Effect of estrogen on the size of low-density lipoprotein particles in postmenopausal women

Abstract

Objective: To investigate the effects of estrogen on the size o low-density lipoprotein (LDL) particles in postmenopausal women.

Methods: We treated 20 postmenopausal women with 0.625 mg of conjugated equine estrogen daily for 3 months and measured the plasma levels of total cholesterol, triglyceride, high-density lipoprotein (HDL), and apolipoproteins A-I, A-II, and B before and after therapy. We also analyzed concentrations of LDL cholesterol and LDL apolipoprotein B. The diameter of LDL particles was determined by gradient gel electrophoresis.

Results: Estrogen caused significant decreases in the plasma levels of total cholesterol and apolipoprotein B and significant increases in the plasma levels of triglyceride, HDL cholesterol, and apolipoprotein A-I and A-II. Mean levels of LDL cholesterol and LDL apolipoprotein B were reduced significantly (by 16.31%, P < .001, and 16.91%, P < .001, respectively) after estrogen treatment. Estrogen also significantly reduced the size of LDL particles, from 25.74 +/- 0.66 (mean +/- standard deviation) to 24.95 +/- 0.78 nm (P < .001). The LDL particle diameter correlated negatively with the plasma level of triglyceride (pre-treatment: r = 0.87, P < .001; post-treatment: r = 0.88, P < .001). Estrogen significantly increased the prevalence of LDL subclass pattern B, from 30 to 65% (P < .03).

Conclusion: Estrogen affects lipid metabolism favorably by reducing the plasma concentration of LDL particles. Estrogen-induced increase in the plasma level of triglyceride appears to reduce the size of LDL particles.