Maternal selenium status in pregnancy, offspring glutathione peroxidase 4 genotype, and childhood asthma
Authors: Seif O. Shaheen, Clare M. Rutterford, Sarah J. Lewis, Susan M. Ring, John W. Holloway, Jean Golding, A. John Henderson
Journal: Journal of Allergy and Clinical Immunology (2014)

Two prospective birth cohort studies have suggested that prenatal selenium status may play a role in the inception of childhood asthma. In the Avon Longitudinal Study of Parents and Children (ALSPAC), umbilical cord tissue concentration of selenium was negatively associated with risk of wheezing in early childhood1Shaheen S.O. Newson R.B. Henderson A.J. Emmett P.M. Sherriff A. Cooke M. et al.Umbilical cord trace elements and minerals and risk of early childhood wheezing and eczema.Eur Respir J. 2004; 24: 292-297Crossref PubMed Scopus (136) Google Scholar; in another United Kingdom cohort, maternal and cord plasma selenium concentrations were negatively associated with wheezing in the second year of life, but not at 5 years.2Devereux G. McNeill G. Newman G. Turner S. Craig L. Martindale S. et al.Early childhood wheezing symptoms in relation to plasma selenium in pregnant mothers and neonates.Clin Exp Allergy. 2007; 37: 1000-1008Crossref PubMed Scopus (63) Google Scholar Associations between biomarkers of prenatal selenium exposure and asthma and wheezing later in childhood have not been reported. Glutathione peroxidase (GPX) 4 is a unique membrane-associated selenium-dependent antioxidant enzyme that can directly reduce phospholipid hydroperoxides and protect against oxidative stress in mammalian cells.3Imai H. Nakagawa Y. Biological significance of phospholipid hydroperoxide glutathione peroxidase (PHGPx, GPx4) in mammalian cells.Free Radic Biol Med. 2003; 34: 145-169Crossref PubMed Scopus (598) Google Scholar Aside from its antioxidant role, GPX4 has been implicated in lipoxygenase metabolism,4Villette S. Kyle J.A. Brown K.M. Pickard K. Milne J.S. Nicol F. et al.A novel single nucleotide polymorphism in the 3′ untranslated region of human glutathione peroxidase 4 influences lipoxygenase metabolism.Blood Cells Mol Dis. 2002; 29: 174-178Crossref PubMed Scopus (90) Google Scholar which has major relevance to leukotriene synthesis and inflammatory signaling in asthma. Thus, demonstration of an interaction between selenium status and GPX4 genotype on asthma risk could strengthen the evidence for a causal role of selenium. In the ALSPAC birth cohort, we investigated whether higher maternal blood concentration of selenium in pregnancy is associated with a lower risk of asthma and wheezing at age 7 years and whether associations are modified by the GPX4 genotype (rs713041). Details of the ALSPAC protocol can be found at http://www.alspac.bris.ac.uk. Methods for maternal selenium analysis have been described in detail previously5Golding J. Steer C.D. Hibbeln J.R. Emmett P.M. Lowery T. Jones R. Dietary predictors of maternal prenatal blood mercury levels in the ALSPAC birth cohort study.Environ Health Perspect. 2013; 121: 1214-1218Crossref PubMed Scopus (70) Google Scholar; whole blood samples were obtained from 4484 women as early as possible in pregnancy, and selenium analysis was performed by the Centers for Disease Control and Prevention, Atlanta, Georgia, in 2009-2010. After excluding assay failures, selenium measurements were complete for 4287 women. The mean (interquartile range) of the gestational timing of blood samples was 11.7 (9-13) weeks (median, 11 weeks; range, 2-42 weeks). Maternal blood selenium concentrations were log transformed for analysis. Children were defined as having current doctor-diagnosed asthma at 7.5 years if mothers responded positively to the question "Has a doctor ever actually said that your study child has asthma?" and positively to questions about wheezing and/or asthma in the past 12 months at 7.5 years. A single nucleotide polymorphism (SNP) in GPX4 (rs713041, at position 718) was typed by LGC Genomics Ltd (Hoddesdon, Herts, United Kingdom; www.lgcgenomics.com) in mothers and children using a competitive allele-specific PCR system (KASPar). Maternal and child GPX4 genotype frequencies did not deviate from Hardy-Weinberg equilibrium. All analyses were restricted to white mothers and their offspring. The median blood selenium concentration was 110.37 μg/L (range, 27.4-324.07 μg/L); the arithmetic mean was 113.82 ± 24.53 μg/L. The 20% centile concentration was 96 μg/L, which approximates to the whole blood concentration of 100 μg/L needed to saturate glutathione peroxidase activity in adults in vivo.6Thomson C.D. Robinson M.F. Butler J.A. Whanger P.D. Long-term supplementation with selenate and selenomethionine: selenium and glutathione peroxidase (EC 1.11.1.9) in blood components of New Zealand women.Br J Nutr. 1993; 69: 577-588Crossref PubMed Scopus (192) Google Scholar After controlling for confounders, including gestational timing of maternal blood samples (see this article's Online Repository at www.jacionline.org for the full list), it was found that maternal blood selenium concentration was not associated with childhood asthma (N = 2298) or wheezing (N = 2326) overall (see Table E1 in this article's Online Repository at www.jacionline.org), nor was maternal or child GPX4 genotype associated with these outcomes (see Table E2 in this article's Online Repository at www.jacionline.org). Table I presents the adjusted associations between maternal blood selenium concentrations and asthma and wheezing, stratified by maternal and child GPX4 genotypes. Maternal genotype did not modify the associations. However, there was evidence of interaction between maternal selenium status and child GPX4 genotype on asthma (P interaction .068) and wheezing (P interaction .011), with an odds reduction of 83% to 84% per doubling increase in blood selenium concentration in children who were homozygous for the minor T allele of rs713041; maternal blood selenium concentration was not associated with these outcomes in children carrying the C allele. Similarly, children of mothers below the 20th centile for blood selenium concentration were more likely to have asthma than were children of mothers with higher blood selenium concentration if they were homozygous for the T allele of rs713041 (odds ratio, 2.21; 95% CI, 0.98-4.99; P = .057), but not if they were carrying the C allele (P interaction .18) (Fig 1). The main findings were unchanged when we carried out 2 sensitivity analyses: first, excluding 3 mother-child pairs with outlying maternal blood selenium values (>300 μg/L); second, after controlling for 10 variables derived by principal-components analysis from the ALSPAC genomewide association study data to address possible residual confounding by population substructure.Table IAssociations between maternal blood selenium concentrations during pregnancy and childhood asthma and wheezing, stratified by maternal and child GPX4 rs713041 genotypeGPX4 rs713041 genotypeNAdjusted OR (95% CI) per doubling selenium concentrationP valueNAdjusted OR (95% CI) per doubling selenium concentrationP valueAsthmaStratified by maternal genotypeStratified by child genotype C:C5600.51 (0.17-1.54).235730.92 (0.31-2.74).88 T:C8520.95 (0.41-2.22).918771.18 (0.50-2.78).70 T:T3260.92 (0.29-2.92).882980.17 (0.04-0.72).02 P for interaction∗Testing difference in selenium associations according to genotype..64.068WheezingStratified by maternal genotypeStratified by child genotype C:C5670.74 (0.24-2.27).605770.69 (0.26-1.86).46 T:C8651.41 (0.57-3.45).468931.99 (0.81-4.93).13 T:T3291.14 (0.35-3.66).833020.16 (0.04-0.66).01 P for interaction∗Testing difference in selenium associations according to genotype..68.011OR, Odds ratio.∗ Testing difference in selenium associations according to genotype. Open table in a new tab OR, Odds ratio. In this population-based birth cohort study, we have found a novel, and plausible, interaction between maternal blood selenium concentration in pregnancy and child GPX4 genotype (rs713041) on the risk of asthma and wheezing at age 7 years. Our data indicate that low maternal blood selenium concentration increases the risk and higher blood selenium concentration reduces the risk but only in genetically susceptible children, namely, those who are homozygous for the minor T allele of GPX4. Villette et al4Villette S. Kyle J.A. Brown K.M. Pickard K. Milne J.S. Nicol F. et al.A novel single nucleotide polymorphism in the 3′ untranslated region of human glutathione peroxidase 4 influences lipoxygenase metabolism.Blood Cells Mol Dis. 2002; 29: 174-178Crossref PubMed Scopus (90) Google Scholar proposed that the rs713041 SNP in the 3′ untranslated region of GPX4 may influence how efficiently selenocysteine is incorporated into GPX4, leading to altered GPX4 synthesis in response to variations in selenium supply.4Villette S. Kyle J.A. Brown K.M. Pickard K. Milne J.S. Nicol F. et al.A novel single nucleotide polymorphism in the 3′ untranslated region of human glutathione peroxidase 4 influences lipoxygenase metabolism.Blood Cells Mol Dis. 2002; 29: 174-178Crossref PubMed Scopus (90) Google Scholar There is other evidence confirming that T/C variation (rs713041) has functional consequences,7Meplan C. Crosley L.K. Nicol F. Horgan G.W. Mathers J.C. Arthur J.R. et al.Functional effects of a common single-nucleotide polymorphism (GPX4c718t) in the glutathione peroxidase 4 gene: interaction with sex.Am J Clin Nutr. 2008; 87: 1019-1027Crossref PubMed Scopus (94) Google Scholar including a study showing that in individuals with the GPX4 (rs713041) TT genotype, oxidative stress decreased as in vivo selenium concentrations Furthermore, in vitro, selenium is necessary for the maximum expression of GPX4 in human lung epithelial cells.8Karunasinghe N. Han D. Zhu S. Yu J. Lange K. Duan H. et al.Serum selenium and single-nucleotide polymorphisms in genes for selenoproteins: relationship to markers of oxidative stress in men from Auckland, New Zealand.Genes Nutr. 2012; 7: 179-190Crossref PubMed Scopus (75) Google Scholar, 9Romanowska M. Kikawa K.D. Fields J.R. Maciag A. North S.L. Shiao Y.H. et al.Effects of selenium supplementation on expression of glutathione peroxidase isoforms in cultured human lung adenocarcinoma cell lines.Lung Cancer. 2007; 55: 35-42Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar We therefore propose that low maternal blood selenium concentration leads to suboptimal GPX4 activity and impaired antioxidant defenses against oxidative stress in fetal airway epithelium, leading to epithelial damage, which, in turn, contributes to the pathogenesis of asthma. Alternatively, prenatal selenium status might influence the development of asthma through the involvement of GPX4 in lipoxygenase metabolism.4Villette S. Kyle J.A. Brown K.M. Pickard K. Milne J.S. Nicol F. et al.A novel single nucleotide polymorphism in the 3′ untranslated region of human glutathione peroxidase 4 influences lipoxygenase metabolism.Blood Cells Mol Dis. 2002; 29: 174-178Crossref PubMed Scopus (90) Google Scholar However, because we cannot exclude the possibility that the main findings have arisen through type 1 error, replication of the interaction we observed is needed in another birth cohort of sufficient size. Our findings suggest that in a susceptible subgroup of mother-child pairs in the population, namely, pregnant women with suboptimal selenium status and offspring with the homozygous minor variant of GPX4 rs71304, there may be potential to reduce the incidence of childhood asthma through selenium supplementation in pregnancy. Whether primary prevention of asthma can be achieved in this way can be determined only through a clinical trial; the efficacy of such a trial is likely to be maximized by adopting a stratified approach. We are extremely grateful to all the families who took part in this study, to the midwives for their help in recruiting them, and to the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses. In multivariate analyses, we controlled for the following potential confounders: maternal factors during pregnancy (smoking, infections, anxiety score, and use of antibiotics, alcohol, and paracetamol); other maternal factors (educational level, housing tenure, financial difficulties, body mass index, age, parity, and history of asthma, eczema, rhinoconjunctivitis, and migraine); sex of child, season of birth, multiple pregnancy, gestational age, birth weight, head circumference, and birth length; and postnatal factors (breast-feeding, day care, pets, damp/mold, environmental tobacco smoke exposure, antibiotic and paracetamol use in infancy, number of younger siblings, and body mass index at age 7 years). We also controlled for the gestational timing of maternal blood samples because whole blood selenium concentrations are known to decline as pregnancy progresses.E1Butler J.A. Whanger P.D. Tripp M.J. Blood selenium and glutathione peroxidase activity in pregnant women: comparative assays in primates and other animals.Am J Clin Nutr. 1982; 36: 15-23Crossref PubMed Scopus (71) Google Scholar To test for interaction, we included the genotype and selenium variables, as well as a Genotype × Selenium interaction term, in the regression models.Table E1Associations between maternal blood selenium concentrations during pregnancy and childhood asthma and wheezingDiseaseSelenium concentration (μg/L)Unadjusted OR (95% CI)Adjusted OR (95% CI)Asthma (N = 2298)Q1 (≤96)1.01.0Q2 (96-105.74)0.77 (0.52-1.14)0.82 (0.54-1.26)Q3 (105.8-115.47)0.61 (0.40-0.92)0.76 (0.49-1.18)Q4 (115.5-128.7)0.73 (0.49-1.08)0.85 (0.55-1.31)Q5 (128.8-324.07)0.72 (0.48-1.07)0.83 (0.53-1.30)Per doubling0.66 (0.42-1.04)0.74 (0.45-1.21)P value for trend = .07P value for trend = .24Wheezing (N = 2326)Q1 (≤96)1.01.0Q2 (96-105.74)0.92 (0.60-1.40)0.97 (0.61-1.54)Q3 (105.8-115.47)0.77 (0.50-1.20)0.96 (0.59-1.54)Q4 (115.5-128.7)1.05 (0.70-1.59)1.16 (0.73-1.84)Q5 (128.8-324.07)0.95 (0.62-1.45)1.07 (0.66-1.72)Per doubling0.84 (0.52-1.33)0.87 (0.52-1.45)P value for trend = .45P value for trend = .59OR, Odds ratio. Open table in a new tab Table E2Association between maternal and child GPX4 rs713041 genotype and childhood asthma and wheezingDiseaseMaternal GPX4 rs713041 genotypeOR (95% CI)Asthma (N = 1738)N560C:C1.0852T:C0.90 (0.64-1.25)326T:T1.29 (0.87-1.93)Per allele1.11 (0.91-1.37)Wheezing (N = 1761)N567C:C1.0865T:C0.83 (0.59-1.19)329T:T1.28 (0.85-1.94)Per allele1.10 (0.89-1.37)DiseaseChild GPX4 rs713041 genotypeOR (95% CI)Asthma (N = 1748)N573C:C1.0877T:C1.23 (0.88-1.73)298T:T1.24 (0.80-1.94)Per allele1.13 (0.91-1.40)Wheezing (N = 1772)N577C:C1.0893T:C0.88 (0.63-1.24)302T:T1.10 (0.71-1.71)Per allele1.02 (0.82-1.28)OR, Odds ratio. Open table in a new tab OR, Odds ratio. OR, Odds ratio.