DIFFERENCES IN THE LOW-DENSITY-LIPOPROTEIN SUBFRACTION PROFILE BETWEEN ORAL-CONTRACEPTIVE USERS AND CONTROLS

To investigate the effect of low dose oral contraceptives on the low density lipoprotein (LDL) subfraction profile, the distribution of the LDL subfraction patterns in 20 premenopausal women on oral contraceptive (OC) therapy and 41 premenopausal women not taking gonadal hormones was studied. The LDL subfraction patterns were identified by density gradient ultracentrifugation and each individual LDL subfraction pattern was characterized by the relative contribution of three major LDL subfractions: light, LDL1; intermediate, LDL2; and dense, LDL3 to total LDL. Serum lipid and lipoprotein levels were similar in OC users and controls, except for significantly higher triglyceride levels in OC users. As for the LDL subfraction patterns, among the OC users the mean relative contribution of dense LDL3 to total LDL was significantly higher than in the controls (32% +/- 8% vs. 26% +/- 13%, P < 0.05), whereas the relative contribution of light LDL1 to total LDL was significantly lower (27% +/- 8% vs. 34% +/- 10%, P < 0.01), indicating a higher prevalence of the more dense LDL subfraction patterns among OC users. Furthermore, the distribution of the LDL subfraction patterns in OC users (27% LDL1, 41% LDL2, and 32% LDL3) resembled that of men (25% LDL1, 43% LDL2, and 33% LDL3, n = 59). Statistical analysis revealed that OC use was significantly associated with a more dense LDL subfraction pattern, characterized by an increased relative contribution of LDL3 (+6%, P < 0.05) and a decreased relative contribution of LDL1 (-6%, P < 0.01), even after correcting for the influence of lipid and lipoprotein levels, which in controls were shown to have a significant relation to LDL3 and LDL1, respectively. So, independent of the lipid and lipoprotein levels, low dose OC alter the composition of LDL to a heavy, dense LDL subfraction profile, which reportedly has been associated with an increased risk of atherosclerosis.