title: Glucose transport by osmotic shock and vanadate is impaired by glucosamine.
abstract: In 3T3-L1 adipocytes, we previously reported that glucosamine impairs insulin stimulation of glucose transport, which is accompanied by impaired insulin stimulation of serine/threonine kinase Akt. To examine the role of Akt in glucosamine-induced insulin resistance, we investigated time course for insulin stimulation of Akt activity and glucose transport during recovery from glucosamine-induced insulin resistance. After induction of insulin resistance by glucosamine, we washed cells to remove glucosamine and incubated them for various times. After one hour, insulin stimulated-glucose transport was significantly increased and continued to increase up to 6-24 h. Insulin stimulation of Akt, however, did not increase after 1-3 h and began to slightly increase after 6 h. Next, we investigated effects of osmotic shock and vanadate on glucose transport in glucosamine-treated cells and found that glucosamine completely inhibited their actions in these cells. These data suggest that an Akt-independent mechanism is operative in glucosamine-induced insulin resistance and glucosamine impairs glucose transport stimulated by various stimuli involving and not involving Akt activation.
authors.affiliation: Department of Physiology and Biophysics, University of Southern California, Los Angeles, California 90089-9142, USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Heart
authors.forename: Chin K
authors.initials: CK
authors.lastname: Sung
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D003847:Deoxyglucose / Q000032:analysis; D005944:Glucosamine / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007333:Insulin Resistance; D007700:Kinetics; D051379:Mice; D009997:Osmotic Pressure; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D014638:Vanadates / Q000037:antagonists & inhibitors*
chemical_list: D007328:Insulin; D011518:Proto-Oncogene Proteins; D014638:Vanadates; D003847:Deoxyglucose; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose; D005944:Glucosamine