, which is an important precursor of clinical valve disease.
We determined genomewide associations with the presence of aorticvalve calcification (among 6942 participants) and mitral annular calcification (among 3795 participants), as detected by computed tomographic (CT) scanning; the study population for this analysis included persons of white European ancestry from three cohorts participating in the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium (discovery population). Findings were replicated in independent cohorts of persons with either CT-detected valvular calcification or clinical aortic stenosis.
One SNP in the lipoprotein(a) (LPA) locus (rs10455872) reached genomewide significance for the presence of aorticvalve calcification (odds ratio per allele, 2.05; P = 9.0×10−10), a finding that was replicated in additional white European, African-American, and Hispanic-American cohorts (P<0.05 for all comparisons). Genetically determined Lp(a) levels, as predicted by LPA genotype, were also associated with aorticvalve calcification, supporting a causal role for Lp(a). In prospective analyses, LPA genotype was associated with incident aortic stenosis (hazard ratio per allele, 1.68; 95% confidence interval [CI], 1.32 to 2.15) and aortic-valve replacement (hazard ratio, 1.54; 95% CI, 1.05 to 2.27) in a large Swedish cohort; the association with incident aortic stenosis was also replicated in an independent Danish cohort. Two SNPs (rs17659543 and rs13415097) near the proinflammatory gene IL1F9 achieved genomewide significance for mitral annular calcification (P = 1.5×10−8 and P = 1.8×10−8, respectively), but the findings were not replicated consistently.
Genetic variation in the LPA locus, mediated by Lp(a) levels, is associated with aorticvalve calcification across multiple ethnic groups and with incident clinical aortic stenosis. (Funded by the National Heart, Lung, and Blood Institute and others.)
We assessed associations of herpes simplex virus types 1 and 2 (HSV-1 and -2), cytomegalovirus (CMV), and human herpesvirus 8 (HHV-8) infection with subclinical coronary atherosclerosis in 291 HIV-infected men in the Multicenter AIDS Cohort Study. Coronary artery calcium (CAC) was measured by non-contrast coronary CT imaging. Markers for herpesviruses infection were measured in frozen specimens collected 10-12 years prior to case identification. Multivariable logistic regression models and ordinal logistic regression models were performed. HSV-2 seropositivity was associated with coronary atherosclerosis (adjusted odds ratio [AOR] =4.12, 95% confidence interval [CI] =1.58-10.85) after adjustment for age, race/ethnicity, cardiovascular risk factors, and HIV infection related factors. Infection with a greater number of herpesviruses was associated with elevated CAC levels (AOR=1.58, 95% CI=1.06-2.36). Our findings suggest HSV-2 may be a risk factor for subclinical coronary atherosclerosis in HIV-infected men. Infection with multiple herpesviruses may contribute to the increased burden of atherosclerosis.
herpesvirus; HSV-2; atherosclerosis; HIV-1/AIDS; risk factors
Coronary heart disease (CHD) is the major cause of death in the United States. Coronary artery calcification (CAC) scores are independent predictors of CHD. African Americans (AA) have higher rates of CHD but are less well-studied in genomic studies. We assembled the largest AA data resource currently available with measured CAC to identify associated genetic variants.
We analyzed log transformed CAC quantity (ln(CAC + 1)), for association with ~2.5 million single nucleotide polymorphisms (SNPs) and performed an inverse-variance weighted meta-analysis on results for 5,823 AA from 8 studies. Heritability was calculated using family studies. The most significant SNPs among AAs were evaluated in European Ancestry (EA) CAC data; conversely, the significance of published SNPs for CAC/CHD in EA was queried within our AA meta-analysis.
Heritability of CAC was lower in AA (~30%) than previously reported for EA (~50%). No SNP reached genome wide significance (p < 5E-08). Of 67 SNPs with p < 1E-05 in AA there was no evidence of association in EA CAC data. Four SNPs in regions previously implicated in CAC/CHD (at 9p21 and PHACTR1) in EA reached nominal significance for CAC in AA, with concordant direction. Among AA, rs16905644 (p = 4.08E-05) had the strongest association in the 9p21 region.
While we observed substantial heritability for CAC in AA, we failed to identify loci for CAC at genome-wide significant levels despite having adequate power to detect alleles with moderate to large effects. Although suggestive signals in AA were apparent at 9p21 and additional CAC and CAD EA loci, overall the data suggest that even larger samples and an ethnic specific focus will be required for GWAS discoveries for CAC in AA populations.
Atherosclerosis; Coronary artery calcium; Genetics; Meta-analysis; African-American
The methodology for use of cardiac CT angiography (CTA) in low risk populations is not well defined. In order to present a reference for future studies, we present CTA methodology that is being used in an epidemiology study- the Multicenter AIDS Cohort Study (MACS).
The Multicenter AIDS Cohort Study (MACS) is an on-going multicenter prospective, observational cohort study. The MACS Cardiovascular Disease substudy plans to enroll 800 men (n= 575 HIV seropositive and n= 225 HIV seronegative) age 40-75 years for coronary atherosclerosis imaging using cardiac CTA. The protocol includes heart rate (HR) optimization with beta blockers; use of proper field of view; scan length limitation; prospective ECG-gating using the lowest beam voltage possible. All scans are evaluated for presence, extent, and composition of coronary atherosclerosis, left atrial volumes, left ventricular volume and mass and non-coronary cardiac pathology.
The first 498 participants had an average radiation dose of 2.5±1.6 milliSieverts (mSv) for the cardiac CTA study. Overall quality of scans was fair to excellent in 98.6% of studies. There were three significant adverse events- two allergic reactions to contrast and one subcutaneous contrast extravasation.
Cardiac CTA was safe and afforded a low effective radiation exposure to these asymptomatic research participants and provides valuable cardiovascular endpoints for scientific analysis. The cardiac CTA methodology described here may serve as a reference for use in future epidemiology studies aiming to assess coronary atherosclerosis and cardiac anatomy in low risk populations while minimizing radiation exposure.
CT angiography; radiation dose; epidemiological study