Endurance training induces fiber type-specific revascularization in hindlimb skeletal muscles of rats with chronic heart failure

OBJECTIVE(S): Previous studies showed that skeletal muscle microcirculation was reduced in chronic heart failure. The aim of this study was to investigate the effects of endurance training on capillary and arteriolar density of fast and slow twitch muscles in rats with chronic heart failure. MATERIALS AND METHODS: Four weeks after surgeries (left anterior descending (LAD) artery occlusion), chronic heart failure rats were divided into 3 groups: Sham (Sham, n=10); Sedentary (Sed, n=10); Exercise training (Ex, n=10). Ex group rats were subjected to endurance training in the form of treadmill running with moderate intensity for 10 weeks. RESULTS: Exercise training significantly increased capillary density and capillary to fiber ratio (P<0.05) in slow twitch muscle, but didn’t change fast twitch muscle capillary density and capillary to fiber ratio. Furthermore, arteriolar density in fast twitch muscle increased remarkably (P<0.05) in response to training, but slow twitch muscle arteriolar density did not change in response to exercise in chronic heart failure rats. HIF-1 increased (P<0.01) but VEGF and FGF-2 mRNA did not change in slow twitch muscle after training. In fast twitch muscle, HIF-1 mRNA increased (P<0.05), and VEGF and angiostatin decreased (P<0.01) significantly after training. CONCLUSION: Endurance training ameliorates fast and slow twitch muscle revascularization non-uniformly in chronic heart failure rats by increasing capillary density in slow twitch muscle and arteriolar density in fast twitch muscle. The difference in revascularization at slow and fast twitch muscles may be induced by the difference in angiogenic and angiostatic gene expression response to endurance training.