DPP4 and type 2 diabetes mellitus: T2D — type 2 diabetes; BMI — body mass index; HbA1c — glycated haemoglobin; DPP4i — dipeptidyl peptidase IV inhibitors; SGLT2i — sodium-glucose cotransporter 2 inhibitors; GLP-1RAs — glucagon-like peptide-1 receptor agonists; SU — sulphonylurea drugs.