Effects of antenatal synthetic glucocorticoid on glucocorticoid receptor binding, DNA methylation, and genome-wide mRNA levels in the fetal male hippocampus

Glucocorticoid effects on the brain: from adaptive developmental plasticity to allostatic overload

Exposure to stress during early life may alter the developmental trajectory of an animal by a mechanism known as adaptive plasticity. For example, to enhance reproductive success in an adverse environment, it is known that animals accelerate their growth during development. However, these short-term fitness benefits are often associated with reduced longevity, a phenomenon known as the growth rate-lifespan trade-off. In humans, early life stress exposure compromises health later in life and increases disease susceptibility. Glucocorticoids (GCs) are major stress hormones implicated in these processes. This Review discusses the evidence for GC-mediated adaptive plasticity in development, leading to allostatic overload in later life. We focus on GC-induced effects on brain structure and function, including neurogenesis; highlight the need for longitudinal studies; and discuss approaches to identify molecular mechanisms mediating GC-induced alteration of the brain developmental trajectory leading to adult dysfunctions. Further understanding of how stress and GC exposure can alter developmental trajectories at the molecular and cellular level is of critical importance to reduce the burden of mental and physical ill health across the life course.

Intergenerational Perioperative Neurocognitive Disorder

Accelerated neurocognitive decline after general anesthesia/surgery, also known as perioperative neurocognitive disorder (PND), is a widely recognized public health problem that may affect millions of patients each year. Advanced age, with its increasing prevalence of heightened stress, inflammation, and neurodegenerative alterations, is a consistent contributing factor to the development of PND. Although a strong homeostatic reserve in young adults makes them more resilient to PND, animal data suggest that young adults with pathophysiological conditions characterized by excessive stress and inflammation may be vulnerable to PND, and this altered phenotype may be passed to future offspring (intergenerational PND). The purpose of this narrative review of data in the literature and the authors' own experimental findings in rodents is to draw attention to the possibility of intergenerational PND, a new phenomenon which, if confirmed in humans, may unravel a big new population that may be affected by parental PND. In particular, we discuss the roles of stress, inflammation, and epigenetic alterations in the development of PND. We also discuss experimental findings that demonstrate the effects of surgery, traumatic brain injury, and the general anesthetic sevoflurane that interact to induce persistent dysregulation of the stress response system, inflammation markers, and behavior in young adult male rats and in their future offspring who have neither trauma nor anesthetic exposure (i.e., an animal model of intergenerational PND).

A case-control study on the effects of incomplete, one, and more than one dexamethasone course on acute respiratory problems in preterm neonates born between 280 and 366 weeks of gestation

OBJECTIVE

To compare the effects of an incomplete course and more than 1 course of dexamethasone, relative to a control of a single complete course, on foetal respiratory problems and other adverse outcomes of preterm birth.

METHODS

This was a retrospective chart review of 1800 women with preterm delivery. Data were collected on newborns whose mothers administered 1 full course of dexamethasone (916/1800; 50.9%), a partial course (716/1800; 39.8%) and more than 1 course (168/1800; 9.3%). Demographic data and adverse maternal and neonatal outcomes were recorded.

RESULTS

Preterm singleton newborns whose mothers received several steroid hormone courses were significantly more likely to have adverse outcomes than newborns of mothers given 1 course. The negative outcomes were the need for positive pressure ventilation ([aOR] 1.831; 95% CI, (1.185,2.829); P = 0.019), ventilator support ([aOR] 1.843; 95% CI, (1.187,2.861); P = 0.011), and phototherapy ([aOR] 1.997; 95% CI, (1.378,2.895); P <  0.001), transient tachypnoea of the newborn ([aOR] 1.801; 95% CI, (1.261,2.571); P = 0.002), intraventricular haemorrhage ([aOR] 2.215; 95% CI, (1.159, 4.233); P = 0.027), sepsis ([aOR] 1.737; 95% CI, (1.086, 2.777); P = 0.007), and admission to neonatal intensive care ([aOR] 1.822; 95% CI, (1.275,2.604); P = 0.001). In the group of very preterm infants, newborns of mothers administered an incomplete course had developed respiratory distress syndrome (RDS) ([aOR] 3.177; 95% CI, (1.485, 6.795); P = 0.006) and used ventilatory support ([aOR] 3.565; 95% CI, (1.912, 6.650); P <  0.001) more than those of mothers receiving a single course.

CONCLUSIONS

Preterm singleton newborns whose mothers were given multiple courses of dexamethasone had an increased incidence of RDS and other adverse outcomes than those of mothers receiving a full course. However, very preterm newborns whose mothers were administered 1 full dexamethasone course had a significantly lower incidence of RDS than those whose mothers were given partial courses.

Altered hippocampal GR/KCC2 signaling mediates susceptibility to convulsion in male offspring following dexamethasone exposure during pregnancy in rats

Epidemiological research suggests that convulsions may have an intrauterine developmental origin related to the application of dexamethasone, an artificially synthesized glucocorticoid. Here, using a rat animal model of prenatal dexamethasone exposure (PDE) we confirm that PDE can cause susceptibility to convulsions in male offspring and explore the epigenetic programming mechanism underlying this effect related to intrauterine type 2K⁺-Cl^- cotransporter (KCC2). Wistar rats were injected with dexamethasone (0.2mg/kg/d) subcutaneously during the gestational days (GD) 9-20 and part of the offspring was given lithium pilocarpine (LiPC) at postnatal week 10. Our results showed that male offspring of the PDE+LiPC group exhibited convulsions susceptibility, as well as increased hippocampal gamma-aminobutyric acid (GABA) and intracellular chloride ions level and decreased GABA receptor expression. The offspring also showed a decrease of hippocampal KCC2 H3K14ac levels and KCC2 expression. PDE male fetal rats (GD20) showed similar changes to male offspring after birth and exhibited an increased expression of glucocorticoid receptor (GR) and histone deacetylase type 2 (HDAC2). We observed effects consistent with those observed in PDE fetal rats following in vitro dexamethasone treatment of the fetal rat hippocampal neuron H19-7 cell line, and the effects could be reversed by treatment with a GR inhibitor (RU486) or HDAC2 inhibitor (romidepsin). Taken together, this study confirmed that PDE causes a reduction of H3K14ac levels in the KCC2 promoter region caused by activation of fetal hippocampal GR-HDAC2-KCC2 signaling. We proposed that this abnormal epigenetic modification is the mechanism underlying offspring convulsions susceptibility. CATEGORIES: mechanism of toxicity.

Transcriptome and Methylome Analysis Reveal Complex Cross-Talks between Thyroid Hormone and Glucocorticoid Signaling at Xenopus Metamorphosis

Background: Most work in endocrinology focus on the action of a single hormone, and very little on the cross-talks between two hormones. Here we characterize the nature of interactions between thyroid hormone and glucocorticoid signaling during Xenopus tropicalis metamorphosis. Methods: We used functional genomics to derive genome wide profiles of methylated DNA and measured changes of gene expression after hormonal treatments of a highly responsive tissue, tailfin. Clustering classified the data into four types of biological responses, and biological networks were modeled by system biology. Results: We found that gene expression is mostly regulated by either T₃ or CORT, or their additive effect when they both regulate the same genes. A small but non-negligible fraction of genes (12%) displayed non-trivial regulations indicative of complex interactions between the signaling pathways. Strikingly, DNA methylation changes display the opposite and are dominated by cross-talks. Conclusion: Cross-talks between thyroid hormones and glucocorticoids are more complex than initially envisioned and are not limited to the simple addition of their individual effects, a statement that can be summarized with the pseudo-equation: TH ∙ GC > TH + GC. DNA methylation changes are highly dynamic and buffered from genome expression.

Perinatal stress and epigenetics

Animal and humans exposed to stress early in life are more likely to suffer from long-term behavioral, mental health, metabolic, immune, and cardiovascular health consequences. The hypothalamus plays a nodal role in programming, controlling, and regulating stress responses throughout the life course. Epigenetic reprogramming in the hippocampus and the hypothalamus play an important role in adapting genome function to experiences and exposures during the perinatal and early life periods and setting up stable phenotypic outcomes. Epigenetic programming during development enables one genome to express multiple cell type identities. The most proximal epigenetic mark to DNA is a covalent modification of the DNA itself by enzymatic addition of methyl moieties. Cell-type-specific DNA methylation profiles are generated during gestational development and define cell and tissue specific phenotypes. Programming of neuronal phenotypes and sex differences in the hypothalamus is achieved by developmentally timed rearrangement of DNA methylation profiles. Similarly, other stations in the life trajectory such as puberty and aging involve predictable and scheduled reorganization of DNA methylation profiles. DNA methylation and other epigenetic marks are critical for maintaining cell-type identity in the brain, across the body, and throughout life. Data that have emerged in the last 15 years suggest that like its role in defining cell-specific phenotype during development, DNA methylation might be involved in defining experiential identities, programming similar genes to perform differently in response to diverse experiential histories. Early life stress impact on lifelong phenotypes is proposed to be mediated by DNA methylation and other epigenetic marks. Epigenetic marks, as opposed to genetic mutations, are reversible by either pharmacological or behavioral strategies and therefore offer the potential for reversing or preventing disease including behavioral and mental health disorders. This chapter discusses data testing the hypothesis that DNA methylation modulations of the HPA axis mediate the impact of early life stress on lifelong behavioral and physical phenotypes.

Spatial learning and memory deficits induced by prenatal glucocorticoid exposure depend on hippocampal CRHR1 and CXCL5 signaling in rats

Background

Prenatal synthetic glucocorticoid (sGC) exposure increases the susceptibility to cognitive and affective disorders in postnatal life. We previously demonstrated that prenatal sGC exposure results in an increase in corticotropin-releasing hormone (CRH) receptor type 1 (CRHR1) expression in the hippocampus of rats, and CRHR1 is involved in synapse formation via regulation of C-X-C chemokine ligand 5 (CXCL5) in hippocampus. We sought to investigate that the roles of CRHR1 and CXCL5 in learning and memory impairment caused by prenatal sGC exposure.

Methods

Pregnant rats were administered with saline or dexamethasone (DEX) from gestational day (GD) 14 to GD21. DEX offspring at 2-day old were treated with saline and CRHR1 antagonists (antalarmin and CP154526) for 7 days. Some DEX offspring received intra-hippocampal injection of AAV9 carrying CXCL5 gene. Spatial learning and memory was assessed by Morris water maze test. Immunofluorescence analysis was applied to show synapsin I and PSD95 signals in hippocampus. Synapsin I and PSD95 protein level and CXCL5 concentration were determined by western blotting and ELISA, respectively. Organotypic hippocampal slice cultures were used to investigate the effect of DEX on CXCL5 production in vitro.

Results

Both male and female DEX offspring displayed impairment of spatial learning and memory in adulthood. Synapsin I and PSD95 signals and CXCL5 levels were decreased in DEX offspring. DEX offspring with antalarmin and CP154526 treatment showed improved spatial learning and memory. Antalarmin and CP154526 treatment increased synapsin I and PSD95 signals and CXCL5 concentration in hippocampus. Bilaterally hippocampal injection of AAV9 carrying CXCL5 gene improved the spatial learning and memory and increased CXCL5 concentration and synapsin I and PSD95 levels in hippocampus. DEX dose-dependently suppressed CXCL5 production in cultured hippocammpal slices, which was prevented by antalarmin treatment.

Conclusion

CRHR1 and CXCL5 signaling in the hippocampus are involved in spatial learning and memory deficits caused by prenatal DEX exposure. CRHR1 activation contributes to decreased CXCL5 production in hippocampus induced by prenatal DEX treatment. Our study provides a molecular basis of prenatal GC exposure programming spatial learning and memory.

[Impact of the healthcare pathway on the rate of obstetrical interventions in small for gestational age fetuses (IATROPAG Study)]

BACKGROUND

While previous studies have demonstrated an improvement in implementation of clinical practices and an improved neonatal prognosis when growth restricted fetuses were followed within a standardized healthcare pathway, the objective of this study was to assess the prevalence of obstetric interventions in small-for-gestational-age (SGA) fetuses followed within a standardized care pathway compared to a traditional care pathway.

METHODS

We conducted a retrospective study between 2015 and 2017, in a type III maternity hospital in Lyon, in a population of SGA fetuses, considered as such in case of antenatal diagnosis of fetal weight<10th percentile but>3rd centile without umbilical Doppler abnormality during antenatal surveillance and without ultrasound argument suggesting intrauterine growth retardation (IUGR). We collected the gestational age at diagnosis, obstetrical events and prevention of preterm delivery (antenatal corticosteroids), gestation age at birth, the method of delivery (spontaneous or induced), indication of induction, the method of birth (spontaneous, instrumental extraction or caesarean section), and the immediate neonatal outcome including cord pH, Apgar score at 5minutes, birth weight and fetal sex. After diagnosis, the choice of the pathway was left to the practitioner depending on their habit, their ability to manage the follow-up and their organizational constraints.

RESULTS

Over the study period, and after exclusion of IUGR, 96 SGA were followed up in the traditional pathway and 106 SGA were followed up in the standardized pathway P=0.75. The traditional pathway showed in multivariate analysis a higher prevalence of antenatal corticosteroid therapy for SGA (16,6%) between 2015 and 2017 with OR 7.3 95% CI [1.41-38.43] when compared to the standardized pathway (3,7%). Similarly, the traditional pathway proposes a higher prevalence of induction of labor (54,1%) than the standardized pathway (33,9%) between 2015 and 2017 with OR 3.19 95% CI [1.70-7.80]. The "a posteriori" post-hoc power of the study is 82.9%.

CONCLUSION

This study confirms the absence of excessive obstetrical intervention in the SGA population when followed in a standardized healthcare pathway. The latter would reduce unnecessary obstetrical interventions while respecting the intrinsic neonatal prognosis of small for gestational age fetuses.

DNA methylome signatures of prenatal exposure to synthetic glucocorticoids in hippocampus and peripheral whole blood of female guinea pigs in early life

Synthetic glucocorticoids (sGC) are administered to women at risk of preterm delivery, approximately 10% of all pregnancies. In animal models, offspring exposed to elevated glucocorticoids, either by administration of sGC or endogenous glucocorticoids as a result of maternal stress, show increased risk of developing behavioral, endocrine, and metabolic dysregulation. DNA methylation may play a critical role in long-lasting programming of gene regulation underlying these phenotypes. However, peripheral tissues such as blood are often the only accessible source of DNA for epigenetic analyses in humans. Here, we examined the hypothesis that prenatal sGC administration alters DNA methylation signatures in guinea pig offspring hippocampus and whole blood. We compared these signatures across the two tissue types to assess epigenetic biomarkers of common molecular pathways affected by sGC exposure. Guinea pigs were treated with sGC or saline in late gestation. Genome-wide modifications of DNA methylation were analyzed at single nucleotide resolution using reduced representation bisulfite sequencing in juvenile female offspring. Results indicate that there are tissue-specific as well as common methylation signatures of prenatal sGC exposure. Over 90% of the common methylation signatures associated with sGC exposure showed the same directionality of change in methylation. Among differentially methylated genes, 134 were modified in both hippocampus and blood, of which 61 showed methylation changes at identical CpG sites. Gene pathway analyses indicated that prenatal sGC exposure alters the methylation status of gene clusters involved in brain development. These data indicate concordance across tissues of epigenetic programming in response to alterations in glucocorticoid signaling.

Impaired Oligodendrocyte Development Following Preterm Birth: Promoting GABAergic Action to Improve Outcomes

Preterm birth is associated with poor long-term neurodevelopmental and behavioral outcomes, even in the absence of obvious brain injury at the time of birth. In particular, behavioral disorders characterized by inattention, social difficulties and anxiety are common among children and adolescents who were born moderately to late preterm (32-37 weeks' gestation). Diffuse deficits in white matter microstructure are thought to play a role in these poor outcomes with evidence suggesting that a failure of oligodendrocytes to mature and myelinate axons is responsible. However, there remains a major knowledge gap over the mechanisms by which preterm birth interrupts normal oligodendrocyte development. In utero neurodevelopment occurs in an inhibitory-dominant environment due to the action of placentally derived neurosteroids on the GABA_A receptor, thus promoting GABAergic inhibitory activity and maintaining the fetal behavioral state. Following preterm birth, and the subsequent premature exposure to the ex utero environment, this action of neurosteroids on GABA_A receptors is greatly reduced. Coinciding with a reduction in GABAergic inhibition, the preterm neonatal brain is also exposed to ex utero environmental insults such as periods of hypoxia and excessive glucocorticoid concentrations. Together, these insults may increase levels of the excitatory neurotransmitter glutamate in the developing brain and result in a shift in the balance of inhibitory: excitatory activity toward excitatory. This review will outline the normal development of oligodendrocytes, how it is disrupted under excitation-dominated conditions and highlight how shifting the balance back toward an inhibitory-dominated environment may improve outcomes.

Early life variations in temperature exposure affect the epigenetic regulation of the paraventricular nucleus in female rat pups

Early life maternal care received has a profound effect on later-life behaviour in adult offspring, and previous studies have suggested epigenetic mechanisms are involved. Changes in thyroid hormone receptor signalling may be related to differences in maternal care received and DNA methylation modifications. We investigated the effects of variations in temperature exposure (a proxy of maternal contact) and licking-like tactile stimulation on these processes in week-old female rat pups. We assessed thyroid hormone receptor signalling by measuring circulating triiodothyronine and transcript abundance of thyroid hormone receptors and the thyroid hormone-responsive genes DNA methyltransferase 3a and oxytocin in the paraventricular nucleus of the hypothalamus. DNA methylation of the oxytocin promoter was assessed in relation to changes in thyroid hormone receptor binding. Repeated room temperature exposure was associated with a decrease in thyroid hormone receptor signalling measures relative to nest temperature exposure, while acute room temperature exposure was associated with an increase. Repeated room temperature exposure also increased thyroid hormone receptor binding and DNA methylation at the oxytocin promoter. These findings suggest that repeated room temperature exposure may affect DNA methylation levels as a consequence of alterations in thyroid hormone receptor signalling.

The epigenetics of perinatal stress

Early life adversity is associated with long-term effects on physical and mental health later in life, but the mechanisms are yet unclear. Epigenetic mechanisms program cell-type-specific gene expression during development, enabling one genome to be programmed in many ways, resulting in diverse stable profiles of gene expression in different cells and organs in the body. DNA methylation, an enzymatic covalent modification of DNA, has been one of the principal epigenetic mechanisms investigated. Emerging evidence is consistent with the idea that epigenetic processes are involved in embedding the impact of early-life experience in the genome and mediating between social environments and later behavioral phenotypes. Whereas there is evidence supporting this hypothesis in animal studies, human studies have been less conclusive. A major problem is the fact that the brain is inaccessible to epigenetic studies in humans and the relevance of DNA methylation in peripheral tissues to behavioral phenotypes has been questioned. In addition, human studies are usually confounded with genetic and environmental heterogeneity and it is very difficult to derive causality. The idea that epigenetic mechanisms mediate the life-long effects of perinatal adversity has attractive potential implications for early detection, prevention, and intervention in mental health disorders will be discussed.


Antenatal Corticosteroids for Fetal Lung Maturity - Too Much of a Good Thing?

BACKGROUND

Between 5-15% of babies are born prematurely worldwide, with preterm birth defined as delivery before 37 completed weeks of pregnancy (term is at 40 weeks of gestation). Women at risk of preterm birth receive antenatal corticosteroids as part of standard care to accelerate fetal lung maturation and thus improve neonatal outcomes in the event of delivery. As a consequence of this treatment, the entire fetal organ system is exposed to the administered corticosteroids. The implications of this exposure, particularly the long-term impacts on offspring health, are poorly understood.

AIMS

This review will consider the origins of antenatal corticosteroid treatment and variations in current clinical practices surrounding the treatment. The limitations in the evidence base supporting the use of antenatal corticosteroids and the evidence of potential harm to offspring are also summarised.

RESULTS

Little has been done to optimise the dose and formulation of antenatal corticosteroid treatment since the first clinical trial in 1972. International guidelines for the use of the treatment lack clarity regarding the recommended type of corticosteroid and the gestational window of treatment administration. Furthermore, clinical trials cited in the most recent Cochrane Review have limitations which should be taken into account when considering the use of antenatal corticosteroids in clinical practice. Lastly, there is limited evidence regarding the long-term effects on the different fetal organ systems exposed in utero, particularly when the timing of corticosteroid administration is sub-optimal.

CONCLUSION

Further investigations are urgently needed to determine the most safe and effective treatment regimen for antenatal corticosteroids, particularly regarding the type of corticosteroid and optimal gestational window of administration. A clear consensus on the use of this common treatment could maximise the benefits and minimise potential harms to offspring.

Perinatal compromise contributes to programming of GABAergic and glutamatergic systems leading to long-term effects on offspring behaviour

Extensive evidence now shows that adversity during the perinatal period is a significant risk factor for the development of neurodevelopmental disorders long after the causative event. Despite stemming from a variety of causes, perinatal compromise appears to have similar effects on the developing brain, thereby resulting in behavioural disorders of a similar nature. These behavioural disorders occur in a sex-dependent manner, with males affected more by externalising behaviours such as attention deficit hyperactivity disorder (ADHD) and females by internalising behaviours such as anxiety. Regardless of the causative event or the sex of the offspring, these disorders may begin in childhood or adolescence but extend into adulthood. A mechanism by which adverse events in the perinatal period impact later in life behaviour has been shown to be the changing epigenetic landscape. Methylation of the GAD1/GAD67 gene, which encodes the key glutamate-to-GABA-synthesising enzyme glutamate decarboxylase 1, resulting in increased levels of glutamate, is one epigenetic mechanism that may account for a tendency towards excitation in disorders such as ADHD. Exposure of the fetus or the neonate to high levels of cortisol may be the mediator between perinatal compromise and poor behavioural outcomes because evidence suggests that increased glucocorticoid exposure triggers widespread changes in the epigenetic landscape. This review summarises the current evidence and recent literature about the impact of various perinatal insults on the epigenome and the common mechanisms that may explain the similarity of behavioural outcomes occurring following diverse perinatal compromise.

Prenatal Glucocorticoid Exposure Results in Changes in Gene Transcription and DNA Methylation in the Female Juvenile Guinea Pig Hippocampus Across Three Generations

Synthetic glucocorticoids (sGC) are administered to women at risk for pre-term delivery, to mature the fetal lung and decrease neonatal morbidity. sGC also profoundly affect the fetal brain. The hippocampus expresses high levels of glucocorticoid (GR) and mineralocorticoid receptor (MR), and its development is affected by elevated fetal glucocorticoid levels. Antenatal sGC results in neuroendocrine and behavioral changes that persist in three generations of female guinea pig offspring of the paternal lineage. We hypothesized that antenatal sGC results in transgenerational changes in gene expression that correlate with changes in DNA methylation. We used RNASeq and capture probe bisulfite sequencing to investigate the transcriptomic and epigenomic effects of antenatal sGC exposure in the hippocampus of three generations of juvenile female offspring from the paternal lineage. Antenatal sGC exposure (F₀ pregnancy) resulted in generation-specific changes in hippocampal gene transcription and DNA methylation. Significant changes in individual CpG methylation occurred in RNApol II binding regions of small non-coding RNA (snRNA) genes, which implicates alternative splicing as a mechanism involved in transgenerational transmission of the effects of antenatal sGC. This study provides novel perspectives on the mechanisms involved in transgenerational transmission and highlights the importance of human studies to determine the longer-term effects of antenatal sGC on hippocampal-related function.

Developmental programming of the HPA axis and related behaviours: epigenetic mechanisms

It has been approximately 30 years since the seminal discoveries of David Barker and his colleagues, and research is beginning to unravel the mechanisms that underlie developmental programming. The early environment of the embryo, foetus and newborn have been clearly linked to altered hypothalamic-pituitary-adrenal (HPA) function and related behaviours through the juvenile period and into adulthood. A number of recent studies have shown that these effects can pass across multiple generations. The HPA axis is highly responsive to the environment, impacts both central and peripheral systems and is critical to health in a wide variety of contexts. Mechanistic studies in animals are linking early exposures to adversity with changes in gene regulatory mechanisms, including modifications of DNA methylation and altered levels of miRNA. Similar associations are emerging from recent human studies. These findings suggest that epigenetic mechanisms represent a fundamental link between adverse early environments and developmental programming of later disease. The underlying biological mechanisms that connect the perinatal environment with modified long-term health outcomes represent an intensive area of research. Indeed, opportunities for early interventions must identify the relevant environmental factors and their molecular targets. This new knowledge will likely assist in the identification of individuals who are at risk of developing poor outcomes and for whom early intervention is most effective.

Antenatal Synthetic Glucocorticoid Exposure at Human Therapeutic Equivalent Doses Predisposes Middle-Age Male Offspring Baboons to an Obese Phenotype That Emerges With Aging

INTRODUCTION

Women threatening premature delivery receive synthetic glucocorticoids (sGC) to accelerate fetal lung maturation, reducing neonatal mortality and morbidity. Few investigations have explored potential long-term offspring side effects. We previously reported increased pericardial fat and liver lipids in 10-year-old (human equivalent 40 years) male baboons exposed to 3 antenatal sGC courses. We hypothesized middle-aged sGC male offspring show obesity-related morphometric changes.

METHODS

Pregnant baboons received courses of 2 betamethasone injections (175 μg·kg-1·d-1 intramuscular) at 0.6, 0.64, and 0.68 gestation. At 10 to 12.5 years, we measured morphometrics and serum lipids in 5 sGC-exposed males and 10 age-matched controls. We determined whether morphometric parameters predicted amount of pericardial fat or lipids. Life-course serum lipids were measured in 25 males (7-23 years) providing normal regression formulas to compare sGC baboons' lipid biological and chronological age.

RESULTS

Birth weights were similar. When studied, sGC-exposed males showed a steeper weight increase from 8 to 12 years and had increased waist and hip circumferences, neck and triceps skinfolds, and total and low-density lipoprotein cholesterol. Triceps skinfold correlated with apical and midventricular pericardial fat thickness, hip and waist circumferences with insulin.

CONCLUSIONS

Triceps skinfold and waist and hip circumferences are useful biomarkers for identifying individuals at risk for obesity and metabolic dysregulation following fetal sGC exposure. Prenatal sGC exposure predisposes male offspring to internal adiposity, greater body size, and increased serum lipids. Results provide further evidence for developmental programming by fetal sGC exposure and call attention to potential emergence of adverse life-course effects.

Combined Antioxidant and Glucocorticoid Therapy for Safer Treatment of Preterm Birth

Ante- and postnatal glucocorticoid therapy reduces morbidity and mortality in the preterm infant, and it is therefore one of the best examples of the successful translation of basic experimental science into human clinical practice. However, accruing evidence derived from human clinical studies and from experimental studies in animal models raise serious concerns about potential long-term adverse effects of treatment on growth and neurological and cardiovascular function in the offspring. This review explores whether combined antioxidant and glucocorticoid therapy may be safer than glucocorticoid therapy alone for the treatment of preterm birth.

Prenatal programming of stress responsiveness and behaviours: Progress and perspectives

Parental exposure to stress or glucocorticoids either before or during pregnancy can have profound influences on neurodevelopment, neuroendocrine function and behaviours in offspring. Specific outcomes are dependent on the nature, intensity and timing of the exposure, as well as species, sex and age of the subject. Most recently, it has become evident that outcomes are not confined to first-generation offspring and that there may be intergenerational and transgenerational transmission of effects. There has been intense focus on the mechanisms by which such early exposure leads to long-term and potential transgenerational outcomes, and there is strong emerging evidence that epigenetic processes (histone modifications, DNA methylation, and small non-coding RNAs) are involved. New knowledge in this area may allow the development of interventions that can prevent, ameliorate or reverse the long-term negative outcomes associated with exposure to early adversity. This review will focus on the latest research, bridging human and pre-clinical studies, and will highlight some of the limitations, challenges and gaps that exist in the field.

Genome-wide epigenetic signatures of childhood adversity in early life: Opportunities and challenges

Maternal adversity and fetal glucocorticoid exposure has long-term effects on cardiovascular, metabolic and behavioral systems in offspring that can persist throughout the lifespan. These data, along with other environmental exposure data, implicate epigenetic modifications as potential mechanisms for long-term effects of maternal exposures on adverse health outcomes in offspring. Advances in microarray, sequencing and bioinformatic approaches have enabled recent studies to examine the genome-wide epigenetic response to maternal adversity. Studies of maternal exposures to xenobiotics such as arsenic and smoking have been performed at birth to examine fetal epigenomic signatures in cord blood relating to adult health outcomes. However, there have been no epigenomic studies examining these effects in animal models. On the other hand, to date, only a few studies of the effects of maternal psychosocial stress have been performed in human infants, and the majority of animal studies have examined epigenomic outcomes in adulthood. In terms of maternal exposure to excess glucocorticoids by synthetic glucocorticoid treatment, there has been no epigenetic study performed in humans and only a few studies undertaken in animal models. This review emphasizes the importance of examining biomarkers of exposure to adversity throughout development to identify individuals at risk and to target interventions. Thus, research performed at birth will be reviewed. In addition, potential subject characteristics associated with epigenetic modifications, technical considerations, the selection of target tissues and combining human studies with animal models will be discussed in relation to the design of experiments in this field of study.

Full versus half dose of antenatal betamethasone to prevent severe neonatal respiratory distress syndrome associated with preterm birth: study protocol for a randomised, multicenter, double blind, placebo-controlled, non-inferiority trial (BETADOSE)

BACKGROUND

Although antenatal betamethasone is recommended worldwide for women at risk of preterm delivery, concerns persist regarding the long-term effects associated with this treatment. Indeed, adverse events, mainly dose-related, have been reported. The current recommended dose of antenatal betamethasone directly derives from sheep experiments performed in the late 60's and has not been challenged in 45 years. Therefore, randomized trials evaluating novel dose regimens are urgently needed.

METHODS

A randomised, double blind, placebo-controlled, non-inferiority trial will be performed in 37 French level 3 maternity units. Women with a singleton pregnancy at risk of preterm delivery before 32 weeks of gestation having already received a first 11.4 mg injection of betamethasone will be randomised to receive either a second injection of 11.4 mg betamethasone (full dose arm) or placebo (half dose arm) administered intramuscularly 24 h after the first injection. The primary binary outcome will be the occurrence of severe respiratory distress syndrome (RDS), defined as the need for exogenous intra-tracheal surfactant in the first 48 h of life. Considering that 20% of the pregnant women receiving the full dose regimen would have a neonate with severe RDS, 1571 patients in each treatment group are required to show that the half dose regimen is not inferior to the full dose, that is the difference in severe RDS rate do not exceed 4% (corresponding to a Relative Risk of 20%), with a 1-sided 2.5% type-1 error and a 80% power. Interim analyses will be done after every 300 neonates who reach the primary outcome on the basis of intention-to-treat, using a group-sequential non-inferiority design.

DISCUSSION

If the 50% reduced antenatal betamethasone dose is shown to be non-inferior to the full dose to prevent severe RDS associated with preterm birth, then it should be used consistently in women at risk of preterm delivery and would be of great importance to their children.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT 02897076 (registration date 09/13/2016).

Antenatal Glucocorticoid Exposure Results in Sex-Specific and Transgenerational Changes in Prefrontal Cortex Gene Transcription that Relate to Behavioural Outcomes

Synthetic glucocorticoids (sGC) are administered to women at risk for pre-term delivery to reduce respiratory distress syndrome in the newborn. The prefrontal cortex (PFC) is important in regulating stress responses and related behaviours and expresses high levels of glucocorticoid receptors (GR). Further, antenatal exposure to sGC results in a hyperactive phenotype in first generation (F₁) juvenile male and female offspring, as well as F₂ and F₃ juvenile females from the paternal lineage. We hypothesized that multiple courses of antenatal sGC modify gene expression in the PFC, that these effects are sex-specific and maintained across multiple generations, and that the gene sets affected relate to modified locomotor activity. We performed RNA sequencing on PFC of F₁ juvenile males and females, as well as F₂ and F₃ juvenile females from the paternal lineage and used regression modelling to relate gene expression and behavior. Antenatal sGC resulted in sex-specific and generation-specific changes in gene expression. Further, the expression of 4 genes (C9orf116, Calb1, Glra3, and Gpr52) explained 20–29% of the observed variability in locomotor activity. Antenatal exposure to sGC profoundly influences the developing PFC; effects are evident across multiple generations and may drive altered behavioural phenotypes.

Fetal glucocorticoid receptor (Nr3c1) deficiency alters the landscape of DNA methylation of murine placenta in a sex-dependent manner and is associated to anxiety-like behavior in adulthood

Prenatal stress defines long-term phenotypes through epigenetic programming of the offspring. These effects are potentially mediated by glucocorticoid release and by sex. We hypothesized that the glucocorticoid receptor (Gr, Nr3c1) fashions the DNA methylation profile of offspring. Consistent with this hypothesis, fetal Nr3c1 heterozygosity leads to altered DNA methylation landscape in fetal placenta in a sex-specific manner. There was a significant overlap of differentially methylated genes in fetal placenta and adult frontal cortex in Nr3c1 heterozygotes. Phenotypically, Nr3c1 heterozygotes show significantly more anxiety-like behavior than wildtype. DNA methylation status of fetal placental tissue is significantly correlated with anxiety-like behavior of the same animals in adulthood. Thus, placental DNA methylation might predict behavioral phenotypes in adulthood. Our data supports the hypothesis that Nr3c1 influences DNA methylation at birth and that DNA methylation in placenta correlates with adult frontal cortex DNA methylation and anxiety-like phenotypes.

Guinea pig models for translation of the developmental origins of health and disease hypothesis into the clinic

Over 30 years ago Professor David Barker first proposed the theory that events in early life could explain an individual's risk of non-communicable disease in later life: the developmental origins of health and disease (DOHaD) hypothesis. During the 1990s the validity of the DOHaD hypothesis was extensively tested in a number of human populations and the mechanisms underpinning it characterised in a range of experimental animal models. Over the past decade, researchers have sought to use this mechanistic understanding of DOHaD to develop therapeutic interventions during pregnancy and early life to improve adult health. A variety of animal models have been used to develop and evaluate interventions, each with strengths and limitations. It is becoming apparent that effective translational research requires that the animal paradigm selected mirrors the tempo of human fetal growth and development as closely as possible so that the effect of a perinatal insult and/or therapeutic intervention can be fully assessed. The guinea pig is one such animal model that over the past two decades has demonstrated itself to be a very useful platform for these important reproductive studies. This review highlights similarities in the in utero development between humans and guinea pigs, the strengths and limitations of the guinea pig as an experimental model of DOHaD and the guinea pig's potential to enhance clinical therapeutic innovation to improve human health.

Improving pregnancy outcomes in humans through studies in sheep

Experimental studies that are relevant to human pregnancy rely on the selection of appropriate animal models as an important element in experimental design. Consideration of the strengths and weaknesses of any animal model of human disease is fundamental to effective and meaningful translation of preclinical research. Studies in sheep have made significant contributions to our understanding of the normal and abnormal development of the fetus. As a model of human pregnancy, studies in sheep have enabled scientists and clinicians to answer questions about the etiology and treatment of poor maternal, placental, and fetal health and to provide an evidence base for translation of interventions to the clinic. The aim of this review is to highlight the advances in perinatal human medicine that have been achieved following translation of research using the pregnant sheep and fetus.

Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: An Endocrine Society Clinical Practice Guideline

Objective

To update the congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency clinical practice guideline published by the Endocrine Society in 2010.

Conclusions

The writing committee presents updated best practice guidelines for the clinical management of congenital adrenal hyperplasia based on published evidence and expert opinion with added considerations for patient safety, quality of life, cost, and utilization.

Antenatal corticosteroids: an assessment of anticipated benefits and potential risks

Antenatal corticosteroids are standard of care for pregnancies at risk of preterm delivery between 24-34 weeks' gestational age. Recent trials demonstrate modest benefits from antenatal corticosteroids for late preterm and elective cesarean deliveries, and antenatal corticosteroids for periviable deliveries should be considered with family discussion. However, many women with threatened preterm deliveries receive antenatal corticosteroids but do not deliver until >34 weeks or at term. The net effect is that a substantial fraction of the delivery population will be exposed to antenatal corticosteroids. There are gaps in accurate assessments of benefits of antenatal corticosteroids because the randomized controlled trials were performed prior to about 1990 in pregnancies generally >28 weeks. The care practices for the mother and infant survival were different than today. The randomized controlled trial data also do not strongly support the optimal interval from antenatal corticosteroid treatment to delivery of 1-7 days. Epidemiology-based studies using large cohorts with >85% of at-risk pregnancies treated with antenatal corticosteroids probably overestimate the benefits of antenatal corticosteroids. Although most of the prematurity-associated mortality is in low-resource environments, the efficacy and safety of antenatal corticosteroids in those environments remain to be evaluated. The short-term benefits of antenatal corticosteroids for high-risk pregnancies in high-resource environments certainly justify antenatal corticosteroids as few risks have been identified over many years. However, cardiovascular and metabolic abnormalities have been identified in large animal models and cohorts of children exposed to antenatal corticosteroids that are consistent with fetal programming for adult diseases. These late effects of antenatal corticosteroids suggest caution for the expanded use of antenatal corticosteroids beyond at-risk pregnancies at 24-34 weeks. A way forward is to develop noninvasive fetal assessments to identify pregnancies across a wider gestational age that could benefit from antenatal corticosteroids.

Corticosteroids and perinatal hypoxic-ischemic brain injury

Perinatal hypoxic-ischemic (HI) brain injury is the major cause of neonatal mortality and severe long-term neurological morbidity. Yet, the effective therapeutic interventions currently available are extremely limited. Corticosteroids act on both mineralocorticoid (MR) and glucocorticoid (GR) receptors and modulate inflammation and apoptosis in the brain. Neuroinflammatory response to acute cerebral HI is a major contributor to the pathophysiology of perinatal brain injury. Here, we give an overview of current knowledge of corticosteroid-mediated modulations of inflammation and apoptosis in the neonatal brain, focusing on key regulatory cells of the innate and adaptive immune response. In addition, we provide new insights into targets of MR and GR in potential therapeutic strategies that could be beneficial for the treatment of infants with HI brain injury.

CRH/CRHR1 mediates prenatal synthetic glucocorticoid programming of depression-like behavior across 2 generations

Pregnant women at risk of preterm labor usually receive synthetic glucocorticoids (sGCs) to promote fetal lung development. Emerging evidence indicates that antenatal sGC increases the risk of affective disorders in offspring. Data from animal studies show that such disorders can be transmitted to the second generation. However, the molecular mechanisms underlying the intergenerational effects of prenatal sGC remain largely unknown. Here we show that prenatal dexamethasone (Dex) administration in late pregnancy induced depression-like behavior in first-generation (F1) offspring, which could be transmitted to second-generation (F2) offspring with maternal dependence. Moreover, corticotropin-releasing hormone (CRH) and CRH receptor type 1 (CRHR1) expression in the hippocampus was increased in F1 Dex offspring and F2 offspring from F1 Dex female rats. Administration of a CRHR1 antagonist to newborn F1 Dex offspring alleviated depression-like behavior in these rats at adult. Furthermore, we demonstrated that increased CRHR1 expression in F1 and F2 offspring was associated with hypomethylation of CpG islands in Crhr1 promoter. Our results revealed that prenatal sGC exposure could program Crh and Crhr1 gene expression in hippocampus across 2 generations, thereby leading to depression-like behavior. Our study indicates that prenatal sGC can cause epigenetic instability, which increases the risk of disease development in the offspring's later life.-Xu, Y.-J., Sheng, H., Wu, T.-W., Bao, Q.-Y., Zheng, Y., Zhang, Y.-M., Gong, Y.-X., Lu, J.-Q., You, Z.-D., Xia, Y., Ni, X. CRH/CRHR1 mediates prenatal synthetic glucocorticoid programming of depression-like behavior across 2 generations.

Deficiency of dietary pyridoxine disturbed the intestinal physical barrier function of young grass carp (Ctenopharyngodon idella)

The aim of this study was to assess the effects of dietary pyridoxine (PN) deficiency on intestinal antioxidant capacity, cell apoptosis and intercellular tight junction in young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp (231.85 ± 0.63 g) were fed six diets containing graded levels of PN (0.12-7.48 mg/kg diet) for 10 weeks. At the end of the feeding trial, the fish were challenged with Aeromonas hydrophila for 2 weeks. The results showed that compared with the optimal PN level, PN deficiency (1) increased the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC), decreased the activities and mRNA levels of antioxidant enzymes such as copper, zinc superoxide dismutase (CuZnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR) (P < .05); (2) up-regulated the mRNA levels of cysteinyl aspartic acid-protease-3 (caspase-3), caspase-7, caspase-8, caspase-9, Bcl-2 associated X protein (Bax), apoptotic protease activating factor-1 (Apaf-1) and Fas ligand (FasL), and down-regulated the mRNA levels of inhibitor of apoptosis proteins (IAP), B-cell lymphoma protein-2 (Bcl-2) and myeloid cell leukaemia-1 (Mcl-1) (P < .05); (3) down-regulated the mRNA levels of ZO-1, occludin [only in middle intestine (MI)], claudin-b, claudin-c, claudin-f, claudin-3c, claudin-7a, claudin-7b and claudin-11, and up-regulated the mRNA levels of claudin-12 and claudin-15a (P < .05), which might be partly linked to Kelch-like-ECH-associated protein 1a (Keap1a)/NF-E2-related factor 2 (Nrf2), p38 mitogen-activated protein kinase (p38MAPK) and myosin light chain kinase (MLCK) signalling in the intestines of fish. However, the activities and mRNA levels of MnSOD, the mRNA levels of Keap1b, c-Jun N-terminal protein kinase (JNK) and claudin-15b in three intestinal segments, and the mRNA levels of occludin in the proximal intestine (PI) and distal intestine (DI) were not affected by graded levels of PN. These data indicate that PN deficiency could disturb the intestinal physical barrier function of fish. Additionally, based on the quadratic regression analysis for MDA content and GST activity, the dietary PN requirements for young grass carp were estimated as 4.85 and 5.02 mg/kg diet, respectively.

Prenatal Stress, Glucocorticoids, and Developmental Programming of the Stress Response

The early environment has a major impact on the developing embryo, fetus, and infant. Parental adversity (maternal and paternal) and glucocorticoid exposure before conception and during pregnancy have profound effects on the development and subsequent function of the hypothalamic-pituitary-adrenal axis and related behaviors. These effects are species-, sex-, and age-specific and depend on the timing and duration of exposure. The impact of these early exposures can extend across multiple generations, via both the maternal and paternal lineage, and recent studies have begun to determine the mechanisms by which this occurs. Improved knowledge of the mechanisms by which adversity and glucocorticoids program stress systems will allow development of strategies to ameliorate and/or reverse these long-term effects.

Prenatal Administration of Betamethasone Causes Changes in the T Cell Receptor Repertoire Influencing Development of Autoimmunity

Prenatal glucocorticoids are routinely administered to pregnant women at risk of preterm delivery in order to improve survival of the newborn. However, in half of the cases, birth occurs outside the beneficial period for lung development. Glucocorticoids are potent immune modulators and cause apoptotic death of immature T cells, and we have previously shown that prenatal betamethasone treatment at doses eliciting lung maturation induce profound thymocyte apoptosis in the offspring. Here, we asked if there are long-term consequences on the offspring’s immunity after this treatment. In the non-obese diabetic mouse model, prenatal betamethasone clearly decreased the frequency of pathogenic T cells and the incidence of type 1 diabetes (T1D). In contrast, in the lupus-prone MRL/lpr strain, prenatal glucocorticoids induced changes in the T cell repertoire that resulted in more autoreactive cells. Even though glucocorticoids transiently enhanced regulatory T cell (Treg) development, these cells did not have a protective effect in a model for multiple sclerosis which relies on a limited repertoire of pathogenic T cells for disease induction that were not affected by prenatal betamethasone. We conclude that prenatal steroid treatment, by inducing changes in the T cell receptor repertoire, has unforeseeable consequences on development of autoimmune disease. Our data should encourage further research to fully understand the consequences of this widely used treatment.

Prenatal Glucocorticoid Exposure Modifies Endocrine Function and Behaviour for 3 Generations Following Maternal and Paternal Transmission

Fetal exposure to high levels of glucocorticoids programs long-term changes in the physiologic stress response and behaviours. However, it is not known whether effects manifest in subsequent generations of offspring following maternal (MT) or paternal (PT) transmission. We treated pregnant guinea pigs with three courses of saline or synthetic glucocorticoid (sGC) at a clinically relevant dose. Altered cortisol response to stress and behaviours transmitted to juvenile female and male F2 and F3 offspring from both parental lines. Behavioural effects of sGC in F1-F3 PT females associated with altered expression of genes in the prefrontal cortex and hypothalamic paraventricular nucleus (PVN). Exposure to sGC programmed large transgenerational changes in PVN gene expression, including type II diabetes, thermoregulation, and collagen formation gene networks. We demonstrate transgenerational programming to F3 following antenatal sGC. Transmission is sex- and generation-dependent, occurring through both parental lines. Paternal transmission to F3 females strongly implicates epigenetic mechanisms of transmission.

Epigenomics of Major Depressive Disorders and Schizophrenia: Early Life Decides

Brain development is guided by the interactions between the genetic blueprint and the environment. Epigenetic mechanisms, especially DNA methylation, can mediate these interactions and may also trigger long-lasting adaptations in developmental programs that increase the risk of major depressive disorders (MDD) and schizophrenia (SCZ). Early life adversity is a major risk factor for MDD/SCZ and can trigger persistent genome-wide changes in DNA methylation at genes important to early, but also to mature, brain function, including neural proliferation, differentiation, and synaptic plasticity, among others. Moreover, genetic variations controlling dynamic DNA methylation in early life are thought to influence later epigenomic changes in SCZ. This finding corroborates the high genetic load and a neurodevelopmental origin of SCZ and shows that epigenetic responses to the environment are, at least in part, genetically controlled. Interestingly, genetic variants influencing DNA methylation are also enriched in risk variants from genome-wide association studies (GWAS) on SCZ supporting a role in neurodevelopment. Overall, epigenomic responses to early life adversity appear to be controlled to different degrees by genetics in MDD/SCZ, even though the potential reversibility of epigenomic processes may offer new hope for timely therapeutic interventions in MDD/SCZ.

Dietary zinc deficiency reduced growth performance, intestinal immune and physical barrier functions related to NF-κB, TOR, Nrf2, JNK and MLCK signaling pathway of young grass carp (Ctenopharyngodon idella)

Our study investigated the effects of dietary zinc (Zn) deficiency on growth performance, intestinal immune and physical barrier functions of young grass carp (Ctenopharyngodon idella). A total of 630 grass carp (244.14 ± 0.40 g) were fed graded levels of zinc lactate (10.71, 30.21, 49.84, 72.31, 92.56, 110.78 mg Zn/kg diet) and one zinc sulfate group (56.9 mg Zn/kg diet) for 60 days. At the end of the feeding trial, fish were challenged with Aeromonas hydrophila for 14 days. These results indicated that compared with optimal dietary Zn level, dietary Zn deficiency (10.71 mg/kg diet) decreased the production of antibacterial compounds, up-regulated pro-inflammatory cytokines related to nuclear factor kappa B (NF-κB) and down-regulated anti-inflammatory cytokines related to target of rapamycin (TOR) in three intestinal segments of young grass carp (P < 0.05), suggesting that dietary Zn deficiency could impair intestinal immune barrier of fish; decreased the activities and mRNA levels of antioxidant enzymes related to NF-E2-related factor 2 (Nrf2), up-regulated the mRNA levels of caspase-3, -7, -8, -9 related to p38 mitogen activated protein (p38 MAPK) and c-Jun N-terminal protein kinase (JNK), down-regulated the mRNA levels of tight junction complexes (TJs) related to myosin light chain kinase (MLCK) in three intestinal segments of young grass carp (P < 0.05), demonstrating that dietary Zn deficiency could injury intestinal physical barrier of fish. Besides, the Zn requirements (zinc lactate as Zn source) based on percent weight gain (PWG), against enteritis morbidity, acid phosphatase (ACP) activity in the proximal intestine (PI) and malondialdehyde (MDA) content in the PI of young grass carp was estimated to be 61.2, 61.4, 69.2 and 69.5 mg/kg diet, respectively. Finally, based on specific growth rate (SGR), feed efficiency (FE) and against enteritis morbidity of young grass carp, the efficacy of zinc lactate relative to zinc sulfate were 132.59%, 135.27% and 154.04%, respectively.

Cord Blood DNA Methylation Biomarkers for Predicting Neurodevelopmental Outcomes

Adverse environmental exposures in pregnancy can significantly alter the development of the fetus resulting in impaired child neurodevelopment. Such exposures can lead to epigenetic alterations like DNA methylation, which may be a marker of poor cognitive, motor and behavioral outcomes in the infant. Here we review studies that have assessed DNA methylation in cord blood following maternal exposures that may impact neurodevelopment of the child. We also highlight some key studies to illustrate the potential for DNA methylation to successfully identify infants at risk for poor outcomes. While the current evidence is limited, in that observations to date are largely correlational, in time and with larger cohorts analyzed and longer term follow-up completed, we may be able to develop epigenetic biomarkers that not only indicate adverse early life exposures but can also be used to identify individuals likely to be at an increased risk of impaired neurodevelopment even in the absence of detailed information regarding prenatal environment.

Prenatal Dexamethasone and Postnatal High-Fat Diet Decrease Interferon Gamma Production through an Age-Dependent Histone Modification in Male Sprague-Dawley Rats

Overexposure to prenatal glucocorticoid (GC) disturbs hypothalamic-pituitary-adrenocortical axis-associated neuroendocrine metabolism and susceptibility to metabolic syndrome. A high-fat (HF) diet is a major environmental factor that can cause metabolic syndrome. We aimed to investigate whether prenatal GC plus a postnatal HF diet could alter immune programming in rat offspring. Pregnant Sprague-Dawley rats were given intraperitoneal injections of dexamethasone or saline at 14-21 days of gestation. Male offspring were then divided into four groups: vehicle, prenatal dexamethasone exposure, postnatal HF diet (VHF), and prenatal dexamethasone exposure plus a postnatal HF diet (DHF). The rats were sacrificed and adaptive immune function was evaluated. Compared to the vehicle, the DHF group had lower interferon gamma (IFN-γ) production by splenocytes at postnatal day 120. Decreases in H3K9 acetylation and H3K36me3 levels at the IFN-γ promoter correlated with decreased IFN-γ production. The impaired IFN-γ production and aberrant site-specific histone modification at the IFN-γ promoter by prenatal dexamethasone treatment plus a postnatal HF diet resulted in resilience at postnatal day 180. Prenatal dexamethasone and a postnatal HF diet decreased IFN-γ production through a site-specific and an age-dependent histone modification. These findings suggest a mechanism by which prenatal exposure to GC and a postnatal environment exert effects on fetal immunity programming.

Programming of stress pathways: A transgenerational perspective

The embryo and fetus are highly responsive to the gestational environment. Glucocorticoids (GC) represent an important class of developmental cues and are crucial for normal brain development. Levels of GC in the fetal circulation are tightly regulated. They are maintained at low levels during pregnancy, and increase rapidly at the end of gestation. This surge in GC is critical for maturation of the organs, specifically the lungs, brain and kidney. There are extensive changes in brain epigenetic profiles that accompany the GC surge, suggesting that GC may drive regulation of gene transcription through altered epigenetic pathways. The epigenetic profiles produced by the GC surge can be prematurely induced as a result of maternal or fetal stress, as well as through exposure to synthetic glucocorticoids (sGC). This is highly clinically relevant as 10% of pregnant women are at risk for preterm labour and receive treatment with sGC to promote lung development in the fetus. Fetal overexposure to GC (including sGC) has been shown to cause lasting changes in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis leading to altered stress responses, and mood and anxiety disorders in humans and animals. In animal models, GC exposure is associated with transcriptomic and epigenomic changes that influence behaviour, HPA function and growth. Importantly, programming by GC results in sex-specific effects that can be inherited over multiple generations via paternal and maternal transmission.

Epigenome-Microbiome crosstalk: A potential new paradigm influencing neonatal susceptibility to disease

Preterm birth is the leading cause of infant morbidity and mortality. Necrotizing enterocolitis (NEC) is an inflammatory bowel disease affecting primarily premature infants, which can be lethal. Microbial intestinal colonization may alter epigenetic signatures of the immature gut establishing inflammatory and barrier properties predisposing to the development of NEC. We hypothesize that a crosstalk exists between the epigenome of the host and the initial intestinal colonizing microbiota at critical neonatal stages. By exposing immature enterocytes to probiotic and pathogenic bacteria, we showed over 200 regions of differential DNA modification, which were specific for each exposure. Reciprocally, using a mouse model of prenatal exposure to dexamethasone we demonstrated that antenatal treatment with glucocorticoids alters the epigenome of the host. We investigated the effects on the expression profiles of genes associated with inflammatory responses and intestinal barrier by qPCR-based gene expression array and verified the DNA modification changes in 5 candidate genes by quantitative methylation specific PCR (qMSP). Importantly, by 16S RNA sequencing-based phylogenetic analysis of intestinal bacteria in mice at 2 weeks of life, we showed that epigenome changes conditioned early microbiota colonization leading to differential bacterial colonization at different taxonomic levels. Our findings support a novel conceptual framework in which epigenetic changes induced by intrauterine influences affect early microbial colonization and intestinal development, which may alter disease susceptibility.

Stress In Utero: Prenatal Programming of Brain Plasticity and Cognition

Animal studies confirm earlier anecdotal observations in humans to indicate that early life experience has a profound impact on adult behavior, years after the original experience has vanished. These studies also highlight the role of early life adversaries in the shaping of a disordered brain. Evidence is accumulating to indicate that the epigenome, through which the environment regulates gene expression, is responsible for long-lasting effects of stress during pregnancy on brain and behavior. A possible differential effect of the environment on the epigenome may underlie the observation that only a small fraction of a population with similar genetic background deteriorates into mental disorders. Considerable progress has been made in the untangling of the epigenetic mechanisms that regulate emotional brain development. The present review focuses on the lasting effects of prenatal stress on brain plasticity and cognitive functions in human and rodent models. Although human studies stress the significance of early life experience in functional maturation, they lack the rigor inherent in controlled animal experiments. Furthermore, the analysis of molecular and cellular mechanisms affected by prenatal stress is possible only in experimental animals. The present review attempts to link human and animal studies while proposing molecular mechanisms that interfere with functional brain development.

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.

Fetal endocrine therapy for congenital adrenal hyperplasia should not be done

Prenatal treatment of congenital adrenal hyperplasia by administering dexamethasone to a woman presumed to be carrying an at-risk fetus remains a controversial experimental treatment. Review of data from animal experimentation and human trials indicates that dexamethasone cannot be considered safe for the fetus. In animals, prenatal dexamethasone decreases birth weight, affects renal, pancreatic beta cell and brain development, increases anxiety and predisposes to adult hypertension and hyperglycemia. In human studies, prenatal dexamethasone is associated with orofacial clefts, decreased birth weight, poorer verbal working memory, and poorer self-perception of scholastic and social competence. Numerous medical societies have cautioned that prenatal treatment of adrenal hyperplasia with dexamethasone is not appropriate for routine clinical practice and should only be done in Institutional Review Board approved, prospective clinical research settings with written informed consent. The data indicate that this treatment is inconsistent with the classic medical ethical maxim to 'first do no harm'.

Gestational Diabetes Alters Offspring DNA Methylation Profiles in Human and Rat: Identification of Key Pathways Involved in Endocrine System Disorders, Insulin Signaling, Diabetes Signaling, and ILK Signaling

Gestational diabetes is associated with risk for metabolic disease later in life. Using a cross-species approach in rat and humans, we examined the hypothesis that gestational diabetes during pregnancy triggers changes in the methylome of the offspring that might be mediating these risks. We show in a gestation diabetes rat model, the Cohen diabetic rat, that gestational diabetes triggers wide alterations in DNA methylation in the placenta in both candidate diabetes genes and genome-wide promoters, thus providing evidence for a causal relationship between diabetes during pregnancy and DNA methylation alterations. There is a significant overlap between differentially methylated genes in the placenta and the liver of the rat offspring. Several genes differentially methylated in rat placenta exposed to maternal diabetes are also differentially methylated in the human placenta of offspring exposed to gestational diabetes in utero. DNA methylation changes inversely correlate with changes in expression. The changes in DNA methylation affect known functional gene pathways involved in endocrine function, metabolism, and insulin responses. These data provide support to the hypothesis that early-life exposures and their effects on metabolic disease are mediated by DNA methylation changes. This has important diagnostic and therapeutic implications.

Dexamethasone Treatment of Newborn Rats Decreases Cardiomyocyte Endowment in the Developing Heart through Epigenetic Modifications

The potential adverse effect of synthetic glucocorticoid, dexamethasone therapy on the developing heart remains unknown. The present study investigated the effects of dexamethasone on cardiomyocyte proliferation and binucleation in the developing heart of newborn rats and evaluated DNA methylation as a potential mechanism. Dexamethasone was administered intraperitoneally in a three day tapered dose on postnatal day 1 (P1), 2 and 3 to rat pups in the absence or presence of a glucocorticoid receptor antagonist Ru486, given 30 minutes prior to dexamethasone. Cardiomyocytes from P4, P7 or P14 animals were analyzed for proliferation, binucleation and cell number. Dexamethasone treatment significantly increased the percentage of binucleated cardiomyocytes in the hearts of P4 pups, decreased myocyte proliferation in P4 and P7 pups, reduced cardiomyocyte number and increased the heart to body weight ratio in P14 pups. Ru486 abrogated the effects of dexamethasone. In addition, 5-aza-2'-deoxycytidine (5-AZA) blocked the effects of dexamethasone on binucleation in P4 animals and proliferation at P7, leading to recovered cardiomyocyte number in P14 hearts. 5-AZA alone promoted cardiomyocyte proliferation at P7 and resulted in a higher number of cardiomyocytes in P14 hearts. Dexamethasone significantly decreased cyclin D2, but not p27 expression in P4 hearts. 5-AZA inhibited global DNA methylation and blocked dexamethasone-mediated down-regulation of cyclin D2 in the heart of P4 pups. The findings suggest that dexamethasone acting on glucocorticoid receptors inhibits proliferation and stimulates premature terminal differentiation of cardiomyocytes in the developing heart via increased DNA methylation in a gene specific manner.

From receptor balance to rational glucocorticoid therapy

Corticosteroids secreted as end product of the hypothalamic-pituitary-adrenal axis act like a double-edged sword in the brain. The hormones coordinate appraisal processes and decision making during the initial phase of a stressful experience and promote subsequently cognitive performance underlying the management of stress adaptation. This action exerted by the steroids on the initiation and termination of the stress response is mediated by 2 related receptor systems: mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs). The receptor types are unevenly distributed but colocalized in abundance in neurons of the limbic brain to enable these complementary hormone actions. This contribution starts from a historical perspective with the observation that phasic occupancy of GR during ultradian rhythmicity is needed to maintain responsiveness to corticosteroids. Then, during stress, initially MR activation enhances excitability of limbic networks that are engaged in appraisal and emotion regulation. Next, the rising hormone concentration occupies GR, resulting in reallocation of energy to limbic-cortical circuits with a role in behavioral adaptation and memory storage. Upon MR:GR imbalance, dysregulation of the hypothalamic-pituitary-adrenal axis occurs, which can enhance an individual's vulnerability. Imbalance is characteristic for chronic stress experience and depression but also occurs during exposure to synthetic glucocorticoids. Hence, glucocorticoid psychopathology may develop in susceptible individuals because of suppression of ultradian/circadian rhythmicity and depletion of endogenous corticosterone from brain MR. This knowledge generated from testing the balance hypothesis can be translated to a rational glucocorticoid therapy.

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.