title: Development of insulin resistance in 3T3-L1 adipocytes.
abstract: Insulin resistance is a manifestation of both diabetes mellitus and obesity. However, the mechanism is still not clearly identified. Herein, we describe a procedure that allows us to evaluate the development of insulin resistance in 3T3-L1 adipocytes. Under these conditions, we show that the concentration of insulin required for 50% desensitization of glucose transport activity is 100 pM; maximal desensitization could be achieved with 1 nM. This demonstrates for the first time that 3T3-L1 adipocytes develop insulin resistance in response to physiologically relevant concentrations of insulin. Glucose (or glucosamine), in addition to insulin, was required to establish desensitization. The expression of GLUT4 protein decreased by 50% with exposure to 10 nM insulin. The dose-dependent loss of GLUT4 was similar to the dose dependence for insulin-resistant transport activity. Translocation in the presence of acute insulin was apparent, but the extent of recruitment directly reflected the decrease in GLUT4 protein. GLUT4 mRNA also declined, but the ED50 was approximately 5 nM. Together, these data suggest that the loss of GLUT4 protein likely underlies the cause of desensitization. However, the loss of GLUT4 protein did not correlate with the loss in GLUT4 mRNA suggesting post-translational control of GLUT4 expression.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Thomson
authors.forename: M G
authors.initials: MG
authors.lastname: Williams
authors.forename: S C
authors.initials: SC
authors.lastname: Frost
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D005786:Gene Expression Regulation / Q000187:drug effects; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009124:Muscle Proteins; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495693:Slc2a4 protein, mouse; D005947:Glucose; D005944:Glucosamine