Changes in insulin action and GLUT-4 with 6 days of inactivity in endurance runners

Matthew D. Vukovich, Paul J. Arciero, Wendy M. Kohrt, Susan B. Racette, Polly A. Hansen, John O. Holloszy

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

Abstract

The purpose of this investigation was to determine whether decreased insulin action after 6 days of inactivity in endurance-trained runners was associated with a decrease in skeletal muscle glucose transporter protein levels (GLUT-4) in the gastrocnemius muscle. Seven endurance runners (5 men and 2 women) volunteered to participate in this investigation. All subjects had normal glucose tolerance as determined by the National Diabetes Data Group guidelines. Each individual completed two hyperinsulinemic euglycemic clamps at insulin infusion rates of 15 (LO) and 40 (HI) mU · m-2 · min- 1, one ~18 h after a training bout and the second after 6 days of inactivity (IA). Muscle biopsies for the measurement of GLUT-4 were obtained from the gastrocnemius before each clamp. Glucose disposal rates during the last 30 min of each insulin infusion were significantly reduced after 6 days of IA, averaging 6.45 ± 1.04 mg · kg fat-free mass (FFM)-1 · min-1 before and 4.55 ± 0.56 mg · kg FFM-1 · minafter detraining for the LO insulin infusion rate and 13.77 ± 0.88 mg · kg FFM-1 · min-1 before and 11.81 ± 0.60 mg · kg FFM-1 · min-1 after detraining for the HI insulin infusion rate (both P < 0.0.5), despite the fact that plasma insulin was higher in the inactive state (LO, 19.2 ± 0.9 μU/ml before and 23.4 ± 1.5 μU/ml after detraining; HI, 56.0 ± 2.0 μU/ml before and 61.6 ± 1.6 mU/ml after detraining; P < 0.05). Calculated insulin clearance was greater in the trained than in the inactive state (P < 0.03). Muscle GLUT-4 transporter protein after 6 days of IA was reduced by 17.5 ± 5.4% (P < 0.02). These results demonstrate that 6 days of IA reduces insulin action in endurance-trained runners and suggest that a reduction in muscle GLUT-4 transporter level plays a role in the decrease in glucose disposal rates.

Original languageEnglish
Pages (from-to)240-244
Number of pages5
JournalJournal of Applied Physiology
Volume80
Issue number1
DOIs
StatePublished - Jan 1996

Keywords

  • detraining
  • euglycemic
  • glucose disposal rates
  • hyperinsulinemic clamp
  • plasma insulin

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