Folate and DNA methylation during in utero development and aging

The intervention on aging system: A classification model, the requirement for five novel categories

Aging is widely considered an immovable fact of life. Cultural conditioning has ensured that therapeutics for extreme human lifespans are considered out of reach technologies. However, longevity therapies such as stem cell replacement, fasting, gene therapies, fasting mimetics such as metformin and rapamycin, regulation and tissue reprogramming with OSK transcription factors, blood dilution, metabolic pathway engineering, reversal of epigenetic drift, heterochronic parabiosis, coenzyme replacement technologies (nicotinamide adenine dinucleotide) and a plethora of other established sciences are showing great potential at slowing down the rate at which tissues enter dysfunction. Recent discoveries have shed light on major mysteries of the aging process. Longevity‐based discoveries are not only landing quickly, but therapies to prevent or reverse those drivers of aging are also being devised regularly and this is opening up an entirely new industry, the longevity industry. This presents the requirement for a new classification system where subjects can be divided into specific groups based on their potential for mortality. This system also enables the public to target which class of this classification system they wish to be on. Moving the population on the classification system to become more disease resistant holds great benefit for society and governments as a whole.

The Ability of Nutrition to Mitigate Epigenetic Drift: A Novel Look at Regulating Gene Expression

Epigenetic drift causes modification in gene expression during aging and a myriad of physiological changes that are mostly undesirable, remove youthful phenotype and are related to biological decay and disease onset. The epigenome is considered a stable regulator of genetic expression. Moreover, evidence is now accumulating that commonly available compounds found in foods can influence the epigenome to embrace a more youthful and therefore, more disease resistant state. Here we explore the correlation between nutriment and the epigenetic regulation through various types of alimentation. The aim is not to discuss specific chemicals involved in disease onset. Instead, we offer a brief glance at pathogens and offer a practical pathway into epigenetic regulation, hypothesizing that epigenetic drift might be attenuated by several foods able to drive a more youthful and disease resistant phenotype.

PM2.5-induced extensive DNA methylation changes in the heart of zebrafish embryos and the protective effect of folic acid

We previously found that folic acid (FA) attenuated cardiac defects in zebrafish embryos exposed to extractable organic matter (EOM) from PM2.5, but the underlining mechanisms remain to be elucidated. Since DNA methylation is crucial to cardiac development, we hypothesized that EOM-induced aberrant DNA methylation changes could be diminished by FA supplementation. In this study, zebrafish embryos were exposed to EOM in the absence or presence of FA. Genomic-wide DNA methylation analysis identified both DNA hypo- and hyper-methylation changes in CCGG sites in zebrafish embryos exposed to EOM, which were attenuated by FA supplementation. We identified a total of 316 genes with extensive DNA methylation changes in EOM samples but little or no DNA methylation changes in EOM plus FA samples. The genes were involved in critical cellular processes and signaling pathways important for embryo development. In addition, the EOM-decreased SAM/SAH ratio was counteracted by FA supplementation. Furthermore, FA attenuated the EOM-induced changes in the expression of genes involved in the regulation of DNA methylation and in folate biosynthesis. In conclusion, our data suggest that FA supplementation protected zebrafish embryos from the cardiac developmental toxicity of PM2.5 by alleviating EOM-induced DNA methylation changes.

Transcriptomic analysis of differentially expressed genes in the oviduct of Rhacophorus omeimontis provides insights into foam nest construction

BACKGROUND

The production of foam nests is one of the strategies that has evolved to allow some anuran species to protect their eggs and larvae. Despite considerable knowledge of the biochemical components of and construction behavior leading to anuran foam nests, little is known about the molecular basis of foam nest construction. Rhacophorus omeimontis presents an arboreal foam-nesting strategy during the breeding season. To better understand the molecular mechanism of foam nest production, transcriptome sequencing was performed using the oviduct of female R. omeimontis during the period when foam nest production began and the period when foam nest production was finished.

RESULTS

The transcriptomes of six oviduct samples of R. omeimontis were obtained using Illumina sequencing. A total of 84,917 unigenes were obtained, and 433 genes (270 upregulated and 163 downregulated) were differentially expressed between the two periods. These differentially expressed genes (DEGs) were mainly enriched in extracellular space and extracellular region based on Gene Ontology (GO) enrichment analysis and in the pathways of two-component system, cell adhesion molecules, steroid hormone biosynthesis and neuroactive ligand-receptor interaction based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Specifically, genes encoding lectins, surfactant proteins and immunity components were highly expressed when the foam nest construction began, indicating that the constituents of foam nests in R. omeimontis were likely a mixture of surfactant, lectins and immune defense proteins. During the period when foam nest production was finished, genes related to lipid metabolism, steroid hormone and immune defense were highly expressed, indicating their important roles in regulating the process of foam nesting.

CONCLUSIONS

Our study provides a rich list of potential genes involved in the production of foam nests in R. omeimontis. These results provide insights into the molecular mechanisms underlying the process of foam nest construction and will facilitate further studies of R. omeimontis.

DNA methylome of human neonatal umbilical cord: Enrichment of differentially methylated regions compared to umbilical cord blood DNA at transcription factor genes involved in body patterning and effects of maternal folate deficiency or children's sex

The DOHaD (developmental origins of health and disease) hypothesis claims that fetal malnutrition or exposure to environmental pollutants may affect their lifelong health. Epigenetic changes may play significant roles in DOHaD; however, access to human fetuses for research has ethical and technical hurdles. Umbilical cord blood (CB) has been commonly used as an epigenetic surrogate of fetuses, but it does not provide direct evidence of fetal exposure to pollutants. Here, we propose umbilical cord tissue (UC), which accumulates substances delivered to fetuses during gestation, as an alternative surrogate for epigenetic studies on fetuses. To explore the feasibility to examine UC epigenome by deep sequencing, we determined CpG methylation profiles of human postnatal UC by reduced representation bisulfite sequencing. Principal component analysis clearly separated the DNA methylomes of UC and CB pairs isolated from the same newborn (n = 10). Although all UC chromosomes were modestly hypomethylated compared to CB chromosomes, GO analysis revealed strong enrichment of differentially methylated regions (DMRs) at promoter-associated CpG islands in the HOX gene clusters and other genes encoding transcription factors involved in determination of the body pattern. DNA methylomes of UC autosomes were largely comparable between males and females. Deficiency of folate during pregnancy has been suggested to affect fetal DNA methylation to cause congenital anomalies. Whereas DNA methylome of UC was not significantly affected by early-gestational (12 weeks) low levels of maternal plasma folate (< 8 ng/ml, n = 10) compared to controls (>19 ng/mL, n = 10), two specific loci of LTR12C endogenous retroviruses in chromosome 12 were significantly hypermethylated in the low-folate group. Our study suggests that UC is useful as an alternative surrogate for studying environmental effects on DNA methylation in human fetuses, compensating CB by providing additional information about epigenetic regulation of genes involved in developmental body patterning and endogenous retroviruses.

Epigenetic Mechanisms Link Maternal Diets and Gut Microbiome to Obesity in the Offspring

Nutrition is the most important environmental factor that can influence early developmental processes through regulation of epigenetic mechanisms during pregnancy and neonatal periods. Maternal diets or nutritional compositions contribute to the establishment of the epigenetic profiles in the fetus that have a profound impact on individual susceptibility to certain diseases or disorders in the offspring later in life. Obesity is considered a global epidemic that impairs human life quality and also increases risk of development of many human diseases such as diabetes and cardiovascular diseases. Studies have shown that maternal nutrition status is closely associated with obesity in progenies indicating obesity has a developmental origin. Maternal diets may also impact the early establishment of the fetal and neonatal microbiome leading to specific epigenetic signatures that may potentially predispose to the development of late-life obesity. This article will review the association of different maternal dietary statuses including essential nutritional quantity and specific dietary components with gut microbiome in determining epigenetic impacts on offspring susceptibility to obesity.

Longitudinal association between fasting blood glucose concentrations and first stroke in hypertensive adults in China: effect of folic acid intervention

Background: Diabetes is a known risk factor for stroke, but data on its prospective association with first stroke are limited. Folic acid supplementation has been shown to protect against first stroke, but its role in preventing first stroke in diabetes is unknown.Objectives: This post hoc analysis of the China Stroke Primary Prevention Trial tested the hypotheses that the fasting blood glucose (FBG) concentration is positively associated with first stroke risk and that folic acid treatment can reduce stroke risk associated with elevated fasting glucose concentrations.Design: This analysis included 20,327 hypertensive adults without a history of stroke or myocardial infarction, who were randomly assigned to a double-blind daily treatment with 10 mg enalapril and 0.8 mg folic acid (n = 10,160) or 10 mg enalapril alone (n = 10,167). Kaplan-Meier survival analysis and Cox proportionate hazard models were used to test the hypotheses with adjustment for pertinent covariables.Results: During a median treatment duration of 4.5 y, 616 participants developed a first stroke (497 ischemic strokes). A high FBG concentration (≥7.0 mmol/L) or diabetes, compared with a low FBG concentration (<5.0 mmol/L), was associated with an increased risk of first stroke (6.0% compared with 2.6%, respectively; HR: 1.9; 95% CI: 1.3, 2.8; P < 0.001). Folic acid treatment reduced the risk of stroke across a wide range of FBG concentrations ≥5.0 mmol/L, but risk reduction was greatest in subjects with FBG concentrations ≥7.0 mmol/L or with diabetes (HR: 0.66; 95% CI: 0.46, 0.97; P < 0.05). There was a significant interactive effect of FBG and folic acid treatment on first stroke (P = 0.01).Conclusions: In Chinese hypertensive adults, an FBG concentration ≥7.0 mmol/L or diabetes is associated with an increased risk of first stroke; this increased risk is reduced by 34% with folic acid treatment. These findings warrant additional investigation. This trial was registered at clinicaltrials.gov as NCT00794885.

Epigenetic dysfunctional diseases and therapy for infection and inflammation

Even though the discovery of the term 'epigenetics' was in the 1940s, it has recently become one of the most promising and expanding fields to unravel the gene expression pattern in several diseases. The most well studied example is cancer, but other diseases like metabolic disorders, autism, or inflammation-associated diseases such as lung injury, autoimmune disease, asthma, and type-2 diabetes display aberrant gene expression and epigenetic regulation during their occurrence. The change in the epigenetic pattern of a gene may also alter gene function because of a change in the DNA status. Constant environmental pressure, lifestyle, as well as food habits are the other important parameters responsible for transgenerational inheritance of epigenetic traits. Discovery of epigenetic modifiers targeting DNA methylation and histone deacetylation enzymes could be an alternative source to treat or manipulate the pathogenesis of diseases. Particularly, the combination of epigenetic drugs such as 5-aza-2-deoxycytidine (Aza) and trichostatin A (TSA) are well studied to reduce inflammation in an acute lung injury model. It is important to understand the epigenetic machinery and the function of its components in specific diseases to develop targeted epigenetic therapy. Moreover, it is equally critical to know the specific inhibitors other than the widely used pan inhibitors in clinical trials and explore their roles in regulating specific genes in a more defined way during infection.

Late Maternal Folate Supplementation Rescues from Methyl Donor Deficiency-Associated Brain Defects by Restoring Let-7 and miR-34 Pathways

The micronutrients folate and vitamin B12 are essential for the proper development of the central nervous system, and their deficiency during pregnancy has been associated with a wide range of disorders. They act as methyl donors in the one-carbon metabolism which critically influences epigenetic mechanisms. In order to depict further underlying mechanisms, we investigated the role of let-7 and miR-34, two microRNAs regulated by methylation, on a rat model of maternal deficiency. In several countries, public health policies recommend periconceptional supplementation with folic acid. However, the question about the duration and periodicity of supplementation remains. We therefore tested maternal supply (3 mg/kg/day) during the last third of gestation from embryonic days (E) 13 to 20. Methyl donor deficiency-related developmental disorders at E20, including cerebellar and interhemispheric suture defects and atrophy of selective cerebral layers, were associated with increased brain expression (by 2.5-fold) of let-7a and miR-34a, with subsequent downregulation of their regulatory targets such as Trim71 and Notch signaling partners, respectively. These processes could be reversed by siRNA strategy in differentiating neuroprogenitors lacking folate, with improvement of their morphological characteristics. While folic acid supplementation helped restoring the levels of let-7a and miR-34a and their downstream targets, it led to a reduction of structural and functional defects taking place during the perinatal period. Our data outline the potential role of let-7 and miR-34 and their related signaling pathways in the developmental defects following gestational methyl donor deficiency and support the likely usefulness of late folate supplementation in at risk women.

Effects of maternal folic acid supplementation on gene methylation and being small for gestational age

BACKGROUND

Being small for gestational age (SGA), a foetal growth abnormality, has a long-lasting impact on childhood health. Its aetiology and underlying mechanisms are not well understood. Underlying epigenetic changes of imprinted genes have emerged as a potential pathological pathway because they may be associated with growth, including SGA. As a common methyl donor, folic acid (FA) is essential for DNA methylation, synthesis and repair, and FA supplementation is widely recommended for women planning pregnancy. The present study aimed to investigate the inter-relationships among methylation levels of two imprinted genes [H19 differentially methylated regions (DMRs) and MEST DMRs], maternal FA supplementation and SGA.

METHODS

We conducted a case-control study. Umbilical cord blood was taken from 39 SGA infants and 49 controls whose birth weights are appropriate for gestational age (AGA). DNA methylation levels of H19 and MEST DMRs were determined by an analysis of mass array quantitative methylation.

RESULTS

Statistically significantly higher methylation levels were observed at sites 7.8, 9 and 17.18 of H19 (P = 0.030, 0.016 and 0.050, respectively) in the SGA infants compared to the AGA group. In addition, the association was stronger in male births where the mothers took FA around conception at six H19 sites (P = 0.004, 0.005, 0.048, 0.002, 0.021 and 0.005, respectively).

CONCLUSIONS

Methylation levels at H19 DMRs were higher in SGA infants compared to AGA controls. It appears that the association may be influenced by maternal peri-conception FA supplementation and also be sex-specific.

Impact of epigenetic dietary compounds on transgenerational prevention of human diseases

The etiology of most human diseases involves complicated interactions of multiple environmental factors with individual genetic background which is initially generated early in human life, for example, during the processes of embryogenesis and fetal development in utero. Early embryogenesis includes a series of programming processes involving extremely accurate time-controlled gene activation/silencing expressions, and epigenetic control is believed to play a key role in regulating early embryonic development. Certain dietary components with properties in influencing epigenetic processes are believed to have preventive effects on many human diseases such as cancer. Evidence shows that in utero exposure to certain epigenetic diets may lead to reprogramming of primary epigenetic profiles such as DNA methylation and histone modifications on the key coding genes of the fetal genome, leading to different susceptibility to diseases later in life. In this review, we assess the current advances in dietary epigenetic intervention on transgenerational human disease control. Enhanced understanding of the important role of early life epigenetics control may lead to cost-effective translational chemopreventive potential by appropriate administration of prenatal and/or postnatal dietary supplements leading to early disease prevention.

DNA methylation program during development

DNA methylation is a key epigenetic mark when occurring in the promoter and enhancer regions regulates the accessibility of the binding protein and gene transcription. DNA methylation is inheritable and can be de novo-synthesized, erased and reinstated, making it arguably one of the most dynamic upstream regulators for gene expression and the most influential pacer for development. Recent progress has demonstrated that two forms of cytosine methylation and two pathways for demethylation constitute ample complexity for an instructional program for orchestrated gene expression and development. The forum of the current discussion and review are whether there is such a program, if so what the DNA methylation program entails, and what environment can change the DNA methylation program. The translational implication of the DNA methylation program is also proposed.

Peptide fingerprinting of folate-responsive proteins in human B lymphoblasts and orofacial clefting

BACKGROUND

Maternal periconceptional use of folic acid contributes to the prevention of neural crest-related congenital malformations including orofacial clefts. The underlying biological pathways affected by folic acid,however, are still not clarified. In an explorative study, we identify folate-responsive proteins and pathways by advanced proteomic techniques and their possible role in orofacial development in young children.

MATERIALS AND METHODS

At 15 months of age, we obtained B lymphoblasts from 10 children with and 10 children without an orofacial cleft. Folate-responsive protein expression was determined in folate-free B-lymphoblast cultures, supplemented with 5-methyltetrahydrofolate to reach the target concentration 30 nM. Folate-associated differences of peptide and protein expressions were assessed by analysing samples before and after folate addition. Samples were trypsin digested and measured by nano-liquid chromatography coupled online to a LTQ-Orbitrap mass spectrometer. Significantly differentiating peptides were determined using a McNemar’s test, and correlations with proteins and existing pathways were visualized using Ingenuity Pathway Analysis.

RESULTS

We found 39 folate-responsive peptides that were assigned to 30 proteins. Those proteins consisted of histones, ribosomal and heat shock proteins (HSP), and proteins involved in antioxidant reactions, cytoskeleton,glycolysis, energy production, protein processing, signal transduction and translation.

CONCLUSIONS

Histones, ribosomal and HSP were mainly found in the case group, and we confirm that almost 60% of these proteins were also found in a subset of the samples in our previous study using microarray on folate-responsive gene expression. The proteins were compared with known biological pathways and matched with recent relevant literature.

Senescence is accelerated through donor cell specificity in cloned pigs

Animals cloned by somatic cell nuclear transfer (SCNT) sometimes have abnormalities that result in large offspring syndrome or early death during gestation due to respiratory and metabolic defects. We cloned pigs using two sources of donor cells and observed phenotypic anomalies in three pigs cloned from one type of cell, s-pig fetal fibroblasts. These animals had many wrinkles on their faces and bodies and looked older than age-matched normal pigs. We performed the present study to examine whether the wrinkled phenotype in the cloned pigs was due to senescence, a genetic problem with donor specificity, or epigenetic problems with reprogramming. To address this issue, we investigated biomarkers of senescence, including telomere length and the expression of senescence-associated β-galactosidase (SA-β-gal), glyceraldehyde phosphate dehydrogenase (GAPDH) and β-actin. We also assessed the methylation status of euchromatic PRE-1 repetitive sequences and centromeric satellite DNA, and measured the mRNA levels of six imprinted genes, Copg2, Mest, Igf2R, GNAS, SNRPN and Ube3a. The telomeres of the wrinkled cloned pigs were much shorter than those of the normal cloned pigs and age-matched normal pigs. In the wrinkled cloned pigs, SA-β-gal activity was detected and GAPDH and β-actin were repressed. The mRNA levels of Mest, GNAS and Ube3a were reduced in the wrinkled cloned pigs, although there was no difference between the normal cloned pigs and normal controls. This gene expression analysis indicates that the wrinkled abnormality of our pigs originates from genetic abnormalities in the donor cells used for SCNT.

Association of genomic instability, and the methylation status of imprinted genes and mismatch-repair genes, with neural tube defects

We studied the genomic instability and methylation status of the mismatch-repair (MMR) genes hMLH1 and hMSH2, and the imprinted genes H19/IGF2, in fetuses with neural tube defects (NTDs) to explore the pathogenesis of the disease. Microsatellite instability (MSI) was observed in 23 of 50 NTD patients. Five NTD patients showed high-degree MSI (MSI-H) and 18 showed low-degree MSI (MSI-L). The frequencies of mutated microsatellite loci were 3/50 (6%) for BatT-25, 10/50 (20%) for Bat-26, 3/50 (6%) for Bat34C4, 6/50 (12%) for D2S123, 4/50 (8%) for D2S119, and 3/50 (6%) for D3S1611. The promoter regions of the hMLH1 and hMSH2 genes were unmethylated in NTD patients, as determined by methylation-specific PCR. The hMLH1 and hMSH2 promoter methylation patterns, the methylation levels of H19 DMR1, and IGF2 DMR0 were detected by bisulfite sequencing PCR, sub-cloning, and sequencing. The hMSH2 promoter sequence was unmethylated, and the hMLH1 promoter showed a specific methylation pattern at two CpG sites. The methylation levels of H19 DMR1 in the NTD and control groups are 73.3% ± 15.9 and 58.3% ± 11.2, respectively. The methylation level of the NTD group was higher than that of the control group (Student's t-test, P<0.05). There is no significant difference in IGF2 DMR0 methylation level between the two groups. All of the results presented here suggest that genomic instability, the MMR system, and hyper-methylation of the H19 DMR1 may be correlated with the occurrence of NTDs.

Diet, epigenetics, and cancer

Cancer encompasses a highly heterogeneous group of diseases. It has been thought that transition from promotion to progression in carcinogenesis may be driven primarily by epigenetic abnormalities. Diet is known to play crucial roles in cancer etiology and has an important role in epigenetics. Current knowledge in the interrelationship among cancer, nutrition and epigenetics is reviewed.

Maternal folic acid supplement intake and semen quality in Danish sons: a follow-up study

OBJECTIVE

To examine whether maternal folic acid supplement intake during pregnancy is related to better semen quality in male offspring.

DESIGN

A follow-up study.

SETTING

Two major Danish municipalities, Aalborg and Odense.

PATIENT(S)

The study population included 347 singleton sons of mothers enrolled into the Healthy Habits for Two cohort when pregnant in 1984-87.

INTERVENTION(S)

Information on maternal folic acid supplement intake during pregnancy was provided by self-administered questionnaire in the 36th week of gestation.

MAIN OUTCOME MEASURE(S)

Semen characteristics and serum concentrations of sex hormones.

RESULT(S)

The distribution of semen characteristics among sons whose mothers took folic acid supplement during pregnancy (n = 88, 25%) did not differ from the distributions among those without (n = 75, 22%) or with unknown folic acid supplement intake (n = 84, 53%). On the contrary, serum levels of FSH and LH were significantly higher in the folic acid supplement group.

CONCLUSION(S)

The hypothesis that folic acid supplement intake during pregnancy will improve semen quality in male offspring was not corroborated by a follow-up study in young Danish men.

Epigenetics in women's health care

Epigenetics refers to structural modifications to genes that do not change the nucleotide sequence itself but instead control and regulate gene expression. DNA methylation, histone modification, and RNA regulation are some of the mechanisms involved in epigenetic modification. Epigenetic changes are believed to be a result of changes in an organism's environment that result in fixed and permanent changes in most differentiated cells. Some environmental changes that have been linked to epigenetic changes include starvation, folic acid, and various chemical exposures. There are periods in an organism's life cycle in which the organism is particularly susceptible to epigenetic influences; these include fertilization, gametogenesis, and early embryo development. These are also windows of opportunity for interventions during the reproductive life cycle of women to improve maternal-child health. New data suggest that epigenetic influences might be involved in the regulation of fetal development and the pathophysiology of adult diseases such as cancer, diabetes, obesity, and neurodevelopmental disorders. Various epigenetic mechanisms may also be involved in the pathogenesis of preeclampsia and intrauterine growth restriction. Additionally, environmental exposures are being held responsible for causing epigenetic changes that lead to a disease process. Exposure to heavy metals, bioflavonoids, and endocrine disruptors, such as bisphenol A and phthalates, has been shown to affect the epigenetic memory of an organism. Their long-term effects are unclear at this point, but many ongoing studies are attempting to elucidate the pathophysiological effects of such gene-environment interactions.

Protective effects of leptin during the suckling period against later obesity may be associated with changes in promoter methylation of the hypothalamic pro-opiomelanocortin gene

Leptin supplementation of neonatal rats during the suckling period protects against being overweight in adulthood and ameliorates the control of food intake. This was associated with changes in the expression of hypothalamic genes involved in the central action of leptin: pro-opiomelanocortin (Pomc), leptin receptor (Lepr) and suppressor of cytokine signalling (Socs3). The purpose of the present study was to determine the methylation status within the promoter regions of these genes and to assess whether the observed changes in the expression levels of these genes could be explained by changes in their methylation status. Male rats were treated daily with an oral physiological dose of leptin or vehicle during the suckling period. After weaning, animals were fed with a normal-fat or a high-fat (HF) diet until aged 6 months. DNA was extracted from the hypothalamus and methylation within the promoter regions of the gene panel was measured by pyrosequencing. Pomc promoter methylation increased in control animals fed the HF diet but decreased in leptin-treated animals. In addition, there was a weak negative correlation between DNA methylation and POMC mRNA levels (P = 0·075). There were no changes in the methylation status of the CpG sites studied within the promoter regions of Lepr and Socs3 in response to leptin or HF treatments. This is the first demonstration that leptin treatment during lactation may programme methylation of an appetite-related gene in the hypothalamus of animals fed HF diets, with possible implications for gene expression and protection against the development of obesity.

Gene expression in the placenta: maternal stress and epigenetic responses

Successful placental development is crucial for optimal growth, development, maturation and survival of the embryo/fetus into adulthood. Numerous epidemiologic and experimental studies have demonstrated the profound influence of intrauterine environment on life, and the diseases to which one is subject as an adult. For the most part, these invidious influences, whether maternal hypoxia, protein or caloric deficiency or excess, and others, represent types of maternal stress. In the present review, we examine certain aspects of gene expression in the placenta as a consequence of maternal stressors. To examine these issues in a controlled manner, and in a species in which the genome has been sequenced, most of these reported studies have been performed in the mouse. Although each individual maternal stress is characterized by up- or down-regulation of specific genes in the placenta, functional analysis reveals some patterns of gene expression common to the several forms of stress. Of critical importance, these genes include those involved in DNA methylation and histone modification, cell cycle regulation, and related global pathways of great relevance to epigenesis and the developmental origins of adult health and disease.

Pharmacology of epigenetics in brain disorders

Epigenetics is a rapidly growing field and holds great promise for a range of human diseases, including brain disorders such as Rett syndrome, anxiety and depressive disorders, schizophrenia, Alzheimer disease and Huntington disease. This review is concerned with the pharmacology of epigenetics to treat disorders of the epigenome whether induced developmentally or manifested/acquired later in life. In particular, we will focus on brain disorders and their treatment by drugs that modify the epigenome. While the use of DNA methyl transferase inhibitors and histone deacetylase inhibitors in in vitro and in vivo models have demonstrated improvements in disease-related deficits, clinical trials in humans have been less promising. We will address recent advances in our understanding of the complexity of the epigenome with its many molecular players, and discuss evidence for a compromised epigenome in the context of an ageing or diseased brain. We will also draw on examples of species differences that may exist between humans and model systems, emphasizing the need for more robust pre-clinical testing. Finally, we will discuss fundamental issues to be considered in study design when targeting the epigenome.

DNA methylation, an epigenetic mechanism connecting folate to healthy embryonic development and aging

Experimental studies demonstrated that maternal exposure to certain environmental and dietary factors during early embryonic development can influence the phenotype of offspring as well as the risk of disease development at the later life. DNA methylation, an epigenetic phenomenon, has been suggested as a mechanism by which maternal nutrients affect the phenotype of their offspring in both honeybee and agouti mouse models. Phenotypic changes through DNA methylation can be linked to folate metabolism by the knowledge that folate, a coenzyme of one-carbon metabolism, is directly involved in methyl group transfer for DNA methylation. During the fetal period, organ-specific DNA methylation patterns are established through epigenetic reprogramming. However, established DNA methylation patterns are not immutable and can be modified during our lifetime by the environment. Aberrant changes in DNA methylation with diet may lead to the development of age-associated diseases including cancer. It is also known that the aging process by itself is accompanied by alterations in DNA methylation. Diminished activity of DNA methyltransferases (Dnmts) can be a potential mechanism for the decreased genomic DNA methylation during aging, along with reduced folate intake and altered folate metabolism. Progressive hypermethylation in promoter regions of certain genes is observed throughout aging, and repression of tumor suppressors induced by this epigenetic mechanism appears to be associated with cancer development. In this review, we address the effect of folate on early development and aging through an epigenetic mechanism, DNA methylation.

Addressing a folate imbalance in fetal cerebrospinal fluid can decrease the incidence of congenital hydrocephalus

Fetal-onset hydrocephalus (HC), which affects between 1:500 and 1:5000 live human births, results from unequal production and drainage of cerebrospinal fluid (CSF) and is associated with abnormal development of the cerebral cortex leading to severe neurological deficits. We previously found that in the hydrocephalic Texas rat, the CSF of affected fetuses induced a cell cycle arrest in neural progenitor cells. Here, we show that alterations in folate metabolism in the CSF of the developing cerebrum are likely responsible for this effect. We identified 3 folate enzymes in the CSF and demonstrate that low levels of one of these, 10-formyltetrahydrofolate dehydrogenase, are associated with HC in the hydrocephalic Texas rat. Therefore, we tested whether supplementation with specific folate species would improve developmental outcome. After daily administration of a combination of tetrahydrofolic and 5-formyltetrahydrofolic acids to pregnant dams, there was a significant reduction in the incidence of HC and improved brain development. By contrast, supplementation with folic acid increased the incidence of congenital HC in this model. These results indicate the complexities of folate metabolism in the developing brain and suggest that folate imbalance leading to HC in the hydrocephalic Texas rat fetuses can be treated with maternal folate supplementation using specific folate metabolites and combinations thereof.

A methyl-deficient diet modifies histone methylation and alters Igf2 and H19 repression in the prostate

BACKGROUND

Folate and methyl-group deficiency has been linked to prostate cancer susceptibility, yet the mechanisms underlying these observations are incompletely understood. The region of the genome containing the imprinted genes insulin-like growth factor 2 (Igf2) and H19, both of which display oncogenic functions, may be particularly sensitive to environmental influences.

METHODS

To determine whether a methyl-deficient diet impacts epigenetic controls at the Igf2-H19 locus, we placed C57BL/6 mice containing a polymorphism at the imprinted Igf2-H19 locus on a choline and methionine deficient (CMD) diet. We interrogated this locus for expression and epigenetic changes in prostate tissues.

RESULTS

A significant increase in both Igf2 and H19 expression was found in CMD prostate tissues compared to controls. These expression changes were reversible with shorter exposure to the CMD diet. Chromatin immunoprecipitation (ChIP) revealed significant decreases in repressive histone modifications (dimethyl-H3K9) within the H19 promoter, as well as Igf2 P2 and P3 promoters. DNA methylation within these promoters was not altered. No significant change in Igf2 or H19 imprinting was observed.

CONCLUSIONS

These findings highlight the plasticity of the epigenome in an epithelial organ vulnerable to neoplastic change. They further suggest that chromatin modifications are more susceptible to methyl-deficient diets than DNA methylation at this locus.

A role for Drosophila in understanding drug-induced cytotoxicity and teratogenesis

Drosophila research has been and continues to be an essential tool for many aspects of biological scientific research and has provided insight into numerous genetic, biochemical, and behavioral processes. As well, due to the remarkable conservation of gene function between Drosophila and humans, and the easy ability to manipulate these genes in a whole organism, Drosophila research has proven critical for studying human disease and the physiological response to chemical reagents. Methotrexate, a widely prescribed pharmaceutical which inhibits dihydrofolate reductase and therefore folate metabolism, is known to cause teratogenic effects in human fetuses. Recently, there has been resurgence in the use of methotrexate for inflammatory diseases and ectopic or unwanted pregnancies thus, increasing the need to fully understand the cytotoxicity of this pharmaceutical. Concerns have been raised over the ethics of studying teratogenic drugs like methotrexate in mammalian systems and thus, we have proposed a Drosophila model. We have shown that exposure of female Drosophila to methotrexate results in progeny with developmental abnormalities. We have also shown that methotrexate exposure changes the abundance of many fundamental cellular transcripts. Expression of a dihydrofolate reductase with a reduced affinity for methotrexate can not only prevent much of the abnormal transcript profile but the teratogenesis seen after drug treatment. In the future, such studies may generate useful tools for mammalian antifolate "rescue" therapies.

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.

Nutri-epigenomics: lifelong remodelling of our epigenomes by nutritional and metabolic factors and beyond

The phenotype of an individual is the result of complex interactions between genotype, epigenome and current, past and ancestral environment, leading to lifelong remodelling of our epigenomes. Various replication-dependent and -independent epigenetic mechanisms are involved in developmental programming, lifelong stochastic and environmental deteriorations, circadian deteriorations, and transgenerational effects. Several types of sequences can be targets of a host of environmental factors and can be associated with specific epigenetic signatures and patterns of gene expression. Depending on the nature and intensity of the insult, the critical spatiotemporal windows and developmental or lifelong processes involved, these epigenetic alterations can lead to permanent changes in tissue and organ structure and function, or to reversible changes using appropriate epigenetic tools. Given several encouraging trials, prevention and therapy of age- and lifestyle-related diseases by individualised tailoring of optimal epigenetic diets or drugs are conceivable. However, these interventions will require intense efforts to unravel the complexity of these epigenetic, genetic and environment interactions and to evaluate their potential reversibility with minimal side effects.

Hyperhomocysteinemia and MTHFR polymorphisms in association with orofacial clefts and congenital heart defects: a meta-analysis

Several studies have reported an association between hyperhomocysteinemia, 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms and cleft lip with or without cleft palate (CLP), and congenital heart defects (CHDs). However, findings have been inconsistent. A meta-analysis was performed of published studies until September 2006 investigating these associations in both mothers and children. Homocysteine data were provided in two CLP and three CHD studies, and MTHFR polymorphisms were reported in ten CLP and eight CHD studies. Data were analyzed using the random effects model in the Cochrane Review Manager. The pooled odds ratio (OR) of maternal hyperhomocysteinemia was 2.3 (95% CI 0.4-11.9) for CLP, and 4.4 (2.6-7.3) for CHDs. The MTHFR C677T polymorphism and CLP showed pooled ORs of 1.2 (0.9-1.5) in mothers and 1.0 (0.9-1.2) in children, whereas these estimates for the A1298C polymorphism were 1.0 (0.7-1.2) in mothers and 0.9 (0.6-1.2) in children. The MTHFR C677T polymorphism in CHD studies demonstrated a pooled OR of 1.0 (0.8-1.3) for mothers and 1.1 (0.9-1.5) for children. Two studies investigating the maternal A1298C polymorphism in CHDs demonstrated a pooled OR of 1.2 (0.8-1.8). Only one CHD study reported an OR of 1.3 (0.8-2.1) for this polymorphism in children. In conclusion, this meta-analysis demonstrates that maternal hyperhomocysteinemia is a risk factor for CHDs. The MTHFR polymorphisms C677T and A1298C in both mothers and children are not independently associated with CLP or CHDs. Future studies should be performed to investigate the interactions between maternal hyperhomocysteinemia, B-vitamin intake, related polymorphisms and the risk of CLP and CHDs.

Transgenic rescue of methotrexate-induced teratogenicity in Drosophila melanogaster

The folic acid analog methotrexate (MTX), a competitive inhibitor of dihydrofolate reductase (DHFR), is used to treat a variety of cancers and autoimmune disorders. However, MTX also causes a wide range of toxic effects in healthy cells and is an established teratogen. Efforts to "rescue" the defects caused by MTX by administering a folate analog or by transgenic expression of a DHFR with an altered affinity for MTX have been attempted in a variety of mammals but limited protection was conferred. As a result, our understanding of the effect of MTX at the molecular genetic level remains incomplete and, in addition, continued mammalian sacrifice is not ideal. Due to the similarity of teratogenic effects produced by MTX in Drosophila melanogaster these insects were transformed with DHFR alleles to determine if rescue could be achieved. The resulting "MTX-resistant" flies were subsequently used to investigate changes in gene expression in response to MTX using semiquantitative reverse transcription PCR. The majority (12/14) of key transcripts that were affected in MTX-exposed females including transcripts involved in cell cycle, defense response, and transport were "rescued" in the "MTX-resistant" transgenic flies. These studies illustrate the utility of this invertebrate model for the investigation of molecular effects of MTX-induced teratogenicity, MTX-resistant DHFRs for gene therapy techniques, and teratogenic protection.

Dietary intake of B-vitamins in mothers born a child with a congenital heart defect

BACKGROUND

Periconceptional use of multivitamins reduces the risk of a child with a congenital heart defect (CHD). Data on the impact of maternal diet, however, are lacking.

AIM OF THE STUDY

We investigated the association between the maternal dietary intake of B-vitamins and having a child with a CHD.

METHODS

A case-control study was performed in 192 mothers of a child with a CHD and 216 mothers of a healthy child. Mothers filled out food frequency questionnaires covering the current dietary intake, and general questionnaires at 17 months after the index-pregnancy. Maternal blood samples were taken to determine B-vitamin and plasma total homocysteine (tHcy) concentrations as nutritional biomarkers. Pregnant and lactating mothers and those with another diet compared with the preconceptional period were excluded for analysis. Case-mothers and controls were compared using the Mann-Whitney U test and logistic regression.

RESULTS

The dietary intake of macronutrients and B-vitamins was comparable between both groups, but all mothers had a substantially lower median folate intake (cases 161 microg, controls 175 microg) than the Dutch recommended dietary allowance of 300 microg. Within the case-group, the intake of proteins and vitamin B(6) and the concentrations of serum vitamin B(12) and folate were significantly lower in hyperhomocysteinemics (tHcy > or = 14.5 micromol/l) than in normohomocysteinemics. The maternal educational level was positively associated with B-vitamin intake, except for vitamin B(12) in controls. Low educated case-mothers showed a significantly lower median vitamin B(12) intake than controls (2.8 microg and 3.8 microg, P = 0.01). The CHD risk doubled if vitamin B(12) intake in these mothers reduced by 50% (OR 2.0; 95% CI: 1.1-3.5).

CONCLUSIONS

A diet low in vitamin B(12) is associated with an increased risk of a child with a CHD, especially in low educated women. A disbalance in the maternal intake of proteins and low folate intake may play a role as well, but needs further investigation. As hyperhomocysteinemia is a strong risk factor for adult cardiovascular disease, these data may imply that the hyperhomocysteinemic mothers and their children should be targeted for nutritional interventions.

Maternal hyperhomocysteinaemia is a risk factor for congenital heart disease

OBJECTIVE

To investigate the inter-relation between mother and infant homocysteine, folate and vitamin B12 status and the risk of a child with congenital heart disease (CHD).

DESIGN

Case-control study.

SETTING

Erasmus MC, University Medical Centre, Rotterdam, the Netherlands.

POPULATION

Participants were 149 case-mothers and their children with CHD (n = 151) and 183 control-mothers with their children (n = 175).

METHODS

Approximately 17 months after the index-pregnancy maternal fasting, children's random venous blood samples were drawn to measure plasma total homocysteine, serum and red blood cell (RBC) folate, and serum vitamin B12 concentrations. Data were compared between cases and controls using the Mann-Whitney U test. The biochemical parameters were dichotomised according to the cutoff value of the 10th percentile of vitamin concentrations and the 90th percentile of homocysteine concentrations based on control data. Risk estimates for the association between CHD and the biochemical parameters were estimated in a logistic regression model.

MAIN OUTCOME MEASURES

Medians (minimum-maximum) and odds ratios (OR) (95% confidence intervals [CI]).

RESULTS

The OR (95% CI) of having a child with CHD was 2.9 (1.4-6.0) for maternal hyperhomocysteinaemia (>14.3 micromol/l). This finding is substantiated by a significant concentration-dependent risk (Ptrend = 0.004). Hyperhomocysteinaemic case-mothers showed significantly lower serum folate and vitamin B12 concentrations than normohomocysteinaemic case-mothers. Serum and RBC folate concentrations were significantly higher in case-children than that in control-children.

CONCLUSIONS

Maternal hyperhomocysteinaemia is associated with an increased risk of CHD, partially due to low folate and vitamin B12 status. The folate status of children warrants further investigation.

Maspin expression is characteristic for cisplatin-sensitive ovarian cancer cells and for ovarian cancer cases of longer survival rates

High cytoplasmic expression of maspin was described in ovarian cancers of shorter survival rates. Until now, no relationship has been described between expression of maspin and sensitivity to cisplatin in ovarian cancers. This study aimed at examining the relationship between expression of maspin, detected by immunohistochemistry and clinical response to cisplatin in ovarian cancer cases as well as the in vitro sensitivity to cisplatin of 11 ovarian cancer cell lines. The analyzes were performed on 73 samples of ovarian cancer and on A2780P, A2780RCIS, CAOV-3, EFO 21, EFO 27, ES-2, Mdah 2774, OAW 42, OVCAR-3, PA-1, and SKOV-3 ovarian cancer cells. Cytoplasmic maspin expression in studied cells significantly correlated with cisplatin sensitivity. A significantly shorter overall survival and progression-free survival was associated with lower cytoplasmic maspin expression at first-look laparotomies and nuclear maspin expression and secondary cytoreductions. Higher nuclear maspin at first-look laparotomies expression was specific for cases of complete response. In the study, the elevated expression of maspin was shown to be typical for cisplatin-sensitive ovarian cancers.

Environmental and nutritional effects on the epigenetic regulation of genes

Major efforts have been directed towards the identification of genetic mutations, their use as biomarkers, and the understanding of their consequences on human health and well-being. There is an emerging interest, however, in the possibility that environmentally-induced changes at levels other than the genetic information could have long-lasting consequences as well. This review summarises our current knowledge of how the environment, nutrition, and ageing affect the way mammalian genes are organised and transcribed, without changes in the underlying DNA sequence. Admittedly, the link between environment and epigenetics remains largely to be explored. However, recent studies indicate that environmental factors and diet can perturb the way genes are controlled by DNA methylation and covalent histone modifications. Unexpectedly, and not unlike genetic mutations, aberrant epigenetic alterations and their phenotypic effects can sometimes be passed on to the next generation.

A life-course approach to the aetiology of late-onset dementias

Substantial progress has been made in the understanding of the neurobiology of dementias, but comprehensive causal models are not available. Genetic and environmental factors probably interact to determine vulnerability to the dementias. The life-course approach to age-related diseases, when systematically applied to the dementias, provides opportunities to identify the nature and timing of environmental contributions. We discuss the relevance of the fetal origins of adult disease hypothesis to the dementias. Associations between the dementias (most often described as Alzheimer's disease) and ischaemic heart disease, obesity, hypertension, hyperlipidaemia, and non-insulin-dependent diabetes mellitus are set against associations between dementias and childhood intelligence, low educational attainments, low socioeconomic status, occupation, and lifetime dietary history. Biological mechanisms that explain how fetal development might influence the risk of adult disease may be relevant to many age-related diseases including the dementias and, possibly, to the biology of ageing.