Effect of physical exercise on the ultrastructural features of skeletal muscle mitochondria in old mice.

Sarcopenia is an age-related decline of muscle mass, strength and quality which represents a potent risk factor for frailty, loss of independence and physical disability in elderly. The mechanisms leading to sarcopenia are still largely unknown and no specific therapy is presently available to counteract its onset or progress. Several studies have stressed the importance of physical exercise as an effective approach to prevent/limit the sarcopenic process. In the present work we have investigated at transmission electron microscopy the effects of treadmill running on the mitochondrial structure in aged skeletal muscle by comparing exercised versus sedentary old (28 months) mice, and using adult (12 months) individuals as control. Our observations demonstrated that ageing induces an accumulation of mitochondria characterised by larger size and longer cristae than in adulthood, and by a frequent association with lipid droplets. The mitochondrial alterations are partially reversed in old mice after treadmill running, thus providing further evidence that an adapted physical exercise may represent a suitable non-pharmacologic approach to limit the negative effects of ageing on the skeletal muscle, even when applied at late age.