Genetic Epidemiology Network Of Arteriopathy Research Articles

MeQTL mapping in the GENOA study reveals genetic determinants of DNA methylation in African Americans

Identifying genetic variants that are associated with variation in DNA methylation, an analysis commonly referred to as methylation quantitative trait locus (meQTL) mapping, is an important first step towards understanding the genetic architecture underlying epigenetic variation. Most existing meQTL mapping studies have focused on individuals of European ancestry and are underrepresented in other populations, with a particular absence of large studies in populations with African ancestry. We fill this critical knowledge gap by performing a large-scale cis-meQTL mapping study in 961 African Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study. We identify a total of 4,565,687 cis-acting meQTLs in 320,965 meCpGs. We find that 45% of meCpGs harbor multiple independent meQTLs, suggesting potential polygenic genetic architecture underlying methylation variation. A large percentage of the cis-meQTLs also colocalize with cis-expression QTLs (eQTLs) in the same population. Importantly, the identified cis-meQTLs explain a substantial proportion (median = 24.6%) of methylation variation. In addition, the cis-meQTL associated CpG sites mediate a substantial proportion (median = 24.9%) of SNP effects underlying gene expression. Overall, our results represent an important step toward revealing the co-regulation of methylation and gene expression, facilitating the functional interpretation of epigenetic and gene regulation underlying common diseases in African Americans.

Epigenome-wide association study of BMI in Black populations from InterGEN and GENOA.

Obesity is a significant public health concern across the globe. Research investigating epigenetic mechanisms related to obesity and obesity-associated conditions has identified differences that may contribute to cellular dysregulation that accelerates the development of disease. However, few studies include Black women, who experience the highest incidence of obesity and early onset of cardiometabolic disorders. The association of BMI with epigenome-wide DNA methylation (DNAm) was examined using the 850K Illumina EPIC BeadChip in two Black populations (Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure [InterGEN], n=239; and The Genetic Epidemiology Network of Arteriopathy [GENOA] study, n=961) using linear mixed-effects regression models adjusted for batch effects, cell type heterogeneity, population stratification, and confounding factors. Cross-sectional analysis of the InterGEN discovery cohort identified 28 DNAm sites significantly associated with BMI, 24 of which had not been previously reported. Of these, 17 were replicated using the GENOA study. In addition, a meta-analysis, including both the InterGEN and GENOA cohorts, identified 658 DNAm sites associated with BMI with false discovery rate < 0.05. In a meta-analysis of Black women, we identified 628 DNAm sites significantly associated with BMI. Using a more stringent significance threshold of Bonferroni-corrected p value 0.05, 65 and 61 DNAm sites associated with BMI were identified from the combined sex and female-only meta-analyses, respectively. This study suggests that BMI is associated with differences in DNAm among women that can be identified with DNA extracted from salivary (discovery) and peripheral blood (replication) samples among Black populations across two cohorts.

Identification of ABCA7 SNP‐by‐CpG interactions associated with cognition in older African Americans

AbstractBackgroundThe ABCA7 gene confers the largest genetic risk for Alzheimer’s Disease (AD) in African Americans (AA) after APOE ε4. However, the relationship between ABCA7 and cognitive function has not been thoroughly examined in AA without dementia. We investigated the effect of genetic variants and epigenetic markers in ABCA7, as well as their interaction, on cognition in older AA without dementia.MethodThe sample included 629 cognitively normal AA from the Genetic Epidemiology Network of Arteriopathy (GENOA). Methylation at 72 CpG sites located within 5kb of ABCA7 were measured using the Illumina EPIC array. General cognitive function (cognition) was measured by taking the first principal component of five cognitive tests. The association between SNPs and cognition was assessed using linear mixed models controlling for age, sex, education, population structure and relatedness. The association between CpGs and cognition was assessed using the same model with further adjustment for white blood cell proportions, batch effects and smoking. We also evaluated SNP‐by‐CpG interactions.ResultNo SNPs were associated with cognition at p&lt;0.05. A 1% change in methylation at three CpGs (cg22271697, cg11714200, cg12082025) was associated with a 0.02‐0.10 standard deviation (SD) increase in cognition (p&lt;0.05; no associations significant at FDR q&lt;0.1). Four SNP‐by‐CpG interactions were associated with cognition (FDR q&lt;0.1). Contrast tests show that methylation is associated with cognition in some genotype groups (p&lt;0.05): a 1% methylation increase at cg22271697 is associated with a 0.13 SD increase in cognition for those with the AA rs3764647 genotype, a 1% increase at cg06169110 is associated with a 0.35 SD decrease in cognition for those with the rs115550680 GG or AG genotype, and a 1% increase at cg00135882 is associated with a 1.19 SD decrease in cognition for those with a rs3764650 GG genotype.ConclusionWhile AD risk SNPs in ABCA7 are not associated with cognition in the full sample of older African Americans, some do interact with proximal methylation to influence cognition. This suggests that a complicated interplay between genetic and epigenetic factors in ABCA7 may influence cognition in cognitively normal AA. A similar mechanism may play a role in cognitive aging and decline.

SNP-by-CpG Site Interactions in ABCA7 Are Associated with Cognition in Older African Americans.

SNPs in ABCA7 confer the largest genetic risk for Alzheimer's Disease (AD) in African Americans (AA) after APOE ε4. However, the relationship between ABCA7 and cognitive function has not been thoroughly examined. We investigated the effects of five known AD risk SNPs and 72 CpGs in ABCA7, as well as their interactions, on general cognitive function (cognition) in 634 older AA without dementia from Genetic Epidemiology Network of Arteriopathy (GENOA). Using linear mixed models, no SNP or CpG was associated with cognition after multiple testing correction, but five CpGs were nominally associated (p < 0.05). Four SNP-by-CpG interactions were associated with cognition (FDR q < 0.1). Contrast tests show that methylation is associated with cognition in some genotype groups (p < 0.05): a 1% increase at cg00135882 and cg22271697 is associated with a 0.68 SD decrease and 0.14 SD increase in cognition for those with the rs3764647 GG/AG (p = 0.004) and AA (p = 2 × 10-4) genotypes, respectively. In addition, a 1% increase at cg06169110 and cg17316918 is associated with a 0.37 SD decrease (p = 2 × 10-4) and 0.33 SD increase (p = 0.004), respectively, in cognition for those with the rs115550680 GG/AG genotype. While AD risk SNPs in ABCA7 were not associated with cognition in this sample, some have interactions with proximal methylation on cognition.

METRO: Multi-ancestry transcriptome-wide association studies for powerful gene-trait association detection

Integrative analysis of genome-wide association studies (GWASs) and gene expression studies in the form of a transcriptome-wide association study (TWAS) has the potential to better elucidate the molecular mechanisms underlying disease etiology. Here we present a method, METRO, that can leverage gene expression data collected from multiple genetic ancestries to enhance TWASs. METRO incorporates expression prediction models constructed in different genetic ancestries through a likelihood-based inference framework, producing calibrated p values with substantially improved TWAS power. We illustrate the benefits of METRO in both simulations and applications to seven complex traits and diseases obtained from four GWASs. These GWASs include two of primarily European ancestry (n = 188,577 and 339,226) and two of primarily African ancestry (n = 42,752 and 23,827). In the real data applications, we leverage gene expression data measured on 1,032 African Americans and 801 European Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study to identify a substantially larger number of gene-trait associations as compared to existing TWAS approaches. The benefits of METRO are most prominent in applications to GWASs of African ancestry where the sample size is much smaller than GWASs of European ancestry and where a more powerful TWAS method is crucial. Among the identified associations are high-density lipoprotein-associated genes including PLTP and PPARG that are critical for maintaining lipid homeostasis and the type II diabetes-associated gene MAPT that supports microtubule-associated protein tau as a key component underlying impaired insulin secretion.

Epigenetics of single-site and multi-site atherosclerosis in African Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA)

BackgroundDNA methylation, an epigenetic mechanism modulated by lifestyle and environmental factors, may be an important biomarker of complex diseases including cardiovascular diseases (CVD) and subclinical atherosclerosis.MethodsDNA methylation in peripheral blood samples from 391 African-Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) was assessed at baseline, and atherosclerosis was assessed 5 and 12 years later. Using linear mixed models, we examined the association between previously identified CpGs for coronary artery calcification (CAC) and carotid plaque, both individually and aggregated into methylation risk scores (MRSCAC and MRScarotid), and four measures of atherosclerosis (CAC, abdominal aorta calcification (AAC), ankle–brachial index (ABI), and multi-site atherosclerosis based on gender-specific quartiles of the single-site measures). We also examined the association between four epigenetic age acceleration measures (IEAA, EEAA, PhenoAge acceleration, and GrimAge acceleration) and the four atherosclerosis measures. Finally, we characterized the temporal stability of the epigenetic measures using repeated DNA methylation measured 5 years after baseline (N = 193).ResultsAfter adjusting for CVD risk factors, four CpGs (cg05575921(AHRR), cg09935388 (GFI1), cg21161138 (AHRR), and cg18168448 (LRRC52)) were associated with multi-site atherosclerosis (FDR < 0.1). cg05575921 was also associated with AAC and cg09935388 with ABI. MRSCAC was associated with ABI (Beta = 0.016, P = 0.006), and MRScarotid was associated with both AAC (Beta = 0.605, equivalent to approximately 1.8-fold increase in the Agatston score of AAC, P = 0.004) and multi-site atherosclerosis (Beta = 0.691, P = 0.002). A 5-year increase in GrimAge acceleration (~ 1 SD) was associated with a 1.6-fold (P = 0.012) increase in the Agatston score of AAC and 0.7 units (P = 0.0003) increase in multi-site atherosclerosis, all after adjusting for CVD risk factors. All epigenetic measures were relatively stable over 5 years, with the highest intraclass correlation coefficients observed for MRScarotid and GrimAge acceleration (0.87 and 0.89, respectively).ConclusionsWe found evidence of an association between DNA methylation and atherosclerosis at multiple vascular sites in a sample of African-Americans. Further evaluation of these potential biomarkers is warranted to deepen our understanding of the relationship between epigenetics and atherosclerosis.

Hypertensive Diseases in Pregnancy and Kidney Function Later in Life: The Genetic Epidemiology Network of Arteriopathy (GENOA) Study

ObjectiveTo evaluate the relationship between hypertensive diseases in pregnancy and kidney function later in life. MethodsWe evaluated measured glomerular filtration rate (mGFR) using iothalamate urinary clearance in 725 women of the Genetic Epidemiology Network of Arteriopathy (GENOA) study. Women were classified by self-report as nulliparous (n=62), a history of normotensive pregnancies (n=544), a history of hypertensive pregnancies (n=102), or a history of pre-eclampsia (n=17). We compared adjusted associations among these four groups with mGFR using generalized estimating equations to account for familial clustering. Chronic kidney disease (CKD) was defined as mGFR of less than 60 mL/min per 1.73 m2 or urinary albumin-creatinine ratio (UACR) greater than or equal to 30 mg/g. ResultsAmong women with kidney function measurements (mean age, 59±9 years, 52.9% African American), those with a history of hypertensive pregnancy had lower mGFR (–4.66 ml/min per 1.73 m2; 95% CI, -9.12 to -0.20) compared with women with a history of normotensive pregnancies. Compared with women with a history of normotensive pregnancies, women with a history of hypertensive pregnancy also had higher odds of mGFR less than 60 ml/min per 1.73 m2 (odds ratio, 2.09; 95% CI, 1.21 to 3.60). Additionally, women with a history of hypertensive pregnancy had greater odds for chronic kidney disease (odds ratio, 4.89; 95% CI, 1.55 to 15.44), after adjusting for age, race, education, smoking history, hypertension, body mass index, and diabetes. ConclusionA history of hypertension in pregnancy is an important prognostic risk factor for kidney disease. To our knowledge, this is the first and largest investigation showing the association between hypertensive diseases in pregnancy and subsequent kidney disease using mGFR in a large biracial cohort.

Transcriptome-Wide Association Study of Blood Cell Traits in African Ancestry and Hispanic/Latino Populations.

Background: Thousands of genetic variants have been associated with hematological traits, though target genes remain unknown at most loci. Moreover, limited analyses have been conducted in African ancestry and Hispanic/Latino populations; hematological trait associated variants more common in these populations have likely been missed. Methods: To derive gene expression prediction models, we used ancestry-stratified datasets from the Multi-Ethnic Study of Atherosclerosis (MESA, including n = 229 African American and n = 381 Hispanic/Latino participants, monocytes) and the Depression Genes and Networks study (DGN, n = 922 European ancestry participants, whole blood). We then performed a transcriptome-wide association study (TWAS) for platelet count, hemoglobin, hematocrit, and white blood cell count in African (n = 27,955) and Hispanic/Latino (n = 28,324) ancestry participants. Results: Our results revealed 24 suggestive signals (p < 1 × 10−4) that were conditionally distinct from known GWAS identified variants and successfully replicated these signals in European ancestry subjects from UK Biobank. We found modestly improved correlation of predicted and measured gene expression in an independent African American cohort (the Genetic Epidemiology Network of Arteriopathy (GENOA) study (n = 802), lymphoblastoid cell lines) using the larger DGN reference panel; however, some genes were well predicted using MESA but not DGN. Conclusions: These analyses demonstrate the importance of performing TWAS and other genetic analyses across diverse populations and of balancing sample size and ancestry background matching when selecting a TWAS reference panel.

Accelerated DNA methylation age and medication use among African Americans.

DNA methylation age acceleration, the discrepancy between epigenetic age and chronological age, is associated with mortality and chronic diseases, including diabetes, hypertension, and hyperlipidemia. In this study, we investigate whether medications commonly used to treat these diseases in 15 drug categories are associated with four epigenetic age acceleration measures: HorvathAge acceleration (HorvathAA), HannumAge acceleration (HannumAA), PhenoAge acceleration, and GrimAge acceleration (GrimAA) using cross-sectional (Phase 1, N=1,100) and longitudinal (Phases 1 and 2, N=266) data from African Americans in the Genetic Epidemiology Network of Arteriopathy (GENOA) study. In cross-sectional analyses, the use of calcium channel blockers was associated with 1.27 years lower HannumAA after adjusting for covariates including hypertension (p=0.001). Longitudinal analyses showed that, compared to those who never used antihypertensives, those who started to take antihypertensives after Phase 1 had a 0.97-year decrease in GrimAA (p=0.007). In addition, compared to those who never used NSAID analgesics, those who started to take them after Phase 1 had a 2.61-year increase in HorvathAA (p=0.0005). Our study demonstrates that three commonly used medications are associated with DNAm age acceleration in African Americans and sheds light on the potential epigenetic effects of pharmaceuticals on aging at the cellular level.

Abstract P141: Association Of Obesity And Cigarette Smoking With Markers Of Inflammation And Thrombosis

Association of obesity and cigarette smoking with markers of inflammation and thrombosis Background: The association between obesity with inflammation and thrombosis has been understudied. The combined association of obesity and cigarette smoking with inflammation and thrombosis also has not been systematically investigated in a well characterized cohort. Methods: We investigated 2549 participants from the Genetic Epidemiology Network of Arteriopathy (GENOA) study (mean age 61±10 years, 64% women, 51% African American). Participants were classified by body mass index (BMI) as normal BMI (n=371), overweight (n= 864), or obese (n= 1314). Obese participants were further classified by self-reported smoking status as having never smoked (n= 747), smoked in the past (n= 454), and currently smoking (n= 113). We compared adjusted associations among these groups with 18 biomarkers of inflammation and 8 biomarkers of thrombosis using generalized estimating equations. Results: After adjusting for potential confounders, individuals who were obese but had never smoked had higher levels of high sensitivity CRP, serum amyloid A, TNFR1 and TNFR2, IL-6, fibrinogen, and VWF compared to participants with normal BMI that were had never smoked (all p&lt;0.05). However, individuals with obesity currently smoking had higher levels of these biomarkers compared to those who never smokers, particularly within the domains of systemic inflammation and cytokines (Table). Compared with participants without obesity who never smoked, the odds of hsCRP &gt;10 milligram/liter in individuals with obesity was 3.6 times for those who currently smoked, and 2.7 times for those who never smoked. Conclusions: In adjusted analyses, obesity is associated with several proinflammatory biomarkers; but when combined with cigarette smoking, this relationship becomes stronger. These findings underscore the need to recommend smoking cessation and weight loss in patients with both of these important risk factors.

Abstract 052: Hypertensive Diseases In Pregnancy And Hemodynamic Stress Later In Life

Background: Hypertensive diseases in pregnancy have been associated with cardiovascular diseases later in life. However, less is known about the relationship between hypertensive diseases in pregnancy and hemodynamic stress later in life. We evaluated the relationship between hypertensive diseases in pregnancy and plasma levels of biomarkers of hemodynamic stress later in life in the Genetic Epidemiology Network of Arteriopathy (GENOA) study. Methods and Results: We investigated 1605 women from the GENOA study (mean age 61±10 years, 57.1% African American).Women were classified as self-reported as nulliparous women (n=140), a history of normotensive pregnancies (n=1,195), a history of a hypertensive pregnancy (n= 229), or a history of preeclampsia (n= 41). We compared adjusted associations among this groups with 4 biomarkers of hemodynamic stress using generalized estimating equations to account for familial clustering. After adjusting for age, race, level of education, smoking history, hypertension, body mass index (BMI), history of coronary artery disease, and diabetes, women with a history of preeclampsia had higher levels of C-terminal proendothelin (CT-proET) compared to women with a history of normotensive pregnancies (Table, p=0.01). There were no significant differences in the levels of midregional proatrial natriuretic peptide (MR-proANP), midregional proadrenomedullin (MR-proADM), and C-Terminal proarginine vasopressin (CT-proAVP) in this groups. Conclusions: Elevated levels of CT-proET (a precursor to the potent vasoconstrictor Endothelin 1) demonstrates a strong relationship among those with a history of preeclampsia. Future studies are warranted to further explore the relationship between CT-proET in the pathogenesis of preeclampsia as well as subsequent changes in cardiovascular structure and function associated with a history of preeclampsia later in life.

Epigenetic age acceleration is associated with cardiometabolic risk factors and clinical cardiovascular disease risk scores in African Americans

BackgroundCardiovascular disease (CVD) is the leading cause of mortality among US adults. African Americans have higher burden of CVD morbidity and mortality compared to any other racial group. Identifying biomarkers for clinical risk prediction of CVD offers an opportunity for precision prevention and earlier intervention.ResultsUsing linear mixed models, we investigated the cross-sectional association between four measures of epigenetic age acceleration (intrinsic (IEAA), extrinsic (EEAA), PhenoAge (PhenoAA), and GrimAge (GrimAA)) and ten cardiometabolic markers of hypertension, insulin resistance, and dyslipidemia in 1,100 primarily hypertensive African Americans from sibships in the Genetic Epidemiology Network of Arteriopathy (GENOA). We then assessed the association between epigenetic age acceleration and time to self-reported incident CVD using frailty hazard models and investigated CVD risk prediction improvement compared to models with clinical risk scores (Framingham risk score (FRS) and the atherosclerotic cardiovascular disease (ASCVD) risk equation). After adjusting for sex and chronological age, increased epigenetic age acceleration was associated with higher systolic blood pressure (IEAA), higher pulse pressure (EEAA and GrimAA), higher fasting glucose (PhenoAA and GrimAA), higher fasting insulin (EEAA), lower low density cholesterol (GrimAA), and higher triglycerides (GrimAA). A five-year increase in GrimAA was associated with CVD incidence with a hazard ratio of 1.54 (95% CI 1.22–2.01) and remained significant after adjusting for CVD risk factors. The addition of GrimAA to risk score models improved model fit using likelihood ratio tests (P = 0.013 for FRS and P = 0.008 for ASCVD), but did not improve C statistics (P > 0.05). Net reclassification index (NRI) showed small but significant improvement in reassignment of risk categories with the addition of GrimAA to FRS (NRI: 0.055, 95% CI 0.040–0.071) and the ASCVD equation (NRI: 0.029, 95% CI 0.006–0.064).ConclusionsEpigenetic age acceleration measures are associated with traditional CVD risk factors in an African-American cohort with a high prevalence of hypertension. GrimAA was associated with CVD incidence and slightly improved prediction of CVD events over clinical risk scores.

Epigenetic loci for blood pressure are associated with hypertensive target organ damage in older African Americans from the genetic epidemiology network of Arteriopathy (GENOA) study

BackgroundHypertension is a major modifiable risk factor for arteriosclerosis that can lead to target organ damage (TOD) of heart, kidneys, and peripheral arteries. A recent epigenome-wide association study for blood pressure (BP) identified 13 CpG sites, but it is not known whether DNA methylation at these sites is also associated with TOD.MethodsIn 1218 African Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study, a cohort of hypertensive sibships, we evaluated the associations between methylation at these 13 CpG sites measured in peripheral blood leukocytes and five TOD traits assessed approximately 5 years later.ResultsTen significant associations were found after adjustment for age, sex, blood cell counts, time difference between CpG and TOD measurement, and 10 genetic principal components (FDR q < 0.1): two with estimated glomerular filtration rate (eGFR, cg06690548, cg10601624), six with urinary albumin-to-creatinine ratio (UACR, cg16246545, cg14476101, cg19693031, cg06690548, cg00574958, cg22304262), and two with left ventricular mass indexed to height (LVMI, cg19693031, cg00574958). All associations with eGFR and four associations with UACR remained significant after further adjustment for body mass index (BMI), smoking status, and diabetes. We also found significant interactions between cg06690548 and BMI on UACR, and between 3 CpG sites (cg19693031, cg14476101, and cg06690548) and diabetes on UACR (FDR q < 0.1). Mediation analysis showed that 4.7% to 38.1% of the relationship between two CpG sites (cg19693031 and cg00574958) and two TOD measures (UACR and LVMI) was mediated by blood pressure (Bonferroni-corrected P < 0.05). Mendelian randomization analysis suggests that methylation at two sites (cg16246545 and cg14476101) in PHGDH may causally influence UACR.ConclusionsIn conclusion, we found compelling evidence for associations between arteriosclerotic traits of kidney and heart and previously identified blood pressure-associated DNA methylation sites. This study may lend insight into the role of DNA methylation in pathological mechanisms underlying target organ damage from hypertension.

Hypertensive diseases in pregnancy, cardiac structure and function later in life: Insights from the Genetic Epidemiology Network of Arteriopathy (GENOA) study.

Hypertensive diseases in pregnancy have been associated with altered cardiac structure and function, yet these associations have not been systematically investigated in larger populations including African Americans. We evaluated the relationships between hypertensive diseases in pregnancy with cardiac structure and function later in life in the Genetic Epidemiology Network of Arteriopathy (GENOA) study. We investigated 1013 African American women sibships with echocardiographic measurements from the GENOA study (Phase II, 2000-05; Jackson, MS). Women were classified as self-reported nulliparous (n=61), a history of normotensive pregnancies (n=780), a history of a hypertensive pregnancies (n=152), or a history of preeclampsia (n=20). We compared adjusted associations among these 4 groups with echocardiographic measurements of cardiac structure and function using generalized estimating equations, accounting for familial clustering. Among 1013 women with echocardiographic data (mean age 62±9.5years), women with a history of hypertensive pregnancy had lower left ventricular ejection fraction (LVEF) (P=0.043) compared to nulliparous women and higher left atrial systolic dimension (LASD) compared to women with a history of normotensive pregnancies (P=0.010), After adjusting for cardiovascular risk factors. There were no statistically significant differences in other echocardiographic parameters among these groups. A history of hypertension in pregnancy is associated with lower LVEF later in life, compared to nulliparous women and higher LASD compared to women with a history of normotensive pregnancies. However, given the multiple comparisons considered, this finding should be interpreted cautiously and requires further study.

Intrinsic and extrinsic epigenetic age acceleration are associated with hypertensive target organ damage in older African Americans

BackgroundEpigenetic age acceleration, a measure of biological aging based on DNA methylation, is associated with cardiovascular mortality. However, little is known about its relationship with hypertensive target organ damage to the heart, kidneys, brain, and peripheral arteries.MethodsWe investigated associations between intrinsic (IEAA) or extrinsic (EEAA) epigenetic age acceleration, blood pressure, and six types of organ damage in a primarily hypertensive cohort of 1390 African Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study. DNA methylation from peripheral blood leukocytes was collected at baseline (1996–2000), and measures of target organ damage were assessed in a follow-up visit (2000–2004). Linear regression with generalized estimating equations was used to test for associations between epigenetic age acceleration and target organ damage, as well as effect modification of epigenetic age by blood pressure or sex. Sequential Oligogenic Linkage Analysis Routines (SOLAR) was used to test for evidence of shared genetic and/or environmental effects between epigenetic age acceleration and organ damage pairs that were significantly associated.ResultsAfter adjustment for sex, chronological age, and time between methylation and organ damage measures, higher IEAA was associated with higher urine albumin to creatinine ratio (UACR, p = 0.004), relative wall thickness (RWT, p = 0.022), and left ventricular mass index (LVMI, p = 0.007), and with lower ankle-brachial index (ABI, p = 0.014). EEAA was associated with higher LVMI (p = 0.005). Target organ damage associations for all but IEAA with LVMI remained significant after further adjustment for blood pressure and antihypertensive use (p < 0.05). Further adjustment for diabetes attenuated the IEAA associations with UACR and RWT, and adjustment for smoking attenuated the IEAA association with ABI. No effect modification by age or sex was observed.ConclusionsMeasures of epigenetic age acceleration may help to better characterize the functional mechanisms underlying organ damage from cellular aging and/or hypertension. These measures may act as subclinical biomarkers for damage to the kidney, heart, and peripheral vasculature; however more research is needed to determine whether these relationships remain independent of lifestyle factors and comorbidities.

Education and Lifestyle Factors Are Associated with DNA Methylation Clocks in Older African Americans.

DNA methylation (DNAm) clocks are important biomarkers of cellular aging and are associated with a variety of age-related chronic diseases and all-cause mortality. Examining the relationship between education and lifestyle risk factors for age-related diseases and multiple DNAm clocks can increase the understanding of how risk factors contribute to aging at the cellular level. This study explored the association between education or lifestyle risk factors for age-related diseases and the acceleration of four DNAm clocks, including intrinsic (IEAA) and extrinsic epigenetic age acceleration (EEAA), PhenoAge acceleration (PhenoAA), and GrimAge acceleration (GrimAA) in the African American participants of the Genetic Epidemiology Network of Arteriopathy. We performed both cross-sectional and longitudinal analyses. In cross-sectional analyses, gender, education, BMI, smoking, and alcohol consumption were all independently associated with GrimAA, whereas only some of them were associated with other clocks. The effect of smoking and education on GrimAA varied by gender. Longitudinal analyses suggest that age and BMI continued to increase GrimAA, and that age and current smoking continued to increase PhenoAA after controlling DNAm clocks at baseline. In conclusion, education and common lifestyle risk factors were associated with multiple DNAm clocks. However, the association with each risk factor varied by clock, which suggests that different clocks may capture adverse effects from different environmental stimuli.

Novel DNA methylation sites associated with cigarette smoking among African Americans

ABSTRACTIntroduction: Cigarette smoking has been associated with adverse health outcomes for mothers and children and is a major contributor to heart disease. Although cigarette smoking is known to affect the epigenome, few studies have been done in African American populations. In this study, we investigated the association between cigarette smoking and DNA methylation (DNAm) among African Americans from the Intergenerational Impact of Genetic and Psychological Factors on Blood Pressure Study (InterGEN), and the Genetic Epidemiology Network of Arteriopathy (GENOA).Methods: The InterGEN study aims to examine the effects of genetic and psychological factors on blood pressure among African American women and their children. Current cigarette smoking was assessed at baseline. DNAm of saliva was assessed using the 850K EPIC Illumina BeadChip for Epigenome-Wide Association analyses. A replication study was conducted among 1100 participants in the GENOA study using the same BeadChip.Results: After controlling for age, body mass index, population structure and cell composition, 26 epigenome-wide significant sites (FDR q < 0.05) were identified, including the AHRR and PHF14 genes associated with atherosclerosis and lung disease, respectively. Six novel CpG sites were discovered in the InterGEN sample and replicated in the GENOA sample. Genes mapped include RARA, FSIP1, ALPP, PIK3R5, KIAA0087, and MGAT3, which were largely associated with cancer development.Conclusion: We observed significant epigenetic associations between smoking and disease-associated genes (e.g., cardiovascular disease, lung cancer). Six novel CpG sites were identified and replicated across saliva and blood samples.

An Exome-Wide Sequencing Study of the GOLDN Cohort Reveals Novel Associations of Coding Variants and Fasting Plasma Lipids.

Background: Associations of both common and rare genetic variants with fasting blood lipids have been extensively studied. However, most of the rare coding variants associated with lipids are population-specific, and exploration of genetic data from diverse population samples may enhance the identification of novel associations with rare variants.Results: We searched for novel coding genetic variants associated with fasting lipid levels in 894 samples from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) with exome-wide sequencing-based genotype data. In single variant tests, one variant (rs11171663 in ITGA7) was associated with fasting triglyceride levels (P = 7.66E-08), explaining approximately 3.2% of the total trait variance. In gene-based tests, we found statistically significant associations between ITGA7 (P = 1.77E-07) and SLCO2A1 (P = 7.18E-07) and triglycerides, as well as between POT1 (P = 3.00E-07) and low-density lipoprotein cholesterol. In another independent replication cohort consisting of 3,183 African American samples from Hypertension Genetic Epidemiology Network (HyperGEN) and the Genetic Epidemiology Network of Arteriopathy (GENOA), the top genes achieved P-values of 0.04 (ITGA7), 0.08 (SLCO2A1), and 0.02 (POT1). In GOLDN, gene transcript levels of ITGA7 and SLCO2A1 were associated with fasting triglycerides (P = 0.07 and P = 0.02), highlighting functional relevance of our findings.Conclusion: In this study, we present preliminary evidence of novel rare variant determinants of fasting lipids, and reveal potential underlying molecular mechanisms. Moreover, these results were replicated in an independent cohort. Our findings may inform novel biomarkers of disease risk and treatment targets.

Longitudinal analysis of epigenome-wide DNA methylation reveals novel smoking-related loci in African Americans

ABSTRACTChanges in DNA methylation may be a potential mechanism that mediates the effects of smoking on physiological function and subsequent disease risk. Given the dynamic nature of the epigenome, longitudinal studies are indispensable for investigating smoking-induced methylation changes over time. Using blood samples collected approximately five years apart in 380 African Americans (mean age 60.7 years) from the Genetic Epidemiology Network of Arteriopathy (GENOA) study, we measured DNA methylation levels using Illumina HumanMethylation BeadChips. We evaluated the association between Phase 1 smoking status and rate of methylation change, using generalized estimating equation models. Among the 6958 CpG sites examined, smoking status was associated with methylation change for 22 CpGs (false discovery rate q < 0.1), with the majority (91%) becoming less methylated over time. Methylation change was greater in ever smokers than never smokers, and the absolute differences in rates of change ranged from 0.18 to 0.77 per decade in M value, equivalent to a value change of 0.013 to 0.047 per decade. Significant enrichment was observed for CpG islands, enhancers, and DNAse hypersensitivity sites (p < 0.05). Although biological pathway analyses were not significant, most of the 22 CpGs were within genes known to be associated with cardiovascular disease, cancers, and aging. In conclusion, we identified epigenetic signatures for cigarette smoking that may have been missed in cross-sectional analyses, providing insight into the epigenetic effect of smoking and highlighting the importance of longitudinal analysis in understanding the dynamic human epigenome.

Higher plasma leptin levels are associated with reduced left ventricular mass and left ventricular diastolic stiffness in black women: insights from the Genetic Epidemiology Network of Arteriopathy (GENOA) study.

Our previous experimental animal data suggest a beneficial effect of leptin on LV structure and function. We hypothesized that leptin levels are associated with lower LV mass and myocardial stiffness which are important risk factors for the development of heart failure with preserved ejection fraction (HFpEF). We evaluated 1172 blacks, in which the prevalence of HFpEF is quite high, with preserved LV ejection fraction (EF > 50%) from the Genetic Epidemiology Network of Arteriopathy Study (mean age 62.9 years, 72% women), a community-based study to identify genes influencing blood pressure and target organ damage due to hypertension. Associations between leptin levels and indices of LV structure and function were evaluated using generalized estimating equations accounting for clustering in siblings. LV myocardial stiffness was evaluated using diastolic wall strain (DWS) measured by echocardiography. Analyses were stratified by sex because leptin levels were three times higher in women than men (p < 0.001). After adjustment for confounders, higher leptin levels were associated with lower LV mass (coefficient for 1 s.d. increase of leptin level: -5.825 g, 95% CI: -9.755 to -1.895 g, P = 0.004) and higher DWS (lower LV stiffness) (coefficient for 1 s.d. increase of leptin level: 0.009, 95% CI: 0.002-0.015, P = 0.007) in women. There were no statistically significant associations in men. In women, there were interactions between leptin levels and body mass index quartiles on LV mass and stiffness (p < 0.05 for both). Higher leptin levels were associated with lower LV mass and stiffness in obese but not lean black women.