Figure 1.

Metabolites linking the gut microbiota and T2D. SCFAs regulate host glucose homeostasis in part by stimulating the secretion of PYY and GLP-1 through binding to the receptors on intestinal epithelial cells. Indole derivatives have beneficial effects on insulin sensitivity. Bile acids may promote GLP-1 secretion and improve insulin sensitivity. BCAA, TMAO and ImP impair host glucose metabolism. In addition, increased gut permeability facilitates endotoxemia, whereby LPS released by the death of gram-negative bacteria crosses the epithelial barrier and enters the circulation, inducing inflammation, which impairs insulin sensitivity. SCFA, short-chain fatty acid; PYY, peptide YY; GLP-1, glucagon-like peptide-1; BCAA, branched-chain amino acid; TMAO, trimethylamine-N-oxide; ImP, imidazole propionate; LPS, lipopolysaccharide.