Insulin-dependent activation of endothelial nitric oxide synthase is impaired by O-linked glycosylation modification of signaling proteins in human coronary endothelial cells.
BACKGROUND
Hyperglycemia impairs functional properties of cytosolic and nuclear proteins via O-linked glycosylation modification (O-GlcNAcylation). We studied the effects of O-GlcNAcylation on insulin signaling in human coronary artery endothelial cells.


RESULTS
O-GlcNAcylation impaired the metabolic branch of insulin signaling, ie, insulin receptor (IR) activation of the IR substrate (IRS)/phosphatidylinositol 3-kinase (PI3-K)/Akt, whereas it enhanced the mitogenic branch, ie, ERK-1/2 and p38 (mitogen-activated protein kinase). Both in vivo and in vitro phosphorylation of endothelial nitric oxide synthase (eNOS) by Akt were reduced by hyperglycemia and hexosamine activation. Insulin-induced eNOS activity in vivo was reduced by hyperglycemia and hexosamine activation, which was coupled to increased activation and expression of matrix metalloproteinase-2 and -9; these phenomena were reversed by inhibition of the hexosamine pathway. Finally, carotid plaques from type 2 diabetic patients showed increased endothelial O-GlcNAcylation with respect to nondiabetics.


CONCLUSIONS
Our data show that hyperglycemia, through the hexosamine pathway, impairs activation of the IR/IRS/PI3-K/Akt pathway, resulting in deregulation of eNOS activity.
Federici
Massimo
M
Department of Internal Medicine, University of Tor Vergata, Rome, Italy. federicm@uniroma2.it
Menghini
Rossella
R
Mauriello
Alessandro
A
Hribal
Marta Letizia
ML
Ferrelli
Francesca
F
Lauro
Davide
D
Sbraccia
Paolo
P
Spagnoli
Luigi Giusto
LG
Sesti
Giorgio
G
Lauro
Renato
R
D001161:Arteriosclerosis / Q000150:complications / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D048909:Diabetes Complications; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004789:Enzyme Activation; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D006031:Glycosylation; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007329:Insulin Antagonists / Q000494:pharmacology; D020782:Matrix Metalloproteinases / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000378:metabolism
D007328:Insulin; D007329:Insulin Antagonists; D011506:Proteins; D019717:Tissue Inhibitor of Metalloproteinase-3; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D020782:Matrix Metalloproteinases; D005947:Glucose; D005944:Glucosamine