Extracellular polysaccharides from Sporidiobolus pararoseus alleviates rheumatoid through ameliorating gut barrier function and gut microbiota

Rheumatoid arthritis (RA) is becoming a prevalent autoimmune disease affecting people worldwide, necessitating the exploration of novel therapeutic approaches due to the associated adverse effects of conventional therapeutic drugs. Sporidiobolus pararoseus polysaccharide (SPP) has been shown to exhibit significant immune stimulation and antioxidant activities. In this study, we constructed a mouse model of type II collagen-induced arthritis (CIA) to investigate the effects and potential mechanisms of SPP intervention on RA. Results showed that SPP intervention alleviated the degree of ankle swelling, joint histopathologic changes, joint pathological score and the expression of serum-associated inflammatory mediators (such as IL-1β and IL-6). 16S rRNA sequencing results indicated that SPP intervention significantly remodeled the intestinal microbiota composition. In particular, SPP intervention significantly increased the relative abundance of beneficial bacteria (Parabacteroides, Bacteroides and Rikenellaceae_RC9_gut_group) with the potential to degrade fungal polysaccharides or produce short-chain fatty acids (SCFAs). The production of SCFAs (especially acetic acid, propionic acid and butyric acid) indeed increased significantly. These SCFAs played an important role in maintaining intestinal barrier function and regulating immune homeostasis, which helped reduce inflammatory responses and alleviate the symptoms of RA.