Predictive value of the TNF-α-rs1800629 polymorphism in bipolar disorder: A case-control study and a meta-analysis

Background: Genetic and inflammatory factors play a role in bipolar disorder (BD). This study was conducted to assess the relationship between tumour necrosis factor-alpha (TNF-alpha)-308G/A polymorphism and the susceptibility to bipolar I disorder in a sample of the Iranian population. Furthermore, the aim of the present meta-analysis was to provide evidence indicating the predictive value of the rs1800629 for BD in the world, based on all available published data. Methods: Genotyping of 95 samples was carried out by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). To set a meta-analysis study, relevant studies, containing information on TNF-alpha-rs1800629 polymorphism and the risk of BD, were explored. Statistical analysis was performed using SPSS 16.0 and Meta-Essentials. Results: The genotype and allele distribution did not indicate any association with BD in our samples. Moreover, there was no significant difference in dominant [p = 0.999] and recessive [p = 0.882, OR = 0.91 (0.25-3.23)] models. Findings did not also vary after adjustment for confounders. Pooled data consisted of 967 cases and 1705 controls and represented no significant association between rs1800629 and BD in all genetic models. However, GG genotype was associated with the 62% lower risk of the disease compared to the AA genotype [p = 0.017, OR = 0.48 (0.22-1.06)]. Conclusions: These findings cannot support the predictive value of rs1800629 as a biomarker of BD risk. However, it is suggested to evaluate its association with gene expression in functional studies and its haplotype with gene region variations.