Strong Heart Study Participants Research Articles

Multicohort Epigenome-Wide Association Study of All-Cause Cardiovascular Disease and Cancer Incidence: A Cardio-Oncology Approach

BackgroundEmerging evidence reveals a complex relationship between cardiovascular disease (CVD) and cancer, which share common risk factors and biological pathways. ObjectivesThe aim of this study was to evaluate common epigenetic signatures for CVD and cancer incidence in 3 ethnically diverse cohorts: Native Americans from the SHS (Strong Heart Study), European Americans from the FHS (Framingham Heart Study), and European Americans and African Americans from the ARIC (Atherosclerosis Risk In Communities) study. MethodsA 2-stage strategy was used that included first conducting untargeted epigenome-wide association studies for each cohort and then running targeted models in the union set of identified differentially methylated positions (DMPs). We also explored potential molecular pathways by conducting a bioinformatics analysis. ResultsCommon DMPs were identified across all populations. In a subsequent meta-analysis, 3 and 1 of those DMPs were statistically significant for CVD only and both cancer and CVD, respectively. No meta-analyzed DMPs were statistically significant for cancer only. The enrichment analysis pointed to interconnected biological pathways involved in cancer and CVD. In the DrugBank database, elements related to 1-carbon metabolism and cancer and CVD medications were identified as potential drugs for target gene products. In an additional analysis restricted to the 950 SHS participants who developed incident CVD, the C index for incident cancer increased from 0.618 (95% CI: 0.570-0.672) to 0.971 (95% CI: 0.963-0.978) when adjusting the models for the combined cancer and CVD DMPs identified in the other cohorts. ConclusionsThese results point to molecular pathways and potential treatments for precision prevention of CVD and cancer. Screening based on common epigenetic signatures of incident CVD and cancer may help identify patients with newly diagnosed CVD at increased cancer risk.

Arsenic Exposure and Epigenetic Aging: The Association with Cardiovascular Disease and All-Cause Mortality in the Strong Heart Study.

Inorganic arsenic (As) may increase the risk of cardiovascular disease (CVD) and all-cause mortality through accelerated aging, which can be estimated using epigenetic-based measures. We evaluated three DNA methylation-based aging measures (PhenoAge, GrimAge, DunedinPACE) (epigenetic aging measures) as potential mediators of the previously reported association of As exposure with CVD incidence, CVD mortality, and all-cause mortality in the Strong Heart Study (SHS), an epidemiological cohort of American Indian adults. Blood DNA methylation and urinary As levels were measured in 2,323 SHS participants (41.5% men, mean age of 55 years old). PhenoAge and GrimAge values were calculated using a residual-based method. We tested the association of urinary As with epigenetic aging measures using linear regression, the association of epigenetic aging measures with the three health outcomes using additive hazards models, and the mediation of As-related CVD incidence, CVD mortality, and all-cause mortality by epigenetic aging measures using the product of coefficients method. SHS participants with higher vs. lower urinary As levels had similar PhenoAge age, older GrimAge age, and faster DunedinPACE. An interquartile range increase in urinary As was associated with higher of PhenoAge age acceleration [ (0.17, 0.80) years], GrimAge age acceleration [0.80 (0.60, 1.00) years], and DunedinPACE [0.011 (0.005, 0.018)], after adjusting for age, sex, center location, genetic components, smoking status, and body mass index. Of the 347 incident CVD events per 100,000 person-years associated with a doubling in As exposure, 21.3% (9.1, 57.1) and 22.6% (9.5, 56.9), were attributable to differences in GrimAge and DunedinPACE, respectively. Arsenic exposure was associated with older GrimAge and faster DunedinPACE measures of biological age. Furthermore, accelerated biological aging measured from DNA methylation accounted for a relevant fraction of As-associated risk for CVD, CVD mortality, and all-cause mortality in the SHS, supporting the role of As in accelerated aging. Research of the biological underpinnings can contribute to a better understanding of the role of aging in arsenic-related disease. https://doi.org/10.1289/EHP11981.

Metal mixtures and DNA methylation measures of biological aging in American Indian populations

IntroductionNative American communities suffer disproportionately from elevated metal exposures and increased risk for cardiovascular diseases and diabetes. DNA methylation is a sensitive biomarker of aging-related processes and novel epigenetic-based “clocks” can be used to estimate accelerated biological aging that may underlie increased risk. Metals alter DNA methylation, yet little is known about their individual and combined impact on epigenetic age acceleration. Our objective was to investigate the associations of metals on several DNA methylation-based aging measures in the Strong Heart Study (SHS) cohort. MethodsBlood DNA methylation data from 2,301 SHS participants was used to calculate age acceleration of epigenetic clocks (PhenoAge, GrimAge, DunedinPACE, Hannum, Horvath). Urinary metals [arsenic (As), cadmium (Cd), tungsten (W), zinc (Zn), selenium (Se), molybdenum (Mo)] were creatinine-adjusted and categorized into quartiles. We examined associations of individual metals through linear regression models and used Bayesian Kernel Machine Regression (BKMR) for the impact of the total metal mixture on epigenetic age acceleration. ResultsThe mixture of nonessential metals (W, As, Cd) was associated with greater GrimAge acceleration and DunedinPACE, while the essential metal mixture (Se, Zn, Mo) was associated with lower epigenetic age acceleration. Cd was associated with increased epigenetic age acceleration across all clocks and BKMR analysis suggested nonlinear associations between Se and DunedinPACE, GrimAge, and PhenoAge acceleration. No interactions between individual metals were observed. The associations between Cd, Zn, and epigenetic age acceleration were greater in never smokers in comparison to current/former smokers. ConclusionNonessential metals were positively associated with greater epigenetic age acceleration, with strongest associations observed between Cd and DunedinPACE and GrimAge acceleration. In contrast, essential metals were associated with lower epigenetic aging. Examining the influence of metal mixtures on epigenetic age acceleration can provide insight into metals and aging-related diseases.

Abstract P373: Health Care Access and Usage Patterns Among Native Americans: The Strong Heart Study

Introduction: Previous research has shown that health care access and usage patterns among Native Americans are often difficult to measure. Hypothesis: We hypothesize that sociodemographic factors such as age, gender, education, and employment influence health care access and usage patterns in Native communities in the Strong Heart Study (SHS). Methods: The SHS is a prospective population-based epidemiological study of cardiovascular disease and its associated risk factors in American Indians (AI). Between 1997 and 1999, surviving participants (N=2,382) of the original cohort were invited to a third exam, in which health care access and usage information were collected, along with other clinical and sociodemographic measurements. Multivariate logistic regression was used to find influencing factors of health care choices. Results: The majority of study participants (79%, 1,877/2,382) reported Indian Health Services (IHS) as their primary source of care, and close to one-third (29%, 689/2,358) reported having no additional coverage. Figure 1 showed travel time, waiting time after arriving at the clinics, and waiting time of a walk-in visit in IHS, tribal health service, and private practice. As participants aging or obtaining more years of education, they were less likely to use public (IHS or tribal) health service vs. private practice with odds ratio (95% confidence interval) 0.97 (0.95-0.99, p<0.01) and 0.89 (0.84-0.93, p<0.01) respectively, adjusting for gender and employment status. Conclusions: SHS participants primarily utilize IHS compared to other health services. Average waiting time is longer for IHS facilities (vs. private practice or tribal health facilities) with 35% (622/1,760) participants waiting for > 60 minutes to be seen in regular appointments, and with 53% (814/1,540) participants waiting for > 60 minutes in a walk-in visit. Age and education influence access to and selection of health care services for AI. This report provides baseline information for future health care access study in SHS.

Urinary Zinc and Incident Type 2 Diabetes: Prospective Evidence From the Strong Heart Study.

Hyperglycemia can increase urinary zinc excretion. We evaluated the association of higher urinary zinc level with new diagnosis of incident type 2 diabetes mellitus (T2DM) in adult populations with a high burden of T2DM from AZ, OK, and ND and SD. We also assessed the cross-sectional association of urinary zinc levels with prevalent prediabetes. We included 1,339 adults free of T2DM at baseline (1989-1991) followed through 1998-1999 in the Strong Heart Study (SHS) and 1,905 family members of SHS participants followed as part of the Strong Heart Family Study (SHFS) through 2006-2009. T2DM incidence was 14.7% (mean follow-up 6.6 years) in the SHS and 13.5% (mean follow-up 5.6 years) in the SHFS. After adjustment for sex, site, education, smoking status, BMI, and estimated glomerular filtration rate, the hazard ratio of T2DM in comparing 75th vs. 25th percentiles of urinary zinc distribution was 1.21 (95% CI 1.08, 1.36) in the SHS and 1.12 (0.96, 1.31) in the SHFS. These associations were attenuated but significant in the SHS after adjustment for HOMA of insulin resistance (HOMA-IR) score. With exclusion of participants with prediabetes at baseline, urinary zinc remained significantly associated with T2DM in the SHS. In cross-sectional analyses, prediabetes was associated with higher urinary zinc levels. Urinary zinc levels were associated with T2DM incidence and prediabetes prevalence even after adjustment for HOMA-IR in populations with a high burden of T2DM. These results highlight the importance of zinc metabolism in diabetes development.

Rare, Protein-Altering Variants in AS3MT and Arsenic Metabolism Efficiency: A Multi-Population Association Study.

Background:Common genetic variation in the arsenic methyltransferase (AS3MT) gene region is known to be associated with arsenic metabolism efficiency (AME), measured as the percentage of dimethylarsinic acid (DMA%) in the urine. Rare, protein-altering variants in AS3MT could have even larger effects on AME, but their contribution to AME has not been investigated.Objectives:We estimated the impact of rare, protein-coding variation in AS3MT on AME using a multi-population approach to facilitate the discovery of population-specific and shared causal rare variants.Methods:We generated targeted DNA sequencing data for the coding regions of AS3MT for three arsenic-exposed cohorts with existing data on arsenic species measured in urine: Health Effects of Arsenic Longitudinal Study (HEALS, ), Strong Heart Study (SHS, ), and New Hampshire Skin Cancer Study (NHSCS, ). We assessed the collective effects of rare (allele frequency ), protein-altering AS3MT variants on DMA%, using multiple approaches, including a test of the association between rare allele carrier status (yes/no) and DMA% using linear regression (adjusted for common variants in 10q24.32 region, age, sex, and population structure).Results:We identified 23 carriers of rare-protein-altering AS3MT variant across all cohorts (13 in HEALS and 5 in both SHS and NHSCS), including 6 carriers of predicted loss-of-function variants. DMA% was 6–10% lower in carriers compared with noncarriers in HEALS [ (95% CI: , )], SHS [ (95% CI: , )], and NHSCS [ (95% CI: , )]. In meta-analyses across cohorts, DMA% was 8.7% lower in carriers [ (95% CI: , )].Discussion:Rare, protein-altering variants in AS3MT were associated with lower mean DMA%, an indicator of reduced AME. Although a small percentage of the population (0.5–0.7%) carry these variants, they are associated with a 6–10% decrease in DMA% that is consistent across multiple ancestral and environmental backgrounds. https://doi.org/10.1289/EHP8152

DNA methylation and cancer incidence: lymphatic\u2013hematopoietic versus solid cancers in the Strong Heart Study

BackgroundEpigenetic alterations may contribute to early detection of cancer. We evaluated the association of blood DNA methylation with lymphatic–hematopoietic cancers and, for comparison, with solid cancers. We also evaluated the predictive ability of DNA methylation for lymphatic–hematopoietic cancers.MethodsBlood DNA methylation was measured using the Illumina Infinium methylationEPIC array in 2324 Strong Heart Study participants (41.4% men, mean age 56 years). 788,368 CpG sites were available for differential DNA methylation analysis for lymphatic–hematopoietic, solid and overall cancers using elastic-net and Cox regression models. We conducted replication in an independent population: the Framingham Heart Study. We also analyzed differential variability and conducted bioinformatic analyses to assess for potential biological mechanisms.ResultsOver a follow-up of up to 28 years (mean 15), we identified 41 lymphatic–hematopoietic and 394 solid cancer cases. A total of 126 CpGs for lymphatic–hematopoietic cancers, 396 for solid cancers, and 414 for overall cancers were selected as predictors by the elastic-net model. For lymphatic–hematopoietic cancers, the predictive ability (C index) increased from 0.58 to 0.87 when adding these 126 CpGs to the risk factor model in the discovery set. The association was replicated with hazard ratios in the same direction in 28 CpGs in the Framingham Heart Study. When considering the association of variability, rather than mean differences, we found 432 differentially variable regions for lymphatic–hematopoietic cancers.ConclusionsThis study suggests that differential methylation and differential variability in blood DNA methylation are associated with lymphatic–hematopoietic cancer risk. DNA methylation data may contribute to early detection of lymphatic–hematopoietic cancers.

Blood-based DNA methylation biomarkers for cumulative lead exposure: associations with cardiovascular disease incidence and mortality in the Strong Heart Study

Lead is a ubiquitous toxicant associated with increased cardiovascular disease (CVD) risk. Blood and bone (patella and tibia) lead are established biomarkers of cumulative lead exposure, but because specialized technologies are needed for analysis, they are typically not available for clinical and epidemiological applications. We recently developed and validated three polygenic biomarkers that estimate lead exposure in blood, patella, and tibia samples based only on blood DNA methylation (DNAm) data. Whether these methylation-biomarkers predict lead-related CVD risk is unknown. We thus investigated the associations of these DNAm lead biomarkers with CVD incidence and mortality in the Strong Heart Study (SHS), a population-based cohort study of CVD in American Indian adults recruited in 1989-1991. The three DNAm lead biomarkers were computed from Illumina EPIC BeadChip blood DNAm data available at baseline among 2,321 SHS participants aged 45-75 years (~41% male). During a median follow-up of ~20 years, 1,023 participants had incident CVD events and 452 died due to CVD. After adjustment for sociodemographic and cardiovascular risk factors, the three DNAm lead biomarkers were associated with CVD mortality, but not with non-fatal CVD events. The hazard ratios (95% CI) for CVD mortality were 1.15 (1.01 - 1.31), 1.12 (1.01 - 1.25), and 1.20 (1.06 - 1.37) per interquartile increase in DNAm-estimated blood, patella, and tibia lead biomarkers. All biomarkers were also associated with coronary heart disease mortality. In subgroup analyses, the associations of lead biomarkers with CVD mortality were stronger in males and ever smokers. These newly developed DNAm lead biomarkers may aid in identifying individuals at risk for CVD mortality resulted from cumulative lead exposure.

Depression Symptoms and Cognitive Test Performance in Older American Indians: The Strong Heart Study.

American Indians have excess risk of depression, which can contribute to cerebrovascular and cognitive disability, with effects on memory, processing speed, executive function, and visuospatial ability. However, studies examining depression and cognition in American Indians are limited; this study aims to report associations of depression with general cognition, verbal fluency and memory, and processing speed. Cohort study. The Cerebrovascular Disease and its Consequences in American Indians study was an ancillary examination of Strong Heart Study participants from 3 U.S. regions. All eligible were included in this analysis (N=818). Participants completed evaluations for depressive symptomology, cognition, and physical function-including Center for Epidemiologic Studies Depression (CESD), Modified Mini-Mental State Examination (3MSE), Wechsler Adult Intelligence Scale-Fourth Edition coding (WAIS), Controlled Oral Word Association (COWA), California Verbal and Learning Test, Halstead finger tapping, grip strength, and Short Physical Performance Battery (SPPB) tests. Linear mixed models were adjusted for site, age, sex, education, income, marital status, alcohol, smoking, diabetes, hypertension, obesity, cholesterol, stroke, infarct, and hemorrhage. Symptoms of depression were common, with 20% (N=138) endorsing CES-D scores of 16+. More depressive symptoms were associated with older age, female sex, lower education, lower income, non-married status, not using alcohol, not smoking, hypertension, diabetes, and stroke. In adjusted analyses, processing speed (WAIS: β -0.13, 95%CI -0.25, -0.03), general cognition (3MSE: β -0.10, 95%CI -0.17, -0.03), verbal fluency (COWA: β -0.10, 95%CI -0.19, -0.01), and motor function (SPPB: β -0.05, 95%CI -0.07, -0.03) were significantly associated with more symptoms of depression. These findings maybe informative for health disparities populations, especially those with depressive risk. Clinicians may require particular training in cultural humility. Future studies should validate use of the CES-D scale in this population; longitudinal studies may focus on causal mechanisms and potential secondary prevention, such as social support. J Am Geriatr Soc 68:1739-1747, 2020.

Cadmium body burden, hypertension, and changes in blood pressure over time: results from a prospective cohort study in American Indians

American Indian communities are at greater risk of hypertension and cardiovascular disease than the general US population and are exposed to greater cadmium levels. However, cadmium's effect on blood pressure is unclear. This study assesses the association between baseline urinary cadmium and longitudinal changes in blood pressure in American Indian communities. Cadmium was measured in 3047 baseline urine samples from Strong Heart Study participants from three geographic areas. Longitudinal changes in blood pressure across three study visits (1989–1999) were modeled using linear mixed models by baseline log urinary cadmium to creatinine ratio. Hypertension risk was evaluated using interval-censored survival analysis. Higher levels of urinary cadmium at baseline were associated with faster rates of increase in diastolic and systolic blood pressure (P [trend] = .001 and .02, respectively). The estimated change in diastolic and systolic blood pressures per year was 0.18 mm Hg (0.05–0.31) and 0.62 mm Hg (0.37–0.87) in the upper quintile of cadmium level compared with −0.11 mm Hg (−0.24 to 0.02) and 0.21 mm Hg (−0.04 to 0.46) in the lowest, respectively. A one-unit increase in log-transformed urinary cadmium was associated with 10% greater hypertension risk (95% confidence interval: 1.01–1.20). In conclusion, blood pressure of individuals with greater baseline levels of urinary cadmium increased at a faster rate relative to those with lower levels.

Comparison of QRS Duration and Associated Cardiovascular Events in American Indian Men Versus Women (The Strong Heart Study)

Electrocardiographic QRS duration at rest is associated with sudden cardiac death and death from coronary heart disease in the general population. However, its relation to cardiovascular events in American Indians, a population with persistently high cardiovascular disease mortality, is unknown. The relation of QRS duration to incident cardiovascular disease during 17.2years of follow-up was assessed in 1,851 male and female Strong Heart Study participants aged 45 to 74years without known cardiovascular disease at baseline. Cox regression with robust standard error estimates was used to determine the association between quintiles of QRS duration and incident cardiovascular disease in gender-stratified analyses, adjusted for age, systolic blood pressure, hypertension, antihypertensive medication use, body mass index, current smoking, diabetes, total cholesterol, high-density lipoprotein cholesterol, and albuminuria. In women only, QRS duration in the highest quintile (≥105ms) conferred significantly higher risk of cardiovascular disease than QRS duration in the lowest quintile (64 to 84ms) (hazard ratio 1.6, 95% CI 1.1 to 2.4) likely because of higher risks of coronary heart disease (hazard ratio 1.8, 95% CI 1.1 to 3.1) and myocardial infarction (hazard ratio 2.1, 95% CI 1.0 to 4.7). Furthermore, when added to the Strong Heart Study Coronary Heart Disease Risk Calculator, QRS duration significantly improved prediction of future coronary heart disease events in women (Net Reclassification Index 0.17, 95% CI 0.06 to 0.47). In conclusion, QRS duration is an independent predictor of cardiovascular disease in women in the Strong Heart Study cohort and may have value in estimating risk in populations with similar risk profiles and a high lifetime incidence of cardiovascular disease.

Risk Factors and Prediction of Stroke in a Population with High Prevalence of Diabetes: The Strong Heart Study.

Background and ObjectiveAmerican Indians have a high prevalence of diabetes and higher incidence of stroke than that of whites and blacks in the U.S. Stroke risk prediction models based on data from American Indians would be of clinical and public health value.Methods and ResultsA total of 3483 (2043 women) Strong Heart Study participants free of stroke at baseline were followed from 1989 to 2010 for incident stroke. Overall, 297 stroke cases (179 women) were identified. Cox models with stroke-free time and risk factors recorded at baseline were used to develop stroke risk prediction models. Assessment of the developed stroke risk prediction models regarding discrimination and calibration was performed by an analogous C-statistic (C) and a version of the Hosmer-Lemeshow statistic (HL), respectively, and validated internally through use of Bootstrapping methods.ResultsAge, smoking status, alcohol consumption, waist circumference, hypertension status, an-tihypertensive therapy, fasting plasma glucose, diabetes medications, high/low density lipoproteins, urinary albumin/creatinine ratio, history of coronary heart disease/heart failure, atrial fibrillation, or Left ventricular hypertrophy, and parental history of stroke were identified as the significant optimal risk factors for incident stroke.DiscussionThe models produced a C = 0.761 and HL = 4.668 (p = 0.792) for women, and a C = 0.765 and HL = 9.171 (p = 0.328) for men, showing good discrimination and calibration.ConclusionsOur stroke risk prediction models provide a mechanism for stroke risk assessment designed for American Indians. The models may be also useful to other populations with high prevalence of obesity and/or diabetes for screening individuals for risk of incident stroke and designing prevention programs.

Metal mixtures in urban and rural populations in the US: The Multi-Ethnic Study of Atherosclerosis and the Strong Heart Study

BackgroundNatural and anthropogenic sources of metal exposure differ for urban and rural residents. We searched to identify patterns of metal mixtures which could suggest common environmental sources and/or metabolic pathways of different urinary metals, and compared metal-mixtures in two population-based studies from urban/sub-urban and rural/town areas in the US: the Multi-Ethnic Study of Atherosclerosis (MESA) and the Strong Heart Study (SHS). MethodsWe studied a random sample of 308 White, Black, Chinese-American, and Hispanic participants in MESA (2000–2002) and 277 American Indian participants in SHS (1998–2003). We used principal component analysis (PCA), cluster analysis (CA), and linear discriminant analysis (LDA) to evaluate nine urinary metals (antimony [Sb], arsenic [As], cadmium [Cd], lead [Pb], molybdenum [Mo], selenium [Se], tungsten [W], uranium [U] and zinc [Zn]). For arsenic, we used the sum of inorganic and methylated species (∑As). ResultsAll nine urinary metals were higher in SHS compared to MESA participants. PCA and CA revealed the same patterns in SHS, suggesting 4 distinct principal components (PC) or clusters (∑As-U-W, Pb-Sb, Cd-Zn, Mo-Se). In MESA, CA showed 2 large clusters (∑As-Mo-Sb-U-W, Cd-Pb-Se-Zn), while PCA showed 4 PCs (Sb-U-W, Pb-Se-Zn, Cd-Mo, ∑As). LDA indicated that ∑As, U, W, and Zn were the most discriminant variables distinguishing MESA and SHS participants. ConclusionsIn SHS, the ∑As-U-W cluster and PC might reflect groundwater contamination in rural areas, and the Cd-Zn cluster and PC could reflect common sources from meat products or metabolic interactions. Among the metals assayed, ∑As, U, W and Zn differed the most between MESA and SHS, possibly reflecting disproportionate exposure from drinking water and perhaps food in rural Native communities compared to urban communities around the US.

Linkage Analysis of Urine Arsenic Species Patterns in the Strong Heart Family Study.

Arsenic toxicokinetics are important for disease risks in exposed populations, but genetic determinants are not fully understood. We examined urine arsenic species patterns measured by HPLC-ICPMS among 2189 Strong Heart Study participants 18 years of age and older with data on ~400 genome-wide microsatellite markers spaced ~10 cM and arsenic speciation (683 participants from Arizona, 684 from Oklahoma, and 822 from North and South Dakota). We logit-transformed % arsenic species (% inorganic arsenic, %MMA, and %DMA) and also conducted principal component analyses of the logit % arsenic species. We used inverse-normalized residuals from multivariable-adjusted polygenic heritability analysis for multipoint variance components linkage analysis. We also examined the contribution of polymorphisms in the arsenic metabolism gene AS3MT via conditional linkage analysis. We localized a quantitative trait locus (QTL) on chromosome 10 (LOD 4.12 for %MMA, 4.65 for %DMA, and 4.84 for the first principal component of logit % arsenic species). This peak was partially but not fully explained by measured AS3MT variants. We also localized a QTL for the second principal component of logit % arsenic species on chromosome 5 (LOD 4.21) that was not evident from considering % arsenic species individually. Some other loci were suggestive or significant for 1 geographical area but not overall across all areas, indicating possible locus heterogeneity. This genome-wide linkage scan suggests genetic determinants of arsenic toxicokinetics to be identified by future fine-mapping, and illustrates the utility of principal component analysis as a novel approach that considers % arsenic species jointly.

Association of Global DNA Methylation and Global DNA Hydroxymethylation with Metals and Other Exposures in Human Blood DNA Samples

Background: The association between human blood DNA global methylation and global hydroxymethylation has not been evaluated in population-based studies. No studies have evaluated environmental determinants of global DNA hydroxymethylation, including exposure to metals.Objective: We evaluated the association between global DNA methylation and global DNA hydroxymethylation in 48 Strong Heart Study participants for which selected metals had been measured in urine at baseline and DNA was available from 1989–1991 (visit 1) and 1998–1999 (visit 3).Methods: We measured the percentage of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in samples using capture and detection antibodies followed by colorimetric quantification. We explored the association of participant characteristics (i.e., age, adiposity, smoking, and metal exposure) with both global DNA methylation and global DNA hydroxymethylation.Results: The Spearman’s correlation coefficient for 5-mC and 5-hmC levels was 0.32 (p = 0.03) at visit 1 and 0.54 (p < 0.001) at visit 3. Trends for both epigenetic modifications were consistent across potential determinants. In cross-sectional analyses, the odds ratios of methylated and hydroxymethylated DNA were 1.56 (95% CI: 0.95, 2.57) and 1.76 (95% CI: 1.07, 2.88), respectively, for the comparison of participants above and below the median percentage of dimethylarsinate. The corresponding odds ratios were 1.64 (95% CI: 1.02, 2.65) and 1.16 (95% CI: 0.70, 1.94), respectively, for the comparison of participants above and below the median cadmium level. Arsenic exposure and metabolism were consistently associated with both epigenetic markers in cross-sectional and prospective analyses. The positive correlation of 5-mC and 5-hmC levels was confirmed in an independent study population.Conclusions: Our findings support that both epigenetic measures are related at the population level. The consistent trends in the associations between these two epigenetic modifications and the characteristics evaluated, especially arsenic exposure and metabolism, suggest the need for understanding which of the two measures is a better biomarker for environmental epigenetic effects in future large-scale epidemiologic studies.Citation: Tellez-Plaza M, Tang WY, Shang Y, Umans JG, Francesconi KA, Goessler W, Ledesma M, Leon M, Laclaustra M, Pollak J, Guallar E, Cole SA, Fallin MD, Navas-Acien A. 2014. Association of global DNA methylation and global DNA hydroxymethylation with metals and other exposures in human blood DNA samples. Environ Health Perspect 122:946–954; http://dx.doi.org/10.1289/ehp.1306674

Body composition and arsenic metabolism: a cross-sectional analysis in the Strong Heart Study.

ObjectiveThe objective of this study was to evaluate the association between measures of body composition and patterns of urine arsenic metabolites in the 1989–1991 baseline visit of the Strong Heart Study, a cardiovascular disease cohort of adults recruited from rural communities in Arizona, Oklahoma, North Dakota and South Dakota.MethodsWe evaluated 3,663 Strong Heart Study participants with urine arsenic species above the limit of detection and no missing data on body mass index, % body fat and fat free mass measured by bioelectrical impedance, waist circumference and other variables. We summarized urine arsenic species patterns as the relative contribution of inorganic (iAs), methylarsonate (MMA) and dimethylarsinate (DMA) species to their sum. We modeled the associations of % arsenic species biomarkers with body mass index, % body fat, fat free mass, and waist circumference categories in unadjusted regression models and in models including all measures of body composition. We also considered adjustment for arsenic exposure and demographics.ResultsIncreasing body mass index was associated with higher mean % DMA and lower mean % MMA before and after adjustment for sociodemographic variables, arsenic exposure, and for other measures of body composition. In unadjusted linear regression models, % DMA was 2.4 (2.1, 2.6) % higher per increase in body mass index category (< 25, ≥25 & <30, ≥30 & <35, ≥35 kg/m2), and % MMA was 1.6 (1.4, 1.7) % lower. Similar patterns were observed for % body fat, fat free mass, and waist circumference measures in unadjusted models and in models adjusted for potential confounders, but the associations were largely attenuated or disappeared when adjusted for body mass index.ConclusionMeasures of body size, especially body mass index, are associated with arsenic metabolism biomarkers. The association may be related to adiposity, fat free mass or body size. Future epidemiologic studies of arsenic should consider body mass index as a potential modifier for arsenic-related health effects.

Global DNA Methylation and Global Hydroxymethylation in a Population-based Pilot Sample from the Strong Heart Study

Background: The association between human blood DNA global methylation and global hydroxymethylation has not been evaluated in population-based studies. No studies have evaluated environmental determinants of global DNA hydroxymethylation, including exposure to metals. Aims: To evaluate the association between global DNA methylation and global DNA hydroxymethylation in a subsample of 48 Strong Heart Study participants who had selected metals measured in urine at baseline and DNA available in 1989-1991 and 1998-1999. Methods: Global 5-methylcytosine (5-mC) and 5-hydroxymethyl-cytosine (5-hmC) levels in DNA were measured by capture and detection antibodies followed by colorimetric quantification. We used linear regression models to evaluate trends and compare relative differences in methylation and hydroxymethylation levels by participant characteristics (age, sex, education, adiposity, smoking, alcohol intake, metal exposure and arsenic metabolism). Results: The Spearman’s correlation coefficient for 5-mC and 5-hmC levels was 0.32 (p –value = 0.03) at visit 1 and 0.54 (p – value &lt; 0.001) at visit 3, with consistent trends for both epigenetic markers across characteristics. The associations were significant for urine cadmium concentrations and global methylation and for arsenic metabolism and global hydroxymethylation. Conclusions: Our findings support that both epigenetic measures are related at the population level. The consistent trends in the associations between these epigenetic modifications and the characteristics evaluated suggest the need for understanding which of the two measures is a better biomarker for environmental epigenetic effects in future large-scale epidemiologic studies.

Heritability and Preliminary Genome-Wide Linkage Analysis of Arsenic Metabolites in Urine

Background: Arsenic (III) methyltransferase (AS3MT) has been related to urine arsenic metabolites in association studies. Other genes might also play roles in arsenic metabolism and excretion.Objective: We evaluated genetic determinants of urine arsenic metabolites in American Indian adults from the Strong Heart Study (SHS).Methods: We evaluated heritability of urine arsenic metabolites [percent inorganic arsenic (%iAs), percent monomethylarsonate (%MMA), and percent dimethylarsinate (%DMA)] in 2,907 SHS participants with urine arsenic measurements and at least one relative within the cohort. We conducted a preliminary linkage analysis in a subset of 487 participants with available genotypes on approximately 400 short tandem repeat markers using a general pedigree variance component approach for localizing quantitative trait loci (QTL).Results: The medians (interquartile ranges) for %iAs, %MMA, and %DMA were 7.7% (5.4–10.7%), 13.6% (10.5–17.1%), and 78.4% (72.5–83.1%), respectively. The estimated heritability was 53% for %iAs, 50% for %MMA, and 59% for %DMA. After adjustment for sex, age, smoking, body mass index, alcohol consumption, region, and total urine arsenic concentrations, LOD [logarithm (to the base of 10) of the odds] scores indicated suggestive evidence for genetic linkage with QTLs influencing urine arsenic metabolites on chromosomes 5 (LOD = 2.03 for %iAs), 9 (LOD = 2.05 for %iAs and 2.10 for %MMA), and 11 (LOD = 1.94 for %iAs). A peak for %DMA on chromosome 10 within 2 Mb of AS3MT had an LOD of 1.80.Conclusions: This population-based family study in American Indian communities supports a genetic contribution to variation in the distribution of arsenic metabolites in urine and, potentially, the involvement of genes other than AS3MT.

Comparison of Estimated Glomerular Filtration Rates and Albuminuria in Predicting Risk of Coronary Heart Disease in a Population With High Prevalence of Diabetes Mellitus and Renal Disease

Improved accuracy in predicting coronary heart disease (CHD) risk in patients with diabetes and kidney disease is needed. The addition of albuminuria to established methods of CHD risk calculation was reported in the Strong Heart Study (SHS) cohort. In this study, the addition of estimated glomerular filtration rate (eGFR) was evaluated using data from 4,549 American Indian SHS participants aged 45 to 74 years. After adjustment for Framingham CHD risk factors, hazard ratios for eGFR as a predictor of CHD were 1.69 (95% confidence interval 1.34 to 2.13) in women and 1.41 (95% confidence interval 0.94 to 2.13) in men. Models including albuminuria, eGFR, or both scored higher in discriminatory power than models using conventional risk factors alone in women; in men, the improvement was seen only for albuminuria and the combination of albuminuria and eGFR. Hosmer-Lemeshow assessments showed good calibration for the models using eGFR alone in both genders, followed by models including albuminuria alone in both genders. Adding eGFR improved the net reclassification improvement (NRI) in women (0.085, p = 0.0004) but not in men (0.010, p = 0.1967). NRI and integrated discrimination improvement (IDI) were improved in both genders using albuminuria and eGFR (NRI 0.135, p <0.0001, and IDI 0.027, p <0.0001 in women; NRI 0.035, p <0.0196, and IDI 0.008, p <0.0156 in men). Therefore, a risk calculator including albuminuria enhances CHD prediction compared to a calculator using only standard risk factors in men and women. Including eGFR alone improves risk prediction in women, but for men, it is preferable to include eGFR and albuminuria. In conclusion, this enhanced calculator should be useful in estimating CHD risk in populations with high prevalence of diabetes and renal disease.

Dietary Calcium Is Associated with Body Mass Index and Body Fat in American Indians , ,

American Indians have a high prevalence of obesity. Evidence supports a relationship between increased dietary calcium intake and lower body weight. This study was conducted to investigate the association between dietary calcium intake, BMI, and percentage of body fat (PBF) in American Indians (ages 47–79 y) in the Strong Heart Study (SHS) (2nd exam, 1992–1995). SHS data were compared with data for the general U.S. adult population from the NHANES III (1988–1994). BMI was calculated as kg/m2. PBF was estimated by bioelectrical impedance using an equation based on total body water. The clinical examination included measures of blood chemistry. Dietary data were collected using a 24-h dietary recall. Calcium intake was significantly lower in SHS participants than in age-matched NHANES III participants. Mean calcium intake in the SHS was 680 mg/d (range: 103–4574 mg/d) for men and 610 mg/d (range: 71–4093 mg/d) for women (P < 0.001). After adjustment for potential confounders, BMI and PBF were lower by 0.80 kg/m2 (95% CI: −1.53 to −0.08, P = 0.046) and 1.28% (95% CI: −2.10 to −0.47, P = 0.011) in SHS participants with higher (≥873 mg/d in the 5th quintile) vs. lower calcium intake (<313 mg/d in the 1st quintile). No relation between calcium intake and BMI or PBF was observed in NHANES III participants. Our data may be used to develop nutritional interventions aimed at weight control in culturally appropriate clinical trials.