Declines in mitochondrial number and function in skeletal muscle are thought to play a primary role in aging process. Cytochrome c oxidase (CcO) is the terminal complex of the mitochondrial
respiratory chain and is comprised of 13 subunits encoded by three mitochondrial genes (COX subunits I, II, and III) and 10 nuclear genes (COX subunits IV, Va, Vb, VIa, VIb, VIc, VIIa, VIIb, VIIc, and
VIII), and is the rate-limiting site of cellular respiration. Cytochrome c oxidase deficiency has been proposed to be a causal factor in the age-related decline in mitochondrial respiratory activity.
This study was designed to explore the possible relationship between the changes of CcO composition and aging, and to investigate if exercise and caloric restriction could alter the effects of aging.
32 male SD rats, 21 months old, were randomly divided into four groups (n=8 each): (1) Aging Control (AC), (2) Caloric Restriction (CR), (3) Exercise (E), and (4) Exercise and Caloric Restriction
(ECR). Another 8 rats of 3 months old were also used a young control group (YC). The E and ECR groups began with moderate intensity treadmill training at 10 m/min for 30 minutes per session in the
first week as an adaptation phase. The training time then increased to 45 minutes per session for 12 weeks. The CR and ECR groups were given 60% of the average of three consecutive day’s food intake,
every day for the experimental period. At the end of 12 weeks interventions, skeletal muscle samples were obtained. The samples were divided into two parts, with one part was treated for extraction of
mitochondria immediately; and the other part was stored at -80℃ before analyses of proteins. The extracted mitochondria were divided into two parts, with one part for analysis of mitochondrial
membrane proteins; and the other part was for analysis of mitochondrial proteins. The total protein concentration was determined by Bradford method. Western-blotting was used to determine COX I and
COX IV protein contents in tissues and mitochondria. One part of mitochondrial membrane proteins was analyzed by NA-PAGE method and the other part was analyzed by SDS-PAGE method. The proportions of
CcO subunits were also determined.
(1) The levels of tissue and mitochondrial COX I and COX IV protein were significantly lower in the AC than YC (p > 0.05), and higher in the E, CR and ECR groups than that of the AC (p < 0.05);
(2) The proportions of the 13 CcO subunits did not show significant changes neither in the AC, nor in the E, CR and ECR groups (p > 0.05).
(3) The COX I and COX IV protein contents in the heart and skeletal muscle tissues and in the mitochondria also did not show significant differences between groups.
(1) The tissue and mitochondrial COX I and COX IV protein contents were lower in the aging control groups, while exercise and caloric restriction appeared to have an effect of delaying the aging
process in these proteins.
(2) The total protein of CcO subunits and the proportions of COX I and COX IV were not significantly affected by aging and exercise or caloric restriction interventions.