Investigating the Regulatory Mechanism of Butyrate on Glucose Metabolism in Diabetic Mice via the TLR5–Gut Microbiota Pathway

Background： Type 2 diabetes mellitus（T2DM）is associated with gut microbiota dysbiosis and chronic low-grade inflammation. Sodium butyrate（NaB）has metabolic and immunomodulatory effects, but its relationships with the gut microbiota（GM）, short-chain fatty acids（SCFAs）, and Toll-like receptor 5(TLR5) in type 2 diabetes remain unclear. This study investigated the effects of sodium butyrate on glucose metabolism and systemic inflammation and explored its associations with the gut microbiota, short-chain fatty acids, and intestinal TLR5. Methods： Eighteen male C57BL/6J mice were randomly assigned to Control, type 2 diabetes mellitus, and type 2 diabetes mellitus plus sodium butyrate groups （n = 6 per group）. Type 2 diabetes was induced by a high-fat diet combined with streptozotocin, followed by daily sodium butyrate gavage for 16 weeks. Glucose metabolism, serum lipopolysaccharide, and inflammatory cytokines were assessed. Gut microbiota composition was analyzed by 16S ribosomal RNA gene sequencing, and intestinal short-chain fatty acids were quantified by gas chromatography–mass spectrometry. Colonic TLR5 expression was evaluated by quantitative real-time polymerase chain reaction and immunofluorescence. Group differences were analyzed using analysis of variance, longitudinal data using repeated-measures analysis, and associations using Spearman correlation analysis. Results： Sodium butyrate significantly improved glucose metabolic abnormalities and systemic low-grade inflammation in diabetic mice. It partially reshaped diabetes-associated gut microbiota dysbiosis, with decreased Helicobacter and Mucispirillum and increased Bacteroides, Lachnospiraceae_NK4A136_group, and Alistipes. These changes were accompanied by alterations in the intestinal short-chain fatty acid profile, particularly isobutyric acid and valeric acids. Colonic TLR5 expression was increased in diabetic mice and further enhanced by sodium butyrate treatment. Several differential bacterial genera and short-chain fatty acids were significantly correlated with TLR5, lipopolysaccharide, and inflammatory cytokines. Conclusions： Sodium butyrate alleviated glucose metabolic abnormalities and systemic low-grade inflammation in type 2 diabetic mice, accompanied by gut microbiota remodeling, altered short-chain fatty acid profiles, and increased colonic TLR5 expression. These findings suggest that coordinated changes in the gut microbiota–metabolite–immune axis may contribute to the metabolic and inflammatory effects of sodium butyrate.