Interleukin-4 (IL-4) is a multifunctional cytokine; involved in the regulation of immune responses, as well as in the pathogenicity of many diseases, such as diabetes mellitus. Some researchers suggested that IL-4 protects the human pancreatic islet from cytotoxic damages, whereas others suggested some inhibitory actions of IL-4 on pancreatic islets. This study aimed to assess the role of IL-4 genotypes of intron 3 variable number of tandem repeats of the IL-4 gene in diabetic retinopathy and diabetic neuropathy in Sudanese patients with type 2 diabetes mellitus (T2DM). This case–control study was performed in a number of Khartoum state hospitals in Sudan. The study enrolled 181 Sudanese patients, 115 (57 females and 58 males) diagnosed with T2DM and 66 (29 females and 37 males) healthy persons who served as control subjects. Polymerase chain reaction was used for the analysis of IL-4, which was amplified using the following amplification sequence (forward primer: CACGACGTTGTAAAACGACTAGGCTGAAAGGGGGAAAGC; reverse primer: CTGTTCACCTCAACTGCTCC). Biochemical analyses for highly sensitive C- reactive protein (hs-CRP), glycated hemoglobin (HbA1c), fasting plasma glucose, total cholesterol, triglycerides, low-density lipoprotein, and high-density lipoprotein were performed using a chemical analyzer.
The study showed that in the diabetic group, 49(42.6%) had diabetic retinopathy, whereas 7(6.1%) had diabetic neuropathy. The B1B1 genotype was found to be a higher risk factor for developing diabetic retinopathy than B2B2 [P = 0.028; Odds ratio (OR) = 1.381; 95% confidence interval (CI) 1.344–9.062], whereas the B1B2 genotype was found to be insignificantly associated with retinopathy (P = 0.357; OR = 1.570; 95% CI 0.654–3.887). Furthermore, hs-CRP and HbA1c were significantly increased in diabetic neuropathy with IL-4 B1B1 genotype.
IL-4 gene polymorphisms can be good markers for the early identification of risk for diabetic retinopathy and neuropathy in Sudanese people. The hs-CRP and HbA1c in diabetic patients with IL-4 B1B1 genotype may be predisposition predictors of diabetic neuropathy.