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PubMed2005

Interaction between maternal periconceptional supplementation of folic acid and reduced folate carrier gene polymorphism of neural tube defects.

OBJECTIVE: To search the interaction between reduced folate carrier gene (RFC1 A80G) polymorphism of children with neural tube defects (NTDs) and maternal periconceptional no supplementation of folic acid. The purpose is to provide the epidemiological evidence for finding genetic marker of NTDs. METHODS: RFC1 (A80G) genotype was detected using PCR-restricted fragment length polymorphism for the blood DNA of 104 trios with NTDs-affected child, and 100 control families with non-malformed control children. The authors investigated the gene-environment interactions between the offspring RFC1 genotype and maternal periconceptional folic acid supplementation through a case-control study. RESULTS: It was observed that the offspring with the GG genotype were associated with a 2.56-fold increased risk of NTDs when compared to those with the AA genotype (OR = 2.56; 95% CI = 1.04-6.36) in this population under investigation. The risk of mothers who did not take folic acid for having an NTDs-affected infants was 7.69 (95% CI = 2.86-21.75). Among the mothers who did not utilize folic acid supplements, the NTDs risk was 3.30 (95% CI = 1.15-9.65) for offspring with the GG genotype, compared to the reference (AA) genotype. Children who had the GG genotype and whose mothers did not take folic acid had an elevated risk for NTDs (OR = 8.80, 95% CI = 2.86 - 29.82), compared to "offspring with AA or GA genotype" and "maternal folic acid use", the interactive coefficient being 1.45. CONCLUSION: The above findings indicate that the RFC1 genotype (GG) is a possible susceptible gene marker for an increased NTDs risk in Chinese population, and there is a potential gene-nutrient interaction between offspring RFC1 GG genotype and maternal periconceptional intake of folic acid on the risk of NTDs. However,the sample size of this study was limited, a larger sample of population-based study is required to pursue the initial observation.

Adult↗

PubMed1997

Minimum effective dose of folic acid for food fortification to prevent neural-tube defects.

BACKGROUND: Although a daily supplement of 400 micrograms folic acid has been shown to prevent neural-tube defects (NTD), most women do not take the recommended supplement. Thus, food fortification is to be introduced in the USA and is being considered in the UK. Because of safety concerns, the USA has chosen a level of fortification that will increase the average woman's intake by only 100 micrograms. Such an increase, although safe, may be ineffective; but a trial to assess its efficacy would be unethical. Because women with red-cell folate concentrations above 400 micrograms/L have a very low risk of NTD, we undertook a randomised trial of several folic acid doses to find out how much is needed to reach this protective concentration. METHODS: We screened 323 women. 172 with red-cell folate between 150 micrograms/L and 400 micrograms/L were invited to take part in the trial. 121 women were randomly assigned placebo or 100 micrograms, 200 micrograms, or 400 micrograms daily of additional folic acid. Compliance was monitored by having the women sign a dated sheet when taking the tablet. 95 women completed the 6-month study. FINDINGS: There were significant increases in red-cell folate in all folic acid groups. The placebo group showed no significant change. The median incremental changes and median post-treatment concentrations were 67 micrograms/L (95% CI 43-120) and 375 micrograms/L (354-444) in the 100 micrograms/day group, 130 micrograms/L (108-184) and 475 micrograms/L (432-503) in the 200 micrograms/day group, and 200 micrograms/L (125-312) and 571 micrograms/L (481-654) in the 400 micrograms/day group. INTERPRETATION: A fortification programme that delivered 400 micrograms folic acid daily to women would protect against NTD, but at the expense of unnecessarily high exposure for many people. Delivery of 200 micrograms daily is also effective against NTD and safer for the general population. Based on projections from the positive folate balance in the group that received 100 micrograms daily, this dose taken continually, as it will be in fortified food, will also produce an important decrease in NTD.

Adult↗

PubMed1995

Morphological study of surgically induced open neural tube defect in old (14 and 21 days) chick embryos.

As an experimental model for the research of open neural tube defect (NTD), the surgical model has several advantages over others, in spite of the fact that the pathogenetic mechanism is not compatible with the human intrauterine events. To make reproducible NTDs by surgery and to compare the surgically induced lesions with the human myeloschisis morphologically, we opened the neural tube for a length of 9-11 somites in Hamburger and Hamilton stage 16-19 chick embryos. Embryos which survived until the late in ovo life (total age 14 and 21 days) showed relatively reproducible open NTDs. Morphologically they are similar to human myeloschisis. This study suggests that the surgical model can be suitable for studies of open NTDs.

Age Factors↗

PubMed2004

The use of drugs in mothers of offspring with neural-tube defects.

OBJECTIVE: To study the risk of maternal drugs use during pregnancy in the origin of isolated neural-tube defects (NTD). MATERIALS AND METHODS: 1202 cases with NTD, 38,151 population controls without any defects and 22,475 patient controls with other defects were compared in the population-based data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities (HCCSCA), 1980-1996. The HCCSCA contains 542 drugs, however only those drugs were evaluated which included five or more mothers in the NTD group. Drugs with the same chemical structures were combined. In addition, only drug use in the second month of pregnancy was evaluated because it is the critical period for NTD. Of course, it is necessary to exclude different biases, mainly recall bias at the evaluation of these drugs. Of 121 chemicals, only oxytetracycline, carbamazepine and valproic acid had some association with NTD. High doses of exogenous oestrogens, clomiphene, chorionic gonadotropin, lynesterol and ergotamine also seemed to have some indirect association with NTD because their exposures occurred more frequently before the critical period of NTD due to maternal infertility. CONCLUSION: Our findings suggest that drugs used during pregnancy do not appear to substantially contribute to the occurrence of isolated NTD but some drugs have a role in the origin of these defects.

Abnormalities, Drug-Induced↗

PubMed1980

Polyacrylamide gel electrophoresis of amniotic fluid cholinesterases: a good prenatal test for neural tube defects.

The qualitative assay of the cholinesterases (ChE) in amniotic fluid on polyacrylamide gel gave a single major band (cholinesterase) in all samples from normal pregnancies, and two major bands (cholinesterase and acetylcholinesterase) in all cases from fetuses with open neural tube defects. Five fluids which were true false positive on alpha-fetoprotein (AFP) assay (elevated AFP in a clear fluid but normal fetus) had a single band, and two fluids which were false negative on AFP testing (normal AFP but spina bifida fetus) had two bands. The second 'diagnostic' ChE band sometimes occurred, together with other extra bands, in some fluids which were very severely contaminated by maternal or fetal blood, but in four of six fluids from normal fetuses where fetal blood staining was sufficient to cause the AFP to be elevated, there was only one ChE band. It is suggested that the qualitative assay of ChE should be performed in addition to AFP in the prenatal diagnosis of neural tube defects.

Amniotic Fluid↗

PubMed1989

Serum from pregnant women carrying a fetus with neural tube defect is teratogenic for rat embryos in culture.

Sera from 13 pregnant women carrying a fetus with a neural tube defect, and from 13 control women with normal pregnancies at the same stage of gestation were used in the culture of postimplantation rat embryos. Serum from women with normal pregnancies had no adverse effect on rat embryo growth and development. Serum from 10 of the women with affected fetuses had a deleterious effect on the rat embryos as abnormalities of neural tube closure were observed in 28% of the conceptuses compared to only 1.3% of the embryos cultured in control serum.

Adolescent↗

PubMed1994

Valproic acid-induced neural tube defects.

Antiepileptic drug therapy with valproic acid (VPA) during early pregnancy can result in a 1-2% incidence of spina bifida aperta, a closure defect of the posterior neural tube in the human. The predominant defect produced by VPA in the mouse is exencephaly, a closure defect of the anterior neural tube. An appropriate dosing regimen (consecutive doses of VPA on Day 9 of gestation) can also result in a low incidence of spina bifida aperta and a high incidence of spina bifida occulta in the mouse. It is likely that the parent drug and not a metabolite is the proximate teratogen. Structure-activity relationships show a strict structural requirement for high teratogenic potency: the molecule must contain an alpha-hydrogen atom, a carboxyl function and branching on C-2 with two chains containing three carbon atoms each for maximum activity. If these two carbon chains are different, then enantiomers are present. Pairs of enantiomers were synthesized and shown to be significantly different in regard to teratogenic potency. Both enantiomers of each compound reach the embryo to the same degree, therefore, the intrinsic teratogenic activity of the enantiomers differs. This suggests that stereoselective interaction occurs between the drugs and a chiral structure within the embryo. The molecular mechanism of the teratogenicity of VPA is not known; one hypothesis is that VPA interacts with embryonic folate metabolism.

Animals↗

PubMed1994