Postmenopausal hormone replacement therapy and autoantibodies against oxidized LDL

Oxidative modification of low-density lipoprotein (oxLDL) has been suggested to play an important role in the pathogenesis of atherosclerosis, and autoantibodies against oxLDL have recently found to reflect this process. The antioxidant effect and inhibition of LDL oxidation may be one of the cardioprotective mechanisms of postmenopausal estrogen therapy.

The effects of postmenopausal hormone replacement therapy (HRT) on the concentrations of serum lipids and oxLDL autoantibodies were studied in a population-based prospective 1-year study with 64 early postmenopausal women (mean age 52.2 +/- 0.4 (S.E.M.) years). The participants were randomized into two treatment groups: HRT-group: Sequential combination of 2 mg estradiol valerate and 1 mg cyproterone acetate alone or in combination with vitamin D3, 300 IU/day + calcium lactate, 500 mg/day (n = 31) and the non-HRT-group: Calcium lactate, 500 mg/day alone or in combination with vitamin D3, 300 IU/day (n = 33). The groups were well matched regarding age, body mass index and baseline serum lipid concentrations.

The serum concentrations of total cholesterol and LDL-cholesterol decreased in the HRT-group (4.1%, P = 0.05 and 6.4%, P = 0.03, respectively, paired t-test) but did not change in the non-HRT-group. No changes in the serum concentrations of HDL-cholesterol or triglycerides were observed. Additionally, no changes in oxLDL autoantibody concentrations were observed in either group.

Although 1-year HRT lowered serum total- and LDL-cholesterol levels, it did not influence oxLDL antibody titers. On the basis of the present results we cannot question the possibility of there being beneficial effects of HRT on the oxidative modification of LDL. However, this effect is not reflected in the levels of oxLDL autoantibodies.