Postmenopausal
estrogen therapy reduces cardiovascular morbidity and mortality, except in women with advanced
coronary disease. This beneficial effect is partly attributed to a reduction of fasting plasma total and
low-density lipoprotein cholesterol (
LDL-C) and an elevation of plasma
high-density lipoprotein cholesterol (HDL-C) concentrations. Since postprandial
lipemia seems to play a role in the pathogenesis of
coronary artery disease, we evaluated the effect of
hormone replacement therapy (HRT) on postprandial
lipoprotein metabolism in 14 normolipemic postmenopausal women. A
vitamin A fat-loading test before and after three cycles of treatment with a sequential combination of
conjugated equine estrogen (CEE) and
medroxyprogesterone acetate (MPA) was used to label
chylomicrons and
chylomicron remnants with
retinyl palmitate (RP), and RP clearance was assessed over an 8-hour period postprandially. Following 3 months of HRT, fasting total
cholesterol and
LDL-C levels were reduced 9.8% (P = .049) and 16.5% (P = .023), respectively. Fasting HDL-C levels increased 18.9% (P = .001). Fasting
triglycerides (TGs) increased, but not significantly. Postprandial integrated plasma TGs did not change significantly. The integrated RP levels in whole plasma and
chylomicron (Svedberg flotation units [Sf] > 1,000) and nonchylomicron (Sf < 1,000) fractions were reduced 58% (P = .043), 78% (P = .041), and 75% (P = .001), respectively, after hormonal treatment. Enhanced clearance of
chylomicrons and
chylomicron remnants by HRT may contribute to the protective effect of
estrogens against
cardiovascular disease in normolipemic postmenopausal women.