Periconceptional vitamin use, dietary folate, and the occurrence of neural tube defects

Investigation of inter-individual variability of the one-carbon folate pathway: a bioinformatic and genetic review

Genetic polymorphisms in the one-carbon folate pathway have been widely studied in association with a number of conditions. Most of the research has focused on the 677C>T polymorphism in the coding region of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. However, there are a total of 25 genes in this pathway coding for enzymes, transporters and receptors, which can be investigated using 267 tagging single nucleotide polymorphisms (SNPs); using SNP database (dbSNP), 38 non-synonymous SNPs with a minor allele frequency of >5% are present in these genes. Most of these variants have not been investigated in relation to disease or drug response phenotypes. In addition, their functional consequences are largely unknown. Prediction of the functional effect using six publicly available programs (PolyPhen, SIFT BLink, PMut, SNPs3D, I-Mutant2.0 and LS-SNP) was limited to functionally well-characterized SNPs such as MTHFR c.677C>T and c.1298A>C ranking low. Epigenetic modifications may also be important with some of these genes. In summary, to date, investigation of the one-carbon folate pathway genes has been limited. Future studies should aim for a more comprehensive assessment of this pathway, while further research is also required in determining the functional effects of these genetic variants.

Folic acid, methylation and neural tube closure in humans

This review provides a brief description of folate use and folic acid metabolism in relation to neural tube defect (NTD) risk. First, a meta-analysis of reduction in NTD recurrence and occurrence risk with periconceptional folic acid supplementation is presented. Second, an overview of the complex folate metabolism is given. Third, SNPs for genes involved in folate and homocysteine metabolism that have been studied in relation to NTD riskare discussed. Fourth, the questions whether folate receptor autoantibodies or hampered methylation are mechanisms underlying NTDs are briefly discussed.

Nutrient pathways and neural tube defects: a semi-Bayesian hierarchical analysis

BACKGROUND

We used conventional and hierarchical logistic regression to examine the association of neural tube defects (NTDs) with intake of 26 nutrients that contribute to the mechanistic pathways of methylation, glycemic control, and oxidative stress, all of which have been implicated in NTD etiology. The hierarchical approach produces more plausible, more stable estimates than the conventional approach, while adjusting for potential confounding by other nutrients.

METHODS

Analyses included 386 cases and 408 nonmalformed controls with complete data on nutrients and potential confounders (race/ethnicity, education, obesity, and intake of vitamin supplements) from a population-based case-control study of deliveries in California from 1989 to 1991. Nutrients were specified as continuous, and their units were standardized to have a mean of zero and standard deviation (SD) of 1 for comparability of units across pathways. ORs reflect a 1-SD increase in the corresponding nutrient.

RESULTS

Among women who took vitamin supplements, semi-Bayesian hierarchical modeling results suggested no associations between nutrient intake and NTDs. Among women who did not take supplements, both conventional and hierarchical models (HM) suggested an inverse association between lutein intake and NTD risk (HM odds ratio [OR] = 0.6; 95% confidence interval = 0.5-0.9) and a positive association with sucrose (HM OR 1.4; 1.1-1.8) and glycemic index (HM OR 1.3; 1.0-1.6).

CONCLUSIONS

Our findings for lutein, glycemic index, and sucrose suggest that further study of NTDs and the glycemic control and oxidative stress pathways is warranted.

Regulation of folate receptor 1 gene expression in the visceral endoderm

BACKGROUND

Nutrient supply to the developing mammalian embryo is a fundamental requirement. Before completion of the chorioallantoic placenta, the visceral endoderm plays a crucial role in nurturing the embryo. We have found that visceral endoderm cells express folate receptor 1, a high-affinity receptor for the essential micronutrient folic acid, suggesting that the visceral endoderm has an important function for folate transport to the embryo. The mechanisms that direct expression of FOLR1 in the visceral endoderm are unknown.

METHODS

Sequences were tested for transcriptional activation capabilities in the visceral endoderm utilizing reporter gene assays in a cell model for extraembryonic endoderm in vitro, and in transgenic mice in vivo.

RESULTS

With F9 embryo carcinoma cells as a model for extraembryonic endoderm, we demonstrate that the P4 promoter of the human FOLR1 gene is active during differentiation of the cells towards visceral endoderm. However, transgenic mouse experiments show that promoter sequences alone are insufficient to elicit reporter gene transcription in vivo. Using sequence conservation as guide to choose genomic sequences from the human FOLR1 gene locus, we demonstrate that the sequence termed F1CE2 exhibits specific enhancer activity in F9 cells in vitro, in the visceral endoderm, and later the yolk sac in transgenic mouse embryos in vivo. We further show that the transcription factor HNF4-alpha can activate this enhancer sequence.

CONCLUSIONS

We have identified a transcriptional enhancer sequence from the FOLR1 locus with specific activity in vitro and in vivo, and suggest that FOLR1 is a target for regulation by HNF4-alpha.

The search for genetic polymorphisms in the homocysteine/folate pathway that contribute to the etiology of human neural tube defects

In this paper, we trace the history of current research into the genetic and biochemical mechanisms that underlie folate-preventable neural tube defects (NTDs). The inspired suggestion by Smithells that common vitamins might prevent NTDs ignited a decade of biochemical investigations-first exploring the nutritional and metabolic factors related to NTDs, then onto the hunt for NTD genes. Although NTDs were known to have a strong genetic component, the concept of common genetic variance being linked to disease risk was relatively novel in 1995, when the first folate-related polymorphism associated with NTDs was discovered. The realization that more genes must be involved started a rush to find polymorphic needles in genetic haystacks. Early efforts entailed the intellectually challenging and time-consuming task of identifying and analyzing candidate single nucleotide polymorphisms (SNPs) in folate pathway genes. Luckily, human genome research has developed rapidly, and the search for the genetic factors that contribute to the etiology of human NTDs has evolved to mirror the increased level of knowledge and data available on the human genome. Large-scale candidate gene analysis and genome-wide association studies are now readily available. With the technical hurdles removed, the remaining challenge is to gather a sample large enough to uncover the polymorphisms that contribute to NTD risk. In some respects the real work is beginning. Although moving forward is exciting, it is humbling that the most important result-prevention of NTDs by maternal folic acid supplementation-was achieved years ago, the direct result of Smithells' groundbreaking studies.

Proposal of a Mediterranean diet index for pregnant women

Numerous studies have addressed the nutritional needs of pregnant women. The nutritional status of the woman before and during gestation affects the growth of the fetus and the course of the pregnancy and influences the risk of obesity for mother and infant. The aim of this study was to propose a diet quality index for pregnancy based on a Mediterranean-type diet (MDS-P), evaluating the diet of a group of pregnant women by applying the Mediterranean Diet Score (MDS) and evaluating their intake of micronutrients required in optimal amounts during pregnancy, such as Fe, folic acid and Ca. The data used to construct this index (MDS-P) were gathered by means of a FFQ specifically designed for pregnant women. The mean MDS of this group, was 4.31 (sd 1.32), considered to represent satisfactory compliance with the Mediterranean diet (range 0-8). The mean MDS-P (range 0-11), which also takes account of dietary intake or supplements of folic acid, Fe and Ca was 7.53 (sd 1.44), indicating a compliance of around 70 %. The present study findings suggest that the MDS-P, which evaluates the adequacy of folic acid, Fe and Ca as well as compliance with the Mediterranean diet, may represent a valid tool for the specific assessment of the diet of pregnant women living in countries in the Mediterranean area. Further studies are required to complete the validation process.

Maternal fumonisin exposure as a risk factor for neural tube defects

Fumonisins are mycotoxins produced by the fungus F. verticillioides, a common contaminant of maize (corn) worldwide. Maternal consumption of fumonisin B(1)-contaminated maize during early pregnancy has recently been associated with increased risk for neural tube defects (NTDs) in human populations that rely heavily on maize as a dietary staple. Experimental administration of purified fumonisin to mice early in gestation also results in an increased incidence of NTDs in exposed offspring. Fumonisin inhibits the enzyme ceramide synthase in de novo sphingolipid biosynthesis, resulting in an elevation of free sphingoid bases and depletion of downstream glycosphingolipids. Increased sphingoid base metabolites (i.e., sphinganine-1-phosphate) may perturb signaling cascades involved in embryonic morphogenesis by functioning as ligands for sphingosine-1-P (S1P) receptors, a family of G-protein-coupled receptors that regulate key biological processes such as cell survival/proliferation, differentiation and migration. Fumonisin-induced depletion of glycosphingolipids impairs expression and function of the GPI-anchored folate receptor (Folr1), which may also contribute to adverse pregnancy outcomes. NTDs appear to be multifactorial in origin, involving complex gene-nutrient-environment interactions. Vitamin supplements containing folic acid have been shown to reduce the occurrence of NTDs, and may help protect the developing fetus from environmental teratogens. Fumonisins appear to be an environmental risk factor for birth defects, although other aspects of maternal nutrition and genetics play interactive roles in determining pregnancy outcome. Minimizing exposures to mycotoxins through enhanced agricultural practices, identifying biomarkers of exposure, characterizing mechanisms of toxicity, and improving maternal nutrition are all important strategies for reducing the NTD burden in susceptible human populations.

Neural tube defects and maternal folate intake among pregnancies conceived after folic acid fortification in the United States

Rates of neural tube defects have decreased since folic acid fortification of the food supply in the United States. The authors' objective was to evaluate the associations between neural tube defects and maternal folic acid intake among pregnancies conceived after fortification. This is a multicenter, case-control study that uses data from the National Birth Defects Prevention Study, 1998-2003. Logistic regression was used to compute crude and adjusted odds ratios between cases and controls assessing maternal periconceptional use of folic acid and intake of dietary folic acid. Among 180 anencephalic cases, 385 spina bifida cases, and 3, 963 controls, 21.1%, 25.2%, and 26.1%, respectively, reported periconceptional use of folic acid supplements. Periconceptional supplement use did not reduce the risk of having a pregnancy affected by a neural tube defect. Maternal intake of dietary folate was not significantly associated with neural tube defects. In this study conducted among pregnancies conceived after mandatory folic acid fortification, the authors found little evidence of an association between neural tube defects and maternal folic acid intake. A possible explanation is that folic acid fortification reduced the occurrence of folic acid-sensitive neural tube defects. Further investigation is warranted to possibly identify women who remain at increased risk of preventable neural tube defects.

Invited commentary: Preventing neural tube defects and more via food fortification?

Many neural tube defects can be prevented if women take folic acid around the time of conception. However, the majority of women do not take folic acid at the critical time, so the US government required that food be fortified with folic acid effective January 1, 1998. Whether the amount being added was sufficient to prevent all folate-related neural tube defects has been hotly debated. Mosley et al. (Am J Epidemiol. 2008;169(1):9-17) found no evidence that folic acid supplement use or dietary folate intake was related to neural tube defects, indicating that fortified food is probably providing sufficient folic acid to prevent folate-related defects. Because data on the effectiveness of fortification in the United States are scarce, this is an important contribution. There is great interest in the other effects of fortification. Folic acid reduces homocysteine levels, and homocysteine has been linked to cardiovascular disease and cancer. On the basis of current evidence, however, it seems unlikely that fortification will reduce cardiovascular disease rates. Its effect on cancer remains unclear. Folic acid may be useful in primary prevention but may also stimulate the growth of existing malignancies or premalignant lesions. Although these issues remain unresolved, Mosley et al. have provided important data to address the primary question: Does fortification prevent folate-related neural tube defects?

Gene-nutrient interactions: importance of folic acid and vitamin B12 during early embryogenesis

The role that nutritional factors play in mammalian development has received renewed attention over the past two decades as the scientific literature has exploded with reports that folic acid supplementation in the periconceptional period can protect embryos from a number of highly significant malformations. As is often the case, the relationship between B vitamin supplementation and improved pregnancy outcomes is more complicated than initially perceived, as the interaction between nutritional factors and selected genes must be considered. In this review, we attempt to summarize the complex clinical and experimental literature on nutritional factors, their biological transport mechanisms, and interactions with genetic polymorphisms that impact early embryogenesis. While not exhaustive, our goal was to provide an overview of important gene-nutrient interactions, focusing on folic acid and vitamin B12, to serve as a framework for understanding the multiple roles they play in early embryogenesis.

Improper supplementation habits of folic acid intake by Hungarian pregnant women: improper recommendations

BACKGROUND

Neural tube defects (NTDs) are some of the most common congenital anomalies. Proper folic acid supplementation is a dominant risk factor, which has been shown to decrease the incidence of NTDs. In Canada, the incidence of neuroblastoma has presented a considerable decrease of 60% as a result of enrichment cereal grain flours with synthetic folic acid. The aim of this study was to investigate the effect of folic acid intake by pregnant women on the incidence of NTDs and neuroblastoma.

METHODS

Regular folic acid intake has been recommended to pregnant women in Hungary since the eighties of the last century by health visitors eventually raking effect as an official protocol which had been released in 1997. During 2001, 2002 and 2003, folic acid intake habits of pregnant women were evaluated by health visitors, proving to be successful in collecting data from 95.06% of the pregnant women. The incidence of NTDs has been registered by the Hungarian National Centre of Epidemiology, Department of Human Genetics and Teratology. The Pediatric Cancer Registry provided the incidence of neuroblastoma in children.

RESULTS

Consistent findings revealed a regular intake of supplementary folic acid products by 68.71% of the pregnant women. Out of these, 93.13% of pregnant women who were taking folic acid, started the supplementation after their 7 weeks of pregnancies, a time designated as the completion period of the development of the neural tube. The dose of folic acid supplementation was evaluated as less than 5 mg/day in 84.75% of the pregnant women. In Hungary, the incidence of NTDs has remained constant, while the incidence of neuroblastoma has shown constant slight increase in spite of the introduction of folic acid supplementation in 1997.

CONCLUSIONS

Based on our experience, folic acid supplementation was initiated after the recognition of pregnancy and its application in a dose of lower than 5 mg/day neither decreased the incidence of NTDs nor did it have an effect on the neuroblastoma incidence. It is implicated that proper folic acid supplementation, which is started from the conception, can be achieved only with the enrichment of cereal grain flours.

Prevention of NTDs with periconceptional multivitamin supplementation containing folic acid in China

BACKGROUND

Maternal nutritional factors seem to contribute substantially to the complex etiologies of NTDs. Foremost among these factors is the periconceptional use of supplementation containing folic acid, which is associated with a reduction in the risk of women having NTD-affected pregnancies. This study was designed to observe the effectiveness of multivitamin supplementation containing folic acid in preventing NTDs in a Chinese population and to detect factors that would impact the effectiveness.

METHODS

Through family planning networks, a population-based community intervention study was carried out in 18 counties of China. Participants were divided into an intervention (taking multivitamin) group and a control group, and were followed up according to periconceptional multivitamin supplementation (in general 6 mg) for 2 years. Women who had a pregnancy were followed up from 28 weeks gestation at least to pregnancy termination, and the outcome was recorded. The incidence rate of the two groups and the relative risks were calculated to evaluate the efficacy of the multivitamin supplement in preventing NTDs.

RESULTS

During 2000 and 2002, all of the women having pregnancies with birth defects and women whose pregnancies were without any birth defects were interviewed. Nine NTDs were recorded from 25,444 pregnancies (NTD birth prevalence = 0.35/1,000 pregnancies) in the intervention group and 48 NTDs among 26,599 pregnancies (NTD birth prevalence = 1.80/1,000 pregnancies) in the control group. The protective rate was 80.4%.

CONCLUSIONS

Periconceptional multivitamin supplementation containing folic acid can prevent the occurrence of NTDs with the beneficial effect dependent on the frequency and timing of the supplementation. Our study suggests that multivitamin supplement containing folic acid taken from a time point of 2 months before conception and continuing until completion of the second month after conception and taken more than five times per week can significantly reduce the risks of NTDs.

Determinants of folic acid use in early pregnancy in a multi-ethnic urban population in The Netherlands: the Generation R study

OBJECTIVE

Recommendations on folic acid use to prevent neural tube defects have been launched in several countries. Adequate folic acid use seems to be low. This study assesses the prevalence of folic acid use and identifies its determinants.

METHODS

The study was embedded in the Generation R Study Rotterdam, the Netherlands, a population-based prospective cohort study between 2002 and 2006. Complete information of 6940 women was available. Information on folic acid use and potential determinants was obtained by questionnaires and physical examination.

RESULTS

Of all women 37% adequately used folic acid during the preconception period. Most important risk factors for inadequate use were unplanned pregnancy (OR 9.5, CI 7.2-12.4, p<0.001), low educational level (OR 2.5, CI 1.8-3.6, p<0.001) and non-western ethnicity, (OR 3.5, CI 2.9-4.3, p<0.001). After stratification for ethnicity, unplanned pregnancy remained the most important risk factor for inadequate use. Other risk factors for inadequate use were younger age, single marital status, smoking, multiparity (all p<0.001) and alcohol use (p<0.05). In contrast, previous spontaneous abortion decreased the risk of inadequate folic acid use (p<0.001).

CONCLUSION

Adequate preconception folic acid supplementation is still too low. Implementation of preconception programs and other public health strategies are strongly needed.

Assessing awareness, knowledge and use of folic acid in Kansas women between the ages of 18 and 44 years

Taking folic acid daily, before and during early pregnancy, has been proven to reduce neural tube birth defects (NTD). Unfortunately, many women fail to take it daily as recommended.

OBJECTIVES

To assess women's self-reported awareness, knowledge and use of folic acid. Methods Data were obtained by cross-sectional, random digit-dialing, computer-assisted telephone interviews with 250 women in Kansas. Associations were determined by chi-squared analysis.

RESULTS

Eighty-eight percent of childbearing age women in Kansas have a general awareness of folic acid, 20% have knowledge that it reduces birth defects, but only 25% report taking it daily. Awareness was associated with high school or greater education (P < .0001), incomes over $25,000 (P = 0.0003), being married (P = 0.0035), being white (P = 0.0135), having health insurance (P = 0.0152) and being capable of pregnancy (P = 0.0119). Knowledge that folic acid reduces birth defects was associated with being aware of the USPHS recommendation (P < .0001), being capable of pregnancy (P = 0.0043), being pregnant (P = 0.0061), and being aware of folic acid (P = 0.0379). Taking folic acid daily was associated with currently being pregnant (P = 0.0126).

CONCLUSIONS

Women less likely to take folic acid on a daily basis were young, non-Caucasians who reported less education, less income and no health insurance. Based upon these data, multi-level education campaigns that specifically target lower-SES women should be considered.

Theory of planned behavior and multivitamin supplement use in Caucasian college females

The objective of this study was to identify predictors of the use of multivitamin supplements (MVS) among Caucasian college females utilizing the Theory of Planned Behavior (TPB). Variables of the TPB and the self-reported use of multivitamin supplements were measured by two separate surveys within 1 week with a convenience sample of 96 Caucasian college student females. Two attitudinal beliefs and one control belief significantly predicted behavioral intention to use multivitamin. A belief that taking multivitamin supplements helps to feel and look good was the most important predictor of the use of multivitamin supplements. EDITORS' STRATEGIC IMPLICATIONS: Findings from this study, although in need of replication, suggest that prevention campaigns would be more successful if messages used to reach these females were consistent with perceived beliefs regarding benefits of using MVS. More broadly, TPB appears to offer a useful framework for understanding or predicting behavior based on psychological constructs theorized to influence behavior.

Embryonic development in the reduced folate carrier knockout mouse is modulated by maternal folate supplementation

BACKGROUND

The reduced folate carrier (RFC1) is a ubiquitously expressed integral membrane protein that mediates delivery of 5-methyltetrahydrofolate into mammalian cells. In this study, embryonic/fetal development is characterized in an RFC1 knockout mouse model in which pregnant dams receive different levels of folate supplementation.

METHODS

RFC1(+/-) males were mated to RFC1(+/-) females, and pregnant dams were treated with vehicle (control) or folic acid (25 or 50 mg/kg) by daily subcutaneous injection (0.1 mL/10 g bwt), beginning on E0.5 and continuing throughout gestation until the time of sacrifice.

RESULTS

Without maternal folate supplementation, RFC1 nullizygous embryos die shortly postimplantation. Supplementation of pregnant dams with 25 mg/kg/day folic acid prolongs survival of mutant embryos until E9.5-E10.5, but they are developmentally delayed relative to wild-type littermates, display a marked absence of erythropoiesis, severe neural tube and limb bud defects, and failure of chorioallantoic fusion. Fgfr2 protein levels are significantly reduced or absent in the extraembryonic membranes of RFC1 nullizygous embryos. Maternal folate supplementation with 50 mg/kg/day results in survival of 22% of RFC1 mutants to E18.5, but they develop with multiple malformations of the eyelids, lungs, heart, and skin.

CONCLUSIONS

High doses of daily maternal folate supplementation during embryonic/fetal development are necessary for early postimplantation embryonic viability of RFC1 nullizygous embryos, and play a critical role in chorioallantoic fusion, erythropoiesis, and proper development of the neural tube, limbs, lungs, heart, and skin.

Epidemiology, etiology, pathogenesis, and diagnosis of recurrent bacterial meningitis

Recurrent bacterial meningitis is a rare phenomenon and generally poses a considerable diagnostic challenge to the clinician. Ultimately, a structured approach and early diagnosis of any underlying pathology are crucial to prevent further episodes and improve the overall outcome for the affected individual. In this article, we are reviewing the existing literature on this topic over the last two decades, encompassing 363 cases of recurrent bacterial meningitis described in 144 publications. Of these cases, 214 (59%) were related to anatomical problems, 132 (36%) were related to immunodeficiencies, and 17 (5%) were related to parameningeal infections. The review includes a detailed discussion of the underlying pathologies and microbiological aspects as well as recommendations for appropriate diagnostic pathways for investigating this unusual entity.

Effect of different dosage and administration schedules of folic acid on blood folate levels in a population of Honduran women of reproductive age

Background

Observational studies and clinical trials have shown conclusive evidence that periconceptional folic acid supplementation prevents up to 70 % of neural tube defects (NTD). The Honduran government wanted to implement a supplementation programme of folic acid but needed to assess the relative effects of two dosages of folic acid.

Objective

To determine the effect of two dosages of folic acid on blood folate levels in Honduran female factory workers aged 18 to 49 years.

Design

This was a randomized, double-blind control supplementation trial conducted in Choloma, Honduras. A total of 140 eligible women were randomly assigned to two dosage groups and followed up for 12 weeks. One group received a daily dosage of 1 mg folic acid and the other a once weekly dosage of 5 mg. Serum folate and red blood cell folate levels were determined by radioassay at baseline, 6 weeks and 12 weeks.

Results

Serum folate levels increased from 6·3 (se 0·2) to 14·9 (se 0·6) ng/ml (P < 0·0001) in women assigned to the 1 mg/d group and from 6·9 (se 0·3) to 10·1 (se 0·4) ng/ml (P < 0·0001) in those assigned to the 5 mg/week group. Red blood cell folate concentrations also increased significantly in both groups, albeit more slowly. Educational level, age and BMI were not associated with the changes in serum and red blood cell folate levels during the supplementation period. However, a differential effect on serum folate levels by dosage group and time was observed.

Conclusions

Although both folate supplementation regimens increased serum and red blood cell folate levels significantly among the women studied, blood folate levels that are considered to be protective of NTD were reached faster with the daily dosage of 1 mg folic acid.

Effect of anti-epileptic drugs in pregnancy and teratogenesis

Epilepsy raises special concern in women during pregnancy. Antiepileptic drugs are known to induce major and minor malformations in the foetus. Aim of the study was to find an association between maternal serum alpha fetoprotein levels, foetal abnormalities and antiepileptic drugs mediated teratogenicity. Maternal serum alpha feto protein levels, kidney and liver function tests in age matched normal pregnant women and seizure free epileptic pregnant women during 12-14 weeks of gestation were estimated. Cases were subjected to ultrasonography at 11(th)-14(th) week of pregnancy and again at 20(th) week of pregnancy. maternal serum alfa feto protein was assayed by a specific Electro Chemiluminescence Immuno Assay test. There was no significant difference in kidney and liver function tests in cases as compared to controls. There were elevated levels of alpha feto protein in cases as compared to controls but this was not statistically significant. No anomalies were detected in ultrasound reports. Most women had normal full term delivery with healthy children but of low birth weight. No correlation was seen between maternal serum alfa feto protein levels and antiepileptic drug leading to teratogenesis.

Folate-mediated one-carbon metabolism and neural tube defects: balancing genome synthesis and gene expression

Neural tube defects (NTDs) refer to a cluster of neurodevelopmental conditions associated with failure of neural tube closure during embryonic development. Worldwide prevalence of NTDs ranges from approximately 0.5 to 60 per 10,000 births, with regional and population-specific variation in prevalence. Numerous environmental and genetic influences contribute to NTD etiology; accumulating evidence from population-based studies has demonstrated that folate status is a significant determinant of NTD risk. Folate-mediated one-carbon metabolism (OCM) is essential for de novo nucleotide biosynthesis, methionine biosynthesis, and cellular methylation reactions. Periconceptional maternal supplementation with folic acid can prevent occurrence of NTDs in the general population by up to 70%; currently several countries fortify their food supply with folic acid for the prevention of NTDs. Despite the unambiguous impact of folate status on NTD risk, the mechanism by which folic acid protects against NTDs remains unknown. Identification of the mechanism by which folate status affects neural tube closure will assist in developing more efficacious and better targeted preventative measures. In this review, we summarize current research on the relationship between folate status and NTDs, with an emphasis on linking genetic variation, folate nutriture, and specific metabolic and/or genomic pathways that intersect to determine NTD outcomes.

Administration of folate-producing bifidobacteria enhances folate status in Wistar rats

To develop a probiotic that provides the host with folate, we administered folate-overproducing bifidobacteria (Bifidobacteria adolescentis MB 227, B. adolescentis MB 239, and B. pseudocatenulatum MB 116) to Wistar rats with induced folate deficiency. Four groups of rats were fed a solid, low-folate diet with no supplements, folate-producing bifidobacteria [probiotic (PRO)], oligofructose [prebiotic (PRE)], or PRO plus PRE [symbiotic (SYM)] for 14 d. The SYM group also had a significantly higher (16.4 +/- 3.7 nmol/L) than in the PRO group (9.1 +/- 0.3 nmol/L), which was greater than in the control (4.8 +/- 0.5 nmol/L) and PRE groups (5.3 +/- 1.4 nmol/L). The SYM group also had a significantly higher hepatic folate concentration than in the other groups, whereas the kidney folate concentration did not differ among the groups. In the unsupplemented group, the pH of feces did not change during the trial, whereas diets containing bifidobacteria and/or oligofructose led to significant acidification due to enhanced saccharolytic metabolism. As a consequence of feeding rats PRE, PRO, and SYM diets, lactobacilli and bifidobacteria were significantly greater than in controls, whereas coliforms and enterococci were lower. This experiment showed that B. adolescentis MB 227, B. adolescentis MB 239, and B. pseudocatenulatum MB 116 exert both the beneficial effects of probiotics and produce folate in vivo, positively affecting the folate status of rats. The simultaneous administration of oligofructose and folate-producing bifidobacteria enhance their effectiveness on folate status. This study provides new perspectives on the specific use of probiotics to deliver important vitamins such as folate.

Folic acid and cognition in older persons

Folic acid supplementation has drawn much attention in recent years for the prevention of Alzheimer's disease and cognitive decline. In this review, the authors describe how current evidence does not support the use of folic acid supplements to protect against cognitive decline. Although a few studies suggest that folic acid supplementation may provide neuroprotection among persons who are folate deficient, there is also data to indicate that supplementation in persons without folate deficiency may pose a risk to neurological function. Vitamin B12 deficiency is common in old age and may not be easy to recognise. Folic acid supplementation may mask the anaemia associated with vitamin B12 deficiency and, therefore, may delay treatment while allowing progression of neurological symptoms. Whether or not folic acid supplementation exacerbates neurological symptoms of vitamin B12 deficiency is not clear. Further studies are needed to determine the possible risks and benefits of folic acid supplementation in older persons.

High prevalence of NTDs in Shanxi Province: A combined epidemiological approach

BACKGROUND

Shanxi Province has historically reported a high prevalence of NTDs. In order to establish baseline rates for NTDs and discuss the risk factors associated with sociodemographic, maternal characteristics, and geographic factors, we performed the present study using an approach combining population and hospital-based methodologies.

METHODS

We used chi(2) and Fisher's exact tests to evaluate variation in the prevalence by selected covariates and computed crude ORs and 95% CIs. Adjusted odds ratios (AORs) were performed using logistic regression with all the covariates included in the model.

RESULTS

The overall NTD prevalence during the 3 year study period was 199.38 per 10,000 births, with a higher NTD prevalence clustered in 46 villages within this geographic area. However, no statistical significance was found between NTD prevalence and the elevation of the villages or their distance from coal plants. AORs revealed women aged 20 and above had a lower risk of NTDs compared to those younger than 20 (AOR range 0.4-0.5). A higher risk of NTDs was observed among female infants (AOR 1.50; 95% CI: 1.04-2.17), women with four or more previous births (AOR 2.80; 95% CI: 1.20-6.52), and a previous history of birth defects (AOR 3.23; 95% CI: 1.46-7.12).

CONCLUSIONS

This study has documented a high prevalence of NTDs in Shanxi. Similar variations to other reports were found in the risk of NTDs by maternal demographic characteristics and a clustering of NTDs in certain villages that require further exploration.

Maternal residence near agricultural pesticide applications and autism spectrum disorders among children in the California Central Valley

BACKGROUND

Ambient levels of pesticides ("pesticide drift") are detectable at residences near agricultural field sites.

OBJECTIVE

Our goal was to evaluate the hypothesis that maternal residence near agricultural pesticide applications during key periods of gestation could be associated with the development of autism spectrum disorders (ASD) in children.

METHODS

We identified 465 children with ASD born during 1996-1998 using the California Department of Developmental Services electronic files, and matched them by maternal date of last menstrual period to 6,975 live-born, normal-birth-weight, term infants as controls. We determined proximity to pesticide applications using California Department of Pesticide Regulation records refined using Department of Water Resources land use polygons. A staged analytic design applying a priori criteria to the results of conditional logistic regressions was employed to exclude associations likely due to multiple testing error.

RESULTS

Of 249 unique hypotheses, four that described organochlorine pesticide applications--specifically those of dicofol and endosulfan--occurring during the period immediately before and concurrent with central nervous system embryogenesis (clinical weeks 1 through 8) met a priori criteria and were unlikely to be a result of multiple testing. Multivariate a posteriori models comparing children of mothers living within 500 m of field sites with the highest nonzero quartile of organochlorine poundage to those with mothers not living near field sites suggested an odds ratio for ASD of 6.1 (95% confidence interval, 2.4-15.3). ASD risk increased with the poundage of organochlorine applied and decreased with distance from field sites.

CONCLUSIONS

The association between residential proximity to organochlorine pesticide applications during gestation and ASD among children should be further studied.

Folate promotion in Western Australia and the prevention of neural tube defects

OBJECTIVES

We conducted a case-control study to investigate the effectiveness of efforts to increase folate intake in Western Australia (WA) for the prevention of neural tube defects (NTD).

METHODS

Case (36) and control (578) mothers completed questionnaires, from which their intake of folate from supplements and food (including fortified foods) was estimated.

RESULTS

Almost one-third of women took folic acid supplements periconceptionally. Supplement use was associated with a non-significant 4% reduction in risk. For women not taking supplements, dietary sources of folate were protective, and most women obtained at least some folate from fortified food.

CONCLUSIONS

For the two-thirds of WA women not taking supplements, fortified food is an important source of folate for the prevention of NTD.

IMPLICATIONS

Greater promotion of foods currently allowed to be fortified with folate, or mandatory fortification, is needed to maximise prevention of NTD in Australia.

Assessment of the potential effect of incremental increases in folic acid intake on neural tube defects in Australia and New Zealand

OBJECTIVE

To estimate the number of neural tube defects that could be prevented in Australia and New Zealand by increasing levels of folic acid intake.

METHODS

Available data on prevalence of neural tube defects in Australia and New Zealand, folic acid supplement use and serum folate were used in a published model to estimate the number of neural tube defects that could be prevented in Australia and New Zealand for increments of folic acid intake from 0.1 mg daily to 1 mg daily.

RESULTS

An increase of 0.2 mg folic acid per day was estimated to result in the prevention of 49 (95% CI 27-84) neural tube defects per year in Australia and 11 (95% CI 6-18) in New Zealand. A separate estimation for Indigenous Australians found that 0.2 mg of folic acid daily could prevent 7 (95% CI 4-11) neural tube defects in Indigenous infants per year.

CONCLUSIONS

These data should be useful in considering primary preventive strategies for neural tube defects, including the possible introduction of mandatory fortification of food with folic acid. The estimates are imprecise because of limitations in the data used in the model.

IMPLICATIONS

More representative and precise data on neural tube defects, serum folate levels and use of folic acid supplements from all Australian States and New Zealand are needed to refine the output from the model and to provide a baseline assessment of folate status against which to measure the effects of any future interventions to prevent neural tube defects.

Mandatory folic acid fortification in Newfoundland and Labrador

PURPOSE

Dietary folic acid (FA) intakes were analyzed in random samples of 302 young women (aged 18 to 34) and 337 seniors (aged 65 to 74) residing in Newfoundland and Labrador (NL). The analyses were an attempt to estimate the amount of FA they would consume solely because of mandatory fortification of foods.

METHODS

Secondary analysis was performed on raw data collected through single 24-hour recalls as part of a larger study.

RESULTS

The dietary FA contributed by fortified foods eaten in the specified amounts was estimated to be 136 to 148 mcg/day (226 to 247 DFE/day) for young women and 151 to 160 mcg/day (252 to 267 DFE/day) for seniors. Most of this FA was contributed to the diet by enriched white flour.

CONCLUSIONS

Mandatory fortification of foods appears to have improved the total mean intake of folate by young women and seniors residing in NL.

Assessment of Turkish women's knowledge concerning folic acid and prevention of birth defects

Objectives:

In Turkey, the incidence of neural tube defects (NTDs) is 30.1 per 10 000 births. For this reason it seems an important problem for women of childbearing age. Adequate periconceptional consumption of folic acid could prevent NTDs. Most women are unaware of this recommendation. The objectives of this study were to evaluate women' knowledge and beliefs with regard to folic acid, and to estimate the consumption frequency of vitamin supplements periconceptionally and during the first trimester of pregnancy.

Design:

Eight hundred and eighteen married women who had delivered a live-born infant within the previous 12 months completed the questionnaire. Each subject participated in a 20-minute interview, with the questionnaire comprising multiple-choice statements. A random sample of 10 public health centres was drawn from 27 in three districts in Konya where about 50% of the population lives.

Results:

Only 22% of subjects had heard or read about folic acid. Thirteen per cent of women indicated knowledge of the direct link between folic acid supplementation and NTD prevention. The knowledge was greatest among 26- to 35-year-olds. Women with a university degree were more likely to have heard about folic acid than were less-educated women.

Conclusion:

The results indicate that further government efforts are needed to inform the population and promote the optimal use of folic acid supplements and folate-enriched foods. It is the responsibility of national authorities to increase health education concerning folic acid and the prevention of NTDs in their countries.

Folate and neural tube defects

A protective effect of folate against the development of neural tube defects (NTDs), specifically, anencephaly and spina bifida, is now well recognized, having been established by a chain of clinical research studies over the past half century. This article summarizes the more important of these studies, which have led to the current situation in which all women capable of becoming pregnant are urged to ingest folic acid regularly. The recommended intakes are 4 mg/d for those at high risk (by virtue of a previous NTD pregnancy outcome) and 0.4 mg/d for all others. However, a reduction in NTD births did not follow promulgation of these recommendations, and so folic acid fortification was mandated in the United States and some other countries. Although some controversy remains about the adequacy of fortification levels, the process was followed by significant improvement in folate indexes and a reduction of 25-30% in NTD frequency (about one-half of the proportion of cases assumed to be responsive to folate). The folate-NTD relation represents the only instance in which a congenital malformation can be prevented simply and consistently. Nevertheless, several research gaps remain: identification of the mechanism by which the defect occurs and how folate ameliorates it; characterization of the relative efficacy of food folate, folic acid added to foods, and folic acid by itself; delineation of the dose-response relations of folate and NTD prevention; and more precise quantification of the dose needed to prevent recurrences.

Prenatal multivitamin supplementation and rates of congenital anomalies: a meta-analysis

BACKGROUND

The use of folic acid-fortified multivitamin supplements has long been associated with decreasing the risk of neural tube defects. Several studies have also proposed the effectiveness of these supplements in preventing other birth defects; however, such effects have never been systematically examined.

OBJECTIVE

We conducted a systematic review and meta-analysis to evaluate the protective effect of folic acid-fortified multivitamin supplements on other congenital anomalies.

METHODS

We searched Medline, PubMed, EMBASE, Toxline, Healthstar, and Cochrane databases for studies describing the outcome of pregnancies in women using multivitamin supplements that were published in all languages from January 1966 to July 2005. The references from all collected articles were reviewed for additional articles. Two independent reviewers who were blinded to the source and identity of the articles extracted data based on predetermined inclusion and exclusion criteria. Using a random effects model, rates of congenital anomalies in babies born to women who were taking multivitamin supplements were compared with rates in the offspring of controls who were not.

RESULTS

From the initial search, 92 studies were identified; 41 of these met the inclusion criteria. Use of multivitamin supplements provided consistent protection against neural tube defects (random effects odds ratio[OR] 0.67, 95% confidence intervals [95% CI] 0.58-0.77 in case control studies; OR 0.52, 95% CI 0.39-0.69 in cohort and randomized controlled studies), cardiovascular defects (OR 0.78, 95% CI 0.67-0.92 in case control studies; OR 0.61, 95% CI 0.40-0.92 in cohort and randomized controlled studies), and limb defects (OR 0.48, 95% CI 0.30-0.76 in case control studies; OR 0.57, 95% CI 0.38-0.85 in cohort and randomized controlled studies). For cleft palate, case control studies showed OR 0.76 (95% CI 0.62-0.93), and cohort and randomized controlled studies showed OR 0.42 (95% CI 0.06-2.84); for oral cleft with or without cleft palate, case control studies showed OR 0.63 (95% CI 0.54-0.73), and cohort and randomized controlled studies showed OR 0.58 (95% CI 0.28-1.19); for urinary tract anomalies, case control studies showed OR 0.48 (95% CI 0.30-0.76), and cohort and randomized controlled studies showed OR 0.68 (95% CI 0.35-1.31); and for congenital hydrocephalus case control studies showed OR 0.37 (95% CI 0.24-0.56), and cohort and randomized controlled studies showed OR 1.54 (95% CI 0.53-4.50). No effects were shown in preventing Down syndrome, pyloric stenosis, undescended testis, or hypospadias.

CONCLUSION

Maternal consumption of folic acid-containing prenatal multivitamins is associated with decreased risk for several congenital anomalies, not only neural tube defects. These data have major public health implications, because until now fortification of only folic acid has been encouraged. This approach should be reconsidered.

The fetal origins of memory: the role of dietary choline in optimal brain development

Fetal nutrition sets the stage for organ function in later life. In this review we discuss the fetal and neonatal origins of brain function. Numerous research observations point to the importance of choline for the developing fetus and neonate. This essential nutrient is involved in 1-carbon metabolism and is the precursor for many important compounds, including phospholipids, acetylcholine, and the methyl donor betaine. Dietary intake of choline by the pregnant mother and later by the infant directly affects brain development and results in permanent changes in brain function. In rodents, perinatal supplementation of choline enhances memory and learning functions, changes that endure across the lifespan. Conversely, choline deficiency during these sensitive periods results in memory and cognitive deficits that also persist. Furthermore, recent studies suggest that perinatal choline supplementation can reduce the behavioral effects of prenatal stress and the cognitive effects of prenatal alcohol exposure in offspring. The likely mechanism for these effects of choline involves DNA methylation, altered gene expression, and associated changes in stem cell proliferation and differentiation. The currently available animal data on choline and hippocampal development are compelling, but studies are needed to determine whether the same is true in humans.

Neural tube defects and folate: case far from closed

Neural tube closure takes place during early embryogenesis and requires interactions between genetic and environmental factors. Failure of neural tube closure is a common congenital malformation that results in morbidity and mortality. A major clinical achievement has been the use of periconceptional folic acid supplements, which prevents approximately 50-75% of cases of neural tube defects. However, the mechanism underlying the beneficial effects of folic acid is far from clear. Biochemical, genetic and epidemiological observations have led to the development of the methylation hypothesis, which suggests that folic acid prevents neural tube defects by stimulating cellular methylation reactions. Exploring the methylation hypothesis could direct us towards additional strategies to prevent neural tube defects.

Maternal nutrient intakes and risk of orofacial clefts

BACKGROUND

Information about nutritional factors as potential risks of orofacial clefts is limited.

METHODS

In this population-based case-control study, we investigated whether periconceptional intakes of supplemental folic acid, dietary folate, and several other nutrients were associated with orofacial clefts. We included data on deliveries from 1997 through 2000 in the National Birth Defects Prevention Study. Orofacial cleft cases were infants or fetuses born with cleft palate (CP) or with cleft lip with or without cleft palate (CLP). Infants without malformations were eligible as controls. Interview participation was 71% among case mothers and 68% among control mothers. Interviews were completed for 704 CLP cases, 404 CP cases, and 2594 controls.

RESULTS

The odds ratio (OR) for CLP associated with use of vitamin supplements containing folic acid was 0.88 (95% confidence interval = 0.73-1.07) and for CP was 1.09 (0.84-1.40). Adjusting for maternal race/ethnicity, age, and education produced an OR of 1.01 (0.82-1.24) for CLP and 1.02 (0.77-1.34) for CP. We found some evidence for decreased CLP risks (>or=30% reduction in risk) with increasing intakes of total protein, choline, and methionine. Decreased CP risk was associated with increased intake of cysteine. Intakes of only 2 micronutrients, iron and riboflavin, were found to reduce CLP risk when adjusted for other nutrients.

CONCLUSION

Our observations contribute to the limited body of evidence suggesting a woman's periconceptional diet may influence clefting risks in her offspring. Our finding of no reduction in clefting risk with periconceptional use of supplements containing folic acid is inconsistent with many previous observations but not all.

Folic acid and the prevention of neural tube defects: A survey of awareness among Latina women of childbearing age residing in southeast Michigan

Periconceptional intake of folic acid is known to reduce the risk for neural tube defects (NTDs). To inform southeast Michigan Latina women of childbearing age about the benefits of food and supplemental sources of the micronutrient in the prevention of NTDs, Spanish-English bilingual health educators carried out 20 education events in supermarkets and community organizations serving Latina women. One hundred and sixty Latina women ages 19 to 50 years indicated their current folic acid awareness and stated their future intentions regarding folic acid. Of 160 women surveyed, 114 (71%) had heard of folic acid, 84 (74%) knew that folic acid prevents birth defects, 63 (55%) knew the critical time to take folic acid, and 76 (67%) identified at least one source of folic acid. After participating in the education events, 136 women (85%) reported planning to eat more folate and/or folic acid-rich foods. Although general folic acid awareness is fairly high, health promotion efforts must be coordinated at community locations serving Latina women to share folic acid's specific protective effects in the prevention of NTDs, the critical timing of intake, and its food and supplement sources.

Quantitative determination of erythrocyte folate vitamer distribution by liquid chromatography-tandem mass spectrometry

BACKGROUND

Given the role of folate in many disorders, intracellular distribution of folate vitamers is of potential clinical importance. In particular, accumulation of non-methyltetrahydrofolates due to altered partitioning of folate metabolism at the level of methylenetetrahydrofolate is of interest.

METHODS

We describe a positive-electrospray liquid chromatography tandem mass spectrometry (LC-MS/MS) method that allows determination of erythrocyte folate vitamer distribution by accurately measuring both 5-methyltetrahydrofolate (5-methylTHF) and non-methyl folate vitamers. Whole blood lysates are deconjugated in ascorbic acid solutions, deproteinized, purified using folate-binding protein affinity columns, concentrated by solid-phase extraction (SPE) and evaporation, and separated on a C18 column within 6 min.

RESULTS

The limit of quantification for both 5-methylTHF and non-methylTHF was 0.4 nmol/L (signal-to-noise >10). Intra- and inter-assay CVs for 5-methylTHF were 1.2% and 2.8%, respectively. Intra- and inter-assay CVs for non-methylTHF as a group were 1.6% and 1.5%, respectively. Recovery results were 97-107%. We measured 8-72% non-methyl folate vitamers in volunteers (n=5) with the methylenetetrahydrofolate reductase (MTHFR) 677 TT genotype. Concentrations ranged from 117 to 327 nmol/L and 23 to 363 nmol/L for 5-methylTHF and non-methylTHF vitamers, respectively. We measured 0-2% non-methylTHF vitamers in MTHFR 677 CC genotype volunteers. In addition, we found that storage of whole-blood samples in ascorbic acid at low pH resulted in 53-90% loss of the non-methylTHF fraction.

CONCLUSION

This LC-MS/MS method accurately determines erythrocyte 5-methylTHF and non-methyl folate vitamers.

Awareness and Use of Folic Acid Among Women in the Lower Mississippi Delta

CONTEXT

National and state efforts to increase folic acid awareness and use may not be reaching large segments of the population.

PURPOSE

This study examines folic acid awareness and use among women of childbearing age in a representative, economically at-risk rural sample and identifies factors that influence awareness and use.

METHODS

A cross-sectional random digit dialing telephone survey was completed with a representative sample of 646 women aged 14-45 years in 36 counties of the lower Mississippi Delta. Folic acid awareness and supplement use were estimated by percentages weighted to reflect the 36-county population. Pregnancy intentions and the ability to become pregnant were used to predict awareness and use among a subsample of sexually active women.

FINDINGS

Compared to national samples, Delta women were less likely to have heard of folic acid (75% vs 64%) or to take a regular (5-7 days/wk) folic acid supplement (34% vs 22%). The proportion of women who took regular folic acid supplements was very low among some subgroups: African Americans (14%), those 14-19 years of age (12%), and those with low incomes (13%) and low educational levels (14%). Of the women who reported being sexually active, the ability to become pregnant more than doubled their likelihood of regular supplement use.

CONCLUSIONS

The national folic acid campaign has not reached many women in the rural Mississippi Delta. A new mode of folic acid education is needed that is focused on low-income and young women and women not planning pregnancies. In the Delta and similar geographic regions, health care providers, black church leaders, and youth group leaders could be valuable advocates for folic acid.

Folate and human reproduction

The influence of folate nutritional status on various pregnancy outcomes has long been recognized. Studies conducted in the 1950s and 1960s led to the recognition of prenatal folic acid supplementation as a means to prevent pregnancy-induced megaloblastic anemia. In the 1990s, the utility of periconceptional folic acid supplementation and folic acid food fortification emerged when they were proven to prevent the occurrence of neural tube defects. These distinctively different uses of folic acid may well be ranked among the most significant public health measures for the prevention of pregnancy-related disorders. Folate is now viewed not only as a nutrient needed to prevent megaloblastic anemia in pregnancy but also as a vitamin essential for reproductive health. This review focuses on the relation between various outcomes of human reproduction (ie, pregnancy, lactation, and male reproduction) and folate nutrition and metabolism, homocysteine metabolism, and polymorphisms of genes that encode folate-related enzymes or proteins, and we identify issues for future research.

Neural tube defects and maternal residential proximity to agricultural pesticide applications

Residential proximity to applications of agricultural pesticides may be an important source of exposure to agents that have been classified as developmental toxins. Data on two case-control study populations of infants with neural tube defects (NTDs) and nonmalformed controls delivered in California between 1987 and 1991 were pooled to investigate whether maternal residential proximity to applications of specific pesticides or physicochemical groups of pesticides during early gestation increases the risk of these malformations. Maternal residential proximity within 1,000 m of pesticide applications was ascertained by linking mothers' addresses with agricultural pesticide use reports and crop maps. Odds ratios were computed by using conventional single- and multiple-pesticide and hierarchical multiple-pesticide logistic regression. In single-pesticide models, several pesticides were associated with NTDs after adjustment for study population, maternal ethnicity, educational level, cigarette smoking, and vitamin use. In a hierarchical multiple-pesticide model, effect estimates for only benomyl and methomyl suggested a possible association. Elevated risks of NTDs and anencephaly or spina bifida subtypes were also associated with exposures to chemicals classified as amide, benzimidazole, methyl carbamate, or organophosphorus pesticides and with increasing numbers of pesticides. These results suggest that ambient exposure to certain categories of agricultural pesticides may increase the risk of NTDs.

Survival of infants with neural tube defects in the presence of folic acid fortification

OBJECTIVE

Neural tube defects (NTDs) are preventable through preconceptional and periconceptional folic acid intake. Although decreases in the prevalence of NTDs have been reported since folic acid fortification of United States grain products began, it is not known whether folic acid plays a role in reducing the severity of occurring NTDs. Our aim was to determine whether survival among infants born with spina bifida and encephalocele has improved since folic acid fortification and to measure the effects of selected maternal, pregnancy, and birth characteristics on first-year (infant) survival rates.

METHODS

A retrospective cohort study was conducted and included 2841 infants with spina bifida and 638 infants with encephalocele who were born between 1995 and 2001 and were registered in any of 16 participating birth defects monitoring programs in the United States. First-year survival rates for both spina bifida and encephalocele cohorts were measured with Kaplan-Meier estimation; factors associated with improved chances of first-year survival, including birth before or during folic acid fortification, were measured with Cox proportional-hazards regression analysis.

RESULTS

Infants with spina bifida experienced a significantly improved first-year survival rate of 92.1% (adjusted hazard ratio: 0.68; 95% confidence interval: 0.50-0.91) during the period of mandatory folic acid fortification, compared with a 90.3% survival rate for those born before fortification. Infants with encephalocele had a statistically nonsignificant increase in survival rates, ie, 79.1% (adjusted hazard ratio: 0.76; 95% confidence interval: 0.51-1.13) with folic acid fortification, compared with 75.7% for earlier births.

CONCLUSIONS

Folic acid may play a role in reducing the severity of NTDs in addition to preventing the occurrence of NTDs. This phenomenon contributes to our understanding of the efficacy of folic acid. Additionally, as survival of NTD-affected infants improves, health care, education, and family support must expand to meet their needs.

A known functional polymorphism (Ile120Val) of the human PCMT1 gene and risk of spina bifida

Folate binding protein 1 (Folr1) knockout mice with low maternal folate concentrations have been shown to be excellent animal models for human folate-responsive neural tube defects (NTDs). Previous studies using the Folr1 knockout mice revealed that maternal folate supplementation up-regulates the expression of the PCMT1 gene in Folr1 nullizygous neural tube tissue during neural tube closure. PCMT1 encodes the protein repair enzyme l-isoaspartate (d-aspartate) O-methyltransferase (PIMT) that converts abnormal d-aspartyl and l-isoaspartyl residues to the normal l-aspartyl form. PIMT is known to protect certain neural cells from Bax-induced apoptosis. Pcmt1-deficient mice present with abnormal AdoMet/AdoHcy homeostasis. We hypothesized that a known functional polymorphism (Ile120Val) in the human PCMT1 gene is associated with an increased risk of folate-responsive human NTDs. A case-control study was conducted to investigate a possible association between this polymorphism and risk of spina bifida. Compared to the Ile/Ile and Ile/Val genotypes, the homozygous Val/Val genotype showed decreased risk for spina bifida (adjusted odds ratio=0.6, 95% confidence interval: 0.4-0.9). Our results showed that the Ile120Val polymorphism of PCMT1 gene is a genetic modifier for the risk of spina bifida. Val/Val genotype was associated with a reduction in risk for spina bifida.

Selected gene polymorphisms and their interaction with maternal smoking, as risk factors for gastroschisis

BACKGROUND

Gastroschisis is a severe birth defect in which the infant is born with a portion of the intestines extruding through a small tear in the abdominal wall, usually to the right of the umbilical cord. Its etiology is unknown, but the prevailing hypothesis is that it results from a vascular accident at the time of involution of the right umbilical vein or of the development of the superior mesenteric artery.

METHODS

In a case-control study of 57 cases of gastroschisis and 506 controls, we tested DNA for polymorphisms of 32 genes representing enzymes involved in angiogenesis, blood vessel integrity, inflammation, wound repair, and dermal or epidermal strength.

RESULTS

In logistic regression, controlling for maternal ethnicity, and using the homozygote wild-type as referent, the following gene polymorphisms were associated with an increased risk for a gastroschisis for heterozygotes: ICAM1 gly241arg (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.1 -3.4); NOS3 glu298asp (OR, 1.9; 95% CI, 1.1-3.4); NPPA 2238T > C (OR, 1.9; 95% CI, 1.0-3.4); and ADD1 gly460trp (OR, 1.5; 95% CI, 0.8-2.8). Additionally, for the NPPA and ADD1 single-nucleotide polymorphisms (SNPs), the homozygote variants had a significantly higher risk than the heterozygotes (OR, 7.5; 95% CI, 1.7-33.5 and OR, 4.9; 95% CI, 1.9-12.9, respectively). Three SNPs showed a strong interaction with maternal smoking. The risk for smokers with 1 or 2 variant alleles compared to nonsmokers with the wild-type allele were: NOS3 (OR, 5.2; 95% CI, 2.4-11.4); ICAM1 (OR, 5.2; 95% CI, 2.1-12.7); and NPPA (OR, 6.4; 95% CI, 2.8-14.6).

CONCLUSIONS

These results support the hypothesis of a vascular compromise as part of a multifactorial etiology of gastroschisis involving both genes and environmental factors.

Maternal fumonisin exposure and risk for neural tube defects: mechanisms in an in vivo mouse model

BACKGROUND

Fumonisin B1 (FB1) is a mycotoxin produced by the fungus Fusarium verticillioides, a common contaminant of corn worldwide. FB1 disrupts sphingolipid biosynthesis by inhibiting the enzyme ceramide synthase, resulting in an elevation of free sphingoid bases and depletion of downstream glycosphingolipids. A relationship between maternal ingestion of FB1-contaminated corn during early pregnancy and increased risk for neural tube defects (NTDs) has recently been proposed in human populations around the world where corn is a dietary staple. The current studies provide an in vivo mouse model of FB1 teratogenicity.

METHODS

Pregnant LM/Bc mice were injected with increasing doses of FB1 on GD 7.5 and 8.5, and exposed fetuses were examined for malformations. Sphingolipid profiles and (3)H-folate concentrations were measured in maternal and fetal tissues. Immunohistochemical expression of the GPI-anchored folate receptor (Folbp1) and its association with the lipid raft component, ganglioside GM1, were characterized. Rescue experiments were performed with maternal folate supplementation or administration of gangliosides.

RESULTS

Maternal FB1 administration (20 mg/kg of body weight) during early gestation resulted in 79% NTDs in exposed fetuses. Sphingolipid profiles were significantly altered in maternal and embryonic tissues following exposure, and (3)H-folate levels and immunohistochemical expression of Folbp1 were reduced. Maternal folate supplementation partially rescued the NTD phenotype, whereas GM1 significantly restored folate concentrations and afforded almost complete protection against FB1-induced NTDs.

CONCLUSIONS

Maternal FB1 exposure altered sphingolipid metabolism and folate concentrations in LM/Bc mice, resulting in a dose-dependent increase in NTDs that could be prevented when adequate folate levels were maintained.

Genetic variation of folate-mediated one-carbon transfer pathway predicts susceptibility to choline deficiency in humans

Choline is a required nutrient, and some humans deplete quickly when fed a low-choline diet, whereas others do not. Endogenous choline synthesis can spare some of the dietary requirement and requires one-carbon groups derived from folate metabolism. We examined whether major genetic variants of folate metabolism modify susceptibility of humans to choline deficiency. Fifty-four adult men and women were fed diets containing adequate choline and folate, followed by a diet containing almost no choline, with or without added folate, until they were clinically judged to be choline-deficient, or for up to 42 days. Criteria for clinical choline deficiency were a more than five times increase in serum creatine kinase activity or a >28% increase of liver fat after consuming the low-choline diet that resolved when choline was returned to the diet. Choline deficiency was observed in more than half of the participants, usually within less than a month. Individuals who were carriers of the very common 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele were more likely than noncarriers to develop signs of choline deficiency (odds ratio, 7.0; 95% confidence interval, 2.0-25; P < 0.01) on the low-choline diet unless they were also treated with a folic acid supplement. The effects of the C677T and A1298C polymorphisms of the 5,10-methylene tetrahydrofolate reductase gene and the A80C polymorphism of the reduced folate carrier 1 gene were not statistically significant. The most remarkable finding was the strong association in premenopausal women of the 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele polymorphism with 15 times increased susceptibility to developing organ dysfunction on a low-choline diet.

Decline in the prevalence of spina bifida and anencephaly by race/ethnicity: 1995-2002

OBJECTIVE

In an effort to reduce the occurrence of neural tube defects (NTDs), folic acid fortification of US enriched grain products was authorized by the Food and Drug Administration in March 1996 and required by January 1998. Fortification has been shown to result in an important decline in the prevalence of spina bifida and anencephaly in the general US population; however, fortification's impact on specific racial/ethnic groups has not been well described. We sought to characterize the decline in the prevalence of spina bifida and anencephaly among specific racial/ethnic groups during the transition to mandatory folic acid fortification in the United States.

METHODS

Data from 21 population-based birth defects surveillance systems were used to examine trends in prevalence of spina bifida and anencephaly for specific racial/ethnic groups for the years 1995-2002. These years were divided into 3 periods: prefortification, optional fortification, and mandatory fortification. Race/ethnicity was defined as Hispanic, non-Hispanic white, and non-Hispanic black. Prevalence ratios were calculated for each racial/ethnic group by dividing the prevalence from the mandatory fortification period by the prevalence in the prefortification period.

RESULTS

The study included data on 4468 cases of spina bifida and 2625 cases of anencephaly. The prevalence of spina bifida and anencephaly was highest among Hispanic births, followed by non-Hispanic white births, with the lowest prevalence among non-Hispanic black births. Significant declines in spina bifida and anencephaly were observed among Hispanic births and non-Hispanic white births. The prevalence ratio for non-Hispanic black births was of borderline significance for spina bifida and was not significant for anencephaly.

CONCLUSIONS

The results of this study suggest that folic acid fortification is associated with significant decreases in the prevalence of spina bifida and anencephaly among non-Hispanic white and Hispanic births. The magnitude of the reduction was similar between these 2 groups and was more pronounced for spina bifida than for anencephaly. The decline in the prevalence of spina bifida and anencephaly among non-Hispanic black births did not reach statistical significance. Efforts to increase folic acid consumption for the prevention of NTDs in pregnancies among women of all races/ethnicities should be continued, and studies to identify and elucidate other risk factors for NTDs are warranted.

Periconceptional dietary intake of myo-inositol and neural tube defects in offspring

BACKGROUND

Periconceptional intake of nutrients in addition to folic acid may contribute to neural tube defect (NTD) etiologies; a likely candidate is myo-inositol. We investigated whether maternal periconceptional dietary intake of myo-inositol influenced NTD risk.

METHODS

Data were derived from a case-control study of fetuses and infants with NTDs among 1989-1991 California births. Interviews were conducted with mothers of 454 NTD cases and with mothers of 462 nonmalformed controls. A standard 100-item food frequency questionnaire was used to assess nutrient intake.

RESULTS

We observed small increases in risk, with increases slightly more evident for anencephaly, associated with intakes of myo-inositol less than the highest intake quartile, e.g., risk of anencephaly was 1.3 (0.7-2.4) among fetuses whose mothers consumed lowest versus highest intakes of myo-inositol. These small increases, however, were imprecise, and also did not indicate increasing risk with decreasing level of myo-inositol intake. Adjusted risk estimates did not differ considerably from their unadjusted counterparts.

CONCLUSIONS

Our results do not indicate that myo-inositol intake, as measured in this study, is strongly associated with risk of human NTDs.

Folate and its preventive potential in colorectal carcinogenesis

Based on a 15-year old hypothesis, it is believed that an adequate ingestion of folate vitamins decreases, whereas a nutritional depletion of folate increases the risk of colorectal cancer. The present article reviews the efforts to provide biochemical and epidemiological evidence for folate as a chemopreventive agent against colorectal carcinogenesis. BIOLOGICAL EVIDENCE: Tetrahydrofolates govern the intracellular one-carbon metabolism and account for proper DNA biosynthesis and macromolecular modification. Numerous experimental studies traced different molecular pathways and tried to link folate depletion with DNA instability and/or mutagenesis. However, none of the proposed underlying molecular mechanisms appear clearly defined. EPIDEMIOLOGICAL EVIDENCE: Numerous case-control and prospective studies have been conducted on folate and colorectal cancer, which all together miss a clinical bottom line. The recommendation of folate intake to prevent colorectal cancer is therefore not evidence-based.

Neural tube defect rates before and after food fortification with folic acid

BACKGROUND

Since 1998, enriched cereal grains sold in the United States have been fortified with folic acid, to reduce the incidence of neural tube defects (NTDs). The Centers for Disease Control and Prevention (CDC) recently reported that NTD rates have decreased 26% since fortification, but that additional effort is needed to achieve the national goal of a 50% reduction. However, accurate determination of NTD rates requires counting antenatally detected cases; the CDC study noted that the number of prenatally diagnosed cases was likely underestimated.

METHODS AND RESULTS

We examined studies from the United States and Canada that compared rates of NTDs before and after very similar fortification programs were instituted in each country. U.S. studies had incomplete ascertainment of prenatally diagnosed NTD cases, and as a result, underreported the number of NTDs prevented. Canadian studies, in which ascertainment was more complete, showed decreases in NTD rates up to 54%.

CONCLUSIONS

There is a strong correlation between the completeness of ascertainment and the percentage decrease in NTD rates. Studies that identify cases best show that folic acid fortification is preventing around 50% of NTDs. The percentage of NTDs that are folate-preventable in the United States is uncertain, but is probably 50-60%. Thus, we may be quite close to achieving the optimum level of protection at current fortification levels.