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Skeletal muscle glucose utilization, a major factor in the control of whole-body glucose tolerance, is modulated in accordance with the muscle metabolic demand. For instance, it is increased in chronic contraction or exercise training in association with elevated expression of GLUT4 and hexokinase II (HK-II). In this work, the contribution of increased metabolic flux to the regulation of the glucose transport capacity was analyzed in cultured human skeletal muscle engineered to overexpress glycogen phosphorylase (GP). Myocytes treated with an adenovirus-bearing muscle GP cDNA (AdCMV-MGP) expressed 10 times higher GP activity and exhibited a twofold increase in the Vmax for 2-deoxy-D-[3H]glucose (2-DG) uptake, with no effect on the apparent Km. The stimulatory effect of insulin on 2-DG uptake was also markedly enhanced in AdCMV-MGP-treated cells, which showed maximal insulin stimulation 2.8 times higher than control cells. No changes in HKII total activity or the intracellular compartmentalization were found. GLUT4, protein, and mRNA were raised in AdCMV-MGP-treated cells, suggesting pretranslational activation. GLUT4 was immunodetected intracellularly with a perinuclear predominance. Culture in glucose-free or high-glucose medium did not alter GLUT4 protein content in either control cells or AdCMV-MGP-treated cells. Control and GP-overexpressing cells showed similar autoinhibition of glucose transport, although they appeared to differ in the mechanism(s) involved in this effect. Whereas GLUT1 protein increased in control cells when they were switched from a high-glucose to a glucose-free medium, GLUT1 remained unaltered in GP-expressing cells upon glucose deprivation. Therefore, the increased intracellular metabolic (glycogenolytic-glycolytic) flux that occurs in muscle cells overexpressing GP causes an increase in GLUT4 expression and enhances basal and insulin-stimulated glucose transport, without significant changes in the autoinhibition of glucose transport. This mechanism of regulation may be operative in the postexercise situation in which GLUT4 expression is upregulated in coordination with increased glycolytic flux and energy demand.
S Baqué, and
E Montell, and
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J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
February 1996,
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M Camps, and
J J Guinovart, and
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A M Gómez-Foix
January 2005,
Acta physiologica Scandinavica,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
May 1994,
The Journal of biological chemistry,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
January 2004,
Pflugers Archiv : European journal of physiology,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
October 1994,
Diabetes,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
February 1997,
Biochemical Society transactions,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
January 1996,
The Biochemical journal,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
January 2005,
Diabetologia,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
September 2003,
FASEB journal : official publication of the Federation of American Societies for Experimental Biology,
S Baqué, and
E Montell, and
M Camps, and
J J Guinovart, and
A Zorzano, and
A M Gómez-Foix
January 1983,
Acta physiologica Scandinavica. Supplementum,
