Eccentric contractions decrease glucose transporter (glut4)
transcription rate, mrna and protein in skeletal muscle.
Kristiansen, S_ren, Jared Jones, Aase Handberg, G. Lynis Dohm and Erik
A. Richter.
Copenhagen Muscle Research Centre, August Krogh Institute,
University of Copenhagen, 13 Universitetsparken, DK-2100 Copenhagen,
Denmark, Department of Biochemistry, School of Medicine, East
Carolina University, Greenville, North Carolina 27858, Department of
Medical Physiology, Panum Institute, University of Copenhagen, 3
Blegdamsvej, DK-2100 Copenhagen, Denmark
APStracts 3:0416C, 1996.
We have recently shown that eccentric contractions (forced lengthening
of active muscle) elicit a delayed decrease in glucose transporter
(GLUT4) protein content in rat skeletal muscle and a decrease in
subsequent contraction-stimulated glucose transport. Here we
investigate whether this decrease in total GLUT4 protein after prior
eccentric contractions is due to changes in GLUT4 gene transcription
rate and GLUT4 mRNA level. Furthermore, the effect of prior eccentric
contrations on sarcolemmal GLUT4 protein content in plasma membrane
(PM) vesicles isolated from contraction-stimulated muscle was
determined. Rat gastrocnemius muscle was electrically stimulated for
eccentric contractions (EC) and the contralateral muscle served as
unstimulated control (UC). Two days later the total GLUT4 protein
content was decreased by 50% (p<0.05) and 32% (p<0.05)
in the white and red gastrocnemius muscle, respectively. Furthermore,
the GLUT4 mRNA concentration was decreased by 41% (p<0.05) in
both the white and red gastrocnemius muscle. Moreover, the GLUT4
transcription rate, determined by nuclear run-on analysis, was
decreased by 75% (p<0.05) in mixed EC gastrocnemius muscle
compared with UC muscle. PM vesicles were isolated from EC and UC
muscle after 15 min of isometric contractions. The PM GLUT4 protein
content was reduced by 51% (p<0.05) in EC muscle compared with
UC muscle. In conclusion, 2 days after eccentric contractions the
GLUT4 transcription rate, GLUT4 mRNA and GLUT4 protein content were
decreased in rat skeletal muscle. Moreover, the PM GLUT4 protein
content in contraction-stimulated muscle was decreased. We suggest
that eccentric muscle contractions decrease muscle GLUT4
transcription rate resulting in a lower GLUT4 protein content, which
in turn decreases the number of GLUT4 transporters translocated to
the sarcolemma ultimatively leading to decreased contraction-induced
muscle glucose transport.
Received 22 August 1996; accepted in final form 13 December 1996.
APS Manuscript Number C489-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996