DPP4 and type 2 diabetes mellitus: SGLT2, sodium-glucose cotransporter-2; SGLT2i, sodium-glucose cotransporter-2 inhibitors; T2DM, type 2 diabetes mellitus; DPP4i, dipeptidyl peptidase-4 inhibitor; HF, heart failure; CVD, cardiovascular disease; CV, cardiovascular; CKD, chronic kidney disease