Dipeptidyl dipeptidase-4 inhibitor, MK-0626, promotes bone marrow-derived endothelial progenitor cell bioactivities for vascular regeneration in diet-induced obese mice

Metabolic syndrome (MS), overlapping type 2 diabetes, hyperlipidemia, and/or hypertension, based on high-fat diet, poses risk for cardiovascular disease. A critical feature associated with such risk is the functional impairment of endothelial progenitor cells (EPCs). Dipeptidyl dipeptidase-4 inhibitors are known not only to inhibit degradation of incretins to control blood glucose levels, but also to improve EPC bioactivity and induce anti-inflammatory effects in tissues. In the present study, we investigated the effects of such an inhibitor, MK-06266, in ischemia model of MS using diet-induced obese (DIO) mice. EPC bioactivity was examined in MK-0626-administered DIO mice and non-treated control group, using an EPC colony-forming assay and bone marrow cKit+ Sca-1+ lineage-cells, and peripheral blood-mononuclear cells. Our results showed that, in vitro, the effect of MK-0626 treatment on EPC bioactivities and differentiation was superior in comparison with non-treatment. Further, in vivo hindlimb ischemia model experiment indicated that microvascular density and pericyte-recruited arteriole number were increased in MK-0626-administered group, but not control group. Lineage profiling of isolated cells from ischemic tissues disclosed that MK-0626 administration has an inhibitory effect on unproductive inflammation. This occurred via a decrease in the influx of total blood cells and pro-inflammatory cells such as neutrophils, total macrophages, M1, total T-cells, cytotoxic T-cells, and B-cells, with a concomitant increase in number of regeneration-associated cells, such as M2/M ratio and Treg/T-helper. Laser Doppler analysis revealed that at day 14 after ischemic injury, blood perfusion in hindlimb was grater in DIO mice treated with MK-0626, but not in control. In conclusion, the dipeptidyl dipeptidase-4 inhibitor has a positive effect on EPC differentiation in MS model of DIO mice. Following ischemic injury, DPP-4 i sharply reduces recruitment of pro-inflammatory cells into ischemic tissue, and triggers regeneration and reparation process. Thus, DPP-4 i is a promising therapeutic agent for MS treatment.