High glucose inhibits insulin-stimulated nitric oxide production without reducing endothelial nitric-oxide synthase Ser(1177) phosphorylation in human aortic endothelial cells

Salt, I. , Morrow, V., Brandie, F., Connell, J. and Petrie, J. (2003) High glucose inhibits insulin-stimulated nitric oxide production without reducing endothelial nitric-oxide synthase Ser(1177) phosphorylation in human aortic endothelial cells. Journal of Biological Chemistry, 278(21), pp. 18791-18797. (doi:10.1074/jbc.M210618200)

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Abstract

Recent studies have indicated that insulin activates endothelial nitric-oxide synthase ( eNOS) by protein kinase B (PKB)-mediated phosphorylation at Ser(1177) in endothelial cells. Because hyperglycemia contributes to endothelial dysfunction and decreased NO availability in types 1 and 2 diabetes mellitus, we have studied the effects of high glucose ( 25 mM, 48 h) on insulin signaling pathways that regulate NO production in human aortic endothelial cells. High glucose inhibited insulin-stimulated NO synthesis but was without effect on NO synthesis stimulated by increasing intracellular Ca2+ concentration. This was accompanied by reduced expression of IRS-2 and attenuated insulin-stimulated recruitment of PI3K to IRS-1 and IRS-2, yet insulin-stimulated PKB activity and phosphorylation of eNOS at Ser(1177) were unaffected. Inhibition of insulin-stimulated NO synthesis by high glucose was unaffected by an inhibitor of PKC. Furthermore, high glucose down-regulated the expression of CAP and Cbl, and insulin-stimulated Cbl phosphorylation, components of an insulin signaling cascade previously characterized in adipocytes. These data suggest that high glucose specifically inhibits insulin-stimulated NO synthesis and down-regulates some aspects of insulin signaling, including the CAP-Cbl signaling pathway, yet this is not a result of reduced PKB-mediated eNOS phosphorylation at Ser(1177). Therefore, we propose that phosphorylation of eNOS at Ser(1177) is not sufficient to stimulate NO production in cells cultured at 25 mM glucose.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Salt, Dr Ian and Petrie, Professor John and Connell, Professor John
Authors: Salt, I., Morrow, V., Brandie, F., Connell, J., and Petrie, J.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences
Journal Name:Journal of Biological Chemistry
Journal Abbr.:J Biol Chem.
Publisher:American Society for Biochemistry and Molecular Biology, Inc.
ISSN:0021-9258
ISSN (Online):1083-351X

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