Implication of xanthine oxidase in muscle oxidative stress in COPD patients.

OBJECTIVE: The aim of this study was to determine the implication of xanthine oxidase (XO) in the exercise-induced muscle oxidative stress and muscle dysfunction of these patients. METHODS: A randomized, crossover and double-blind study was conducted in nine severe COPD patients, who performed a localized quadriceps endurance test after oral treatment with allopurinol, a XO inhibitor or placebo. Redox status was studied in arterial and venous femoral blood before and after the endurance test. RESULTS: In placebo condition, muscle exercise resulted in a significant increase in AOPP and isoprostanes, with a significant increase in the venoarterial difference (v-a) in isoprostanes after exercise as compared with before (p<0.05). In contrast, allopurinol treatment prevented the elevation in AOPP levels and v-a isoprostanes after exercise. However, no significant improvement in quadriceps muscle endurance was observed, but allopurinol treatment seemed to preserve muscle strength properties. CONCLUSION: This study demonstrates that XO is implicated in the exercise-induced muscle oxidative stress of COPD patients. Allopurinol administration seemed to improve only some muscle properties. Therefore other sources of muscle oxidative stress should be implicated in muscle dysfunction observed in these patients.

Does prior training affect acute O2 supply responses during exercise in Desaturator COPD patients?

BACKGROUND: This study investigated the effects of a prior individualized training program (TP) on the response to acute oxygen supply during exercise in chronic obstructive pulmonary disease (COPD) patients showing exercise-induced desaturation. METHODS: Twenty-two COPD patients (mean [SD] FEV1 = 52.1 [3]% predicted) who desaturated on exercise participated in a TP. Exercise tolerance while breathing compressed air or oxygen was assessed using a walking test (WT) before and after TP. Oxygen flow was individualized. RESULTS: Before TP, acute oxygen supply improved mean exercise tolerance. But this response was heterogeneous as only 8 patients increased their walking distance with oxygen. TP improved exercise tolerance in the entire population. However, a greater affect of oxygen administration during exercise was not observed after TP. The response to oxygen again showed great disparity as only 6 patients increased their walking distance with oxygen after TP. CONCLUSION: The response to oxygen supply during exercise varied among COPD patients. Moreover, despite the clinical benefits of TP, no cumulative effect of TP and oxygen supply was observed during exercise performance.