Combined 16S rRNA gene sequencing and metabolomics to investigate the protective effects of Wu-tou decoction on rheumatoid arthritis in rats

Wu-tou decoction (WTD) is a traditional Chinese medicine (TCM) formula which has been used for treating rheumatoid arthritis (RA) for a thousand years. However, the underlying mechanism of WTD in treating RA is still unclear. In recent years, more and more attention has been paid to the role of gut microbiota and microbiotaderived metabolites in the treatment of RA. Hence, this study aims to investigate the roles of microbiota and microbial metabolites in the treatment of RA with WTD. Firstly, the therapeutic effects of WTD on adjuvantinduced arthritis (AIA) rats were evaluated. Then, the 16S rRNA sequencing analysis was used to clarify the changes of the intestinal microbiota and obtain the key microbiota affected by WTD. The important microbial metabolites were quantitated to explore the metabolic characteristics of WTD against RA by targeted metabolomics method. Finally, correlation analysis was performed to investigate the functional correlation among the gut microbiota, metabolites and RA-related serum indexes. The results indicated that WTD could relieve arthritis and reverse gut microbiota dysbiosis. The variation of short-chain fatty acids, bile acids, tryptophan metabolites and amino acids, which are important microbial metabolites, were reversed by WTD intervention. The correlation studies proved that WTD could regulate inflammation and intestinal barrier function partially by modulating Bacteroides, Prevotella, Akkermansia and their associated acetic acid, butyric acid, cholic acid and indole propionic acid. The anti-RA effects of WTD were partially mediated by gut microbiota and microbial metabolites. This study provides a new insight for treating RA and highlights the importance of gut microbiota in the treatment of diseases.