IARS1 and type 2 diabetes mellitus: Imidazole propionate, produced by type 2 diabetes-associated bacteria as a metabolite of histidine, is heightened in type 2 diabetes and impairs glucose tolerance and insulin signaling, a process achieved by inhibiting insulin receptor substrate (IRS) in a p38g/p62/mTORC1-dependent manner.218 In a similar vein, the gut microbiome that harbors tyrosine phenol-lyase can catabolize dietary tyrosine into the precursor phenyl sulfate.