The Tyr113His T/C rs1051740 and 'very slow' phenotype of the EPHX1 gene alters miR-26b-5p and miR-1207-5p expression in pregnancy

BackgroundEnvironmental insults and microsomal epoxide hydrolase 1 (EPHX1) single nucleotide polymorphisms (SNPs), Tyr113His T/C rs1051740 and His139Arg A/G rs2234922, aberrantly alters microRNA (miR) expression and are linked to low birthweights (LBW).ObjectivesTo investigate the interplay between pollution, EPHX1 SNPs and miRs during pregnancy and associated LBW outcomes.MethodsSouth African pregnant women (n = 241) were recruited in the MACE birth cohort study in Durban, a city with high levels of industry and traffic related pollutants. EPHX1 SNPs were genotyped using PCR-RFLP and grouped into their respective phenotypes, i.e. normal (N), slow (S), very slow (VS) and fast (F). EPHX1, miR-26b-5p, miR-193b-3p and miR-1207-5p expression were determined using quantitative PCR.ResultsMothers with the Tyr113His SNP had low iron levels [TT vs. TC + CC: mean difference (MD) = 0.67 g/dl; p = 0.0167], LBW [TT vs. TC + CC: MD = 189.30 g; p = 0.0067], and low EPHX1 expression; p < 0.0001. miR-26b-5p and miR-1207-5p expression were significantly higher in the CC genotypes compared to TT + TC groups; p < 0.0001. The opposite trend occurred for miR-193b-3p; p = 0.0045. Mothers with the VS phenotype had low iron levels [N vs. VS and VS vs. F: MD = 2.03 and − 1.96 g/dl; p = 0.0021, respectively], decreased gestational age [VS vs. F: MD = − 2.14 weeks; p = 0.0051, respectively], and LBW [N vs. VS, VS vs. F and S vs. VS: MD = 1000, − 940.30 and 968.80 g; p < 0.0001, respectively]; F phenotype had the highest EPHX1 expression [N vs. F, VS vs. F and S vs. F: MD = − 1.067, − 1.854 and − 1.379; p = 0.0002, respectively]; and N phenotype had low miR-26b-5p [N vs. VS: MD = − 0.6100; p = 0.0159] and miR-1207-5p [N vs. VS and VS vs. F: MD = − 0.834 and 1.103; p = 0.0007, respectively] expression. miR-193b-3p expression between phenotypes remained unchanged.ConclusionThe Tyr113His T/C variant of rs1051740 and VS phenotype alters EPHX1, miR-26b-5p and miR-1207-5p expression, and contributes towards low blood iron levels and LBW.