Untargeted metabolomics using mass spectrometry has been used forthe discovery of key disease-associated metabolites.377,378 Koh et al. employed untargeted metabolome analysis toward type 2diabetes and discovered that imidazole propionate was present at higherconcentrations among patients with type 2 diabetes.377 Imidazole propionate is produced from histidine by gutmicrobes and impairs insulin signaling through mTORC1. This evidence concerns the gene INS and type 2 diabetes mellitus.