Endothelial dysfunction is an early step to the progression of cardiovascular diseases in diabetes. Apart from their anti-diabetic action, DPP-4 (dipeptidyl peptidase-4) inhibitors also reduce cardiovascular events in diabetic patients. However, the underlying mechanism of the beneficial effect of DPP-4 inhibitor on endothelial function is still obscure. In this study, we intervened type 1 or 2 diabetic model mice with vildagliptin for 4 weeks and measured the vascular reactivity. We found that vildagliptin improved endothelium-dependent vasodilation in diabetic mice independent of GLP-1 (glucagonlike peptide-1), but this effect was blocked by a SIRT1 (Sirtuin 1) inhibitor, Ex527. Mechanistically, vildagliptin-activated Transient Receptor Potential Channel Vanilloid 4 (TRPV4) to promote extracellular calcium uptake in endothelial cells, which activated AMPK (AMP-activated protein kinase)/SIRT1 pathway to counteract hyperglycemia-induced endothelial reactive oxygen species generation and senescence. Vildagliptin directly binds to TRPV4 by forming a hydrogen bond, which is critical to vildagliptin-evoked endothelial calcium intake. Knockout or inhibition of TRPV4 erased the beneficial role of vildagliptin. In addition, activation of SIRT1 by SRT1720 improved endothelial function independent of TRPV4 and reduced TRPV4 transcription to maintain an appropriate calcium level. In summary, our findings prove that vildagliptin protects against hyperglycemia-induced endothelial dysfunction by activating TRPV4-meditaed Ca2+ uptake, which helps to re-understand the mechanism of DPP-4 inhibitors and expand the therapeutic scope.
Keywords: diabetes complications; sirtuin 1; transient receptor potential channels; vascular endothelial cells; vildagliptin.