Abstract 10874: O-Linked β-N-acetylglucosamine Modification is Increased in Freshly Isolated Human Endothelial Cells in Type 2 Diabetes

Abstract

Background: Diabetes mellitus (DM) is characterized by hyperglycemia that may contribute to abnormal vascular function. High glucose levels upregulate the hexosamine biosynthesis pathway leading to protein glycosylation with O-linked N-acetylglucosamine (O-GlcNAc). We sought to investigate the functional relevance of O-GlcNAc modification to endothelial dysfunction in DM. Method and Results: Freshly isolated endothelial cells obtained by J-wire biopsy from patients with DM had impaired insulin-mediated eNOS phosphorylation at Ser1177 compared to controls. Incubation in normal glucose conditions (5mM, 24hours) restored insulin-mediated eNOS phosphorylation in endothelial cells from patients with DM whereas insulin resistance persisted in high glucose conditions (30mM), suggesting a link between glucose levels and endothelial insulin resistance. Endothelial O-GlcNAc level was higher in diabetes patients compared to healthy controls (22±8 vs 12±5%, N=18/10, P=0.003, Figure A). Higher endothelial O-GlcNAc levels correlated with higher body mass index (P= 0.03), fasting blood glucose (P=0.01), HbA1C (P=0.02), and triglycerides (P=0.01). Normal glucose conditions lowered O-GlcNAc levels in endothelial cells isolated from patients with DM (P=0.028, Figure B). Ongoing studies are evaluating the effect of agents that reducing O-GlcNAc on insulin-mediated eNOS phosphorylation. Conclusion: Our results provide evidence that O-GlcNAc is more abundant in the endothelium of diabetic patients and glucose normalization reduces O-GlcNAc and improves reaction to insulin. Further work is needed to determine the contribution of O-GlcNAc modification to vascular disease in diabetes.