Effect of ageing and caloric restriction on specific markers of protein oxidative damage and membrane peroxidizability in rat liver mitochondria.

To gain insight into the anti-ageing mechanisms of caloric restriction (CR), liver mitochondria were isolated from male Brown-Norway rats of different ages (fully fed control and CR) and various specific markers of non-enzymatic protein modification (by oxidative, glyco- and lipoxidative-reactions) were measured by GC/MS and Western blotting. A membrane peroxidizability index (PI) was calculated from the fatty acid profiles. Between 6 and 18 months of age, there were significant decreases in the concentration of all markers of damage in mitochondria from both the fully fed and CR groups. In contrast, between the ages of 18 and 28 months, there were significant increases in the concentrations of all markers of damage. In mitochondria from both fully fed and CR groups, there were significant increases in N-epsilon (Nepsilon)-(carboxymethyl)lysine (CML) and N-epsilon-(malondialdehyde)lysine (MDAL) between 6 and 28 months of age. In general, damage tended to be lower in mitochondria from CR animals, but the effects were not significant, except for the concentration of N-epsilon-(carboxymethyl)lysine at 28 months of age. PI increased steadily and significantly with age in fully fed animals, whilst CR induced a significant decrease in this index at 28 months of age. It is concluded that for male rats of the Brown-Norway strain, and mitochondria from liver (i) old (but not mature) age is associated with an increased membrane PI and protein oxidative damage and (ii) CR does not lead to a general reversion in age-related protein damage, but it does prevent the age-induced increase in PI very late in life.