Association of Apolipoprotein B Gene Signal Peptide Insertion-Deletion Polymorphism and the Associated Lipid levels with Coronary Artery Disease

Background and objectives - Apolipoprotein B (apo B) is the principal structural protein of low density lipoprotein (LDL), involved in the lipoprotein metabolism and in maintaining the cholesterol homeostasis. It functions as a ligand for the LDLreceptor, thus mediating the cellular uptake of cholesterol. A polymorphism located in the coding part of the signal peptide of APOB gene has been associated with altered lipid levels, mainly increased plasma total cholesterol, LDL and apo B concentrations. We carried out this study to determine the association of APOB signal peptide Ins- Del polymorphism and its associated lipid levels with coronary atherosclerosis. Methods - Genotype analysis was done on 100 patients with angiographically proven coronary atherosclerosis and 100 control subjects by polymerase chain reaction. Serum lipids and apolipoprotein B were measured. Results - Patients had significantly higher frequency of Del (ID and DD) genotype than control subjects (0.51 versus 0.27, p - 0.001) with odds ratio of 2.8 (1.6 to 5.1, P - 0.001) between Del (ID and DD) genotype and II genotype for developing coronary atherosclerosis. Significantly higher levels of apo B (148.2 mg per dL versus 106.4, p - 0.000) was observed in coronary atherosclerosis patients as compared to control subjects. Conclusions - The APOB signal peptide Ins-Del polymorphism and its associated high level of apo B were significantly associated with coronary artery disease. The high level of apo B may be an independent risk factor for coronary atherosclerosis.