Treatment with hormone replacement therapy lowers remnant lipoprotein particles in healthy postmenopausal women: results from a randomized trial

Background Recent evidence indicates that remnant lipoprotein particles (RLPs) may play a role in atherosclerosis. Remnant lipoprotein particles have been suggested to be the most atherogenic particles among the triglyceride-rich lipoproteins. In particular, these triglyceride-rich particles were identified as an independent risk factor for cardiovascular diseases (CVD) in women. Postmenopausal hormone replacement therapy (HRT) beneficially affects lipid profile, although total triglyceride levels often increase. Evidence on the effects of HRT on RLPs is limited. We determined whether 3 months' treatment of postmenopausal women with Tibolone or conjugated oestrogens combined with medroxyprogesterone acetate (CEE + MPA) affects RLP-cholesterol (RLP-C). Materials and methods One hundred and five healthy postmenopausal women were randomized to either 2.5 mg of Tibolone, 0.625 mg of CEE + 2.5 mg of MPA or placebo. At baseline and after 3 months the lipid profile was determined. For assessment of RLP-C we used an immunoseparation-based method. Results Treatment with CEE + MPA significantly reduced RLP-C (-0.03 mmol L-1 , P -value = 0.01) and appeared to increase triglycerides (0.15 mmol L-1 , P -value = 0.20) compared with placebo. Tibolone did not significantly change RLP-C (-0.01 mmol L-1 , P -value = 0.35) and significantly decreased triglycerides (-0.35 mmol L-1 , P -value = 0.004). Conclusions Treatment of postmenopausal women with conjugated oestrogens and medroxyprogesterone acetate reduced RLP-C, without a reduction in total triglycerides, whereas Tibolone did affect triglyceride levels, but not RLP-C. These observations may be relevant for explaining the effect of HRT on cardiovascular risk in healthy postmenopausal women.