Decreased oxidant profile and increased antioxidant capacity in naturally postmenopausal women

Abstract

Recent works have shown a dual side of estrogens, and research on the relationship between oxidative stress and menopausal status remains unclear and has produced controversial results. In this work, we aimed to evaluate by sensitive methods the oxidant and antioxidant changes that develop after natural menopause. Thirty premenopausal and 28 naturally postmenopausal women volunteered for this study. Blood was collected and plasma used. 17-OH estradiol levels in plasma were estimated. Plasma levels of advanced oxidation protein products (AOPP), lipid peroxidation products (such as hydroperoxides and malondialdehyde (MDA)), and nitrites were measured, and total radical antioxidant parameter testing was performed to determine the oxidant and antioxidant profiles, respectively. Estrogen levels were significantly increased (p < 0.02) in premenopausal women (54.28 ± 9.34 pg/mL) as compared with postmenopausal women (18.10 ± 1.49 pg/mL). Postmenopausal women had lower levels of lipid hydroperoxide oxidation (p < 0.0001), lipid hydroperoxide levels evaluated by the area under the curve (AUC; 1,366,000 ± 179,400 AUC; p < 0.01), and hydroperoxides as measured by the ferrous oxidation-xylenol orange method (31.48 ± 2.7 μM; p < 0.0001). The MDA levels did not differ between pre- and postmenopausal women whether measured by thiobarbituric acid-reactive substances or high-performance liquid chromatography assays. No differences in AOPP and nitrite levels were observed between pre- and postmenopausal women. Postmenopausal women also exhibited a higher total radical antioxidant level (0.89 ± 0.08 μM Trolox; p < 0.0001). Postmenopausal women demonstrated lower levels of oxidative damage and a higher antioxidant capacity than premenopausal women.

Fig. 1

Plasma oxidative stress evaluated by high-sensitivity chemiluminescence. a Profile of peroxidation, b area under curve (AUC), and c statistical significance of curves are shown. RUL relative unities of lights, pre premenopausal women, post postmenopausal women. *p < 0.0001, statistically significant

Fig. 2

a Hydroperoxide levels measured by the FOX assay, b malondialdehyde (MDA) levels measured by thiobarbituric acid-reactive substances (TBARs), c MDA measured by HPLC, and d nitrite levels. PRE premenopausal women, POST postmenopausal women. *p < 0.0001, statistically significant

Fig. 3

Advanced oxidation protein products (AOPP). pre premenopausal women, post postmenopausal women

Fig. 4

Antioxidant profile determined by total radical-trapping antioxidant parameter (TRAP). pre premenopausal women, post postmenopausal women. *p < 0.0001, statistically significant