DPP4 and type 2 diabetes mellitus: Our recent study reported that the commonly used oral hypoglycemic agent, dipeptidyl peptidase-4 inhibitors (DPP-4i), markedly changed the composition of the gut microbiota and the pattern of metabolites in high-fat diet- (HFD-) fed mice and that the DPP-4i sitagliptin- (Sit-) altered microbiome from type 2 diabetes (T2D) patients improved the glucose intolerance induced by HFD in germ-free mice [9].