RESUMEN
During perimenopause, oxidative stress increases, which may result in disruption of bone turnover, and consequently in osteoporosis. The use of antioxidants may be an effective nutritional approach to reducing osteoporosis in this period of life. Mate tea (MT) (Ilex paraguariensis), a typical and inexpensive beverage consumed in the Brazilian south-east, Argentina and Uruguay, increases antioxidant defense. Our hypothesis was that MT would decrease oxidative stress and mitigate bone deterioration. To test this, we analyzed oxidative stress markers of bone turnover, and local and systemic markers of bone metabolism of rats during natural perimenopause. Female Wistar rats (aged 16months) in proven perimenopause period received 20mg/kgBW/day of mate tea, by gavage (PM+MT Group, n=10) or water (PM Group, n=10). Female rats aged 4months (AD Group, n=10) received water. The treatment period was four weeks. MT minimized the deterioration of rat microarchitecture, characterized by increase in the bone trabecular area, number of osteocytes and areal bone mineral density. These results were accompanied by a lower level of malondialdehyde, an oxidative stress marker, in femoral tissue homogenate. Plasmatic tartrate-resistant acid phosphatase, a typical osteoclastic function marker, decreases after treatment, indicating a decrease in osteoclastic function. MT also modified the immunostaining pattern of bone metabolism markers, decreasing the receptor activator of nuclear factor kappa-B ligant (RANKL), superoxide dismutase isoform 2 (SOD2) and increasing osteoprotegerin (OPG), a decoy receptor for the RANKL, which positively modulates bone mass. These results suggested MT was capable of decreasing bone resorption by inhibiting the osteoclastogenesis in a RANKL-dependent signaling pathway activated by oxidative stress. Taken together, the results indicated that MT minimized bone loss in perimenopause and this effect is at least partly due to the decrease in oxidative stress, confirming our hypothesis.