DNA POLYMORPHISMS OF THE APOLIPOPROTEIN-B GENE ARE ASSOCIATED WITH OBESITY AND SERUM-LIPIDS IN HEALTHY INDIANS IN SINGAPORE

Three DNA polymorphisms (Ins/Del, XbaI and EcoRI) of the apolipoprotei n B gene and their influence on body-mass index, serum lipids and apol ipoprotein levels were studied in 181 healthy Indians of both sexes (1 21 males and 60 females), aged between 17 and 71 years. The frequencie s of X+ (XbaI) and Del (Ins/Del) of the signal peptide region in India ns were found to be significantly lower (0.17 and 0.11, respectively) compared to the frequencies in Caucasians (0.50 and 0.32, respectively ) (P < 0.025). The frequency of E- (EcoRI) was similar to that in Cauc asians (0.10 vs 0.15). A highly significant linkage disequilibrium was observed between the XbaI site and Ins/Del polymorphism of the apo B gene in this sample (X2 = 31.9, P < 0.001). The simultaneous presence of Del and X+ allele was significantly associated with higher body mas s index (X2 = 11.43, P < 0.005), serum total cholesterol (X2 = 5.11; P < 0.025) and triglyceride (X = 6.42; P < 0.025) levels. Mean values o f adjusted BMI and serum triglyceride levels were found to be 29.0 +/- 1.92 vs 23.7 +/- 0.67 (P < 0.025) and 278.0 +/- 60.78 vs 140.4 +/- 15 .43 mg/dl (P < 0.05), respectively, in subjects with Del and X+ compar ed to others. The multiple regression tests showed that 3.3 and 5.8% o f the total variability of BMI is explained by Ins/Del and XbaI polymo rphism, respectively, in this sample (P = 0.06 and 0.02), while 3.8% o f serum triglyceride levels was explained by Ins/Del polymorphism of t he apo B gene (P = 0.04). Further, the serum HDL cholesterol level was significantly associated with XbaI polymorphism, with X+ having signi ficantly lower HDL cholesterol, and it explained about 5% of the total variability (P = 0.02).