title: PPARβ activation restores the high glucose-induced impairment of insulin signalling in endothelial cells.
abstract: OBJECTIVE
  PPARβ enhances insulin sensitivity in adipocytes and skeletal muscle cells, but its effects on insulin signalling in endothelial cells are not known. We analysed the effects of the PPARβ/δ (PPARβ) agonists, GW0742 and L165041, on impaired insulin signalling induced by high glucose in HUVECs and aortic and mesenteric arteries from diabetic rats.
  
  
  METHODS
  Insulin-stimulated NO production, Akt-Ser(473) and eNOS-Ser(1177) phosphorylation, and reactive oxygen species (ROS) production were studied in HUVECs incubated in low- or high-glucose medium. Insulin-stimulated relaxations and protein phosphorylation in vessels from streptozotocin (STZ)-induced diabetic rats were also analysed.
  
  
  RESULTS
  HUVECs incubated in high-glucose medium showed a significant reduction in insulin-stimulated production of NO. High glucose also reduced insulin-induced Akt-Ser(473) and eNOS-Ser(1177) phosphorylation, increased IRS-1-Ser(636) and ERK1/2-Thr(183) -Tyr(185) phosphorylation and increased ROS production. The co-incubation with the PPARβ agonists GW0742 or L165041 prevented all these effects induced by high glucose. In turn, the effects induced by the agonists were suppressed when HUVEC were also incubated with the PPARβ antagonist GSK0660, the pyruvate dehydrogenase kinase (PDK)4 inhibitor dichloroacetate or after knockdown of both PPARβ and PDK4 with siRNA. The ERK1/2 inhibitor PD98059, ROS scavenger catalase, inhibitor of complex II thenoyltrifluoroacetone or uncoupler of oxidative phosphorylation, carbonyl cyanide m-chlorophenylhydrazone, also prevented glucose-induced insulin resistance. In STZ diabetic rats, oral GW0742 also improved insulin signalling and the impaired NO-mediated vascular relaxation.
  
  
  CONCLUSIONS
  PPARβ activation in vitro and in vivo restores the endothelial function, preserving the insulin-Akt-eNOS pathway impaired by high glucose, at least in part, through PDK4 activation.
authors: Department of Pharmacology, University of Granada, 18071, Granada, Spain.
authors: A M
authors: AM
authors: Quintela
authors: R
authors: R
authors: Jiménez
authors: L
authors: L
authors: Piqueras
authors: M
authors: M
authors: Gómez-Guzmán
authors: J
authors: J
authors: Haro
authors: M J
authors: MJ
authors: Zarzuelo
authors: A
authors: A
authors: Cogolludo
authors: M J
authors: MJ
authors: Sanz
authors: M
authors: M
authors: Toral
authors: M
authors: M
authors: Romero
authors: F
authors: F
authors: Pérez-Vizcaíno
authors: J
authors: J
authors: Duarte
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D048068:PPAR-beta / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014162:Transfection
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; C000631432:PDK4 protein, human; D048068:PPAR-beta; C000631440:Pdk4 protein, rat; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: HUVECs; PPARβ; insulin signalling; reactive oxygen species