Calorie restriction increases cell surface GLUT-4 in insulin-stimulated skeletal muscle

DJ Dean, JT Brozinick Jr… - American Journal of …, 1998 - journals.physiology.org
DJ Dean, JT Brozinick Jr, SW Cushman, GD Cartee
American Journal of Physiology-Endocrinology and Metabolism, 1998journals.physiology.org
Reduced calorie intake [calorie restriction (CR); 60% of ad libitum (AL)] leads to enhanced
glucose transport without altering total GLUT-4 glucose transporter abundance in skeletal
muscle. Therefore, we tested the hypothesis that CR (20 days) alters the subcellular
distribution of GLUT-4. Cell surface GLUT-4 content was higher in insulin-stimulated
epitrochlearis muscles from CR vs. AL rats. The magnitude of this increase was similar to the
CR-induced increase in glucose transport, and GLUT-4 activity (glucose transport rate …
Reduced calorie intake [calorie restriction (CR); 60% of ad libitum (AL)] leads to enhanced glucose transport without altering total GLUT-4 glucose transporter abundance in skeletal muscle. Therefore, we tested the hypothesis that CR (20 days) alters the subcellular distribution of GLUT-4. Cell surface GLUT-4 content was higher in insulin-stimulated epitrochlearis muscles from CR vs. AL rats. The magnitude of this increase was similar to the CR-induced increase in glucose transport, and GLUT-4 activity (glucose transport rate divided by cell surface GLUT-4) was unaffected by diet. The CR effect was specific to the insulin-mediated pathway, as evidenced by the observations that basal glucose transport and cell surface GLUT-4 content, as well as hypoxia-stimulated glucose transport, were unchanged by diet. CR did not alter insulin’s stimulation of insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI3K) activity. Muscle abundance of IRS-2 and p85 subunit of PI3K were unaltered by diet, but IRS-1 content was lower in CR vs. AL. These data demonstrate that, despite IRS-1-PI3K activity similar to AL, CR specifically increases insulin’s activation of glucose transport by enhancing the steady-state proportion of GLUT-4 residing on the cell surface.
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