Polymorphism of the NFKB1 affects the serum inflammatory levels of IL-6 in Hashimoto thyroiditis in a Turkish population

Abstract

Hashimoto thyroiditis (HT) is a chronic inflammatory autoimmune disease of thyroid gland affected by interaction of multiple genes and various cytokines. Variants in the genes coding for the NFKB and IKB proteins can be potentially involved in the development of the inflammatory diseases. NFKB, a key transcription factor of the regulation of immune responses, is interesting candidate for association studies about autoimmune disorder. The aim of the present study was to investigate the relationship between NFKB1 and NFKBIA (NFKB1 inhibitor gene) polymorphisms, and the risk of HT in a Turkish Population in the context of IL-6 serum levels which may contribute to susceptibility to the disease. We analyzed the distribution of NFKB1-94ins/del ATTG and NFKBIA 3'UTR A→G polymorphisms using PCR-RFLP method and IL-6 serum levels using ELISA method in 120 HT patients and 190 healthy controls in Turkish population. Although, there was no statistical significant difference in distribution of the genotypes and alleles of NFKB1-94ins/del ATTG or NFKBIA 3'UTR A→G polymorphisms in patients and control subjects as single, ins/ins/GG combined genotype had protective effect on the disease when compared to ins/ins/AG combined genotype as combined genotypes of both polymorphisms. In addition to this finding, IL-6 serum levels in HT patients with del/del genotype were significantly higher than in patients with del/ins genotype (p<0.001). According to the combined genotype analysis of NFKB1-94ins/del ATTG and NFKBIA 3'UTR A→G polymorphisms, IL-6 levels were also higher in patients with del/del genotype when at least one G allele existing (p=0.007). Therefore, our findings suggest that the functional promoter NFKB1-94ins/del ATTG polymorphism was significantly associated with population HT disease through acting by directly modulating IL-6 serum levels.

Keywords: ELISA; Hashimoto thyroiditis; IL-6; NFKB1; NFKBIA; PCR-RFLP; Polymorphism.