PGC-1α mediates exercise-induced skeletal muscle VEGF expression in mice
The aim of the present study was to test the hypothesis that PGC-1α is required for exercise-induced VEGF expression in both young and old mice and that AMPK activation leads to increased VEGF expression through a PGC-1α-dependent mechanism. Whole body PGC-1α knockout (KO) and littermate wild-type (WT) mice were submitted to either 1) 5 wk of exercise training, 2) lifelong (from 2 to 13 mo of age) exercise training in activity wheel, 3) a single exercise bout, or 4) 4 wk of daily subcutaneous AICAR or saline injections. In skeletal muscle of PGC-1α KO mice, VEGF protein expression was ∼60–80% lower and the capillary-to-fiber ratio ∼20% lower than in WT. Basal VEGF mRNA expression was similar in WT and PGC-1α KO mice, but acute exercise and AICAR treatment increased the VEGF mRNA content in WT mice only. Exercise training of young mice increased skeletal muscle VEGF protein expression ∼50% in WT mice but with no effect in PGC-1α KO mice. Furthermore, a training-induced prevention of an age-associated decline in VEGF protein content was observed in WT but not in PGC-1α KO muscles. In addition, repeated AICAR treatments increased skeletal muscle VEGF protein expression ∼15% in WT but not in PGC-1α KO mice. This study shows that PGC-1α is essential for exercise-induced upregulation of skeletal muscle VEGF expression and for a training-induced prevention of an age-associated decline in VEGF protein content. Furthermore, the findings suggest an AMPK-mediated regulation of VEGF expression through PGC-1α.