Inhibition of MTOR signaling impairs rat embryo organogenesis by affecting folate availability.

Mechanistic target of rapamycin (MTOR) is essential for embryo development by acting as a nutrient sensor to regulate cell growth, proliferation and metabolism. Folate is required for normal embryonic development and it was recently reported that MTOR functions as a folate sensor. In this work, we tested the hypothesis that MTOR functions as a folate sensor in the embryo and its inhibition result in embryonic developmental delay affecting neural tube closure and that these effects can be rescued by folate supplementation. Administration of rapamycin (0.5 mg/kg) to rats during early organogenesis inhibited embryonic ribosomal protein S6, a downstream target of MTOR Complex1, markedly reduced embryonic folate incorporation (-84%, P < 0.01) and induced embryo developmental impairments, as shown by an increased resorption rate, reduced embryo somite number and delayed neural tube closure. These alterations were prevented by folic acid administered to the dams. Differently, although an increased rate of embryonic rotation defects was observed in the rapamycin-treated dams, this alteration was not prevented by maternal folic acid supplementation. In conclusion, MTOR inhibition during organogenesis in the rat resulted in decreased folate levels in the embryo, increased embryo resorption rate and impaired embryo development. These data suggest that MTOR signaling influences embryo folate availability, possibly by regulating the transfer of folate across the maternal-embryonic interface.

The Timing and Duration of Folate Restriction Differentially Impacts Colon Carcinogenesis.

Diet plays a crucial role in the development of colorectal cancer (CRC). Of particular importance, folate, present in foods and supplements, is a crucial modulator of CRC risk. The role of folate, and, specifically, the synthetic variant, folic acid, in the primary prevention of CRC has not been fully elucidated. Animal studies varied considerably in the timing, duration, and supplementation of folates, leading to equivocal results. Our work attempts to isolate these variables to ascertain the role of folic acid in CRC initiation, as we previously demonstrated that folate restriction conferred protection against CRC initiation in a ß-pol haploinsufficient mouse model. Here we demonstrated that prior adaptation to folate restriction altered the response to carcinogen exposure in wild-type C57BL/6 mice. Mice adapted to folate restriction for 8 weeks were protected from CRC initiation compared to mice placed on folate restriction for 1 week, irrespective of antibiotic supplementation. Through analyses of mTOR signaling, DNA methyltransferase, and DNA repair, we have identified factors that may play a critical role in the differential responses to folate restriction. Furthermore, the timing and duration of folate restriction altered these pathways differently in the absence of carcinogenic insult. These results represent novel findings, as we were able to show that, in the same model and under controlled conditions, folate restriction produced contrasting results depending on the timing and duration of the intervention.

Multi-Micronutrient Fortified Rice Improved Serum Zinc and Folate Concentrations of Cambodian School Children. A Double-Blinded Cluster-Randomized Controlled Trial.

BACKGROUND: Within Cambodia, micronutrient deficiencies continue to be prevalent in vulnerable groups, such as women and children. Fortification of staple foods such as rice could be a promising strategy for Cambodia to improve micronutrient status. OBJECTIVE: Our objective was to investigate the impact of multiple-micronutrient fortified rice (MMFR), distributed through a World Food Program school-meals program (WFP-SMP) on serum zinc concentrations and folate status in a double-blind, cluster-randomized, placebo-controlled trial. METHODS: Sixteen schools were randomly assigned to receive one of three different types of extruded-fortified rice (UltraRice Original (URO), UltraRice New (URN), or NutriRice) or unfortified rice (placebo) six days a week for six months. A total of 1950 schoolchildren (6-16 years old) participated in the study. Serum zinc (all groups) and folate (only in NutriRice and placebo group) concentrations were assessed from morning non-fasting antecubital blood samples and were measured at three time points (baseline and after three and six months). RESULTS: After six months of intervention, serum zinc concentrations were significantly increased in all fortified rice group compared to placebo and baseline (0.98, 0.85 and 1.40 µmol/L for URO, URN and NutriRice, respectively) (interaction effect: p < 0.001 for all). Children in the intervention groups had a risk of zinc deficiencies of around one third (0.35, 039, and 0.28 for URO, URN, and NutriRice, respectively) compared to the placebo (p < 0.001 for all). The children receiving NutriRice had higher serum folate concentrations at endline compared to children receiving normal rice (+ 2.25 ng/mL, p = 0.007). CONCLUSIONS: This study showed that the high prevalence of zinc and folate deficiency in Cambodia can be improved through the provision of MMFR. As rice is the staple diet for Cambodia, MMFR should be considered to be included in the school meal program and possibilities should be explored to introduce MMFR to the general population.

Low Prevalence of Folic Acid Supplementation during Pregnancy: A Multicenter Study in Vietnam.

Periconceptional folic acid (FA) supplementation is recommended to prevent neural tube defects (NTDs), but little information is known about its use in Vietnam. It is important that FA supplements start to be taken when planning a pregnancy and continued through the first trimester to prevent NTDs, as the neural tube closes in the first month of pregnancy. However, FA supplementation in Vietnam is usually recommended to commence from the first antenatal visit, which is usually at 16 weeks, and very few women take FA before their first visit. This multicenter study aimed to determine the prevalence of FA supplement use and associated maternal characteristics in Vietnam. FA supplementation was assessed in 2030 singleton pregnant women between 2015 and 2016. In total, 654 (32.2%) women reported taking either supplements containing FA alone or multivitamins containing FA, and 505 (24.9%) reported correctly taking supplements containing FA alone. Women who were aged 30 years or over, had low education levels, had formal employment, and whose current pregnancy was first or unplanned were less likely to supplement with FA. Education programs are needed to encourage FA supplementation when contemplating pregnancy.

Renal Reabsorption of Folates: Pharmacological and Toxicological Snapshots.

Folates are water-soluble B9 vitamins that serve as one-carbon donors in the de novo synthesis of thymidylate and purines, and in the conversion of homocysteine to methionine. Due to their key roles in nucleic acid synthesis and in DNA methylation, inhibiting the folate pathway is still one of the most efficient approaches for the treatment of several tumors. Methotrexate and pemetrexed are the most prescribed antifolates and are mainly used in the treatment of acute myeloid leukemia, osteosarcoma, and lung cancers. Normal levels of folates in the blood are maintained not only by proper dietary intake and intestinal absorption, but also by an efficient renal reabsorption that seems to be primarily mediated by the glycosylphosphatidylinositol- (GPI) anchored protein folate receptor α (FRα), which is highly expressed at the brush-border membrane of proximal tubule cells. Folate deficiency due to malnutrition, impaired intestinal absorption or increased urinary elimination is associated with severe hematological and neurological deficits. This review describes the role of the kidneys in folate homeostasis, the molecular basis of folate handling by the kidneys, and the use of high dose folic acid as a model of acute kidney injury. Finally, we provide an overview on the development of folate-based compounds and their possible therapeutic potential and toxicological ramifications.

A case-control analysis of maternal diet and risk of neural tube defects in Bangladesh.

OBJECTIVES: Mothers need a nutrient-rich diet for healthy neural tube development. Neural tube defect risk can be reduced through fortifying grain products with folic acid and taking folic acid supplements. Fortification is not required in Bangladesh. Maternal supplement use rates are low, similar to other countries. This study evaluates maternal dietary intake during pregnancy to identify possible interventions. METHODS: A food frequency questionnaire (FFQ) assessed maternal diet. The primary aim compared dietary intake (calories, fat, carbohydrate, protein, fiber, vitamins, and minerals) between mothers of infants with myelomeningocele (cases) and mothers of controls. Secondary aims included (i) comparing foods consumed and (ii) evaluating if rice intake correlated with arsenic exposure. Paired t-tests, Wilcoxon signed rank tests, McNemar's chi-squared test, and linear regression were used. RESULTS: This study included 110 matched mother-infant pairs (55 cases/55 controls). Mothers of cases and mothers of controls had similar caloric intake [median 2406 kcal/day vs. 2196 kcal/day (p = 0.071)]. Mothers in both groups consumed less than half the daily recommended 600 µg of folate. Diets were potentially deficient in vitamins A, D, E, potassium, sodium, and iron. Steamed rice was the primary food consumed for both groups, and this rice intake was not associated with toenail arsenic. CONCLUSIONS: Dietary interventions should increase folate, vitamins A, D, E, potassium, sodium, and iron intake in Bangladeshi mothers. Folic acid fortification of grain products maybe the only viable strategy to achieve adequate folate intake for mothers. Given the central role of rice to the Bangladeshi diet, fortifying rice may be a viable option.

The effect of folic acid deficiency on FGF pathway via Brachyury regulation in neural tube defects.

Folate deficiency in early development leads to disturbance in multiple processes, including neurogenesis during which fibroblast growth factor (FGF) pathway is one of the crucial pathways. Whether folic acid (FA) directly affects FGF pathways to influence neurodevelopment and the possible mechanism remains unclear. In this study, we presented evidence that in human FA-insufficient encephalocele, the FGF pathway was interfered. Furthermore, in Brachyury knockout mice devoid of such T-box transcription factors regulating embryonic neuromesodermal bipotency and a key component of FGF pathway, change in expression of Brachyury downstream targets, activator Fgf8 and suppressor dual specificity phosphatase 6 was detected, along with the reduction in expression of other key FGF pathway genes. By using a FA-deficient cell model, we further demonstrated that decrease in Brachyury expression was through alteration in hypermethylation at the Brachyury promoter region under FA deficiency conditions, and suppression of Brachyury promoted the inactivation of the FGF pathway. Correspondingly, FA supplementation partially reverses the effects seen in FA-deficient embryoid bodies. Lastly, in mice with maternal folate-deficient diets, aberrant FGF pathway activity was found in fetal brain dysplasia. Taken together, our findings highlight the effect of FA on FGF pathways during neurogenesis, and the mechanism may be due to the low expression of Brachyury gene via hypermethylation under FA-insufficient conditions.-Chang, S., Lu, X., Wang, S., Wang, Z., Huo, J., Huang, J., Shangguan, S., Li, S., Zou, J., Bao, Y., Guo, J., Wang, F., Niu, B., Zhang, T., Qiu, Z., Wu, J., Wang, L. The effect of folic acid deficiency on FGF pathway via Brachyury regulation in neural tube defects.

Optic Nerve Degeneration and Reduced Contrast Sensitivity Due to Folic Acid Deficiency: A Behavioral and Electrophysiological Study in Rhesus Monkeys.

Purpose: The purpose of the research was to elucidate the role of folic acid (B9) deficiency in the development of nutritional optic neuritis and to characterize the neurophysiological consequences of optic nerve degeneration in the cortical visual system. Methods: A combined behavioral and electrophysiological approach was applied to study luminance contrast sensitivity in two macaque monkeys affected by nutritional optic neuritis and in two healthy monkeys for comparison. For one monkey, a follow-up approach was applied to compare visual performance before onset of optic neuropathy, during the disease, and after treatment. Results: Optic nerve degeneration developed as a consequence of insufficient dietary intake of folic acid in two exemplars of macaque monkeys. The degeneration resulted in markedly reduced luminance contrast sensitivity as assessed behaviorally. In one monkey, we also measured visual activity in response to varying contrast at the level of single neurons in the cortical visual system and found a striking reduction in contrast sensitivity, as well as a marked increase in the latency of neuronal responses. Prolonged daily folate supplementation resulted in a significant recovery of function. Conclusions: Folic acid deficiency per se can lead to the development of optic nerve degeneration in otherwise healthy adult animals. The optic nerve degeneration strongly affects contrast sensitivity and leads to a distinct reduction in the strength and velocity of the incoming signal to cortical visual areas of the macaque brain, without directly affecting excitability and functional properties of cortical neurons.

One crisis, diverse impacts-Tissue-specificity of folate deficiency-induced circulation defects in zebrafish larvae.

Folate (vitamin B9) is an essential nutrient required for cell survival, proliferation, differentiation and therefore embryogenesis. Folate deficiency has been associated with many diseases, including congenital heart diseases and megaloblastic anemia, yet the mechanisms underlying these remains elusive. Here, we examine the impact of folate deficiency on the development of the circulation system using a zebrafish transgenic line which displays inducible folate deficiency. Impaired hematopoiesis includes decreased hemoglobin levels, decreased erythrocyte number, increased erythrocyte size and aberrant c-myb expression pattern were observed in folate deficient embryos. Cardiac defects, including smaller chamber size, aberrant cardiac function and cmlc2 expression pattern, were also apparent in folate deficient embryos. Characterization of intracellular folate content in folate deficiency revealed a differential fluctuation among the different folate derivatives that carry a single carbon group at different oxidation levels. Rescue attempts by folic acid and nucleotides resulted in differential responses among affected tissues, suggesting that different pathomechanisms are involved in folate deficiency-induced anomalies in a tissue-specific manner. The results of the current study provide an explanation for the inconsistent outcome observed clinically in patients suffering from folate deficiency and/or receiving folate supplementation. This study also supports the use of this model for further research on the defective cardiogenesis and hematopoiesis caused by folate deficiency.

Micronutrient Status and Dietary Intake of Iron, Vitamin A, Iodine, Folate and Zinc in Women of Reproductive Age and Pregnant Women in Ethiopia, Kenya, Nigeria and South Africa: A Systematic Review of Data from 2005 to 2015.

A systematic review was conducted to evaluate the status and intake of iron, vitamin A, iodine, folate and zinc in women of reproductive age (WRA) (≥15-49 years) and pregnant women (PW) in Ethiopia, Kenya, Nigeria and South Africa. National and subnational data published between 2005 and 2015 were searched via Medline, Scopus and national public health websites. Per micronutrient, relevant data were pooled into an average prevalence of deficiency, weighted by sample size (WAVG). Inadequate intakes were estimated from mean (SD) intakes. This review included 65 surveys and studies from Ethiopia (21), Kenya (11), Nigeria (21) and South Africa (12). In WRA, WAVG prevalence of anaemia ranged from 18-51%, iron deficiency 9-18%, and iron deficiency anaemia at 10%. In PW, the prevalence was higher, and ranged from 32-62%, 19-61%, and 9-47%, respectively. In WRA, prevalence of vitamin A, iodine, zinc and folate deficiencies ranged from 4-22%, 22-55%, 34% and 46%, while in PW these ranged from 21-48%, 87%, 46-76% and 3-12% respectively. Inadequate intakes of these micronutrients are high and corresponded with the prevalence figures. Our findings indicate that nationally representative data are needed to guide the development of nutrition interventions and public health programs, such as dietary diversification, micronutrient fortification and supplementation.

Genetic polymorphisms and folate status.

Moderate hyperhomocysteinemia-induced low folate status is an independent risk factor for cardiovascular disease, dementia, and depression. Folate is an essential cofactor in the one-carbon metabolism pathway and is necessary in amino acid metabolism, purine and thymidylate synthesis, and DNA methylation. In the folate cycle and homocysteine metabolism, folate, vitamin B12, vitamin B6, and vitamin B2 are important cofactors. Many enzymes are involved in folate transport and uptake, the folate pathway, and homocysteine (Hcy) metabolism, and various polymorphisms have been documented in these enzymes. Serum folate and total Hcy (tHcy) levels are influenced by folate intake and genetic polymorphisms in 5,10-methylenetertahydrofolate reductase (MTHFR) such as C677T. The prevalence of the MTHFR 677TT genotype varies across ethnic groups and regions, with a frequency of approximately 15% in Japanese populations. Individuals with the TT genotype have significantly higher tHcy levels and lower folate levels in serum than those with the CT and TT genotypes. However, administration of folic acid has been shown to eliminate these differences. Moreover, data have suggested that interventions based on genotype may be effective for motivating individuals to change their lifestyle and improve their nutrition status. Accordingly, in this review, we discuss the effects of MTHFR C677T polymorphisms on serum tHcy and folate levels with folic acid intervention and evaluate approaches for overcoming folic acid deficiency and related symptoms.

Intergenerational impact of paternal lifetime exposures to both folic acid deficiency and supplementation on reproductive outcomes and imprinted gene methylation.

STUDY QUESTION: Do paternal exposures to folic acid deficient (FD), and/or folic acid supplemented (FS) diets, throughout germ cell development adversely affect male germ cells and consequently offspring health outcomes? SUMMARY ANSWER: Male mice exposed over their lifetimes to both FD and FS diets showed decreased sperm counts and altered imprinted gene methylation with evidence of transmission of adverse effects to the offspring, including increased postnatal-preweaning mortality and variability in imprinted gene methylation. WHAT IS KNOWN ALREADY: There is increasing evidence that disruptions in male germ cell epigenetic reprogramming are associated with offspring abnormalities and intergenerational disease. The fetal period is the critical time of DNA methylation pattern acquisition for developing male germ cells and an adequate supply of methyl donors is required. In addition, DNA methylation patterns continue to be remodeled during postnatal spermatogenesis. Previous studies have shown that lifetime (prenatal and postnatal) folic acid deficiency can alter the sperm epigenome and increase the incidence of fetal morphological abnormalities. STUDY DESIGN, SIZE, DURATION: Female BALB/c mice (F0) were placed on one of four amino-acid defined diets for 4 weeks before pregnancy and throughout pregnancy and lactation: folic acid control (Ctrl; 2 mg/kg), 7-fold folic acid deficient (7FD; 0.3 mg/kg), 10-fold high FS (10FS, 20 mg/kg) or 20-fold high FS (20FS, 40 mg/kg) diets. F1 males were weaned to their respective prenatal diets to allow for diet exposure during all windows of germline epigenetic reprogramming: the erasure, re-establishment and maintenance phases. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: F0 females were mated with chow-fed males to produce F1 litters whose germ cells were exposed to the diets throughout embryonic development. F1 males were subsequently mated with chow-fed female mice. Two F2 litters, unexposed to the experimental diets, were generated from each F1 male; one litter was collected at embryonic day (E)18.5 and one delivered and followed postnatally. DNA methylation at a global level and at the differentially methylated regions of imprinted genes (H19, Imprinted Maternally Expressed Transcript (Non-Protein Coding)-H19, Small Nuclear Ribonucleoprotein Polypeptide N-Snrpn, KCNQ1 Opposite Strand/Antisense Transcript 1 (Non-Protein Coding)-Kcnq1ot1, Paternally Expressed Gene 1-Peg1 and Paternally Expressed Gene 3-Peg3) was assessed by luminometric methylation analysis and bisulfite pyrosequencing, respectively, in F1 sperm, F2 E18.5 placenta and F2 E18.5 brain cortex. MAIN RESULTS AND THE ROLE OF CHANCE: F1 males exhibited lower sperm counts following lifetime exposure to both folic acid deficiency and the highest dose of folic acid supplementation (20FS), (both P < 0.05). Post-implantation losses were increased amongst F2 E18.5 day litters from 20FS exposed F1 males (P < 0.05). F2 litters derived from both 7FD and 20FS exposed F1 males had significantly higher postnatal-preweaning pup death (both P < 0.05). Sperm from 10FS exposed males had increased variance in methylation across imprinted gene H19, P < 0.05; increased variance at a few sites within H19 was also found for the 7FD and 20FS groups (P < 0.05). While the 20FS diet resulted in inter-individual alterations in methylation across the imprinted genes Snrpn and Peg3 in F2 E18.5 placenta, ≥50% of individual sites tested in Peg1 and/or Peg3 were affected in the 7FD and 10FS groups. Inter-individual alterations in Peg1 methylation were found in F2 E18.5 day 10FS group brain cortex (P < 0.05). LARGE SCALE DATA: Not applicable. LIMITATIONS REASONS FOR CAUTION: The cause of the increase in postnatal-preweaning mortality was not investigated post-mortem. Further studies are required to understand the mechanisms underlying the adverse effects of folic acid deficiency and supplementation on developing male germ cells. Genome-wide DNA and histone methylome studies as well as gene expression studies are required to better understand the links between folic acid exposures, an altered germ cell epigenome and offspring outcomes. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this study provide further support for paternally transmitted environmental effects. The results indicate that both folic acid deficiency and high dose supplementation can be detrimental to germ cell development and reproductive fitness, in part by altering DNA methylation in sperm. STUDY FUNDING AND COMPETING INTERESTS: This study was supported by a grant to J.M.T. from the Canadian Institutes of Health Research (CIHR #89944). The authors declare they have no conflicts of interest.

Neural tube defects: Risk factors and preventive measures.

For the last 25 years, it has been proven that the occurrence or recurrence of neural tube defects can be prevented with the administration of folic acid before and early pregnancy. At present, over 80 countries in the world, except Japan, have mandated the fortification of wheat flour and/or rice with folic acid, which has resulted in a significant reduction in the prevalence of neural tube defects. In 2000, the Japanese government recommended folic acid 400 µg daily for young women of childbearing age and women who are planning to conceive. In 2002, the government started to present information about the importance of folic acid in the development of fetuses in the Mother-Child Health Booklet annually. Despite these endeavors, the prevalence of neural tube defects has remained unchanged. We discuss the risk factors of neural tube defects and propose preventive measures to decrease the number of neonates with neural tube defects. We believe that the government should implement the fortification of staple food with folic acid very soon, which will eventually decrease not only the neonatal mortality and morbidity, but also the economic burden on our health care system.

Nutrition, One-Carbon Metabolism and Neural Tube Defects: A Review.

Neural tube defects (NTDs) are a group of severe congenital malformations, induced by the combined effects of genes and the environment. The most valuable finding so far has been the protective effect of folic acid supplementation against NTDs. However, many women do not take folic acid supplements until they are pregnant, which is too late to prevent NTDs effectively. Long-term intake of folic acid-fortified food is a good choice to solve this problem, and mandatory folic acid fortification should be further promoted, especially in Europe, Asia and Africa. Vitamin B2, vitamin B-6, vitamin B-12, choline, betaine and n-3 polyunsaturated fatty acids (PUFAs) can also reduce the NTD risk by interacting with the one-carbon metabolism pathway. This suggest that multivitamin B combined with choline, betaine and n-3 PUFAs supplementation may have a better protective effect against NTDs than folic acid alone. Genetic polymorphisms involved in one-carbon metabolism are associated with NTD risk, and gene screening for women of childbearing age prior to pregnancy may help prevent NTDs induced by the risk allele. In addition, the consumption of alcohol, tea and coffee, and low intakes of fruit and vegetable are also associated with the increased risk of NTDs, and should be avoided by women of childbearing age.

Folic acid and autism: What do we know?

Autism spectrum disorders (ASD) consist in a range of neurodevelopmental conditions that share common features with autism, such as impairments in communication and social interaction, repetitive behaviors, stereotypies, and a limited repertoire of interests and activities. Some studies have reported that folic acid supplementation could be associated with a higher incidence of autism, and therefore, we aimed to conduct a systematic review of studies involving relationships between this molecule and ASD. The MEDLINE database was searched for studies written in English which evaluated the relationship between autism and folate. The initial search yielded 60 potentially relevant articles, of which 11 met the inclusion criteria. The agreement between reviewers was κ = 0.808. The articles included in the present study addressed topics related to the prescription of vitamins, the association between folic acid intake/supplementation during pregnancy and the incidence of autism, food intake, and/or nutrient supplementation in children/adolescents with autism, the evaluation of serum nutrient levels, and nutritional interventions targeting ASD. Regarding our main issue, namely the effect of folic acid supplementation, especially in pregnancy, the few and contradictory studies present inconsistent conclusions. Epidemiological associations are not reproduced in most of the other types of studies. Although some studies have reported lower folate levels in patients with ASD, the effects of folate-enhancing interventions on the clinical symptoms have yet to be confirmed.

Blood folate concentrations among women of childbearing age by race/ethnicity and acculturation, NHANES 2001-2010.

Hispanic women have higher rates of neural tube defects and report lower total folic acid intakes than non-Hispanic white (NHW) women. Total folic acid intake, which is associated with neural tube defect risk reduction, has been found to vary by acculturation factors (i.e. language preference, country of origin, or time spent in the United States) among Hispanic women. It is unknown whether this same association is present for blood folate status. The objective of this research was to assess the differences in serum and red blood cell (RBC) folate concentrations between NHW women and Mexican American (MA) women and among MA women by acculturation factors. Cross-sectional data from the 2001-2010 National Health and Nutrition Examination Survey (NHANES) were used to investigate how blood folate concentrations differ among NHW or MA women of childbearing age. The impact of folic acid supplement use on blood folate concentrations was also examined. MA women with lower acculturation factors had lower serum and RBC folate concentrations compared with NHW women and to their more acculturated MA counterparts. Consuming a folic acid supplement can minimize these disparities, but MA women, especially lower acculturated MA women, were less likely to report using supplements. Public health efforts to increase blood folate concentrations among MA women should consider acculturation factors when identifying appropriate interventions.

Dihydrofolate reductase 19-bp deletion polymorphism modifies the association of folate status with memory in a cross-sectional multi-ethnic study of adults.

BACKGROUND: Folate status has been positively associated with cognitive function in many studies; however, some studies have observed associations of poor cognitive outcomes with high folate. In search of an explanation, we hypothesized that the association of folate with cognition would be modified by the interaction of high-folate status with a common 19-bp deletion polymorphism in the dihydrofolate reductase (DHFR) gene. To our knowledge, the cognitive effects of this gene have not been studied previously. OBJECTIVE: We examined the association between cognitive outcomes with the 19-bp deletion DHFR polymorphism, folate status, and their interaction with high or normal plasma folate. DESIGN: This was a pooled cross-sectional study of the following 2 Boston-based cohorts of community living adults: the Boston Puerto Rican Health Study and the Nutrition, Aging, and Memory in Elders study. Individuals were genotyped for the DHFR 19-bp deletion genotype, and plasma folate status was determined. Cognitive outcomes included the Mini-Mental State Examination, Center for Epidemiologic Studies Depression Scale, and factor scores for the domains of memory, executive function, and attention from a set of cognitive tests. RESULTS: The prevalence of the homozygous deletion (del/del) genotype was 23%. In a multivariable analysis, high folate status (>17.8 ng/mL) was associated with better memory scores than was normal-folate status (fourth-fifth quintiles compared with first-third quintiles: ß ± SE = -0.22 ± 0.06, P < 0.01). Carriers of the DHFR del/del genotype had worse memory scores (ß ± SE = -0.24 ± 0.10, P < 0.05) and worse executive scores (ß = -0.19, P < 0.05) than did those with the del/ins and ins/ins genotypes. Finally, we observed an interaction such that carriers of the del/del genotype with high folate had significantly worse memory scores than those of both noncarriers with high-folate and del/del carriers with normal-folate (ß-interaction = 0.26 ± 0.13, P < 0.05). CONCLUSIONS: This study identifies a putative gene-nutrient interaction that, if confirmed, would predict that a sizable minority carrying the del/del genotype might not benefit from high-folate status and could see a worsening of memory. An understanding of how genetic variation affects responses to high-folate exposure will help weigh risks and benefits of folate supplementation for individuals and public health.

Folic acid deficiency induces premature hearing loss through mechanisms involving cochlear oxidative stress and impairment of homocysteine metabolism.

Nutritional imbalance is emerging as a causative factor of hearing loss. Epidemiologic studies have linked hearing loss to elevated plasma total homocysteine (tHcy) and folate deficiency, and have shown that folate supplementation lowers tHcy levels potentially ameliorating age-related hearing loss. The purpose of this study was to address the impact of folate deficiency on hearing loss and to examine the underlying mechanisms. For this purpose, 2-mo-old C57BL/6J mice (Animalia Chordata Mus musculus) were randomly divided into 2 groups (n = 65 each) that were fed folate-deficient (FD) or standard diets for 8 wk. HPLC analysis demonstrated a 7-fold decline in serum folate and a 3-fold increase in tHcy levels. FD mice exhibited severe hearing loss measured by auditory brainstem recordings and TUNEL-positive-apoptotic cochlear cells. RT-quantitative PCR and Western blotting showed reduced levels of enzymes catalyzing homocysteine (Hcy) production and recycling, together with a 30% increase in protein homocysteinylation. Redox stress was demonstrated by decreased expression of catalase, glutathione peroxidase 4, and glutathione synthetase genes, increased levels of manganese superoxide dismutase, and NADPH oxidase-complex adaptor cytochrome b-245, α-polypeptide (p22phox) proteins, and elevated concentrations of glutathione species. Altogether, our findings demonstrate, for the first time, that the relationship between hyperhomocysteinemia induced by folate deficiency and premature hearing loss involves impairment of cochlear Hcy metabolism and associated oxidative stress.

Folate deficiency in rat pups during weaning causes learning and memory deficits.

Folate is essential for fetal development, and its deficiency during gestation causes behavioural deficits in the offspring. The present study investigated its influence during weaning on brain function in the pups of rats that were put on a folate-deficient (FD) diet on postnatal day (PND) 1. Systemic folate deficiency in pups on the FD diet (n 15) was evident from the dramatically lower hepatic folate concentrations (median 23·7, range 8·1-48·4 ng/mg protein) and higher homocysteine concentrations (median 27·7, range 14·7-45·5 pmol/mg protein), respectively, compared with those of pups on the normal diet (ND; n 9) (median 114·5, range 64·5-158·5 ng/mg protein and median 15·5, range 11·6-18·9 pmol/mg protein) on PND 23. Brain folate concentrations although low were similar in pups on the FD diet (median 10·5, range 5·5-24·5 ng/mg protein) and ND (median 11·1, range 7·1-24·2 ng/mg protein). There was a high accumulation of homocysteine in the brain of FD pups, mostly in the hippocampus (median 58·1, range 40·8-99·7 pmol/mg protein) and cerebellum (median 69·1, range 50·8-126·6 pmol/mg protein), indicating metabolic folate deficiency despite normal brain folate concentrations. Developmental deficits or autistic traits were more frequent in the FD group than in the ND group and repetitive self-grooming occurred, on average, three times (range 1-8) v. once (range 0-3) during 5 min, respectively. Long-term memory or spatial learning and set-shifting deficits affected 12 to 62% of rats in the FD group compared with none in the ND group. Post-weaning folic acid supplementation did not correct these deficits. These observations indicate that folate deficiency during weaning affects postnatal development even when gestational folate supply is normal.

Consortium analysis of gene and gene-folate interactions in purine and pyrimidine metabolism pathways with ovarian carcinoma risk.

SCOPE: We reevaluated previously reported associations between variants in pathways of one-carbon (1-C) (folate) transfer genes and ovarian carcinoma (OC) risk, and in related pathways of purine and pyrimidine metabolism, and assessed interactions with folate intake. METHODS AND RESULTS: Odds ratios (OR) for 446 genetic variants were estimated among 13,410 OC cases and 22,635 controls, and among 2281 cases and 3444 controls with folate information. Following multiple testing correction, the most significant main effect associations were for dihydropyrimidine dehydrogenase (DPYD) variants rs11587873 (OR = 0.92; p = 6 × 10⁻5) and rs828054 (OR = 1.06; p = 1 × 10⁻4). Thirteen variants in the pyrimidine metabolism genes, DPYD, DPYS, PPAT, and TYMS, also interacted significantly with folate in a multivariant analysis (corrected p = 9.9 × 10⁻6) but collectively explained only 0.2% of OC risk. Although no other associations were significant after multiple testing correction, variants in SHMT1 in 1-C transfer, previously reported with OC, suggested lower risk at higher folate (p(interaction) = 0.03-0.006). CONCLUSION: Variation in pyrimidine metabolism genes, particularly DPYD, which was previously reported to be associated with OC, may influence risk; however, stratification by folate intake is unlikely to modify disease risk appreciably in these women. SHMT1 SNP-by-folate interactions are plausible but require further validation. Polymorphisms in selected genes in purine metabolism were not associated with OC.