Exercise induces a transient increase in transcription of the GLUT-4 gene in skeletal muscle

• Published in: The American journal of physiology Vol. 265; no. 6 Pt 1; pp. C1597 - C1603
• Main Authors: Neufer, P D, Dohm, G L
• Format: Journal Article
• Language: English
• Published: United States 01-12-1993
• Subjects: Analysis of Variance; Animals; Blotting, Northern; Blotting, Western; Cell Nucleus - metabolism; Citrate (si)-Synthase - metabolism; Gene Expression Regulation - physiology; Glucose Transporter Type 1; Glucose Transporter Type 4; Male; Molecular Weight; Monosaccharide Transport Proteins - biosynthesis; Monosaccharide Transport Proteins - isolation & purification; Monosaccharide Transport Proteins - metabolism; Muscle Proteins; Muscles - metabolism; Muscles - physiology; Physical Conditioning, Animal; Rats; Rats, Sprague-Dawley; RNA - isolation & purification; Space life sciences; Time Factors; Transcription, Genetic
• ISSN: 0002-9513
• DOI: 10.1152/ajpcell.1993.265.6.c1597

Endurance exercise training elicits an increase in mitochondrial density as well as GLUT-4 glucose transporter protein content in skeletal muscle. Corresponding increases in mRNA for respiratory enzymes and GLUT-4 indicate that pretranslational control mechanisms are involved in this adaptive process. To directly test whether transcription of the GLUT-4 gene is activated in response to exercise training, nuclei were isolated from red hindlimb skeletal muscle of rats after 1 wk of exercise training (8% grade, 32 m/min, 40 min, twice/day). Rats were killed either 30 min, 3 h, or 24 h after the last training session. GLUT-4 transcription, determined by nuclear run-on analysis, was unaltered after 30 min, increased by 1.8-fold after 3 h, but was no longer different from controls 24 h after exercise. A similar transient increase in GLUT-4 transcription was evident, but less pronounced (1.4-fold), in untrained rats after a single bout of exercise, suggesting that the postexercise induction in GLUT-4 gene transcription is enhanced by exercise training. GLUT-4 protein content was increased 1.7-fold after 1 wk of training in the absence of any corresponding change in GLUT-4 mRNA, providing evidence that the initial increase in GLUT-4 expression involves translational and/or posttranslational control mechanisms. These findings demonstrate that muscle GLUT-4 expression in response to exercise training is subject to both transcriptional and posttranscriptional regulation. We propose that the increase in GLUT-4 mRNA evident with extended periods of training may result from a shift to pretranslational control and is the cumulative effect of repeated postexercise transient increases in GLUT-4 gene transcription.