Aging and short-term calorie restriction differently affect the cardiac and skeletal muscle expression of genes regulating energy substrate utilization in male rats.

Aging affects the energy metabolism differently in the cardiac and skeletal muscles. The study aim was to assess the effects of short-term calorie restriction (SCR) and refeeding on the expression of genes involved in the control of cardiac and skeletal muscle energy metabolism in old vs. young male rats. Young (4 mo) and old (24 mo) rats were subjected to 60% SCR for 30 days, and refed ad libitum for 2 or 4 days. In the cardiac (CM) and skeletal muscles (SM) we compared the gene expression (qPCR) of carnitine palmitoyltransferase-I (Cpt-I), peroxisome proliferator-activated receptor beta/delta (Ppar-β/δ), glucose transporter 4 (Glut4), peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α), and sirtuin 3 (Sirt3). In CM, aging increased Cpt-I expression but did not affect the other genes. In SM, Cpt-I, Glut4, Pgc-1α, and Sirt3 mRNA levels were lower in old than young rats. In CM of only young rats SCR increased Cpt-I expression which remained elevated after refeeding. Upon SCR, the expression of Ppar-β/δ, Glut4, Pgc-1α, and Sirt3 in CM increased in young but not old rats, and refeeding re-established control levels. In SM of young rats SCR increased Ppar-β/δ and Pgc-1α, and decreased Sirt3 expression, whereas refeeding generally decreased these mRNA levels. In SM of old rats SCR decreased only Pgc-1α expression. The adaptive response to SCR and subsequent refeeding is muscle tissue-specific and differs in young and old male rats. SCR appears to increase the efficiency of glucose and fatty acid utilization in the cardiac muscle of young, but not old male rats.