Exercise-induced quadriceps oxidative stress and peripheral muscle dysfunction in COPD patients

Exercise-induced muscle oxidative stress may be involved in the myopathy associated with chronic obstructive pulmonary disease (COPD). This study was designed to look at whether local exercise induces muscle oxidative stress and whether this may be associated with the reduced muscle endurance in COPD. Quadriceps endurance was measured in 12 patients with COPD (FEV1 = 0.96 [[plusmn]] 0.14 SEM) and 10 healthy sedentary subjects by knee extensions of the dominant leg. Biopsies of the vastus lateralis were obtained before and 48 hours after exercise. Muscle oxidative stress was measured by lipid peroxidation (TBARs) and oxidized proteins. Muscle antioxidant was evaluated by peroxidase glutathion activity (GPX). Quadriceps endurance was significantly reduced in patients with COPD (p < 0.01). Forty-eight hours post-exercise, only COPD patients had a significant increase in muscle TBARs (p < 0.05) and oxidized proteins (p < 0.05) while increased GPX activity was only observed in controls (p < 0.05). Both increases in muscle TBARs and oxidized proteins were significantly and inversely correlated with quadriceps endurance in COPD (p < 0.05). Local exercise induced muscle oxidative stress in COPD patients while it failed to raise antioxidant activity. In these individuals, muscle oxidative stress was associated with reduced quadriceps endurance. Word count: 200 words