Prenatal exposure to maternal depressed mood and the MTHFR C677T variant affect SLC6A4 methylation in infants at birth

Looking beyond the DNA sequence: the relevance of DNA methylation processes for the stress-diathesis model of depression

The functioning of the hypothalamic-pituitary-adrenal (HPA) axis and serotonergic (5-HT) system are known to be intertwined with mood. Alterations in these systems are often associated with depression. However, neither are sufficient to cause depression in and of themselves. It is now becoming increasingly clear that the environment plays a crucial role, particularly, the perinatal environment. In this review, we posit that early environmental stress triggers a series of epigenetic mechanisms that adapt the genome and programme the HPA axis and 5-HT system for survival in a harsh environment. We focus on DNA methylation as it is the most stable epigenetic mark. Given that DNA methylation patterns are in large part set within the perinatal period, long-term gene expression programming by DNA methylation is especially vulnerable to environmental insults during this period. We discuss specific examples of genes in the 5-HT system (serotonin transporter) and HPA axis (glucocorticoid receptor and arginine vasopressin enhancer) whose DNA methylation state is associated with early life experience and may potentially lead to depression vulnerability. We conclude with a discussion on the relevance of studying epigenetic mechanisms in peripheral tissue as a proxy for those occurring in the human brain and suggest avenues for future research.

Role of the hypothalamic-pituitary-adrenal axis in developmental programming of health and disease

Adverse environments during the fetal and neonatal development period may permanently program physiology and metabolism, and lead to increased risk of diseases in later life. Programming of the hypothalamic-pituitary-adrenal (HPA) axis is one of the key mechanisms that contribute to altered metabolism and response to stress. Programming of the HPA axis often involves epigenetic modification of the glucocorticoid receptor (GR) gene promoter, which influences tissue-specific GR expression patterns and response to stimuli. This review summarizes the current state of research on the HPA axis and programming of health and disease in the adult, focusing on the epigenetic regulation of GR gene expression patterns in response to fetal and neonatal stress. Aberrant GR gene expression patterns in the developing brain may have a significant negative impact on protection of the immature brain against hypoxic-ischemic encephalopathy in the critical period of development during and immediately after birth.

Associations of BDNF genotype and promoter methylation with acute and long-term stroke outcomes in an East Asian cohort

Background

Brain derived neurotrophic factor (BDNF) has been shown to play an important role in poststroke recovery. BDNF secretion is influenced by genetic and epigenetic profiles. This study aimed to investigate whether BDNF val66met polymorphism and promoter methylation status were associated with outcomes at two weeks and one year after stroke.

Methods and Findings

A total of 286 patients were evaluated at the time of admission and two weeks after stroke, and 222 (78%) were followed one year later in order to evaluate consequences of stroke at both acute and chronic stages. Stroke outcomes were dichotomised into good and poor by the modified Rankin Scale. Stroke severity (National Institutes of Health Stroke Scale), physical disability (Barthel Index), and cognitive function (Mini-Mental State Examination) were measured. Associations of BDNF genotype and methylation status on stroke outcomes and assessment scale scores were investigated using logistic regression, repeated measures ANOVA and partial correlation tests. BDNF val66met polymorphism was independently associated with poor outcome at 2 weeks and at 1 year, and with worsening physical disability and cognitive function over that period. Higher BDNF promoter methylation status was independently associated with worse outcomes at 1 year, and with the worsening of physical disability and cognitive function. No significant genotype-methylation interactions were found.

Conclusions

A role for BDNF in poststroke recovery was supported, and clinical utility of BDNF genetic and epigenetic profile as prognostic biomarkers and a target for drug development was suggested.

Antenatal identification of major depressive disorder: a cohort study

OBJECTIVE

The purpose of this study was to estimate the frequency of identification of major depressive disorder by providers during prenatal care.

STUDY DESIGN

A cohort of pregnant women who were participating in a randomized controlled trial and who had received a diagnosis of major depressive disorder was examined. Women were included in the current study if prenatal clinic records were available and legible.

RESULTS

Clinical depression was noted in 56% of prenatal charts and on 24% of problem lists. Physicians and certified nurse midwives noted depression equally (P = .935); physicians more frequently noted mental health referral (23% vs 0%; P = .01), and midwives more frequently included depression on the problem list (P = .01). Recent medication use, which was stopped before conception or study participation, predicted notation of depression in the chart (P = .001).

CONCLUSION

Depression frequently is missed during pregnancy and, when identified, is underacknowledged as a problem. Women who have not recently used antidepressant medication are more likely to be missed. Better screening and acknowledgment are needed.

An unbalanced maternal diet in pregnancy associates with offspring epigenetic changes in genes controlling glucocorticoid action and foetal growth

OBJECTIVE

In epidemiological studies, adverse early-life conditions associate with subsequent cardiometabolic disease. Hypothesized causes include maternal malnutrition, foetal glucocorticoid overexposure and reduced growth factors. Animal studies suggest a role for epigenetic processes in maintaining early-life effects into adulthood, but human relevance is unknown. We aimed to investigate relationships between an unbalanced maternal diet in pregnancy, neonatal and adult anthropometric variables with methylation at key genes controlling tissue glucocorticoid action and foetal growth.

DESIGN

We studied 34 individuals aged 40 from the Motherwell cohort study whose mothers ate an unbalanced diet in pregnancy, previously linked with elevated blood pressure and cortisol in adult offspring.

MEASUREMENTS

DNA methylation at 11β-hydroxysteroid dehydrogenase type 2 (HSD2), glucocorticoid receptor (GR) and insulin-like growth factor 2 (IGF2) was measured by pyrosequencing on buffy coat DNA.

RESULTS

Methylation at specific CpGs in the HSD2 promoter and at one of the IGF2 differentially methylated regions (H19 ICR) correlated with neonatal anthropometric variables. CpG methylation within HSD2, GR and H19 ICR was positively associated with increased adiposity and blood pressure in adulthood. Methylation at GR (exon 1F) was increased in offspring of mothers with the most unbalanced diets in pregnancy.

CONCLUSIONS

Alterations in DNA methylation at genes important in regulating circulating cortisol levels, tissue glucocorticoid action, blood pressure and foetal growth are present in adulthood in association with both early-life parameters and cardiometabolic risk factors. The data indicate a persisting epigenetic link between early-life maternal diet and/or foetal growth and cardiovascular disease risk in humans.

Linking prenatal maternal adversity to developmental outcomes in infants: the role of epigenetic pathways

Prenatal exposure to maternal stress, anxiety, and depression can have lasting effects on infant development with risk of psychopathology. Although the impact of prenatal maternal distress has been well documented, the potential mechanisms through which maternal psychosocial variables shape development have yet to be fully elucidated. Advances in molecular biology have highlighted the role of epigenetic mechanisms in regulating gene activity, neurobiology, and behavior and the potential role of environmentally induced epigenetic variation in linking early life exposures to long-term biobehavioral outcomes. In this article, we discuss evidence illustrating the association between maternal prenatal distress and both fetal and infant developmental trajectories and the potential role of epigenetic mechanisms in mediating these effects. Postnatal experiences may have a critical moderating influence on prenatal effects, and we review findings illustrating prenatal-postnatal interplay and the developmental and epigenetic consequences of postnatal mother-infant interactions. The in utero environment is regulated by placental function and there is emerging evidence that the placenta is highly susceptible to maternal distress and a target of epigenetic dysregulation. Integrating studies of prenatal exposures, placental function, and postnatal maternal care with the exploration of epigenetic mechanisms may provide novel insights into the pathophysiology induced by maternal distress.

Biological memory of childhood maltreatment: current knowledge and recommendations for future research

Child maltreatment (CM) not only has detrimental and lifelong psychological consequences, but also can lead to lasting alterations in core physiological systems--a biological memory of CM. Furthermore, some of these alterations might even be transmitted to the next generation. This article describes current knowledge about the effects of CM on the stress system (i.e., the hypothalamus-pituitary-adrenal axis), on cellular aging (i.e., telomere length and telomerase activity), and on the immune system. Furthermore, we want to initiate research on the question of transmission of the described physiological alterations subsequent to CM to the next generation--possibly through epigenetic imprinting. As diverse neurobiological factors and epigenetics are closely linked, these different research fields should join forces to gain a deeper understanding of the biological determinants and sequelae of CM and its transmission.

Epigenetic alterations related to early-life stressful events

Objective: Early stress events severely impact brain and behaviour. From a neurobiological point of view early stress influences neuroanatomical structures and is associated with a dysregulation of the hypothalamic-pituitary-adrenal axis. The objective of this article is to review the epigenetic alterations implicated in brain adaptation to early stress events.

Method: A review of empirical research of epigenetic alterations associated to early stress events was performed.

Results: Neuroanatomic and epigenetic alterations have been observed after early stress events. Epigenetics alterations include DNA methylation, histones modifications and microRNA (miRNA) expression. The most studied is largely the former, affecting genes involved in neuroendocrine, neurotransmission and neuroplasticity regulation after early stress exposition. It includes glucocorticoid receptor, FK506-binding protein 5, arginine vasopressin, oestrogen receptor alpha, 5-hydroxy-tryptamine transporter and brain-derived neurotrophic factor.

Conclusion: Epigenetic regulation is critical in the interplay between nature and nurture. Alterations in the DNA methylation as well as histones modifications and miRNA expression patterns could explain abnormal behaviours secondary to early stress events.

Glucocorticoids as mediators of developmental programming effects

Epidemiological evidence suggests that exposure to an adverse environment in early life is associated with an increased risk of cardio-metabolic and behavioral disorders in adulthood, a phenomenon termed 'early life programming'. One major hypothesis for early life programming is fetal glucocorticoid overexposure. In animal studies, prenatal glucocorticoid excess as a consequence of maternal stress or through exogenous administration to the mother or fetus is associated with programming effects on cardiovascular and metabolic systems and on the brain. These effects can be transmitted to subsequent generations. Studies in humans provide some evidence that prenatal glucocorticoid exposure may exert similar programming effects on glucose/insulin homeostasis, blood pressure and neurodevelopment. The mechanisms by which glucocorticoids mediate these effects are unclear but may include a role for epigenetic modifications. This review discusses the evidence for glucocorticoid programming in animal models and in humans.

Environmental stress affects DNA methylation of a CpG rich promoter region of serotonin transporter gene in a nurse cohort

BACKGROUND

Shift-working nurses are exposed to a stressful work environment, which puts them at an increased risk for burnout and depression. We explored the effect of environmental stress on serotonin transporter gene (SLC6A4) promoter methylation among nurses from high and low work stress environments.

METHODOLOGY

Using bisulfite sequencing, we investigated the methylation status of five CpG residues of a CpG-rich region in the promoter of SLC6A4 by comparing female shift working nurses from a high work stress environment (n = 24) to low work stress environment (n = 25). We also analyzed the association of 5-HTTLPR polymorphism at 5' end of SLC6A4. Work stress was assessed by the Karasek's Model and possible signs of burnout or depression were measured by the Maslach Burnout Index General Survey and Beck Depression Index. Methylation levels were assessed by bisulfite sequencing of DNA extracted from peripheral blood leucocytes. Restriction enzyme treatment followed by standard PCR was used to identify 5-HTTLPR genotypes.

PRINCIPAL FINDINGS

We found that nurses in the high stress environment had significantly lower promoter methylation levels at all five CpG residues compared to nurses in the low stress environment (p<0.01). There was no significant interaction of 5-HTTLPR genotype and work stress with methylation (p = 0.58). In unadjusted (bivariate) analysis, burnout was not significantly associated to methylation levels. However, when mutually adjusted for both, burnout and work stress were significant contributors (p = 0.038 and p<0.0001 respectively) to methylation levels.

CONCLUSIONS

Our findings show that environmental stress is concurrent with decreased methylation of the SLC6A4 promoter. This may lead to increased transcriptional activity of the gene, increased reuptake of serotonin from synaptic clefts, and termination of the activity of serotonin. This could present a possible coping mechanism for environmental stress in humans that could eventually increase risk for disturbed functional capability and experience of depressed mood in long-term stress.

Fetal serotonin signaling: setting pathways for early childhood development and behavior

Finely tuning levels of the key neurotransmitter serotonin (5-hydroxytryptamine [5-HT]) during early life is essential for brain development and setting pathways for health and disorder across the early life span. Given the central role of 5-HT in brain development, regulation of mood, stress reactivity, and risk for psychiatric disorders, alterations in 5-HT signaling early in life have critical implications for behavior and mental health in childhood and adolescence. This article reviews the developmental consequences of two key influences that alter fetal 5-HT signaling: (1) in utero exposure to 5-HT reuptake inhibitor antidepressants, and (2) genetic variations in the 5-HT transporter gene (SLC6A4). The consequences of altered prenatal 5-HT signaling vary greatly, and developmental outcomes depend on an ongoing interplay between biological (genetic/epigenetic variations), experiential (prenatal drug or maternal mood exposure), and contextual (postnatal social environment) variables. Emerging evidence suggests both exposure to 5-HT reuptake inhibitors and genetic variations that affect 5-HT signaling may increase sensitivity to negative social contexts for some individuals, whereas for others, they may confer sensitivity to positive life circumstances. In this sense, factors that change central 5-HT levels may function less like influences that predict "vulnerability," but rather act like "plasticity factors." Understanding the impact of early changes in serotonergic programming offers critical insights that might explain patterns of individual differences in developmental risk and resilience.

DNA methylation analysis of the angiotensin converting enzyme (ACE) gene in major depression

BACKGROUND

The angiotensin converting enzyme (ACE) has been repeatedly discussed as susceptibility factor for major depression (MD) and the bi-directional relation between MD and cardiovascular disorders (CVD). In this context, functional polymorphisms of the ACE gene have been linked to depression, to antidepressant treatment response, to ACE serum concentrations, as well as to hypertension, myocardial infarction and CVD risk markers. The mostly investigated ACE Ins/Del polymorphism accounts for ~40%-50% of the ACE serum concentration variance, the remaining half is probably determined by other genetic, environmental or epigenetic factors, but these are poorly understood.

MATERIALS AND METHODS

The main aim of the present study was the analysis of the DNA methylation pattern in the regulatory region of the ACE gene in peripheral leukocytes of 81 MD patients and 81 healthy controls.

RESULTS

We detected intensive DNA methylation within a recently described, functional important region of the ACE gene promoter including hypermethylation in depressed patients (p = 0.008) and a significant inverse correlation between the ACE serum concentration and ACE promoter methylation frequency in the total sample (p = 0.02). Furthermore, a significant inverse correlation between the concentrations of the inflammatory CVD risk markers ICAM-1, E-selectin and P-selectin and the degree of ACE promoter methylation in MD patients could be demonstrated (p = 0.01 - 0.04).

CONCLUSION

The results of the present study suggest that aberrations in ACE promoter DNA methylation may be an underlying cause of MD and probably a common pathogenic factor for the bi-directional relationship between MD and cardiovascular disorders.

Depression in pregnancy, infant birth weight and DNA methylation of imprint regulatory elements

Depressed mood in pregnancy has been linked to low birth weight (LBW, < 2,500 g), a risk factor for adult-onset chronic diseases in offspring. We examined maternal depressed mood in relation to birth weight and evaluated the role of DNA methylation at regulatory sequences of imprinted genes in this association. We measured depressed mood among 922 pregnant women using the CES-D scale and obtained birth weight data from hospital records. Using bisulfite pyrosequencing of cord blood DNA from 508 infants, we measured methylation at differentially methylated regions (DMRs) regulating imprinted genes IGF2/H19, DLK1/MEG3, MEST, PEG3, PEG10/SGCE, NNAT and PLAGL1. Multiple regression models were used to examine the relationship between depressed mood, birth weight and DMR methylation levels. Depressed mood was associated with a more that 3-fold higher risk of LBW, after adjusting for delivery mode, parity, education, cigarette smoking, folic acid use and preterm birth. The association may be more pronounced in offspring of black women and female infants. Compared with infants of women without depressed mood, infants born to women with severe depressed mood had a 2.4% higher methylation at the MEG3 DMR. Whereas LBW infants had 1.6% lower methylation at the IGF2 DMR, high birth weight (> 4,500 g) infants had 5.9% higher methylation at the PLAGL1 DMR compared with normal birth weight infants. Our findings confirm that severe maternal depressed mood in pregnancy is associated with LBW, and that MEG3 and IGF2 plasticity may play important roles.

Stress-related programming of autonomic imbalance: role in allergy and asthma

Evidence linking psychological stress to allergy has grown with our increased understanding of the natural history and pathophysiology of these disorders and the neurobiology of stress vulnerability. However, the specific pathways that increase vulnerability to developing allergy and associated disorders remain to be elucidated. Autonomic nervous system functioning (autonomic balance) has been implicated in allergy for some time albeit links between autonomic balance and immune function in early development have been under studied. Starting in utero, stress may influence the programming of brain neurotransmitter systems, sympathetic and parasympathetic nervous system functioning, and the hypothalamic-pituitary-adrenal axis, which in turn may alter neural regulation of immune function. Epigenetic dysregulation of gene expression may be a fundamental mechanism for programming of early neural-immune processes.

Peripheral SLC6A4 DNA methylation is associated with in vivo measures of human brain serotonin synthesis and childhood physical aggression

The main challenge in addressing the role of DNA methylation in human behaviour is the fact that the brain is inaccessible to epigenetic analysis in living humans. Using positron emission tomography (PET) measures of brain serotonin (5-HT) synthesis, we found in a longitudinal sample that adult males with high childhood-limited aggression (C-LHPA) had lower in vivo 5-HT synthesis in the orbitofrontal cortex (OBFC). Here we hypothesized that 5-HT alterations associated with childhood aggression were linked to differential DNA methylation of critical genes in the 5-HT pathway and these changes were also detectable in peripheral white blood cells. Using pyrosequencing, we determined the state of DNA methylation of SLC6A4 promoter in T cells and monocytes isolated from blood of cohort members (N = 25) who underwent a PET scan, and we examined whether methylation status in the blood is associated with in vivo brain 5-HT synthesis. Higher levels of methylation were observed in both T cells and monocytes at specific CpG sites in the C-LHPA group. DNA methylation of SLC6A4 in monocytes appears to be associated more reliably with group membership than T cells. In both cell types the methylation state of these CpGs was associated with lower in vivo measures of brain 5-HT synthesis in the left and right lateral OBFC (N = 20) where lower 5-HT synthesis in C-LHPA group was observed. Furthermore, in vitro methylation of the SLC6A4 promoter in a luciferase reporter construct suppresses its transcriptional activity supporting a functional role of DNA methylation in SLC6A4 promoter regulation. These findings indicate that state of SLC6A4 promoter methylation is altered in peripheral white blood cells of individuals with physical aggression during childhood. This supports the relevance of peripheral DNA methylation for brain function and suggests that peripheral SLC6A4 DNA methylation could be a marker of central 5-HT function.

The secret language of destiny: stress imprinting and transgenerational origins of disease

Epigenetic regulation modulates gene expression without altering the DNA sequence to facilitate rapid adjustments to dynamically changing environmental conditions. The formation of an epigenetic memory allows passing on this information to subsequent generations. Here we propose that epigenetic memories formed by adverse environmental conditions and stress represent a critical determinant of health and disease in the F3 generation and beyond. Transgenerational programming of epigenetic regulation may represent a key to understand adult-onset complex disease pathogenesis and cumulative effects of life span and familial disease etiology. Ultimately, the mechanisms of generating an epigenetic memory may become of potentially promising diagnostic and therapeutic relevance due to their reversible nature. Exploring the role of environmental factors, such as stress, in causing variations in epigenetic profiles may lead to new avenues of personalized, preventive medicine based on epigenetic signatures and interventions.

Epigenetic regulation of the BDNF gene: implications for psychiatric disorders

Abnormal brain-derived neurotrophic factor (BDNF) signaling seems to have a central role in the course and development of various neurological and psychiatric disorders. In addition, positive effects of psychotropic drugs are known to activate BDNF-mediated signaling. Although the BDNF gene has been associated with several diseases, molecular mechanisms other than functional genetic variations can impact on the regulation of BDNF gene expression and lead to disturbed BDNF signaling and associated pathology. Thus, epigenetic modifications, representing key mechanisms by which environmental factors induce enduring changes in gene expression, are suspected to participate in the onset of various psychiatric disorders. More specifically, various environmental factors, particularly when occurring during development, have been claimed to produce long-lasting epigenetic changes at the BDNF gene, thereby affecting availability and function of the BDNF protein. Such stabile imprints on the BDNF gene might explain, at least in part, the delayed efficacy of treatments as well as the high degree of relapses observed in psychiatric disorders. Moreover, BDNF gene has a complex structure displaying differential exon regulation and usage, suggesting a subcellular- and brain region-specific distribution. As such, developing drugs that modify epigenetic regulation at specific BDNF exons represents a promising strategy for the treatment of psychiatric disorders. Here, we present an overview of the current literature on epigenetic modifications at the BDNF locus in psychiatric disorders and related animal models.

DNA methylation in neonates born to women receiving psychiatric care

Prenatal exposure both to maternal psychiatric illness and psychiatric medication has been linked with adverse child outcomes that affect physiological, emotional and psychiatric development. Studies suggest that epigenetic mechanisms, such as DNA methylation, may facilitate these effects. In this report, we explore the association between maternal psychiatric illness and treatment during pregnancy and neonatal DNA methylation patterns in a prospectively-characterized clinical cohort of 201 dyads. Associations between the percent of umbilical cord blood DNA methylated at 27,578 CpG sites and maternal psychiatric diagnosis, symptoms and antidepressant use were evaluated by fitting a separate linear mixed effects model for each CpG site. There were no significant changes in neonatal DNA methylation attributable to maternal psychiatric diagnosis or depressive symptoms during pregnancy. Exposure to an antidepressant medication was associated with differential methylation of CpG sites in TNFRSF21 and CHRNA2 (false discovery rate < 0.05), but the average difference in methylation for both CpG sites was less than 3% between each group. The results were not specific to type of antidepressant or duration of the exposure. This study suggests that there are no large effects of maternal psychiatric illness, depressive symptoms or prenatal exposure to antidepressants on neonatal DNA methylation. Delineation of the influence of maternal psychiatric illness and pharmacological exposures on the developing fetuses has critical implications for clinical care during pregnancy.

Neonatal abstinence syndrome

PURPOSE OF REVIEW

This review will discuss the complex nature of maternal and other factors that can affect the infant's display of neonatal abstinence syndrome (NAS), clinical presentation and treatment of NAS, and the impact of recent findings on future directions for research.

RECENT FINDINGS

NAS has traditionally been described as a constellation of signs/symptoms displayed by the neonate upon withdrawal of gestational opioid exposure; however, recent research has advanced our understanding of this disorder. Other psychoactive substances, such as increasingly prescribed serotonin reuptake inhibitors, may produce an independent or synergistic discontinuation syndrome. The wide variability in NAS presentation has generated interest in the interplay of prenatal and postnatal environmental and genetic factors that may moderate or mediate its expression. Finally, recent advances in the treatment of opioid-dependent pregnant women have suggested buprenorphine as an alternative treatment to methadone during pregnancy, largely due to reduced NAS severity in exposed neonates.

SUMMARY

Physicians should be aware of the complexity of the maternal, fetal, and infant factors that combine to create the infant's display of NAS, and incorporate these aspects into comprehensive assessment and care of the dyad. Further research regarding the pathophysiology and treatment of NAS is warranted.

Genetic and non-genetic influences during pregnancy on infant global and site specific DNA methylation: role for folate gene variants and vitamin B12

Inter-individual variation in patterns of DNA methylation at birth can be explained by the influence of environmental, genetic and stochastic factors. This study investigates the genetic and non-genetic determinants of variation in DNA methylation in human infants. Given its central role in provision of methyl groups for DNA methylation, this study focuses on aspects of folate metabolism. Global (LUMA) and gene specific (IGF2, ZNT5, IGFBP3) DNA methylation were quantified in 430 infants by Pyrosequencing®. Seven polymorphisms in 6 genes (MTHFR, MTRR, FOLH1, CβS, RFC1, SHMT) involved in folate absorption and metabolism were analysed in DNA from both infants and mothers. Red blood cell folate and serum vitamin B₁₂ concentrations were measured as indices of vitamin status. Relationships between DNA methylation patterns and several covariates viz. sex, gestation length, maternal and infant red cell folate, maternal and infant serum vitamin B₁₂, maternal age, smoking and genotype were tested. Length of gestation correlated positively with IGF2 methylation (rho = 0.11, p = 0.032) and inversely with ZNT5 methylation (rho = −0.13, p = 0.017). Methylation of the IGFBP3 locus correlated inversely with infant vitamin B₁₂ concentration (rho = −0.16, p = 0.007), whilst global DNA methylation correlated inversely with maternal vitamin B₁₂ concentrations (rho = 0.18, p = 0.044). Analysis of common genetic variants in folate pathway genes highlighted several associations including infant MTRR 66G>A genotype with DNA methylation (χ² = 8.82, p = 0.003) and maternal MTHFR 677C>T genotype with IGF2 methylation (χ² = 2.77, p = 0.006). These data support the hypothesis that both environmental and genetic factors involved in one-carbon metabolism influence DNA methylation in infants. Specifically, the findings highlight the importance of vitamin B₁₂ status, infant MTRR genotype and maternal MTHFR genotype, all of which may influence the supply of methyl groups for DNA methylation. In addition, gestational length appears to be an important determinant of infant DNA methylation patterns.

Cardiometabolic risk and the MTHFR C677T variant in children treated with second-generation antipsychotics

Second-generation antipsychotics (SGAs) are increasingly being used to treat children with a variety of psychiatric illnesses. Metabolic syndrome (MetS), a risk factor for cardiovascular disease, is a side-effect of SGA-treatment. We conducted a cross-sectional study and assessed the association of the methylenetetrahydrofolate reductase (MTHFR) C677T variant with features of MetS in SGA-treated (n=105) and SGA-naïve (n=112) children. We targeted the MTHFR C677T variant, because it is associated with risk for cardiovascular disease, and features of MetS in adults without psychiatric illness. MetS in children is based on the presence of any three of the following: waist circumference ≥ 90th percentile for age and sex; plasma triglyceride ≥ 1.24 mmol l(-1); plasma high-density lipoprotein-cholesterol ≤ 1.03 mmol l(-1); systolic or diastolic blood pressure ≥ 90th percentile for age, sex, and height; and fasting glucose ≥ 5.6 mmol l(-1). We found that 15% of SGA-treated children had MetS compared with 2% of SGA-naïve children (OR 8.113, P<0.05). No effect of the MTHFR C677T variant on psychiatric diagnosis was observed. The MTHFR 677T allele was associated (P<0.05) with MetS (OR 5.75, 95% CI= 1.18-28.12) in SGA-treated children. Models adjusted for duration of SGA treatment, ethnicity, sex, age and use of other medications revealed a positive relationship between the MTHFR 677T allele and diastolic blood pressure Z-scores (P=0.001) and fasting plasma glucose (P<0.05) in SGA-treated children. These findings illustrate the high prevalence of MetS in SGA-treated children and suggest metabolic alterations associated with the MTHFR C677T variant may have a role in the development of MetS features in SGA-treated children.

DNA methylation of stress-related genes and LINE-1 repetitive elements across the healthy human placenta

OBJECTIVES

DNA methylation is known to play a critical role in regulating development of placental morphology and physiology. The methylation of genes mediated by glucocorticoid hormones may be particularly vulnerable to intrauterine stress in the placenta. However little is known about DNA methylation of stress-related genes within a healthy placenta, and particularly whether methylation occurs uniformly across different regions of the placenta, which is a critical question for researchers seeking to analyze methylation patterns. We examined DNA methylation across four regions of the placenta to evaluate methylation levels of stress-related genes within a healthy placenta, and to evaluate whether methylation patterns vary by sampling location.

STUDY DESIGN

We evaluated levels of DNA methylation of three stress-related genes: NR3C1, BDNF, and 11B-HSD2 and of the repetitive element, LINE-1, in four different sample locations of 20 healthy placentas.

MAIN OUTCOME MEASURES

Pyrosequencing was used to quantify levels of methylation at CpG sites within the promoter regions of each of the three stress-related genes, and global methylation of LINE-1.

RESULTS

Very low levels of methylation were found across all three stress-related genes; no gene showed a median methylation level greater than 4.20% across placental regions. Variation in methylation between placental regions for stress-related genes and for LINE-1 was minimal.

CONCLUSIONS

Our data suggest that these frequently studied stress-related genes have low levels of methylation in healthy placenta tissue. Minimal variation between sites suggests that sampling location does not affect DNA methylation analyses of these genes or of LINE-1 repetitive elements.

Perinatal selective serotonin reuptake inhibitor exposure: impact on brain development and neural plasticity

Selective serotonin reuptake inhibitor (SSRI) medications are the most common antidepressant treatment used during pregnancy and the postpartum period. Up to 10% of pregnant women are prescribed SSRIs. Serotonin plays an integral part in neurodevelopment, and questions have been raised about the placental transfer of SSRIs and the effects of preventing reuptake of presynaptic serotonin on fetal neurodevelopment. Preclinical data is beginning to document a role of early exposure to SSRIs in long-term developmental outcomes related to a number of brain regions, such as the hippocampus, cortex and cerebellum. To date, the majority of preclinical work has investigated the developmental effects of SSRIs in the offspring of healthy mothers; however, more research is needed on the effects of these medications in the face of maternal adversity. This minireview will highlight emerging evidence from clinical and preclinical studies investigating the impact of perinatal SSRI exposure on brain development and neural plasticity.

Epigenetic effects of early developmental experiences

Early-life adversity can affect brain development and behavior. Emerging evidence from studies on both humans and rodents suggests that epigenetic mechanisms may play a critical role in shaping our biology in response to the quality of the environment. This article highlights the research findings suggesting that prenatal maternal stress, postnatal maternal care, and infant neglect/abuse can lead to epigenetic variation, which may have long-term effects on stress responsivity, neuronal plasticity, and behavior.

Effects of citalopram on serotonin and CRF systems in the midbrain of primates with differences in stress sensitivity

This chapter reviews the neurobiological effects of stress sensitivity and s-citalpram (CIT) treatment observed in our nonhuman primate model of functional hypothalamic amenorrhea (FHA). This type of infertility, also known as stress-induced amenorrhea, is exhibited by cynomolgus macaques. In small populations, some individuals are stress-sensitive (SS) and others are highly stress-resilient (HSR). The SS macaques have suboptimal secretion of estrogen and progesterone during normal menstrual cycles. SS monkeys also have decreased serotonin gene expression and increased CRF expression compared to HSR monkeys. Recently, we found that CIT treatment improved ovarian steroid secretion in SS monkeys, but had no effect in HSR monkeys. Examination of the serotonin system revealed that SS monkeys had significantly lower Fev (fifth Ewing variant, rodent Pet1), TPH2 (tryptophan hydroxylase 2), 5HT1A autoreceptor and SERT (serotonin reuptake transporter) expression in the dorsal raphe than SR monkeys. However, CIT did not alter the expression of either Fev, TPH2, SERT or 5HT1A mRNAs. In contrast, SS monkeys tended to have a higher density of CRF fiber innervation of the dorsal raphe than HSR monkeys, and CIT significantly decreased the CRF fiber density in SS animals. In addition, CIT increased CRF-R2 gene expression in the dorsal raphe. We speculate that in a 15-week time frame, the therapeutic effect of S-citalopram may be achieved through a mechanism involving extracellular serotonin inhibition of CRF and stimulation of CRF-R2, rather than alteration of serotonin-related gene expression.