Exercise training and clenbuterol reduce insulin resistance of obese Zucker rats

C. E. Torgan, J. T. Brozinick, E. A. Banks, Miriam Yvette Cortez-Cooper, R. E. Wilcox, J. L. Ivy

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40 Scopus citations


This study compared the effects of aerobic exercise training and chronic administration of the selective β2-adrenergic agonist clenbuterol on whole body and skeletal muscle insulin resistance in obese (fa/fa) Zucker rats. Obese rats were randomly assigned to training, clenbuterol, or sedentary control groups. Lean littermates served as a second control group. After 4-5 wk of treatment, an oral glucose tolerance test was performed, followed 1 wk later by hindlimb perfusion, during which time the rates of glucose uptake and 3-O-methyl-D-glucose (3-MG) transport were assessed in the presence of a submaximal (500 μU/ml) insulin concentration. Training resulted in a significant increase in citrate synthase and cytochrome oxidase activity in the recruited muscles. Clenbuterol induced a large increase in muscle mass but provoked a significant decrease in oxidative enzyme activity and β- adrenergic receptor density. Both treatments increased glucose tolerance and reduced the postglucose insulin response, with the improvements being more pronounced in the clenbuterol group. However, only exercise training improved insulin-stimulated hindlimb muscle glucose uptake (11.37 ± 0.65, 8.73 ± 0.77, and 8.27 ± 0.41 μmol · g-1 · h-1 for trained, clenbuterol, and sedentary control groups, respectively) and 3-MG transport. These results suggest that aerobic exercise training attenuated the insulin-resistant condition in the obese Zucker rat by a mechanism other than or in addition to β2-adrenergic receptor activation.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number3 27-3
StatePublished - Jan 1 1993


  • fiber type
  • glucose tolerance
  • glucose transport
  • glucose uptake
  • oxidative enzymes
  • skeletal muscle

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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    Torgan, C. E., Brozinick, J. T., Banks, E. A., Cortez-Cooper, M. Y., Wilcox, R. E., & Ivy, J. L. (1993). Exercise training and clenbuterol reduce insulin resistance of obese Zucker rats. American Journal of Physiology - Endocrinology and Metabolism, 264(3 27-3).