Protection of Tissue Mass/Body Mass by Combination of Lifelong Voluntary Exercise and Mild (8%) Caloric Restriction in Aging Fischer-344 Rats

Abstract

Advancing age is associated with reduction of skeletal muscle mass and hypertrophy of the heart. Evidence indicates that moderate (30–40%) caloric restriction (CR) conserves maintenance of skeletal muscle and heart mass and myocyte number. Exercise training in aging populations may also provide protection against sarcopenia in skeletal muscle and remodeling in the heart. PURPOSE: To investigate whether lifelong voluntary exercise or mild (8%) caloric restriction provide protection of tissue mass/body mass in rat skeletal muscle, heart, brain, kidney, and liver. METHODS: We tested the hypothesis that 8% CR or lifelong wheel running + 8% CR would conserve tissue mass/body mass ratio by dividing male Fischer-344 rats at 11 weeks into four groups: fed ad libitum until 6 mo. old (6AL, n=12); fed ad libitum until 24 mo. old (24AL, n=11); 8% caloric restriction from 11 wk to 24 mo of age (24CR, n= 12); wheel running from 11 wk to 24 mo. with 8% caloric restriction (24ExCR, n=12). RESULTS: Body mass was significantly lower in the 24ExCR group than 6AL and 24CR. Skeletal muscle mass/body mass was better conserved with age (means similar to 6AL) in 24ExCR compared with 24AL and 24CR in the gastrocnemius, tibialis anterior, extensor digitorum longus, vastus lateralis, and plantaris, and compared with 24CR in the soleus. Heart mass was higher in 24AL than 6AL, but not 24CR and 24ExCR. In addition, brain mass/body mass was significantly higher in 24ExCR than 6AL, 24AL, and 24ExCR. Kidney mass was higher in all age groups compared with 6AL. CONCLUSIONS: The combination of lifelong wheel running and mild caloric restriction conserved skeletal muscle mass/body mass and brain mass, while preventing age-induced elevation of heart mass in the Fischer-344 rat. Supported by an NIH Grant R01AG17994-01