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Admixture mapping scans identify a locus affecting retinal vascular caliber in hypertensive African Americans: the Atherosclerosis Risk in Communities (ARIC) study.

ABSTRACT: Retinal vascular caliber provides information about the structure and health of the microvascular system and is associated with cardiovascular and cerebrovascular diseases. Compared to European Americans, African Americans tend to have wider retinal arteriolar and venular caliber, even after controlling for cardiovascular risk factors. This has suggested the hypothesis that differences in genetic background may contribute to racial/ethnic differences in retinal vascular caliber. Using 1,365 ancestry-informative SNPs, we estimated the percentage of African ancestry (PAA) and conducted genome-wide admixture mapping scans in 1,737 African Americans from the Atherosclerosis Risk in Communities (ARIC) study. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) representing summary measures of retinal arteriolar and venular caliber, respectively, were measured from retinal photographs. PAA was significantly correlated with CRVE (rho = 0.071, P = 0.003), but not CRAE (rho = 0.032, P = 0.182). Using admixture mapping, we did not detect significant admixture association with either CRAE (genome-wide score = -0.73) or CRVE (genome-wide score = -0.69). An a priori subgroup analysis among hypertensive individuals detected a genome-wide significant association of CRVE with greater African ancestry at chromosome 6p21.1 (genome-wide score = 2.31, locus-specific LOD = 5.47). Each additional copy of an African ancestral allele at the 6p21.1 peak was associated with an average increase in CRVE of 6.14 microm in the hypertensives, but had no significant effects in the non-hypertensives (P for heterogeneity <0.001). Further mapping in the 6p21.1 region may uncover novel genetic variants affecting retinal vascular caliber and further insights into the interaction between genetic effects of the microvascular system and hypertension.

SUBMITTER: Cheng CY

PROVIDER: S-EPMC2855324 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Admixture mapping scans identify a locus affecting retinal vascular caliber in hypertensive African Americans: the Atherosclerosis Risk in Communities (ARIC) study.

Cheng Ching-Yu CY Reich David D Wong Tien Y TY Klein Ronald R Klein Barbara E K BE Patterson Nick N Tandon Arti A Li Man M Boerwinkle Eric E Sharrett A Richey AR Kao W H Linda WH

PLoS genetics 20100415 4

Retinal vascular caliber provides information about the structure and health of the microvascular system and is associated with cardiovascular and cerebrovascular diseases. Compared to European Americans, African Americans tend to have wider retinal arteriolar and venular caliber, even after controlling for cardiovascular risk factors. This has suggested the hypothesis that differences in genetic background may contribute to racial/ethnic differences in retinal vascular caliber. Using 1,365 ance ...[more]

PMID: 20419148

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Project description:BackgroundLow serum magnesium levels have been associated with multiple chronic diseases. The regulation of serum magnesium homeostasis is not well understood. A previous genome-wide association study (GWAS) of European ancestry (EA) populations identified nine loci for serum magnesium. No such study has been conducted in African-Americans, nor has there been an evaluation of the interaction of magnesium-associated SNPs with environmental factors. The goals of this study were to identify genetic loci associated with serum magnesium in an African-American (AA) population using both genome-wide and candidate region interrogation approaches and to evaluate gene-environment interaction for the magnesium-associated variants in both EA and AA populations. We conducted a GWAS of serum magnesium in 2737 AA participants of the Atherosclerosis Risk in Communities (ARIC) Study and interrogated the regions of the nine published candidate loci in these results. Literature search identified the influence of progesterone on MUC1 expression and insulin on TRPM6 expression.ResultsThe GWAS approach in African-American participants identified a locus near MUC1 as genome-wide significant (rs2974937, beta=-0.013, p=6.1x10(-9)). The candidate region interrogation approach identified two of the nine loci previously discovered in EA populations as containing SNPs that were significantly associated in African-American participants (SHROOM3 and TRPM6). The index variants at these three loci together explained 2.8 % of the variance in serum magnesium concentration in ARIC African-American participants. On the test of gene-environment interaction in ARIC EA participants, the index variant at MUC1 had 2.5 times stronger association in postmenopausal women with progestin use (beta=-0.028, p=7.3x10(-5)) than in those without any hormone use (beta=-0.011, p=7.0x10(-8), p for interaction 0.03). At TRPM6, the index variant had 1.6 times stronger association in those with lower fasting insulin levels (<80 pmol/L: beta=-0.013, p=1.6x10(-7); ≥80 pmol/L: beta=-0.008, p=1.8x10(-2), p for interaction 0.03).ConclusionsWe identified three loci that explained 2.8% of the variance in serum magnesium concentration in ARIC African-American participants. Following-up on functional studies of gene expression identified gene-environment interactions between progestin use and MUC1 and between insulin and TRPM6 on serum magnesium concentration in ARIC European-American participants. These results extend our understanding of the metabolism of serum magnesium.

Project description:BACKGROUND:Evidence suggests glucose transporter-1 (GLUT1) genetic variation affects diabetic nephropathy and albuminuria. Our aim was to evaluate associations with albuminuria of six GLUT1 single nucleotide polymorphisms(SNPs), particularly XbaI and the previously associated Enhancer-2 (Enh2) SNP. METHODS:A two-stage case-control study was nested in a prospective cohort study of 2156 African Americans and 8122 European Americans with urinary albumin-to-creatinine ratio (ACR). Cases comprised albuminuria (N = 825; ? 30 ?g/mg) and macroalbuminuria (N = 173; ? 300 ?g/mg). ACR < 30 ?g/mg classified controls (n = 9453). Logistic regression and odds ratios (OR) assessed associations. The evaluation phase (stage 1, n = 2938) tested associations of albuminuria (n = 305) with six GLUT1 SNPs: rs841839, rs3768043, rs2297977, Enh2(rs841847) XbaI (rs841853), and rs841858. Enh2 was examined separately in the replication phase (stage 2, n = 7340) and the total combined sample (n = 10,278), with all analyses stratified by race and type 2 diabetes. RESULTS:In European Americans, after adjusting for diabetes and other GLUT1 SNPs in stage 1, Enh2 risk genotype (TT) was more common in albuminuric cases (OR = 3.37, P = 0.090) whereas XbaI (OR = 0.94, p = 0.931) and remaining SNPs were not. In stage 1, the Enh2 association with albuminuria was significant among diabetic European Americans (OR = 2.36, P = 0.025). In African Americans, Enh2 homozygosity was rare (0.3%); XbaI was common (18.0% AA) and not associated with albuminuria. In stage 2 (n = 7,340), Enh2 risk genotype had increased but non-significant OR among diabetic European Americans (OR = 1.66, P = 0.192) and not non-diabetics (OR = 0.99, p = 0.953), not replicating stage 1. Combining stages 1 and 2, Enh2 was associated with albuminuria (OR 2.14 [1.20-3.80], P = 0.009) and macroalbuminuria (OR 2.69, [1.02-7.09], P = 0.045) in diabetic European Americans. The Enh2 association with macroalbuminuria among non-diabetic European Americans with fasting insulin (OR = 1.84, P = 0.210) was stronger at the highest insulin quartile (OR = 4.08, P = 0.040). CONCLUSIONS:As demonstrated with type 1 diabetic nephropathy, the GLUT1 Enh2 risk genotype, instead of XbaI, may be associated with type 2 diabetic albuminuria among European Americans, though an association is not conclusive. The association among diabetic European Americans found in stage 1 was not replicated in stage 2; however, this risk association was evident after combining all diabetic European Americans from both stages. Additionally, our results suggest this association may extend to non-diabetics with high insulin concentrations. Rarity of the Enh2 risk genotype among African Americans precludes any definitive conclusions, although data suggest a risk-enhancing role.

Dataset Information

Admixture mapping scans identify a locus affecting retinal vascular caliber in hypertensive African Americans: the Atherosclerosis Risk in Communities (ARIC) study.

Publications

Admixture mapping scans identify a locus affecting retinal vascular caliber in hypertensive African Americans: the Atherosclerosis Risk in Communities (ARIC) study.

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