Mitochondria and Ageing

Abstract

Mitochondria are the major sites of oxygen utilisation for energy production in cells. Indeed, all the reactions of the Krebs’ Cycle take place in mitochondria and they produce NADH and succinate, which are then oxidised in the respiratory chain. Experiments dating back to the early part of the twentieth century seemed to indicate that at a high rate of oxygen consumption (referred to gram of body weight) was normally associated with a low maximum lifespan. Thus, it was thought that it was the rate of oxygen utilisation that was related to “the rate of living”. However, more recent data pointed out that birds are unique because they combine high rates of oxygen consumption with a high maximum lifespan. It would later be pointed out that the maximal lifespan is more correlated with the rate of free radical production by mitochondria rather than the rate of oxygen utilisation. These experiments were performed under the general scheme of the free radical theory of ageing. Still, more than 300 theories have been postulated to explain ageing and this can indicate that none of them is completely satisfactory to explain a complex phenomenon such as ageing. We postulate in this chapter that the free radical theory of ageing could be revisited and that it is the age-associated derangement of the free radical signalling network that is central to understand ageing.