Background: COPD is a debilitating disease that affects patients’ daily lives. One’s daily physical activity (DPA) decreases due to multifactorial causes, and this decrease is correlated with a poor prognosis in COPD patients. Muscle wasting may at least be partly due to increased activity of the ubiquitin proteasome pathway and apoptosis. Methods: This study investigated the relationships among DPA, circulating proteasome activity, and protein carbonyl in COPD patients and healthy subjects (HSs). This study included 57 participants (42 patients and 15 healthy subjects). Ambulatory DPA was measured using actigraphy, and oxygen saturation was measured with a pulse oximeter. Results: COPD patients had lower DPA, lower 6 min walking distance (6MWD), lower delta saturation pulse oxygenation (SpO2) during the 6MWT, and lower delta SpO2 during DPA than HSs. COPD patients had higher proteasome activity and protein carbonyl than HSs. Circulating proteasome activity was significantly negatively correlated with DPA (r=-0.568, P<0.05) in COPD patients, whereas delta SpO2 during the 6MWT was significantly positively correlated with proteasome activity (r=0.685, P<0.05) in HSs. Protein carbonyl was significantly negatively correlated with the body mass index (r=-0.318, P<0.05), mid-arm circumference (r=0.350, P<0.05), calf circumference (r=0.322, P<0.05), forced expiratory volume in the first second (r=-0.441, P<0.01), and 6MWD (r=-0.313, P<0.05) in COPD patients. Our results showed no significant difference in inflammatory markers (interleukin-6 and tumor necrosis factor-α) or ubiquitin between the two groups. Conclusion: COPD patients had lower DPA levels and higher circulating proteasome activity than HSs, and a negative correlation of DPA with circulating proteasome activity.
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