Background: Postmenopausal women have increased oxidative stress and decreased antioxidant status. Estrogen has great antioxidant capacity both in vitro and in vivo. Few authors have studied the effect that hormone replacement therapy (HRT) has on the oxidant and antioxidant status and none have studied the effect on DNA oxidation as a possible explanation for the aging process itself.
Aim: The aim of this study was to evaluate both oxidation and antioxidation markers in postmenopausal woman and to determine the effects that HRT has on them.
Method: Sixty-two postmenopausal women with similar biophysical characteristics were divided into three groups: (1) 18 not taking any HRT, (2) 20 receiving estrogen-only replacement therapy (ERT, conjugated equine estrogen), and (3) 22 receiving combined estrogen/progestin HRT (conjugated equine estrogen + medroxyprogesterone acetate). Specific molecular oxidative damage was detected by measuring 8- hydroxy-2-deoxy guanosine (8-OH-2dG) (DNA damage), standardized thiobarbituric acid reactive substances (TBARS) (lipid damage) and protein carbonyl (proteins). Antioxidant enzyme activity was detected by measuring catalase activity, and total antioxidant status was measured using 1,1,difenil-2-picril hydrazil. Both ELISA and photometric methods were used.
Results: 8-OH-2dG levels were significantly lower in women who received combined HRT compared to women who did not receive HRT (ANOVA, p < 0.05). Lipid oxidation was significantly lower in women on ERT compared to women taking no HRT (ANOVA, p < 0.05). Pearson correlation showed that lipid oxidation decreased as the estradiol concentration increased within the study range (r = -0.362, p < 0.05). No statistical difference was noted for protein oxidation and catalase activity among the groups. No statistical difference was found for total antioxidant status between the groups (ANOVA).
Conclusions: HRT decreases oxidative damage to both DNA and lipids in postmenopausal women. Lipid oxidation status may be inversely related to estrogen levels in postmenopausal women.