Tetrahydroxy stilbene glucoside for alleviating osteoporosis: Elevating autophagy to attenuate osteoblast dysfunction mediated by the AMPK/mTOR/ULK1 pathway

Abstract

Osteoporosis, a systemic metabolic disease, typically leads to osteogenic dysfunction with aging, which is the primary mechanism underlying the decrease in bone mass and strength. Polygonum multiflorum Thunb., a Chinese botanical drug known for kidney-tonifying and bone-fortifying effects, comprises 2,3,5,4′-Tetrahydroxy stilbene-2-O-β-d-glucoside (TSG) as its key component, which demonstrates potential for preventing and managing osteoporosis. However, its specific role in oxidative stress-induced osteoblast dysfunction remains unclear. Here, we constructed osteoblasts model of oxidative damage and a mouse model of senile osteoporosis. Alkaline phosphatase (ALP) and Alizarin Red S staining analysis, as well as histological, trabecular microstructure and indexes of bone metabolism were used to evaluate osteogenic function. Flow cytometry, western blot and qRT-PCR were employed to identify apoptosis and autophagy pathways affected by TSG. The results showed that TSG pretreatment significantly reduced apoptosis and suppressed mitochondrial apoptosis pathway proteins in H₂O₂-exposed osteoblasts, thereby mitigating oxidative damage. TSG also increased ALP expression, mineralization, and the expression of osteogenic factors. Furthermore, TSG aggravated autophagy induced by H₂O₂, while the anti-apoptotic and mineralization-promoting effects were inhibited by 3-methyladenine and enhanced by rapamycin. Mechanistically, TSG resulted in the activation of the AMPK/mTOR/ULK1 pathway, which was partially reversed by AMPK inhibition, thereby ameliorating osteoblast dysfunction. Finally, we confirmed that TSG treatment reversed bone loss by improving trabecular microstructure, balancing bone metabolic factors, and enhancing bone morphogenetic protein expression. Collectively, our findings provide a potential therapeutic strategy for alleviating osteoporosis.