Moreover, individuals with COPD show depletion of type I muscle fibers (aerobic) and a greater proportion of type IIx fibers, with consequent reduction in the number of mitochondria and oxidative enzymes and lower expression of peroxisome proliferator-activated receptors (PPAR-α) and PGC-1α, molecular markers that are related to mitochondrial biogenesis and higher activation of oxidative metabolism [24]. The gene discussed is PPARGC1A; the disease is chronic obstructive pulmonary disease.