Study on the unique effects of Wubi Shanyao Pills in improving postmenopausal osteoporosis via the "gut-bone" axis

Postmenopausal Osteoporosis (PMOP) is a prevalent bone disease affecting postmenopausal women. The "gut-bone" axis, a concept indicating a close relationship between gut microbiota and PMOP, is the focus of our study. Wubi Shanyao Pills (WSP), a traditional Chinese compound formula, is known for its beneficial tonic effects on intestinal function. Several individual herbs within its formulation have demonstrated positive effects on PMOP. However, the impact of WSP on PMOP and its underlying mechanisms is a significant area that remains inadequately understood and is the key focus of our research.

Our study aimed to investigate the effects and mechanisms of WSP on improving PMOP. We selected postmenopausal mice and fed them a low-calcium, high-phosphorus diet while administering alendronate tablets at a dosage of 0.14 g/kg, alongside varying doses of WSP (0.375, 0.75, and 1.5 g/kg), once daily. We evaluated the influence of WSP on bone quality in PMOP by assessing grip strength, bone strength, and bone microstructure in the mice. We also analysed the balance between bone resorption and formation by measuring the expression of factors associated with both processes. Additionally, we assessed levels of inflammatory mediators using serum ELISA to detect lipopolysaccharides (LPS). We quantified changes in both relative and absolute abundance of intestinal flora using Accu16STM bacteria. We evaluated the expression of intestinal tight junction proteins and the morphology of intestinal mucosal tissues to assess intestinal barrier function.

Administration of WSP improved bone quality in PMOP mice by increasing the number of bone trabeculae and enhancing overall bone strength. It inhibited the expression of bone resorption-related factors, including Cross-linked C-telopeptide of type Ⅰ collagen (CTX-Ⅰ), Tartrate-resistant acid phosphatase (TRAP), receptor activator of nuclear factor-κB (RANK), and receptor activator of nuclear factor-κB ligand (RANKL), while promoting the levels of bone formation-related markers such as bone-specific alkaline phosphatase (BALP), procollagen I n-terminal propeptide (PINP), bone glycoprotein (BGP), bone morphogenetic protein 2 (BMP-2), and SMAD1/5. Additionally, WSP was found to reduce serum LPS levels and inflammatory factors. Further analysis of the intestinal flora revealed that WSP may be could decrease the absolute abundance of Mucispirillum, Desulfovibrionaceae, Desulfovibrio, and other microorganisms significantly correlated with elevated levels of LPS and inflammatory factors. It also upregulated the expression of tight junction proteins ZO-1, Occludin, and Claudin in the colon, thereby enhancing intestinal integrity.

Our research suggests that WSP holds potential for improving osteoporosis in the PMOP mouse model. WSP can promote osteoblast-mediated bone formation and inhibit osteoclast-mediated bone resorption, ultimately ameliorating PMOP. This effect may be associated with the ability of WSP to reduce the absolute abundance of harmful intestinal microbiota such as Desulfovibrionales, Thermodesulfobacteriota, Helicobacteraceae, and Campylobacteria, thereby attenuating the inflammatory response induced by LPS. These findings have significant implications for the potential use of WSP in the treatment of PMOP.