Effect of Ava II and NcoI polymorphisms at the low density lipoprotein receptor gene on plasma lipid levels in a group of Thai subjects.

The contribution of common genetic variations at the LDL receptor gene in determining interindividual differences in plasma lipid levels in the general population has been observed in several studies. In this study, we employed the PCR-RFLP method to investigate such an effect of the common Ava II (exon 13) and Nco I (exon 18) polymorphisms at the low density lipoprotein (LDL) receptor gene locus in 54 normolipidemic Thai subjects. The mean LDL-C level was slightly higher in the Ava II (+/+) genotype than the other Ava II genotypes. This difference was significant at the 5 per cent level although there were only three homozygotes with Ava II (+/+) genotype. The average effect of Ava II (+) allele was to increase LDL-C level by 6.75 mg/dl. A gene-dosage effect was not observed for this polymorphism. In addition, the subjects with Ava II (+/+) genotype also tended to have high serum total cholesterol and triglyceride and low HDL-C levels. Nco I polymorphism revealed no statistically significant effect on lipid levels in these subjects. However, the subjects with (+) allele tended to have high levels of LDL-C, serum total cholesterol and triglyceride.