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1 University of Michigan
2 Tohoku University
* To whom correspondence should be addressed. E-mail: gcartee{at}umich.edu.
A single exercise bout can increase insulin-independent glucose transport immediately post-exercise and insulin-dependent glucose transport (GT) for several hours post-exercise. Akt substrate of 160 kDa (AS160) and TBC1D1 are paralog Rab GTPase activating proteins that have been proposed to contribute to these exercise effects. Previous research demonstrated greater AS160 and Akt threonine phosphorylation in rat skeletal muscle at 3-4 h post-exercise concomitant with enhanced insulin-stimulated GT. To further probe if these signaling events or TBC1D1 phosphorylation were important for the enhanced post-exercise insulin-stimulated GT, male Wistar rats were studied using four experimental protocols (2 h swim-exercise, differing with regard to timing of muscle sampling and whether food was provided post-exercise) that were known to vary in their influence of insulin-independent and insulin-dependent GT post-exercise. The results indicated that in isolated rat epitrochlearis muscle: 1) elevated phosphorylation of AS160 (measured using anti-phospho-Akt substrate, PAS-AS160, and phospho-specific anti-Thr642-AS160, pThr642-AS160) consistently tracked with elevated insulin-stimulated GT; 2) PAS-TBC1D1 was not different from sedentary values at 3 or 27 h post-exercise, when insulin sensitivity was increased; 3) insulin-stimulated Akt activity was not increased post-exercise in muscles with increased insulin sensitivity; 4) PAS-TBC1D1 was increased immediately post-exercise, when insulin-independent GT was elevated, and reversed at 3 and 27 h post-exercise, when insulin-independent GT was also reversed; and 5) there was no significant effect of exercise or insulin on total abundance of AS160, TBC1D1, Akt or GLUT4 protein with any of the protocols. The results are consistent with increased AS160 phosphorylation (PAS-AS160 or pThr642-AS160), but not increased PAS-TBC1D1 or Akt activity, being important for increased post-exercise insulin-stimulated GT in rat skeletal muscle. They also support the idea that increased TBC1D1 phosphorylation may play a role in the insulin-independent increase in GT post-exercise.
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H. Alkhateeb, A. Chabowski, J. F. C. Glatz, B. Gurd, J. J. F. P. Luiken, and A. Bonen Restoring AS160 phosphorylation rescues skeletal muscle insulin resistance and fatty acid oxidation while not reducing intramuscular lipids Am J Physiol Endocrinol Metab, November 1, 2009; 297(5): E1056 - E1066. [Abstract] [Full Text] [PDF] |
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