High glucose concentration produces a short-term increase in pERK1/2 and p85 proteins, having a direct angiogenetic effect by an action similar to VEGF.

Excessive glucose serum concentration, endothelial dysfunction and microangiopathy are key features of diabetes mellitus, being both diagnostic parameters and pathogenetic mechanisms. Vascular endothelial growth factor (VEGF) is importantly implicated in the physiology and pathology of blood vessels, including diabetic vascular damage. These factors certainly affect endothelial cells, and to evaluate mechanisms involved, we took advantage of telomerase-immortalized human microvascular endothelial (TIME) cells. TIME cells were exposed to different glucose concentrations and to VEGF treatments. Culture conditions also included the use of basement membrane extract, as an in vitro differentiation model. Cell morphology was then evaluated in the different conditions, and cellular proteins were extracted to analyze specific protein products by Western blot. High glucose concentrations and VEGF did substantially affect neither morphology nor growth of cultured TIME cells, while both considerably increased differentiation into "capillary-like" structures when cells were cultured on basement membrane extract. Under these conditions, high glucose concentration and VEGF also produced a short-term increase in pERK1/2 and p85 proteins, while total and phosphorylated AKT were not affected. These data suggest a direct angiogenetic effect of glucose, affecting intracellular transduction mechanisms with an action similar to that of VEGF. This effect on endothelial cell proliferation and differentiation could be part of pathogenetic mechanisms producing diabetic microvascular alterations.