Diabetic Retinopathy and IGF-1 Gene Polymorphic Cytosine-Adenine Repeats in a Southern Indian Cohort

Abstract

Background/Aims: Growth factors have been implicated in the pathogenesis of diabetic retinopathy (DR). IGF-1 is known to trigger a critical cascade of molecular events that initiate retinal angiogenesis. Increased vitreous IGF-1 levels have been correlated with the severity of ischemia-associated diabetic retinal neovascularization. In the present study, a cytosine-adenine (CA)_n repeat in the promoter of the IGF-1 gene is studied for association with DR. Methods: A total of 127 patients with retinopathy (cases: DR+) and 81 patients without retinopathy (controls: DR–) who had type 2 diabetes were recruited for the study. Patients underwent detailed clinical examination and DR was graded based on stereoscopic digital fundus photographs. Frequencies of alleles and genotypes between the two groups were analyzed for significance using relevant statistical tests. (CA)₁₇ and (CA)₁₈ repeats were the more frequent alleles. Results: The frequency of the 18-repeat genotype was significantly higher in DR+ patients when compared to DR– patients and found to confer a 2.4 times (95% CI: 1.2–5.0) and 2.8 times (95% CI: 1.1–7.5) higher risk for developing DR and proliferative DR, respectively, when compared to <18-repeat genotypes. Conclusions: Our study suggests that the 18-repeat genotype is a susceptibility genotype for DR and its clinical severity in a Southern Indian cohort.