IGF1 gene polymorphisms associated with diabetic retinopathy risk in Chinese Han population

Abstract

Objective: This study aimed to explore the association of insulin-like growth factor 1 gene (IGF1) polymorphisms with diabetic retinopathy (DR) in a Chinese Han population.

Methods: Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for genotyping. Genotype frequencies were compared by chi-square test. Odds ratio (OR) with 95% confidence interval (95%CI) was calculated to express the risk intensity of DR. Linkage disequilibrium between IGF1 polymorphisms was analyzed by Haploview. Serum IGF1 concentration was measured by enzyme-linked immunosorbent assays (ELISA) and assessed by student's t test.

Results: AG genotype of rs6218 and TT genotype of rs35767 were significantly associated with the elevated risk of DR (rs6218: OR=1.77, P=0.04; rs35767: OR=2.32, P=0.03) and type II diabetes mellitus (T2DM) (rs6218: OR=1.92, P=0.00. rs35767: OR=2.29, P=0.02). Only T allele of rs35767 significantly increased the risk of DR (OR=1.45, P=0.04), however, rs6218 (OR=1.92, P=0.00), rs35767 (OR=0.02, P=0.02) and rs5742612 (OR=2.21, P=0.04) showed obvious association with T2DM. Haplotypes were only associated with T2DM, but not DR. Minor allele homozygote of rs35767 was obviously correlated with serum IGF1 level.

Conclusion: IGF1 rs6218 and rs35767 polymorphisms contribute to the risk of DR. IGF1 rs35767 polymorphism may participate in the regulation of serum IGF1 concentration in DR.

Keywords: IGF1; diabetic retinopathy; haplotype; serum concentration; t2dm.

Figure 1. Serum concentration of IGF1 in DR, DNR and healthy control

Compared with the healthy controls, serum concentration of IGF1 was significantly increased in DR and DNR groups (P<0.01 for both). Moreover, DR exhibited obviously increased serum IGF1 concentration compared to the DNR group (P<0.01). ^**: indicated P<0.01.

Figure 2. Association between IGF1 polymorphisms and serum IGF1 concentration in DR

Analysis result demonstrated that serum IGF1 concentrations didn't show significant difference between any two genotypes of rs972936, rs6218, or rs5742612 polymorphisms. Obvious higher serum IGF1 concentration was found in TT, compared with CT and CC genotypes carriers. Moreover, serum concentration of IGF1 was similar between CC and CT genotype carriers (P=0.0748). ^**: suggested P<0.01.