The IDO genetic polymorphisms and postpartum depressive symptoms: an association study in Chinese parturients who underwent cesarean section

Postpartum depressive symptoms (PDS) are not an uncommon mood disorder in postpartum women. Our previous research indicated a role for increased tryptophan (TRP) metabolism along the kynurenine pathway (KP) in the pathogenesis of PDS. Accordingly, this study was going to investigate the association of indoleamine-2,3-dioxygenase (IDO, a key enzyme of KP) genetic polymorphisms with PDS. Seven hundred twenty-five women receiving cesarean section were enrolled in this study. PDS was determined by an Edinburgh Postnatal Depression Scale (EPDS) score ≥ 13. Subsequently, 48 parturients with PDS and 48 parturients without PDS were selected for investigation of perinatal serum concentrations of TRP, kynurenine (KYN), and KYN/TRP ratio, the latter is the representative of IDO activity. In addition, seven single nucleotide polymorphisms of the IDO gene were examined. Following this genotyping, 50 parturients carrying the IDO rs10108662 AA genotype and 50 parturients carrying the IDO rs10108662 AC + CC genotype were selected for comparisons of TRP, KYN, and KYN/TRP ratio levels. This study showed the PDS incidence of 6.9% in the Chinese population, with PDS characterized by increased IDO activity (p < 0.05), versus women without PDS. We also found that the variations of IDO1 gene rs10108662 were significantly related to PDS incidence (p < 0.05). Furthermore, there was a significant difference in IDO activity between the IDO rs10108662 CA + AA, versus CC, genotypes. Our findings indicate a role of the kynurenine pathway in the development of PDS, rs10108662 genetic polymorphism resulting in changes of IDO activity might contribute to PDS pathogenesis.