Body fat distribution and menopause influence the oxidative balance in the feminine organism

BACKGROUND: Recent studies evidenced a key-role of oxidative stress (OS) in the pathogenesis of caridiovascular diseases (CV)(1). These diseases occur with increased frequency in postmenopausal women, possibly in association with overall, mainly abdominal, fat accumulation. OBJECTIVES: We investigated in 100 women the influence of menopausal status on body fat distribution and its correlation with OS. METHODS: Total and regional body fat was measured by dual-energy X-ray absorptiometry (DXA). Sera from all subjects were employed for colorimetric assessement of hydroperoxides concentration (D-Roms test) and total antioxidant power (TAP), by a ferric reduction (FRAP) technique. Antioxidant contributions by thiol groups and uric acid (UA) were assessed by 5,5 -dithiobis-2-nitrobenzoic acid reaction and by an enzymatic assay employing Uricase, respectively. RESULTS: Oral contraceptive users were excluded a posteriori from the study due to a highly significant increase of hydroperoxides (p<0.00001). Independently of age, menopausal transition leads no significative change in hydroperoxides, whereas TAP in the perimenopause increases (p<0.001) with the partial contribution of UA (p<0.05). After adjustment for age, hydroperoxides result positively associated with total (TF) and abdominal (AF) fat mass with similar p value (P<0.05). More significantly TF and AF correlated positively with TAP (p<0.0001 and p<0.00001, respectively). DISCUSSION: Unlike most of the currently available literature on the subject (1, the menopausal transition appears to be associated to a shift of oxidative balance towards the antioxidant component. Thus, the endogen estrogens do not seem to exert the described protective role against the oxidative damage. On the contrary, the syntethic hormones of the contraceptive pills favor a remarkable increase of OS, most probably by induction of metabolic processes which lead to the production of reactive species. The direct proportionality between OS and amount of body fat mass may be explained by the increased availability of lipid, essential for the amplification of oxidative signals.