Gut microbiota also produces metabolites such as short-chain fatty acids (SCFAs), bile acids (BAs), trimethylamine N-oxide (TMAO), indole derivatives, and lipopolysaccharides (LPS), which participate in insulin signaling and induce the occurrence of T2DM through mechanisms such as IR, bile acid metabolism, lipid metabolic disorders, and endotoxemia (Gurung et al., 2020; Scheithauer et al., 2020; Zhang Y. et al., 2020; Wu et al., 2023). Here, INS is linked to type 2 diabetes mellitus.