GLP1R and type 2 diabetes mellitus: Since then, new classes of glucose-lowering drugs have been introduced for the treatment of T2D, namely di-peptidyl peptidase-4 inhibitors (DPP-4is), sodium-glucose cotransporter-2 inhibitors (SGLT2is), glucagon-like peptide 1 receptor agonists (GLP-1 RAs) and, since 2022, tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP)/ GLP-1 RA.