Effect of dietary restriction on age-related increase of liver susceptibility to peroxidation in rats

Dietary restriction (DR) increases life span and decreases age-related diseases in experimental animals. It has received a great deal of attention in connection with the relationship between aging, nutrition, and oxidative stress because oxidative injury in several organ systems is a prominent feature in aging. We investigated the possibility that DR can protect vulnerable liver lipids against age-related increases of peroxidation. Male Fischer 344 rats fed ad libitum (AL) or dietarily restricted (maintained on 60% of AL food intake) were killed by decapitation at 4 (young) or 12 mon (adult) of age. Phosphatidylcholine hydroperoxide (PCOOH) concentration of liver was determined using a chemiluminescent high-performance liquid chromatographic method. Liver PCOOH increased with age in adult rats, but less of an increase of PCOOH was seen in DR rats, which is consistent with results on production of thiobarbituric acid-reactive substances and oxygen-derived free radicals. No significant differences were found in liver superoxide dismutase and catalase activity between AL and DR groups of young and adult rats. Liver triglyceride and cholesterol contents were lower in DR than AL rats at 12 mon. Fatty acid compositions of phosphatidylcholine and phosphatidylethanolamine indicated that the ratio of (20:3n-6 + 20:4n-6)/18:2n-6, an index of linoleic acid (18:2n-6) desaturation, was lower in DR than in AL rats. We concluded that DR suppresses age-related oxidative damage in liver by modulating the amount of lipid as well as fatty acid composition.