Epimedii Folium decoction ameliorates osteoporosis in mice through NLRP3/caspase-1/IL-1β β signalling pathway and gut-bone axis

Aim of the study: This study aimed to determine the effect of Epimedium brevicornu Maxim. (EF) on osteoporosis (OP) and its underlying molecular mechanisms, and to explore the existence of the "Gut-Bone Axis". Material and methods: The impact of EF decoction (EFD) on OP was evaluated using istopathological examination and biochemical assays. Targeted metabolomics was employed to identify key molecules and explore their molecular mechanisms. Alterations in the gut microbiota (GM) were evaluated by 16S rRNA gene sequencing. The role of the GM was clarified using an antibiotic cocktail and faecal microbiota transplantation. Results: EFD significantly increased the weight (14.06%), femur length (4.34%), abdominal fat weight (61.14%), uterine weight (69.86%), and insulin-like growth factor 1 (IGF-1) levels (59.48%), while reducing serum type I collagen cross-linked carboxy-terminal peptide (CTX-I) levels (15.02%) in osteoporotic mice. The mechanism of action may involve the regulation of the NLRP3/cleaved caspase-1/IL-1 beta signalling pathway in improving intestinal tight junction proteins and bone metabolism. Additionally, EFD modulated the abundance of related GM communities, such as Lactobacillus, , Coriobacteriaceae, , bacteria of family S24-7, , Clostridiales, , and Prevotella, , and increased propionate and butyrate levels. Antibiotic-induced dysbiosis of gut bacteria disrupted OP regulation of bone metabolism, which was restored by the recovery of GM. Conclusions: Our study is the first to demonstrate that EFD works in an OP mouse model by utilising GM and butyric acid. Thus, EF shows promise as a potential remedy for OP in the future.