Regulatory activity of DNA-binding peptides on some metabolic pathways altered in aging

The Smith theory, which describes aging as a consequence of damage at DNA transcription level, suggested to us the opportunity of studying the possible action of DNA-binding peptides from calf thymus on old rats. We previously demonstrated that this peptidic fraction exerts a regulative control on transcriptional activities of DNA in cell and cell-free systems. In order to verify the possible action of these low molecular weight peptides we chose a large range of metabolic and structural parameters which are altered in aging. The results obtained indicate the following conclusions. Lipids. The lipid levels of old rat liver and serum are altered compared with those of young rats; the administration of peptidic fraction to old rats reverses the lipid alterations observed. Glucides. In old rat liver the presence of glycogen is very scanty or completely absent; the animals treated with the peptides show an amount and distribution of glycogen similar to that of adult normal rats. ATP. The peptidic fraction causes in the old rats a marked increase of blood ATP, bringing the level in the range of values determined in young rats. DNA, RNA, proteins. The total synthesis rate of DNA, RNA and proteins in old rat liver is not influenced by the DNA-binding peptides. Vice versa the nucleic acids from liver nuclei of old rats given peptidic fraction contain a greater RNA component compared to control old rats. This result is confirmed by the strong increase of transcriptional activity of DNA for RNA polymerase caused by administration of peptidic fraction to old rats. This increased DNA transcription can be interpreted as a partial recovery of DNA transcriptional capacity which evidently might imply a restoration of impaired metabolic systems. The histochemical and stereological analyses of liver cell compartments confirm the biochemical data.