De novo emergence of insulin-stimulated glucose uptake in human aortic endothelial cells incubated with high glucose

Elevated glucose concentrations have profound effects on cell function. We hypothesized that incubation of human aortic endothelial cells ( HAEC) with high glucose increases insulin signaling and develops the appearance of insulin-stimulated glucose uptake by the cells. Compared with 5 mM glucose, incubation of HAEC with 30 mM glucose for up to 48 h increased in a time- dependent manner expression of insulin receptor, insulin receptor substrate ( IRS)- 1, IRS- 2, and GLUT1 proteins. High glucose also increased the specific binding of I-125-labeled insulin in HAEC accompanied by accelerated production of interleukin (IL)-6 and IL-8. Short-term stimulation by 50 mu U/ml insulin did not activate [C-14] glucose uptake by HAEC incubated in 5 mM glucose. However, an addition of insulin to high glucose-exposed endothelial cells led to a significant increase in [ 14C] glucose uptake in a glucose concentration- and time-dependent fashion, reaching a plateau at 48 h of incubation. Furthermore, incubation of HAEC with 30 mM glucose resulted in a new insulin-stimulated extracellular signal-regulated kinase-1/2 mitogen-activated protein kinase phosphorylation and increased lipid peroxidation and production of reactive oxygen species. These studies show for the first time that high glucose increases expression of insulin receptors and downstream elements of the insulin-signaling pathway and transforms "insulin-resistant" aortic endothelial cells into "insulin-sensitive" tissue regarding glucose uptake.