Changes in insulin action and glut4 with six days of inactivity in
endurance runners.
Vukovich, Matthew D., Paul J. Arciero, Wendy M. Kohrt, Susan B.
Racette, Polly A. Hansen, John O. Holloszy.
Washington University Medical School, Section of Applied
Physiology, 4566 Scott Ave. Box 8113, St. Louis, MO 63110
APStracts 2:0393A, 1995.
The purpose of this investigation was to determine if decreased
insulin action following 6 days of inactivity in endurance trained
runners was associated with a decrease in skeletal muscle glucose
transporter protein levels (GLUT4) in the gastrocnemius muscle. Seven
endurance runners (males = 5, females = 2) 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 each, at
insulin infusion rates of 15 (LO) and 40 (HI) mU x m-2 x min-1, one
18 hrs after a training bout (TR) and the second following 6 d of
inactivity (IA). Muscle biopsies for the measurement of GLUT4 were
obtained from the gastrocnemius prior to each clamp. Glucose disposal
rates (GDR) during the last 30 min of each insulin infusion,
expressed as mg x kg FFM-1 x min-1, were significantly reduced after
6 days of inactivity, averaging 6.45 +/- 1.04 before and 4.55 +/-
0.56 after detraining for the LO insulin infusion rate, and 13.77 +/-
0.88 before and 11.81 +/- 0.60 after detraining for the HI insulin
infusion rate (both p<0.05), despite the fact that plasma
insulin was higher (p<0.05) in the inactive state (LO: 19.2 +/-
0.9 [mu]U x ml-1 before and 23.4 +/- 1.5 [mu]U x ml-1 after; HI:
56.0+/-2.0 [mu]U x ml-1 before and 61.6+/-1.6 [mu]U x ml-1 after).
Calculated insulin clearance was greater (P<0.03) in the trained
than in the inactive state. Muscle GLUT4 transporter protein
following 6 days of inactivity was reduced by 17.5 +/- 5.4%
(P<0.02). These results demonstrate that 6 days of inactivity
reduces insulin action in endurance trained runners and suggest that
a reduction in muscle GLUT4 transporter level plays a role in the
decrease in glucose disposal rates.
Received 27 March 1995; accepted in final form 31 August 1995.
APS Manuscript Number A336-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.