Exercise, unlike insulin, promotes glucose transporter translocation in obese Zucker rat muscle

P. A. King, J. J. Betts, E. D. Horton, E. S. Horton

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40 Scopus citations

Abstract

Insulin or exercise stimulates skeletal muscle glucose transport, most likely by increasing both the number and activity of glucose transporters in the plasma membrane. Skeletal muscle glucose transport of genetically obese Zucker rats (fa/fa) displays a severe insulin resistance that results, at least in part, from a failure of net transporter translocation to the cell membrane (King, P., E. D. Horton, M. Hirshman, and E. S. Horton. J. Clin. Invest. 90: 1568-1575, 1992). The purpose of the present study was to determine if the obese rat muscle was also resistant to the action of acute exercise to increase glucose transport and, if so, to determine if the defect involved transporter translocation as seen in the resistance to insulin. The muscle glucose transport system was investigated in plasma membranes isolated from postprandial, sedentary or acutely exercised, lean and obese Zucker rats. Measurements of D- and L-glucose uptake by membrane vesicles under equilibrium exchange conditions indicated that an acute bout of exercise resulted in a threefold increase in the maximum velocity (V(max)) for lean animals (5.7 vs. 17.6 nmol · mg protein-1 · min-1) and a 4.5-fold increase in the V(max) for obese rats (4.1 vs. 18.6 nmol · mg protein-1 · min-1). For both lean and obese animals, this increase in transport was associated with an increase in transporter number measured by cytochalasin B binding (1.6- and 2.2-fold, respectively) and with an increase in the average carrier turnover number (1.9- and 2.0-fold, respectively). The results indicate that, unlike a maximal insulin stimulus, acute exercise of the obese Zucker rat promotes both transporter translocation and transporter activation in skeletal muscle.

Original languageEnglish
Pages (from-to)R447-R452
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume265
Issue number2 34-2
DOIs
StatePublished - 1993

Keywords

  • glucose transport
  • insulin resistance
  • membrane vesicles

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