To investigate the relationship between apolipoprotein E (ApoE) gene polymorphism and diabetic retinopathy (DR) and plasma lipid levels in type 2 diabetes mellitus (T2DM).

A case-control study was conducted, including 112 patients with T2DM complicated by DR (DR group) and 96 patients with T2DM without DR (T2DM group), who were admitted to Xuzhou No.1 People′s Hospital between January 2022 and May 2024. The ApoE gene polymorphisms were detected using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The genotypes and allele frequencies between the two groups were compared using the chi-square test or Fisher′s exact test, while analysis of ANOVA was performed to compare serum lipid levels among patients with different genotypes. Logistic regression analysis was applied to identify risk factors associated with the development of DR in patients with T2DM.

By comparison, the total cholesterol (TC) level [(5.02±0.98)mmol/L] and triglyceride (TG) level [(2.92±1.07)mmol/L] in the DR group were higher than those of the T2DM group [(4.51±1.33)mmol/L, (2.36±0.25)mmol/L]. The overall distributions of ApoE genotypes and alleles differed significantly between the two groups (all P<0.01). After Bonferroni correction, significant differences were observed in the distributions of the ε3/3, ε3/4, and ε4/4 genotypes between the DR and T2DM groups (all P<0.0083). The frequencies of the ApoE ε3 and ε4 alleles in the DR group were significantly lower than those in the T2DM group (all P<0.0167). There were differences in TC and TG levels among patients with different alleles of ApoE in the DR group (F=3.429, 4.947, all P<0.05). Logistic regression analysis indicated that TC (OR=1.467, 95%CI: 1.080-1.993), TG (OR=2.761, 95%CI: 1.756-4.342), and ApoE ε4 allele (OR=0.056, 95%CI: 0.018-0.176) were all independent risk factors for the development of DR in patients with T2DM (all P<0.05).

The TC, TG, and ApoE ε4 alleles in lipid levels are strongly associated with T2DM complicated with DR and may be one of the major factors in its pathogenesis.