Maternal hyperhomocysteinemia: a risk factor for neural-tube defects?

Profiling the Influence of Gene Variants Related to Folate-Mediated One-Carbon Metabolism on the Outcome of In Vitro Fertilization (IVF) with Donor Oocytes in Recipients Receiving Folic Acid Fortification

Nutritional status and gene polymorphisms of one-carbon metabolism confer a well-known interaction that in pregnant women may affect embryo viability and the health of the newborn. Folate metabolism directly impacts nucleotide synthesis and methylation, which is of increasing interest in the reproductive medicine field. Studies assessing the genetic influence of folate metabolism on IVF treatments have currently been performed in women using their own oocytes. Most of these patients seeking to have a child or undergoing IVF treatments are advised to preventively intake folate supplies that restore known metabolic imbalances, but the treatments could lead to the promotion of specific enzymes in specific women, depending on their genetic variance. In the present study, we assess the influence of candidate gene variants related to folate metabolism, such as Serine Hydroxymethyltransferase 1 SHMT1 (rs1979276 and rs1979277), Betaine-Homocysteine S-Methyltransferase BHMT (rs3733890), Methionine synthase reductase MTRR (rs1801394), Methylenetetrahydrofolate reductase MTHFR (rs1801131 and rs1801133), methionine synthase MTR (rs12749581), ATP Binding Cassette Subfamily B Member 1 ABCB1 (rs1045642) and folate receptor alpha FOLR1 (rs2071010) on the success of IVF treatment performed in women being recipients of donated oocytes. The implication of such gene variants seems to have no direct impact on pregnancy consecution after IVF; however, several gene variants could influence pregnancy loss events or pregnancy maintenance, as consequence of folic acid fortification.

Maternal biomarkers for early prediction of the neural tube defects pregnancies

BACKGROUND

Neural tube defects (NTD) are one of the most common congenital birth defects. The reason for the NTD cause is still not completely known, but it is believed that some genetic and environmental factors might play a role in its etiology. Among the genetic factors the polymorphism in the folate gene pathway is crucial. Numerous studies have suggested the possible role of maternal higher plasma concentration of homocysteine and low concentration of folate and cobalamin in the development of NTD but some negative studies are also published.

AIM

Aim of the present was to find out the exact relation between NTD and maternal biomarkers like folate, cobalamin and homocysteine by conducting a meta-analysis.

METHOD

Different electronic databases were searched for the eligible studies. Standardized mean difference (SMD) with 95% confidence interval (CI) was used to determine association between maternal markers as risk for NTD pregnancy. The p value <0.05 was considered statistically significant in all tests. All the statistical analyses were done in the Open Meta-Analyst program.

RESULTS

The homocysteine is significantly associated with the increased risk of NTD (SMD = 0.57; 95% CI: 0.35-0.80, p = <0.001; I2 = 93.01%), s-folate showed protective role in NTD (SMD = -0.48; 95% CI: -0.77 to -0.19, p = 0.001; I2 = 95.73%), similarly cobalamin is also having protective role (SMD = -0.28; 95% CI: -0.43 to -0.13, p = <0.001; I2 = 80.40%).

CONCLUSION

In conclusion this study suggest that different maternal biomarkers may be used for the early prediction of the NTDs.

High-concentration homocysteine inhibits mitochondrial respiration function and production of reactive oxygen species in neuron cells

OBJECTIVE

Homocysteine plays critical roles in cellular redox homeostasis, and hyperhomocysteinemia has been associated with multiple diseases, including neurological disorders involving reactive oxygen species-inducing and pro-inflammatory effects of homocysteine that are related to mitochondria. This study investigated the role of homocysteine in regulating mitochondria of neuron cell lines.

METHODS

Neuron cells were pre-treated with homocysteine, and then flow cytometry was used to detect reactive oxygen species production and mitochondrial membrane potential, while Seahorse XFp Mito stress assay was used to comprehensively analyze mitochondrial function.

RESULTS

The experimental results showed that high-concentration homocysteine diminished carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone-stimulated oxygen consumption rate and mitochondrial spare respiration capacity in a time- and concentration-dependent manner, and homocysteine also reduced reactive oxygen species in cultured neuron cell lines while no changes in mitochondrial membrane potential were observed.

CONCLUSION

These results indicate that homocysteine diminished mitochondrial respiration function in neuron cell lines mediated by its reactive oxygen species-reducing effects, which may underlie the association between hyperhomocysteinemia and human diseases.

One-carbon metabolism and folate transporter genes: Do they factor prominently in the genetic etiology of neural tube defects?

Neural tube defects (NTDs) are a broad class of congenital birth defects that result from the failure of neural tube closure during neurulation. Folic acid supplementation has been shown to prevent the occurrence of NTDs by as much as 70% in some human populations, and folate deficiency in a pregnant woman is associated with increased risk for having an NTD affected infant. Thus, folate transport-related genes and genes involved in the subsequent folate-mediated one-carbon metabolic pathway have long been considered primary candidates to study the genetic etiology of human NTDs. Herein, we review the genes involved in folate transport and one-carbon metabolism thus far identified as contributing variants that influence human NTD risk, and place these findings in the context of our evolving understanding of the complex genetic architecture underlying these defects.

Integrated analysis of the critical region 5p15.3-p15.2 associated with cri-du-chat syndrome

Cri-du-chat syndrome (CdCs) is one of the most common contiguous gene syndromes, with an incidence of 1:15,000 to 1:50,000 live births. To better understand the etiology of CdCs at the molecular level, we investigated theprotein-protein interaction (PPI) network within the critical chromosomal region 5p15.3-p15.2 associated with CdCs using systemsbiology. Data were extracted from cytogenomic findings from patients with CdCs. Based on clinical findings, molecular characterization of chromosomal rearrangements, and systems biology data, we explored possible genotype-phenotype correlations involving biological processes connected with CdCs candidate genes. We identified biological processes involving genes previously found to be associated with CdCs, such as TERT, SLC6A3, and CTDNND2, as well as novel candidate proteins with potential contributions to CdCs phenotypes, including CCT5, TPPP, MED10, ADCY2, MTRR, CEP72, NDUFS6, and MRPL36. Although further functional analyses of these proteins are required, we identified candidate proteins for the development of new multi-target genetic editing tools to study CdCs. Further research may confirm those that are directly involved in the development of CdCs phenotypes and improve our understanding of CdCs-associated molecular mechanisms.

Genetic polymorphisms of key enzymes in folate metabolism affect the efficacy of folate therapy in patients with hyperhomocysteinaemia

The aim of this study is to analyse the efficacy rate of folate for the treatment of hyperhomocysteinaemia (HHcy) and to explore how folate metabolism-related gene polymorphisms change its efficacy. This study also explored the effects of gene-gene and gene-environment interactions on the efficacy of folate. A prospective cohort study enrolling HHcy patients was performed. The subjects were treated with oral folate (5 mg/d) for 90 d. We analysed the efficacy rate of folate for the treatment of HHcy by measuring homocysteine (Hcy) levels after treatment. Unconditioned logistic regression was conducted to analyse the association between SNP and the efficacy of folic acid therapy for HHcy. The efficacy rate of folate therapy for HHcy was 56·41 %. The MTHFR rs1801133 CT genotype, TT genotype and T allele; the MTHFR rs1801131 AC genotype, CC genotype and C allele; the MTRR rs1801394 GA genotype, GG genotype and G allele; and the MTRR rs162036 AG genotype and AG+GG genotypes were associated with the efficacy of folic acid therapy for HHcy (P<0·05). No association was seen between other SNP and the efficacy of folic acid. The optimal model of gene-gene interactions was a two-factor interaction model including rs1801133 and rs1801394. The optimal model of gene-environment interaction was a three-factor interaction model including history of hypertension, history of CHD and rs1801133. Folate supplementation can effectively decrease Hcy level. However, almost half of HHcy patients failed to reach the normal range. The efficacy of folate therapy may be genetically regulated.

Elevated H3K79 homocysteinylation causes abnormal gene expression during neural development and subsequent neural tube defects

Neural tube defects (NTDs) are serious congenital malformations. Excessive maternal homocysteine (Hcy) increases the risk of NTDs, while its mechanism remains elusive. Here we report the role of histone homocysteinylation in neural tube closure (NTC). A total of 39 histone homocysteinylation sites are identified in samples from human embryonic brain tissue using mass spectrometry. Elevated levels of histone KHcy and H3K79Hcy are detected at increased cellular Hcy levels in human fetal brains. Using ChIP-seq and RNA-seq assays, we demonstrate that an increase in H3K79Hcy level down-regulates the expression of selected NTC-related genes including Cecr2, Smarca4, and Dnmt3b. In human NTDs brain tissues, decrease in expression of CECR2, SMARCA4, and DNMT3B is also detected along with high levels of Hcy and H3K79Hcy. Our results suggest that higher levels of Hcy contribute to the onset of NTDs through up-regulation of histone H3K79Hcy, leading to abnormal expressions of selected NTC-related genes.

Should vitamin B12 status be considered in assessing risk of neural tube defects?

There is a strong biological premise for including vitamin B₁₂ with folic acid in strategies to prevent neural tube defects (NTDs), due to the closely interlinked metabolism of these two vitamins. For example, reduction of B₁₂ deficiency among women of reproductive age could enhance the capacity of folic acid to prevent NTDs by optimizing the cellular uptake and utilization of natural folate cofactors. Vitamin B₁₂ might also have an independent role in NTD prevention, such that adding it in fortification programs might be more effective than fortifying with folic acid alone. Globally, there is ample evidence of widespread vitamin B₁₂ deficiency in low‐ and middle‐income countries, but there is also considerable divergence of vitamin B₁₂ status across regions, likely due to genetic as well as nutritional factors. Here, I consider the evidence that low vitamin B₁₂ status may be an independent factor associated with risk of NTDs, and whether a fortification strategy to improve B₁₂ status would help reduce the prevalence of NTDs. I seek to identify knowledge gaps in this respect and specify research goals that would address these gaps.

Maternal Antenatal Bereavement and Neural Tube Defect in Live-Born Offspring: A Cohort Study

Background

Maternal emotional stress during pregnancy has previously been associated with congenital neural malformations, but most studies are based on data collected retrospectively. The objective of our study was to investigate associations between antenatal maternal bereavement due to death of a close relative and neural tube defects (NTDs) in the offspring.

Methods

We performed a register-based cohort study including all live-born children (N = 1,734,190) from 1978–2008. Exposure was bereavement due to loss of a close relative from one year before conception to the end of the first trimester of pregnancy. The outcome was NTDs in the offspring according to the International Classification of Disease. We used multivariate logistic regression to estimate prevalence odds ratios (ORs).

Results

A total of 2% children were born to mothers who lost a close relative prenatally. During 30 years of follow-up, 1,115 children were diagnosed with any NTDs: spina bifida (n = 889), anencephaly (n = 85) and encephalocele (n = 164). And 23 children were diagnosed with two types of NTDs. Overall, when comparing bereaved mothers to non-bereaved mothers, no significant increased prevalence of NTDs in the offspring was seen (OR = 0.84; 95% confidence interval: 0.52–1.33).

Conclusion

Overall maternal bereavement in the antenatal period was not related to NTDs in liveborn offspring.

Homocystinuria: Therapeutic approach

Homocystinuria is a disorder of sulfur metabolism pathway caused by deficiency of cystathionine β-synthase (CBS). It is characterized by increased accumulation of homocysteine (Hcy) in the cells and plasma. Increased homocysteine results in various vascular and neurological complications. Present strategies to lower cellular and plasma homocysteine levels include vitamin B6 intake, dietary methionine restriction, betaine supplementation, folate and vitamin B12 administration. However, these strategies are inefficient for treatment of homocystinuria. In recent years, advances have been made towards developing new strategies to treat homocystinuria. These mainly include functional restoration to mutant CBS, enhanced clearance of Hcy from the body, prevention of N-homocysteinylation-induced toxicity and inhibition of homocysteine-induced oxidative stress. In this review, we have exclusively discussed the recent advances that have been achieved towards the treatment of homocystinuria. The review is an attempt to help clinicians in developing effective therapeutic strategies and designing novel drugs against homocystinuria.

Evaluation of proton-coupled folate transporter (SLC46A1) polymorphisms as risk factors for neural tube defects and oral clefts

Many folate-related genes have been investigated for possible causal roles in neural tube defects (NTDs) and oral clefts. However, no previous reports have examined the major gene responsible for folate uptake, the proton-coupled folate transporter (SLC46A1). We tested for association between these birth defects and single nucleotide polymorphisms in the SLC46A1 gene. The NTD study population included 549 complete and incomplete case-family triads, and 999 controls from Ireland. The oral clefts study population comprised a sample from Utah (495 complete and incomplete case-family triads and 551 controls) and 221 Filipino multiplex cleft families. There was suggestive evidence of increased NTD case risk with the rs17719944 minor allele (odds ratio (OR): 1.29; 95% confidence intervals (CI): [1.00-1.67]), and decreased maternal risk of an NTD pregnancy with the rs4795436 minor allele (OR: 0.62; [0.39-0.99]). In the Utah sample, the rs739439 minor allele was associated with decreased case risk for cleft lip with cleft palate (genotype relative risk (GRR): 0.56 [0.32-0.98]). Additionally, the rs2239907 minor allele was associated with decreased case risk for cleft lip with cleft palate in several models, and with cleft palate only in a recessive model (OR: 0.41; [0.20-0.85]). These associations did not remain statistically significant after correcting for multiple hypothesis testing. Nominal associations between SLC46A1 polymorphisms and both Irish NTDs and oral clefts in the Utah population suggest some role in the etiology of these birth defects, but further investigation in other populations is needed.

Periconceptional risk factors of spina bifida among Egyptian population: a case-control study

OBJECTIVE

To study the preconceptual & early conceptional risk factors predisposing to the development of spina bifida (SB) among Egyptian population.

STUDY DESIGN

The study involved 197 pregnant women undergoing fetal anatomy scan; 97 women proved to have fetal SB and 100 women with normal fetuses as a control group. The control group was recruited randomly in the same period from patients undergoing anatomical scan. Risk factors that might lead to SB were investigated including maternal age, gravidity, parity, residence, history of diabetes mellitus or drug intake, smoking, infections, exposure to X-ray, history of congenital anomalies in other offspring, parental consanguinity, positive family history, and folate supplementations.

RESULTS

SB affected the lumbo-sacral region in the majority of cases (89.7%). It was associated with hydrocephalus in 66 cases (68%), polyhydramnios in 12 cases (12.4%). The SB group showed significantly higher parity (p = 0.005), more frequent history of drug intake (p < 0.001), higher frequency of infection with CMV (p = 0.004), and HSV (p = 0.013) and less proportion of folate supplementation (p < 0.001).

CONCLUSION

The rate of SB in the tested group was five per 1000. Risk factors were lack of folate supplementation and history of antiepileptic drugs intake.

Quantitative assessment of maternal biomarkers related to one-carbon metabolism and neural tube defects

Periconceptional supplementation with folic acid reduces the occurrence of neural tube defects (NTDs). The association between maternal abnormalities in homocysteine metabolism (e.g., hyperhomocysteinaemia, folate deficiency and low vitamin B12) and the risk of NTDs-affected pregnancies has been widely evaluated in recent years, although the results are conflicting. To investigate this inconsistency, we performed a meta-analysis of 32 studies, involving 1,890 NTD-affected mothers and 3,995 control mothers, to develop an understanding of the relationship between maternal biomarkers related to one-carbon metabolism and NTD. A random-effects model was used to calculate the ratio of means (RoM) between the cases and controls, along with the 95% confidence intervals (CIs). A significant increase in homocysteine levels was observed in NTD-affected mothers compared with controls (RoM: 1.16, 95% CI: 1.09-1.23, P = 1.8 × 10(-6)). The pooled analysis also revealed that NTD-affected mothers had significantly lower levels of folate (RoM: 0.93, 95% CI: 0.88-0.97, P = 0.002), vitamin B12 (RoM: 0.91, 95% CI: 0.87-0.95, P = 3.6 × 10(-5)) and red blood cell folate (RoM: 0.92, 95% CI: 0.86-0.98, P = 0.01). Therefore, altered plasma levels of biomarkers related to one-carbon metabolism are associated with NTD-affected pregnancies.

Markers of macromolecular oxidative damage in maternal serum and risk of neural tube defects in offspring

Neural tube defects (NTDs) are among the most common and severe congenital malformations. To examine the association between markers of macromolecular oxidative damage and risk of NTDs, we measured levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), protein carbonyl (PC), and 8-iso-prostaglandin F2α (8-iso-PGF2α) in maternal serum samples of 117 women with NTD-affected pregnancies and 121 women with healthy term newborns. We found higher levels of 8-OHdG and PC in the NTD group than in the control group; however, we did not observe a statistically significant difference in 8-iso-PGF2α levels between the NTD and the control groups. NTD risk increased with increasing quartiles of 8-OHdG [odds ratio (OR)=1.17; 95% confidence interval (CI) 0.39-3.51; OR=2.19; 95% CI, 0.68-7.01; OR=3.70; 95% CI, 1.30-10.51, for the second, third, and fourth quartile relative to the lowest quartile, respectively; P=0.009], and with increasing quartiles of PC (OR=2.26; 95% CI, 0.66-7.69; OR=3.86; 95% CI, 1.17-12.80; OR=5.98; 95% CI, 1.82-19.66, for the second, third, and fourth quartile relative to the lowest quartile, respectively; P=0.002]. Serum levels of 8-OHdG were higher in women who did not take folic acid supplements during the periconceptional period. These results suggest that oxidative stress is present in women carrying pregnancies affected by NTDs.

5-Mehtyltetrahydrofolate rescues alcohol-induced neural crest cell migration abnormalities

Background

Alcohol is detrimental to early development. Fetal alcohol spectrum disorders (FASD) due to maternal alcohol abuse results in a series of developmental abnormalities including cranial facial dysmorphology, ocular anomalies, congenital heart defects, microcephaly and intellectual disabilities. Previous studies have been shown that ethanol exposure causes neural crest (NC) apoptosis and perturbation of neural crest migration. However, the underlying mechanism remains elusive. In this report we investigated the fetal effect of alcohol on the process of neural crest development in the Xenopus leavis.

Results

Pre-gastrulation exposure of 2-4% alcohol induces apoptosis in Xenopus embryo whereas 1% alcohol specifically impairs neural crest migration without observing discernible apoptosis. Additionally, 1% alcohol treatment considerably increased the phenotype of small head (43.4% ± 4.4%, total embryo n = 234), and 1.5% and 2.0% dramatically augment the deformation to 81.2% ± 6.5% (n = 205) and 91.6% ± 3.0% (n = 235), respectively (P < 0.05). Significant accumulation of Homocysteine was caused by alcohol treatment in embryos and 5-mehtyltetrahydrofolate restores neural crest migration and alleviates homocysteine accumulation, resulting in inhibition of the alcohol-induced neurocristopathies.

Conclusions

Our study demonstrates that prenatal alcohol exposure causes neural crest cell migration abnormality and 5-mehtyltetrahydrofolate could be beneficial for treating FASD.

MTHFR C677T and A1298C Genotypes and Haplotypes in Slovenian Couples with Unexplained Infertility Problems and in Embryonic Tissues from Spontaneous Abortions

The objective of this study was to analyze the methylenetetrahydrofolate reductases ( MTHFR s) C677T and A1298C genotype distributions in couples with unexplained fertility problems (UFP) and healthy controls, and to analyze the genotype and haplotype distribution in spontaneously aborted embryonic tissues (SAET) using allele specific polymerase chain reaction (PCR) in 200 probands with UFP, 353 samples of SAET and 222 healthy controls. The analysis revealed a significant overall representation of the 677T allele in male probands from couples with UFP ( p = 0.036). The combined genotype distribution for both MTHFR polymorphisms was also significantly altered (χ ² 21.73, p <0.001) although female probands made no contribution (χ ² 1.33, p = 0.72). The overall representation of the 677T allele was more pronounced in SAET (0.5 vs. 0.351 in controls, p <0.001) regardless of the karyotype status (aneuploidy vs. normal karyotype). In addition, the frequencies of the CA and CC haplotypes were significantly lower than in the control group ( p = 0.021 and p = 0.001, respectively), whereas the frequency of the TC haplotype was significantly higher than in controls ( p <0.0001). The presented findings indicate that only male probands contribute to the association of MTHFR mutations with fertility problems in grown adults and demonstrate a high prevalence of mutated MTHFR genotypes in SAET.

PCMT1 gene polymorphisms, maternal folate metabolism, and neural tube defects: a case-control study in a population with relatively low folate intake

The PCMT1 gene encodes the protein repair enzyme protein-L-isoaspartate (D-aspartate) O-methyltransferase, which is known to protect certain neural cells against Bax-induced apoptosis. Previous studies have produced inconsistent results regarding the effects of PCMT1 (rs4816 and rs4552) polymorphisms on neural tube defects (NTDs). Reduced maternal plasma folate levels and/or elevated homocysteine (Hcy) levels are considered to be risk factors for NTDs. In order to clarify the key factors contributing to the apparent discrepancy and investigate gene-environment interaction, we conducted a case-control study including 121 cases and 146 matched controls to investigate the association between the two PCMT1 polymorphisms in fetuses and the risk of NTDs in the Chinese population of Lvliang, which has low folate intake. Maternal plasma folate and Hcy levels were also measured, and the interaction between fetal PCMT1 gene status and maternal folate metabolites was assessed. Maternal plasma folate concentrations in the NTD group were lower than in controls (10.23 vs. 13.08 nmol/L, adjusted P = 0.059), and Hcy concentrations were significantly higher (14.46 vs. 11.65 μmol/L, adjusted P = 0.026). Fetuses carrying the rs4816 AG + GG genotype, combined with higher maternal plasma Hcy, had a 6.46-fold (95 % CI 1.15-36.46) increased risk of anencephaly. The results of this study imply that the fetal PCMT1 rs4816 polymorphism may play only a weak role in NTD formation and that gene-environment interactions might be more significant.

Systems biological approach to investigate the lack of familial link between Down's Syndrome & Neural Tube Disorders

Systems Biology involves the study of the interactions of biological systems and ultimately their functions. Down's syndrome (DS) is one of the most common genetic disorders which are caused by complete, or occasionally partial, triplication of chromosome 21, characterized by cognitive and language dysfunction coupled with sensory and neuromotor deficits. Neural Tube Disorders (NTDs) are a group of congenital malformations of the central nervous system and neighboring structures related to defective neural tube closure during the first trimester of pregnancy usually occurring between days 18-29 of gestation. Several studies in the past have provided considerable evidence that abnormal folate and methyl metabolism are associated with onset of DS & NTDs. There is a possible common etiological pathway for both NTDs and Down's syndrome. But, various research studies over the years have indicated very little evidence for familial link between the two disorders. Our research aimed at the gene expression profiling of microarray datasets pertaining to the two disorders to identify genes whose expression levels are significantly altered in these conditions. The genes which were 1.5 fold unregulated and having a p-value <0.05 were filtered out and gene interaction network were constructed for both NTDs and DS. The top ranked dense clique for both the disorders were recognized and over representation analysis was carried out for each of the constituent genes. The comprehensive manual analysis of these genes yields a hypothetical understanding of the lack of familial link between DS and NTDs. There were no genes involved with folic acid present in the dense cliques. Only - CBL, EGFR genes were commonly present, which makes the allelic variants of these genes - good candidates for future studies regarding the familial link between DS and NTDs.

ABBREVIATIONS

NTD - Neural Tube Disorders, DS - Down's Syndrome, MTHFR - Methylenetetrahydrofolate reductase, MTRR- 5 - methyltetrahydrofolate-homocysteine methyltransferase reductase.

Methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism and risk of preeclampsia: an updated meta-analysis based on 51 studies

BACKGROUND AND AIMS

The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been considered to be associated with preeclampsia (PE), but the results from previous studies were conflicting. The present study aimed at investigating the frequency of preeclampsia according to the distribution polymorphism using a meta-analysis on the published studies.

METHODS

The English and Chinese databases were searched to identify eligible studies published in English before August 2012. Data were extracted using standardized methods. The association was assessed by odds ratio (OR) with 95% confidence intervals (CI). Begg's test was used to measure publication bias.

RESULTS

A total of 51 case-control studies containing 6,403 patients and 11,346 controls were involved in this meta-analysis. Significant associations were detected between MTHFR C677T polymorphism and risk of PE in the overall population for TT vs. CC (OR = 1.280, 95% CI: 1.074-1.525), recessive model (OR = 1.264, 95% CI: 1.067-1.303), and dominant genetic model (OR = 1.174, 95% CI: 1.057-1.303); in Caucasian population for dominant model (OR = 1.136, 95% CI: 1.022-1.263), and in East Asia population for TT vs. CC (OR = 2.199, 95% CI: 1.366-3.924) CT vs. CC (OR = 1.453, 95% CI: 1.001-2.109), recessive model (OR = 1.742, 95% CI: 1.202-2.525), and dominant model (OR = 1.783, 95% CI: 1.271-2.501). Conversely, no associations were detected in Latin America, South Asia, and Africa populations.

CONCLUSIONS

Results of the meta-analysis suggest that the MTHFR C677T polymorphism was associated with risk of PE in overall, Caucasian, and East Asia populations. Nevertheless, the results for Latino, East Asians, South Asians and Africans should be interpreted with caution due to the small sample size.

Neural tube defects and maternal intake of micronutrients related to one-carbon metabolism or antioxidant activity

BACKGROUND

Maternal nutritional status has been evaluated to clarify its role in development of neural tube defects (NTDs). Maternal folate intake during pregnancy has been closely evaluated for its association with NTDs. The study objective was to examine associations between NTDs and other dietary periconceptional micronutrient intake, particularly nutrients involved in one-carbon metabolism or antioxidant activity.

METHODS

Using data from the National Birth Defects Prevention Study, 1997-2005, logistic regression models were used to estimate the relative risk of NTDs based on maternal micronutrient intake.

RESULTS

Results were stratified according to folic acid supplement use, race/ethnicity, and maternal body mass index. Analyses included 954 cases (300 with anencephaly, 654 with spina bifida) and 6268 controls. Higher intakes of folate, thiamin, betaine, iron, and vitamin A were associated with decreased risk of anencephaly among some ethnic and clinical groups. In some groups, higher intakes of thiamin, riboflavin, vitamin B(6) , vitamin C, vitamin E, niacin, and retinol were associated with decreased risk of spina bifida.

CONCLUSION

In addition to folic acid, other micronutrients, including thiamin, betaine, riboflavin, vitamin B(6) , vitamin C, vitamin E, niacin, iron, retinol, and vitamin A, may decrease the risk of NTD occurrence. Birth Defects Research (Part A) 2012. © 2012 Wiley Periodicals, Inc.

Mouse as a model for multifactorial inheritance of neural tube defects

Neural tube defects (NTDs) such as spina bifida and anencephaly are some of the most common structural birth defects found in humans. These defects occur due to failures of neurulation, a process where the flat neural plate rolls into a tube. In spite of their prevalence, the causes of NTDs are poorly understood. The multifactorial threshold model best describes the pattern of inheritance of NTDs where multiple undefined gene variants interact with environmental factors to cause an NTD. To date, mouse models have implicated a multitude of genes as required for neurulation, providing a mechanistic understanding of the cellular and molecular pathways that control neurulation. However, the majority of these mouse models exhibit NTDs with a Mendelian pattern of inheritance. Still, many examples of multifactorial inheritance have been demonstrated in mouse models of NTDs. These include null and hypomorphic alleles of neurulation genes that interact in a complex fashion with other genetic mutations or environmental factors to cause NTDs. These models have implicated several genes and pathways for testing as candidates for the genetic basis of NTDs in humans, resulting in identification of putative pathogenic mutations in some patients. Mouse models also provide an experimental paradigm to gain a mechanistic understanding of the environmental factors that influence NTD occurrence, such as folic acid and maternal diabetes, and have led to the discovery of additional preventative nutritional supplements such as inositol. This review provides examples of how multifactorial inheritance of NTDs can be modeled in the mouse.

Maternal folate status in early pregnancy and child emotional and behavioral problems: the Generation R Study

BACKGROUND

Maternal prenatal folate status has been linked to neurodevelopmental disorders, but the association with child emotional and behavioral problems is unclear.

OBJECTIVES

We assessed the association of maternal folate status during pregnancy with child emotional and behavioral problems. Also, we examined whether any association between folate status and child problems is a consequence of maternal folic acid supplement use or variation in maternal MTHFR genotype.

DESIGN

Within a population-based cohort, we measured maternal plasma folate concentrations in early pregnancy and assessed folic acid supplement use by questionnaire. Mothers of European descent were genotyped for the MTHFR 677 C→T polymorphism. Child emotional and behavioral problems were assessed with the Child Behavior Checklist at 3 y in 3209 children.

RESULTS

Children of mothers with prenatal folate deficiency were at higher risk of emotional problems (OR: 1.57; 95% CI: 1.03, 2.38) but not behavioral problems (OR: 1.00; 95% CI: 0.64, 1.56) after adjustment for confounders. A higher risk of emotional problems was also found in children whose mothers started using folic acid supplements late or did not use supplements at all (OR: 1.45; 95% CI: 1.14, 1.84) than in children whose mothers started periconceptionally. However, low plasma folate concentrations only partly explained this association (OR: 1.38; 95% CI: 1.08, 1.78). Although related to plasma folate concentrations, maternal MTHFR genotype did not explain the association of folate status with offspring emotional problems.

CONCLUSION

Low maternal folate status during early pregnancy is associated with a higher risk of emotional problems in the offspring.

Homocysteine exposure affects early hemodynamic parameters of embryonic chicken heart function

Maternal hyperhomocysteinemia has been associated with an increased risk of newborns with a congenital heart defect. This has been substantiated in the chicken embryo, as congenital heart defects have been induced after homocysteine treatment. Comparable heart defects are observed in venous clipping studies, a model of altered embryonic blood flow. Because of this overlap in heart defects, our aim was to test the hypothesis that homocysteine would cause alterations in embryonic heart function that precede the structural malformations previously described. Therefore, Doppler flow velocity waveforms were recorded in both primitive ventricles and the outflow tract of the embryonic heart of homocysteine treated and control chicken embryos at embryonic day 3.5. Homocysteine treatment consisted of 50 μL 0.05 M L-homocysteine thiolactone at 24, 48, and 72 hr. Homocysteine-treated embryos displayed significantly lower mean heart rates of 134 (SD 22) bpm, compared to 150 (14) bpm in control embryos. Homocysteine treatment caused an inhibiting effect on hemodynamic parameters, and altered heart function was presented by a shift in the proportions of the different wave times in percentage of total cycle time. Homocysteine induces changes in hemodynamic parameters of early embryonic chicken heart function. These changes may precede morphological changes and contribute to the development of CHD defects through alterations in shear stress and shear stress related genes, as seen before in venous clipping studies.

Solute Carrier Family 19, member 1 (SLC19A1) polymorphisms (-43T>C, 80G>A, and 696C>T), and haplotypes in idiopathic recurrent spontaneous abortion in a Korean population

The objective was to investigate the association between idiopathic recurrent spontaneous abortion (RSA) and 3 SLC19A1 polymorphisms (-43T>C, 80G>A, and 696C>T). DNA from 269 patients with RSA and 125 controls were genotyped for the 3 SLC19A1 single nucleotide polymorphisms (SNPs) by polymerase chain reaction-restriction fragment length polymorphism. Homocysteine and folate levels of 100 patients with RSA were available for analysis. The combination genotypes of SLC19A1 -43TC/80GG, -43TC/80AA, and -43CC/80GA; 80GA/696TT, 80AA/696CC; and -43TC/696CC were less frequent in patients with RSA compared to controls (P < .05 for each). The -43C/80A/696 T and -43T/80G/696C haplotypes were more frequent in patients than controls, whereas -43T/80A/696C, -43C/80A/696C, -43C/80G/696C, -43C/80G/696T, and -43T/80G/696T haplotypes were less frequent in patients (P < .05 for each). The -43T/80G and 80A/696T haplotypes were more frequent in patients, while -43T/80A, -43C/80G, 80A/696C, 80G/696T, and -43C/696C haplotypes occurred less frequently in patients (P < .05 for each). The associations between idiopathic RSA occurrence and SLC19A1 -43T>C/80G>A/696C>T polymorphisms were identified and can be developed as biomarkers for RSA risk.

Maternal homocysteine and small-for-gestational-age offspring: systematic review and meta-analysis

BACKGROUND

Growth retardation in utero leading to small-for-gestational-age (SGA) newborns is associated with increased neonatal morbidity and mortality and with lifelong consequences such as poor cognitive function and cardiovascular diseases. Maternal total homocysteine (tHcy) concentrations have been linked to a wide range of adverse pregnancy outcomes and could possibly influence birth weight.

OBJECTIVE

We performed a systematic review of and meta-analysis on the association of maternal tHcy and birth weight.

DESIGN

A literature search of English, German, and French publications with the use of the PubMed database (January 1966-July 2010) found 78 abstracts. Search terms were as follows: homocysteine AND (birth weight OR small for gestational age OR intrauterine growth retardation). Studies were eligible if information on maternal tHcy and birth weight and the possible association between maternal tHcy and birth weight was available. Effect size estimates were converted to ORs as estimates of the RR of a woman to deliver SGA offspring when maternal tHcy exceeded the 90th percentile.

RESULTS

The search yielded 19 studies for analysis, consisting of 21,326 individuals. Pooled analysis resulted in a crude OR of 1.25 (95% CI: 1.09, 1.44). When this estimate was expressed as a linear effect, it corresponded to a decrease in birth weight of 31 g (95% CI: -13, -51 g) for a 1-SD increase in maternal tHcy.

CONCLUSIONS

Higher maternal tHcy concentrations are associated with a small increased risk for SGA offspring. The small estimated birth weight difference might be of little clinical relevance for the individual newborn; however, it could be of greater importance at a population level.

A genetic signature of spina bifida risk from pathway-informed comprehensive gene-variant analysis

Despite compelling epidemiological evidence that folic acid supplements reduce the frequency of neural tube defects (NTDs) in newborns, common variant association studies with folate metabolism genes have failed to explain the majority of NTD risk. The contribution of rare alleles as well as genetic interactions within the folate pathway have not been extensively studied in the context of NTDs. Thus, we sequenced the exons in 31 folate-related genes in a 480-member NTD case-control population to identify the full spectrum of allelic variation and determine whether rare alleles or obvious genetic interactions within this pathway affect NTD risk. We constructed a pathway model, predetermined independent of the data, which grouped genes into coherent sets reflecting the distinct metabolic compartments in the folate/one-carbon pathway (purine synthesis, pyrimidine synthesis, and homocysteine recycling to methionine). By integrating multiple variants based on these groupings, we uncovered two provocative, complex genetic risk signatures. Interestingly, these signatures differed by race/ethnicity: a Hispanic risk profile pointed to alterations in purine biosynthesis, whereas that in non-Hispanic whites implicated homocysteine metabolism. In contrast, parallel analyses that focused on individual alleles, or individual genes, as the units by which to assign risk revealed no compelling associations. These results suggest that the ability to layer pathway relationships onto clinical variant data can be uniquely informative for identifying genetic risk as well as for generating mechanistic hypotheses. Furthermore, the identification of ethnic-specific risk signatures for spina bifida resonated with epidemiological data suggesting that the underlying pathogenesis may differ between Hispanic and non-Hispanic groups.

Maternal one-carbon metabolism, MTHFR and TCN2 genotypes and neural tube defects in India

BACKGROUND

Neural tube defects (NTDs) are among the most common severe congenital malformations, representing a long-term public health burden in India. A deranged one-carbon metabolism and genes regulating this metabolism have been linked to NTDs. Vitamin B(12) deficiency is reported to be more prevalent than folate deficiency in the Indian population. We investigated the role of maternal nutritional and genetic markers related to one-carbon metabolism in the etiology of NTDs.

METHODS

We conducted a multicenter case-control study to compare plasma folate, vitamin B(12) , homocysteine and holo-transcobalamin levels, and polymorphisms in methylenetetrahydrofolate reductase (MTHFR, 677C>T, 1298A>C, 1781G>A and 236+724A>G) and transcobalamin (TCN2, 776C>G) genes, in 318 women with NTD-affected offspring (cases) and 702 women with apparently healthy offspring (controls). The samples were collected at diagnosis in cases and at delivery in controls.

RESULTS

We observed a significant association of high maternal plasma homocysteine concentrations with NTDs in the offspring (p = 0.026). There was no association of maternal folate or B(12) levels with NTDs (p > 0.05) but low maternal holo-transcobalamin predicted strong risk of NTDs in the offspring (p = 0.003). The commonly associated maternal polymorphism 677C>T in the MTHFR gene did not predict risk of NTDs in the offspring (p > 0.05) and 1298A>C and 1781G>A polymorphisms in MTHFR were protective (p = 0.024 and 0.0004 respectively). Maternal 776C>G polymorphism in TCN2 was strongly predictive of NTD in the offspring (p = 0.006).

CONCLUSION

Our study has demonstrated a possible role for maternal B(12) deficiency in the etiology of NTDs in India over and above the well-established role of folate deficiency.

The emerging role of epigenetic mechanisms in the etiology of neural tube defects

The molecular requirements for neural tube closure are complex. This is illustrated by the occurrence of neural tube defects (NTDs) in many genetic mouse mutants, which implicate a variety of genes, pathways and cellular functions. NTDs are also prevalent birth defects in humans, affecting around 1 per 1000 pregnancies worldwide. In humans the causation is thought to involve the interplay of fetal genes and the effect of environmental factors. Recent studies on the aetiology of human NTDs, as well as analysis of mouse models, have raised the question of the possible involvement of epigenetic factors in determining susceptibility. A consideration of potential causative factors in human NTDs must now include both alterations in the regulation of gene expression, through mutation of promoter or regulatory elements, and the additional analysis of epigenetic regulation. Alterations in the epigenetic status can be directly modified by various environmental insults or maternal dietary factors.

Maternal periconceptional factors affect the risk of spina bifida-affected pregnancies: an Italian case-control study

PURPOSE

Neural tube defects, including spina bifida and anencephaly, are the second most common birth defects with an incidence in Italy of 0.4-1/1,000. Information on factors playing a role in the pathogenesis of spina bifida is based on populations with different exposures, lifestyle, social and cultural habits compared to Italian people. Our objective was to fill this gap by using data from a case-control interview study carried out at the G. Gaslini Children's Hospital, Genoa, from 2000 to 2008.

METHODS

We surveyed questionnaires from 133 case mothers and 273 control women providing information on periconceptional risk factors. Univariate and multivariate logistic regression analyses were used to estimate risks by odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

Univariate results suggest that birth order, low maternal educational level, age, smoking habits, alcohol consumption, high caffeine intake, lack of folate supplementation, low and high calorie diet, occasional consumption of fruit and vegetables, high emotional stress, and environmental pollution are associated with an increased spina bifida risk. Nevertheless, high caffeine intake (OR = 10.82; 95% CI, 3.78-31), low calorie diet (OR = 5.15; 95%CI, 1.79-14), occasional consumption of fruit and vegetables (OR = 3.38; 95% CI, 1.67-6.82), alcohol consumption (OR = 3.05; 95% CI, 1.24-7.50) and, above all, lack of folate supplementation at any time of pregnancy (OR = 20.54; 95% CI, 5.41-77) mainly determined spina bifida risk in the multivariate analysis.

CONCLUSION

Our findings point out that a common underlying mechanism, a disturbed folate/homocysteine metabolism, may be causative for the burden of spina bifida in the Italian population.

Development of an animal model for chronic mild hyperhomocysteinemia and its response to oxidative damage

The purpose of this study was to develop a chronic chemically induced model of mild hyperhomocysteinemia in adult rats. We produced levels of Hcy in the blood (30μM), comparable to those considered a risk factor for the development of neurological and cardiovascular diseases, by injecting homocysteine subcutaneously (0.03μmol/g of body weight) twice a day, from the 30th to the 60th postpartum day. Controls received saline in the same volumes. Using this model, we evaluated the effect of chronic administration of homocysteine on redox status in the blood and cerebral cortex of adult rats. Reactive oxygen species and thiobarbituric acid reactive substances were significantly increased in the plasma and cerebral cortex, while nitrite levels were reduced in the cerebral cortex, but not in the plasma, of rats subjected to chronic mild hyperhomocysteinemia. Homocysteine was also seen to disrupt enzymatic and non-enzymatic antioxidant defenses in the blood and cerebral cortex of rats. Since experimental animal models are useful for understanding the pathophysiology of human diseases, the present model of mild hyperhomocysteinemia may be useful for the investigation of additional mechanisms involved in tissue alterations caused by homocysteine.

Homocysteine in pregnancy

The aim of this review is to evaluate the evidence for and against fasting plasma total homocysteine (tHcy) as a biomarker/risk factor of impaired reproductive function before and during pregnancy. Apart from nutritional and lifestyle factors, tHcy is also influenced by physiological factors specific to pregnancy such as hemodilution, increased glomerular filtration rate, and endocrinological changes. These lead to a considerable reduction under normal circumstances in tHcy by midpregnancy. Stimulating excess endogenous homocysteine production before and during pregnancy in animal experiments and adding exogenous homocysteine to cell cultures result in the impairment of reproductive and developmental processes from preconception throughout pregnancy and during subsequent development of the offspring. Different studies have confirmed that elevated tHcy is a risk factor for subfertility, congenital developmental defects, preeclampsia, and intrauterine growth retardation. There is conflicting evidence that elevated tHcy is a risk factor for miscarriage, gestational diabetes, premature rupture of the membranes, placental abruption, and offspring with Down syndrome. Prospective, sufficiently powered, studies from preconception/early pregnancy are required to determine whether tHcy is a risk factor for these pregnancy complications.

Maternal smoking, passive tobacco smoke, and neural tube defects

BACKGROUND

Although cigarette smoke is a well-established toxin and harmful to the developing embryo, the evidence for an independent effect on the occurrence of neural tube defects (NTDs) is mixed. In this study, we examined the relation between NTDs and maternal exposures to cigarette smoke, including passive smoke exposure.

METHODS

We used cases and controls from the large, multistate, population-based National Birth Defects Prevention Study. A total of 1041 NTD cases and 5862 live birth controls, delivered during 1997 to 2004, were available for analyses. Mothers were interviewed by telephone between 6 weeks and 24 months after delivery. Participation rates were 71% for NTD case mothers and 69% for control mothers.

RESULTS

Compared with nonsmokers (and also not exposed to passive cigarette smoke), mothers exposed only to passive smoke had an increased NTD odds ratio (OR, 1.7; 95% confidence interval [CI], 1.4-2.0), adjusted for race-ethnicity, and study center. There was no increased OR for mothers who actively smoked 24 or fewer cigarettes per day. Mothers who smoked 25 or more cigarettes per day had an elevated OR (OR, 1.6; 95% CI, 0.9-3.0), but the OR adjusted for race-ethnicity, and center was compatible with the null.

CONCLUSION

Results suggest that maternal exposure to passive smoke is associated with NTDs. Women who plan on becoming pregnant should minimize their exposure to passive smoke and refrain from smoking.

Serum vitamin B12 and homocysteine levels in pregnant women with neural tube defect

OBJECTIVE

The aim of the study is to investigate the importance of serum vitamin B12 levels in pregnant women with foetal neural tube defect (NTD).

STUDY DESIGN

This study consists of 31 pregnant women having fetuses with NTD. The pregnant women in the study group were selected among cases with normal folate levels. Serum vitamin B12 levels were investigated. Additionally, complete blood count, serum iron level, iron binding capacity, ferritin, folate, free T(3), free T(4), thyroid stimulating hormone and plasma homocysteine levels were measured. Control group consisted of 32 pregnant women who did not have a history of NTD in previous pregnancies and did not have fetuses with NTD in present pregnancy. NTD was diagnosed between 14th and 20th gestational age. The mean gestational age of members of control group was the same as those of NTD group.

RESULTS

There was no statistically significant difference between pregnants with NTD and control group according to number of cases with vitamin B12 deficiency.

CONCLUSION

It seems that vitamin B12 deficiency does not play a causative role in the development of foetal NTD. Monitoring maternal homocystein levels might be important in understanding the aetiologies of foetal NTD.

Role of parental folate pathway single nucleotide polymorphisms in altering the susceptibility to neural tube defects in South India

AIM

To investigate the role of four parental folate pathway single nucleotide polymorphisms (SNPs) i.e., methylene tetrahydrofolate reductase (MTHFR) 677C>T, MTHFR 1298A>C, methionine synthase reductase (MTRR) 66A>G and glutamate carboxypeptidase (GCP) II 1561C>T on susceptibility to neural tube defects (NTDs) in 50 couples with NTD offspring and 80 couples with normal pregnancy outcome.

RESULTS

Maternal MTHFR 677C-->T (odds ratio (OR): 2.69, 95% confidence interval (CI): 1.35-5.34) and parental GCP II 1561C-->T (maternal: OR: 1.89, 95% CI: 1.12-3.21 and paternal: OR: 3.23, 95% CI: 1.76-5.93) were found to be risk factors for a NTD. Both paternal and maternal GCP II T-variant alleles were found to interact with MTHFR 677T- and MTRR G-variant alleles in increasing the risk for NTD. Segregation of data based on type of defect revealed an association between maternal 677T-allele and meningomyelocele (OR: 9.00, 95% CI: 3.77-21.55, P<0.0001) and an association between parental GCP II 1561T-allele and anencephaly (maternal: OR: 2.25, 95% CI: 1.12-4.50, P<0.05 and paternal: OR: 4.26, 95% CI: 2.01-9.09, P<0.001).

CONCLUSIONS

Maternal MTHFR C677T and parental GCP II C1561T polymorphisms are associated with increased risk for NTDs. Apart from individual genetic effects, epistatic interactions were also observed.

Maternal caffeine consumption and risk of neural tube defects

BACKGROUND

Animal studies demonstrate teratogenic effects of caffeine, whereas human studies are inconclusive.

METHODS

Associations between maternal caffeine consumption and neural tube defects (NTDs) by type of NTD (anencephaly, spina bifida, or encephalocele) were examined using data from the National Birth Defects Prevention Study (NBDPS). Total average daily caffeine from coffee, tea, soda, and chocolate consumption during the year before pregnancy was estimated for 768 mothers of infants with NTDs and 4143 mothers of infants without birth defects who gave birth during 1997 through 2002. Periconceptional use of caffeine-containing medications was evaluated separately. Adjusted odds ratios (OR) and 95% confidence intervals (CI) associated with consumption of total caffeine and each caffeine source were estimated from logistic regression models.

RESULTS

Positive associations were observed between spina bifida and total caffeine consumption (OR 1.4; 95% CI: 1.1-1.9) and each caffeine source except caffeinated tea, which showed a negative association with spina bifida (OR 0.7; 95% CI: 0.6-0.9). Associations with modestly increased risk of NTDs and encephalocele were also observed. The association between caffeine consumption and anencephaly differed by maternal race/ethnicity. No dose effects were found.

CONCLUSIONS

Additional studies should confirm whether women who consume caffeine are at increased risk for pregnancies complicated by NTDs.

Choline: an essential nutrient for public health

Choline was officially recognized as an essential nutrient by the Institute of Medicine (IOM) in 1998. There is significant variation in the dietary requirement for choline that can be explained by common genetic polymorphisms. Because of its wide-ranging roles in human metabolism, from cell structure to neurotransmitter synthesis, choline-deficiency is now thought to have an impact on diseases such as liver disease, atherosclerosis, and, possibly, neurological disorders. Choline is found in a wide variety of foods. Eggs and meats are rich sources of choline in the North American diet, providing up to 430 milligrams per 100 grams. Mean choline intakes for older children, men, women, and pregnant women are far below the adequate intake level established by the IOM. Given the importance of choline in a wide range of critical functions in the human body, coupled with less-than-optimal intakes among the population, dietary guidance should be developed to encourage the intake of choline-rich foods.

Homocysteine metabolism and its relation to health and disease

Homocysteine is a metabolic intermediate in methyl group metabolism that is dependent on a number of nutritional B-vitamin cofactors. An emerging aspect of homocysteine metabolism is its relation to health and disease. Perturbations of homocysteine metabolism, particularly intracellular and subsequently circulating accumulation of homocysteine (i.e., hyperhomocysteinemia), are associated with vascular disease risk, as well as other pathologies. However, intervention with B-vitamin supplementation has been shown to successfully restore normal homocysteine concentrations, but without concomitant reductions in disease risk. Thus, the mechanistic relation between homocysteine balance and disease states, as well as the value of homocysteine management, remains an area of intense investigation.

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.