title: Insulin-sensitive regulation of glucose transport and GLUT4 translocation in skeletal muscle of GLUT1 transgenic mice.
abstract: Skeletal muscle glucose transport was examined in transgenic mice overexpressing the glucose transporter GLUT1 using both the isolated incubated-muscle preparation and the hind-limb perfusion technique. In the absence of insulin, 2-deoxy-d-glucose uptake was increased approximately 3-8-fold in isolated fast-twitch muscles of GLUT1 transgenic mice compared with non-transgenic siblings. Similarly, basal glucose transport activity was increased approximately 4-14-fold in perfused fast-twitch muscles of transgenic mice. In non-transgenic mice insulin accelerated glucose transport activity approximately 2-3-fold in isolated muscles and to a much greater extent ( approximately 7-20-fold) in perfused hind-limb preparations. The observed effect of insulin on glucose transport in transgenic muscle was similarly dependent upon the technique used for measurement, as insulin had no effect on isolated fast-twitch muscle from transgenic mice, but significantly enhanced glucose transport in perfused fast-twitch muscle from transgenic mice to approximately 50-75% of the magnitude of the increase observed in non-transgenic mice. Cell-surface glucose transporter content was assessed via 2-N-4-(l-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(d -mannos-4-yloxy)-2-propylamine photolabelling methodology in both isolated and perfused extensor digitorum longus (EDL). Cell-surface GLUT1 was enhanced by as much as 70-fold in both isolated and perfused EDL of transgenic mice. Insulin did not alter cell-surface GLUT1 in either transgenic or non-transgenic mice. Basal levels of cell-surface GLUT4, measured in either isolated or perfused EDL, were similar in transgenic and non-transgenic mice. Interestingly, insulin enhanced cell-surface GLUT4 approximately 2-fold in isolated EDL and approximately 6-fold in perfused EDL of both transgenic and non-transgenic mice. In summary, these results reveal differences between isolated muscle and perfused hind-limb techniques, with the latter method showing a more robust responsiveness to insulin. Furthermore, the results demonstrate that muscle overexpressing GLUT1 has normal insulin-induced GLUT4 translocation and the ability to augment glucose-transport activity above the elevated basal rates.
authors.affiliation: Pfizer Central Research, Eastern Point Road, Groton, CT 06340, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Etgen
authors.forename: W J
authors.initials: WJ
authors.lastname: Zavadoski
authors.forename: G D
authors.initials: GD
authors.lastname: Holman
authors.forename: E M
authors.initials: EM
authors.lastname: Gibbs
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001386:Azides; D001483:Base Sequence; D001692:Biological Transport; D015153:Blotting, Western; D017931:DNA Primers; D004187:Disaccharides; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006027:Glycosides; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008822:Mice, Transgenic; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011437:Propylamines
chemical_list: D000345:Affinity Labels; D001386:Azides; D017931:DNA Primers; D004187:Disaccharides; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006027:Glycosides; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011437:Propylamines; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; C065412:2-N-(4-(1-azitrifluoroethyl)benzoyl)-1,3-bis-(mannos-4-yloxy)-2-propylamine; D005947:Glucose