Effects of exercise on mitochondrial content and function in aging human skeletal muscle

Skeletal muscle mitochondria are implicated with age-related loss of function and insulin resistance. We examined the effects of exercise on skeletal muscle mitochondria in older (age = 67.3 [+ or -] 0.6 years) men (n = 5) and women (n = 3). Similar increases in (p < .01) cardiolipin (88.2 [+ or -] 9.0 to 130.6 [+ or -] 7.5 [micro]g/mU creatine kinase activity [CK]) and the total mitochondrial DNA (1264 [+ or -] 170 to 1895 [+ or -] 273 copies per diploid of nuclear genome) reflected increased mitochondria content. Succinate oxidase activity, complexes 2-4 of the electron transport chain (ETC), increased from 0.13 [+ or -] 0.02 to 0.20 [+ or -] 0.02 U/mU CK (p < .01). This improvement was more pronounced (p < .05) in subsarcolemmal (127 [+ or -] 48%) compared to intermyofibrillar (56 [+ or -] 12%) mitochondria. NADH oxidase activity, representing total ETC activity, increased from 0.51 [+ or -] 0.09 to 1.00 [+ or -] 0.09 U/mU CK (p < .01) In conclusion, exercise enhances mitochondria ETC activity in older human skeletal muscle, particularly in subsarcolemmal mitochondria, which is likely related to the concomitant increases in mitochondrial biogenesis.