Natural compounds for the treatment of rheumatoid arthritis based on the 'gut‑joint axis' (Review)

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease whose etiology remains incompletely understood. As the proposal and progress of the 'mucosal origin hypothesis', the role of the 'gut‑joint axis' mechanism in the pathological process of RA is gradually being revealed. Changes in the intestinal microbiota, damage to the mucosal barrier, mucosal immune dysfunction and disorders of microbial‑derived metabolites all regulate the occurrence and development of RA. Natural compounds, bioactive entities isolated from natural sources, have demonstrated distinct therapeutic advantages across a broad spectrum of diseases. The intestine may be the key for these compounds to exert their therapeutic effects on diseases. The present review summarized the 'gut‑joint axis' in RA and the natural compounds that exert therapeutic effects via this pathway. It emphasized that improving intestinal microecology may be a potential treatment method for RA, and natural compounds are expected to become promising treatment strategies for RA in this way. However, there are still numerous problems that need to be urgently solved to complete the clinical transformation of these natural compounds.2.