title: Glucose-induced O₂ consumption activates hypoxia inducible factors 1 and 2 in rat insulin-secreting pancreatic beta-cells.
abstract: BACKGROUND
  Glucose increases the expression of glycolytic enzymes and other hypoxia-response genes in pancreatic beta-cells. Here, we tested whether this effect results from the activation of Hypoxia-Inducible-factors (HIF) 1 and 2 in a hypoxia-dependent manner.
  
  
  RESULTS
  Isolated rat islets and insulin-secreting INS-1E cells were stimulated with nutrients at various pO₂ values or treated with the HIF activator CoCl₂. HIF-target gene mRNA levels and HIF subunit protein levels were measured by real-time RT-PCR, Western Blot and immunohistochemistry. The formation of pimonidazole-protein adducts was used as an indicator of hypoxia. In INS-1E and islet beta-cells, glucose concentration-dependently stimulated formation of pimonidazole-protein adducts, HIF1 and HIF2 nuclear expression and HIF-target gene mRNA levels to a lesser extent than CoCl₂ or a four-fold reduction in pO₂. Islets also showed signs of HIF activation in diabetic Lepr(db/db) but not non-diabetic Lepr(db/+) mice. In vitro, these glucose effects were reproduced by nutrient secretagogues that bypass glycolysis, and were inhibited by a three-fold increase in pO₂ or by inhibitors of Ca²⁺ influx and insulin secretion. In INS-1E cells, small interfering RNA-mediated knockdown of Hif1α and Hif2α, alone or in combination, indicated that the stimulation of glycolytic enzyme mRNA levels depended on both HIF isoforms while the vasodilating peptide adrenomedullin was a HIF2-specific target gene.
  
  
  CONCLUSIONS
  Glucose-induced O₂ consumption creates an intracellular hypoxia that activates HIF1 and HIF2 in rat beta-cells, and this glucose effect contributes, together with the activation of other transcription factors, to the glucose stimulation of expression of some glycolytic enzymes and other hypoxia response genes.
authors.affiliation: Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Bensellam
authors.forename: Bertrand
authors.initials: B
authors.lastname: Duvillié
authors.forename: Galyna
authors.initials: G
authors.lastname: Rybachuk
authors.forename: D Ross
authors.initials: DR
authors.lastname: Laybutt
authors.forename: Christophe
authors.initials: C
authors.lastname: Magnan
authors.forename: Yves
authors.initials: Y
authors.lastname: Guiot
authors.forename: Jacques
authors.initials: J
authors.lastname: Pouysségur
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Jonas
mesh_terms: D053607:Adrenomedullin / Q000235:genetics; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D003920:Diabetes Mellitus / Q000378:metabolism / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000494:pharmacology*; D006019:Glycolysis / Q000235:genetics; D051793:Hypoxia-Inducible Factor 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D007700:Kinetics; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D053607:Adrenomedullin; D051792:Basic Helix-Loop-Helix Proteins; D002118:Calcium; D005947:Glucose; D051793:Hypoxia-Inducible Factor 1; D007328:Insulin; D010100:Oxygen; D012333:RNA, Messenger; D000099162:Endothelial PAS Domain-Containing Protein 1