Fuzhuan Brick Tea Polysaccharide Improved Ulcerative Colitis in Association with Gut Microbiota-Derived Tryptophan Metabolism

Fuzhuanbrick tea (FBT) has attracted wide attention because of its substantial nutritional value. This article first studied the protective mechanism of FBT polysaccharide (FBTP) on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) by 16S rDNA amplicon sequencing technology and metabonomics. It was demonstrated that the administration of FBTP by oral gavage (100, 200, and 400 mg/kg·bw) could decrease the disease activity index (DAI), prevent colon shortening, and alleviate colon tissue damage and inflammation in mice with UC. Interestingly, FBTP relieved the intestinal microbiota disorder caused by UC and contributed to the proliferation of beneficial microbiota, such as Lactobacillus and Akkermansia, followed by a significant increase in the levels of short-chain fatty acids (SCFAs). Furthermore, FBTP dramatically altered tryptophan metabolism and elevated the fecal contents of indole-3-acetaldehyde (IAld) and indole-3-acetic acid (IAA). It was also found that FBTP significantly increased the colonic expressions of aromatic hydrocarbon receptors (AhR) and interleukin-22 (IL-22) and further promoted the expressions of intestinal tight junction (TJ) proteins ZO-1 and occludin in the colitis mice. Cumulatively, these findings suggest that FBTP can relieve UC by regulating intestinal flora disorders, promoting microbial metabolism, and repairing the intestinal barrier.