Effects of physical activity and age on mitochondrial function

Abstract

It has been proposed that ageing results from the accumulation of mitochondrial DNA mutations with age which interfere with respiratory chain ATP production. Insufficient ATP production impairs cell function, and tissue dysfunction ensues, leading to morbidity, decline and eventually death. Supporting this theory, mitochondrial DNA mutations accumulate with age and respiratory chain function declines dramatically in human skeletal muscle. However, the extent of decline in respiratory chain function is greater (50%) than anticipated from the low levels of mitochondrial DNA mutations (< 1%) observed in aged muscle. We hypothesized that an age-related reduction in physical activity could be an important factor in this decline and thus studied the influence of chronological age on muscle mitochondria in subjects matched for levels of physical activity. In this carefully selected group, there was little correlation between oxidative metabolism and age. However, several parameters of respiratory chain function did correlate with markers of physical activity (activity score and handgrip strength). Our results suggest that reduced physical activity is a major contribution to the decline in mitochondrial oxidations during ageing. Physical activity ameliorates and may even mask mitochondrial 'ageing' in muscle.

Muscle strength mediates the relationship between mitochondrial energetics and walking performance

“…Physical exercise is the only intervention thus far that has been shown to significantly improve muscle strength in older individuals (Latham et al ., 2004). In addition, there is literature support for the positive role of resistance exercise and elevated levels of aerobic physical activity on mitochondrial content and function in the elderly (McCully et al ., 1993; Brierley et al ., 1996; Jubrias et al ., 2001), presenting a coherent picture with our current results. Together, these studies provide strong support for exploration of such interventions as an important prescriptive step in retaining functional mobility and independence with aging.…”

Is defective electron transport at the hub of aging?

“…(1989). Importantly, the effect of aging became much less significant once confounding variables such as exercise (Berthon et al ., 1995;Brierly et al ., 1996) and smoking (Smith et al ., 1993) were taken into account in a multivariate statistical analysis. Exercise increases the volume density of mitochondria in young skeletal muscle, less so in old muscle, and shifts substrate metabolism to a higher reliance on fatty acids, which yield more ATP/mole.…”

Mitochondrial Biogenesis in Skeletal Muscle: Exercise and Aging

“…Indeed, some of the age-associated alterations found in mitochondrial activity can be the result of a reduction in the level of voluntary physical activity as individuals age (31). In this regard, it is notable that the adaptation to exercise is not limited to young individuals, because older athletes can increase the activity of mitochondrial oxidative enzymes as a result of training (72).…”