In endothelial cells from patients with T2DM, normal glucose conditions (24 hours at 5 mmol/L) lowered O‐GlcNAc levels and restored insulin‐mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O‐GlcNAc levels and impaired insulin action. The gene discussed is NOS3; the disease is type 2 diabetes mellitus.