Impairment in endothelial bioenergetics contributes to diabetes‐induced vascular dysfunction

Abstract

Diabetes, whether insulin‐dependent or independent is a major cause of endothelial dysfunction and a leading risk factor for cardiovascular disease. While compelling evidence indicates that endothelial dysfunction is a precursor and contributor to cardiovascular disease, the etiology of diabetes‐induced endothelial dysfunction remains ill‐defined. Recently alteration in endothelial cell bioenergetics has emerged as a new contributor to vascular diseases. However, whether alterations in endothelial glycolysis, the main endothelial cell bioenergetic pathway contributes to endothelial dysfunction is unknown. Herein, we tested the hypothesis that diabetes‐associated endothelial dysfunction involved increases in endothelial cells glycolysis and upregulation of its primary regulator, 6‐phosphofructo‐2‐kinase/fructose‐2, 6‐bisphosphatase 3 (PFKFB3). Measurement of glycolytic activity via Seahorse analyzer in primary human aortic endothelial cells (HAEC) from control and diabetic patients revealed a significant increase in basal glycolysis in diabetic subjects (p<0.05). We also employed Akita mice, a mouse model of type 1 diabetes. Male Akita mice showed a diabetic phenotype with 3‐folds increase in blood glucose. Seahorse analysis in intact aortic explants revealed a 1.7‐fold increase in basal glycolysis and a 1.3‐fold increase in maximal glycolysis in Akita mice (P<0.05). The increase in glycolysis was endothelial‐derived as aortic denudation significantly decreased glycolysis in Akita mice and abolished the difference between groups. No significant difference in mitochondrial function was depicted in the mito‐stress test between Akita and WT aortic explants (p>0.05). Additionally, endothelial cells extracted from aortas of Akita mice exhibited a 2‐fold increase in PFKFB3 mRNA expression(P<0.05). Interestingly, inhibition of PFKFB3 using 3PO (20μM) restored endothelial function in Akita mice. Similarly, Non‐obese diabetic females (NOD), a model for type‐1 diabetes, showed 4‐fold increases in PFKFB3 mRNA expression in aortic endothelial cells and impaired EDR which was restored with 3PO (p<0.05). To further evaluate the role of PFKFB3 in vascular endothelial function we overexpressed PFKFB3 in WT aortas with adenovirus (Ad‐PFKFB3), and reported impaired aorta EDR(P<0.05). Transduction of HAEC with Ad‐PFKFB3 showed a significant increase in ROS producing enzyme (NOX1). Also, inhibition of NOX1 using the selective inhibitor GKT771 restored EDR in Akita and Ad‐PFKFB3‐transduced WT aortas. In Conclusion, our data identified for the first time a role for endothelial glycolysis in the control of vascular relaxation and showed a crucial role of PFKFB3‐mediated endothelial glycolysis in vascular endothelial dysfunction associated with Type‐1 diabetes in males and females. The underlying mechanism potentially involves NOX1 as a downstream target for PFKFB3. Thus, Inhibitors of PFKFB3 could be a potential therapeutic target for diabetes‐induced vascular endothelial dysfunction.