Influences of dietary restriction and age on liver enzyme activities and lipid peroxidation in mice.

Dietary restriction extends maximum life span in rodents by unknown mechanisms. We compared livers from 12- and 24-mo-old mice fed control (C, approximately 95 kcal/wk) or restricted (R, approximately 55 kcal/wk) amounts of diet since 3 wk of age. We hypothesized that dietary restriction might alter the activity levels of enzymes with possible relevance to aging processes. The enzymes included several xenobiotic metabolizers, radical scavengers (catalase, superoxide dismutase, glutathione peroxidase), superoxide sources (xanthine oxidase, peroxisomal beta-oxidation of palmitoyl-CoA) and glucose-6-phosphatase. Lipid peroxidation (LP) was also measured. Comparing 12- and 24-mo-old mice, the strongest diet or age effect was an increased catalase activity for group R (42% higher at 12 mo, 64% at 24 mo). LP was clearly lower in group R at 12 mo (a 30% decrease) and somewhat lower (13%) at 24 mo than in group C. Similarly, in 12-mo-old C and R mice injected with either the P-450 inducer beta-naphthoflavone (beta-NF in corn oil) or with corn oil alone. R mice showed higher catalase activity (40-44%) and lower LP (43-46%) in both beta-NF-injected and vehicle-injected groups. These data suggest that if free radical damage is involved in aging, it may be a particular kind of damage, that is, that in part prevented by a selective increase in catalase activity.