EFFECT OF OVEREXPRESSING GLUT-1 AND GLUT-4 ON INSULIN-STIMULATED AND CONTRACTION-STIMULATED GLUCOSE-TRANSPORT IN MUSCLE

To examine the effects of GLUT-ion GLUT-4-dependent, insulin-stimulate d, and contraction-stimulated 2-deoxy-D-glucose (2-DG) transport, we o verexpressed GLUT-1 in metabolically heterogeneous skeletal muscles [r ed and white tibialis anterior (TA) and extensor digitorum longus (EDL )] via 7 days of chronic electrical stimulation. GLUT-1 was increased 1.6- to 16.4-fold (P < 0.05). Basal 2-DG transport was increased 1.7- to 3.0-fold (P < 0.05) and was equal to (red TA and EDL; P > 0.05) or exceeded insulin-stimulated 2-DG transport by 50% (white TA; P < 0.05) in the control muscles. GLUT-4 was concomitantly overexpressed (2.1- to 4.4-fold; P < 0.05). Insulin-stimulated 2-DG transport was increase d 1.6- to 2.5-fold (P < 0.05). During muscle contractions, 2-DG transp ort increased 9- to 12-fold (P < 0.05) in control muscles, but this wa s reduced by similar to 25% (P < 0.05) in muscles overexpressing GLUT- 1 and GLUT-4 (red TA and EDL). In contrast, in the experiment, white T A contraction-stimulated 2-DG transport was increased 1.7-fold (P < 0. 05). Therefore, overexpression of GLUT-1, when GLUT-4 is also overexpr essed, does not impair insulin-stimulated 2-DG transport, although con traction-stimulated transport may be reduced in some muscles.