ABSTRACT
Neovascularization is the hallmark of proliferative diabetic retinopathy but its exact pathogenesis is still undefined. Recently, leptin was shown to possess an angiogenic action in vitro and to induce neovascularization in vivo. The present study was conducted to investigate the possible relation between serum leptin levels and diabetic retinopathy especially the proliferative form.The study included 50 patients with type 2 diabetes mellitus [22 males, 28 females, mean age 52.88 +/- 4.85 years, body mass index [BMI] 27.31 +/- 3.2 kg/m[2], and waist/hip ratio, 0.84 +/- 0.23]. They were classified into three groups according to the stage of their diabetic retinopathy [20 without retinopathy, 17 with nonproliferative retinopathy, and 13 with proliferative retinopathy]. In addition, 15 apparently healthy subjects who matched with the diabetic patients for age, sex, BMI and waist/hip ratio served as controls. All participants were subjected to full history taking, thorough clinical examination, ECG, echocardiography, direct and indirect ophthalmoscopy, and the following laboratory investigations: fasting blood glucose, glycosylated hemoglobin, blood urea, serum creatinine, detection of microalbuminuria, lipid profile, and serum leptin that measured with immuunoradiometric assay. No significant difference in the mean level of serum leptin was found between diabetic patients and control subjects. In patients with proliferative retinopathy, the mean level of serum leptin [18.27 +/- 0.88 ng/ml] was significantly higher than that in patients with nonproliferative retinopathy [11.96 +/- 1.08 ng/ml, P< 0.001] or patients without retinopathy [7.17 +/- 1.18 ng/ml, P< 0.001]. Also, patients with nonproliferative retinopathy had significantly higher leptin level than patients without retinopathy [P<0.001]. Serum leptin levels were strongly correlated with BMI in diabetic patients [r=0.77, P< 0.001]. The differences in leptin levels between the groups of diabetic patients were still significant after adjusting leptin level for BMI. The estimated threshold of serum leptin for diabetic retinopathy was 8.7 ng/ml. In conclusion, the more advanced the diabetic retinopathy, the higher the serum leptin levels, even after adjusting the levels for BMI. With recently observed role of leptin in promotion of angiogenesis, the possibility that leptin may play a role in diabetic retinopathy especially the proliferative form can not be excluded. Further studies are needed to confirm this possibility