Temporal effects of training on skeletal muscle angiogenic responses to acute exercise

Abstract

Vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)‐2 and MMP‐9 are important in extracellular matrix remodeling and skeletal muscle angiogenesis in response to exercise. We evaluated protein expression of VEGF, MMP‐2 and MMP‐9 in mouse gastrocnemius muscle following 0, 3, 5, 7, 14, and 28 (d)ays of voluntary wheel running (n=12 per group). Protein expression was evaluated at either rest (basal, n=6) or after a single 1‐hour treadmill running bout (25 m/min at 10‐degrees, n=6) in each group. Compared to untrained controls, basal VEGF levels were significantly decreased by 36% at 3d, increased by 31% at 7d, and again reduced by 48% at 28d (p<0.05 respectively). Basal MMP‐2 protein expression was only reduced at 3d (36%, p<0.05), while MMP‐9 protein levels were decreased by 43% at 5d, 43% at 7d, and 34% at 14d (p<0.05 respectively). Basal MMP‐9 was not significantly altered at either 3d or 28d. VEGF response to acute exercise was increased in by 61% in control (p<0.05), 33% at 3d (p<0.05), and, to a lesser extent, in 5d (29%, p=0.08) trained mice, but absent after 7d of training. Neither MMP‐2 nor MMP‐9 showed a significant protein response to acute exercise. These data show that the VEGF protein response to acute exercise is blunted after 7 days of training, at a time point when training‐induced capillary adaptation is expected.