Talk:Abnormal Development - Folic Acid and Neural Tube Defects
Effects of maternal folic acid supplementation on airway remodeling and allergic airway disease development
J Matern Fetal Neonatal Med. 2019 Sep;32(18):2970-2978. doi: 10.1080/14767058.2018.1452904. Epub 2018 Mar 27.
İscan B1, Tuzun F1, Eroglu Filibeli B1, Cilekar Micili S2, Ergur BU2, Duman N1, Ozkan H1, Kumral A1.
Objective: Maternal folic acid supplementation has been recommended prior to and during the first trimester of pregnancy to reduce the risk of infant neural tube defects. However, an uncertain relationship between folic acid supplementation during pregnancy and development of childhood asthma exists. Recent data show a methyl donor-rich diet could increase the risk of developing allergic airway disease through DNA methylation and aberrant gene transcription. This study evaluated the effect of folic acid supplementation during pregnancy on airway remodeling and allergic airway disease vulnerability in a mouse asthma model. Methods: BALB/c mice were divided into four groups according to gestational folic acid supplementation and postnatal ovalbumin (OVA) exposure: Group 1 (whole pregnancy folic acid supplementation + OVA-exposed group), Group 2 (first gestational week folic acid supplementation + OVA-exposed group), Group 3 (no folic acid supplementation + OVA-exposed group), and Group 4 (control group). Offspring were sacrificed on day 45 for immunohistological and ultrastructural tests. Results: In OVA challenged groups, folic acid supplementation led to a thicker epithelial and subepithelial smooth muscle layer than in the unsupplemented group. Moreover, folic acid supplementation during whole pregnancy (Group 1) was associated with a thicker epithelial and subepithelial smooth muscle layer than folic acid supplementation during the first week of pregnancy (Group 2), suggesting a duration-response relationship. Electron microscopic imaging revealed that structural changes including the loss of epithelial integrity, thickening of basement membrane, and subepithelial fibrosis were more prominent in the folic acid supplementation groups. Conclusions: This study suggested that maternal folic acid supplementation during pregnancy affects airway remodeling and increases the allergic responses induced by ovalbumin challenge in offspring. In addition, the effect size increased as the duration and cumulative dose increased. KEYWORDS: Folic acid; airway remodeling; asthma; maternal folic acid supplementation PMID: 29587542 DOI: 10.1080/14767058.2018.1452904
Novel Mutation of LRP6 Identified in Chinese Han Population Links Canonical WNT Signaling to Neural Tube Defects
Birth Defects Res. 2018 Jan 15;110(1):63-71. doi: 10.1002/bdr2.1122. Epub 2017 Sep 29.
Shi Z1, Yang X1, Li BB1, Chen S1, Yang L1, Cheng L2, Zhang T3, Wang H1,4,5, Zheng Y1,4,6. Author information Abstract BACKGROUND: Neural tube defects (NTDs), the second most frequent cause of human congenital abnormalities, are debilitating birth defects due to failure of neural tube closure. It has been shown that noncanonical WNT/planar cell polarity (PCP) signaling is required for convergent extension (CE), the initiation step of neural tube closure (NTC). But the effect of canonical WNT//β-catenin signaling during NTC is still elusive. LRP6 (low density lipoprotein receptor related proteins 6) was identified as a co-receptor for WNT/β-catenin signaling, but recent studies showed that it also can mediate WNT/PCP signaling. METHODS: In this study, we screened mutations in the LRP6 gene in 343 NTDs and 215 ethnically matched normal controls of Chinese Han population. RESULTS: Three rare missense mutations (c.1514A>G, p.Y505C); c.2984A>G, p.D995G; and c.4280C>A, p.P1427Q) of the LRP6 gene were identified in Chinese NTD patients. The Y505C mutation is a loss-of-function mutation on both WNT/β-catenin and PCP signaling. The D995G mutation only partially lost inhibition on PCP signaling without affecting WNT/β-catenin signaling. The P1427Q mutation dramatically increased WNT/β-catenin signaling but only mildly loss of inhibition on PCP signaling. All three mutations failed to rescue CE defects caused by lrp6 morpholino oligos knockdown in zebrafish. Of interest, when overexpressed, D995G did not induce any defects, but Y505C and P1427Q caused more severe CE defects in zebrafish. CONCLUSION: Our results suggested that over-active canonical WNT signaling induced by gain-of-function mutation in LRP6 could also contribute to human NTDs, and a balanced WNT/β-catenin and PCP signaling is probably required for proper neural tube development. Birth Defects Research 110:63-71, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc. KEYWORDS: LRP6; PCP signaling; WNT/β-catenin signaling; mutation; neural tube defects PMID: 28960852 DOI: 10.1002/bdr2.1122
Hum Mutat. 2018 Jan 3. doi: 10.1002/humu.23397. [Epub ahead of print]
Li H1,2, Zhang J1, Chen S3, Wang F2, Zhang T2, Niswander L1.
Rare variants are considered underlying causes of complex diseases. The complex and severe group of disorders called neural tube defects (NTDs) results from failure of the neural tube to close during early embryogenesis. Neural tube closure requires the coordination of numerous signaling pathways, including the precise regulation of retinoic acid (RA) concentration which is controlled by enzymes involved in RA synthesis and degradation. Here we used a case-control mutation screen study to reveal rare variants in retinoid related genes in a Han Chinese NTD population by sequencing six genes in 355 NTD cases and 225 controls. NTD-specific rare variants were found in exonic regions and upstream regions. The RA-responsive genes CYP26A1, CRABP1 and ALDH1A2 harbored NTD-specific rare variants in their upstream regions. Unexpectedly, the majority of missense variants in NTD cases were found in CYP26B1 which encodes a RA degradation enzyme, whereas no missense variants in this gene were found in controls. Functional analysis indicated that the CYP26B1 NTD variants were inefficient in the degradation of RA using assays of RA-induced transcription and RA-initiated neuronal differentiation. Our study supports the contribution of rare variants in RA related genes to the etiology of human NTDs. This article is protected by copyright. All rights reserved.
PMID: 29297599 DOI: 10.1002/humu.23397
Decrease in neural tube defects since folic acid added to bread
Mandatory fortification of bread with folic acid (in Australia) and iodine (in Australia and New Zealand) was introduced in 2009 to address two important public health issues: to reduce the prevalence of neural tube defects (serious birth defects such as spina bifida) in Australia and to deal with the re-emergence of iodine deficiency in both Australia and New Zealand.
The introduction of the mandatory fortification has resulted in improved health outcomes, particularly for teenagers and Aboriginal and Torres Strait Islander women, according to a new report from the Australian Institute of Health and Welfare (AIHW).
The report, Monitoring the health impacts of mandatory folic acid and iodine fortification, shows that the increase in folic acid and iodine in the food supply since the introduction of mandatory fortification has resulted in notable health improvements.
'There was a significant (14.4%) overall decrease in the rate of neural tube defects (NTDs) in Australia following mandatory folic acid fortification. However among teenagers, the rate of NTDs decreased even more, by almost 55%, and for Aboriginal and Torres Strait Islander women, the rate of NTDs decreased by 74%, which is a very positive outcome,' said AIHW spokesperson Ms Ann Hunt.
Identification of PCSK9 as a novel serum biomarker for the prenatal diagnosis of neural tube defects using iTRAQ quantitative proteomics
Sci Rep. 2015 Dec 22;5:17559. doi: 10.1038/srep17559.
An D1,2, Wei X1, Li H1, Gu H1, Huang T1, Zhao G1, Liu B1, Wang W3, Chen L1, Ma W1, Zhang H1, Cao S1, Yuan Z1.
To identify candidate serum molecule biomarkers for the non-invasive early prenatal diagnosis of neural tube defects (NTDs), we employed an iTRAQ-based quantitative proteomic approach to analyze the proteomic changes in serum samples from embryonic day (E) 11 and E13 pregnant rats with spina bifida aperta (SBA) induced by all-trans retinoic acid. Among the 390 proteins identified, 40 proteins at E11 and 26 proteins at E13 displayed significant differential expression in the SBA groups. We confirmed 5 candidate proteins by ELISA. We observed the space-time expression changes of proprotein convertase subtilisin/kexin type 9 (PCSK9) at different stages of fetal development, including a marked decrease in the sera of NTD pregnancies and gradual increase in the sera of normal pregnancies with embryonic development. PCSK9 demonstrated the diagnostic efficacy of potential NTD biomarkers [with an area under the receiver operating characteristic curve of 0.763, 95% CI: 065-0.88]. Additionally, PCSK9 expression in the spinal cords and placentas of SBA rat fetuses was markedly decreased. PCSK9 could serve as a novel molecular biomarker for the non-invasive prenatal screening of NTDs and may be involved in the pathogenesis of NTDs at critical periods of fetal development.
Prenatal versus postnatal repair procedures for spina bifida for improving infant and maternal outcomes
Cochrane Database Syst Rev. 2014 Oct 28;(10):CD008825. doi: 10.1002/14651858.CD008825.pub2.
Grivell RM1, Andersen C, Dodd JM.
BACKGROUND: Spina bifida is a fetal neural tube defect (NTD), which may be diagnosed in utero and is compatible with life postnatally, albeit often with significant disability and morbidity. Although postnatal repair is possible, with increasing in utero diagnosis with ultrasound, the condition has been treated during pregnancy (prenatal repair) with the aim of decreased morbidity for the child. The procedure that is performed during pregnancy does have potential morbidities for the mother, as it involves maternal surgery to access the fetus. OBJECTIVES: To compare the effects of prenatal versus postnatal repair and different types of repair of spina bifida on perinatal mortality and morbidity, longer term infant outcomes and maternal morbidity. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 July 2014). SELECTION CRITERIA: All published, unpublished, and ongoing randomised controlled trials comparing prenatal and postnatal repair of meningomyelocele for fetuses with spina bifida and different types of prenatal repair. DATA COLLECTION AND ANALYSIS: Two review authors independently evaluated trials for inclusion and methodological quality without consideration of their results according to the stated eligibility criteria and extracted data. MAIN RESULTS: Our search strategy identified six reports for potential inclusion. Of those, we included one trial (four reports) involving 158 women, which was at low risk of bias.The one included trial examined the effect of prenatal repair versus postnatal repair. For the primary infant outcome of neonatal mortality, there was no clear evidence of a difference identified for prenatal versus postnatal repair (one study, 158 infants, risk ratio (RR) 0.51, 95% confidence interval (CI) 0.05 to 5.54), however event rates were uncommon and so the analysis is likely to be underpowered to detect differences.Prenatal repair was associated with an earlier gestational age at birth (one study, 158 infants, mean difference (MD) -3.20 weeks, 95% CI -3.93 to -2.47) and a corresponding increase in both the risk of preterm birth before 37 weeks (one study, 158 infants, RR 5.30, 95% CI 3.11 to 9.04) and preterm birth before 34 weeks (one study, 158 infants, RR 9.23, 95% CI 3.45 to 24.71). Prenatal repair was associated with a reduction in shunt dependent hydrocephalus and moderate to severe hindbrain herniation. For women, prenatal repair was associated with increased preterm ruptured membranes (one study, 158 women, RR 6.15, 95% CI 2.75 to 13.78), although there was no clear evidence of difference in the risk of chorioamnionitis or blood transfusion, although again, event rates were uncommon.A number of this review's secondary infant and maternal outcomes were not reported. For the infant: days of hospital admission; survival to discharge; stillbirth; need for further surgery (e.g. skin grafting); neurogenic bladder dysfunction; childhood/infant quality of life. For the mother: admission to intensive care; women's emotional wellbeing and satisfaction with care. AUTHORS' CONCLUSIONS: This review is based one small well-conducted study. There is insufficient evidence to recommend drawing firm conclusions on the benefits or harms of prenatal repair as an intervention for fetuses with spina bifida. Current evidence is limited by the small number of pregnancies that have been included in the single conducted randomised trial to date. PMID 25348498
Fetal surgery for spina bifida: past, present, future
Semin Pediatr Surg. 2013 Feb;22(1):10-7. doi: 10.1053/j.sempedsurg.2012.10.003.
Open spina bifida or myelomeningocele (MMC) is a common birth defect that is associated with significant lifelong morbidity. Little progress has been made in the postnatal surgical management of the child with spina bifida. Postnatal surgery is aimed at covering the exposed spinal cord, preventing infection, and treating hydrocephalus with a ventricular shunt. Experimental and clinical evidence suggest that the primary cause of the neurologic defects associated with MMC is not simply incomplete neurulation, but rather chronic, mechanical and amniotic-fluid induced chemical trauma that progressively damages the exposed neural tissue during gestation. The cerebrospinal fluid leak through the MMC leads to hindbrain herniation and hydrocephalus. In utero repair of open spina bifida is now performed in selected patients and presents an additional therapeutic alternative for expectant mothers carrying a fetus with MMC. In the past, studies in animal models and clinical case series laid the groundwork for a clinical trial to test the safety and efficacy of fetal MMC repair. In the present, a prospective, randomized study (the MOMS trial) has shown that fetal surgery for MMC before 26 weeks' gestation may preserve neurologic function, reverse the hindbrain herniation of the Chiari II malformation, and obviate the need for postnatal placement of a ventriculoperitoneal shunt. However, this study also demonstrates that fetal surgery is associated with significant risks related to the uterine scar and premature birth. In the future, research will expand our understanding of the pathophysiology of MMC, evaluate the long-term impact of in-utero intervention, and to refine timing and technique of fetal MMC surgery using tissue engineering technology. Copyright © 2013 Elsevier Inc. All rights reserved.
Preconception folic acid supplementation and risk for chromosome 21 nondisjunction: a report from the National Down Syndrome Project
Am J Med Genet A. 2013 Mar;161A(3):438-44. doi: 10.1002/ajmg.a.35796. Epub 2013 Feb 7.
Hollis ND1, Allen EG, Oliver TR, Tinker SW, Druschel C, Hobbs CA, O'Leary LA, Romitti PA, Royle MH, Torfs CP, Freeman SB, Sherman SL, Bean LJ. Author information
Both a lack of maternal folic acid supplementation and the presence of genetic variants that reduce enzyme activity in folate pathway genes have been linked to meiotic nondisjunction of chromosome 21; however, the findings in this area of research have been inconsistent. To better understand these inconsistencies, we asked whether maternal use of a folic acid-containing supplement before conception reduces risk for chromosome 21 nondisjunction. Using questionnaire data from the National Down Syndrome Project, a population-based case-control study, we compared the use of folic acid-containing supplements among mothers of infants with full trisomy 21 due to maternal nondisjunction (n = 702) and mothers of infants born with no major birth defects (n = 983). Using logistic regression, adjusting for maternal age, race/ethnicity, and infant age at maternal interview, we found no evidence of an association between lack of folic acid supplementation and maternal nondisjunction among all case mothers (OR = 1.16; 95% CI: 0.90-1.48). In analyses stratified by meiotic stage and maternal age (<35 or ≥35 years), we found an association among older mothers experiencing meiosis II nondisjunction errors (OR = 2.00; 95% CI: 1.08-3.71). These data suggest that lack of folic acid supplementation may be associated specifically with MII errors in the aging oocyte. If confirmed, these results could account for inconsistencies among previous studies, as each study sample may vary by maternal age structure and proportion of meiotic errors. Copyright © 2013 Wiley Periodicals, Inc.
Association between maternal use of folic acid supplements and risk of autism spectrum disorders in children
JAMA. 2013 Feb 13;309(6):570-7. doi: 10.1001/jama.2012.155925.
Surén P, Roth C, Bresnahan M, Haugen M, Hornig M, Hirtz D, Lie KK, Lipkin WI, Magnus P, Reichborn-Kjennerud T, Schjølberg S, Davey Smith G, Øyen AS, Susser E, Stoltenberg C.
Source Norwegian Institute of Public Health, PO Box 4404, Nydalen, N-0403 Oslo, Norway. email@example.com
IMPORTANCE: Prenatal folic acid supplements reduce the risk of neural tube defects in children, but it has not been determined whether they protect against other neurodevelopmental disorders. OBJECTIVE: To examine the association between maternal use of prenatal folic acid supplements and subsequent risk of autism spectrum disorders (ASDs) (autistic disorder, Asperger syndrome, pervasive developmental disorder-not otherwise specified [PDD-NOS]) in children. DESIGN, SETTING, AND PATIENTS: The study sample of 85,176 children was derived from the population-based, prospective Norwegian Mother and Child Cohort Study (MoBa). The children were born in 2002-2008; by the end of follow-up on March 31, 2012, the age range was 3.3 through 10.2 years (mean, 6.4 years). The exposure of primary interest was use of folic acid from 4 weeks before to 8 weeks after the start of pregnancy, defined as the first day of the last menstrual period before conception. Relative risks of ASDs were estimated by odds ratios (ORs) with 95% CIs in a logistic regression analysis. Analyses were adjusted for maternal education level, year of birth, and parity. MAIN OUTCOME MEASURE: Specialist-confirmed diagnosis of ASDs. RESULTS: At the end of follow-up, 270 children in the study sample had been diagnosed with ASDs: 114 with autistic disorder, 56 with Asperger syndrome, and 100 with PDD-NOS. In children whose mothers took folic acid, 0.10% (64/61,042) had autistic disorder, compared with 0.21% (50/24,134) in those unexposed to folic acid. The adjusted OR for autistic disorder in children of folic acid users was 0.61 (95% CI, 0.41-0.90). No association was found with Asperger syndrome or PDD-NOS, but power was limited. Similar analyses for prenatal fish oil supplements showed no such association with autistic disorder, even though fish oil use was associated with the same maternal characteristics as folic acid use. CONCLUSIONS AND RELEVANCE: Use of prenatal folic acid supplements around the time of conception was associated with a lower risk of autistic disorder in the MoBa cohort. Although these findings cannot establish causality, they do support prenatal folic acid supplementation. Comment in The following popper user interface control may not be accessible. Tab to the next button to revert the control to an accessible version.Destroy user interface controlPericonceptional folic acid and risk of autism spectrum disorders. [JAMA. 2013]
Upper and lower urinary tract outcomes in adult myelomeningocele patients: a systematic review
PLoS One. 2012;7(10):e48399. doi: 10.1371/journal.pone.0048399. Epub 2012 Oct 31.
Veenboer PW, Bosch JL, van Asbeck FW, de Kort LM. Source Department of Urology, University Medical Centre Utrecht, Utrecht, The Netherlands.
BACKGROUND: The introduction of sophisticated treatment of bladder dysfunction and hydrocephalus allows the majority of SB patients to survive into adulthood. However, no systematic review on urological outcome in adult SB patients is available and no follow-up schemes exist. OBJECTIVES: To systematically summarize the evidence on outcome of urinary tract functioning in adult SB patients. METHODS: A literature search in PubMed and Embase databases was done. Only papers published in the last 25 years describing patients with open SB with a mean age >18 years were included. We focused on finding differences in the treatment strategies, e.g., clean intermittent catheterization and antimuscarinic drugs versus early urinary diversion, with regard to long-term renal and bladder outcomes. RESULTS: A total of 13 articles and 5 meeting abstracts on urinary tract status of adult SB patients were found describing a total of 1564 patients with a mean age of 26.1 years (range 3-74 years, with a few patients <18 years). All were retrospective cohort studies with relatively small and heterogeneous samples with inconsistent reporting of outcome; this precluded the pooling of data and meta-analysis. Total continence was achieved in 449/1192 (37.7%; range 8-85%) patients. Neurological level of the lesion and hydrocephalus were associated with incontinence. Renal function was studied in 1128 adult patients. In 290/1128 (25.7%; range 3-81.8%) patients some degree of renal damage was found and end-stage renal disease was seen in 12/958 (1.3%) patients. Detrusor-sphincter dyssynergy and detrusor-overactivity acted as adverse prognostic factors for the development of renal damage. CONCLUSIONS: These findings should outline follow-up schedules for SB patients, which do not yet exist. Since renal and bladder deterioration continues beyond adolescence, follow-up of these individuals is needed. We recommend standardization in reporting the outcome of urinary tract function in adult SB patients.
Disruption of the folate pathway in zebrafish causes developmental defects
BMC Dev Biol. 2012 Apr 5;12(1):12. [Epub ahead of print]
Lee MS, Bonner JR, Bernard DJ, Sanchez EL, Sause ET, Prentice RR, Burgess SM, Brody LC.
ABSTRACT: BACKGROUND: Folic acid supplementation reduces the risk of neural tube defects and congenital heart defects. The biological mechanisms through which folate prevents birth defects are not well understood. We explore the use of zebrafish as a model system to investigate the role of folate metabolism during development. RESULTS: We first identified zebrafish orthologs of 12 human folate metabolic genes. RT-PCR and in situ analysis indicated maternal transcripts supply the embryo with mRNA so that the embryo has an intact folate pathway. To perturb folate metabolism we exposed zebrafish embryos to methotrexate (MTX), a potent inhibitor of dihydrofolate reductase (Dhfr) an essential enzyme in the folate metabolic pathway. Embryos exposed to high doses of MTX exhibited developmental arrest prior to early segmentation. Lower doses of MTX resulted in embryos with a shortened anterior-posterior axis and cardiac defects: linear heart tubes or incomplete cardiac looping. Inhibition of dhfr mRNA with antisense morpholino oligonucleotides resulted in embryonic lethality. One function of the folate pathway is to provide essential one-carbon units for dTMP synthesis, a rate-limiting step of DNA synthesis. After 24 hours of exposure to high levels of MTX, mutant embryos continue to incorporate the thymidine analog BrdU. However, additional experiments indicate that these embryos have fewer mitotic cells, as assayed with phospho-histone H3 antibodies, and that treated embryos have perturbed cell cycles. CONCLUSIONS: Our studies demonstrate that human and zebrafish utilize similar one-carbon pathways. Our data indicate that folate metabolism is essential for early zebrafish development. Zebrafish studies of the folate pathway and its deficiencies could provide insight into the underlying etiology of human birth defects and the natural role of folate in development.
Periconceptional bread intakes indicate New Zealand's proposed mandatory folic acid fortification program may be outdated: results from a postpartum survey
BMC Pregnancy Childbirth. 2012 Feb 14;12:8.
Mallard SR, Gray AR, Houghton LA. Source Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
BACKGROUND: In September 2009, a folic acid fortification mandate (135 μg/100 g bread) was to be implemented in New Zealand. However, due to political and manufacturer objection, fortification was deferred until May 2012. Based on estimates of bread consumption derived from a 1997 nationally representative survey, this program was intended to deliver a mean additional intake of 140 μg folic acid/d to women of childbearing age. Little is known about current bread consumption patterns in this target group. The aim of this study was to assess bread consumption among women prior to and during pregnancy with the intent to estimate periconceptional folic acid intakes that would be derived from bread if mandatory fortification were implemented as currently proposed. METHODS: A retrospective survey of 723 postpartum women in hospitals and birthing centres across New Zealand was conducted using a self-administered questionnaire on bread intake prior to and during pregnancy and maternal socio-demographic and obstetric characteristics. RESULTS: Median bread intake before conception (2 slices/d) was below that of previous data upon which the current fortification proposal was modeled (3-4 slices/d). If mandatory fortification is implemented as proposed, only 31% (95% CI = 24%-37%) of childbearing-age women would attain an additional folic acid intake of ≥ 140 μg/d, with a mean of 119 μg/d (95% CI = 107 μg/d-130 μg/d). Based on these data, a fortification level of 160 μg/100 g bread is required to achieve the targeted mean of 140 μg folic acid/d. Nonetheless, under the current proposal additional folic acid intakes would be greatest among the least advantaged segments of the target population: Pacific and indigenous Māori ethnic groups; those with increased parity, lower income and education; younger and single mothers; and women with unplanned pregnancies. Subgroups predicted to derive less than adequate folic acid intakes from the proposed policy were women of Asian descent and those with a postgraduate education. CONCLUSIONS: This study provides insight on the ability of a fortification policy to benefit the groups at highest risk of poor folate intakes in a population. However, bread consumption among the target group of childbearing women appears to have declined since the data used in previous dietary modeling were collected. Thus, it seems prudent to re-model dietary folic acid intakes based on more recent national survey data prior to the implementation of a mandatory folic acid fortification policy.
Mutations in genes encoding the glycine cleavage system predispose to neural tube defects in mice and humans
Hum Mol Genet. 2012 Apr 1;21(7):1496-503. Epub 2011 Dec 13.
Narisawa A, Komatsuzaki S, Kikuchi A, Niihori T, Aoki Y, Fujiwara K, Tanemura M, Hata A, Suzuki Y, Relton CL, Grinham J, Leung KY, Partridge D, Robinson A, Stone V, Gustavsson P, Stanier P, Copp AJ, Greene ND, Tominaga T, Matsubara Y, Kure S.
Neural tube defects (NTDs), including spina bifida and anencephaly, are common birth defects of the central nervous system. The complex multigenic causation of human NTDs, together with the large number of possible candidate genes, has hampered efforts to delineate their molecular basis. Function of folate one-carbon metabolism (FOCM) has been implicated as a key determinant of susceptibility to NTDs. The glycine cleavage system (GCS) is a multi-enzyme component of mitochondrial folate metabolism, and GCS-encoding genes therefore represent candidates for involvement in NTDs. To investigate this possibility, we sequenced the coding regions of the GCS genes: AMT, GCSH and GLDC in NTD patients and controls. Two unique non-synonymous changes were identified in the AMT gene that were absent from controls. We also identified a splice acceptor site mutation and five different non-synonymous variants in GLDC, which were found to significantly impair enzymatic activity and represent putative causative mutations. In order to functionally test the requirement for GCS activity in neural tube closure, we generated mice that lack GCS activity, through mutation of AMT. Homozygous Amt(-/-) mice developed NTDs at high frequency. Although these NTDs were not preventable by supplemental folic acid, there was a partial rescue by methionine. Overall, our findings suggest that loss-of-function mutations in GCS genes predispose to NTDs in mice and humans. These data highlight the importance of adequate function of mitochondrial folate metabolism in neural tube closure.
Determination of folic acid in milk, milk powder and energy drink by an indirect immunoassay
J Sci Food Agric. 2012 Mar 1. doi: 10.1002/jsfa.5625. [Epub ahead of print]
Zhang T, Xue H, Zhang B, Zhang Y, Song P, Tian X, Xing Y, Wang P, Meng M, Xi R. Source College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Tianjin, China.
BACKGROUND: Folic acid (FA) is essential for healthy people (reference daily intake 400 µg day(-1) ) and pregnant women (600 µg day(-1) ). Insufficient intake of FA will increase the risk of neural tube defects in newborns. In this study an indirect enzyme-linked immunosorbent assay was developed for rapid and convenient detection of FA in vitamin-fortified foods. RESULTS: A carbodiimide-modified active ester method was used to synthesise the immunogen (FA-bovine serum albumin (BSA) conjugate) to raise polyclonal antibodies for FA. The coupling ratio of FA with BSA was determined to be 14:1 (molar ratio). The detection limit of the immunoassay was 3.0 ng mL(-1) in buffer, 3.52 ng mL(-1) in energy drink, 11.91 ng mL(-1) in milk and 16.50 ng mL(-1) in milk powder. Intra- and inter-assay variability ranged from 6.6 to 15.1%. Analytical recoveries of FA-spiked samples were 88.3-108.9%. CONCLUSION: The immunoassay developed in this study can be used as a simple, rapid and accurate method for fast semi-quantitative and quantitative on-site analysis of FA in food products. Copyright © 2012 Society of Chemical Industry. Copyright © 2012 Society of Chemical Industry. PMID 22378547
Folic Acid Supplementation for Women of Childbearing Age versus Supplementation for the General Population: A Review of the Known Advantages and Risks
Int J Family Med. 2011;2011:173705. Epub 2011 May 23.
Shelke N, Keith L. Source College of Arts and Sciences, Loyola University, Chicago, IL 60660, USA.
This paper focuses on the current best-evidence-based clinical practices and controversies surrounding folic acid supplementation/fortification for the prevention of neural tube defects (NTDs) during early pregnancy. The paper also discusses the controversies surrounding the effect of folic acid on the prevention as well as the promotion of cancer. Sufficient data is available to safely conclude that folic acid reduces the risk of NTDs during pregnancy; however, a safe dosage has not yet been calculated for the rest of the population. More research is necessary to study the complete role of folic acid in human growth and development.
High intake of folic acid disrupts embryonic development in mice
Birth Defects Res A Clin Mol Teratol. 2011 Jan;91(1):8-19. doi: 10.1002/bdra.20754. Epub 2010 Dec 22.
Pickell L, Brown K, Li D, Wang XL, Deng L, Wu Q, Selhub J, Luo L, Jerome-Majewska L, Rozen R.
Department of Human Genetics, McGill University and Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.
BACKGROUND: Folic acid fortification and supplementation has increased folate intake and blood folate concentrations and successfully reduced the incidence of neural tube defects. However, the developmental consequences of high folate intake are unknown. This study investigated the impact of high folate intake, alone or with methylenetetrahydrofolate reductase (MTHFR) deficiency, on embryonic and placental development in mice.
METHODS: Mthfr +/+ or +/- pregnant mice on a control diet (CD; recommended intake of folic acid for rodents) or folic acid-supplemented diet (FASD; 20-fold higher than the recommended intake) were examined for embryonic loss, delay, and defects at 10.5 and 14.5 days post coitum (dpc); 10.5-dpc placenta, and 14.5-dpc embryo hearts were studied histologically.
RESULTS: Total plasma folate was 10-fold higher in FASD compared to CD mice; plasma homocysteine levels were not affected by diet. At 10.5 dpc, the FASD was associated with embryonic delay and growth retardation, and may confer susceptibility to embryonic defects. The FASD did not adversely affect 10.5-dpc placental development. At 14.5 dpc, embryos from the FASD Mthfr +/+ group were delayed and the FASD was associated with thinner ventricular walls in embryonic hearts. There was a significant interaction between maternal MTHFR deficiency and a high folate diet for several developmental outcomes.
CONCLUSIONS: Our study suggests that high folate intake may have adverse effects on fetal mouse development and that maternal MTHFR deficiency may improve or rescue some of the adverse outcomes. These findings underscore the need for additional studies on the potential negative impact of high folate intake during pregnancy.
Copyright © 2010 Wiley-Liss, Inc. PMID: 21254354
Eichholzer M, Tonz O, Zimmermann R. Folic acid: a public-health challenge. Lancet. 2006 Apr 22;367(9519):1352-61. "... In the USA, Canada, and Chile, mandatory fortification of flour substantially improved folate and homocysteine status, and neural tube defects rates fell by between 31% and 78%. Nevertheless, many countries do not choose mandatory folic acid fortification, in part because expected additional health benefits are not yet scientifically proven in clinical trials, in part because of feared health risks, and because of the issue of freedom of choice. Thus, additional creative public-health approaches need to be developed to prevent neural tube defects and improve the folate status of the general population."
Padmanabhan R. Etiology, pathogenesis and prevention of neural tube defects. Congenit Anom (Kyoto). 2006 Jun;46(2):55-67.
Tamura T, Picciano MF. Folate and human reproduction. Am J Clin Nutr. 2006 May;83(5):993-1016.
Wen SW, Walker M. An exploration of health effects of folic acid in pregnancy beyond reducing neural tube defects. J Obstet Gynaecol Can. 2005 Jan;27(1):13-9.
- Australian Institute of Health and Welfare Mandatory folic acid and iodine fortification in Australia and New Zealand: baseline report for monitoring "This report presents key baseline data for monitoring mandatory folic acid and iodine fortification in Australia and New Zealand. Data are presented for each component of the fortification monitoring frameworks as follows: food composition; folic acid and iodine intake; folic acid and iodine status of the populations; and health outcomes." Reports
- Prevalence of neural tube defects in Australia prior to mandatory fortification of bread-making flour with folic acid.
"The birth prevalence of NTDs from 1998-2005, was 5/10,000 births. The total prevalence including terminations of pregnancy was 13/10,000 births. A 26% declining trend in total prevalence was seen from 1992-2005, but the main decline occurred prior to 1998. Women who were Indigenous, socially disadvantaged, young, living in remote areas and had multiple gestations were more likely to give birth to babies with NTDs."
- Low folic acid supplement intake rate among women in northern China with a high-prevalence of neural tube defects, 2008.
"In 2008, we conducted a cross-sectional survey to investigate awareness and intake rates of folic acid supplementation among women of childbearing age from 293 counties (all national-level poverty counties) in northern China that had a high prevalence of NTDs ( about 16.0/10,000 births of at least 28 weeks gestation in 2008)."
- Association of folate receptor (folr1, folr2, folr3) and reduced folate carrier (slc19a1) genes with meningomyelocele.
"This study involved the analyses of selected single nucleotide polymorphisms across the folate receptor genes and the folate carrier gene in a large population sample. It provided evidence that the rare alleles of specific single nucleotide polymorphisms within these genes appear to be statistically significant for association to meningomyelocele in the patient population that was tested."
- High intake of folic acid disrupts embryonic development in mice.
"Mthfr +/+ or +/- pregnant mice on a control diet (CD; recommended intake of folic acid for rodents) or folic acid-supplemented diet (FASD; 20-fold higher than the recommended intake) were examined for embryonic loss, delay, and defects at 10.5 and 14.5 days post coitum (dpc); 10.5-dpc placenta, and 14.5-dpc embryo hearts were studied histologically. ...Our study suggests that high folate intake may have adverse effects on fetal mouse development and that maternal MTHFR deficiency may improve or rescue some of the adverse outcomes. These findings underscore the need for additional studies on the potential negative impact of high folate intake during pregnancy.
Folate levels and neural tube defects. Implications for prevention
JAMA. 1995 Dec 6;274(21):1698-702.
Daly LE, Kirke PN, Molloy A, Weir DG, Scott JM. Source Department of Public Health Medicine and Epidemiology, University College Dublin, Ireland.
Using data from a recent case-control study, a woman's risk of having a child with a neural tube defect (NTD) was found to be associated with early pregnancy red cell folate levels in a continuous dose-response relationship. These findings were used to calculate the reduction in NTD cases that would be expected under two different strategies to raise folate levels. Targeting high-risk individuals has a small effect on the population prevalence but can substantially change an individual's risk. Targeting the population produces a small change in individual risk but has a large effect on the population prevalence. Supplementation of high-risk women would be the most efficient method to implement the high-risk strategy, while food fortification would be preferable for the population approach. The current guidelines for the prevention of NTD are for an increased folic acid intake of 0.4 mg per day. This would result in a 48% reduction in NTDs, which may be near optimal. The two intervention strategies should be considered complementary in prevention of NTDs.
Comment in JAMA. 1995 Dec 6;274(21):1717-8. JAMA. 1996 Jun 5;275(21):1635-6.