Dietary restriction attenuates age-related increases in rat skeletal muscle antioxidant enzyme activities

Dietary restriction (DR) retards aging in rodents, but its mechanism of action remains unclear. Free radicals have been hypothesized to be involved in aging and in DR's actions. We investigated the influences of age and DR on the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD) in skeletal muscle from 11-, 26- and 34-mo-old (BN x Fischer 344) F1 rats fed either ad libitum (AL) or subjected to a 30% DR from 14 weeks of age. The mass of the upper hindlimb muscles recoverable in 34-mo-old AL rats was only 52% that of 11-mo-old AL rats, whereas rats on DR showed a stable, intermediate value at both ages. CAT and GPX activities increased progressively and markedly in muscle of AL animals with aging. The increase in CAT activity was partially attenuated by DR, while that of GPX was entirely prevented. These effects of aging and DR were more profound in 12,000 x g pellets than in cytosolic fractions. SOD activities were more variable and not clearly influenced by age or DR. These data agree with prior reports of an age-related increase in skeletal muscle antioxidant enzyme activities. Further, DR attenuates this alteration and does so most profoundly in the 12,000 x g pellet, the fraction which is enriched in mitochondria.