Abstract
Patients with chronic obstructive pulmonary disease (COPD) frequently complain of dyspnea on exertion and reduced exercise capacity, which has been attributed to an increase in the work of breathing and in impaired of gas exchange. Although COPD primarily affects the pulmonary system, patients with COPD exhibit significant systemic manifestations of disease progression. These manifestations include weight loss, nutritional abnormalities, skeletal muscle dysfunction (SMD), cardiovascular problems, and psychosocial complications. It has been documented that SMD significantly contributes to a reduced exercise capacity in patients with COPD. Ventilatory and limb muscle in these patients show structural and functional alteration, which are influenced by several factors, including physical inactivity, hypoxia, smoking, aging, corticosteroid, malnutrition, systemic inflammation, oxidative stress, apoptosis, and ubiquitin-proteasome pathway activation. This article summarizes briefly the evidence and the clinical consequences of SMD in patients with COPD. In addition, it reviews contributing factors and therapeutic strategies.
Figures and Tables
Figure 1
The strength of the quadriceps, pectoralis major, and latissimus dorsi muscles in normal subjects and in chronic obstructive pulmonary disease (COPD). The strength of each muscle was significantly reduced in COPD patients compared with normal subjects. Values are mean±SD. *p<0.005. Adapted from Bernard S, LeBlanc P, Whittom F, Carrier G, Jobin J, Belleau R, et al. Peripheral muscle weakness in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1998;158:629-34.
![trd-68-125-g001](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-g001.jpg)
Figure 2
Computed tomography finding of quadriceps muscle found in chronic obstructive pulmonary disease (COPD) patient and in control subject. Adapted from Bernard S, LeBlanc P, Whittom F, Carrier G, Jobin J, Belleau R, et al. Peripheral muscle weakness in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1998;158:629-34.
![trd-68-125-g002](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-g002.jpg)
Figure 3
Fiber-type composition of the vastus lateralis muscle found in chronic obstructive pulmonary disease (COPD) patients and in normal subjects. When it compared with normal subjects, a significant reduction in the proportion of type I fiber with a corresponding increase in the proportion of type IIb fiber was observed in COPD patients. Values are mean±SD. *p<0.0005, †p<0.05. Adapted from Whittom F, Jobin J, Simard PM, Leblanc P, Simard C, Bernard S, et al. Histochemical and morphological characteristics of the vastus lateralis muscle in patients with chronic obstructive pulmonary disease. Med Sci Sports Exerc 1998;30:1467-74.
![trd-68-125-g003](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-g003.jpg)
Figure 4
Proposed mechanisms of skeletal muscle dysfunction in patients with COPD. COPD: chronic obstructive pulmonary disease; UPP: ubiquitin proteasome pathway.
![trd-68-125-g004](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-g004.jpg)
Table 1
Structural and functional changes in COPD, which were shown in vastus lateralis muscle biopsies
![trd-68-125-i001](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-i001.jpg)
Table 2
Difference of structural and biochemical changes between diaphragm and limb muscles in COPD patients
![trd-68-125-i002](/upload/SynapseData/ArticleImage/0003trd/trd-68-125-i002.jpg)
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