Epigenetic effects of glucocorticoids

The neurobiological effects of childhood maltreatment on brain structure, function, and attachment

Childhood maltreatment is a risk factor for psychopathologies, and influences brain development at specific periods, particularly during early childhood and adolescence. This narrative review addresses phenotypic alterations in sensory systems associated with specific types of childhood maltreatment exposure, periods of vulnerability to the neurobiological effects of maltreatment, and the relationships between childhood maltreatment and brain structure, function, connectivity, and network architecture; psychopathology; and resilience. It also addresses neurobiological alterations associated with maternal communication and attachment disturbances, and uses laboratory-based measures during infancy and case-control studies to elucidate neurobiological alterations in reactive attachment disorders in children with maltreatment histories. Moreover, we review studies on the acute effects of oxytocin on reactive attachment disorder and maltreatment and methylation of oxytocin regulatory genes. Epigenetic changes may play a critical role in initiating or producing the atypical structural and functional brain alterations associated with childhood maltreatment. However, these changes could be reversed through psychological and pharmacological interventions, and by anticipating or preventing the emergence of brain alterations and subsequent psychopathological risks.

DNA methylation variation after a parenting program for child conduct problems: Findings from a randomized controlled trial

This study investigated associations of the Incredible Years (IY) parenting program with children's DNA methylation. Participants were 289 Dutch children aged 3-9 years (75% European ancestry, 48% female) with above-average conduct problems. Saliva was collected 2.5 years after families were randomized to IY or care as usual (CAU). Using an intention-to-treat approach, confirmatory multiple-regression analyses revealed no significant differences between the IY and CAU groups in children's methylation levels at the NR3C1 and FKBP5 genes. However, exploratory epigenome-wide analyses revealed nine differentially methylated regions between groups, coinciding with SLAMF1, MITF, FAM200B, PSD3, SNX31, and CELSR1. The study provides preliminary evidence for associations of IY with children's salivary methylation levels and highlights the need for further research into biological outcomes of parenting programs.

Adverse effects of early-life stress: focus on the rodent neuroendocrine system

Early-life stress is associated with a high prevalence of mental illnesses such as post-traumatic stress disorders, attention-deficit/hyperactivity disorder, schizophrenia, and anxiety or depressive behavior, which constitute major public health problems. In the early stages of brain development after birth, events such as synaptogenesis, neuron maturation, and glial differentiation occur in a highly orchestrated manner, and external stress can cause adverse long-term effects throughout life. Our body utilizes multifaceted mechanisms, including neuroendocrine and neurotransmitter signaling pathways, to appropriately process external stress. Newborn individuals first exposed to early-life stress deploy neurogenesis as a stress-defense mechanism; however, in adulthood, early-life stress induces apoptosis of mature neurons, activation of immune responses, and reduction of neurotrophic factors, leading to anxiety, depression, and cognitive and memory dysfunction. This process involves the hypothalamus-pituitary-adrenal axis and neurotransmitters secreted by the central nervous system, including norepinephrine, dopamine, and serotonin. The rodent early-life stress model is generally used to experimentally assess the effects of stress during neurodevelopment. This paper reviews the use of the early-life stress model and stress response mechanisms of the body and discusses the experimental results regarding how early-life stress mediates stress-related pathways at a high vulnerability of psychiatric disorder in adulthood.

Mild daily stress, in interaction with NR3C1 DNA methylation levels, is linked to alterations in the HPA axis and ANS response to acute stress in early adolescents

BACKGROUND

Daily Hassles (DH) or daily stress - is a mild type of stressor with unique contributions to psychological distress. Yet, most prior studies that investigate the effects of stressful life experiences focus on childhood trauma or on early life stress and little is known about the effects of DH on epigenetic changes in stress system related genes and on the physiological response to social stressors.

METHODS

In the present study, conducted among 101 early adolescents (mean age = 11.61; SD = 0.64), we investigated whether Autonomic Nervous System (ANS) (namely heart rate and heart rate variability) and Hypothalamic-Pituitary-Adrenal (HPA) axis functioning (measured as cortisol stress reactivity and recovery) are associated with DNA methylation (DNAm) in the glucocorticoid receptor gene (NR3C1), the level of DH and their interaction. To assess the stress system functioning the TSST protocol was used.

RESULTS

Our findings show that higher NR3C1 DNAm in interaction with higher levels of daily hassles, is associated with blunted HPA axis reactivity to psychosocial stress. In addition, higher levels of DH are associated with extended HPA axis stress recovery. In addition, participants with higher NR3C1 DNAm had lower ANS adaptability to stress, specifically lower parasympathetic withdrawal; for heart rate variability this effect was strongest for participants with higher level of DH.

CONCLUSIONS

The observation that interaction effects between NR3C1 DNAm levels and daily stress on the functioning of the stress-systems, are already detectable in young adolescents, highlights the importance of early interventions, not only in the case of trauma, but also daily stress. This might help to prevent stress-induced mental and physical disorders later in life.

Effects of stress and mindfulness on epigenetics

Epigenetics are heritable changes in the rate of gene expression without any modification of the DNA sequence and occur in response to environmental changes. Tangible changes to the external surroundings may be practical causes for epigenetic modifications, playing a potential evolutionary role. While fight, flight, or freeze responses once served a concrete role in survival, modern humans may not face similar existential threats that warrant psychological stress. Yet, chronic mental stress is predominant in modern life. This chapter elucidates the deleterious epigenetic changes that occur due to chronic stress. In an exploration of mindfulness-based interventions (MBIs) as a potential antidote to such stress-induced epigenetic modifications, several pathways of action are uncovered. The epigenetic changes that occur because of mindfulness practice are demonstrated across the hypothalamic-pituitary-adrenal axis, serotonergic transmission, genomic health and aging, and neurological biomarkers.

Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development

It is often assumed that the transfer of maternal glucocorticoids (GCs; e.g., corticosterone or cortisol) to offspring is an inevitable cost associated with adverse or stressful conditions experienced by mothers. However, recent evidence indicates that maternal GCs may adaptively programme particular physiological and molecular pathways during development to enhance offspring fitness. In this context, an important mechanism through which maternal GCs may lastingly affect offspring phenotypic quality and survival is via effects on embryo telomerase activity and so on offspring postnatal telomere length. Here, using a field experimental design for which we manipulated the corticosterone content in yellow-legged gull (Larus michahellis) eggs, we show that embryos from corticosterone-injected eggs not only had a higher telomerase activity but also longer telomeres just after hatching. A complementary analysis further revealed that gull hatchlings with longer telomeres had a higher survival probability during the period when most of the chick mortality occurs. Given the important role that telomere length and its restoring mechanisms have on ageing trajectories and disease risk, our findings provide a new mechanistic link by which mothers may presumably shape offspring life-history trajectories and phenotype.

A Role for Histone Deacetylases in the Biology and Treatment of Post-Traumatic Stress Disorder: What Do We Know and Where Do We Go from Here?

Post-traumatic stress disorder is a prevalent disorder within the USA and worldwide with a yearly diagnosis rate of 2-4% and affecting women more than men. One of the primary methods for study of this stress disorder relies on animal models as there are few noninvasive methods and few replicated peripheral biomarkers for use in humans. One area of active research in psychiatric neuroscience is the field of epigenetics - how the chemical modifications of the genetic code regulate behavior. The dynamic changes in histone acetylation and deacetylation in the brain are not fully reflected by the study of peripheral biomarker. In this review, we aim to examine the role of histone acetylation and deacetylation in memory formation and fear memory learning. The studies discussed here focus largely on the role of histone deacetylases (HDACs) in animal models of trauma and fear response. Many studies used HDAC inhibitors to elucidate the effects after inhibition of these enzymes after trauma or stress. These studies of memory processing and cued fear extinction in animal can often shed light on human disorders of cued fear responses and memory dysregulation after stress or trauma such as in PTSD. These results provide strong evidence for a role of these enzymes in PTSD in humans. The few clinical studies that exist with HDAC inhibitors also suggest a fundamental role of these enzymes in the neurobiology of the stress response. Further study of these enzymes in both clinical and pre-clinical settings may help elucidate the neurobiology of stress-related pathology like PTSD and provide a foundation for novel therapy to treat these disorders.

Cocaine-induced inheritable epigenetic marks may be altered by changing early postnatal fostering

Here, we explored the hypothesis that parental cocaine exposure could alter epigenetic machinery in their drug-naive offspring while early postnatal fostering may further modify the accompanied neurochemical and functional components. Variant drug-naive pups were produced from cocaine-exposed or unexposed C57BL/6 female mice that were matched with their male counterparts for mating. Within 3 days of birth, half of the pups were cross-fostered and nurtured by non-biological lactating dams. The pups were initially examined for locomotor activity and memory performance and subsequently for changes in DNA methylation in promoter regions of cAMP response element modulator (Crem) and Fosb in the prefrontal cortex at 48 days postnatum. The impact of postnatal fostering on these parameters was also investigated. Our results showed that cocaine exposure significantly decreased both Crem and Fosb methylation in the prefrontal cortex of progenitor mice, while similar patterns of methylation were replicated in the brains of drug-naive non-fostered offspring mice but reversed by postnatal fostering. Furthermore, offspring raised by cocaine-exposed dams were impaired in discriminative learning and exhibited memory decline, whereas locomotor activity remains unaltered in all groups of mice. Our data provide some evidence that indirect exposure to cocaine may cause marked epigenetic changes within the cortical networks of drug-naive descendants and that mediation by Crem/Fosb signalling in this brain region may be beneficial, while early postnatal fostering may further engineer molecular switching that may predispose the individual to future risky behaviours as well as accumulative potential to developing cognitive impairment later in life.

Attachment and Epigenetics: A Scoping Review of Recent Research and Current Knowledge

Background

Epigenetic research has pointed to that the interaction between genetics and environmental factors may play a role in making some individuals more vulnerable than others.

Aim

The aim of this article was to present a broad perspective on the current state of knowledge in a relatively new and complex field of “attachment and epigenetic processes.”

Method

We conducted a scoping review based on a systematic literature search in PsycINFO, PubMed, and Embase databases for relevant abstracts using the terms attachment and epigenet*.

Results

In total, 11 studies were included. Research predating 2009 and animal studies were excluded in order to review the current state of research in humans.

Conclusion

Overall, there seems to be a consistency in the literature, pointing to a link between early childhood adversity, attachment processes, and epigenetic changes. However, research in human subjects is still limited.

Epigenetic Modifications due to Environment, Ageing, Nutrition, and Endocrine Disrupting Chemicals and Their Effects on the Endocrine System

The epigenome of an individual can be altered by endogenous hormones, environment, age, diet, and exposure to endocrine disrupting chemicals (EDCs), and the effects of these modifications can be seen across generations. Epigenetic modifications to the genome can alter the phenotype of the individual without altering the DNA sequence itself. Epigenetic modifications include DNA methylation, histone modification, and aberrant microRNA (miRNA) expression; they begin during germ cell development and embryogenesis and continue until death. Hormone modulation occurs during the ageing process due to epigenetic modifications. Maternal overnutrition or undernutrition can affect the epigenome of the fetus, and the effects can be seen throughout life. Furthermore, maternal care during the childhood of the offspring can lead to different phenotypes seen in adulthood. Diseases controlled by the endocrine system, such as obesity and diabetes, as well as infertility in females can be associated with epigenetic changes. Not only can these phenotypes be seen in F1, but also some chemical effects can be passed through the germline and have effects transgenerationally, and the phenotypes are seen in F3. The following literature review expands upon these topics and discusses the state of the science related to epigenetic effects of age, diet, and EDCs on the endocrine system.

Epigenetic Mechanisms in the Neurodevelopmental Theory of Depression

The genome (genes), epigenome, and environment work together from the earliest stages of human life to produce a phenotype of human health or disease. Epigenetic modifications, including among other things: DNA methylation, modifications of histones and chromatin structure, as well as functions of noncoding RNA, are coresponsible for specific patterns of gene expression. This refers also to mental disorders, including depressive disorders. Early childhood experiences accompanied by severe stressors (considered a risk factor for depression in adult life) are linked with changes in gene expression. They include genes involved in a response to stress (hypothalamic-pituitary-adrenal axis, HPA), associated with autonomic nervous system hyperactivity and with cortical, and subcortical processes of neuroplasticity and neurodegeneration. These are, among others: gene encoding glucocorticoid receptor, FK506 binding protein 5 gene (FKBP5), gene encoding arginine vasopressin and oestrogen receptor alpha, 5-hydroxy-tryptamine transporter gene (SLC6A4), and gene encoding brain-derived neurotrophic factor. How about personality? Can the experiences unique to every human being, the history of his or her development and gene-environment interactions, through epigenetic mechanisms, shape the features of our personality? Can we pass on these features to future generations? Hence, is the risk of depression inherent in our biological nature? Can we change our destiny?

Histone deacetylase 4 (HDAC4): a new player in anorexia nervosa?

Anorexia nervosa (AN) and other eating disorders continue to constitute significant challenges for individual and public health. AN is thought to develop as a result of complex interactions between environmental triggers, psychological risk factors, sociocultural influences, and genetic vulnerability. Recent research developments have highlighted a novel potentially relevant component in the AN etiology-activity of the histone deacetylase 4 (HDAC4) gene that has emerged in several recent studies related to AN. HDAC4 is a member of the ubiquitously important family of epigenetic modifier enzymes called histone deacetylases and has been implicated in processes related to the formation and function of the central nervous system (CNS), bone, muscle, and metabolism. In a family affected by eating disorders, a missense mutation in HDAC4 (A786T) was found to segregate with the illness. The relevance of this mutation in eating-related behaviors was further confirmed with mouse models. Despite  the fact that HDAC4 has not been identified as a significant signal in genome-wide association studies in AN, several studies have found significant or near-significant methylation differences in HDAC4 locus in peripheral tissues of actively ill AN patients in comparison with different control groups. Limitations of these studies include a lack of understanding of to what extent the changes in methylation are predictive of AN as such changes might also occur as a consequence of the disease. It remains to be determined how methylation in peripheral tissues correlates with that in the CNS and how different methylation patterns affect HDAC4 expression. The present review discusses the findings and potential roles of HDAC4 in AN. Its emerging roles in learning and neuroplasticity may be specific and relevant for the etiology of AN and potentially lead to novel therapeutic approaches.

NR3C1 methylation as a moderator of the effects of maternal support and stress on insecure attachment development

We examined the prediction that the interaction between Glucocorticoid Receptor Gene (NR3C1) methylation, stress, and experienced maternal support predicts anxious and avoidant attachment development. This was tested in a general population sample of 487 children and adolescents (44% boys, Mage = 11.84, SDage = 2.4). These children were followed over a period of 18 months. In line with the prediction, we found that NR3C1 methylation moderates the effect of maternal support during stress on anxious attachment development 18 months later. More stressed children who experienced less maternal support reported increased anxious attachment when their NR3C1 gene was highly methylated. This effect could not be explained by children's level of psychopathology. No effects were found for attachment avoidance. These data provide the first prospective evidence that epigenetic processes are involved in attachment development. (PsycINFO Database Record

Epigenetics and Health Disparities

PURPOSE OF REVIEW

African Americans disproportionately suffer from leading causes of morbidity and mortality including cardiovascular disease (CVD), cancer, and preterm birth. Disparities can arise from multiple social and environmental exposures, but how the human body responds to these exposures to result in pathophysiologic states is incompletely understood.

RECENT FINDINGS

Epigenetic mechanisms, particularly DNA methylation, can be altered in response to exposures such as air pollution, psychosocial stress, and smoking. Each of these exposures has been linked to the above health states (CVD, cancer, and preterm birth) with striking racial disparities in exposure levels. DNA methylation patterns have also been shown to be associated with each of these health outcomes.

SUMMARY

Whether DNA methylation mediates exposure-disease relationships and can help explain racial disparities in health is not known. However, because many environmental and adverse social exposures disproportionately affect minorities, understanding the role that epigenetics plays in the human response to these exposures that often result in disease, is critical to reducing disparities in morbidity and mortality.

Glucocorticoids in Fish Eggs: Variation, Interactions with the Environment, and the Potential to Shape Offspring Fitness

Wild and captive vertebrates face multiple stressors that all have the potential to induce chronic maternal stress (i.e., sustained, elevated plasma glucocorticoids), resulting in embryo exposure to elevated maternally derived glucocorticoids. In oviparous taxa such as fish, maternally derived glucocorticoids in eggs are known for their capacity to shape offspring phenotype. Using a variety of methodologies, scientists have quantified maternally derived levels of egg cortisol, the primary glucocorticoid in fishes, and examined the cascading effects of egg cortisol on progeny phenotype. Here we summarize and interpret the current state of knowledge on egg cortisol in fishes and the relationships linking maternal stress/state to egg cortisol and offspring phenotype/fitness. Considerable variation in levels of egg cortisol exists across species and among females within a species; this variation is hypothesized to be due to interspecific differences in reproductive life history and intraspecific differences in female condition. Outcomes of experimental studies manipulating egg cortisol vary both inter- and intraspecifically. Moreover, while exogenous elevation of egg cortisol (as a proxy for maternal stress) induces phenotypic changes commonly considered to be maladaptive (e.g., smaller offspring size), emerging work in other taxa suggests that there can be positive effects on fitness when the offspring's environment is taken into account. Investigations into (i) mechanisms by which egg cortisol elicits phenotypic change in offspring (e.g., epigenetics), (ii) maternal and offspring buffering capacity of cortisol, and (iii) factors driving natural variation in egg cortisol and how this variation affects offspring phenotype and fitness are all germane to discussions on egg glucocorticoids as signals of maternal stress.

Physiological Stress Responses in Amphibian Larvae to Multiple Stressors Reveal Marked Anthropogenic Effects even below Lethal Levels

Natural and anthropogenic disturbances cause profound alterations in organisms, inducing physiological adjustments to avoid, reduce, or remedy the impact of disturbances. In vertebrates, the stress response is regulated via neuroendocrine pathways, including the hypothalamic-pituitary-interrenal axis that regulates the secretion of glucocorticoids. Glucocorticoids have cascading effects on multiple physiological pathways, affecting the metabolic rate, reactive oxygen species production, or immune system. Determining the extent to which natural and anthropogenic environmental factors induce stress responses in vertebrates is of great importance in ecology and conservation biology. Here we study the physiological stress response in spadefoot toad tadpoles (Pelobates cultripes) against three levels of a series of natural and anthropogenic stressors common to many aquatic systems: salinity (0, 6, and 9 ppt), herbicide (0, 1, and 2 mg/L acid equivalent of glyphosate), water acidity (pH 4.5, 7.0, and 9.5), predators (absent, native, and invasive), and temperature (21°, 25°, and 29°C). The physiological stress response was assessed examining corticosterone levels, standard metabolic rate, activity of antioxidant enzymes, oxidative cellular damage in lipids, and immunological status. We found that common stressors substantially altered the physiological state of tadpoles. In particular, salinity and herbicides cause dramatic physiological changes in tadpoles. Moreover, tadpoles reduced corticosterone levels in the presence of natural predators but did not do so against invasive predators, indicating a lack of innate recognition. Corticosterone and the antioxidant enzyme glutathione reductase were the most sensitive parameters to stress in this study. Anthropogenic perturbations of aquatic systems pose serious threats to larval amphibians even at nonlethal concentrations, judging from the marked physiological stress responses generated, and reveal the importance of incorporating physiological information onto conservation, ecological, and evolutionary studies.

Glucocorticoid programming of intrauterine development

Glucocorticoids (GCs) are important environmental and maturational signals during intrauterine development. Toward term, the maturational rise in fetal glucocorticoid receptor concentrations decreases fetal growth and induces differentiation of key tissues essential for neonatal survival. When cortisol levels rise earlier in gestation as a result of suboptimal conditions for fetal growth, the switch from tissue accretion to differentiation is initiated prematurely, which alters the phenotype that develops from the genotype inherited at conception. Although this improves the chances of survival should delivery occur, it also has functional consequences for the offspring long after birth. Glucocorticoids are, therefore, also programming signals that permanently alter tissue structure and function during intrauterine development to optimize offspring fitness. However, if the postnatal environmental conditions differ from those signaled in utero, the phenotypical outcome of early-life glucocorticoid receptor overexposure may become maladaptive and lead to physiological dysfunction in the adult. This review focuses on the role of GCs in developmental programming, primarily in farm species. It examines the factors influencing GC bioavailability in utero and the effects that GCs have on the development of fetal tissues and organ systems, both at term and earlier in gestation. It also discusses the windows of susceptibility to GC overexposure in early life together with the molecular mechanisms and long-term consequences of GC programming with particular emphasis on the cardiovascular, metabolic, and endocrine phenotype of the offspring.

Programming of the hypothalamic-pituitary-interrenal axis by maternal social status in zebrafish (Danio rerio)

The present study examined the effects of maternal social status, with subordinate status being a chronic stressor, on development and activity of the stress axis in zebrafish embryos and larvae. Female zebrafish were confined in pairs for 48 h to establish dominant/subordinate hierarchies; their offspring were reared to 144 h post-fertilization (hpf) and sampled at five time points over development. No differences were detected in maternal cortisol contribution, which is thought to be an important programmer of offspring phenotype. However, once zebrafish offspring began to synthesize cortisol de novo (48 hpf), larvae of dominant females exhibited significantly lower baseline cortisol levels than offspring of subordinate females. These lower cortisol levels may reflect reduced hypothalamic-pituitary-interrenal (HPI) axis activity, because corticotropin-releasing factor (crf) and cytochrome p450 side chain cleavage enzyme (p450scc) mRNA levels also were lower in larvae from dominant females. Moreover, baseline mRNA levels of HPI axis genes continued to be affected by maternal social status beyond 48 hpf. At 144 hpf, stress-induced cortisol levels were significantly lower in offspring of subordinate females. These results suggest programming of stress axis function in zebrafish offspring by maternal social status, emphasizing the importance of maternal environment and experience on offspring stress axis activity.

Male germline transmits fetal alcohol epigenetic marks for multiple generations: a review

Alcohol exposure during fetal and early postnatal development can lead to an increased incidence of later life adult-onset diseases. Examples include central nervous system dysfunction, depression, anxiety, hyperactivity, and an inability to deal with stressful situations, increased infection and cancer. Direct effects of alcohol leading to developmental abnormalities often involve epigenetic modifications of genes that regulate cellular functions. Epigenetic marks carried over from the parents are known to undergo molecular programming events that happen early in embryonic development by a wave of DNA demethylation, which leaves the embryo with a fresh genomic composition. The proopiomelanocortin (Pomc) gene controls neuroendocrine-immune functions and is imprinted by fetal alcohol exposure. Recently, this gene has been shown to be hypermethylated through three generations. Additionally, the alcohol epigenetic marks on the Pomc gene are maintained in the male but not in the female germline during this transgenerational transmission. These data suggest that the male-specific chromosome might be involved in transmitting alcohol epigenetic marks through multiple generations.

Normal cortisol response to cold pressor test, but lower free thyroxine, after recovery from undernutrition

Undernutrition is a stressor with long-term consequences, and the effect of nutritional recovery on cortisol and thyroid hormone status is unknown. To investigate basal thyroid hormones and the cortisol response to a cold pressor test in children recovered from undernutrition, a cross-sectional study was undertaken on children (6–16 years) separated into four groups: control (n 41), stunted (n 31), underweight (n 27) and recovered (n 31). Salivary cortisol was collected over the course of 10 h: upon awakening, before and after an unpleasant and a pleasant stimulus. Cortisol upon awakening was highest in the stunted and lowest in the underweight groups: control=5·05 (95 % CI 3·71, 6·89) nmol/l, stunted=6·62 (95 % CI 3·97, 11·02) nmol/l, underweight=2·51 (95 % CI 1·75, 3·63) nmol/l and recovered=3·46 (95 % CI 2·46, 4·90) nmol/l (P=0·005). Girls had higher cortisol concentrations upon awakening compared with boys (P=0·021). The undernourished groups showed an elevated cortisol response both to the unpleasant stimulus and at the last measurement (16.00 hours) compared with that of the recovered group: AUC, control=2·07 (95 % CI 1·69, 2·45) nmol/l×30 min, stunted=2·48 (95 % CI 1·91, 3·06) nmol/l×30 min, underweight=2·52 (95 % CI 2·07, 2·97) nmol/l×30 min, recovered=1·68 (95 % CI 1·26, 2·11) nmol/l×30 min (P=0·042); and control=2·03 (95 % CI 1·75, 2·39) nmol/l×30 min, stunted=2·51 (95 % CI 1·97, 3·19) nmol/l×30 min, underweight=2·61 (95 % CI 2·16, 3·16) nmol/l×30 min, recovered=1·70 (95 % CI 1·42, 2·03) nmol/l×30 min (P=0·009). Lower free thyroxine (T4) was found in the recovered and stunted groups: control=1·28 (95 % CI 1·18, 1·39) pmol/l, stunted=0·98 (95 % CI 0·87, 1·10) pmol/l, underweight=1·10 (95 % CI 1·01, 1·21) pmol/l and recovered=0·90 (95 % CI 0·83, 0·99) pmol/l (P<0·001). Multivariate analysis showed a lower cortisol concentration along 10 h (06.00–16.00 hours) in the recovered compared with the other groups (P=0·017), and similar concentrations between the recovered and control group. In conclusion, the children with recovery in weight and height had a cortisol stress response similar to control but a lower basal free T4. Longitudinal studies are warranted to determine the extent of these endocrine changes after recovery of undernutrition and in adulthood.

Glucocorticoids as regulatory signals during intrauterine development

NEW FINDINGS

What is the topic of this review? This review discusses the role of the glucocorticoids as regulatory signals during intrauterine development. It examines the functional significance of these hormones as maturational, environmental and programming signals in determining offspring phenotype. What advances does it highlight? It focuses on the extensive nature of the regulatory actions of these hormones. It highlights the emerging data that these actions are mediated, in part, by the placenta, other endocrine systems and epigenetic modifications of the genome. Glucocorticoids are important regulatory signals during intrauterine development. They act as maturational, environmental and programming signals that modify the developing phenotype to optimize offspring viability and fitness. They affect development of a wide range of fetal tissues by inducing changes in cellular expression of structural, transport and signalling proteins, which have widespread functional consequences at the whole organ and systems levels. Glucocorticoids, therefore, activate many of the physiological systems that have little function in utero but are vital at birth to replace the respiratory, nutritive and excretory functions previously carried out by the placenta. However, by switching tissues from accretion to differentiation, early glucocorticoid overexposure in response to adverse conditions can programme fetal development with longer term physiological consequences for the adult offspring, which can extend to the next generation. The developmental effects of the glucocorticoids can be direct on fetal tissues with glucocorticoid receptors or mediated by changes in placental function or other endocrine systems. At the molecular level, glucocorticoids can act directly on gene transcription via their receptors or indirectly by epigenetic modifications of the genome. In this review, we examine the role and functional significance of glucocorticoids as regulatory signals during intrauterine development and discuss the mechanisms by which they act in utero to alter the developing epigenome and ensuing phenotype.

Early Life Stress, Nicotinic Acetylcholine Receptors and Alcohol Use Disorders

Stress is a major driving force in alcohol use disorders (AUDs). It influences how much one consumes, craving intensity and whether an abstinent individual will return to harmful alcohol consumption. We are most vulnerable to the effects of stress during early development, and exposure to multiple traumatic early life events dramatically increases the risk for AUDs. However, not everyone exposed to early life stress will develop an AUD. The mechanisms determining whether an individual’s brain adapts and becomes resilient to the effects of stress or succumbs and is unable to cope with stress remain elusive. Emerging evidence suggests that neuroplastic changes in the nucleus accumbens (NAc) following early life stress underlie the development of AUDs. This review discusses the impact of early life stress on NAc structure and function, how these changes affect cholinergic signaling within the mesolimbic reward pathway and the role nicotinic acetylcholine receptors (nAChRs) play in this process. Understanding the neural pathways and mechanism determining stress resilience or susceptibility will improve our ability to identify individuals susceptible to developing AUDs, formulate cognitive interventions to prevent AUDs in susceptible individuals and to elucidate and enhance potential therapeutic targets, such as the nAChRs, for those struggling to overcome an AUD.

Biology of stress revisited: intracellular mechanisms and the conceptualization of stress

Application of allostatic theory to stress during the 1990s refocused attention on internal responses to a perceived hazard, and the last 20 years has seen considerable developments in the biological contexts of stress. Evidence from neuroscience now suggests that secretion of the hormone cortisol is not only stimulated by the outcomes of cognitive transaction but it also feeds back and contributes positively to the cognitive adaptation that is a feature of stress resilience. More recently, the operative intracellular mechanisms are beginning to be understood and provide an insight into the regulation and maintenance of intracellular homeostasis that underpins adaptive change and vulnerability. The maintenance or appropriate modulation of intracellular homeostasis usually provides a buffering of potential adverse interactions. However, the capacity to do so is diminished during chronic stress leading to intracellular and subsequently systemic, homeostatic failure and hence maladaptation. This area of research seems far removed from cognitive theory, but placing intracellular homeostasis at the core of cognitive and biological responses supports the concept of stress as a genuinely psycho-biological phenomenon.

FGF2 is a target and a trigger of epigenetic mechanisms associated with differences in emotionality: partnership with H3K9me3

Posttranslational modifications of histone tails in chromatin template can result from environmental experiences such as stress and substance abuse. However, the role of epigenetic modifications as potential predisposing factors in affective behavior is less well established. To address this question, we used our selectively bred lines of high responder (bHR) and low responder (bLR) rats that show profound and stable differences in affective responses, with bLRs being prone to anxiety- and depression-like behavior and bHRs prone to addictive behavior. We first asked whether these phenotypes are associated with basal differences in epigenetic profiles. Our results reveal broad between-group differences in basal levels of trimethylated histone protein H3 at lysine 9 (H3K9me3) in hippocampus (HC), amygdala, and nucleus accumbens. Moreover, levels of association of H3K9me3 at Glucocorticoid Receptor (GR) and Fibroblast growth Factor 2 (FGF2) promoters differ reciprocally between bHRs and bLRs in these regions, consistent with these genes' opposing levels of expression and roles in modulating anxiety behavior. Importantly, this basal epigenetic pattern is modifiable by FGF2, a factor that modulates anxiety behavior. Thus, early-life FGF2, which decreases anxiety, altered the levels of H3K9me3 and its binding at FGF2 and GR promoters of bLRs rendering them more similar to bHRs. Conversely, knockdown of HC FGF2 altered both anxiety behavior and levels of H3K9me3 in bHRs, rendering them more bLR-like. These findings implicate FGF2 as a modifier of epigenetic mechanisms associated with emotional responsiveness, and point to H3K9me3 as a key player in the regulation of affective vulnerability.

Glucocorticoids and fetal programming part 2: Mechanisms

The lifelong health of an individual is shaped during critical periods of development. The fetus is particularly susceptible to internal and external stimuli, many of which can alter developmental trajectories and subsequent susceptibility to disease. Glucocorticoids are critical in normal development of the fetus, as they are involved in the growth and maturation of many organ systems. The surge in fetal glucocorticoid levels that occurs in most mammalian species over the last few days of pregnancy is an important developmental switch leading to fundamental changes in gene regulation in many organs, including the brain. These changes are important for the transition to postnatal life. Exposure of the fetus to increased levels of glucocorticoids, resulting from maternal stress or treatment with synthetic glucocorticoids, can lead to long-term 'programming' of hypothalamic-pituitary-adrenal function and behaviours. Glucocorticoids act at multiple levels within the fetal brain. Growing evidence indicates that they can exert powerful effects on the epigenome, including on DNA methylation, histone acetylation and microRNA, to influence gene expression. Such influences probably represent a critical component of the 'programming' process, and might be partly responsible for the transgenerational effects of antenatal glucocorticoid exposure on neurologic, cardiovascular and metabolic function.

Development of food intake controls: neuroendocrine and environmental regulation of food intake during early life

This article is part of a Special Issue "Energy Balance". The development of neuroendocrine regulation of food intake during early life has been shaped by natural selection to allow for optimal growth and development rates needed for survival. In vertebrates, neonates or early larval forms typically exhibit "feeding drive," characterized by a developmental delay in 1) responsiveness of the hypothalamus to satiety signals (e.g., leptin, melanocortins) and 2) sensitivity to environmental cues that suppress food intake. Homeostatic regulation of food intake develops once offspring transition to later life history stages when growth is slower, neuroendocrine systems are more mature, and appetite becomes more sensitive to environmental or social cues. Across vertebrate groups, there is a tremendous amount of developmental plasticity in both food intake regulation and stress responsiveness depending on the environmental conditions experienced during early life history stages or by pregnant/brooding mothers. This plasticity is mediated through the organizing effects of hormones acting on the food intake centers of the hypothalamus during development, which alter epigenetic expression of genes associated with ingestive behaviors. Research is still needed to reveal the mechanisms through which environmental conditions during development generate and maintain these epigenetic modifications within the lifespan or across generations. Furthermore, more research is needed to determine whether observed patterns of plasticity are adaptive or pathological. It is clear, however, that developmental programming of food intake has important effects on fitness, and therefore, has ecological and evolutionary implications.

A calcium-deficient diet in rat dams during gestation and nursing affects hepatic 11β-hydroxysteroid dehydrogenase-1 expression in the offspring

BACKGROUND

Prenatal malnutrition can affect the phenotype of offspring by changing epigenetic regulation of specific genes. Several lines of evidence demonstrate that calcium (Ca) plays an important role in the pathogenesis of insulin resistance syndrome. We hypothesized that pregnant female rats fed a Ca-deficient diet would have offspring with altered hepatic glucocorticoid-related gene expression and that lactation would modify these alterations.

METHODOLOGY

We determined the effects of Ca deficiency during pregnancy and/or lactation on hepatic 11β-hydroxysteroid dehydrogenase-1 (Hsd11b1) expression in offspring. Female Wistar rats consumed either a Ca-deficient (D: 0.008% Ca) or control (C: 0.90% Ca) diet ad libitum from 3 weeks preconception to 21 days postparturition. On postnatal day 1, pups were cross-fostered to the same or opposite dams and divided into the following four groups: CC, DD, CD, and DC (first letter: original mother's diet; second letter: nursing mother's diet). All offspring were fed a control diet beginning at weaning (day 21) and were killed on day 200 ± 7. Serum insulin and adipokines in offspring were measured using ELISA kits.

PRINCIPAL FINDINGS

In males, mean levels of insulin, glucose, and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) were higher in the DD and DC groups than in the CC group. We found no difference in HOMA-IR between the CC and CD groups in either males or females. Expression of Hsd11b1 was lower in male DD rats than in CC rats. Hsd11b1 expression in male offspring nursed by cross-fostered dams was higher than that in those nursed by dams fed the same diet; CC vs. CD and DD vs. DC. In females, Hsd11b1 expression in DC rats was higher than that in CC rats.

CONCLUSIONS

These findings indicated that maternal Ca restriction during pregnancy and/or lactation alters postnatal growth, Hsd11b1 expression, and insulin resistance in a sex-specific manner.

Childhood family living arrangements and blood pressure in black men: the Howard University Family Study

Black men have higher blood pressure (BP) levels and consequently higher prevalence of hypertension compared with men from other ethnic groups in the United States. Socio-familial factors in childhood have been found to play an important role in hypertension, but few studies have examined this relationship among black men. We investigated whether childhood family living arrangements are independently associated with mean BP and hypertension in a cross-sectional sample of 515 unrelated black male participants aged ≥20 years enrolled in the Howard University Family Study between 2001 and 2008. Black men who lived with both parents compared with the reference group of men who never lived with both parents during their lifetime had lower systolic BP (-4.4 mm Hg [95% confidence interval {CI}, -7.84 to -0.96]), pulse pressure (-3.9 mm Hg [95% CI, -6.28 to -1.51]), and mean arterial BP (-2.0 mm Hg [95% CI, -4.44 to 0.51]). This protective effect was more pronounced among men who lived with both parents for 1 to 12 years of their lives; they had decreased systolic BP (-6.5 mm Hg [95% CI, -10.99 to -1.95]), pulse pressure (-5.4 mm Hg [95% CI, -8.48 to -2.28]), mean arterial pressure (-3.3 mm Hg [95% CI, -6.56 to 0.00]), and a 46% decreased odds of developing hypertension (odds ratio=0.54; 95% CI, 0.30 to 0.99). No statistically significant associations were found for diastolic BP. These results provide preliminary evidence that childhood family structure exerts a long-term influence on BP among black men.

Transgenerational epigenetics and brain disorders

Neurobehavioral and psychiatric disorders are complex diseases with a strong heritable component; however, to date, genome-wide association studies failed to identify the genetic loci involved in the etiology of these brain disorders. Recently, transgenerational epigenetic inheritance has emerged as an important factor playing a pivotal role in the inheritance of brain disorders. This field of research provides evidence that environmentally induced epigenetic changes in the germline during embryonic development can be transmitted for multiple generations and may contribute to the etiology of brain disease heritability. In this review, we discuss some of the most recent findings on transgenerational epigenetic inheritance. We particularly discuss the findings on the epigenetic mechanisms involved in the heritability of alcohol-induced neurobehavioral disorders such as fetal alcohol spectrum disorders.

Age- and sex-dependent effects of early life stress on hippocampal neurogenesis

Early life stress is a well-documented risk factor for the development of psychopathology in genetically predisposed individuals. As it is hard to study how early life stress impacts human brain structure and function, various animal models have been developed to address this issue. The models discussed here reveal that perinatal stress in rodents exerts lasting effects on the stress system as well as on the structure and function of the brain. One of the structural parameters strongly affected by perinatal stress is adult hippocampal neurogenesis. Based on compiled literature data, we report that postnatal stress slightly enhances neurogenesis until the onset of puberty in male rats; when animals reach adulthood, neurogenesis is reduced as a consequence of perinatal stress. By contrast, female rats show a prominent reduction in neurogenesis prior to the onset of puberty, but this effect subsides when animals reach young adulthood. We further present preliminary data that transient treatment with a glucocorticoid receptor antagonist can normalize cell proliferation in maternally deprived female rats, while the compound had no effect in non-deprived rats. Taken together, the data show that neurogenesis is affected by early life stress in an age- and sex-dependent manner and that normalization may be possible during critical stages of brain development.

Convergence of genetic and environmental factors on parvalbumin-positive interneurons in schizophrenia

Schizophrenia etiology is thought to involve an interaction between genetic and environmental factors during postnatal brain development. However, there is a fundamental gap in our understanding of the molecular mechanisms by which environmental factors interact with genetic susceptibility to trigger symptom onset and disease progression. In this review, we summarize the most recent findings implicating oxidative stress as one mechanism by which environmental insults, especially early life social stress, impact the development of schizophrenia. Based on a review of the literature and the results of our own animal model, we suggest that environmental stressors such as social isolation render parvalbumin-positive interneurons (PVIs) vulnerable to oxidative stress. We previously reported that social isolation stress exacerbates many of the schizophrenia-like phenotypes seen in a conditional genetic mouse model in which NMDA receptors (NMDARs) are selectively ablated in half of cortical and hippocampal interneurons during early postnatal development (Belforte et al., 2010). We have since revealed that this social isolation-induced effect is caused by impairments in the antioxidant defense capacity in the PVIs in which NMDARs are ablated. We propose that this effect is mediated by the down-regulation of PGC-1α, a master regulator of mitochondrial energy metabolism and anti-oxidant defense, following the deletion of NMDARs (Jiang et al., 2013). Other potential molecular mechanisms underlying redox dysfunction upon gene and environmental interaction will be discussed, with a focus on the unique properties of PVIs.

Importance of epigenetic mechanisms in visceral pain induced by chronic water avoidance stress

Epigenetic molecular mechanisms, which include DNA methylation and histone deacetylation, are implicated in the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we demonstrated that repeated water avoidance stress (WAS), a validated model of chronic psychological stress, induces heightened visceral pain behaviors in rodents that resemble irritable bowel syndrome (IBS) sequelae. However, the involvement of epigenetic molecular mechanisms in the pathophysiology of stress-induced visceral pain has not been explored. Our hypothesis is that epigenetic mechanisms within the central nervous system (CNS) are important to chronic stress-induced visceral hypersensitivity. Adult male F-344 rats with intracerebroventricular (i.c.v.) cannulae were exposed to 7 days of repeated WAS. Controls received a SHAM stress. Following the daily 1h stressor, trichostatin A (TSA; 100 ng/ml), a potent histone deacetylase inhibitor, or vehicle (VEH; 0.1% DMSO/saline,) as control was administered via the i.c.v. cannula. Visceral sensitivity was assessed 24h after the final WAS and quantified the visceromotor response (VMR) by recording the number of abdominal contractions in response to graded pressures (20-60 mmHg) of colorectal distensions (CRD). From a separate group of rats that were exposed to repeated WAS or SHAM stress, the amygdala was isolated to assess the methylation status of glucocorticoid receptor (GR) and corticotropin releasing-factor (CRF) genes via bisulfite sequencing and verified by pyrosequencing. GR and CRF gene expression was quantified via qRT-PCR. Stressed rats exhibited visceral hypersensitivity that was significantly attenuated by TSA. Compared to SHAM controls, methylation of the GR gene was increased following WAS while expression of the GR gene was decreased. Methylation of the CRF promoter was decreased with WAS with a concomitant increase in CRF expression. This study demonstrates the involvement of central epigenetic mechanisms in regulating stress-induced visceral hypersensitivity and provides a foundation for exploring the epigenetic mechanisms that may contribute to IBS-like symptomatology.

Predicting PTSD: pre-existing vulnerabilities in glucocorticoid-signaling and implications for preventive interventions

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may develop in response to a traumatic event. Approximately 10% of trauma-exposed individuals subsequently develop PTSD. It is hypothesized that the development of PTSD is associated with biological vulnerability factors, which are already present prior to the onset of symptoms. In this review we present an overview of currently identified vulnerability factors in the glucocorticoid (GC) signaling pathway for the development of PTSD. In addition, the implications of the identified vulnerability factors for potential preventive intervention strategies, including glucocorticoid receptor (GR) agonists and oxytocin, are discussed. Summarized, the findings of these studies indicate that individuals vulnerable for development of PTSD have dysregulations on various levels of the GC-signaling cascade: i.e. low levels of circulating levels of cortisol shortly after trauma, high GR number in peripheral blood mononuclear cells (PBMCs), high GILZ mRNA expression and low FKBP5 expression in PBMCs prior to trauma, and high sensitivity of T-cells for regulation by GCs prior to trauma. Furthermore, single nucleotide polymorphisms in the GR and FKBP5 genes have been found to be associated with increased risk for PTSD. Collectively, the identified vulnerability factors tentatively suggest that the development of PTSD may be preceded by a high sensitivity of various cells for regulation by GCs. The identification of these vulnerability factors may ultimately aid selective targeting of preventive interventions towards individuals at risk for PTSD. In addition, the identification of these vulnerability factors may eventually result in new preventive pharmacological strategies for PTSD.

Transgenerational epigenetic effects on animal behaviour

Over the last decade a shift in paradigm has occurred with respect to the interaction between environment and genes. It is now clear that animal genomes are regulated to a large extent as a result of input from environmental events and experiences, which cause short- and long-term modifications in epigenetic markings of DNA and histones. In this review, the evidence that such epigenetic modifications can affect the behaviour of animals is explored, and whether such acquired behaviour alterations can transfer across generation borders. First, the mechanisms by which experiences cause epigenetic modifications are examined. This includes, for example, methylation of cytosine in CpG positions and acetylation of histones, and studies showing that this can be modified by early experiences. Secondly, the evidence that specific modifications in the epigenome can be the cause of behaviour variation is reviewed. Thirdly, the extent to which this phenotypically active epigenetic variants can be inherited either through the germline or through reoccurring environmental conditions is examined. A particularly interesting observation is that epigenetic modifications are often linked to stress, and may possibly be mediated by steroid effects. Finally, the idea that transgenerationally stable epigenetic variants may serve as substrates for natural selection is explored, and it is speculated that they may even predispose for directed, non-random mutations.

Role of glucocorticoid in developmental programming: evidence from zebrafish

The vertebrate corticosteroid stress response is highly conserved and a key function is to restore homeostasis by mobilizing and reallocating energy stores. This process is primarily initiated by activation of the hypothalamus-pituitary-adrenal axis, leading to the release of corticosteroids into the circulation. In teleosts, cortisol is the primary corticosteroid that is released into the circulation in response to stress. This steroid activates corticosteroid receptors that are ligand-bound transcription factors, modulating downstream gene expression in target tissues. Recent research in zebrafish (Danio rerio) has identified novel roles for cortisol in early developmental processes, including organogenesis and mesoderm formation. As cortisol biosynthesis commences only around the time of hatch in teleosts, the early developmental events are orchestrated by cortisol that is maternally deposited prior to fertilization. This review will highlight the molecular events leading to the development of the corticosteroid stress axis, and the possible role of cortisol in the developmental programming of stress axis function. Use of zebrafish as a model may lead to significant insights into the conserved role of glucocorticoids during early development with potential implications in biomedical research, including fetal stress syndromes in humans.

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.

Caffeine-induced activated glucocorticoid metabolism in the hippocampus causes hypothalamic-pituitary-adrenal axis inhibition in fetal rats

Epidemiological investigations have shown that fetuses with intrauterine growth retardation (IUGR) are susceptible to adult metabolic syndrome. Clinical investigations and experiments have demonstrated that caffeine is a definite inducer of IUGR, as children who ingest caffeine-containing food or drinks are highly susceptible to adult obesity and hypertension. Our goals for this study were to investigate the effect of prenatal caffeine ingestion on the functional development of the fetal hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis and to clarify an intrauterine HPA axis-associated neuroendocrine alteration induced by caffeine. Pregnant Wistar rats were intragastrically administered 20, 60, and 180 mg/kg·d caffeine from gestational days 11–20. The results show that prenatal caffeine ingestion significantly decreased the expression of fetal hypothalamus corticotrophin-releasing hormone. The fetal adrenal cortex changed into slight and the expression of fetal adrenal steroid acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (P450scc), as well as the level of fetal adrenal endogenous corticosterone (CORT), were all significantly decreased after caffeine treatment. Moreover, caffeine ingestion significantly increased the levels of maternal and fetal blood CORT and decreased the expression of placental 11β-hydroxysteroid dehydrogenase-2 (11β-HSD-2). Additionally, both in vivo and in vitro studies show that caffeine can downregulate the expression of fetal hippocampal 11β-HSD-2, promote the expression of 11β-hydroxysteroid dehydrogenase 1 and glucocorticoid receptor (GR), and enhance DNA methylation within the hippocampal 11β-HSD-2 promoter. These results suggest that prenatal caffeine ingestion inhibits the development of the fetal HPA axis, which may be associated with the fetal overexposure to maternal glucocorticoid and activated glucocorticoid metabolism in the fetal hippocampus. These results will be beneficial in elucidating the developmental toxicity of caffeine and in exploring the fetal origin of adult HPA axis dysfunction and metabolic syndrome susceptibility for offspring with IUGR induced by caffeine.

Timing matters: long term effects of adversities from prenatal period up to adolescence on adolescents' cortisol stress response. The TRAILS study

OBJECTIVE

Altered cortisol response is a vulnerability marker for a variety of stress-related diseases and psychiatric disorders. Childhood adversity has been shown to modify this response, but evidence is inconsistent. Effects may differ depending on the timing of exposure, or due to the interplay between pre/postnatal adversity and later adversities. The present study examined the influence of adversity during different timeframes (pre/postnatal, ages 0-5, 6-11, 12-13, 14-15 years), and the interaction between pre/postnatal and later adversity on adolescents' cortisol stress response.

METHOD

Four salivary cortisol samples were collected before and after a social stress test in 471 16-year-old adolescents from the longitudinal study TRAILS. Data on pre/postnatal exposure to adversities were obtained from Preventive Child Healthcare records and parental reports, subsequent adversities from parental and self-reports.

RESULTS

Pre/postnatal adversity was associated with increased cortisol reactivity. Adversities during ages 0-5 were not associated with cortisol outcomes. Adversities during ages 6-11 were associated with a high cortisol level, especially in those exposed to pre/postnatal adversity, while adversities during ages 12-13 and 14-15 were associated with a low cortisol level.

CONCLUSIONS

Results highlight the importance to take the timing of stress exposure into account. In addition to programming effects, pre/postnatal adversity interacts with childhood adversity in producing deviant cortisol levels. Puberty may be marked by a transition in how adversities affect the HPA-axis, with cortisol hypersecretion before age 11 and hyposecretion after age 11.

Physiopathology of idiopathic nephrotic syndrome: lessons from glucocorticoids and epigenetic perspectives

Idiopathic nephrotic syndrome (INS) has been studied for decades in attempt to understand the physiopathological mechanisms explaining the disease. It is recognized as a multifactorial disease, with immunological components targeting kidney functions. Many hypotheses have been discussed or tested, including the role of a circulating factor, polymorphisms of genes implicated in lymphocyte maturation and differentiation, and DNA epigenetic modifications. In the present review, the data supporting these different (and probably combinatorial) hypotheses have been reviewed in order to identify and discuss the possible pathways implicated in the physiopathology of INS.

Epigenetic influences that modulate infant growth, development, and disease

SIGNIFICANCE

Epigenetic modifications are key processes in understanding normal human development and are largely responsible for the myriad cell and tissue types that originate from a single-celled fertilized ovum. The three most common processes involved in bringing about epigenetic changes are DNA methylation, histone modification, and miRNA effects. There are critical periods in the development of the zygote, the embryo, and the fetus where in the organism is most susceptible to epigenetic influences because of normal demethylation and de novo methylation processes that occur in the womb.

RECENT ADVANCES

A number of epigenetic modifications of normal growth patterns have been recognized, leading to altered development and disease states in the mammalian fetus and infant. 'Fetal programming' due to these epigenetic changes has been implicated in pathogenesis of adult-onset disease such as hypertension, diabetes, and cardiovascular disease. There may also be transgenerational effects of such epigenetic modifications.

CRITICAL ISSUES

The impact of environmental agents and endogenous factors such as stress at critical periods of infant development has immediate, life-long and even multi-generational effects. Both the timing and the degree of insult may be important. Understanding these influences may help prevent onset of disease and promote normal growth.

FUTURE DIRECTIONS

Use of one-carbon metabolism modifying agents such as folic acid during critical periods of epigenetic modulation may have significant clinical impact. Their use as therapeutic agents in targeted epigenetic modulation of genes may be the new frontier for clinical therapeutics.

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.

Crosstalk among Epigenetic Pathways Regulates Neurogenesis

The process of neurogenesis includes neural stem cell proliferation, fate specification, young neuron migration, neuronal maturation, and functional integration into existing circuits. Although neurogenesis occurs largely during embryonic development, low levels but functionally important neurogenesis persists in restricted regions of the postnatal brain, including the subgranular zone of the dentate gyrus in the hippocampus and the subventricular zone of the lateral ventricles. This review will cover both embryonic and adult neurogenesis with an emphasis on the latter. Of the many endogenous mediators of postnatal neurogenesis, epigenetic pathways, such as mediators of DNA methylation, chromatin remodeling systems, and non-coding RNA modulators, appear to play an integral role. Mounting evidence shows that such epigenetic factors form regulatory networks, which govern each step of postnatal neurogenesis. In this review, we explore the emerging roles of epigenetic mechanisms particularly microRNAs, element-1 silencing transcription factor/neuron-restrictive silencing factor (REST/NRSF), polycomb proteins, and methyl-CpG bindings proteins, in regulating the entire process of postnatal and adult neurogenesis. We further summarize recent data regarding how the crosstalk among these different epigenetic proteins forms the critical regulatory network that regulates neuronal development. We finally discuss how crosstalk between these pathways may serve to translate environmental cues into control of the neurogenic process.