Prenatal dexamethasone programs expression of genes in liver and adipose tissue and increased hepatic lipid accumulation but not obesity on a high-fat diet

Diminished 11β-hydroxysteroid dehydrogenase type 2 activity is associated with decreased weight and weight gain across the first year of life

CONTEXT

Low birth weight is associated with adverse metabolic outcome in adulthood. Exposure to glucocorticoid (GC) excess in utero is associated with decreased birth weight, but the prospective longitudinal relationship between GC metabolism and growth has not been examined.

OBJECTIVE

We have hypothesized that changes in GC metabolism leading to increased availability may impair growth.

DESIGN

This was a prospective, longitudinal study with clinical measurements and 24-hour urinary steroid metabolite analysis at 1, 4, 12, 26, and 52 weeks after delivery in mothers and their babies.

SETTING

The study was conducted with observations and samples collected in the volunteers' own homes.

PARTICIPANTS

Healthy mothers and newborn babies/infants participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Urinary steroid metabolite excretion quantified by gas chromatography/mass spectroscopy across the first year of life in relation to change in weight was measured.

RESULTS

The total production of the GC metabolites quantified increased across the first year of life. Markers of 11β-hydroxysteroid dehydrogenase type 1 activity increased from the age of 3 months as did those of 5α-reductase activity. After correcting for confounding variables, low markers of 11β-hydroxysteroid dehydrogenase type 2 activity was associated with reduced absolute weight and decreased weight gain over the first year of life. In the mothers, 5α-reductase activity was low at birth and progressively increased to normal over the first 6 months postpartum.

CONCLUSIONS

Increased GC exposure as a consequence of reduced 11β-hydroxysteroid dehydrogenase type 2 activity is likely to be a critical determinant of growth in early life. This not only highlights the central role of GCs and their metabolism, but also emphasizes the need for detailed longitudinal analyses.

Melatonin in the regulation of liver steatosis following prenatal glucocorticoid exposure

Nonalcoholic fatty liver disease patients are characterized by hepatic steatosis. Prenatal glucocorticoid overexposure can result in steatosis. In this study, we aimed to determine the mechanism and cellular apoptosis of prenatal glucocorticoid overexposure in rats and whether melatonin can rescue the prenatal glucocorticoid-induced steatosis and apoptosis in neonatal rats. Pregnant Sprague-Dawley rats at gestational days 14 to 21 were administered dexamethasone. Acute effects of prenatal programming liver were assessed at postnatal day 7. The expression of proteins involved in the apoptotic and methylation pathways was analyzed by RT-PCR and Western blotting. Apoptosis and steatosis were examined by histology staining. The liver steatosis and apoptosis were increased in prenatal glucocorticoid group more than in control group and decreased in melatonin group. The expression of leptin decreased in prenatal glucocorticoid and increased in melatonin group by liver RT-PCR and Western blot study. Caspase 3, TNF-α proteins expression, and TUNEL stains increased in prenatal glucocorticoid compared with control and decreased in melatonin group. The liver histone deacetylase, DNA methyltransferase activity, and DNA methylation were increased in prenatal glucocorticoid and decreased in melatonin group. The present study showed that the prenatal glucocorticoid induced programming liver steatosis at day 7 after delivery, possibly via altered leptin expression. Melatonin can reverse the methylation of leptin and decreased liver steatosis.

Chronic high-fat diet increases acute neuroendocrine stress response independently of prenatal dexamethasone treatment in male rats

OBJECTIVE

Intrauterine growth restriction (IUGR) has been associated with metabolic disorders later in life such as obesity and diabetes as well as psychiatric disorders such as depression and schizophrenia. Therefore, we wanted to investigate whether behavioural, metabolic or neuroendocrine abnormalities could be provoked or exacerbated by a high-fat diet (HFD) in an experimental model of IUGR.

METHODS

Pregnant dams were exposed to dexamethasone (DEX) in the third gestational week to induce IUGR. Late adolescent male offspring of DEX- and vehicle-treated dams were then fed a HFD or standard chow for 8 weeks and subjected to a variety of assessments.

RESULTS

Only diet affected the hypothalamus-pituitary-adrenal (HPA) axis stress response, as HFD doubled the observed corticosterone levels following acute restraint. HFD and prenatal DEX exposure concomitantly exacerbated depressive-like behaviour in the forced swim test, even though no interaction was seen. Prenatal DEX treatment tended to increase the basal acoustic startle response (ASR), while an interaction between HFD and DEX was present in the ASR pre-pulse inhibition suggestive of fundamental changes in neuronal gating mechanisms. Metabolic parameters were only affected by diet, as HFD increased fasting glucose and insulin levels.

CONCLUSION

We conclude that chronic HFD may be more important in programming of the HPA axis stress responsiveness than an adverse foetal environment and therefore potentially implies an increased risk for developing psychiatric and metabolic disease.

Early-Life Stress, HPA Axis Adaptation, and Mechanisms Contributing to Later Health Outcomes

Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, which then modulates the degree of adaptation and response to a later stressor. It is known that early-life stress can impact on later health but less is known about how early-life stress impairs HPA axis activity, contributing to maladaptation of the stress-response system. Early-life stress exposure (either prenatally or in the early postnatal period) can impact developmental pathways resulting in lasting structural and regulatory changes that predispose to adulthood disease. Epidemiological, clinical, and experimental studies have demonstrated that early-life stress produces long term hyper-responsiveness to stress with exaggerated circulating glucocorticoids, and enhanced anxiety and depression-like behaviors. Recently, evidence has emerged on early-life stress-induced metabolic derangements, for example hyperinsulinemia and altered insulin sensitivity on exposure to a high energy diet later in life. This draws our attention to the contribution of later environment to disease vulnerability. Early-life stress can alter the expression of genes in peripheral tissues, such as the glucocorticoid receptor and 11-beta hydroxysteroid dehydrogenase (11β-HSD1). We propose that interactions between altered HPA axis activity and liver 11β-HSD1 modulates both tissue and circulating glucocorticoid availability, with adverse metabolic consequences. This review discusses the potential mechanisms underlying early-life stress-induced maladaptation of the HPA axis, and its subsequent effects on energy utilization and expenditure. The effects of positive later environments as a means of ameliorating early-life stress-induced health deficits, and proposed mechanisms underpinning the interaction between early-life stress and subsequent detrimental environmental exposures on metabolic risk will be outlined. Limitations in current methodology linking early-life stress and later health outcomes will also be addressed.

Disruption of fetal hormonal programming (prenatal stress) implicates shared risk for sex differences in depression and cardiovascular disease

Comorbidity of major depressive disorder (MDD) and cardiovascular disease (CVD) represents the fourth leading cause of morbidity and mortality worldwide, and women have a two times greater risk than men. Thus understanding the pathophysiology has widespread implications for attenuation and prevention of disease burden. We suggest that sex-dependent MDD-CVD comorbidity may result from alterations in fetal programming consequent to the prenatal maternal environments that produce excess glucocorticoids, which then drive sex-dependent developmental alterations of the fetal hypothalamic-pituitary-adrenal (HPA) axis circuitry impacting mood, stress regulation, autonomic nervous system (ANS), and the vasculature in adulthood. Evidence is consistent with the hypothesis that disruptions of pathways associated with gamma aminobutyric acid (GABA) in neuronal and vascular development and growth factors have critical roles in key developmental periods and adult responses to injury in heart and brain. Understanding the potential fetal origins of these sex differences will contribute to development of novel sex-dependent therapeutics.

Nutritional manipulations in the perinatal period program adipose tissue in offspring

Epidemiological studies demonstrated initially that maternal undernutrition results in low birth weight with increased risk for long-lasting energy balance disorders. Maternal obesity and diabetes associated with high birth weight, excessive nutrition in neonates, and rapid catchup growth also increase the risk of adult-onset obesity. As stated by the Developmental Origin of Health and Disease concept, nutrient supply perturbations in the fetus or neonate result in long-term programming of individual body weight set point. Adipose tissue is a key fuel storage unit involved mainly in the maintenance of energy homeostasis. Studies in numerous animal models have demonstrated that the adipose tissue is the focus of developmental programming events in a sex- and depot-specific manner. In rodents, adipose tissue development is particularly active during the perinatal period, especially during the last week of gestation and during early postnatal life. In contrast to rodents, this process essentially takes place before birth in bigger mammals. Despite these different developmental time windows, altricial and precocial species share several mechanisms of adipose tissue programming. Offspring from malnourished dams present adipose tissue with a series of alterations: impaired glucose uptake, insulin and leptin resistance, low-grade inflammation, modified sympathetic activity with reduced noradrenergic innervations, and thermogenesis. These modifications reprogram adipose tissue metabolism by changing fat distribution and composition and by enhancing adipogenesis, predisposing the offspring to fat accumulation. Subtle adipose tissue circadian rhythm changes are also observed. Inappropriate hormone levels, modified tissue sensitivity (especially glucocorticoid system), and epigenetic mechanisms are key factors for adipose tissue programming during the perinatal period.

Pomegranate vinegar attenuates adiposity in obese rats through coordinated control of AMPK signaling in the liver and adipose tissue

BACKGROUND

The effect of pomegranate vinegar (PV) on adiposity was investigated in high-fat diet (HF)-induced obese rats.

METHODS

The rats were divided into 5 groups and treated with HF with PV or acetic acid (0, 6.5 or 13% w/w) for 16 weeks. Statistical analyses were performed by the Statistical Analysis Systems package, version 9.2.

RESULTS

Compared to control, PV supplementation increased phosphorylation of AMP-activated protein kinase (AMPK), leading to changes in mRNA expressions: increases for hormone sensitive lipase and mitochondrial uncoupling protein 2 and decreases for sterol regulatory element binding protein-1c (SREBP-1c) and peroxisome proliferator-activated receptorγ (PPARγ) in adipose tissue; increases for PPARα and carnitinepalmitoyltransferase-1a (CPT-1a) and decrease for SREBP-1c in the liver. Concomitantly, PV reduced increases of body weight (p = 0.048), fat mass (p = 0.033), hepatic triglycerides (p = 0.005), and plasma triglycerides (p = 0.001).

CONCLUSIONS

These results suggest that PV attenuates adiposity through the coordinated control of AMPK, which leads to promotion of lipolysis in adipose tissue and stimulation of fatty acid oxidation in the liver.

Maternal hypoxia increases the susceptibility of adult rat male offspring to high-fat diet-induced nonalcoholic fatty liver disease

Exposure to an adverse intrauterine environment increases the risk for adult metabolic syndrome. However, the influence of prenatal hypoxia on the risk of fatty liver disease in offspring is unclear. The purpose of the present study was to evaluate the role of reduced fetal oxygen on the development and severity of high-fat (HF) diet-induced nonalcoholic fatty liver disease (NAFLD). Based on design implicating 2 factors, ie, maternal hypoxia (MH) and postnatal HF diet, blood lipid and insulin levels, hepatic histology, and potential molecular targets were evaluated in male Sprague Dawley rat offspring. MH associated with postnatal HF diet caused a significant increase in plasma concentration of triglycerides, free fatty acids, low-density lipoprotein cholesterol, and insulin. Histologically, a more severe form of NAFLD with hepatic inflammation, hepatic resident macrophage infiltration, and progression toward nonalcoholic steatohepatitis was observed. The lipid homeostasis changes and insulin resistance caused by MH plus HF were accompanied by a significant down-regulation of insulin receptor substrate 2 (IRS-2), phosphoinositide-3 kinase p110 catalytic subunit, and protein kinase B. In MH rats, insulin-stimulated IRS-2 and protein kinase B (AKT) phosphorylation were significantly blunted as well as insulin suppression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Meanwhile, a significant up-regulation of lipogenic pathways was noticed, including sterol-regulatory element-binding protein-1 and fatty acid synthase in liver. Our results indicate that maternal hypoxia enhances dysmetabolic liver injury in response to an HF diet. Therefore, the offspring born in the context of maternal hypoxia may require special attention and follow-up to prevent the early development of NAFLD.

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

The endogenous glucocorticoid (GC) surge in late gestation plays a vital role in maturation of several organ systems. For this reason, pregnant women at risk of preterm labor are administered synthetic glucocorticoids (sGCs) to promote fetal lung development. Animal studies have shown that fetal sGC exposure can cause life-long changes in endocrine and metabolic function. We have previously shown that antenatal sGC treatment is associated with alterations in global DNA methylation and modifications to the hippocampal methylome and acetylome. In this study, we hypothesized that: 1) there are changes in the transcriptional landscape of the fetal hippocampus in late gestation, associated with the endogenous cortisol surge; 2) fetal sGC exposure alters genome-wide transcription in the hippocampus; and 3) these changes in transcription are associated with modified glucocorticoid receptor (GR) DNA binding and DNA methylation. sGC was administered as 2 courses on gestational days (GD) 40, 41, 50, and 51, and the hippocampi of fetal guinea pigs were examined before (GD52) and after (GD65) the endogenous cortisol surge (Term ∼GD67). We also analyzed fetal hippocampi 24 hours and 14 days following maternal sGC injections (n = 3-4/group). Genome-wide modification of transcription and GR DNA binding occurred in late gestation, in parallel with the normal GC surge. Further, sGC exposure had a substantial impact on the hippocampal transcriptome, GR-DNA binding, and DNA methylation at 24 hours and 14 days following the final sGC treatment. These data support the hypothesis that GC exposure in late gestation plays a significant role in modifying the transcriptional and epigenetic landscape of the developing fetal hippocampus and that substantial effects are evident for at least 2 weeks after sGC exposure.

Postnatal dietary omega-3 fatty acid supplementation rescues glucocorticoid-programmed adiposity, hypertension, and hyperlipidemia in male rat offspring raised on a high-fat diet

Fetal glucocorticoid excess programs several adverse outcomes in adult offspring, many of which can be prevented by postnatal, dietary omega-3 (n-3) fatty acids. Here we tested 2 separate hypotheses: 1) a postnatal high-fat diet exacerbates the glucocorticoid-programmed phenotype; and 2) postnatal, dietary n-3 fatty acids rescue programmed outcomes, even in the presence of a high-fat diet challenge. Pregnant Wistar rat dams were either untreated or administered dexamethasone acetate (Dex; 0.5 μg/mL drinking water) from day 13 of pregnancy. Offspring were cross-fostered to untreated mothers and males were weaned onto a standard (Std), high-fat, low n-3 (HF), or high-fat, high n-3 (HFHn-3) diet. Prenatal Dex reduced birth weight (26%) and delayed puberty onset by 1.2 days, irrespective of postnatal diet. Prenatal Dex programmed increased blood pressure in adult offspring, an effect worsened by the postnatal HF diet. Supplementation with high n-3 fatty acids, however, prevented both the Dex and HF-induced increases in blood pressure. Prenatal Dex also programmed increased adiposity, plasma cholesterol, and plasma triglyceride levels at 6 months of age, particularly in those offspring raised on the HF diet. But again, each of these adverse outcomes was rescued by supplementation of the HF diet with n-3 fatty acids. In conclusion, the capacity of n-3 fatty acids to overcome adverse programming outcomes remains evident, even in the presence of a HF diet challenge.

Short- and long-term effects of exposure to natural and synthetic glucocorticoids during development

1.Glucocorticoids (GCs) are necessary for fetal development, but clinical and experimental studies suggest that excess exposure may be detrimental to health in both the short and longer term. 2.Exposure of the fetus to synthetic GCs can occur if the mother has a medical condition requiring GC therapy (e.g. asthma) or if she threatens to deliver her baby prematurely. Synthetic GCs can readily cross the placenta and treatment is beneficial, at least in the short term, for maternal health and fetal survival. 3.Maternal stress during pregnancy can raise endogenous levels of the natural GC cortisol. A significant proportion of the cortisol is inactivated by the placental 'GC barrier'. However, exposure to severe stress during pregnancy can result in increased risk of miscarriage, low birth weight and behavioural deficits in children. 4.Animal studies have shown that excess exposure to both synthetic and natural GCs can alter normal organ development, including that of the heart, brain and kidney. The nature and severity of the organ impairment is dependent upon the timing of exposure and, in some cases, the type of GC used and the sex of the fetus. 5.In animal models, exposure to elevated GCs during pregnancy has been associated with adult-onset diseases, including elevated blood pressure, impaired cardiac and vascular function and altered metabolic function.

Sex-specific effects of prenatal stress on glucose homoeostasis and peripheral metabolism in rats

Glucocorticoid overexposure during pregnancy programmes offspring physiology and predisposes to later disease. However, any impact of ethologically relevant maternal stress is less clear, yet of physiological importance. Here, we investigated in rats the short- and long-term effects in adult offspring of repeated social stress (exposure to an aggressive lactating female) during late pregnancy on glucose regulation following stress, glucose-insulin homoeostasis and peripheral expression of genes important in regulating glucose and lipid metabolism and glucocorticoid action. Prenatal stress (PNS) was associated with reduced birth weight in female, but not male, offspring. The increase in blood glucose with restraint was exaggerated in adult PNS males compared with controls, but not in females. Oral glucose tolerance testing showed no effects on plasma glucose or insulin concentrations in either sex at 3 months; however, at 6 months, PNS females were hyperinsulinaemic following an oral glucose load. In PNS males, plasma triglyceride concentrations were increased, with reduced hepatic mRNA expression of 5α-reductase and peroxisome proliferator-activated receptor α (Pparα (Ppara)) and a strong trend towards reduced peroxisome proliferator-activated receptor gamma coactivator 1α (Pgc1α (Ppargc1a)) and Pparγ (Pparg) expression, whereas only Pgc1α mRNA was affected in PNS females. Conversely, in subcutaneous fat, PNS reduced mRNA expression of 11β-hydroxysteroid dehydrogenase type 1 (11βhsd1), phosphoenolpyruvate carboxykinase (Pepck (Pck1)), adipose triglyceride lipase (Atgl) and diglyceride acyltransferase 2 (Dgat2) in females, but only Pepck mRNA expression was reduced in PNS males. Thus, prenatal social stress differentially programmes glucose homoeostasis and peripheral metabolism in male and female offspring. These long-term alterations in physiology may increase susceptibility to metabolic disease.

Impact of antenatal glucocorticosteroids on whole-genome expression in preterm babies

AIM

To study the impact that using antenatal steroid to treat threatened preterm delivery has on whole-genome expression.

METHODS

A prospective whole-genome expression study was carried out on 50 newborn infants, delivered before 32 weeks gestation, who had been exposed to antenatal steroids, including 40 who had received a full antenatal steroid course. Seventy infants not exposed to antenatal steroids formed the control group. Microarray analyses were performed five and 28 days after delivery, and the results were validated by real-time PCR. The study was conducted between September 2008 and November 2010.

RESULTS

Twenty thousand six hundred and ninety-three genes were studied in the infants' leucocytes. Thirteen were differentially expressed 5 days after delivery, but there were no differences at day 28. Four genes related to cancer or inflammation were up-regulated. Nine genes were down-regulated: six were Y-linked and associated with malignancies, graft-versus-host disease, male infertility and cell differentiation and three were associated with pre-eclampsia, oxidative stress and chloride/bicarbonate exchange. Seven gene pathways were up-regulated at day five and only one at day 28. These were associated with cell growth, cell cycle regulation, metabolism and apoptosis.

CONCLUSION

Antenatal steroid therapy affects a limited number of genes and gene pathways in leucocytes in preterm babies at day five of life. The effect is short-lived, but long-term effects cannot be ruled out.

Prenatal stress increases the obesogenic effects of a high-fat-sucrose diet in adult rats in a sex-specific manner

Stress during pregnancy can induce metabolic disorders in adult offspring. To analyze the possible differential response to a high-fat-sucrose (HFS) diet in offspring affected by prenatal stress (PNS) or not, pregnant Wistar rats (n = 11) were exposed to a chronic mild stress during the third week of gestation. The aim of this study was to model a chronic depressive-like state that develops over time in response to exposure of rats to a series of mild and unpredictable stressors. Control dams (n = 11) remained undisturbed. Adult offspring were fed chow or HFS diet (20% protein, 35% carbohydrate, 45% fat) for 10 weeks. Changes in adiposity, biochemical profile, and retroperitoneal adipose tissue gene expression by real-time polymerase chain reaction were analyzed. An interaction was observed between HFS and PNS concerning visceral adiposity, with higher fat mass in HFS-fed stressed rats, statistically significant only in females. HFS modified lipid profile and increased insulin resistance biomarkers, while PNS reduced insulin concentrations and the homeostasis model assessment index. HFS diet increased gene (mRNA) expression for leptin and apelin and decreased cyclin-dependent kinase inhibitor 1A and fatty acid synthase (Fasn), whereas PNS increased Fasn and stearoyl-CoA desaturase1. An interaction between diet and PNS was observed for adiponutrin (Adpn) and peroxisome proliferator-activated receptor-γ coactivator1-α (Ppargc1a) gene expression: Adpn was increased by the PNS only in HFS-fed rats, whereas Ppargc1a was increased by the PNS only in chow-fed rats. From these results, it can be concluded that experience of maternal stress during intrauterine development can enhance predisposition to obesity induced by a HFS diet intake.

Glucocorticoid programming of the fetal male hippocampal epigenome

The late-gestation surge in fetal plasma cortisol is critical for maturation of fetal organ systems. As a result, synthetic glucocorticoids (sGCs) are administered to pregnant women at risk of delivering preterm. However, animal studies have shown that fetal exposure to sGC results in increased risk of behavioral, endocrine, and metabolic abnormalities in offspring. Here, we test the hypothesis that prenatal GC exposure resulting from the fetal cortisol surge or after sGC exposure results in promoter-specific epigenetic changes in the hippocampus. Fetal guinea pig hippocampi were collected before (gestational day [GD52]) and after (GD65) the fetal plasma cortisol surge (Term∼GD67) and 24 hours after (GD52) and 14 days after (GD65) two repeat courses of maternal sGC (betamethasone) treatment (n = 3-4/gp). We identified extensive genome-wide alterations in promoter methylation in late fetal development (coincident with the fetal cortisol surge), whereby the majority of the affected promoters exhibited hypomethylation. Fetuses exposed to sGC in late gestation exhibited substantial differences in DNA methylation and histone h3 lysine 9 (H3K9) acetylation in specific gene promoters; 24 hours after the sGC treatment, the majority of genes affected were hypomethylated or hyperacetylated. However, 14 days after sGC exposure these differences did not persist, whereas other promoters became hypermethylated or hyperacetylated. These data support the hypothesis that the fetal GC surge is responsible, in part, for significant variations in genome-wide promoter methylation and that prenatal sGC treatment profoundly changes the epigenetic landscape, affecting both DNA methylation and H3K9 acetylation. This is important given the widespread use of sGC in the management of women in preterm labor.

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

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

Glucocorticoids as mediators of developmental programming effects

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

Prepro-thyrotropin releasing hormone expressing neurons in the juxtaparaventricular region of the lateral hypothalamus are activated by leptin and altered by prenatal glucocorticoid exposure

The neuropeptide thyrotropin-releasing hormone (TRH) is recognized to play an important role in controlling energy balance through direct effects on the CNS, although mechanisms explaining the phenomenon are poorly understood. To begin to understand the effects of TRH on CNS control of energy balance, we first mapped neurons expressing the TRH precursor peptide, prepro-TRH (ppTRH) in the paraventricular nucleus of the rat hypothalamus and the surrounding regions. We identified a population of ppTRH-expressing neurons in the juxtaparaventricular region of the lateral hypothalamus (LHAjp) which were stimulated by the satiety signal leptin (2.5μg/kg, IP). Using a model of fetal glucocorticoid (GC) exposure in which pregnant rats were treated with the synthetic GC dexamethasone (DEX) during gestational days 18-21, it was observed that such exposure resulted in reduced numbers of ppTRH-ir neurons in the LHAjp in adult male and female rats, and was accompanied by increased food intake. Our data provide further insight into the biological role of the LHAjp, as well as the potential involvement of TRH neurons within this region in metabolic disease associated with fetal glucocorticoid exposure.

Exposure to dexamethasone during late gestation causes female-specific decreases in core body temperature and prepro-thyrotropin-releasing hormone expression in the paraventricular nucleus of the hypothalamus in rats

Synthetic glucocorticoids (GC) have been used to promote lung development in preterm infants, thereby decreasing respiratory distress syndrome and mortality, yet, concern has arisen from reports that such treatment predisposes individuals to disease in adulthood. Given the variety of preclinical studies that show metabolic and behavioral abnormalities in adulthood following fetal exposure to synthetic GC, we examined the effect of in utero exposure to the synthetic GC, dexamethasone (DEX), on hypothalamic expression of thyrotropin-releasing hormone (TRH) a central neuropeptide involved in mediating behavior and metabolic balance. Pregnant Sprague-Dawley rats were administered 0.4mg/kg DEX on gestational days 18-21. As adults (postnatal day (PD) 60), the offspring were fitted with temperature sensing transmitters allowing real-time monitoring of core body temperature (CBT) across the 24h light dark period. This revealed a significant decrease in CBT throughout the day in prenatal DEX-treated females on estrus and diestrus, but not in male offspring. The reduction in CBT by prenatal DEX exposure was accompanied by a significant decrease in the expression of Trh transcript in the paraventricular nucleus of the hypothalamus (PVN) of female rats at PD 60 and this effect was also present on PD7. There was also a female-specific reduction in the number of preproTRH-immunoreactive (ir) neurons in the PVN, with ppTRH-ir nerve fibers decreases that were present in both male and female offspring. No changes in thyroid hormone (triiodothyronine, T3; thyroxine, T4) were observed in adult offspring, but during development, both males and females (PD14) had lower T3 and T4 levels. These data indicate abnormal expression of TRH results from fetal DEX exposure during late gestation, possibly explaining the decreased CBT observed in the female offspring.

Prenatal synthetic glucocorticoid treatment changes DNA methylation states in male organ systems: multigenerational effects

Prenatal synthetic glucocorticoids (sGC) are administered to pregnant women at risk of delivering preterm, approximately 10% of all pregnancies. Animal studies have demonstrated that offspring exposed to elevated glucocorticoids, either by administration of sGC or as a result of maternal stress, are at increased risk of developing behavioral, endocrine, and metabolic abnormalities. DNA methylation is a covalent modification of DNA that plays a critical role in long-lasting programming of gene expression. Here we tested the hypothesis that prenatal sGC treatment has both acute and long-term effects on DNA methylation states in the fetus and offspring and that these effects extend into a subsequent generation. Pregnant guinea pigs were treated with sGC in late gestation, and methylation analysis by luminometric methylation assay was undertaken in organs from fetuses and offspring across two generations. Expression of genes that modify the epigenetic state were measured by quantitative real-time PCR. Results indicate that there are organ-specific developmental trajectories of methylation in the fetus and newborn. Furthermore, these trajectories are substantially modified by intrauterine exposure to sGC. These sGC-induced changes in DNA methylation remain into adulthood and are evident in the next generation. Furthermore, prenatal sGC exposure alters the expression of several genes encoding proteins that modulate the epigenetic state. Several of these changes are long lasting and are also present in the next generation. These data support the hypothesis that prenatal sGC exposure leads to broad changes in critical components of the epigenetic machinery and that these effects can pass to the next generation.

Prenatal dexamethasone exposure potentiates diet-induced hepatosteatosis and decreases plasma IGF-I in a sex-specific fashion

The clinical use of synthetic glucocorticoids in preterm infants to promote lung development has received considerable attention due to the potential for increased risk of developing metabolic disease in adulthood after such treatment. In this study, we examined the hypothesis that exposure to the synthetic glucocorticoid, dexamethasone (DEX), during late gestation in the rat results in the development of nonalcoholic fatty liver disease in adult offspring. Pregnant Sprague Dawley dams were treated with 0.4 mg/kg DEX beginning on gestational d 18 until parturition (gestational d 23). At postnatal d 21, offspring were weaned onto either a standard chow or high-fat (60% fat-derived calories) diet. In adulthood (postnatal d 60-65), hepatic tissue was harvested and examined for pathology. Liver steatosis, or fat accumulation, was found to be more severe in the DEX-exposed female offspring that were weaned onto the high-fat diet. This finding corresponded with decreased plasma IGF-I concentrations, as well as decreased hypothalamic expression of GHRH mRNA. Morphological measurements on body and long bone length further implicate a GH signaling deficit after fetal DEX exposure. Collectively, these data indicate suppression of GH axis function in the female DEX/high-fat cohort but not in the male offspring. Because deficits in the GH signaling can be linked to the development of nonalcoholic fatty liver disease, our results suggest that the prominent liver injury noted in female offspring exposed to DEX during late gestation may stem from abnormal development of the GH axis at the hypothalamic level.

Maternal prenatal undernutrition programs adipose tissue gene expression in adult male rat offspring under high-fat diet

Several studies have shown that maternal undernutrition leading to low birth weight predisposes offspring to the development of metabolic pathologies such as obesity. Using a model of prenatal maternal 70% food restriction diet (FR30) in rat, we evaluated whether postweaning high-fat (HF) diet would amplify the phenotype observed under standard diet. We investigated biological parameters as well as gene expression profile focusing on white adipose tissues (WAT) of adult offspring. FR30 procedure does not worsen the metabolic syndrome features induced by HF diet. However, FR30HF rats displayed catch-up growth to match the body weight of adult control HF animals, suggesting an increase of adiposity while showing hyperleptinemia and a blunted increase of corticosterone. Using quantitative RT-PCR array, we demonstrated that FR30HF rats exhibited leptin and Ob-Rb as well as many peptide precursor and receptor gene expression variations in WAT. We also showed that the expression of genes involved in adipogenesis was modified in FR30HF animals in a depot-specific manner. We observed an opposite variation of STAT3 phosphorylation levels, suggesting that leptin sensitivity is modified in WAT adult FR30 offspring. We demonstrated that 11β-HSD1, 11β-HSD2, GR, and MR genes are coexpressed in WAT and that FR30 procedure modifies gene expression levels, especially under HF diet. In particular, level variation of 11β-HSD2, whose protein expression was detected by Western blotting, may represent a novel mechanism that may affect WAT glucocorticoid sensitivity. Data suggest that maternal undernutrition differently programs the adult offspring WAT gene expression profile that may predispose for altered fat deposition.