DPP4 and diabetes mellitus: In vivo, treatment with a DPP-4 inhibitor (sitagliptin) can significantly attenuate RVSP, right ventricle and pulmonary vascular remodeling, inflammatory cell infiltration, and EndMT in MCT-, bleomycin- and hypoxia-induced PH rats, and treatment with a GLP-1 antagonist can abolish the beneficial effects of sitagliptin on PH [[100], [101], [102]], which suggests that similar to its action on diabetes, DPP-4 inhibitors can also exert protective effects by inhibiting GLP-1 cleavage.