Early alterations in soleus GLUT-4, glucose transport, and glycogen in voluntary running rats

E. J. Henriksen, A. E. Halseth

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

Voluntary wheel running (WR) by juvenile female rats was used as a noninterventional model of soleus muscle functional overload to study the regulation of insulin-stimulated glucose transport activity by the glucose transporter (GLUT-4 isoform) protein level and glycogen concentration. Soleus total protein content was significantly greater (+18%; P < 0.05) than in age- matched controls after 1 wk of WR, and this hypertrophic response continued in weeks 2-4 (+24-32%). GLUT-4 protein was 39% greater than in controls in 1- wk WR soleus, and this adaptation was accompanied by a similar increase in in vitro insulin-stimulated glucose transport activity (+29%). After 2 and 4 wk of WR, however, insulin-stimulated glucose transport activity had returned to control levels, despite a continued elevation (+25-28%) of GLUT-4 protein. At these two time points, glycogen concentration was significantly enhanced in WR soleus (+21-42%), which coincided with significant reductions in glycogen synthase activity ratios (-23 to -41%). These results indicate that, in this model of soleus muscle functional overload, the GLUT-4 protein level may initially regulate insulin-stimulated glucose transport activity in the absence of changes in other modifying factors. However, this regulation of glucose transport activity by GLUT-4 protein may be subsequently overridden by elevated glycogen concentration.

Original languageEnglish (US)
Pages (from-to)1862-1867
Number of pages6
JournalJournal of Applied Physiology
Volume76
Issue number5
DOIs
StatePublished - Jan 1 1994

Keywords

  • carbohydrate metabolism
  • exercise training
  • insulin action
  • skeletal muscle hypertrophy

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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