von Willebrand factor and retinal circulation in early-stage retinopathy of type 1 diabetes

OBJECTIVE - Although retinopathy is a common microvascular complication of type 1 diabetes, the mechanism for this complication is still unknown. Changes in retinal, circulation have been noted before the development of overt retinal pathology, Because von Willebrand factor (VWF) is a marker for endothelial dysfunction and mediates platelet adhesion, we determined if there was an association between VWF and retinal. circulation in the early stages of diabetic retinopathy. RESEARCH DESIGN AMID METHODS - Twenty subjects (aged 32.4 +/- 7.8 years) with type 1 diabetes and minimal or no retinopathy were studied. The mean duration of diabetes was 4.7 +/- 2.6 years. Data were collected at baseline and after 4 months of 1,800 IU vitamin E therapy or placebo. Retinal circulation was evaluated by video fluorescein angiography. Plasma vWF antigen levers were measured by enzyme-linked immunosorbent assay and fibrinogen by the Clauss method. RESULTS - Retinal blood flow was negatively correlated with vWF levels (r = -0.44 P = 0.008), whereas retinal circulation time was positively correlated with vWF levels (r = 0.33, P = 0.048). Fibrinogen levels were not significantly associated with either retinal index. How ever, fibrinogen levels were positively associated with HbA(1c) levels (r = 0.34, P = 0.01), indicating an association between poor glycemic control and higher fibrinogen levels. CONCLUSIONS - Increased vWF was associated with a prolonged retinal circulation time and reduced retinal blood flow in early-stage retinopathy of type 1 diabetes. Reduced blood flow associated with increased vWF levels may promote stasis in the retinal circulation and lead to local hypoxemia. These changes might contribute to the microvascular complications of diabetes. Whether the VWF levels predict retinal complications deserves further investigation.