Anti-ageing interventions and their neuroendocrine aspects in mammals.

A number of interventions for delaying or reversing declines in body functions due to ageing are critically reviewed here, including their relation to neuroendocrine function. Diets severely deficient in calories retard the ageing of body tissues, inhibit the development of disease and tumours, and significantly prolong the lifespan of rats and mice. Such diets also decrease hormone secretion, reduce the metabolism of the whole body, and lower gene expression. Administration of hormones, thymic peptides and other immune factors, and appropriate drugs can improve declining immune function in old rats and mice, thereby increasing resistance to infection, autoimmune disease and tumours. In old rats, correction of faults that develop in the neuroendocrine system with age--particularly in the hypothalamus--can restore oestrous cycles, increase the secretion of growth hormone, increase protein synthesis, inhibit development of disease and tumours, and prolong life. Antioxidants administered to rats and mice in an attempt to reduce damage to cells caused by free radicals, do not significantly retard ageing or prolong the lifespan of these animals. Regular, moderate exercise in elderly humans decreases incidence of heart disease, improves lung function, reduces bone loss, and produces other beneficial effects. Suitable drugs that will improve memory function in elderly humans remain to be developed, although a few have produced small improvements albeit with undesirable side effects. Overall, the neuroendocrine and immune approaches offer the best prospects for delaying and reversing declines in body functions due to ageing.