Biological Theories of Aging

What are the Underlying Causes of Aging?

Aging is a complex of biological processes involving mechanisms of regulation of altered gene expression, protein synthesis and degradation (protein turnover), and processes associated with oxidative metabolism and biological processes of detoxification. Furthermore, a major causative factor that has the potential to alter regulatory processes involves products of oxidative metabolism; that is, the metabolic production of oxygen-free radicals or reactive oxygen species (ROS) that damage macromolecules such as deoxyribonucleic acid (DNA) and proteins. Current theories on the molecular mechanisms of aging and longevity assurance propose that aging results from the accumulation of various intrinsic endobiotic toxins, also referred to as “metabolic rubbish,” whose production is due to the failure of metabolic detoxification processes. These natural biological processes are the body's mechanisms for protection against intrinsic (endobiotic) and environmental toxins.

There are a variety of theories of age-associated molecular interactions that focus on the development of cellular and organ dysfunction and deterioration. Many of these theories address the mechanisms of molecular, genetic, physiological, and environmental factors that affect cell and tissue homeostasis in aging.

[Page 75]Most recently, theories of molecular mechanisms of aging have focused on evidence that aging involves the metabolic generation of oxygen-free radicals (ROS) that damage macromolecules and the consequences of the failure to remove or repair these macromolecules. In aging tissues, these oxidatively damaged macromolecules affect the efficiency of tissue and organ function. Thus, the processes of aging and development of age-associated diseases has been attributed to the deleterious effects of oxygen-free radicals (ROS) that cause oxidative damage to macromolecules. Furthermore, because critical metabolic functions are localized within intracellular “factories” called organelles (metabolic power houses), oxidative damage to these structures may affect their efficiency of biological function. This is a major cause of the age-associated progressive decline in tissue function. This entry summarizes selected current theories of the molecular mechanisms of

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