Effects of apolipoprotein E polymorphism on plasma lipoprotein(a) levels

Effects of apolipoprotein E (apo E) genetic polymorphism on plasma lipoprotein(a) (Lp(a)) levels were investigated in 305 civil service workers (158 men and 147 women). Plasma Lp(a) levels were measured by ELISA. Apo E phenotypes were determined from plasma by isoelectric focusing, Western blotting and immunostaining, as we previously reported. A total of 305 subjects were divided into the three apo E groups; apo E2 group (n = 19 for apo E3/2 and n = 4 for apo E4/2), Apo E3/3 group (n = 224) and apo E4/3 group (n = 58). Mean levels of plasma Lp(a) were 14.2 mg/dl. Plasma Lp(a) levels were significantly lower in the apo E2 group (6.6 mg/dl) than in the apo E3/3 (15.1 mg/dl) and E4/3 (13.7 mg/dl) groups. Plasma total cholesterol (T-chol) and low density lipoprotein (LDL)-chol levels were significantly lower in the apo E2 group than in the apo E4/3 group and tended to be highest in the apo E4/3 group. A significant positive correlation was noted between plasma Lp(a) levels and plasma LDL-chol levels, indicating that the effects of apo E polymorphism on plasma Lp(a) levels were parallel to its effects on plasma LDL-chol levels. In women plasma Lp(a) levels were significantly lower in the apo E2 group than in the apo E3/3 and E4/3 groups, whereas in men plasma Lp(a) levels tended to be lower in the apo E2 group but no significant difference was noted among the three apo E groups. It is concluded that plasma Lp(a) levels are, at least in part, modulated by apo E polymorphism (particularly apo E2) and that there is a gender difference in the effects of apo E polymorphism on plasma Lp(a) levels.