Effect of insulin on VEGF expression in bovine retinal microvascular endothelial cells exposed to normal or high glucose

Abstract

To investigate the effect of insulin or (and) high glucose on the vascular endothelial growth factor (VEGF) expression in bovine retinal microvascular endothelial cells (BREC). It was a experimental study. BREC were cultured with selective culture media. Passaged cells were cultured in normal (5 mmol/L) or high glucose (30 mmol/L) medium for 3 days. Equimolar mannitol was supplemented for osmotic controls. Cells were serum-deprived overnight in Dulbecco's modified Eagle's medium containing 0.2% w/v bovine serum albumin and then incubated in the absence or presence of 100 nmol/L insulin for 24 hrs. Cells were harvested and the expression of VEGF mRNA was analyzed by Real-time PCR. VEGF protein level was determined by HUVEC proliferation assay, immunofluorescence and western-blot Insulin or (and) high glucose significantly increased VEGF mRNA (F = 5.67, 9.04; P <0.05) and protein (F = 5.50, 5.57; P <0.05) expression. However, the combined effect of insulin and high glucose is weak in contrast to insulin or high glucose alone. High glucose attenuated insulin-induced VEGF expression. Therefore, VEGF may be not the major factor that lead to transient worsening of diabetic retinopathy after acute insulin therapy in diabetes.