The Biological basis of the aging process

Abstract

The basic chemical process underlying aging was first put forward by the free radical theory of aging in 1956; the reaction of active free radicals (normally produced within an organism itself) with cellular constituents initiates the changes associated with aging. The involvement of free radicals in aging is related to their key role in the origin and evolution of life. The specific composition of tissue macromolecules (proteins, nucleic acids, lipids and carbohydrates) in long-lived animal species gives them an intrinsically high resistance to modification that probably contributes to the superior longevity of these species. Long-lived species also show low rates of reactive oxygen species (ROS) generation and oxidative damage to their mitochondria. Dietary restriction further decreases mitochondrial ROS production and oxidative molecular damage due to the decreased intake of dietary proteins. These effects of protein restriction seem to be specifically due to the lowered methionine intake of protein and dietary restricted animals. Both a low rate of generation of endogenous damage and an intrinsically high resistance to the modification of tissue macromolecules are key traits of animal longevity.