Training improves the oxidative phenotype muscle during the transition from cardiac hypertrophy to heart failure without altering MyoD and myogenin

The purpose of this study was to investigate the effects of Physical Training (PT) on phenotypic features (fiber-type content) and myogenic regulatory factors (Myod and myogenin) in rat skeletal muscle during the transition from cardiac hypertrophy to heart failure (HF). We employed the model of ascending aortic stenosis (AS) to induce HF in male Wistar rats. Sham-operated animals were used as age-matched controls. At 18 wk after surgery, rats with ventricular dysfunction were randomized into 4 groups: Sham-operated untrained (Sham-U; n = 8), Sham-operated trained (Sham-T; n = 6), aortic stenosis untrained (AS-U; n = 6) and aortic stenosis trained (AS-T; n = 8). The AS-T and Sham-T groups were submitted to a 10-wk aerobic PT program, while the AS-U and Sham-U groups remained untrained for the same period of time. After the PT program, the groups were euthanized and the soleus muscle collected for phenotypic and molecular analyses. PT promoted type IIa-to-I fiber conversion in the trained groups (Sham-T and AS-T), compared to the untrained groups (Sham-U and AS-U). No significant (P > 0.05) differences were found in Type I or IIa fiber content in the AS-U group compared to the Sham-U group. Additionally, there were no significant (P > 0.05) differences in MRF factors MyoD and myogenin (gene and protein) expression between the groups. Therefore, our results indicate that PT may be a suitable strategy to improve the oxidative phenotype in skeletal muscle during the transition from cardiac hypertrophy to HF, without altering MyoD and myogenin.

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