Butyrate inhibits interleukin-17 and generates Tregs to ameliorate colorectal colitis in rats

Background: Butyrate is an energy source for colonocytes that is formed by bacterial fermentation of dietary fiber in the colon and that exerts broad anti-inflammatory activities. Although the administration of butyrate improves homeostasis in patients and ameliorates IBD (Inflammatory Bowel Disease)-related lesions and symptoms, the anti-inflammatory mechanisms of butyrate still remain unclear. To explore the impact of butyrate on Treg (Regulatory T cell)/Th17 (T helper 17 cell) differentiation and colitis in rats. Methods: The effect of butyrate on the expression of markers related to both Tregs and Th17 cells were determined in human monocytes as well as a rat model of colitis induced by 2,4,6-trinitrobenzene sulfonic acid. Rats were treated with butyrate in vivo, whereas the rat splenocytes and human monocytes were treated in vitro. Results: We found that butyrate administration increased peripheral blood Treg cell levels as well as plasma levels of anti-Th17 cytokines (IL-10 and IL-12). Butyrate administration further suppressed IL-17 levels in both plasma and colonic mucosa, and ameliorated colonic colitis lesions in rats. This promotion of Treg activity and inhibition of IL-17 release was also observed in human venous monocytes and rat splenocytes in vitro. Conclusions: Our results suggest that butyrate plays a key role in regulating the Treg/Th17 balance and ultimately protects the colon mucosa against the development of IBD.