Does the aging skeletal muscle maintain its endocrine function?
Contracting skeletal muscles produce and release the cytokine interleukin (IL)-6 and this release is augmented by the presence of low muscle glycogen. Since muscle metabolism in elderly subjects relies on glycogen more than younger subjects, it is possible that aging is associated with an altered production of muscle-derived IL-6 during exercise. To test the relation between aging and muscle-derived IL-6, seven healthy elderly males, mean age 70+/-1 (SEM) yr and six healthy young males, mean age 26+/-2 (SEM) yr performed three hours of dynamic knee-extensor exercise at 50% of maximal work load (Wmax). IL-6 mRNA and glycogen in muscles were analysed and the IL-6 release were estimated before, during and after the exercise. Although the absolute work load in the elderly was less than half of that in the young, 41.1+/-3.1 W and 92.5+/-4.0 W, respectively, the muscle glycogen utilization after three hours of exercise did not differ between groups, 238.7+/-52.4 and 245.2+/-74.0 mmol/kg musc
