Tryptophan-cholic acid (Trp-CA) is a microbial amino acid-binding bile acid (MABA), serving as an endogenous ligand and agonist for MRGPRE (Mas-related GPCR family member E), thereby inducing GLP-1 secretion. Tryptophan-cholic acid improves glucose tolerance in diabetic mice and may be utilised for studies on type 2 diabetes.