Two recently identified glucose transporters, GLUT8 and GLUT12, are expressed in human skeletal muscle and may be involved in insulin-mediated sugar transport.
The purpose of this study was to measure GLUT8 and GLUT12 mRNA levels in endurance-trained versus sedentary individuals in an effort to determine the effect of repeated days of contractile activity on gene expression.
GLUT 4, 8, and 12 mRNA were measured in biopsies from the vastus lateralis using quantitative real-time PCR in endurance-trained (N = 16, age = 22.0 ± 0.9 yr, V̇O2max (L·min−1) = 4.13 ± 0.25) and sedentary (N = 15, age = 21.3 ± 0.8 yr, V̇O2max (L·min−1) = 3.21 ± 0.24) subjects.
GLUT12 mRNA was lower (40 ± 14%, P < 0.05) in the exercise-trained compared with the sedentary subjects. There was no difference between groups in GLUT8 mRNA content. mRNA of the insulin-sensitive glucose transporter (GLUT4) was 78 ± 27% (P < 0.05) higher in skeletal muscle from endurance-trained compared with sedentary individuals.
These findings suggest an isoform-specific effect on the mRNA of the glucose transporters in human skeletal muscle with repeated days of contractile activity.
1Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY; and 2East Carolina University, Human Performance Laboratory, Department of Exercise and Sport Science, Greenville, NC
Address for correspondence: Maureen J. Charron, Ph.D., Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461; E-mail: Charron@aecom.yu.edu.
Submitted for publication September 2005.
Accepted for publication January 2006.