NUTRITIONAL INFLUENCE ON CELLULAR ANTIOXIDANT DEFENSE SYSTEMS

The metabolic machinery of the cell is able to reverse most adverse effects of the stress under normal conditions. However, when the reducing power of the cell is decreased or when the oxidative stress is markedly increased, irreversible damage to the cell may occur. The susceptibility of a given tissue to oxidative stress is determined by the balance between factors that promote oxidation and those that exert antioxidant action. The oxidative damage may be described as a consequence of antioxidant deficiency. A number of enzymes and compounds present in the cell may function to protect cellular components from oxidative damage. The major antioxidant defense systems appear to be those scavenging free radicals and singlet oxygen in conjunction with vitamin E and superoxide dismutase, and the reduction of hydroperoxides by the activities of catalase and GSH peroxidase. Many dietary components are closely interrelated and involved in various stages of antioxidant defense. The nutritional status of the affected subjects may directly or indirectly modify their antioxidant defense capability and thus the susceptibility to oxidative stress. It should be pointed out that the cellular reductive mechanisms differ from tissue to tissue and from species to species. Many other metabolic reactions and dietary components, which have yet to be studied, may also play an important role in cellular antioxidant defense. Furthermore, as most of the information has been generated using experimental animals, the translation of these data to the human remains to be demonstrated. Further study at the cellular and subcellular level of animals and additional studies with humans will be necessary to have a better understanding in this important area.