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 dise ases in experimental animals. It has received a great deal of attention in connection with the relationship between aging, nutrition, and oxidative st ress because oxidative injury in several organ systems is a prominent featu re in aging. We investigated the possibility that DR can protect vulnerable liver lipids against age-related increases of peroxidation. Male Fischer 3 44 rats fed ad libitum (AL) or dietarily restricted (maintained on 60% of A L food intake) were killed by decapitation at 4 (young) or 12 mon (adult) o f age. Phosphatidylcholine hydroperoxide (PCOOH) concentration of liver was determined using a chemiluminescent high-performance liquid chromatographi c method. Liver PCOOH increased with age in adult rats, but less of an incr ease of PCOOH was seen in DR rats, which is consistent with results on prod uction of thiobarbituric acid-reactive substances and oxygen-derived free r adicals. No significant differences were found in liver superoxide dismutas e and catalase activity between AL and DR groups of young and adult rats. L iver triglyceride and cholesterol contents were lower in DR than AL rats at 12 mon. Fatty acid compositions of phosphatidylcholine and phosphatidyleth anolamine 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 mo dulating the amount of lipid as well as fatty acid composition.