Abstract P631: Hyperglycemia-induced Glycosylation: A Driving Force for Vascular Dysfunction in Diabetes?

Abstract

Vascular endothelial dysfunction leading to increased risk of coronary artery disease and peripheral vascular disease remains an important problem in type 2 diabetic mellitus (T2DM). T2DM patients with a high glycation index of hemoglobin A 1C have a greater risk of vascular complications, suggesting there is a correlation between hyperglycemia-induced glycosylation and the progression of vascular dysfunction. The objective of this study was to better understand hyperglycemia-induced glycosylation in the vascular endothelium and its contribution to the onset and progression of T2DM. Initial characterization of the effects of hyperglycemia on ex vivo vasodilation and in vitro tube formation assays exhibited impaired endothelial phenotypes (p<0.05). PNGaseF enzymatic removal of endothelial cell surface glycosylations was able to restore the healthy tube formation phenotypes (p<0.05). To identify specific glycosylations contributing to this impairment we used a glycoproteomic approach to examine differential glycosylation on the rat microvascular endothelial cell surface following normal (4.5 mM) and high (25 mM) glucose treatments. In comparisons of the groups, 273 N-glycosylation and 499 O-glycosylation modified proteins were identified. Of these proteins, 87 were significantly increased in N-glycosylation and 143 in O-glycosylation as a result of the high glucose treatment (p<0.05). Bioinformatics analyses of the targets revealed differential glycosylation of important endothelial cell surface receptors, a diverse array of ion channels, and immune regulators. The CD59 glycoprotein, important for protection from innate immunity, was increased in N-glycosylation (2.02 fold, p<0.05) and O-glycosylation (unique). Interestingly, glycosylation of CD59 is known to inhibit this protection from innate immunity. The lipoprotein receptor LRP1, important for leptin signaling and energy homeostasis, was also significantly increased in total N-glycosylation (1.8-fold total; p<0.05) and has been linked to insulin resistance. Overall, this study identified multiple hyperglycemia-induced differential glycosylations in the endothelium that may be key regulators of vascular dysfunction during the onset and progression of T2DM.