Brain-Derived Neurotrophic Factor Val66Met Polymorphism and Its Synergism with L/S Polymorphism in the Promoter Region of Serotonin Transporter in Bipolar I Disorder Patients in Western Iran

Abstract

Background: Brain-derived neurotrophic factor (BDNF) might involve in the pathogenesis of mental disorders. There are inconsistent reports related to the role of BDNF Val66Met in susceptibility to bipolar disorder (BD). Objectives: The aim of the present study was to investigate the role of BDNF Val66Met and its synergism with 5-HTT gene-linked polymorphic region (5-HTTLPR) variants in susceptibility to bipolar I disorder (BP-I) in Western Iran. Materials and Methods: In this case-control study, 153 patients with BP-I and 146 age- and gender-matched healthy individuals were investigated for BDNF and 5-HTTLPR variants using PCR-RFLP method. Results: The frequency of BDNF A (Met) allele in patients (17.7%) was slightly lower than that in controls (19.9%, P = 0.5). The concomitant presence of BDNF G (Val) and 5-HTTLPR S alleles tended to increase the risk of BP-I by 1.41 times (P = 0.064) compared to the combined presence of BDNF G and 5-HTTLPR L alleles. Also, interaction between BDNF G (Val) and 5-HTTLPR S tended to increase the risk of BP-I by 1.28-fold (P = 0.062) compared to the concomitant presence of BDNF A and 5-HTTLPR S alleles. Conclusions: This study, conducted for the first time on Kurdish population in Western Iran, did not indicate any association between BDNF Val66Met with BP-I. However, the interaction between BDNF and 5-HTTLPR variants tended to increase the susceptibility to BP-I.