Exercise in maintenance hemodialysis patients induces transcriptional changes in genes favoring anabolic muscle

Exercise training increases exercise capacity of maintenance hemodialysis patients, but the cellular mechanisms responsible for this effect are unclear. We studied the effects of different forms of exercise training (endurance, strength, or a combination where patients underwent about one-half each of the endurance and strength training of the first two groups) on mRNA levels of genes in muscle that may contribute to increased exercise capacity. Before exercise training, muscle mRNA of insulin-like growth factor (IGF)-IEa, lGF-I receptor, IGF-II, IGF-binding protein (IGFBP)-2, and lGFBP-3 were lower in hemodialysis patients than normal controls. After approximately 21 weeks of exercise training, muscle mRNA increased significantly for all of these genes, as well as for IGF-lEc. Muscle mRNA for myostatin, a protein that inhibits skeletal muscle protein synthesis and muscle hypertrophy, decreased. The responses of mRNA to the different types of exercise training generally showed similar significant changes or trends. Muscle IGF-I protein also increased with exercise. Anthropometry, but not dual energy x-ray absorptiometry or bioelectrical impedance, showed a decrease in body fat and an increase in fat-free mass. In conclusion, exercise training in hemodialysis patients induces changes in skeletal muscle mRNA and increases muscle IGF-I protein, which may promote protein anabolism.