Examining physiological roles of adipose derived VEGF: Consequences in substrate availability and endurance exercise capacity in adipocyte specific VEGF deficient mice
Reducing vascular endothelial growth factor (VEGF) in adipose tissue alters adipose vascularity and metabolic homeostasis. We hypothesized that this would also affect metabolic responses during exercise-induced stress, and that adipocyte-specific VEGF deficient (adipoVEGF-/-) mice would have impaired endurance capacity. Endurance exercise capacity in adipoVEGF-/- (n=10) and littermate control (n=11) mice was evaluated every 4 weeks between 6 & 24 weeks of age using a submaximal endurance run to exhaustion at 20 m/min, 10-degree incline. Maximal running speed, using incremental increases in speed at 30-second intervals, was tested at 25 weeks of age. Beginning at 6 weeks, and continuing with all time points, endurance run time to exhaustion was 30% lower in adipoVEGF-/- compared to controls (p\u3c0.001). The age-associated rate of decline in endurance capacity was similar in adipoVEGF-/- vs. control mice and there was no difference in maximal running speed between the groups. Following 1 hour of running at 50% maximum running speed, adipoVEGF-/- mice displayed decreased circulating insulin, (p\u3c0.001), glycerol (p\u3c0.05), and a tendency for decreased glucose (p=0.06) compared to controls. These data suggest that deficits in adipose tissue vasculature are mediated by adipose VEGF and that deficiency of VEGF blunts the availability of lipid-derived substrates during endurance exercise and affects insulin secretion and glucose metabolism
