High-density lipoprotein metabolism in post-menopausal women

Abstract

There is a large decrease in endogenous estrogen production with menopause associated with increases in severity of risk factors for coronary heart disease (CHD), including lower high density lipoprotein cholesterol (HDL-C) concentrations. Exogenous estrogen is administered to decrease the risk of CHD. This project was designed to examine the influence of hormone replacement therapy (HRT), ethnicity, and body composition on cholesterol ester transfer protein (CETP) and lecithin:cholesterol acyltransferase (LCAT) activities, two enzymes involved in HDL metabolism. 205 women participated, 32% of Hispanic origin and 52% not presently undergoing HRT (58% Anglo, 39% Hispanic). CETP and LCAT activities were quantified by a mass transfer method and body composition variables were measured by dual energy x-ray absorptiometry and anthropometry. There were no significant differences in plasma lipids and lipoproteins among HRT groups (non-users, unopposed estrogen, combined therapy). Hispanic women had lower HDL-C concentrations and total plasma cholesterol to HDL-C ratio, and higher triglyceride concentrations and greater susceptibility of low density lipoprotein particles to oxidation. CETP activity was elevated in Hispanic women when compared to Anglo women. The ethnic difference in CETP activity was eliminated once IAAT or measures of trunk fat, but not total body fatness, were controlled. No differences in CETP or LCAT activities were found among HRT groups. Women not undergoing HRT tended to have greater abdominal fat compared to women undergoing either hormone therapy, however differences were not significant. Hispanic women had significantly greater amounts of abdominal fat than did Anglo women, even after adjusting for total body fat. CETP and LCAT activities were positively related to plasma lipids, lipoproteins (exception: negative association with HDL-C), and body composition. Correlations were higher with regional fat measures than with total body fat measures. In conclusion, HRT did not affect CETP or LCAT activities. Results suggest that associations between HRT use and decreased risk of CHD involve other mechanisms. Hispanic women had higher CETP activities and greater distribution of abdominal body fat suggesting that they are at greater risk for CHD compared to Anglo women.