O‐GlcNAcylation Mediates Glucose‐Induced Alterations in Endothelial Cell Phenotype in Human Diabetes Mellitus
Nobuyuki Masaki, Bihua Feng, Rosa Bretón‐Romero, Elica Inagaki, Robert M. Weisbrod, Jessica L. Fetterman, Naomi M. Hamburg
Abstract
Background Posttranslational protein modification with O‐linked N ‐acetylglucosamine (O‐Glc NA c) is linked to high glucose levels in type 2 diabetes mellitus (T2 DM ) and may alter cellular function. We sought to elucidate the involvement of O‐Glc NA c modification in endothelial dysfunction in patients with T2 DM . Methods and Results Freshly isolated endothelial cells obtained by J‐wire biopsy from a forearm vein of patients with T2 DM (n=18) was compared with controls (n=10). Endothelial O‐Glc NA c levels were 1.8‐ford higher in T2 DM patients than in nondiabetic controls ( P =0.003). Higher endothelial O‐Glc NA c levels correlated with serum fasting blood glucose level ( r =0.433, P =0.024) and hemoglobin A 1c ( r =0.418, P =0.042). In endothelial cells from patients with T2 DM , normal glucose conditions (24 hours at 5 mmol/L) lowered O‐Glc NA c levels and restored insulin‐mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O‐Glc NA c levels and impaired insulin action. Treatment of endothelial cells with Thiamet G, an O‐Glc NA case inhibitor, increased O‐Glc NA c levels and blunted the improvement of insulin‐mediated endothelial nitric oxide synthase phosphorylation by glucose normalization. Conclusions Taken together, our findings indicate a role for O‐Glc NA c modification in the dynamic, glucose‐induced impairment of endothelial nitric oxide synthase activation in endothelial cells from patients with T2 DM . O‐Glc NA c protein modification may be a treatment target for vascular dysfunction in T2 DM .