Moderate exercise training induces ROS-related adaptations to skeletal muscles

Aim of the present work was the evaluation of the effects of moderate exercise training on two skeletal muscles differing for fibre-type composition, Tibialis Anterior (TA) and Soleus (SOL). Fibre adaptations, including their metabolic shift and mechanisms underlying proliferation and differentiation, oxidative stress markers, anti-oxidant and cytoprotective molecules, activity of Ca2+-handling molecules were examined. Six male 2-month-old rats trained on a treadmill for 1 h/day, 3 days/week, 14 weeks, reaching 30 m/min at the end of training. Six age-matched sedentary rats served as controls. Rats were sacrificed 24 h after the last training session. Muscle Regulatory Factors increased in both muscles, activating satellite cell proliferation, which led to moderate hypertrophy in SOL and to moderate hyperplasia in TA, where the upregulation of desmin and TNFR2 expression suggests that myotube formation by proliferating myoblasts is somehow delayed. Changes leading to a more oxidative metabolism together with the upregulation of a number of antioxidant enzymes occurred in TA. HSP70i protein was upregulated in both SOL and TA, while oxidative stress markers increased in SOL alone. The status of ionic channels and pumps was preserved. We suggest that the increase in ROS, known to be associated with exercise, underlies most observed results.