GPBAR1 and metabolic disease: Compounds such as oleanolic acid, betulinic acid, ursolic acid, curcumin, 5β-scymnol, nomilin, obacunone, and quinovic acid engage TGR5 via diverse mechanisms and signaling pathways (e.g., cAMP, PKA, PPARγ, and GLP-1 axis), supporting their potential as therapeutic candidates for metabolic diseases.