A genome-wide scan of serum lipid levels in the Old Order Amish

Elevated serum low density lipoprotein cholesterol (LDL-C) and triglyceride (TG) and decreased high density lipoprotein cholesterol (HDL-C) levels are established risk factors for cardiovascular disease (CVD). To identify quantitative trait loci influencing lipid levels, we conducted genome-wide linkage analyses of total serum cholesterol (TSC), HDL-C, ln-transformed TG (LNTG) and LDL-C levels in 612 individuals from 28 families of the Amish Family Diabetes Study (AFDS). Subjects were genotyped for 373 microsatellite markers covering all 22 autosomes and the X chromosome at an average density of 9.7 centimorgans. All lipid traits exhibited moderate estimated heritability (h2±S.E.): TSC, 0.63±0.11; HDL-C, 0.54±0.08; LNTG, 0.37±0.08; LDL-C, 0.62±0.10. The highest logarithm of the odds (LOD) score observed was 2.47 (P=0.0003), at 3p25 for LDL-C. LOD scores exceeding 2.0 (P<0.001) were also observed at 2p23 (LOD=2.17) and 19p13 (LOD=2.23) for LDL-C, and at 11q23 (LOD=2.03) for LNTG. Three additional regions exhibited LOD scores greater than 1.5, corresponding to a P-value of <0.005. Many of the regions suggestively linked in this genome-wide scan contain genes encoding proteins with established roles in lipid metabolism, including apolipoproteins, peroxisome proliferater-activated receptor-γ and the LDL receptor.