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The effect of exercise and insulin on AS160 phosphorylation and 14-3-3 binding capacity in human skeletal muscle

¹School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia; and ²MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom

Submitted 18 August 2007 ; accepted in final form 25 November 2007

AS160 is an Akt substrate of 160 kDa implicated in the regulation of both insulin- and contraction-mediated GLUT4 translocation and glucose uptake. The effects of aerobic exercise and subsequent insulin stimulation on AS160 phosphorylation and the binding capacity of 14-3-3, a novel protein involved in the dissociation of AS160 from GLUT4 vesicles, in human skeletal muscle are unknown. Hyperinsulinemic-euglycemic clamps were performed on seven men at rest and immediately and 3 h after a single bout of cycling exercise. Skeletal muscle biopsies were taken before and after the clamps. The insulin sensitivity index calculated during the final 30 min of the clamp was 8.0 ± 0.8, 9.1 ± 0.5, and 9.2 ± 0.8 for the rest, postexercise, and 3-h postexercise trials, respectively. AS160 phosphorylation increased immediately after exercise and remained elevated 3 h after exercise. In contrast, the 14-3-3 binding capacity of AS160 and phosphorylation of Akt and AMP-activated protein kinase were only increased immediately after exercise. Insulin increased AS160 phosphorylation and 14-3-3 binding capacity and insulin receptor substrate-1 and Akt phosphorylation, but the response to insulin was not enhanced by prior exercise. In conclusion, the 14-3-3 binding capacity of AS160 is increased immediately after acute exercise in human skeletal muscle, but this is not maintained 3 h after exercise completion despite sustained AS160 phosphorylation. Insulin increases AS160 phosphorylation and 14-3-3 binding capacity, but prior exercise does not appear to enhance the response to insulin.

glucose transport; type 2 diabetes

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				J. P. Thyfault Setting the stage: possible mechanisms by which acute contraction restores insulin sensitivity in muscle Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2008; 294(4): R1103 - R1110. [Abstract] [Full Text] [PDF]