title: Prolonged exposure to high insulin impairs the endothelial PI3-kinase/Akt/nitric oxide signalling.
abstract: Hyperinsulinemia predicts future cardiovascular events, but may also contribute to atherosclerosis. We therefore studied the consequences of prolonged insulin treatment of human umbilical vein endothelial cells (HUVEC) on the phosphatidylinositol-3'-kinase(PI3K)/Akt/nitric oxide(NO)-dependent insulin signaling, together with the expression of the pro-atherogenic molecule vascular cell adhesion molecule (VCAM)-1. HUVEC were incubated with insulin (10(-11) to 10(-7) M) in short- (30 min) and long-term (24 h to 3 days) incubations. In short-term incubations, insulin did not affect constitutive Akt and eNOS at any concentration, but significantly increased their active phosphorylated forms, and NO production. In long-term incubations, however, such insulin effects on the phosphorylated forms, as well as NO production, were attenuated, promoting an effect of insulin also at concentrations otherwise ineffective. Such effects were accompanied by a boosting of insulin effect on VCAM-1 surface expression. In contrast, under similar conditions, insulin did not exert any significant effect on the surface expression of ICAM-1 and E-selectin. Therefore, prolonged exposure of HUVEC to high insulin levels induces a downregulation of the PI3K/Akt/eNOS axis. Such impairment of insulin signalling in states of prolonged hyperinsulinemia pontially contributes to detrimental effects on atherogenesis in insulin resistance states, such as the metabolic syndrome and type 2 diabetes.
authors.affiliation: Institute of Cardiology, "G. d'Annunzio" University - Chieti, C/o Ospedale Clinicizzato SS. Annunziata, Via dei Vestini, 66013 Chieti, Italy.
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Madonna
authors.forename: Raffaele
authors.initials: R
authors.lastname: De Caterina
mesh_terms: D002448:Cell Adhesion; D019040:E-Selectin / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006946:Hyperinsulinism / Q000201:enzymology*; D007328:Insulin / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D020298:U937 Cells; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D019040:E-Selectin; D004791:Enzyme Inhibitors; D007328:Insulin; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019331:NG-Nitroarginine Methyl Ester