Normal adaptations to exercise despite protection against oxidative stress

Area of Science:

• Exercise Physiology
• Nutritional Biochemistry
• Skeletal Muscle Adaptations

Background:

• Previous studies suggested antioxidant vitamins C and E inhibit exercise-induced mitochondrial biogenesis and GLUT4 expression.
• Reevaluation needed to confirm these effects on skeletal muscle adaptive responses.

Purpose of the Study:

• To investigate the impact of high-dose antioxidant vitamin C and E supplementation on exercise-induced adaptations in rat skeletal muscle.
• To determine if antioxidants affect mitochondrial biogenesis, GLUT4 expression, and insulin sensitivity following endurance exercise.

Main Methods:

• Rats received daily high doses of vitamins C and E (750 and 150 mg/kg body weight, respectively) over short-term (9 days) and long-term (8 weeks) periods.
• Exercise (swimming) was performed during the final 3 days of both study durations.
• Adaptive responses, including plasma TBARs, GLUT4 expression, mitochondrial enzyme activity, and superoxide dismutase levels, were assessed post-exercise.

Main Results:

• Antioxidant supplementation demonstrated a protective effect against exercise-induced oxidative stress (elevated plasma TBARs in controls, not in supplemented rats).
• Significant increases in insulin-stimulated glucose transport, GLUT4 expression, and mitochondrial marker enzymes were observed in epitrochlearis muscles of both control and antioxidant groups.
• No significant differences were found in the magnitude of these adaptive responses between control and antioxidant-supplemented rats.

Conclusions:

• High-dose antioxidant vitamins C and E do not impede the adaptive responses of skeletal muscle mitochondria, GLUT4 expression, or insulin action to endurance exercise.
• Antioxidant supplementation did not alter basal levels of these proteins in sedentary rats.
• These findings challenge previous reports suggesting that antioxidants interfere with exercise adaptations.