DPP4 and endothelial dysfunction: Furthermore, glucagon-like peptide-1 (GLP-1), an incretin, induces an endothelial-dependent relaxation via NO-dependent action [15] and improves endothelial dysfunction in patients with type 2 diabetes [16], and sitagliptin, a DPP-4 inhibitor, protects endothelial function in spontaneously hypertensive rats through a GLP-1-dependent mechanism [17].