Objective: A small percentage of patients do not develop any evidence of diabetic retinopathy (DR) even after many years of diabetes. Vascular endothelial growth factor (VEGF) has been implicated in the development of DR. Therefore, we sought to determine if the regulation of VEGF differs in those patients who develop DR after many years of diabetes compared with those who do not develop DR.
Research design and methods: We performed standard 7-field stereoscopic fundus photography on 95 consecutive patients with type 1 and type 2 diabetes. Patients were categorized into 3 groups according to the presence or absence of DR and the duration of diabetes: group 1 was defined by presence of DR, group 2 was defined by absence of DR after >10 years duration of diabetes, and group 3 was defined by absence of DR with long-standing diabetes (> or =20 years for type 1 diabetes and > or =15 years for type 2 diabetes). Monocytes from 40 ml peripheral blood were isolated from all patients, and the hypoxic induction of VEGF was determined in vitro.
Results: We found no significant difference in the basal level of VEGF in patients with and without DR. However, we did find a markedly significant difference in the hypoxic induction of VEGF between patients from group 1 and group 3 (4.35+/-0.55 vs. 1.87+/-0.3, P<0.00013).
Conclusions: This study suggests that 1 mechanism for the absence of DR in patients with long-standing diabetes is a decreased hypoxic induction of VEGF.