Some biochemical parameters of ageing in relation to dietary protein.

An investigation was undertaken to study the effect of dietary protein level on some age-related biochemical processes in mice. Weanling mice were fed a laboratory diet containing protein at 6, 12 or 24% and adequate in all other nutrients, for up to 52 weeks. Although the rate of gain in body weight of the animals between 3 and 6 weeks was related to the dietary level of protein, the final body weights of mice in different groups were not significantly different. Lipid peroxidation in liver homogenate, free activities of some lysosomal enzymes of brain, liver and intestine, and the accumulation of lipofuscin pigments showed an increase with the dietary level of protein. On the other hand, the activity of superoxide dismutase in liver showed an inverse relationship to the protein level of the diet. The findings are discussed in relation to the free-radical theory of ageing.