The influence of common gene variants of the xenobiotic receptor (PXR) in genetic susceptibility to intrahepatic cholestasis of pregnancy

Abstract

The xenobiotic nuclear pregnane X receptor is implicated in many physiological pathways and diseases, including bile acid detoxification and cholestasis. Aim: To estimate the contribution of common gene variants of the xenobiotic receptor (pregnane X receptor, PXR) to genetic susceptibility to intrahepatic cholestasis of pregnancy. Methods: A total of 101 intrahepatic cholestasis of pregnancy patients and 171 healthy pregnant women in the third trimester of their pregnancies were included. Four tag single nucleotide polymorphisms (SNPs) (rs12488820 C⁄T, rs2472671 C⁄T, rs2461823 A⁄G, and rs1054191 A⁄G) encompassing 36 kb in chromosome 3, with a minor allele frequency ‡0.10 and representing 33 polymorphic sites were genotyped. Besides these, three additional SNPs (rs3814057, rs6785049, and rs7643645) were included because they showed previous evidence of functionality. Results: Genotypic test for single SNPs showed that rs2461823 genotypes were significantly associated with intrahepatic cholestasis of pregnancy (P < 0.0069), OR per G allele: 1.44, 95% CI: 1.01–2.05, P < 0.042. The Cochran-Armitage test for trend and the allelic test showed a significant association with disease status (P < 0.04 and 0.03 respectively), G being the risk allele. A positive association between rs2461823 and ALT, AST, and bilirubin concentrations was observed. Neonate birth weight adjusted by the Capurro index was significantly associated with rs2461823 (P < 0.05); the proportion of the total variation attributed to rs2461823 genotypes was 7.8%. Conclusion: Common PXR polymorphisms may contribute to the genetic susceptibility to intrahepatic cholestasis of pregnancy.