Concomitant expression and combined localization of visfatin and vascular endothelial growth factor in retinas of diabetic rats

Abstract

Background Diabetic retinopathy (DR) is one of the most important microvascular complications of diabetes,which has become one of the leading causes of blindness.Neovascularization is the main pathological manifestations of DR,but its mechanism is unknown.There is a clear need to investigate its pathogenesis which can offer potential therapeutic targets.Objective The aim of this study was to investigate the expression and distribution of visfatin and vascular endothelial growth factor (VEGF) in diabetic model rats.Methods This study was approved by Animal Ethic Committee of Inner Mongolia Medical University.Sixty SPF 8-week-old male SpragueDawley rats were randomized into the diabetic group and control group.The rats were housed under a condition that alternated between 12 hours of light and darkness,with free access to rat food and water.Diabetes was induced by intraperitoneal injection of 60 mg/kg (0.60 ml/100 g) of streptozotocin (STZ) and control rats received equivalent volume of buffer.The models were regarded as successful when blood glucose was ≥ 16.7 mmol/L.Rats were sacrificed 12 weeks after the injection of STZ and retinal specimens were prepared to detect the expression of visfatin and VEGF.Total retinal protein was isolated from the retinas of experimental and control eyes,and the expression of visfatin and VEGF was assessed by Western blot.Frozen cross sections of retinas of 5 μm thickness were used to perform double immunofluorescence staining with anti-visfatin and anti-VEGF antibodies.Results Mean body weight of the diabetic rats was (189.02±11.34) g and that of the control rats was (489.57 ± 14.48) g at 12 weeks post-injection,showing a significant difference between them (t =5.236,P =0.003).Mean blood glucose level was (29.25±3.86) mmol/L in the diabetic group and (5.32±1.01) mmol/L in the control group,demonstrating a significant difference (t =11.778,P =0.000).Double immunofluorescence staining showed reduced expression of visfatin and VEGF in the retinal nerve fibrous layer and glial cells in the control rats.A stronger staining for visfatin and VEGF was found in the various layers of the retina in the diabetic rats,with an expression level of visfatin (A value) of 346.26±41.23,which was considerably higher than that of the control group (102.07±65.01) (t =8.291,P =0.000) in 12 weeks after injection.Furthermore,the expression of VEGF in the retina was elevated in the diabetic group compared with the control group (A value) (415.88±92.15 vs.113.06±32.06) (t=10.067,P=0.000).Conclusions Visfatin might contribute to the pathologic progression of diabetic retinal,neovascularization and it might play a synergistic role with VEGF in the pathophysiology of DR. Key words: Visfatin; Vascular endothelial growth factor; Diabetic retinopathy; Double immunofluorescence stain; Western blot