Effects of high glucose and different concentrations of insulin on the proliferation of vascular smooth muscle cells

Objective To explore the effect of high glucose and different concentrations of insulin on the proliferation of vascular smooth muscle cells(VSMCs) and the underlying mechanisms.Methods The primary cultures of VSMCs were derived from the thoracic aortae of Wistar rat.The proliferation of VSMCs was induced by high glucose and different concentrations of insulin.The VSMCs were divided into a control,a high glucose,high glucose plus different concentrations of insulin groups.The proliferation of VSMCs was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay.The expression of proliferating cell nuclear antigen(PCNA) protein in VSMCs was determined by immunocytochemistry techniques.The expression of PCNA mRNA and the content of nitric oxide(NO) was measured by RT-PCR and commercial available kit,respectively.Results High glucose could induce the proliferation of VSMCs,an effect which was enhanced by the insulin in a dose-dependent manner.The maximum effect of insulin was on the 5th day at the concentration of 300 mU/L.High glucose treatment increased the content of PCNA protein accompanied by the increased mRNA expression,which was enhanced by combination with insulin(300 mU/L).High glucose treatment significantly reduced the content of NO,an effect which was enhanced by combination with insulin(300 mU/L).Conclusion Insulin is able to induce the proliferation of VSMCs in a dose-dependent manner,which is related to increasing the PCNA expression and reducing the NO production,and insulin and high glucose show a synergistic reaction.