History of Cardiovascular Disease, Intensive Lifestyle Intervention, and Cardiovascular Outcomes in the Look AHEAD Trial

OBJECTIVE

To examine the effects of an intensive lifestyle intervention (ILI) on cardiovascular disease (CVD), the Action for Health in Diabetes (Look AHEAD) trial randomized 5,145 participants with type 2 diabetes and overweight/obesity to a ILI or diabetes support and education. Although the primary outcome did not differ between the groups, there was suggestive evidence of heterogeneity for prespecified baseline CVD history subgroups (interaction P = 0.063). Event rates were higher in the ILI group among those with a CVD history (hazard ratio 1.13 [95% CI: 0.90-1.41]) and lower among those without CVD (hazard ratio 0.86 [95% CI: 0.72-1.02]).

METHODS

This study conducted post hoc analyses of the rates of the primary composite outcome and components, adjudicated cardiovascular death, nonfatal myocardial infarction (MI), stroke, and hospitalization for angina, as well as three secondary composite cardiovascular outcomes.

RESULTS

Interaction P values for the primary and two secondary composites were similar (0.060-0.064). Of components, the interaction was significant for nonfatal MI (P = 0.035). This interaction was not due to confounding by baseline variables, different intervention responses for weight loss and physical fitness, or hypoglycemic events. In those with a CVD history, statin use was high and similar by group. In those without a CVD history, low-density lipoprotein cholesterol levels were higher (P = 0.003) and statin use was lower (P ≤ 0.001) in the ILI group.

CONCLUSIONS

Intervention response heterogeneity was significant for nonfatal MI. Response heterogeneity may need consideration in a CVD-outcome trial design.

Sex- and Race-Related Differences in Liver-Associated Serum Chemistry Tests in Young Adults in the Cardia Study

Simultaneous multiple automated analyses of liver function can be performed quickly and cheaply, but their usefulness in mass screening is questionable. Reference intervals are frequently applied without regard to race and sex, despite the fact that reported values may vary considerably in relation to these factors. Serum analyte results for greater than 5000 black and white men and women in the CARDIA Study showed clinically and statistically significant differences by race and sex for values of aspartate aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, total bilirubin, total protein, and albumin; these differences were not explained by differences in age, body mass, reported ethanol intake, smoking, or oral contraceptive use. Results for at least one of these six tests were out of range in 38% of the men and 19% of the women. Sex- and race-specific reference intervals are recommended to decrease the frequency of values reported as abnormal in otherwise healthy young adults.

Multi-ancestry sleep-by-SNP interaction analysis in 126,926 individuals reveals lipid loci stratified by sleep duration

Both short and long sleep are associated with an adverse lipid profile, likely through different biological pathways. To elucidate the biology of sleep-associated adverse lipid profile, we conduct multi-ancestry genome-wide sleep-SNP interaction analyses on three lipid traits (HDL-c, LDL-c and triglycerides). In the total study sample (discovery + replication) of 126,926 individuals from 5 different ancestry groups, when considering either long or short total sleep time interactions in joint analyses, we identify 49 previously unreported lipid loci, and 10 additional previously unreported lipid loci in a restricted sample of European-ancestry cohorts. In addition, we identify new gene-sleep interactions for known lipid loci such as LPL and PCSK9. The previously unreported lipid loci have a modest explained variance in lipid levels: most notable, gene-short-sleep interactions explain 4.25% of the variance in triglyceride level. Collectively, these findings contribute to our understanding of the biological mechanisms involved in sleep-associated adverse lipid profiles.

Sleep duration is associated with an adverse lipid profile. Here, the authors perform genome-wide gene-by-sleep interaction analysis and find 49 previously unreported lipid loci when considering short or long total sleep time.

Associations Between Left Ventricular Structure, Function, and Cerebral Amyloid: The ARIC-PET Study

Background and Purpose- Cardiovascular disease is a known risk factor for cognitive decline, although the mechanisms remain unclear. We hypothesize that Aβ (β-amyloid), a core pathology of Alzheimer's disease, will be associated with subclinical cardiac structure and function echocardiogram indices. Methods- Three hundred six nondemented participants from the ARIC study (Atherosclerosis Risk in Communities Study) underwent florbetapir positron emission tomography and 2D echocardiography (echo). Cross-sectional associations between echo markers of left ventricular structure and function and global cortical Aβ (≥1.2 standardized uptake value ratio were evaluated using multivariable logistic regression with interaction terms when appropriate. Results- Participants ranged in age from 67 to 88 years, were 57% female and 42% black. Per 1 cm increase in end-diastolic left ventricular diameter, the odds of elevated florbetapir standardized uptake value ratio doubled (odds ratio, 2.04 [95% CI, 1.10-3.77]), with similar findings when excluding mild cognitive impairment (odds ratio, 2.61 [95% CI, 1.22-5.59]). Conclusions- We have demonstrated a significant association between a marker of left ventricular structure and elevated florbetapir standardized uptake value ratio, identified using positron emission tomography. Ongoing prospective work will help determine if changes in cardiac structure and function either precede, or occur simultaneously with deposition of amyloid.

The prevalence of atrial fibrillation on 48-hour ambulatory electrocardiography in African Americans compared to Whites: The Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

A lower prevalence of atrial fibrillation (AF), but paradoxically higher burden of cardiovascular disease risk factors, has been observed among African Americans compared to Whites in studies of AF identified by mostly 12-lead electrocardiograms (ECGs) and clinically.

METHODS

We performed 48-hour ambulatory electrocardiography (aECG) in a biracial sample of 1,193 participants in the Atherosclerosis Risk in Communities (ARIC) (mean age = 78 years, 62% African Americans, 64% female). Atrial fibrillation was identified from aECG, study visit ECGs, and discharge codes from cohort hospitalizations. We used covariate-adjusted logistic regression to estimate prevalence odds ratios (ORs) for AF in African Americans versus Whites, with adjustment for sampling and nonresponse.

RESULTS

African Americans were more likely than Whites to have hypertension and diabetes but less likely to have coronary heart disease. The prevalence of AF detected by aECG or ARIC study ECG (adjusted for age and coronary heart disease) was lower in African Americans than Whites (2.7% vs 5.0%). White men had a higher (although not significant) AF prevalence of 7.8% compared to the other race and gender groups at 2.3%-2.8%. The adjusted OR for AF was 0.49 (0.24-0.99) comparing African Americans to Whites. Findings were similar when AF was defined to include prior AF hospitalizations (OR = 0.42, 0.25-0.72). There were no significant differences by race for asymptomatic or paroxysmal AF.

CONCLUSIONS

Atrial fibrillation was less prevalent in African American than white older adults, regardless of detection method. Although overall detection of new AF cases with aECG was low, future studies should consider longer-term monitoring to characterize AF by race.

Genome-Wide Association Study Identifies Loci for Liver Enzyme Concentrations in Mexican Americans: The GUARDIAN Consortium

OBJECTIVE

Populations of Mexican American ancestry are at an increased risk for nonalcoholic fatty liver disease. The objective of this study was to determine whether loci in known and novel genes were associated with variation in aspartate aminotransferase (AST) (n = 3,644), alanine aminotransferase (ALT) (n = 3,595), and gamma-glutamyl transferase (GGT) (n = 1,577) levels by conducting the first genome-wide association study (GWAS) of liver enzymes, which commonly measure liver function, in individuals of Mexican American ancestry.

METHODS

Levels of AST, ALT, and GGT were determined by enzymatic colorimetric assays. A multi-cohort GWAS of individuals of Mexican American ancestry was performed. Single-nucleotide polymorphisms (SNP) were tested for association with liver outcomes by multivariable linear regression using an additive genetic model. Association analyses were conducted separately in each cohort, followed by a nonparametric meta-analysis.

RESULTS

In the PNPLA3 gene, rs4823173 (P = 3.44 × 10^-10 ), rs2896019 (P = 7.29 × 10^-9 ), and rs2281135 (P = 8.73 × 10^-9 ) were significantly associated with AST levels. Although not genome-wide significant, these same SNPs were the top hits for ALT (P = 7.12 × 10^-8 , P = 1.98 × 10^-7 , and P = 1.81 × 10^-7 , respectively). The strong correlation (r²  = 1.0) for these SNPs indicated a single hit in the PNPLA3 gene. No genome-wide significant associations were found for GGT.

CONCLUSIONS

PNPLA3, a locus previously identified with ALT, AST, and nonalcoholic fatty liver disease in European and Japanese GWAS, is also associated with liver enzymes in populations of Mexican American ancestry.

A multi-ancestry genome-wide study incorporating gene-smoking interactions identifies multiple new loci for pulse pressure and mean arterial pressure

Elevated blood pressure (BP), a leading cause of global morbidity and mortality, is influenced by both genetic and lifestyle factors. Cigarette smoking is one such lifestyle factor. Across five ancestries, we performed a genome-wide gene-smoking interaction study of mean arterial pressure (MAP) and pulse pressure (PP) in 129 913 individuals in stage 1 and follow-up analysis in 480 178 additional individuals in stage 2. We report here 136 loci significantly associated with MAP and/or PP. Of these, 61 were previously published through main-effect analysis of BP traits, 37 were recently reported by us for systolic BP and/or diastolic BP through gene-smoking interaction analysis and 38 were newly identified (P < 5 × 10-8, false discovery rate < 0.05). We also identified nine new signals near known loci. Of the 136 loci, 8 showed significant interaction with smoking status. They include CSMD1 previously reported for insulin resistance and BP in the spontaneously hypertensive rats. Many of the 38 new loci show biologic plausibility for a role in BP regulation. SLC26A7 encodes a chloride/bicarbonate exchanger expressed in the renal outer medullary collecting duct. AVPR1A is widely expressed, including in vascular smooth muscle cells, kidney, myocardium and brain. FHAD1 is a long non-coding RNA overexpressed in heart failure. TMEM51 was associated with contractile function in cardiomyocytes. CASP9 plays a central role in cardiomyocyte apoptosis. Identified only in African ancestry were 30 novel loci. Our findings highlight the value of multi-ancestry investigations, particularly in studies of interaction with lifestyle factors, where genomic and lifestyle differences may contribute to novel findings.

Silent Myocardial Infarction and Long-Term Risk of Heart Failure: The ARIC Study

BACKGROUND

Although silent myocardial infarction (SMI) accounts for about one-half of the total number of myocardial infarctions (MIs), the risk of heart failure (HF) among patients with SMI is not well established.

OBJECTIVES

The purpose of this study was to examine the association of SMI and clinically manifested myocardial infarction (CMI) with HF, as compared with patients with no MI.

METHODS

This analysis included 9,243 participants from the ARIC (Atherosclerosis Risk In Communities) study who were free of cardiovascular disease at baseline (ARIC visit 1: 1987 to 1989). SMI was defined as electrocardiographic evidence of MI without CMI after the baseline until ARIC visit 4 (1996 to 1998). HF events were ascertained starting from ARIC visit 4 until 2010 in individuals free of HF before that visit.

RESULTS

Between ARIC visits 1 and 4, 305 SMIs and 331 CMIs occurred. After ARIC visit 4 and during a median follow-up of 13.0 years, 976 HF events occurred. The incidence rate of HF was higher in both CMI and SMI participants than in those without MI (incidence rates per 1,000 person-years were 30.4, 16.2, and 7.8, respectively; p < 0.001). In a model adjusted for demographics and HF risk factors, both SMI (hazard ratio [HR]: 1.35; 95% confidence interval [CI]: 1.02 to 1.78) and CMI (HR: 2.85; 95% CI: 2.31 to 3.51) were associated with increased risk of HF compared with no MI. These associations were consistent in subgroups of participants stratified by several HF risk predictors. However, the risk of HF associated with SMI was stronger in those younger than the median age (53 years) (HR: 1.66; 95% CI: 1.00 to 2.75 vs. HR: 1.19; 95% CI: 0.85 to 1.66, respectively; overall interaction p by MI type <0.001).

CONCLUSIONS

SMI is associated with an increased risk of HF. Future research is needed to examine the cost effectiveness of screening for SMI as part of HF risk assessment, and to identify preventive therapies to improve the risk of HF among patients with SMI.

Publisher Correction: Protein-altering variants associated with body mass index implicate pathways that control energy intake and expenditure in obesity

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Multiancestry Genome-Wide Association Study of Lipid Levels Incorporating Gene-Alcohol Interactions

A person's lipid profile is influenced by genetic variants and alcohol consumption, but the contribution of interactions between these exposures has not been studied. We therefore incorporated gene-alcohol interactions into a multiancestry genome-wide association study of levels of high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides. We included 45 studies in stage 1 (genome-wide discovery) and 66 studies in stage 2 (focused follow-up), for a total of 394,584 individuals from 5 ancestry groups. Analyses covered the period July 2014-November 2017. Genetic main effects and interaction effects were jointly assessed by means of a 2-degrees-of-freedom (df) test, and a 1-df test was used to assess the interaction effects alone. Variants at 495 loci were at least suggestively associated (P < 1 × 10-6) with lipid levels in stage 1 and were evaluated in stage 2, followed by combined analyses of stage 1 and stage 2. In the combined analysis of stages 1 and 2, a total of 147 independent loci were associated with lipid levels at P < 5 × 10-8 using 2-df tests, of which 18 were novel. No genome-wide-significant associations were found testing the interaction effect alone. The novel loci included several genes (proprotein convertase subtilisin/kexin type 5 (PCSK5), vascular endothelial growth factor B (VEGFB), and apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (APOBEC1) complementation factor (A1CF)) that have a putative role in lipid metabolism on the basis of existing evidence from cellular and experimental models.

Multi-ancestry genome-wide gene-smoking interaction study of 387,272 individuals identifies new loci associated with serum lipids

The concentrations of high- and low-density-lipoprotein cholesterol and triglycerides are influenced by smoking, but it is unknown whether genetic associations with lipids may be modified by smoking. We conducted a multi-ancestry genome-wide gene-smoking interaction study in 133,805 individuals with follow-up in an additional 253,467 individuals. Combined meta-analyses identified 13 new loci associated with lipids, some of which were detected only because association differed by smoking status. Additionally, we demonstrate the importance of including diverse populations, particularly in studies of interactions with lifestyle factors, where genomic and lifestyle differences by ancestry may contribute to novel findings.

Protein-coding variants implicate novel genes related to lipid homeostasis contributing to body-fat distribution

Body-fat distribution is a risk factor for adverse cardiovascular health consequences. We analyzed the association of body-fat distribution, assessed by waist-to-hip ratio adjusted for body mass index, with 228,985 predicted coding and splice site variants available on exome arrays in up to 344,369 individuals from five major ancestries (discovery) and 132,177 European-ancestry individuals (validation). We identified 15 common (minor allele frequency, MAF ≥5%) and nine low-frequency or rare (MAF <5%) coding novel variants. Pathway/gene set enrichment analyses identified lipid particle, adiponectin, abnormal white adipose tissue physiology and bone development and morphology as important contributors to fat distribution, while cross-trait associations highlight cardiometabolic traits. In functional follow-up analyses, specifically in Drosophila RNAi-knockdowns, we observed a significant increase in the total body triglyceride levels for two genes (DNAH10 and PLXND1). We implicate novel genes in fat distribution, stressing the importance of interrogating low-frequency and protein-coding variants.

Type 1 Diabetes Risk in African-Ancestry Participants and Utility of an Ancestry-Specific Genetic Risk Score

OBJECTIVE

Genetic risk scores (GRS) have been developed that differentiate individuals with type 1 diabetes from those with other forms of diabetes and are starting to be used for population screening; however, most studies were conducted in European-ancestry populations. This study identifies novel genetic variants associated with type 1 diabetes risk in African-ancestry participants and develops an African-specific GRS.

RESEARCH DESIGN AND METHODS

We generated single nucleotide polymorphism (SNP) data with the ImmunoChip on 1,021 African-ancestry participants with type 1 diabetes and 2,928 control participants. HLA class I and class II alleles were imputed using SNP2HLA. Logistic regression models were used to identify genome-wide significant (P < 5.0 × 10-8) SNPs associated with type 1 diabetes in the African-ancestry samples and validate SNPs associated with risk in known European-ancestry loci (P < 2.79 × 10-5).

RESULTS

African-specific (HLA-DQA1*03:01-HLA-DQB1*02:01) and known European-ancestry HLA haplotypes (HLA-DRB1*03:01-HLA-DQA1*05:01-HLA-DQB1*02:01, HLA-DRB1*04:01-HLA-DQA1*03:01-HLA-DQB1*03:02) were significantly associated with type 1 diabetes risk. Among European-ancestry defined non-HLA risk loci, six risk loci were significantly associated with type 1 diabetes in subjects of African ancestry. An African-specific GRS provided strong prediction of type 1 diabetes risk (area under the curve 0.871), performing significantly better than a European-based GRS and two polygenic risk scores in independent discovery and validation cohorts.

CONCLUSIONS

Genetic risk of type 1 diabetes includes ancestry-specific, disease-associated variants. The GRS developed here provides improved prediction of type 1 diabetes in African-ancestry subjects and a means to identify groups of individuals who would benefit from immune monitoring for early detection of islet autoimmunity.

The triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio as a predictor of insulin resistance, β-cell function, and diabetes in Hispanics and African Americans

OBJECTIVE

The TG/HDL-C ratio is used as a marker of insulin resistance (IR) in Caucasians; however, there is limited data in other ethnic groups. We hypothesized that the TG/HDL-C ratio is associated with IR in Hispanics and African Americans (AA).

RESEARCH DESIGN AND METHODS

Data from the Insulin Resistance Atherosclerosis Family Study was examined for associations between TG/HDL-C ratio and IR, β-cell function and incident diabetes in non-diabetic Hispanics (n = 872, 63% female) and AA (n = 371, 61% female). Insulin sensitivity index (S_I) and disposition index (DI) from frequently-sampled intravenous glucose tolerance tests were used as markers of IR and β-cell function respectively. Incident type 2 diabetes was determined by fasting glucose ≥ 126 mg/dl or initiation of anti-hyperglycemia agents over 5 year follow-up.

RESULTS

Higher TG/HDL-C ratio was associated with IR in Hispanic and AA men and women (P < 0.0002), as well as β-cell function in Hispanic women and AA men and women (P < 0.02). TG/HDL-C predicted incident type 2 diabetes in women (area under the curves 0.703 and 0.795 for Hispanics and AA respectively).

CONCLUSIONS

Similar to Caucasians, the TG/HDL-C ratio can be used to identify IR in Hispanics and AA, and may predict type 2 diabetes in women.

Differences in Cardiovascular Mortality Risk among African Americans in the Minnesota Heart Survey: 1985-2015 vs The Atherosclerosis Risk in Communities Study Cohort: 1987-2015

Geographic differences in cardiovascular disease (CVD) mortality among African Americans (AAs) are well-established, but not well-characterized. Using the Minnesota Heart Survey (MHS) and Atherosclerosis Risk in Communities (ARIC) Study, we aimed to assess whether CVD risk factors drive geographic disparities in CVD mortality among AAs. ARIC risk factors were measured between1987-1989 from a population-based sample of AAs, aged 45 to 64 years, living in Jackson, MS and Forsyth County, NC. Similar measures were made at MHS baseline, 1985, in AAs from Minneapolis-St. Paul, MN. CVD mortality was identified using ICD codes for underlying cause of death. We compared MHS and ARIC on CVD death rates using Poisson regression, risk factor prevalences, and hazard ratios using Cox regression. After CVD risk factor adjustment, AA men in MHS had 3.4 (95% CI: 2.1, 4.7) CVD deaths per 1000 person-years vs 9.9 (95% CI: 8.7, 11.1) in ARIC. AA women in MHS had 2.7 (95% CI: 1.8, 3.6) CVD deaths per 1000 person-years vs 6.7 (95% CI: 6.0, 7.4) in ARIC. A 2-fold higher CVD mortality rate remained in ARIC vs MHS after additional adjustment for education and income. ARIC had higher total cholesterol, hypertension, diabetes, and BMI, as well as less education and income than MHS. Risk factor hazard ratios of CVD death did not differ. The CVD death rate was lower in AAs in Minnesota (MHS) than AAs in the Southeast (ARIC). While our findings support maintaining low risk for CVD prevention, differences in CVD mortality reflect unidentified geographic variation.

Risk of diabetes associated with fatty acids in the de novo lipogenesis pathway is independent of insulin sensitivity and response: the Insulin Resistance Atherosclerosis Study (IRAS)

OBJECTIVE

To examine the associations of fatty acids in the de novo lipogenesis (DNL) pathway, specifically myristic acid (14:0), palmitic acid (16:0), cis-palmitoleic acid (c16:1 n-7), cis-myristoleic acid (c14:1n5), stearic acid (18:0) and cis-oleic acid (c18:1 n-9), with 5-year risk of type 2 diabetes. We hypothesized that DNL fatty acids are associated with risk of type 2 diabetes independent of insulin sensitivity.

RESEARCH DESIGN AND METHODS

We evaluated 719 (mean age 55.1±8.5 years, 44.2% men, 42.3% Caucasians) participants from the Insulin Resistance Atherosclerosis Study. Multivariable logistic regression models with and without adjustment of insulin sensitivity were used to assess prospective associations of DNL fatty acids with incident type 2 diabetes.

RESULTS

Type 2 diabetes incidence was 20.3% over 5 years. In multivariable regression models, palmitic, palmitoleic, myristic, myristoleic and oleic acids were associated with increased risk of type 2 diabetes (p<0.05). Palmitic acid had the strongest association (OR per standard unit of palmitic acid 1.46; 95% CI 1.23 to 1.76; p<0.001), which remained similar with addition of insulin sensitivity and acute insulin response (AIR) to the model (OR 1.36; 95% CI 1.09 to 1.70, p=0.01). Oleic and palmitoleic acids were also independently associated with incident type 2 diabetes. In multivariable models, ratios of fatty acids corresponding to stearoyl CoA desaturase-1 and Elovl6 enzymatic activity were significantly associated with risk of type 2 diabetes independent of insulin sensitivity and AIR.

CONCLUSIONS

We observed associations of DNL fatty acids with type 2 diabetes incidence independent of insulin sensitivity.

Fatty acid biomarkers of dairy fat consumption and incidence of type 2 diabetes: A pooled analysis of prospective cohort studies

BACKGROUND

We aimed to investigate prospective associations of circulating or adipose tissue odd-chain fatty acids 15:0 and 17:0 and trans-palmitoleic acid, t16:1n-7, as potential biomarkers of dairy fat intake, with incident type 2 diabetes (T2D).

METHODS AND FINDINGS

Sixteen prospective cohorts from 12 countries (7 from the United States, 7 from Europe, 1 from Australia, 1 from Taiwan) performed new harmonised individual-level analysis for the prospective associations according to a standardised plan. In total, 63,682 participants with a broad range of baseline ages and BMIs and 15,180 incident cases of T2D over the average of 9 years of follow-up were evaluated. Study-specific results were pooled using inverse-variance-weighted meta-analysis. Prespecified interactions by age, sex, BMI, and race/ethnicity were explored in each cohort and were meta-analysed. Potential heterogeneity by cohort-specific characteristics (regions, lipid compartments used for fatty acid assays) was assessed with metaregression. After adjustment for potential confounders, including measures of adiposity (BMI, waist circumference) and lipogenesis (levels of palmitate, triglycerides), higher levels of 15:0, 17:0, and t16:1n-7 were associated with lower incidence of T2D. In the most adjusted model, the hazard ratio (95% CI) for incident T2D per cohort-specific 10th to 90th percentile range of 15:0 was 0.80 (0.73-0.87); of 17:0, 0.65 (0.59-0.72); of t16:1n7, 0.82 (0.70-0.96); and of their sum, 0.71 (0.63-0.79). In exploratory analyses, similar associations for 15:0, 17:0, and the sum of all three fatty acids were present in both genders but stronger in women than in men (pinteraction < 0.001). Whereas studying associations with biomarkers has several advantages, as limitations, the biomarkers do not distinguish between different food sources of dairy fat (e.g., cheese, yogurt, milk), and residual confounding by unmeasured or imprecisely measured confounders may exist.

CONCLUSIONS

In a large meta-analysis that pooled the findings from 16 prospective cohort studies, higher levels of 15:0, 17:0, and t16:1n-7 were associated with a lower risk of T2D.

Association of Race and Ethnicity With Glycemic Control and Hemoglobin A1c Levels in Youth With Type 1 Diabetes

IMPORTANCE

Health disparities in the clinical presentation and outcomes among youth with type 1 diabetes exist. Long-term glycemic control patterns in racially/ethnically diverse youth are not well described.

OBJECTIVES

To model common trajectories of hemoglobin A1c (HbA1c) among youth with type 1 diabetes and test how trajectory group membership varies by race/ethnicity.

DESIGN SETTING AND PARTICIPANTS

Longitudinal cohort study conducted in 5 US locations. The analysis included data from 1313 youths (aged <20 years) newly diagnosed in 2002 through 2005 with type 1 diabetes in the SEARCH for Diabetes in Youth study (mean [SD] age at diabetes onset, 8.9 [4.2] years) who had 3 or more HbA1c study measures during 6.1 to 13.3 years of follow-up. Data were analyzed in 2017.

EXPOSURES

Self-reported race/ethnicity.

MAIN OUTCOMES AND MEASURES

Hemoglobin A1c trajectories identified through group-based trajectory modeling over a mean (SD) of 9.0 (1.4) years of diabetes duration. Multinomial models studied the association of race/ethnicity with HbA1c trajectory group membership, adjusting for demographic characteristics, clinical factors, and socioeconomic position.

RESULTS

The final study sample of 1313 patients was 49.3% female (647 patients) with mean (SD) age 9.7 (4.3) years and mean (SD) disease duration of 9.2 (6.3) months at baseline. The racial/ethnic composition was 77.0% non-Hispanic white (1011 patients), 10.7% Hispanic (140 patients), 9.8% non-Hispanic black (128 patients), and 2.6% other race/ethnicity (34 patients). Three HbA1c trajectories were identified: group 1, low baseline and mild increases (50.7% [666 patients]); group 2, moderate baseline and moderate increases (41.7% [548 patients]); and group 3, moderate baseline and major increases (7.5% [99 patients]). Group 3 was composed of 47.5% nonwhite youths (47 patients). Non-Hispanic black youth had 7.98 higher unadjusted odds (95% CI, 4.42-14.38) than non-Hispanic white youth of being in the highest HbA1c trajectory group relative to the lowest HbA1c trajectory group; the association remained significant after full adjustment (adjusted odds ratio of non-Hispanic black race in group 3 vs group 1, 4.54; 95% CI, 2.08-9.89). Hispanic youth had 3.29 higher unadjusted odds (95% CI, 1.78-6.08) than non-Hispanic white youth of being in the highest HbA1c trajectory group relative to the lowest HbA1c trajectory group; the association remained significant after adjustment (adjusted odds ratio of Hispanic ethnicity in group 3 vs group 1, 2.24; 95% CI, 1.02-4.92). In stratified analyses, the adjusted odds of nonwhite membership in the highest HbA1c trajectory remained significant among male patients and youth diagnosed at age 9 years or younger, but not female patients and youth who were older than 9 years when they were diagnosed (P for interaction = .04 [sex] and .02 [age at diagnosis]).

CONCLUSIONS AND RELEVANCE

There are racial/ethnic differences in long-term glycemic control among youth with type 1 diabetes, particularly among nonwhite male patients and nonwhite youth diagnosed earlier in life.

Genome-wide interaction with the insulin secretion locus MTNR1B reveals CMIP as a novel type 2 diabetes susceptibility gene in African Americans

Although type 2 diabetes (T2D) results from metabolic defects in insulin secretion and insulin sensitivity, most of the genetic risk loci identified to date relates to insulin secretion. We reported that T2D loci influencing insulin sensitivity may be identified through interactions with insulin secretion loci, thereby leading to T2D. Here, we hypothesize that joint testing of variant main effects and interaction effects with an insulin secretion locus increases power to identify genetic interactions leading to T2D. We tested this hypothesis with an intronic MTNR1B SNP, rs10830963, which is associated with acute insulin response to glucose, a dynamic measure of insulin secretion. rs10830963 was tested for interaction and joint (main + interaction) effects with genome-wide data in African Americans (2,452 cases and 3,772 controls) from five cohorts. Genome-wide genotype data (Affymetrix Human Genome 6.0 array) was imputed to a 1000 Genomes Project reference panel. T2D risk was modeled using logistic regression with rs10830963 dosage, age, sex, and principal component as predictors. Joint effects were captured using the Kraft two degrees of freedom test. Genome-wide significant (P < 5 × 10-8 ) interaction with MTNR1B and joint effects were detected for CMIP intronic SNP rs17197883 (Pinteraction  = 1.43 × 10-8 ; Pjoint  = 4.70 × 10-8 ). CMIP variants have been nominally associated with T2D, fasting glucose, and adiponectin in individuals of East Asian ancestry, with high-density lipoprotein, and with waist-to-hip ratio adjusted for body mass index in Europeans. These data support the hypothesis that additional genetic factors contributing to T2D risk, including insulin sensitivity loci, can be identified through interactions with insulin secretion loci.

Novel genetic associations for blood pressure identified via gene-alcohol interaction in up to 570K individuals across multiple ancestries

Heavy alcohol consumption is an established risk factor for hypertension; the mechanism by which alcohol consumption impact blood pressure (BP) regulation remains unknown. We hypothesized that a genome-wide association study accounting for gene-alcohol consumption interaction for BP might identify additional BP loci and contribute to the understanding of alcohol-related BP regulation. We conducted a large two-stage investigation incorporating joint testing of main genetic effects and single nucleotide variant (SNV)-alcohol consumption interactions. In Stage 1, genome-wide discovery meta-analyses in ≈131K individuals across several ancestry groups yielded 3,514 SNVs (245 loci) with suggestive evidence of association (P < 1.0 x 10-5). In Stage 2, these SNVs were tested for independent external replication in ≈440K individuals across multiple ancestries. We identified and replicated (at Bonferroni correction threshold) five novel BP loci (380 SNVs in 21 genes) and 49 previously reported BP loci (2,159 SNVs in 109 genes) in European ancestry, and in multi-ancestry meta-analyses (P < 5.0 x 10-8). For African ancestry samples, we detected 18 potentially novel BP loci (P < 5.0 x 10-8) in Stage 1 that warrant further replication. Additionally, correlated meta-analysis identified eight novel BP loci (11 genes). Several genes in these loci (e.g., PINX1, GATA4, BLK, FTO and GABBR2) have been previously reported to be associated with alcohol consumption. These findings provide insights into the role of alcohol consumption in the genetic architecture of hypertension.

Short-Term Global Cardiovascular Disease Risk Prediction in Older Adults

BACKGROUND

Current prevention guidelines recommend using the Pooled Cohort Equation (PCE) for 10-year atherosclerotic cardiovascular disease (CVD) risk assessment. However, the PCE has serious limitations in older adults: it excludes heart failure (HF) hospitalization, estimates 10-year risk, which may not be the most relevant time frame, and is not indicated for individuals age >79 years.

OBJECTIVES

This study sought to determine whether adding biomarkers to PCE variables improves global CVD (coronary heart disease, stroke, and HF) risk prediction in older adults over a shorter time period.

METHODS

Atherosclerosis Risk in Communities study participants without prevalent CVD including HF (n = 4,760; age 75.4 ± 5.1 years) were followed for incident global CVD events. Adding N-terminal pro-B-type natriuretic peptide, high-sensitivity cardiac troponin T, and high-sensitivity C-reactive protein to the PCE and a "lab model" with the biomarkers, age, race, and gender were assessed for prediction improvement. Area under the receiver operating characteristic curve (AUC) and net reclassification index (NRI) were calculated.

RESULTS

Over median follow-up of ∼4 years, incident HF was the leading CVD event (n = 193 vs. 118 coronary heart disease and 81 stroke events). Compared to the PCE, each biomarker improved risk prediction. The largest improvement in risk prediction metrics was with the addition of all 3 biomarkers (ΔAUC 0.103; continuous NRI 0.484). The lab model also performed better than the PCE model (ΔAUC 0.091, continuous NRI 0.355).

CONCLUSIONS

Adding biomarkers to the PCE or a simpler "lab model" improves short-term global CVD risk prediction and may be useful to inform short-term preventive strategies in older adults.

Metabolomics Identifies Distinctive Metabolite Signatures for Measures of Glucose Homeostasis: The Insulin Resistance Atherosclerosis Family Study (IRAS-FS)

CONTEXT

Metabolomics provides a biochemical fingerprint that, when coupled with clinical phenotypes, can provide insight into physiological processes.

OBJECTIVE

Survey metabolites associated with dynamic and basal measures of glucose homeostasis.

DESIGN

Analysis of 733 plasma metabolites from the Insulin Resistance Atherosclerosis Family Study.

SETTING

Community based.

PARTICIPANTS

One thousand one hundred eleven Mexican Americans.

MAIN OUTCOME

Dynamic measures were obtained from the frequently sampled intravenous glucose tolerance test and included insulin sensitivity and acute insulin response to glucose. Basal measures included homeostatic model assessment of insulin resistance and β-cell function.

RESULTS

Insulin sensitivity was associated with 99 metabolites (P < 6.82 × 10-5) explaining 28% of the variance (R2adj) beyond 28% by body mass index. Beyond branched chain amino acids (BCAAs; P = 1.85 × 10-18 to 1.70 × 10-5, R2adj = 8.1%) and phospholipids (P = 3.51 × 10-17 to 3.00 × 10-5, R2adj = 14%), novel signatures of long-chain fatty acids (LCFAs; P = 4.49 × 10-23 to 4.14 × 10-7, R2adj = 11%) were observed. Conditional analysis suggested that BCAA and LCFA signatures were independent. LCFAs were not associated with homeostatic model assessment of insulin resistance (P > 0.024). Acute insulin response to glucose was associated with six metabolites; glucose had the strongest association (P = 5.68 × 10-16). Homeostatic model assessment of β-cell function had significant signatures from the urea cycle (P = 9.64 × 10-14 to 7.27 × 10-6, R2adj = 11%). Novel associations of polyunsaturated fatty acids (P = 2.58 × 10-13 to 6.70 × 10-5, R2adj = 10%) and LCFAs (P = 9.06 × 10-15 to 3.93 × 10-7, R2adj = 10%) were observed with glucose effectiveness. Assessment of the hyperbolic relationship between insulin sensitivity and secretion through the disposition index revealed a distinctive signature of polyunsaturated fatty acids (P = 1.55 × 10-12 to 5.81 × 10-6; R2adj = 3.8%) beyond that of its component measures.

CONCLUSIONS

Metabolomics reveals distinct signatures that differentiate dynamic and basal measures of glucose homeostasis and further identifies new metabolite classes associated with dynamic measures, providing expanded insight into the metabolic basis of insulin resistance.

Publisher Correction: Protein-altering variants associated with body mass index implicate pathways that control energy intake and expenditure in obesity

In the version of this article originally published, one of the two authors with the name Wei Zhao was omitted from the author list and the affiliations for both authors were assigned to the single Wei Zhao in the author list. In addition, the ORCID for Wei Zhao (Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA) was incorrectly assigned to author Wei Zhou. The errors have been corrected in the HTML and PDF versions of the article.

Publisher Correction: Protein-altering variants associated with body mass index implicate pathways that control energy intake and expenditure in obesity

In the published version of this paper, the name of author Emanuele Di Angelantonio was misspelled. This error has now been corrected in the HTML and PDF versions of the article.

Impact of Intensive Lifestyle Intervention on Disability-Free Life Expectancy: The Look AHEAD Study

OBJECTIVE

The impact of weight loss intervention on disability-free life expectancy in adults with diabetes is unknown. We examined the impact of a long-term weight loss intervention on years spent with and without physical disability.

RESEARCH DESIGN AND METHODS

Overweight or obese adults with type 2 diabetes age 45-76 years (n = 5,145) were randomly assigned to a 10-year intensive lifestyle intervention (ILI) or diabetes support and education (DSE). Physical function was assessed annually for 12 years using the 36-Item Short Form Health Survey. Annual incidence of physical disability, mortality, and disability remission were incorporated into a Markov model to quantify years of life spent active and physically disabled.

RESULTS

Physical disability incidence was lower in the ILI group (6.0% per year) than in the DSE group (6.8% per year) (incidence rate ratio 0.88 [95% CI 0.81-0.96]), whereas rates of disability remission and mortality did not differ between groups. ILI participants had a significant delay in moderate or severe disability onset and an increase in number of nondisabled years (P < 0.05) compared with DSE participants. For a 60-year-old, this effect translates to 0.9 more disability-free years (12.0 years [95% CI 11.5-12.4] vs. 11.1 years [95% CI 10.6-11.7]) but no difference in total years of life. In stratified analyses, ILI increased disability-free years of life in women and participants without cardiovascular disease (CVD) but not in men or participants with CVD.

CONCLUSIONS

Long-term lifestyle interventions among overweight or obese adults with type 2 diabetes may reduce long-term disability, leading to an effect on disability-free life expectancy but not on total life expectancy.

Serum metabolomic profile of incident diabetes

AIMS/HYPOTHESIS

Metabolomic profiling offers the potential to reveal metabolic pathways relevant to the pathophysiology of diabetes and improve diabetes risk prediction.

METHODS

We prospectively analysed known metabolites using an untargeted approach in serum specimens from baseline (1987-1989) and incident diabetes through to 31 December 2015 in a subset of 2939 Atherosclerosis Risk in Communities (ARIC) study participants with metabolomics data and without prevalent diabetes.

RESULTS

Among the 245 named compounds identified, seven metabolites were significantly associated with incident diabetes after Bonferroni correction and covariate adjustment; these included a food additive (erythritol) and compounds involved in amino acid metabolism [isoleucine, leucine, valine, asparagine, 3-(4-hydoxyphenyl)lactate] and glucose metabolism (trehalose). Higher levels of metabolites were associated with increased risk of incident diabetes (HR per 1 SD increase in isoleucine 2.96, 95% CI 2.02, 4.35, p = 3.18 × 10^-8; HR per 1 SD increase in trehalose 1.16, 95% CI 1.09, 1.25, p = 1.87 × 10^-5), with the exception of asparagine, which was associated with a lower risk of diabetes (HR per 1 SD increase in asparagine 0.78, 95% CI 0.71, 0.85, p = 4.19 × 10^-8). The seven metabolites modestly improved prediction of incident diabetes beyond fasting glucose and established risk factors (C statistics 0.744 vs 0.735, p = 0.001 for the difference in C statistics).

CONCLUSIONS/INTERPRETATION

Branched chain amino acids may play a role in diabetes development. Our study is the first to report asparagine as a protective biomarker of diabetes risk. The serum metabolome reflects known and novel metabolic disturbances that improve prediction of diabetes.

Arterial stiffness and dementia pathology: Atherosclerosis Risk in Communities (ARIC)-PET Study

OBJECTIVE

Arterial stiffness has been associated with evidence of cerebral small vessel disease (cSVD) and fibrillar β-amyloid (Aβ) deposition in the brain. These complex relationships have not been examined in racially and cognitively diverse cohorts.

METHODS

The Atherosclerosis Risk in Communities (ARIC)-Neurocognitive Study collected detailed cognitive testing for adjudication of dementia and mild cognitive impairment (MCI), brain MRI, and arterial stiffness by pulse wave velocity (PWV, carotid-femoral [cfPWV] and heart-carotid [hcPWV]). The ARIC-PET ancillary study added Aβ imaging using florbetapir ([18F]-AV-45) to obtain standardized uptake volume ratios and defined global Aβ-positivity as standardized uptake volume ratio >1.2. One-SD increase in PWV was related to brain volume, MRI-defined cSVD (e.g., cerebral microbleeds and white matter hyperintensity), and cortical Aβ deposition adjusted for age, body mass index, sex, race, and APOE ε4 status. We examined the cross-sectional relationships including interactions by race, APOE ε4 status, and cognition.

RESULTS

Among the 320 ARIC-PET participants (76 [5] years, 45% black, 27% MCI), greater central stiffness (hcPWV) was associated with greater Aβ deposition (odds ratio [OR] = 1.31, 95% confidence interval [CI] 1.01-1.71). Greater central stiffness (cfPWV) was significantly associated with having lower brain volumes in Alzheimer disease-susceptible regions (in mm3, β = -1.5 [0.7 SD], p = 0.03) and high white matter hyperintensity burden (OR = 1.6, 95% CI 1.2-2.1). Furthermore, cfPWV was associated with a higher odds of concomitant high white matter hyperintensity and Aβ-positive scans (OR = 1.4, 95% CI 1.1-2.1). These associations were strongest among individuals with MCI and did not differ by race or APOE ε4 status.

CONCLUSIONS

Arterial stiffness, measured by PWV, is an emerging risk factor for dementia through its repeated relationships with cognition, cSVD, and Aβ deposition.

Transethnic Evaluation Identifies Low-Frequency Loci Associated With 25-Hydroxyvitamin D Concentrations

Context

Vitamin D inadequacy is common in the adult population of the United States. Although the genetic determinants underlying vitamin D inadequacy have been studied in people of European ancestry, less is known about populations with Hispanic or African ancestry.

Objective

The Trans-Ethnic Evaluation of Vitamin D (TRANSCEN-D) genomewide association study (GWAS) consortium was assembled to replicate genetic associations with 25-hydroxyvitamin D [25(OH)D] concentrations from the Study of Underlying Genetic Determinants of Vitamin D and Highly Related Traits (SUNLIGHT) meta-analyses of European ancestry and to identify genetic variants related to vitamin D concentrations in African and Hispanic ancestries.

Design

Ancestry-specific (Hispanic and African) and transethnic (Hispanic, African, and European) meta-analyses were performed with Meta-Analysis Helper software (METAL).

Patients or Other Participants

In total, 8541 African American and 3485 Hispanic American (from North America) participants from 12 cohorts and 16,124 European participants from SUNLIGHT were included in the study.

Main Outcome Measures

Blood concentrations of 25(OH)D were measured for all participants.

Results

Ancestry-specific analyses in African and Hispanic Americans replicated single nucleotide polymorphisms (SNPs) in GC (2 and 4 SNPs, respectively). An SNP (rs79666294) near the KIF4B gene was identified in the African American cohort. Transethnic evaluation replicated GC and DHCR7 region SNPs. Additionally, the transethnic analyses revealed SNPs rs719700 and rs1410656 near the ANO6/ARID2 and HTR2A genes, respectively.

Conclusions

Ancestry-specific and transethnic GWASs of 25(OH)D confirmed findings in GC and DHCR7 for African and Hispanic American samples and revealed findings near KIF4B, ANO6/ARID2, and HTR2A. The biological mechanisms that link these regions with 25(OH)D metabolism warrant further investigation.

A Large-Scale Multi-ancestry Genome-wide Study Accounting for Smoking Behavior Identifies Multiple Significant Loci for Blood Pressure

Genome-wide association analysis advanced understanding of blood pressure (BP), a major risk factor for vascular conditions such as coronary heart disease and stroke. Accounting for smoking behavior may help identify BP loci and extend our knowledge of its genetic architecture. We performed genome-wide association meta-analyses of systolic and diastolic BP incorporating gene-smoking interactions in 610,091 individuals. Stage 1 analysis examined ∼18.8 million SNPs and small insertion/deletion variants in 129,913 individuals from four ancestries (European, African, Asian, and Hispanic) with follow-up analysis of promising variants in 480,178 additional individuals from five ancestries. We identified 15 loci that were genome-wide significant (p < 5 × 10-8) in stage 1 and formally replicated in stage 2. A combined stage 1 and 2 meta-analysis identified 66 additional genome-wide significant loci (13, 35, and 18 loci in European, African, and trans-ancestry, respectively). A total of 56 known BP loci were also identified by our results (p < 5 × 10-8). Of the newly identified loci, ten showed significant interaction with smoking status, but none of them were replicated in stage 2. Several loci were identified in African ancestry, highlighting the importance of genetic studies in diverse populations. The identified loci show strong evidence for regulatory features and support shared pathophysiology with cardiometabolic and addiction traits. They also highlight a role in BP regulation for biological candidates such as modulators of vascular structure and function (CDKN1B, BCAR1-CFDP1, PXDN, EEA1), ciliopathies (SDCCAG8, RPGRIP1L), telomere maintenance (TNKS, PINX1, AKTIP), and central dopaminergic signaling (MSRA, EBF2).

Abstract 151: Intracranial Atherosclerotic Disease and Brain Amyloid Deposition: The ARIC Study

Background: Increasing evidence points to intracranial atherosclerosis as a risk factor not only for stroke but also for dementia, but whether it is linked to Alzheimer’s disease-specific pathology itself is less understood. In the community-based Atherosclerosis Risk in Communities (ARIC) study, we evaluated the cross-sectional association between intracranial atherosclerosis and cerebral amyloid deposition, in nondemented participants.

Methods: In 2011-2014, a subset of participants from the ARIC Neurocognitive Study underwent both a brain MRI, including high-resolution vessel wall imaging, and florbetapir PET, as a marker of amyloid deposition. We analyzed the association between elevated amyloid (defined as a global cortical florbetapir standardized uptake value ratio (SUVR)>1.2) and intracranial arterial plaque presence, frequency, and extent of stenosis, with adjustment for demographic and vascular risk factors. We tested effect modification by APOE ε4 genotype.

Results: In 300 participants (mean age of 76y, 44% African-American, 56% female, 31% carriers of at least one APOE ε4 allele), intracranial plaque was found in 105 (35%) participants. Mean SUVR was higher in individuals with vs without plaque (1.34 ± 0.29 vs 1.27 ± 0.23, p=0.03). In adjusted models, plaque presence was not associated significantly with elevated SUVR in the total sample, nor was number of plaques. Associations between plaque presence and extent were generally stronger in APOE ε4 carriers than noncarriers (p<0.05 for interaction for some plaque features; see Table).

Conclusions: Although intracranial arterial plaque or stenosis was not definitively associated with brain amyloid in this sample of nondemented older adults, associations with brain amyloid appeared stronger in carriers of an APOE ε4 allele, consistent with studies demonstrating a similar relationship as that seen with other more traditionally measured vascular risk factors.

FGF23 Concentration and APOL1 Genotype Are Novel Predictors of Mortality in African Americans With Type 2 Diabetes

OBJECTIVE

Cardiovascular and renal complications contribute to higher mortality in patients with diabetes. We assessed novel and conventional predictors of mortality in African American-Diabetes Heart Study (AA-DHS) participants.

RESEARCH DESIGN AND METHODS

Associations between mortality and subclinical atherosclerosis, urine albumin-to-creatinine ratio (UACR), estimated glomerular filtration rate (eGFR), plasma fibroblast growth factor 23 (FGF23) concentration, African ancestry proportion, and apolipoprotein L1 genotypes (APOL1) were assessed in 513 African Americans with type 2 diabetes; analyses were performed using Cox proportional hazards models.

RESULTS

At baseline, participants were 55.6% female with median (25th, 75th percentile) age 55 years (49.0, 62.0), diabetes duration 8 years (5.0, 13.0), glycosylated hemoglobin 60.7 mmol/mol (48.6, 76.0), eGFR 91.3 mL/min/1.73 m² (76.4, 111.3), UACR 12.5 mg/mmol (4.2, 51.2), and coronary artery calcium 28.5 mg Ca²⁺ (1.0, 348.6); 11.5% had two APOL1 renal-risk variants. After 6.6-year follow-up (5.8, 7.5), 54 deaths were recorded. Higher levels of coronary artery calcified plaque, carotid artery calcified plaque, albuminuria, and FGF23 were associated with higher mortality after adjustment for age, sex, and African ancestry proportion. A penalized Cox regression that included all covariates and predictors associated with mortality identified male sex (hazard ratio [HR] 4.17 [95% CI 1.96-9.09]), higher FGF23 (HR 2.10 [95% CI 1.59-2.78]), and absence of APOL1 renal-risk genotypes (HR 0.07 [95% CI 0.01-0.69]) as the strongest predictors of mortality.

CONCLUSIONS

Accounting for conventional risk factors, higher FGF23 concentrations and APOL1 non-renal-risk genotypes associated with higher mortality in African Americans with diabetes. These data add to growing evidence supporting FGF23 association with mortality; mechanisms whereby these novel predictors impact survival remain to be determined.

Genome-Wide Study of Subcutaneous and Visceral Adipose Tissue Reveals Novel Sex-Specific Adiposity Loci in Mexican Americans

OBJECTIVE

This study aimed to explore the genetic mechanisms of regional fat deposition, which is a strong risk factor for metabolic diseases beyond total adiposity.

METHODS

A genome-wide association study of 7,757,139 single-nucleotide polymorphisms (SNPs) in 983 Mexican Americans (n_male  = 403; n_female  = 580) from the Insulin Resistance Atherosclerosis Family Study was performed. Association analyses were performed with and without sex stratification for subcutaneous adipose tissue, visceral adipose tissue (VAT), and visceral-subcutaneous ratio (VSR) obtained from computed tomography.

RESULTS

The strongest signal identified was SNP rs2185405 (minor allele frequencies [MAF] = 40%; P_VAT = 1.98 × 10^-8 ) with VAT. It is an intronic variant of the GLIS family zinc finger 3 gene (GLIS3). In addition, SNP rs12657394 (MAF = 19%) was associated with VAT in males (P_male = 2.39×10^-8 ; P_female = 2.5 × 10^-3 ). It is located intronically in the serum response factor binding protein 1 gene (SRFBP1). On average, male carriers of the variant had 24.6 cm² increased VAT compared with noncarriers. Subsequently, genome-wide SNP-sex interaction analysis was performed. SNP rs10913233 (MAF = 14%; P_int = 3.07 × 10^-8 ) in PAPPA2 and rs10923724 (MAF = 38%; P_int = 2.89 × 10^-8 ) upstream of TBX15 were strongly associated with the interaction effect for VSR.

CONCLUSIONS

Six loci were identified with genome-wide significant associations with fat deposition and interactive effects. These results provided genetic evidence for a differential basis of fat deposition between genders.

Protein-altering variants associated with body mass index implicate pathways that control energy intake and expenditure in obesity

Genome-wide association studies (GWAS) have identified >250 loci for body mass index (BMI), implicating pathways related to neuronal biology. Most GWAS loci represent clusters of common, noncoding variants from which pinpointing causal genes remains challenging. Here we combined data from 718,734 individuals to discover rare and low-frequency (minor allele frequency (MAF) < 5%) coding variants associated with BMI. We identified 14 coding variants in 13 genes, of which 8 variants were in genes (ZBTB7B, ACHE, RAPGEF3, RAB21, ZFHX3, ENTPD6, ZFR2 and ZNF169) newly implicated in human obesity, 2 variants were in genes (MC4R and KSR2) previously observed to be mutated in extreme obesity and 2 variants were in GIPR. The effect sizes of rare variants are ~10 times larger than those of common variants, with the largest effect observed in carriers of an MC4R mutation introducing a stop codon (p.Tyr35Ter, MAF = 0.01%), who weighed ~7 kg more than non-carriers. Pathway analyses based on the variants associated with BMI confirm enrichment of neuronal genes and provide new evidence for adipocyte and energy expenditure biology, widening the potential of genetically supported therapeutic targets in obesity.

Diabetes-related factors and abdominal aortic aneurysm events: the Atherosclerotic Risk in Communities Study

PURPOSE

To test the hypothesis that diabetes-related factors (metabolic syndrome [MetS], glucose, insulin, and leptin) are inversely associated with abdominal aortic aneurysm (AAA) risk.

METHODS

We followed 13,736 participants, aged 45-64 years, without prior AAA surgery at baseline (1987-1989), for AAA occurrence through 2011. Hazard ratios (HRs) and their 95% confidence intervals (CIs) of AAA were calculated using Cox regression.

RESULTS

During 275,054 person-years of follow-up, we identified 518 AAA events. Fasting serum glucose was associated inversely with AAA risk (HR [95% CI] per one unit increment in log₂(glucose), 0.54 [0.36-0.80]), but fasting insulin was not associated with AAA. Plasma leptin was also associated inversely with AAA occurrence (HR [95% CI] per one unit increment in log₂(leptin), 0.83 [0.71-0.98]). Compared with individuals without MetS, those with MetS had increased risk of AAA (HR [95% CI], 1.24 [1.04-1.48]). Among individuals with or without diabetes, the HRs increased monotonically with a greater number of non-glucose MetS components.

CONCLUSIONS

Diabetes, fasting glucose, and plasma leptin were inversely associated with risk of AAA. In contrast, the MetS was associated with increased risk of AAA, due to the influence of the non-glucose MetS components.

Genome-wide association study of coronary artery calcified atherosclerotic plaque in African Americans with type 2 diabetes

Background

Coronary artery calcified atherosclerotic plaque (CAC) predicts cardiovascular disease (CVD). Despite exposure to more severe conventional CVD risk factors, African Americans (AAs) are less likely to develop CAC, and when they do, have markedly lower levels than European Americans. Genetic factors likely contribute to the observed ethnic differences. To identify genes associated with CAC in AAs with type 2 diabetes (T2D), a genome-wide association study (GWAS) was performed using the Illumina 5 M chip in 691 African American-Diabetes Heart Study participants (AA-DHS), with replication in 205 Jackson Heart Study (JHS) participants with T2D. Genetic association tests were performed on the genotyped and 1000 Genomes-imputed markers separately for each study, and combined in a meta-analysis.

Results

Single nucleotide polymorphisms (SNPs), rs11353135 (2q22.1), rs16879003 (6p22.3), rs5014012, rs58071836 and rs10244825 (all on chromosome 7), rs10918777 (9q31.2), rs13331874 (16p13.3) and rs4459623 (18q12.1) were associated with presence and/or quantity of CAC in the AA-DHS and JHS, with meta-analysis p-values ≤8.0 × 10⁻⁷. The strongest result in AA-DHS alone was rs6491315 in the 13q32.1 region (parameter estimate (SE) = −1.14 (0.20); p-value = 9.1 × 10⁻⁹). This GWAS peak replicated a previously reported AA-DHS CAC admixture signal (rs7492028, LOD score 2.8).

Conclusions

Genetic association between SNPs on chromosomes 2, 6, 7, 9, 16 and 18 and CAC were detected in AAs with T2D from AA-DHS and replicated in the JHS. These data support a role for genetic variation on these chromosomes as contributors to CAC in AAs with T2D, as well as to variation in CAC between populations of African and European ancestry.

Electronic supplementary material

The online version of this article (10.1186/s12863-017-0572-9) contains supplementary material, which is available to authorized users.

From Neighborhood to Genome: Three Decades of Nutrition-Related Research from the Atherosclerosis Risk in Communities Study

For 30 years, the Atherosclerosis Risk in Communities (ARIC) cohort study has examined the etiology and progression of atherosclerosis and atherosclerotic diseases.1 This research has evaluated variation in cardiovascular disease (CVD) risk in relation to age, race, gender, location and lifestyle factors, including diet. In this commentary, we describe ARIC research that illustrates an expanded view of the relationship between diet and health and suggest ways that future cohort studies may influence the direction of nutrition and dietetics practice.

Genetic architecture of lipid traits in the Hispanic community health study/study of Latinos

BACKGROUND

Despite ethnic disparities in lipid profiles, there are few genome-wide association studies investigating genetic variation of lipids in non-European ancestry populations. In this study, we present findings from genetic association analyses for total cholesterol, low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), and triglycerides in a large Hispanic/Latino cohort in the U.S., the Hispanic Community Health Study / Study of Latinos (HCHS/SOL).

METHODS

We estimated a heritability of approximately 20% for each lipid trait, similar to previous estimates in Europeans. To search for novel lipid loci, we performed conditional association analysis in which the statistical model was adjusted for previously reported SNPs associated with any of the four lipid traits. SNPs that remained genome-wide significant (P < 5 × 10-8) after conditioning on known loci were evaluated for replication.

RESULTS

We identified eight potentially novel lipid signals with minor allele frequencies <1%, none of which replicated. We tested previously reported SNP-trait associations for generalization to Hispanics/Latinos via a statistical framework. The generalization analysis revealed that approximately 50% of previously established lipid variants generalize to HCHS/SOL based on directional FDR r-value < 0.05. Some failures to generalize were due to lack of power.

CONCLUSIONS

These results demonstrate that many loci associated with lipid levels are shared across populations.

Individual serum saturated fatty acids and markers of chronic subclinical inflammation: the Insulin Resistance Atherosclerosis Study

Recent evidence has documented distinct effects of individual saturated FAs (SFAs) on cardiometabolic outcomes, with potential protective effects from odd- and very long-chain SFAs (VLSFAs). Cross-sectional and prospective associations of individual serum SFAs (12:0, 14:0, 15:0, 16:0, 18:0, 20:0, 22:0, and total SFA) with proinflammatory biomarkers and adiponectin were investigated in 555 adults from the IRAS. Principal component analysis (PCA) of proinflammatory markers yielded three clusters: principal component (PC) 1: fibrinogen, white cell count, C-reactive protein; PC 2: plasminogen activator inhibitor-1 (PAI-1), TNF-α, IL-18; PC 3: IL-6 and IL-8. Cross-sectional analyses on proinflammatory PCs and adiponectin, and prospective analyses on 5 year PAI-1 and fibrinogen concentrations were conducted with multiple regression. Total SFA and 16:0 were positively associated with PC 1 and PC 2, and negatively associated with adiponectin. The 14:0 was positively associated with PC 1 and negatively associated with adiponectin. In contrast, 15:0, 20:0, and 22:0 were negatively associated with PC 2, and 20:0 and 22:0 were positively associated with adiponectin. The 18:0 was negatively associated with PC 3. Prospectively, 15:0, 18:0, 20:0, and 22:0 were negatively associated with 5 year PAI-1 concentrations. The results demonstrate that individual SFAs have distinct roles in subclinical inflammation, highlighting the unique metabolic impacts of individual SFAs.

Cardiovascular Dysfunction and Frailty Among Older Adults in the Community: The ARIC Study

Background

The contribution of cardiovascular dysfunction to frailty in older adults is uncertain. This study aimed to define the relationship between frailty and cardiovascular structure and function, and determine whether these associations are independent of coexisting abnormalities in other organ systems.

Methods

We studied 3,991 older adults (mean age 75.6±5.0 years; 59% female) from the Atherosclerosis Risk in Communities (ARIC) Study in whom the following six organ systems were uniformly assessed: cardiac (by echocardiography), vascular (by ankle-brachial-index and pulse-wave-velocity), pulmonary (by spirometry), renal (by estimated glomerular filtration rate), hematologic (by hemoglobin), and adipose (by body mass index and bioimpedance). Frailty was defined by the presence of ≥3 of the following: low strength, low energy, slowed motor performance, low physical activity, or unintentional weight loss.

Results

Two hundred eleven (5.3%) participants were frail. In multivariable analyses adjusted for demographics, diabetes, hypertension, and measures of other organ system function, frailty was independently and additively associated with left ventricular hypertrophy (odds ratio [OR] = 1.72; 95% confidence interval [CI] = 1.30-2.40), reduced global longitudinal strain (reflecting systolic function; OR = 1.68; 95% CI = 1.16-2.44), and greater left atrial volume index (reflecting diastolic function; OR = 1.60; 95% CI = 1.13-2.27), which together demonstrated the greatest association with frailty (OR = 2.10; 95% CI = 1.57-2.82) of the systems studied. Lower magnitude associations were observed for vascular and pulmonary abnormalities, anemia, and impaired renal function. Cardiovascular abnormalities remained associated with frailty after excluding participants with prevalent cardiovascular disease.

Conclusions

Abnormalities of cardiac structure and function are independently associated with frailty, and together show the greatest association with frailty among the organ systems studied.

A Genome-Wide Association Study of IVGTT-Based Measures of First-Phase Insulin Secretion Refines the Underlying Physiology of Type 2 Diabetes Variants

Understanding the physiological mechanisms by which common variants predispose to type 2 diabetes requires large studies with detailed measures of insulin secretion and sensitivity. Here we performed the largest genome-wide association study of first-phase insulin secretion, as measured by intravenous glucose tolerance tests, using up to 5,567 individuals without diabetes from 10 studies. We aimed to refine the mechanisms of 178 known associations between common variants and glycemic traits and identify new loci. Thirty type 2 diabetes or fasting glucose-raising alleles were associated with a measure of first-phase insulin secretion at P < 0.05 and provided new evidence, or the strongest evidence yet, that insulin secretion, intrinsic to the islet cells, is a key mechanism underlying the associations at the HNF1A, IGF2BP2, KCNQ1, HNF1B, VPS13C/C2CD4A, FAF1, PTPRD, AP3S2, KCNK16, MAEA, LPP, WFS1, and TMPRSS6 loci. The fasting glucose-raising allele near PDX1, a known key insulin transcription factor, was strongly associated with lower first-phase insulin secretion but has no evidence for an effect on type 2 diabetes risk. The diabetes risk allele at TCF7L2 was associated with a stronger effect on peak insulin response than on C-peptide-based insulin secretion rate, suggesting a possible additional role in hepatic insulin clearance or insulin processing. In summary, our study provides further insight into the mechanisms by which common genetic variation influences type 2 diabetes risk and glycemic traits.

Association of Directly Measured Plasma Free 25(OH)D With Insulin Sensitivity and Secretion: The IRAS Family Study

OBJECTIVES

We aimed to compare the associations of directly measured plasma free 25-hydroxyvitamin D [25(OH)D] and total 25(OH)D concentrations with insulin sensitivity (SI) and β-cell function in nondiabetic Hispanics and African Americans. We hypothesized that directly measured free 25(OH)D would be more strongly associated with these measures of glucose homeostasis and that associations would differ by race.

DESIGN

We studied 1189 nondiabetic participants in the Insulin Resistance Atherosclerosis Study Family Study using data from baseline examinations from 2000 to 2002. SI, acute insulin response, and disposition index (DI) were determined from frequently sampled intravenous glucose tolerance tests. Plasma free and total 25(OH)D concentrations were measured by enzyme-linked immunosorbent assay and radioimmunoassay, respectively.

RESULTS

The median concentrations of plasma free 25(OH)D were 3.46 pg/mL for Hispanics and 2.17 pg/mL for African Americans (P < 0.0001), whereas the median concentrations of plasma total 25(OH)D were 16 ng/mL for Hispanics and 10 ng/mL for African Americans (P < 0.0001). Plasma free and total 25(OH)D were both positively associated with SI and DI in generalized estimating equations adjusted for demographic and lifestyle factors. After further adjustment with body mass index, the associations were no longer statistically significant, except for a significant association between plasma free 25(OH)D and SI. There was no effect modification by ethnicity on any of the exposure-outcome associations.

CONCLUSIONS

Our data showed that plasma free 25(OH)D had a slightly stronger association with SI compared with plasma total 25(OH)D, although the difference was modest and there were no marked differences in the associations between Hispanics and African Americans.

Diabetes status modifies the association between carotid intima-media thickness and incident heart failure: The Atherosclerosis Risk in Communities study

AIMS

Increasing carotid intima-media thickness (CIMT) is associated with incident heart failure (HF). We investigated whether this association differs by diabetes status.

METHODS

We characterized 13,590 Atherosclerosis Risk in Communities Study participants free of baseline HF into normal fasting glucose (NFG, glucose <100mg/dl), impaired fasting glucose (IFG, glucose 100-125mg/dl), and type 2 diabetes (T2D, glucose ≥126mg/dl, self-report, or use of diabetes drugs). CIMT was assessed by B-mode ultrasound. Incident HF was defined using ICD-9 or 10 codes from hospitalizations and death certificates. Cox regression was used to estimate hazard ratios (HR) for incident HF, adjusting for age, sex, race, education, hypertension medication, blood pressure, BMI, waist circumference, HDL, LDL, triglycerides, lipid-lowering medication, smoking, alcohol, serum creatinine, and interim CHD.

RESULTS

T2D participants had higher mean CIMT (0.79±0.20mm), compared to IFG (0.75±0.19mm) and NFG (0.70±0.17mm) (p<0.0001). Over 20.6years of median follow-up, 15% developed HF. Rates of HF (per 1000 person-years) were substantially higher for those with T2D (24.7), compared to IFG (7.7) and NFG (5.8). In adjusted analyses, the CIMT-HF association was significantly modified by diabetes status (P_interaction=0.015): for NFG (HR per SD increase in CIMT: 1.27; 95%CI: 1.20-1.34), IFG (HR 1.18; 95%CI: 1.11-1.25) and T2D (HR 1.12; 95%CI: 1.05-1.21).

CONCLUSIONS

CIMT is associated with increased risk of HF, particularly among persons without diabetes. Due to a high absolute risk of HF among adults with T2D, CIMT may be a less reliable predictor.

Urinary F2-isoprostanes and the risk of hypertension

PURPOSE

There is strong biological plausibility for a causal role of reactive oxygen species in vascular pathology but no direct epidemiological evidence linking elevated reactive oxygen species levels to hypertension development. We examined cross-sectional and prospective associations between oxidative status (urinary F₂-isoprostanes) and hypertension in the Insulin Resistance Atherosclerosis Study cohort (n = 831).

METHODS

The cohort included non-Hispanic white, Hispanic, and non-Hispanic black individuals, with 252 (30%) having prevalent hypertension and 579 participants normotensive at baseline, 122 (21%) of whom developed hypertension during the 5-year follow-up. Four urinary F₂-isoprostane isomers were quantified in baseline specimens using LC/MS-MS and were summarized as a composite index. Examined outcomes included hypertension status (yes/no), systolic (SBP) and diastolic blood pressure (DBP), pulse pressure (PP), and mean arterial pressure (MAP).

RESULTS

Prevalent and incident hypertension were associated with greater age, Black race, impaired glucose tolerance, and greater BMI. F₂-IsoP levels were lower among men and among non-Hispanic Blacks, were inversely associated with age, and were directly associated with BMI. No cross-sectional association was found between F₂-isoprostanes and hypertension status (OR = 0.93, 0.77-0.12). Among the continuous measures of blood pressure only PP was associated with F₂-isoprostanes at baseline (beta-coefficient = 0.99, 0.11-1.86). No prospective association was found between F₂-isoprostanes and incident hypertension: OR = 0.98, 0.77-1.25. No prospective associations were found for systolic blood pressure and diastolic blood pressure, and pulse pressure. Mean arterial pressure showed an inverse association (beta-coefficient = -0.16, -0.31 to -0.01).

CONCLUSIONS

Elevated F₂-isoprostane levels do not increase the risk of hypertension.

Association Between Midlife Vascular Risk Factors and Estimated Brain Amyloid Deposition

IMPORTANCE

Midlife vascular risk factors have been associated with late-life dementia. Whether these risk factors directly contribute to brain amyloid deposition is less well understood.

OBJECTIVE

To determine if midlife vascular risk factors are associated with late-life brain amyloid deposition, measured using florbetapir positron emission tomography (PET).

DESIGN, SETTING, AND PARTICIPANTS

The Atherosclerosis Risk in Communities (ARIC)-PET Amyloid Imaging Study, a prospective cohort study among 346 participants without dementia in 3 US communities (Washington County, Maryland; Forsyth County, North Carolina; and Jackson, Mississippi) who have been evaluated for vascular risk factors and markers since 1987-1989 with florbetapir PET scans in 2011-2013. Positron emission tomography image analysis was completed in 2015.

EXPOSURES

Vascular risk factors at ARIC baseline (age 45-64 years; risk factors included body mass index ≥30, current smoking, hypertension, diabetes, and total cholesterol ≥200 mg/dL) were evaluated in multivariable models including age, sex, race, APOE genotype, and educational level.

MAIN OUTCOMES AND MEASURES

Standardized uptake value ratios (SUVRs) were calculated from PET scans and a mean global cortical SUVR was calculated. Elevated florbetapir (defined as a SUVR >1.2) was the dependent variable.

RESULTS

Among 322 participants without dementia and with nonmissing midlife vascular risk factors at baseline (mean age, 52 years; 58% female; 43% black), the SUVR (elevated in 164 [50.9%] participants) was measured more than 20 years later (median follow-up, 23.5 years; interquartile range, 23.0-24.3 years) when participants were between 67 and 88 (mean, 76) years old. Elevated body mass index in midlife was associated with elevated SUVR (odds ratio [OR], 2.06; 95% CI, 1.16-3.65). At baseline, 65 participants had no vascular risk factors, 123 had 1, and 134 had 2 or more; a higher number of midlife risk factors was associated with elevated amyloid SUVR at follow-up (30.8% [n = 20], 50.4% [n = 62], and 61.2% [n = 82], respectively). In adjusted models, compared with 0 midlife vascular risk factors, the OR for elevated SUVR associated with 1 vascular risk factor was 1.88 (95% CI, 0.95-3.72) and for 2 or more vascular risk factors was 2.88 (95% CI, 1.46-5.69). No significant race × risk factor interactions were found. Late-life vascular risk factors were not associated with late-life brain amyloid deposition (for ≥2 late-life vascular risk factors vs 0: OR, 1.66; 95% CI, 0.75-3.69).

CONCLUSIONS AND RELEVANCE

An increasing number of midlife vascular risk factors was significantly associated with elevated amyloid SUVR; this association was not significant for late-life risk factors. These findings are consistent with a role of vascular disease in the development of Alzheimer disease.

Sex Differences in the Association Between Insulin Resistance and Incident Coronary Heart Disease and Stroke Among Blacks Without Diabetes Mellitus: The Jackson Heart Study

Background

Studies exploring the association between insulin resistance (IR) and cardiovascular disease in blacks have not been conclusive, especially for coronary heart disease (CHD). The McAuley index and homeostasis model assessment of IR (HOMA‐IR) perform differently in predicting cardiovascular disease. We investigated this association in the Jackson Heart Study, a large longitudinal cohort of blacks.

Methods and Results

IR was estimated for 3565 participants without diabetes mellitus and cardiovascular disease at baseline using the McAuley index and HOMA‐IR, and their associations with incident CHD and stroke (composite outcome) were compared. A lower McAuley index and higher HOMA‐IR are indicative of IR. Cox regression analysis was used to estimate adjusted hazard ratios for incident CHD and/or stroke. There were 158 events (89 CHD‐only, 58 stroke‐only, and 11 CHD/stroke) over a median follow‐up of 8.4 years. After adjustment for demographic factors, the risk of the composite outcome decreased with each SD increase in the McAuley index (hazard ratio 0.80; 95% CI: 0.67–0.96), with no attenuation after further accounting for CHD and stroke risk factors. When considered individually, McAuley index and HOMA‐IR were associated with CHD (hazard ratio 0.71, 95% CI: 0.55–0.92 and hazard ratio 1.33, 95% CI: 1.03–1.72, respectively), but not stroke risk. The logHOMA‐IR and CHD association was present in men, but not in women (P_interaction=0.01).

Conclusions

Both HOMA‐IR and the McAuley index demonstrate strong associations with CHD but not stroke risk in blacks. The logHOMA‐IR and CHD association was present in men, but not in women.

Genetic modifiers of cardiorespiratory fitness response to lifestyle intervention

PURPOSE

Numerous prospective studies indicate that improved cardiorespiratory fitness reduces type 2 diabetes risk and delays disease progression. We hypothesized that genetic variants modify fitness response to an intensive lifestyle intervention (ILI) in the Action for Health in Diabetes (Look AHEAD) randomized clinical trial, aimed to detect whether ILI will reduce cardiovascular events in overweight/obese subjects with type 2 diabetes compared with a standard of care.

METHODS

Polymorphisms in established fitness genes and in all loci assayed on the Illumina CARe iSelect chip were examined as predictors of change in MET level, estimated using a treadmill test, in response to a 1-yr intervention in 3899 participants.

RESULTS

We identified a significant signal in previously reported fitness-related gene RUNX1 that was associated with 1-yr METs response in ILI (0.19 ± 0.04 MET less improvement per minor allele copy; P = 1.9 × 10(-5)) and genotype-intervention interaction (P = 4.8 × 10(-3)). In the chipwide analysis, FKBP7 rs17225700 showed a significant association with ILI response among subjects not receiving beta-blocker medications (0.47 ± 0.09 METs less improvement; P = 5.3 × 10(-5)) and genotype-treatment interaction (P = 5.3 × 10(-7)). The Gene Relationships Among Implicated Loci pathway-based analysis identified connections between associated genes, including those influencing vascular tone, muscle contraction, cardiac energy substrate dynamics, and muscle protein synthesis.

CONCLUSIONS

This is the first study to identify genetic variants associated with fitness responses to a randomized lifestyle intervention in overweight/obese diabetic individuals. RUNX1 and FKBP7, involved in erythropoesis and muscle protein synthesis, respectively, are related to change in cardiorespiratory fitness in response to exercise.

Analysis of Whole Exome Sequencing with Cardiometabolic Traits Using Family-Based Linkage and Association in the IRAS Family Study

Family-based methods are a potentially powerful tool to identify trait-defining genetic variants in extended families, particularly when used to complement conventional association analysis. We utilized two-point linkage analysis and single variant association analysis to evaluate whole exome sequencing (WES) data from 1205 Hispanic Americans (78 families) from the Insulin Resistance Atherosclerosis Family Study. WES identified 211,612 variants above the minor allele frequency threshold of ≥0.005. These variants were tested for linkage and/or association with 50 cardiometabolic traits after quality control checks. Two-point linkage analysis yielded 10,580,600 logarithm of the odds (LOD) scores with 1148 LOD scores ≥3, 183 LOD scores ≥4, and 29 LOD scores ≥5. The maximal novel LOD score was 5.50 for rs2289043:T>C, in UNC5C with subcutaneous adipose tissue volume. Association analysis identified 13 variants attaining genome-wide significance (P < 5 × 10^-08 ), with the strongest association between rs651821:C>T in APOA5 and triglyceride levels (P  =  3.67 × 10^-10 ). Overall, there was a 5.2-fold increase in the number of informative variants detected by WES compared to exome chip analysis in this population, nearly 30% of which were novel variants relative to the Database of Single Nucleotide Polymorphisms (dbSNP) build 138. Thus, integration of results from two-point linkage and single-variant association analysis from WES data enabled identification of novel signals potentially contributing to cardiometabolic traits.

Repeatability of ectopic beats from 48-hr ambulatory electrocardiography: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

The purpose of this study was to characterize the repeatability of ectopic beats, defined by premature atrial contractions (PACs) and premature ventricular contractions (PVCs), on ambulatory electrocardiogram (aECG) monitoring and evaluate the effect of length of aECG monitoring on the repeatability estimates.

METHODS

This analysis includes 95 randomly selected participants from the Atherosclerosis Risk in Communities Study (ARIC; 2011-2013). The participants wore a Holter monitor for two, 48-hr periods separated by a mean of 38 days following an identical, standardized protocol. We divided each 48-hr recording into 3-, 6-, 12-, and 24-hr recording periods and calculated intraclass correlation coefficients (ICCs) for PACs and PVCs and also as a percentage of the corresponding total of recorded beats per hour among these periods.

RESULTS

All participants had ≥1 PAC during the 48-hr recordings, and only two participants had no PVCs. ICCs were >0.83 for all indices and recording lengths ≥12 hrs. ICCs were intermediate for 6-hr recordings (range 0.80-0.83) and lower for 3-hr recordings (range 0.74-0.80). The ratio of the between- to within-participant variation increased with recording length.

CONCLUSION

Repeatability of PACs and PVCs was excellent for recording lengths of 6-24 hr and fair for 3 hr. Repeatability varies over shorter duration recordings within the 48-hr recording period, and thus the present results have implications for detection algorithms for ectopic beats and can facilitate epidemiologic and clinical applications in which knowledge of measurement variability and misclassification are needed.

GENOME-WIDE INTERACTION WITH SELECTED TYPE 2 DIABETES LOCI REVEALS NOVEL LOCI FOR TYPE 2 DIABETES IN AFRICAN AMERICANS

Type 2 diabetes (T2D) is the result of metabolic defects in insulin secretion and insulin sensitivity, yet most T2D loci identified to date influence insulin secretion. We hypothesized that T2D loci, particularly those affecting insulin sensitivity, can be identified through interaction with known T2D loci implicated in insulin secretion. To test this hypothesis, single nucleotide polymorphisms (SNPs) nominally associated with acute insulin response to glucose (AIRg), a dynamic measure of first-phase insulin secretion, and previously associated with T2D in genome-wide association studies (GWAS) were identified in African Americans from the Insulin Resistance Atherosclerosis Family Study (IRASFS; n=492 subjects). These SNPs were tested for interaction, individually and jointly as a genetic risk score (GRS), using GWAS data from five cohorts (ARIC, CARDIA, JHS, MESA, WFSM; n=2,725 cases, 4,167 controls) with T2D as the outcome. In single variant analyses, suggestively significant (Pinteraction < 5×10-6) interactions were observed at several loci including DGKB (rs978989), CDK18 (rs12126276), CXCL12 (rs7921850), HCN1 (rs6895191), FAM98A (rs1900780), and MGMT (rs568530). Notable beta-cell GRS interactions included two SNPs at the DGKB locus (rs6976381; rs6962498). These data support the hypothesis that additional genetic factors contributing to T2D risk can be identified by interactions with insulin secretion loci.

Whole genome sequence analysis of serum amino acid levels

Background

Blood levels of amino acids are important biomarkers of disease and are influenced by synthesis, protein degradation, and gene–environment interactions. Whole genome sequence analysis of amino acid levels may establish a paradigm for analyzing quantitative risk factors.

Results

In a discovery cohort of 1872 African Americans and a replication cohort of 1552 European Americans we sequenced exons and whole genomes and measured serum levels of 70 amino acids. Rare and low-frequency variants (minor allele frequency ≤5%) were analyzed by three types of aggregating motifs defined by gene exons, regulatory regions, or genome-wide sliding windows. Common variants (minor allele frequency >5%) were analyzed individually. Over all four analysis strategies, 14 gene–amino acid associations were identified and replicated. The 14 loci accounted for an average of 1.8% of the variance in amino acid levels, which ranged from 0.4 to 9.7%. Among the identified locus–amino acid pairs, four are novel and six have been reported to underlie known Mendelian conditions. These results suggest that there may be substantial genetic effects on amino acid levels in the general population that may underlie inborn errors of metabolism. We also identify a predicted promoter variant in AGA (the gene that encodes aspartylglucosaminidase) that is significantly associated with asparagine levels, with an effect that is independent of any observed coding variants.

Conclusions

These data provide insights into genetic influences on circulating amino acid levels by integrating -omic technologies in a multi-ethnic population. The results also help establish a paradigm for whole genome sequence analysis of quantitative traits.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1106-x) contains supplementary material, which is available to authorized users.