Apolipoprotein B-gene DNA polymorphisms (XbaI and EcoRI), serum lipids, and apolipoproteins in healthy Chinese.

The frequency of restriction fragment length polymorphisms (RFLPs) of the apolipoprotein B (apo B) gene, detected by XbaI and EcoRI, and their influence on serum lipids and apolipoproteins were studied in healthy Chinese of both sexes in Singapore. A total of 221 subjects (150 males, 71 females) were investigated for the XbaI and 159 subjects for the EcoRI polymorphisms, while serum lipids and apolipoprotein levels were available for 196 subjects. The frequency of the X2 allele was found to be significantly lower in the Chinese than that reported in Caucasians from the United Kingdom (0.09 vs. 0.51, P less than 0.001). The haplotype frequencies were also significantly different between the Chinese and Caucasians with a higher frequency of X1R1 in the former compared to the latter (0.85 vs. 0.34, P less than 0.0001). The distribution of RFLP genotypes at both of the restriction sites was at Hardy-Weinberg equilibrium in all groups. The influence of the apo B RFLPs on serum lipids and apolipoprotein levels (apo AI, AII, and B) was studied by both residual and multiple regression analyses considering age, sex, body mass index (BMI), and genotypes as independent variables in all possible combinations. No association was observed between the apo B genotypes and serum lipids or apolipoprotein levels except for high density lipoprotein cholesterol (HDLC), apo AI and AII, with the X2 being associated with significantly lower levels of HDLC as well as apo AI and AII, the effect being stronger in males. These data raise the possibility that the mechanism of reported association between apo B polymorphism and coronary artery disease may be through effects on HDLC.