The effects of aging on enzyme activities and metabolite concentrations in skeletal muscle from sedentary male and female subjects.

Aging affects the metabolic capacity of skeletal muscle, in particular the glycolytic and respiratory capacities. The purpose of this study was to quantify biochemical alterations due to aging in muscular metabolic capacity in human skeletal muscles in sedentary subjects. The activities of various marker enzymes and metabolites related to glycolysis, Krebs' cycle and the electron transfer chain and high energy phosphate compounds were measured in muscle biopsies from the rectus abdominis, vastus lateralis, and gluteus maximus muscles of 76 sedentary subjects (32 males and 44 females) between 15 and 91 yr. No significant differences between males and females were found, but changes related to age were: a decrease in hexokinase and lactate dehydrogenase activities in the rectus abdominis; a decrease in citrate synthase activity and citrate in the vastus lateralis; an increase in pyruvate kinase activity and a decrease in ATP and creatine phosphate concentrations in the gluteus maximus. These data suggest that distinct muscles may respond differently to aging regardless of sex in sedentary subjects.