Knee-extensor Exercise and Skeletal Muscle Citrate Synthase Activity in COPD Patients

Abstract

0254 Measured citrate synthase activity (CSA) in skeletal muscle increases after an acute bout of exercise in young healthy adults. PURPOSE: To evaluate CSA levels in COPD patients after acute single-leg knee-extensor exercise (KE) and chronic KE training. METHODS: Muscle biopsies from 13 COPD patients (65 +/− 3yr; FEV1 = 0.95 +/− 0.08L) and 7 age (64 +/− 3yr) and activity level-matched controls were assessed for CSA before and after acute KE. A subgroup of COPD patients (n = 5) completed an 8-week KE training protocol and underwent a second set of biopsy protocol. RESULTS: Resting CSA in all COPD patients was not different from controls (10.64 +/− 1.12 vs. 12.66 +/− 1.50 μmol/min/g). As anticipated, the controls exhibited a 19 +/− 6% increase in CSA after acute KE. In contrast, the untrained COPD patients significantly decreased CSA by 14 +/− 10.3% after acute KE. Post training COPD patients performed acute KE as in the pre-training study, but no longer revealed a significant fall in CSA (10 +/− 7.5%). COPD patients revealed significant plasticity in response to chronic KE training, resulting in increasing CSA from 8.16 +/− 1.7 to 12.69 +/− 2.2. CONCLUSION: Unlike healthy controls, which increased CSA after acute KE, the COPD patients actually decreased CSA. Exercise training improves CSA in COPD and tends to attenuate the fall in CSA because of acute exercise. Although in healthy subjects the exact mechanism by which exercise increases CSA is unknown, these data support the concept that subtle abnormalities in skeletal muscle metabolism accompany COPD. Supported by NIH Grants 1-R25-GM60202 and HL 17731.