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Obesity remains a global public health burden, with 4.7 million premature deaths globally attributed to obesity. Severe obesity (SevO: defined as body mass index (BMI)≥40) is a major risk factor for other comorbidities, including heart disease and Type 2 Diabetes, which disproportionately impact historically marginalized populations, including Hispanic/Latinos. Based on BRFSS data, 24.5% of US Hispanic/Latino adults are projected to have severe obesity by 2030. However, the etiology of the underlying metabolic dysfunction remains unknown. To address this gap, we identified metabolites associated with SevO in genotyped participants aged ≥20 with 25 < BMI ≥ 40 and metabolic data in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). We investigated cross-sectional associations between Blom-transformed metabolites and baseline SevO, adjusting for age, study center, background group, smoking status, and principal components of ancestry, stratified by sex (SUGEN), and meta-analyzed (SAS 9.4). For the top 20 metabolites, we extracted publicly available HCHS/SOL metabolite GWAS (mGWAS) summary statistics to derive metaboQTLs, and summary statistics from a multi-population meta-analysis of SevO (N>70,000) and implemented forward MR analysis using the MendelianRandomization R package (v0.3.0), which provides various robust causal estimation methods for summary data. Anthropometry and data for 640 known Metabolon metabolites were available for 551 females (mean age: 43.3 years, 27% SevO) and 371 males (mean age 43.4 years, 15% SevO). We identified Bonferroni-corrected significant SevO associations (p Cytidine is a pyrimidine nucleoside consisting of D-ribose and cytosine, which is a precursor of cytidine triphosphate required in the one-carbon metabolism pathway to convert phosphatidylcholine (PC) to phosphatidylethanolamine (PE). PC biosynthesis is higher in adipose tissue macrophages in obese mice and humans. Indoleproprionate is a microbial metabolite of tryptophan produced by gut bacteria. Indoleproprionate levels have been shown to be associated with higher microbiome diversity and lower incidence of T2D. Our work points to future efforts to validate findings in other cohorts, including reverse MR to further elucidate the causal relationship between metabolites and severe obesity.

Background: QT interval (QT) genome-wide association studies (GWAS) have identified upwards of 35 common variant loci, including SNPs adjacent to putative transcription elongation factor TCEA3. Transcription elongation control has broad effects on gene expression, the misregulation of which is known to influence cardiac conduction system morphogenesis as well as activation or repression of key regulatory genes. Thus, we hypothesized that a genome-wide gene-gene interaction study of TCEA3 lead SNP rs2298632 would identify novel loci that influence QT. Methods: Using 1000 Genomes imputed data (>20 million SNPs) in n=67,445 participants (69% Caucasian; 18% Hispanic/Latino; 11% African American) from 10 studies, we conducted genome-wide meta-analyses to test for the presence of: interaction effect loci by examining rs2298632xSNP interactions on QT; and joint effect loci by simultaneously examining SNP main effects and rs2298632xSNP interactions on QT. Inverse-variance weighted meta-analysis of genomically controlled ancestry- and study-specific summary effects estimated using multivariable adjusted linear models or generalized estimating equations that incorporated robust standard errors was performed using METAL. SNPs demonstrating evidence of heterogeneity (Cochran’s Q P < 0.05) and SNPs that were infrequent or rare (minor allele frequency [MAF] Results: We identified one genome-wide significant interaction effect locus ( P INT -8 ) at PVT1 (lead SNP: rs4733591; mean MAF = 32%), a long non-coding RNA gene for which previous GWAS identified suggestive associations with left ventricular systolic dysfunction. We also identified four genome-wide significant joint effect loci ( P JOINT -8 ) that mapped within or nearby NUCKS1 (lead SNP: rs823094; MAF = 0.33) , CASR (lead SNP = rs17251221; MAF = 0.13) , ACTBL2 (lead SNP = rs7737409; MAF = 0.22) , and KDM1B (lead SNP = rs34969716; MAF = 0.26) , loci with roles in calcium sensing, regulation of gene expression through histone modification, and tumor suppression. Conclusion: Extension of traditional main effects GWAS to interrogate gene-gene interactions for biologically motivated loci like TCEA3 may help inform the structure and function of genetic pathways underlying complex traits like QT.

Introduction: Mean corpuscular volume (MCV) of red blood cells (RBCs) is a heritable index commonly used in clinical workup of anemia. Macrocytosis, or high MCV, is associated with cardiovascular events in chronic kidney disease patients and all-cause mortality. Genome-wide association studies (GWAS) of MCV have been conducted primarily in European and Asian populations; few have included populations of African or American ancestry. The Multiethnic Genotyping Array (MEGA) was designed to improve variant discovery and fine-mapping in US minorities by better capturing population-specific genetic variation. To identify novel MCV loci and examine evidence of generalization of previously reported MCV loci to populations with African and Amerindian genetic admixture, we conducted a GWAS of African American and Hispanic/Latino Population Architecture using Genomics and Epidemiology (PAGE II) participants on the MEGA array. Methods: We employed Illumina MEGA genotype data to evaluate the association between ~1.5 million SNPs and MCV. Generalized estimating equation models were adjusted for age, sex, current smoking status, study, study center, and the top 10 study-specific principal components of genetic ancestry. Race/ethnic-stratified analyses were combined using inverse-variance weighted fixed-effects meta-analysis to evaluate the entire study sample. Significance thresholds of 1.8x10 -3 and 5x10 -8 were used to define generalization and genome-wide significance, respectively. Results: The study population of 3,734 African Americans and 15,505 Hispanic/Latinos was 62% female with a mean age of 50 (range: 18 to 94 years); 19% of participants were current smokers. Trans-ethnic meta-analysis identified 12 genome-wide significant loci for MCV, including two associations at previously unreported loci: FIGNL1/IKZF1 (chromosome 7p12.2, coded allele frequency [CAF] range=51 to 57%), and LRP6 (chromosome 12p13.2, CAF range=0.3 to 1.7%). FIGNL1 is involved in DNA double-strand-break repair, and IKZF1 is a zinc-finger protein that functions in the hemo-lymphopoetic system. LRP6 encodes an LDL receptor involved in the Wnt/beta-catenin signaling cascade. Ninety-three percent of previously reported MCV loci generalized to the combined PAGE study population, ten at genome-wide significant levels. No previously unreported MCV loci were detected in race/ethnic stratified analyses. Conclusion: Generalization of previously reported MCV loci to African Americans and Hispanic/Latinos highlights the shared genetic architecture of MCV. The potentially novel associations identified at chromosomes 7p12.2 and 12p13.2 also underscore the benefits of performing GWAS in ancestrally diverse populations using arrays that better capture global genetic variation.

Introduction: Variability within the normal population range of hematocrit is associated with stroke and myocardial infarction. Published GWAS of hematocrit have identified multiple loci, yet few studies have included populations of Hispanic or African descent, thereby limiting opportunities to identify population-specific variants or narrow associated regions for functional analysis. We present a fine-mapping analysis of six previously identified hematocrit loci in African American and Hispanic/Latino participants of the PAGE study. Methods: Approximately 200,000 genotyped or imputed Metabochip variants were examined for association with hematocrit (proportion of whole blood comprising red blood cells) in 19,822 Hispanic/Latino and 19,973 African American participants. SNPs were excluded on a population-specific basis if effective heterozygosity was < 30. Primary and conditional analyses were performed in Plink, ProbABEL, or SuGen; fixed-effects meta-analyses were performed in Metal. Trans-ethnic and ancestry-specific meta-analyses were performed in MANTRA to generate 99% credible intervals for previously published variants that generalized to our populations. Results: We first examined whether 8,261 variants in five previously identified hematocrit loci ( HFE , ABO , HK1 , SH2B3 / ATXN2 , and TMPRSS6 ) were associated with hematocrit in our study populations. Three loci generalized (p-4 ) to Hispanic/Latino participants ( ABO, HK1, and TMPRSS6 ) and three generalized to African Americans ( HFE , ABO , and SH2B3/ATXN2 ). Among generalized loci, conditional analyses adjusting for published variants in European-ancestry or East Asian populations did not identify any independently associated SNPs in Hispanic Latinos or African Americans (p-5 ). Trans-ethnic meta-analysis for the ABO locus resulted in a 5 SNP, 13kb 99% credible interval, shorter than both the Hispanic/Latino (17kb) and African American (360kb) credible intervals. In discovery analysis, we identified one variant associated with hematocrit in Hispanic/Latinos at array-wide significance levels ( PROX1 locus, p-7 ). No novel loci were identified in African Americans. Conclusion: Our findings provide evidence that the same genomic loci influence normal variation in hematocrit values across diverse ancestral populations. Trans-ethnic fine mapping of the gene-rich ABO locus—which has been associated with ischemic stroke, thrombosis, and myocardial infarction in addition to hematocrit GWA studies—suggests that a functional variant may reside in the first intron of the ABO coding region. Additionally, identification of previously unidentified associations in Hispanic/Latinos emphasizes the importance of including diverse populations in association studies as well as the potential to identify population-specific functional variants within known or discovery loci.

PR interval (PR) prolongation is a predictor of atrial fibrillation, a common cardiac arrhythmia, and is an established risk factor for pacemaker implantation, heart failure, stroke, and all-cause mortality. Previous genome-wide association studies in European (EU) and African (AA) descent populations have identified multiple loci associated with PR. However, it is unclear whether these loci are relevant in other racial groups, including Hispanic/Latinos (HL). Extending studies to include admixed populations such as HL also provides the potential to narrow regions associated with PR and identify population specific variants. Therefore, we evaluated 1,135 SNPs from four previously identified PR loci ( SCN5A, SCN10A, CAV1-CAV2, and TBX5-TBX3 ), fine-mapped on the Illumina Metabochip for association with PR. Associations were examined using linear regression assuming an additive genetic model and adjusting for global ancestry and clinical covariates (age, sex, RR interval, body mass index, height, systolic blood pressure) in 11,800 HL participants from participating studies of the Population Architecture using Genomics and Epidemiology (PAGE) consortia. Three of the four loci ( SCN5A, SCN10A, and CAV1-CAV2 ) generalized to HL populations ( P 2 >0.2 with EU-identified index SNPs). At each of these loci, we identified SNPs with stronger evidence of association with PR than the EU-identified index SNP when examined in the HL population ( SCN5A : rs7374540; SCN10A : rs6801957; CAV-CAV2 : rs717957). Conditional analyses also identified two additional independent SNPs at each of the three generalized loci ( SCN5A : rs3796387, rs9861242; SCN10A : rs10428132, rs7433723; CAV1-CAV2 : rs3801995, rs3807994), representing potential secondary signals. Furthermore, linkage disequilibrium (LD) patterns in Hispanics enabled the narrowing of the regions flanking the EU-identified index SNPs. For example, at the CAV1-CAV2 locus, HL LD patterns indicated that seven SNPs were in LD with rs3807989, the EU-identified index SNP, compared to 17 SNPs that were in LD with rs3807989 when applying EU LD patterns, reducing the size of the region by 71 kilobases. Finally, we examined evidence for population specific signals outside of the specific regions identified in EU populations which were associated with PR in Hispanics by focusing on SNPs uncorrelated with the EU index signals. At all four loci, multiple SNPs had evidence of association independent of the signals examined based on EU results. In conclusion, the same genetic loci that influence PR in European descent populations are also important in Hispanic populations, although we detected evidence for population specific SNPs. These results emphasize the importance of examining genetic associations in diverse populations in order to narrow the genomic interval for future functional interrogation.

Several loci have been discovered and replicated for urine albumin-creatinine ratio (ACR), a measure of kidney function, in European populations; however, other ethnic populations such as African-Americans have been less studied for this trait. We examined the association of genetic variants on the Metabochip with natural log transformed ACR (ln(ACR)) in 4,629 African-Americans from the Population Architecture using Genomics and Epidemiology (PAGE) Study which includes participants from the Atherosclerosis Risk in Communities (ARIC), Cardiovascular Health Study (CHS), Coronary Artery Risk Development in Young Adults (CARDIA), and Epidemiologic Architecture for Genes Linked to the Environment (EAGLE-BioVU) studies. We then replicated our findings in 1,533 African-American participants from the Multi-Ethnic Study of Atherosclerosis (MESA). Linear regression models were used to examine associations, assuming additive effects of the SNPs. Within each study, models were adjusted for age, field center (where applicable), and principal components of ancestry, and stratified by sex. Fixed effects inverse variance weighted meta-analysis was used to combine results from contributing studies. Array-wide statistical significance was concluded for SNP associations of p-value less than 2.8 x 10-7. Mean ln(ACR) ranged from 1.4 to 2.9 mg/g, average age ranged from 44 to 77 years, and percent female participants ranged from 59-65% in the contributing studies. Four SNPs were significantly associated array-wide with ACR in the discovery sample: rs17399841 in GRHL2 (β=-0.67, MAF=0.01, p=2.7x10-9), rs153914 near SPATA9/RHOBTB3 (β=-0.59, MAF=0.01, p=1.0x10-7), rs17439845 in LEF1 (β=-0.49, MAF=0.02, p=1.3x10-7), and rs11836243 near ZNF641/ANP32D (β=0.23, MAF=0.12, p=1.8x10-7). Of these four loci, only the association of rs17439845 with ACR replicated in MESA (β=-0.36, p=0.038), with a combined discovery-replication beta of -0.46 and p value of 1.8x10-8. Combined discovery-replication for rs17399841, rs153914, and rs11836243 no longer achieved array-wide significance (p-values 9.84x10-7, 1.98x10-5, and 1.32x10-4, respectively). LEF1 is a mediator in the Wnt signaling pathway, and has been previously implicated in systemic lupus erythematosus and osteoporosis, as well as previously associated with waist circumference, echocardiographic traits, bone mineral density, and blood count traits. Continuing studies in diverse populations are warranted to identify a set of loci important in contributing to the variation in ACR.

Introduction: Waist-to-hip ratio (WHR) is associated with cardiometabolic disease and its risk factors independent of body-mass-index (BMI). Previous GWAS on WHR adjusting for BMI (WHR’) have identified several SNPs but mainly among European descent populations (EA SNPs). While these SNPs point to general loci of interest, they are not likely the causal variants. Expanding analyses of these loci to other race and ethnic populations can dually assess whether these loci apply to more diverse populations and utilize differences in genetic linkage disequilibrium (LD) patterns to narrow the region containing the causal variant. Objective: To better capture genetic variants of WHR’ in self-identified African Americans (AA) within 14 loci containing previously reported WHR’ EA SNPs. Methods: Up to 14,322 AA participants (aged 20-93 years, 61% female) were included from seven studies. Individuals were genotyped using the Illumina iSelect Metabochip array consisting of nearly 200,000 SNPs enriched to fine map GWAS signals of cardiometabolic traits, including the 14 WHR’ loci. We modeled WHR’ adjusting for age, sex, study site, and the first three ancestry principle components for each study and conducted an inverse variance weighted meta-analysis. Variants reaching a Bonferroni adjusted threshold of P Results: Within the 14 regions, seven loci (in or near TBX15-WARS2, DNM3-PIGC, GRB14, NISCH-STAB1, ADAMTS9, VEGFA, and RSPO3 ) contained a significant AA SNP. In the GRB14 locus, the AA SNP (rs10195252, P =1.93x10 -06 ) was the same as the EA SNP. Among four of the seven loci, the AA SNPs (rs12096179 near TBX15-WARS2, rs2371767 in ADAMTS9 , rs1358990 near VEGFA, and rs9385487 in RSPO3 ) were not independent of the EA SNPs (LD r 2 ≥0.3), but were more significant in AA, possibly narrowing the region containing the functional variant. Two AA SNPs (rs11715796 in NISCH-STAB1 and rs4916251 near DNM3-PIGC ) suggesting independence from the EA SNP (r 2 NISCH-STAB1 had a stronger association after conditioning on the EA SNP, signifying independence. The AA SNP near DNM3-PIGC was less significant after conditioning, indicating it points to the same signal as the EA SNP. We have identified participants from additional cohorts for inclusion in future analyses and will conduct a sex-stratified analysis to further explore WHR’ loci among AA. Conclusions: Examination of 14 previously identified loci for WHR’ in AA individuals revealed one novel signal in NISCH-STAB1 . Five additional non-independent AA SNPs suggested a narrower region containing the WHR’ altering variant based on the LD structure differences between EA and AA. These findings highlight the value in expanding genetic association studies to other race and ethnic populations.