ABSTRACT
β-Glucans, a group of complex non-digestible polysaccharides, are considered to have beneficial health effects due to their immune modulatory properties and are being widely used as dietary supplements. Prebiotic properties of these polysaccharides in promoting intestinal health are also being recognized. Therefore, we assessed the impact of oral administration of high-pure yeast β-glucan (YBG) on the susceptibility to colitis, gut immune function, composition of gut microbiota and short-chain fatty acid (SCFA) production. We show that prolonged pre-treatment with YBG diminishes the severity of dextran sulfate sodium (DSS)-induced colitis in mice. YBG consumption, compared to untreated controls, results in increased regulatory T cell (Treg) frequencies in the gut mucosa, a shift in the abundance of gut microbiota towards polysaccharide-fermenting bacterial phyla, and higher production of SCFA. Depletion of gut microbiota in YBG-fed mice using broad spectrum antibiotics not only eliminated SCFA production and increased Treg frequencies, but also profoundly enhanced the pro-inflammatory response in the colon and susceptibility to colitis. Overall, our study demonstrates that oral consumption of high-pure BG promotes a healthy gut, immune regulation, minimizes susceptibility to colitis in a microbiota- and SCFA-dependent manner. On the contrary, YBG-consumption when the gut mucosa and microbiota are compromised can reverse this protection and increase the susceptibility to gut inflammation and disease.