Effects of Exercise Training on Regulation of Skeletal Muscle Glucose Metabolism in Elderly Men

Abstract

Background: The aim was to investigate the molecular mechanisms behind exercise training-induced improvements in glucose regulation in aged subjects.

Methods: Twelve elderly male subjects completed 8 weeks of exercise training. Before and after the training period, the subjects completed an oral glucose tolerance test (OGTT) and a muscle biopsy was obtained from the vastus lateralis before and 45 minutes into the OGTT. Blood samples were collected before and up to 120 minutes after glucose intake.

Results: Exercise training increased Hexokinase II, GLUT4, Akt2, glycogen synthase (GS), pyruvate dehydrogenase (PDH)-E1α, PDK2 protein, and glycogen content in skeletal muscle. Furthermore, in response to glucose, GS activity was increased and the dephosphorylation of GS site 2 + 2a and 3a was enhanced after the training intervention. The glucose-mediated insulin stimulation of TBC1D4 Thr(642) phosphorylation was increased after exercise training. In the trained state, the PDHa activity was reduced following glucose intake and without changes in phosphorylation level of PDH-E1α.

Conclusions: The present results suggest that exercise training improves glucose regulation in elderly subjects by enhancing the capacity and acute regulation of glucose uptake and by enhancing intracellular glucose removal to glycogen synthesis rather than glucose oxidation.

Keywords: Aging; Glycogen synthase; Insulin signaling.; Physical activity; Pyruvate dehydrogenase.