Skeletal muscle mitochondrial dysfunction during chronic obstructive pulmonary disease: central actor and therapeutic target.

Muscle dysfunction is a common complication and an important prognostic factor in chronic obstructive pulmonary disease (COPD). As therapeutic strategies are still needed to treat this complication, gaining more insight into the process that leads to skeletal muscle decline in COPD appears to be an important issue. This review focuses on mitochondrial involvement in limb skeletal muscle alterations (decreased muscle mass, strength, endurance and power and increased fatigue) in COPD. Mitochondria are the main source of energy for the cells; they are involved in production of reactive oxygen species and activate an important pathway that leads to apoptosis. In COPD patients, skeletal muscles are characterized by decreased mitochondrial density and biogenesis, impaired activity and coupling of mitochondrial respiratory chain complexes, increased mitochondrial production of reactive oxygen species and, possibly, increased apoptosis. Of particular interest, a sedentary lifestyle, hypoxia, hypercapnia, tobacco smoking, corticosteroid therapy and, possibly, inflammation participate in this mitochondrial dysfunction, which is accessible to conventional therapies, such as exercise and tobacco cessation, as well as, potentially, to more innovative approaches, such as antioxidant treatment and supplementation with polyunsaturated fatty acids.