title: Oxidant stress reduces insulin responsiveness in 3T3-L1 adipocytes.
abstract: Increased oxidant stress has been suggested to occur in diabetes and to contribute to the development of late diabetic complications. Whether oxidant stress plays a role in the development or progression of insulin resistance is not known. In this study we hypothesized that exposing 3T3-L1 adipocytes to prolonged micromolar concentrations of H2O2 would reduce their acute metabolic responses to insulin stimulation. 3T3-L1 adipocytes exposed to 25 mU/ml glucose oxidase (GO) for 18 h exhibited a threefold increase in basal 2-deoxyglucose (2-DG) uptake activity. However, net increase in 2-DG uptake activity after acute insulin (100 nM) stimulation was 355 +/- 56 pmol.mg protein-1.min-1 in control vs. 198 +/- 41 pmol.mg protein-1.min-1 in GO-pretreated cells (P < 0.05). Basal lipogenesis activity was significantly enhanced by GO, but acute insulin stimulation resulted in significantly reduced lipogenesis activity (29 +/- 4 vs. 11 +/- 1 nmol glucose/well for control and 50 mU/ml GO, respectively, P = 0.001). Glycogen synthase alpha activity was reduced by GO (78 +/- 1 vs. 43 +/- 2 pmol UDP-glucose.mg protein-1.min-1, P = 0.03), whereas insulin stimulation of glycogen synthase was reduced, exhibiting a right shift in the insulin dose-response curve. These effects of GO were associated with increased GLUT-1 and reduced GLUT-4 protein and mRNA content. In conclusion, our data suggest that oxidant stress alters glucose transporters expression and insulin-stimulated metabolism in 3T3-L1 adipocytes.
authors.affiliation: Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Rudich
authors.forename: N
authors.initials: N
authors.lastname: Kozlovsky
authors.forename: R
authors.initials: R
authors.lastname: Potashnik
authors.forename: N
authors.initials: N
authors.lastname: Bashan
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D003847:Deoxyglucose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005949:Glucose Oxidase / Q000494:pharmacology; D006006:Glycogen Synthase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D007527:Isoenzymes / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis; D051379:Mice; D018384:Oxidative Stress
chemical_list: D007328:Insulin; D007527:Isoenzymes; D008055:Lipids; D003847:Deoxyglucose; D006861:Hydrogen Peroxide; D005949:Glucose Oxidase; D006006:Glycogen Synthase