Selective Enhancement of Insulin Sensitivity in the Endothelium In Vivo Reveals a Novel Proatherosclerotic Signalling Loop

• Published in: Circulation research Vol. 120; no. 5; pp. 784 - 798
• Main Authors: Viswambharan, Hema, Yuldasheva, Nadira, Sengupta, Anshuman, Imrie, Helen, Gage, Matthew, Haywood, Natalie, Walker, Andrew MN, Skromna, Anna, Makova, Natallia, Galloway, Stacey, Shah, Pooja, Sukumar, Piruthivi, Porter, Karen E, Grant, Peter J, Shah, Ajay M, Santos, Celio XC, Li, Jing, Beech, David J, Wheatcroft, Stephen B, Cubbon, Richard M, Kearney, Mark T
• Format: Journal Article
• Language: English
• Published: United States American Heart Association, Inc 03.03.2017; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Acetylcholine; AKT protein; Animals; Arteriosclerosis; Atherosclerosis - metabolism; Atherosclerosis - pathology; Cells, Cultured; CYBB protein; Diabetes mellitus; Diabetes mellitus (non-insulin dependent); Endothelial cells; Endothelial Cells - metabolism; Endothelial Cells - pathology; Endothelium; Endothelium, Vascular - metabolism; Endothelium, Vascular - pathology; Human Umbilical Vein Endothelial Cells; Humans; Insulin; Insulin Resistance - physiology; Kinases; Male; Mechanical stimuli; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Transgenic; NAD(P)H oxidase; Nitric-oxide synthase; Organ Culture Techniques; Phosphorylation; Proline; Proline-rich tyrosine kinase 2; Protein-tyrosine kinase; Signal Transduction - physiology; Superoxide; Vasodilation; diabetes mellitus; insulin; superoxide; insulin resistance; reactive oxygen species
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/CIRCRESAHA.116.309678

RATIONALE:In the endothelium, insulin stimulates endothelial nitric oxide synthase (eNOS) to generate the anti-atherosclerotic signalling radical NO. Insulin resistant type 2 diabetes is associated with reduced NO availability and accelerated atherosclerosis. The effect of enhancing endothelial insulin sensitivity on NO availability is unclear. OBJECTIVE:To answer this question we generated a mouse with endothelial cell (EC)-specific over-expression of the human insulin receptor (hIRECO) using the Tie2 promoter-enhancer. METHODS AND RESULTS:hIRECO demonstrated significant endothelial dysfunction measured by blunted endothelium-dependent vasorelaxation to acetylcholine which was normalized by a specific Nox2 NADPH oxidase inhibitor. Insulin-stimulated phosphorylation of Akt was increased in hIRECO EC as was Nox2 NADPH oxidase-dependent generation of superoxide, whereas insulin and shear stress-stimulated eNOS activation were blunted. Phosphorylation at the inhibitory residue Y657 of eNOS and expression of PYK2 which phosphorylates this residue were significantly higher in hIRECO EC. Inhibition of PYK2 improved insulin and shear-induced eNOS activation in hIRECO EC. CONCLUSIONS:Enhancing insulin sensitivity specifically in EC leads to a paradoxical decline in endothelial function, mediated by increased tyrosine phosphorylation of eNOS and excess Nox2 derived superoxide. Increased EC insulin sensitivity leads to a pro-atherosclerotic imbalance between NO and superoxide. Inhibition of PYK2 restores insulin- and shear-induced NO production. This study demonstrates for the first time that increased endothelial insulin sensitivity leads to a pro-atherosclerotic imbalance between NO and superoxide.