TNF-α-308 G/A variant may be associated with bipolar disorder in a Turkish population

Abstract

Background: Tumor necrosis factor alpha (TNF-α) is a proinflammatory multifunctional cytokine produced by macrophages. A dysregulation of the immune system contribute to the pathogenesis of bipolar disorder (BD). In this study, we aimed to investigate the relationship between the TNF-α gene -308G/A promoter variant and the risk of BD. Methods: A total of 104 BD patients and 94 healthy controls were enrolled in the study. Genomic DNA was isolated and TNF-α -308G/A variant was analyzed using PCR-RFLP method. Results: TNF-α -308G/A variant GG genotype and G allele were more prevalent in BD patients compared to the controls (p = 0.002 and p = 0.017, respectively). The patients carrying GG genotype had a 5.927-fold higher risk of developing BD. Then, we divided patients into two groups as smokers and non-smokers. TNF-α -308G/A variant GA genotype was higher in non-smoker BD patients than smoker patients (p = 0.027). We found that TNF-α -308G/A AA genotype and A allele increased in smoker patients compared to non-smoker patients (p = 0.008, p = 0.002, respectively). Discussion: Our results provided evidence that TNF-α -308G/A variant may contribute to development of BD in a Turkish cohort. In addition, this variant plays a relevant role in the smoker status of BD.