Association of Interleukin 13 rs20541 Gene Polymorphism and Serum Periostin with Asthma and Allergic Conjunctivitis Among Egyptian Patients

Abstract

Background: Single nucleotide polymorphisms (SNPs) in the interleukin 13 (IL13) gene are associated with vulnerability to allergic diseases, such as asthma and allergic conjunctivitis (AC). Periostin, as an IL13-induced protein, has emerged as a novel biomarker in several allergic diseases. Data among Egyptian patients are still scarce.

Aim: To find out the association of IL13 rs20541 gene polymorphism and serum levels of periostin with asthma and AC among Egyptian patients.

Patients and methods: Eighty-one Egyptian allergic patients with asthma, AC, and both asthma and AC (27 each), were enrolled in this case-control study. Twenty-seven age and gender-matched healthy volunteers served as controls. All participants were tested for IL13 rs20541 SNP by real-time polymerase chain reaction, TaqMan method. Serum levels of periostin and IL13 were assessed by ELISA.

Results: Compared to healthy subjects, asthmatic patients had a higher frequency of the homozygous adenine/adenine (AA) genotype at IL13 rs20541 SNP (14.8% vs 3.7%) and a lower frequency of the guanosine/guanosine (GG) genotype (51.9% vs 55.6%), while AC patients had higher GG genotype (70.4% vs 55.6%) with no AA genotype detected, yet no significant difference was noticed (p = 7.053). A significantly higher serum periostin in asthmatic patients compared to controls was found (p = 0.005). Higher levels of serum periostin, although nonsignificant, were recorded in AC patients compared to controls (22.88 ± 10.01ng/mL and 17.51 ± 3.17ng/mL, respectively). Periostin was significantly higher in patients with IL13 AA and GA genotypes compared to those with GG genotype (p = 0.016). A significant positive correlation between serum periostin and serum IL13 among allergic patients was recorded (r = 0.352, p < 0.001).

Conclusion: Among Egyptian patients, serum level of periostin is significantly associated with asthma and positively correlates with IL13 level supporting its utility as a diagnostic biomarker. IL13 rs20541 gene polymorphism does not seem to play an obvious role in asthma and AC, which requires further evaluation.

Keywords: IL13 rs2054; allergic asthma; allergic conjunctivitis; periostin.

Figure 1

Allelic discrimination plot showing the results of IL13 rs20541 SNP genotyping by real-time PCR in 48 examined allergic patients. Blue dots correspond to the homozygous GG genotype (28 patients), green dots correspond to the heterozygous AG genotypes (17 patients), and red dots correspond to the homozygous AA genotype (3 patients). The X-axis represents the fluorescence of allele A while the Y-axis represents that of allele G. Different colors correspond to different fluorescent dyes used in the reaction; FAM (blue), ROX (red), and VIC (green).

Figure 2

A scattered plot curve shows a significant positive correlation (r=0.352, p<0.001) between serum level of periostin and serum level of IL13 among the examined allergic patients (n=81).