Perivascular adipose tissue (PVAT)-derived leptin improves aortic endothelial function via attenuating endothelial glycolysis in a mouse model of lipodystrophy

Endothelial dysfunction, characterized by impaired endothelial-dependent relaxation (EDR), is a hallmark and first step in the chain of events leading to cardiovascular disorders. Several vascular pathologies have been associated with aberrant increases in endothelial glycolysis and 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3) expression/activity, however, whether endothelial glycolysis contributes to EDR regulation remains unknown. Additionally, endothelial dysfunction is present in conditions associated with severe alterations in body fat content including obesity (excess) and lipodystrophy (absence of adipose tissue). However, the exact link between endothelial function and adipose tissue, particularly the one surrounding blood vessels (perivascular adipose tissue, PVAT) remains ill-defined. As leptin, the adipokine highly involved in the regulation of cardiovascular function, has also been shown to modulate cellular bioenergetics in immune and cancer cells, we hypothesized that leptin derived from PVAT controls EDR via endothelial leptin receptor activation and attenuation of PFKFB3-mediated glycolysis. To determine the role of PFKFB3 in endothelial function, we overexpressed PFKFB3 in mouse endothelial cells via adenovirus transduction (Ad-PFKFB3), and reported impaired aorta EDR. Additionally, using seahorse analyzer and glycolysis stress test we found that human aortic endothelial cells (HAEC) transduced with Ad-PFKFB3 showed a significant increase in basal glycolysis (p<0.05) which was blunted by exposure to leptin (10µg/ml, 2h). To determine the role of PVAT-derived leptin in EDR, we used a mouse model of lipodystrophy, with total deficiency in adipose tissue and leptin (Bscl2-/-) characterized by vascular and metabolic dysfunctions as evidenced by impaired EDR and glucose intolerance. We also found that aortas from Bscl2-/- mice exhibited a marked increase in basal and maximum glycolysis measured using seahorse analyzer and glycolysis stress test. This is in line with the PCR data showing increased expression of PFKFB3 mRNA compared to WT mice. Interestingly, inhibition of PFKFB3 using 3 PO or PFK158 (20uM) restored EDR in Bscl2-/- mice. Additionally, we transplanted 25 mg PVAT from WT mice to the abdominal aorta of Bscl2-/-. After 4 weeks, PVAT significantly reduced aortic expression of PFKFB3 and corrected systemic glycemia as well as EDR in Bscl2-/- vs sham (P<0.05). However, leptin receptor blockade (Allo-Aca, 0.05 mg/kg/day) blunted PVAT-mediated restoration of EDR in PVAT-transplanted Bscl2-/- mice. In conclusion, these data demonstrate that PVAT releases a vasodilatory factor, potentially, leptin that acts via activation of endothelial leptin receptor to improve endothelial function via a mechanism that involves regulation of PFKFB3-mediated endothelial glycolysis.