Effects of Intragenic Variability at 3 Polymorphic Sites of the Apolipoprotein B Gene on Serum Lipids and Lipoproteins in a Multiethnic Asian Population

We determined the allelic (X + /X - , M + /M - , and E + /E - ) distribution frequencies of the Xbal, MspI, and EcoKl restriction fragment length polymorphisms (RFLPs) in the apolipoprotein B gene in a control group of 374 healthy Chinese, Malays, and Indians and in a hyperlipidemic cohort of 131 Chinese patients. Covariability between the RFLPs and serum lipid, lipoprotein, and apolipoprotein concentrations was also studied. We found a lower frequency (average 0.0829) of the X+ allele and higher frequencies of the E+ (average 0.9452) and M+ (average 0.9772) alleles in our study population compared with frequencies reported in other populations. The 3 polymorphic sites did not contribute to significant variations in lipid levels (p \u3e 0.1 in all cases). Also, there was no significant variation in genotype frequencies between the control subjects and the hyperlipidemic subjects. Despite their relative close proximity within the APOB gene sequence, the 3 polymorphic sites did not show any significant linkage disequilibrium. However, the presence of the X + cutting site was in linkage disequilibrium with the Del allele of the 5\u27 insertion-deletion polymorphism and the E — allele was in linkage disequilibrium with the 3\u27 VNTR located near the 3\u27 end of the coding region of the APOB gene