Voluntary exercise training enhances glucose transport in muscle stimulated by insulin-like growth factor I

Jason Y. Hokama, Ryan S. Streeper, Erik J. Henriksen

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Skeletal muscle glucose transport can be regulated by hormonal factors such as insulin and insulin-like growth factor I (IGF-I). Although it is well established that exercise training increases insulin action on muscle glucose transport, it is currently unknown whether exercise training leads to an enhancement of IGF-I-stimulated glucose transport in skeletal muscle. Therefore, we measured glucose transport activity [by using 2-deoxy-D- glucose (2-DG) uptake] in the isolated rat epitrochlearis muscle stimulated by submaximally and maximally effective concentrations of insulin (0.2 and 13.3 nM) or IGF-I (5 and 50 nM) after 1, 2, and 3 wk of voluntary wheel running (WR). After 1 wk of WR, both submaximal and maximal insulin- stimulated 2-DG uptake rates were significantly (P < 0.05) enhanced (43 and 31%) compared with those of sedentary controls, and these variables were further increased after 2 (86 and 57%) and 3 wk (71 and 70%) of WR. Submaximal and maximal IGF-I-stimulated 2-DG uptake rates were significantly enhanced after 1 wk of WR (82 and 61%), and these increases did not expand substantially after 2 (71 and 58%) and 3 wk (96 and 70%) of WR. This enhancement of hormone-stimulated 2-DG uptake in WR muscles preceded any alteration in glucose transporter (GLUT-4) protein level, which increased only after 2 (24%) and 3 wk (54%) of WR. Increases in GLUT-4 protein were significantly correlated (r = 0.844) with increases in citrate synthase. These results indicate that exercise training can enhance both insulin- stimulated and IGF-I-stimulated muscle glucose transport activity and that these improvements can develop without an increase in GLUT-4 protein.

Original languageEnglish (US)
Pages (from-to)508-512
Number of pages5
JournalJournal of Applied Physiology
Volume82
Issue number2
DOIs
StatePublished - Feb 1997

Keywords

  • 2-deoxy-D-glucose uptake
  • GLUT-4 protein
  • citrate synthase
  • insulin
  • rat epitrochlearis muscle
  • wheel running

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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