Background: Vascular endothelial growth factor (VEGF) is involved in endothelial dysfunction in hypertension and diabetes. It may play a role in the pathogenesis of diabetic nephropathy and retinopathy. Other various growth factors were found to be involved in the neovascularization in proliferative diabetic retinopathy including insulin like growth factor -1 (IGF-1) but most of the studies have measured only a single growth factor especially in the vitreous fluid, thus ignoring any potential inter-relationship between levels of different growth factors.
Objective: To study the possible changes in the levels of IGF-1 and VEGF in different vascular status in diabetic patients. Secondly, based on the genetic predisposition for the vascular changes, it would be beneficial to compare the basal IGF-1, and VEGF levels in prediabetic and normal control subjects.
Study design: This study was conducted on 66 subjects: 12 diabetic patients with diabetic retinopathy (DR), 12 diabetic patients with nephropathy (DN), 12 diabetic patients with ischemic heart disease (IHD), 12 subjects with impaired glucose tolerance (IGT), 12 control subjects and 6 non-diabetic IHD patients. Vitreal fluid samples were taken from each patient with DR and each control subject during vitrectomy. Blood sample was taken from each subject of the study and we assessed their clinical condition, several laboratory and radiological investigations including measurement of VEGF and IGF-l in both serum and vitreal fluid.
Results and conclusions: Vitreal levels of VEGF (4.25±l.88 ng/dl) and IGF-I (42.82±l2.79 ng/dl) are higher in the diabetic patients than the control (1.03±l.67 and 29.89±21.23 ng/dl). Vitreal levels of VEGF were higher than the corresponding serum level (2.23±l.008 ng/dl) indicating that local production is the main mechanism. Vitreal levels of IGF-l were lower than the corresponding serum level (358.74±97.89 ng/dl), with a positive correlation indicating that serum diffusion is the main mechanism. Insignificant change in the serum levels of VEGF and IGF-l in patients with diabetic nephropathy (2.88±l.09 and 398.59±l65.90 ng/dl) than the control indicating that regional production of growth factors may be more important than their serum concentration. Low serum levels of VEGF and lGF-l (1.04± and 343.67±210.61 ng/dl) are cofactors for the development of advanced myocardial ischemia. IGT group also have low serum IGF-l (319.75±l14.45 ng/dl), so the spark of diabetic complications might occur early in the natural course of diabetes. Serum levels of VEGF and IGF-l are unrelated, although several studies based on the molecular levels reveal a relation, reflecting again that regional production and existence is more important.