Fourteen composite probiotics alleviate type 2 diabetes through modulating gut microbiota and modifying M1/M2 phenotype macrophage in db/db mice

Dysregulation of intestinal microbiota accelerates the development of type 2 diabetes. Probiotics are potential adjunctive therapy in the treatment of diabetes. This study investigated the anti-diabetic mechanism of 14 composite probiotics. Results showed that treatment with 14 composite probiotics improved intestinal microbiota equilibrium by increasing the population of short-chain fatty acids (SCFAs)-producing bacteria and decreasing the number of harmful bacteria. Further, the probiotics significantly improved blood glucose metabolism by promoting glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) secretion. These effects were ascribed to the activation of GPR43/41, restoration of the pancreatic structure, the elevation of insulin secretion and balancing of blood glucose-related parameters. Additionally, the 14 composite probiotics markedly restored gut barrier function via activating antioxidant enzymes, promoting tight junction protein expression, inhibiting the activity of pro-inflammatory factors and improving the morphology of the colon. Furthermore, the 14 composite probiotics upregulated M2 polarization factors and downregulated M1 polarization factors, possibly through TLRs/MyD88/NF-κB signaling pathway. These results indicate that the 14 composite probiotics can potentially improve diabetes prognosis.