title: Impact of GLO1 knock down on GLUT4 trafficking and glucose uptake in L6 myoblasts.
abstract: Methylglyoxal (MG), a highly reactive α-dicarbonyl metabolite of glucose degradation pathways, protein and fatty acid metabolism, plays an important role in the pathogenesis of diabetic complications. Hyperglycemia triggers enhanced production of MG and increased generation of advanced glycation endproducts (AGEs). In non-enzymatic reactions, MG reacts with arginine residues of proteins to form the AGEs argpyrimidine and hydroimidazolone. Glyoxalase 1 (GLO1), in combination with glyoxalase 2 and the co-factor glutathione constitute the glyoxalase system, which is responsible for the detoxification of MG. A GLO1 specific knock down results in accumulation of MG in targeted cells. The aim of this study was to investigate the effect of intracellularly accumulated MG on insulin signaling and on the translocation of the glucose transporter 4 (GLUT4). Therefore, L6 cells stably expressing a myc-tagged GLUT4 were examined. For the intracellular accumulation of MG, GLO1, the first enzyme of the glyoxalase pathway, was down regulated by siRNA knock down and cells were cultivated under hyperglycemic conditions (25 mM glucose) for 48 h. Here we show that GLO1 knock down augmented GLUT4 level on the cell surface of L6 myoblasts at least in part through reduction of GLUT4 internalization, resulting in increased glucose uptake. However, intracellular accumulation of MG had no effect on GLUT4 concentration or modification. The antioxidant and MG scavenger NAC prevented the MG-induced GLUT4 translocation. Tiron, which is also a well-known antioxidant, had no impact on MG-induced GLUT4 translocation.
authors.affiliation: Ruhr-University Bochum, Diabetes Center, Heart and Diabetes Center NRW, Bad Oeynhausen, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Engelbrecht
authors.forename: Bernd
authors.initials: B
authors.lastname: Stratmann
authors.forename: Cornelius
authors.initials: C
authors.lastname: Hess
authors.forename: Diethelm
authors.initials: D
authors.lastname: Tschoepe
authors.forename: Thomas
authors.initials: T
authors.lastname: Gawlowski
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D003920:Diabetes Mellitus / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007791:Lactoylglutathione Lyase / Q000235:genetics* / Q000378:metabolism; D032446:Myoblasts / Q000201:enzymology*; D018384:Oxidative Stress; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011765:Pyruvaldehyde / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C495694:Slc2a4 protein, rat; D011765:Pyruvaldehyde; C494920:Akt1 protein, rat; C494923:Akt2 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D007791:Lactoylglutathione Lyase; D005947:Glucose