Integrated metabolomics and gut microbiota analysis to explore the protective effects of Gushudan on postmenopausal osteoporosis rats via gut-bone axis.

Postmenopausal osteoporosis (PMOP) was caused by significant deviations in gut microbiota and metabolites. Gushudan (GSD), a small traditional Chinese medicine formula, exerted therapeutic effects including kidney-nourishing and bone-strengthening properties. The therapeutic mechanism of GSD in alleviating kidney-yang deficiency syndrome and secondary osteoporosis was systematically investigated through metabolomics and network pharmacology. However, the mechanisms and impact on gut microbiota through which GSD mitigated PMOP remained to be elucidated. In this study, fecal metabolomics was integrated with gut microbiota analysis to comprehensively investigate modification in intestinal flora and metabolic profiles in PMOP rat models from the gut-bone axis framework. Therefore, the GC-MS-based method integrating non-targeted and targeted metabolomics was established to analyze fecal metabolites. The comprehensive analysis of gut microbial communities was performed using 16S rRNA on fecal samples. In the result, 20 potential biomarkers were successfully identified in the non-targeted metabolomics analysis. Subsequently, 12 metabolites related to amino acid metabolism, energy metabolism and bile acid biosynthesis were quantitatively. Then, ten gut microorganisms with significant changes were discovered through 16S rRNA. Furthermore, alterations in fecal metabolites demonstrated a significant correlation with dysbiosis within the gut microorganisms such as [Ruminococcus]_torques_group, Elusimicrobium, Intestinimonas and Papillibacter. GSD effectively modulated abnormal levels of metabolites such as glycine, lactic acid, succinic acid, cholesterol and deoxycholic acid. Specifically, GSD improved the abundance of [Ruminococcus]_torques_group, Elusimicrobium, Intestinimonas. In conclusion, the gut-bone axis was validated as a novel framework, and gut microbiota modulation was further identified as a promising therapeutic target for the prevention of PMOP.