DPP4 and type 2 diabetes mellitus: Clinical studies of the effects of DPP-4 inhibitor treatment on vascular endothelial function, usually involving small numbers of patients, have yielded inconsistent results [19, 20] and the DPP-4 inhibitor sitagliptin did not improve echocardiographic parameters in patients with T2D and left ventricular diastolic dysfunction [21].