Prenatal betamethasone exposure results in pituitary-adrenal hyporesponsiveness in adult sheep

Association of different doses of antenatal corticosteroids exposure with early major outcomes and early weight loss percentage in extremely preterm infants or extremely low birthweight infants: a multicentre cohort study

OBJECTIVES

To determine the dose-dependent associations between antenatal corticosteroids (ANS) exposure and the rates of major morbidities, and the early weight loss percentage (EWLP) in hospital among extremely preterm infants (EPI) or extremely low birthweight infants (ELBWI).

METHODS

A multicentre, retrospective cohort study of EPI or ELBWI born between 2017 and 2018 was conducted. Infants were classified into no ANS, partial ANS and complete ANS exposure group; three subgroups were generated by gestational age and birth weight. Multiple logistic regression and multiple linear regression were performed.

RESULTS

There were 725 infants included from 32 centres. Among no ANS, partial ANS and complete ANS exposure, there were significant differences in the proportions of bronchopulmonary dysplasia (BPD) (24.5%, 25.4% and 16.1%), necrotising enterocolitis (NEC) (6.7%, 2.0% and 2.0%) and death (29.6%, 18.5% and 13.5%), and insignificant differences in the proportions of intraventricular haemorrhage (IVH) (12.5%, 13.2% and 12.2%), and extrauterine growth restriction (EUGR) (50.0%, 56.6% and 59.5%). In the logistic regression, compared with no ANS exposure, complete ANS reduced the risk of BPD (OR 0.58, 95% CI 0.37 to 0.91), NEC (OR 0.21, 95% CI 0.08 to 0.57) and death (OR 0.36, 95% CI 0.23 to 0.56), and partial ANS reduced the risk of NEC (OR 0.23, 95% CI 0.07 to 0.72) and death (OR 0.54, 95% CI 0.34 to 0.87). Compared with partial ANS exposure, complete ANS decreased the risk of BPD (OR 0.58, 95% CI 0.37 to 0.91). There were insignificant associations between ANS exposure and IVH, EUGR. In the multiple linear regression, partial and complete ANS exposure increased EWLP only in the ≥28 weeks (w) and <1000 g subgroup (p<0.05).

CONCLUSIONS

Different doses of ANS (dexamethasone) exposure were protectively associated with BPD, NEC, death in hospital, but not EUGR at discharge among EPI or ELBWI. Beneficial dose-dependent associations between ANS (dexamethasone) exposure and BPD existed. ANS exposure increased EWLP only in the ≥28 w and<1000 g subgroup. ANS administration, especially complete ANS, is encouraged before preterm birth.

TRIAL REGISTRATION NUMBER

NCT06082414.

Development programming: Stress during gestation alters offspring development in sheep

Inappropriate management practices of domestic animals during pregnancy can be potential stressors, resulting in complex behavioural, physiological and neurological consequences in the developing offspring. Some of these consequences can last into adulthood or propagate to subsequent generations. We systematically summarized the results of different experimental patterns using artificially increased maternal glucocorticoid levels or prenatal maternal physiological stress paradigms, mediators between prenatal maternal stress (PMS) and programming effects in the offspring and the effects of PMS on offspring phenotypes in sheep. PMS can impair birthweight, regulate the development of the hypothalamic-pituitary-adrenal axis, modify behavioural patterns and cognitive abilities and alter gene expression and brain morphology in offspring. Further research should focus on the effects of programming on gene expression, immune function, gut microbiome, sex-specific effects and maternal behaviour of offspring, especially comparative studies of gestational periods when PMS is applied, continual studies of programming effects on offspring and treatment strategies that effectively reverse the detrimental programming effects of prenatal stress.

Effect of maternal periconceptional undernutrition in sheep on cortisol regulation in offspring from mid-late gestation, through to adulthood

INTRODUCTION

Maternal periconceptional undernutrition (PCUN) alters fetal hypothalamic-pituitary-adrenal axis (HPAA) function and placental glucocorticoid metabolism in sheep. The effects of PCUN on HPAA function in adult life are not known. We investigated the effects of PCUN on fetal adrenal development across gestation and on cortisol regulation in adult offspring.

METHODS

Ewes were undernourished from 61 days before to 30 days after conception ('PCUN') or fed ad libitum ('N'). mRNA expression in the fetal adrenal gland of ACTH receptor (ACTHR), steroidogenic acute regulatory protein (STAR), cytochrome P450 17A1 (CYP17A1), 11beta-hydroxysteroid-dehydrogenase type 2 (11βHSD2), insulin-like growth factor-2 (IGF2), and in the fetal hippocampus of 11βHSD1, 11βHSD2, mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) was determined at 50 (adrenal only), 85, 120 and 131 days of gestation (term=148 days). In adult offspring (≥ 3 years, N; 10 female, 5 male, PCUN; 10 female, 10 male) a combined arginine vasopressin (AVP, 0.1 μg/kg) and corticotropin-releasing hormone (CRH, 0.5 μg/kg) challenge and a metyrapone (40 mg/kg) challenge were undertaken. mRNA expression of ACTHR, STAR and CYP17A1 were determined in adult adrenals.

RESULTS

Fetal adrenal STAR, CYP17A1 and IGF2 mRNA expression were not different between groups in early gestation but were higher in PCUN than N at 131 days' gestation (all p<0.01). PCUN reduced fetal hippocampal MR and GR mRNA expression by 50% at 85 day, but not in later gestation. Adult offspring plasma cortisol responses to AVP+CRH or metyrapone were not different between groups. Plasma ACTH response to AVP+CRH was lower in PCUN males but ACTH response to metyrapone was not different between groups. Adult adrenal ACTHR, STAR, and CYP17A1 mRNA expression were not affected by PCUN.

CONCLUSIONS

We conclude that the effects of PCUN on fetal HPAA function that became apparent in late gestation, are not reflected in adrenal cortisol secretion in mid-adulthood.

Association between antenatal glucocorticoid exposure and the activity of the stress system, cognition, and behavior in 8- to 9-year-old children: A prospective observational study

INTRODUCTION

Glucocorticoid (GC) -induced fetal programming of the activity of the hypothalamus-pituitary-adrenal axis (HPAA) and its associated cognitive and behavioral consequences in later life have been well characterized in several animal species. However, information on humans is scarce. In this study, we examined HPAA activity markers and associated outcomes at 8 to 9 years of age among children prenatally exposed to GC for suspected preterm birth. Our hypothesis was that antenatal exposure to the betamethasone (BM) is associated with exacerbation of HPAA activity in childhood.

MATERIAL AND METHODS

Prospective observational study in 31 children whose mothers received single (n = 19) or multiple (n = 12) courses of BM for threatened preterm birth but born with normal weight appropriate for the gestational age (median 37+⁶  weeks of gestation) compared with 38 non-exposed, age-matched children. Primary end point was the activity of the HPAA in response to the Trier Social Stress Test. Secondary end points were changes in autonomic nervous system (ANS) activity, cognitive performance (IQ), attention-deficit/hyperactivity disorder (ADHD) symptoms, and electrocortical activity (EEG).

RESULTS

There was no statistically significant difference in HPAA activity markers between antenatal BM exposed and unexposed groups. ANS activity in BM-exposed children shifted towards a higher parasympathetic tone reflected by a higher overall high-frequency band power of heart rate variability. IQ scores were within normal limits for both groups; however, BM-exposed children had lower IQ scores than the unexposed group. BM-exposed group had marginally more ADHD core symptoms and increased electrocortical activity in the occipital brain region compared with controls. A monotonic dose-response relationship between BM exposure and activity of the ANS and IQ was estimated in post-hoc analyses.

CONCLUSIONS

Antenatal exposure to BM in the context of threatened preterm birth was not associated with changes in HPAA activity in childhood. However, BM exposure may be associated with changes in ANS activity. Antenatal GC prophylaxis is a valuable and often life-saving therapy, but its prescription may warrant a well-balanced risk-benefit assessment.

Metabolic Consequences of Glucocorticoid Exposure before Birth

Glucocorticoids have an important role in development of the metabolic phenotype in utero. They act as environmental and maturational signals in adapting feto-placental metabolism to maximize the chances of survival both before and at birth. They influence placental nutrient handling and fetal metabolic processes to support fetal growth, fuel storage and energy production with respect to nutrient availability. More specifically, they regulate the transport, utilization and production of a range of nutrients by the feto-placental tissues that enables greater metabolic flexibility in utero while minimizing any further drain on maternal resources during periods of stress. Near term, the natural rise in fetal glucocorticoid concentrations also stimulates key metabolic adaptations that prepare tissues for the new energy demanding functions after birth. Glucocorticoids, therefore, have a central role in the metabolic communication between the mother, placenta and fetus that optimizes offspring metabolic phenotype for survival to reproductive age. This review discusses the effects of maternal and fetal glucocorticoids on the supply and utilization of nutrients by the feto-placental tissues with particular emphasis on studies using quantitative methods to assess metabolism in rodents and sheep in vivo during late pregnancy. It considers the routes of glucocorticoid overexposure in utero, including experimental administration of synthetic glucocorticoids, and the mechanisms by which these hormones control feto-placental metabolism at the molecular, cellular and systems levels. It also briefly examines the consequences of intrauterine glucocorticoid overexposure for postnatal metabolic health and the generational inheritance of metabolic phenotype.

Long-Term Consequences of Adaptive Fetal Programming in Ruminant Livestock

Environmental perturbations during gestation can alter fetal development and postnatal animal performance. In humans, intrauterine growth restriction (IUGR) resulting from adaptive fetal programming is known as a leading cause of perinatal morbidity and mortality and predisposes offspring to metabolic disease, however, the prevalence and impact in livestock is not characterized as well. Multiple animal models have been developed as a proxy to determine mechanistic changes that underlie the postnatal phenotype resulting from these programming events in humans but have not been utilized as robustly in livestock. While the overall consequences are similar between models, the severity of the conditions appear to be dependent on type, timing, and duration of insult, indicating that some environmental insults are of more relevance to livestock production than others. Thus far, maternofetal stress during gestation has been shown to cause increased death loss, low birth weight, inefficient growth, and aberrant metabolism. A breadth of this data comes from the fetal ruminant collected near term or shortly thereafter, with fewer studies following these animals past weaning. Consequently, even less is known about how adaptive fetal programming impacts subsequent progeny. In this review, we summarize the current knowledge of the postnatal phenotype of livestock resulting from different models of fetal programming, with a focus on growth, metabolism, and reproductive efficiency. We further describe what is currently known about generational impacts of fetal programming in production systems, along with gaps and future directions to consider.

A Life Course Approach to the Relationship Between Fetal Growth and Hypothalamic-Pituitary-Adrenal Axis Function

CONTEXT

Human and animal studies suggest that hypothalamic-pituitary-adrenal axis (HPA-A) function may be programmed in utero; however, these findings are inconsistent. Given the powerful metabolic actions of cortisol, it is important to clarify the influence of early life on adult HPA-A function.

OBJECTIVE

To determine the relationship between fetal growth and HPA-A stress response to a psychosocial stressor in young adults.

DESIGN

Multigenerational, prospective cohort study (the Raine Study) conducted between 1989 and 1991.

SETTING

King Edward Memorial Hospital, Perth, Western Australia, Australia.

PARTICIPANTS

A total of 917 participants aged 18 years from Gen2 of the Raine Study.

MAIN OUTCOME MEASURES

Measures of hypothalamic-pituitary-adrenal axis function before and after exposure to the Trier Social Stress Test.

RESULTS

In fully adjusted models, an inverse linear relationship was observed between birthweight and plasma measures of (1) baseline cortisol (β = -0.90%, 95% CI: -1.73 to -0.07; P = 0.03); (2) peak cortisol (β = -0.78%, 95% CI -1.51 to -0.06; P = 0.03); (3) area under the curve with respect to ground (β = -0.89%, 95% CI -1.60 to -0.18; P = 0.01); and (4) adrenal sensitivity (β = -1.02, 95% CI: -1.85 to -0.18; P = 0.02). Similar results were demonstrated for percent optimal birthweight. No consistent quadratic relationships were identified. No associations were found between measures of fetal adiposity and HPA-A function at age 18 years, or fetal growth and HPA-A response pattern. Removal of anticipatory responders from the models substantially attenuated the observed relationships.

CONCLUSION

We observed an inverse linear relationship between fetal growth and HPA-A function at age 18 years. This differs from the inverse parabolic relationship (inverted U curve) reported in adults of advanced age. Altered adrenal sensitivity may underlie this relationship.

Prematurity and Dysmaturity Are Associated With Reduced Height and Shorter Distal Limb Length in Horses

The long-term effects of gestational immaturity in the premature (defined as < 320 days gestation) and dysmature (normal term but showing some signs of prematurity) foal have not been thoroughly investigated. Studies have reported that a high percentage of gestationally immature foals with related orthopedic issues such as incomplete ossification may fail to fulfill their intended athletic purpose, particularly in Thoroughbred racing. In humans, premature birth is associated with shorter stature at maturity and variations in anatomical ratios, linked to alterations in metabolism and timing of physeal closure in the long bones. We hypothesized that gestational immaturity in horses might similarly be associated with reduced height and different anatomical ratios at maturity. In this preliminary study, the skeletal ratios of horses with a history of gestational immaturity, identified through veterinary and breeder records, were compared with those of unaffected, closely related horses (i.e., sire, dam, sibling). External measurements were taken from conformation photographs of cases (n = 19) and related horses (n = 28), and these were then combined into indices to evaluate and compare metric properties of conformation. A principal component analysis showed that the first two principal components account for 43.8% of the total conformational variation of the horses' external features, separating horses with a rectangular conformation (body length > height at the withers), from those that are more square (body length = height at the withers). Varimax rotation of PC1 and analysis of different gestational groups showed a significant effect of gestational immaturity (P = .001), with the premature group being more affected than the dysmature group (P = .009, P = .012). Mean values for the four dominant indices showed that these groups have significantly lower distal limb to body length relationships than controls. The observed differences suggest that gestational immaturity may affect anatomical ratios at maturity, which, in combination with orthopedic issues arising from incomplete ossification, may have a further impact on long-term athletic potential.

Allium cepa Linn juice protect against alterations in reproductive functions induced by maternal dexamethsone treatment during lactation in male offspring of Wistar rats

Treatment with dams with dexamethasone during lactation has been reported to induce oxidative stress in the testis of the offspring. Allium cepa L (Red Onion) is known to be a potent free radical scavenger. The protective role of Allium cepa against oxidative stress induced in testis following treatment with dexamehasone during lactation in Wistar rats was assessed. Twenty female rats were assigned into four groups (n = 5) during lactation and they were treated as follows: Group 1 serve as Control (distilled water), Group 2, 3, and four were admistered dexamethasone (60 μg/kg), Allium cepa (5 ml/kg) and dexamethasone + Allium cepa respectively. Testicular descent, pubertal age, sperm quality indices, and serum hormonal profile were assessed as indices of reproductive function. Testicular malondialdehyde (MDA) reduced glutathione (GSH) as well as superoxide dismutase (SOD) and catalase activities were assessed as measures of oxidative stress. Results obtained showed that dexamethasone caused significant (P < 0.05) reduction in testes weights, indices of sperm quality, serum testosterone, FSH, LH levels and testicular antioxidant enzyme activities. There was significant delay (P < 0.05) in days of testes descent, preputial separation and increase in testicular MDA. However, maternal treatment with Allium cepa Linn juice significantly (P < 0.05) improved both indices of reproductive function and testicular antioxidant enzymes. These findings suggest that Allium cepa Linn has a protective effect against testicular oxidative stress and reproductive dysfunction following treatment of dams with dexamethasone during lactation.

Prenatal glucocorticoids exposure and fetal adrenal developmental programming

Clinically, we apply synthetic glucocorticoids to treat fetal and maternal diseases, such as premature labor and autoimmune diseases. Although its clinical efficacy is positive, the fetus will be exposed to exogenous synthetic glucocorticoids. Prenatal adverse environments (such as xenobiotics exposure, malnutrition, infection, hypoxia and stress) can cause fetuses overexposure to excessive endogenous maternal glucocorticoids. The level of glucocorticoids is the key to fetal tissue maturation and postnatal fate. A large number of studies have found that prenatal glucocorticoids exposure can lead to fetal adrenal dysplasia and dysfunction, continuing after birth and even into adulthood. As the core organ of fetal-originated adult diseases, fetal adrenal dysplasia is closely related to the susceptibility and occurrence of multiple chronic diseases, and there are also obvious gender differences. However, its intrauterine programming mechanisms have not been fully elucidated. This review summarizes recent advances in prenatal glucocorticoids exposure and fetal adrenal developmental programming alterations, which is of great significance for explaining adrenal developmental toxicity and the intrauterine origin of fetal-originated adult diseases.

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.

Chronic stress influences attentional and judgement bias and the activity of the HPA axis in sheep

INTRODUCTION

Environmental challenges are part of everyday life for most domestic animals. However, very little is known about how animals cope emotionally and physiologically with cumulative challenges. This experiment aimed to determine the impact of long-term exposure to environmental challenges on the affective state and hypothalamic-pituitary-adrenal (HPA) axis responses to a subsequent additional acute shearing challenge.

METHODS

Sheep were exposed to either a long-term environmental challenge (rest disruption and individual housing) in order to induce chronic stress (chronic stress group) or control conditions (group housing in a field with low stress handling and daily feed rewards, control group). Judgement and attention bias were assessed as measures of the emotional state following several days of the challenge or control treatment (pre-shearing tests). In addition, the responsiveness of the HPA-axis was evaluated using a combined Corticotropin Releasing Hormone and Arginine Vasopressin (CRH/AVP) challenge. Finally, all animals were exposed to an acute shearing challenge, then judgement bias (post-shearing test), HPA-axis and internal body temperature responses were determined.

RESULTS

In the pre-shearing judgement bias test, the chronic stress group slightly increased optimism compared to the control treatment. In the attention bias test, the chronic stress group showed reduced vigilance behaviour towards a predator threat and a quicker approach to the food compared to the control treatment. The chronic stress group also had lower plasma ACTH concentrations in response to the CRH/AVP challenge compared to the control group, no differences in cortisol concentrations were found. In the post-shearing judgement bias test, differences in optimism were no longer evident between the chronic stress and control groups. Plasma ACTH concentrations and body temperatures showed a greater increase in response to shearing in the chronic stress group compared to the control group.

CONCLUSION

Our results suggest that long-term exposure to challenges biased cognitive measures of the affective state towards an increased expectation of a reward and reduced attention towards a threat. The exaggerated ACTH responses in the chronic stress group may be indicative of HPA-axis dysregulation. Despite a period of challenge exposure in the chronic stress group, judgement bias responses to the shearing challenge were similar in the chronic stress and control groups; the reasons for this need further investigation. The altered affective state together with signs of HPA-axis dysregulation may indicate an increased risk of compromised welfare in animals exposed to long-term environmental challenges.

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.

Prenatal Treatment of Congenital Adrenal Hyperplasia: Long-Term Effects of Excess Glucocorticoid Exposure

Prenatal treatment of congenital adrenal hyperplasia with dexamethasone (DEX) has been in use since the mid-1980s and has proven effective at reducing virilization of external genitalia in affected girls. However, multiple experimental studies on animals and clinical studies on humans show that prenatal administration of glucocorticoids may cause unwanted adverse effects which have raised concerns about the long-term safety of the treatment. The long-term outcome of prenatal DEX treatment on cognition has been investigated, but the results are still conflicting. Overall, most of the evidence points towards a negative effect on executive functions where girls seem to be more susceptible than boys. Some effects on social behavior have been observed, but results are still contradictory and treated children are mostly well adapted. Cardiovascular, renal, and metabolic function are still areas to be investigated. Larger studies are warranted to investigate areas other than cognition and behavior and to be able to draw more definitive conclusions about prenatal DEX treatment.

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.

Effects of Late Gestational Fetal Exposure to Dexamethasone Administration on the Postnatal Hypothalamus-Pituitary-Adrenal Axis Response to Hypoglycemia in Pigs

BACKGROUND

Prenatal glucocorticoid administration alters the activity of the fetal hypothalamic-pituitary-adrenocortical axis (HPAA), and correspondingly the adenocorticotropic hormone (ACTH) and cortisol levels after birth. The dosages required for these effects are critically discussed. Activation of the HPAA is related to metabolic syndrome and diabetes mellitus. Hypoglycemia is the classic side effect of antidiabetic treatment. We hypothesized that a low dosage of dexamethasone in late pregnancy alters the HPAA response to hypoglycemia in pigs.

METHODS

12 pregnant sows were randomly assigned to two groups which received either a low-dose intramuscular injection (99th and 100th day of gestation) of dexamethasone (0.06 μg/kg body weight) or vehicle. Three months after birth, 18 dexamethasone-treated anaesthetized offspring and 12 control offspring underwent a 75 min hypoglycemic clamp (blood glucose below 4 mmol/L) procedure. Heart rate (HR), blood pressure, ACTH and cortisol levels and body weight (at birth and after three months) were recorded.

RESULTS

Dexamethasone-treated animals exhibited significantly elevated ACTH (139.9 ± 12.7 pg/mL) and cortisol (483.1 ± 30.3 nmol/L) levels during hypoglycemia as compared to the control group (41.7 ± 6.5 pg/mL and 257.9 ± 26.7 nmol/L, respectively), as well as an elevated HR (205.5 ± 5.7 bpm) and blood pressure (systolic: 128.6 ± 1.5, diastolic: 85.7 ± 0.7 mmHg) response as compared to the control group (153.2 ± 4.5 bpm; systolic: 118.6 ± 1.6, diastolic: 79.5 ± 1.4 mmHg, respectively; p < 0.001).

CONCLUSIONS

Low-dose prenatal administration of dexamethasone not only exerts effects on the HPAA (ACTH and cortisol concentration) and vital parameters (HR and diastolic blood pressure) under baseline conditions, but also on ACTH, HR and systolic blood pressure during hypoglycemia.

Glucocorticoid programming of intrauterine development

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

Programming of 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.

The impact of maternal synthetic glucocorticoid administration in late pregnancy on fetal and early neonatal hypothalamic-pituitary-adrenal axes regulatory genes is dependent upon dose and gestational age at exposure

In this study, we determined the gene and/or protein expression of hypothalamic-pituitary-adrenal (HPA) axis regulatory molecules following synthetic glucocorticoid exposures. Pregnant sheep received intramuscular saline or betamethasone (BET) injections at 104 (BET-1), 104 and 111(BET-2) or 104, 111 and 118 (BET-3) days of gestation (dG). Samples were collected at numerous time-points between 75 dG and 12 weeks postnatal age. In the BET-3 treatment group, fetal plasma cortisol levels were lower at 145 dG than controls and gestational length was lengthened significantly. The cortisol:adrenocorticotropic hormone (ACTH) ratio in fetal plasma of control and BET-3 fetuses rose significantly between132 and 145 dG, and remained elevated in lambs at 6 and 12 weeks of age; this rise was truncated at day 145 in fetuses of BET-3 treated mothers. After BET treatment, fetal and postnatal pituitary proopiomelanocortin mRNA levels were reduced from 109 dG to 12 weeks postnatal age; pituitary prohormone convertase 1 and 2 mRNA levels were reduced at 145 dG and postnatally; hypothalamic arginine vasopressin mRNA levels were lowered at all time-points, but corticotrophin-releasing hormone mRNA levels were reduced only in postnatal lambs. Maternal BET increased late fetal and/or postnatal adrenal mRNA levels of ACTH receptor and 3β hydroxysteroid dehydrogenase but decreased steroidogenic acute regulatory protein and P450 17-α hydroxylase. The altered mRNA levels of key HPA axis regulatory proteins after maternal BET injections suggests processes that may subserve long-term changes in HPA activity in later life after prenatal exposure to synthetic glucocorticoids.

Neonatal glucocorticoid overexposure programs pituitary-adrenal function in ponies

The present study tested the hypothesis that overexposure to endogenous glucocorticoids in neonatal life alters the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis in ponies at 1 and 2 yr of age. Newborn foals received saline (0.9% NaCl, n = 8, control) or long-acting adrenocorticotropic hormone (ACTH1-24) (Depot Synacthen 0.125 mg intramuscularly twice daily, n = 9) for 5 d after birth to raise cortisol concentrations 5- to 6-fold. At 1 and 2 yr of age, HPA axis function was assessed by bolus administration of short-acting ACTH1-24 (1 μg/kg intravenous) and insulin (0.5 U/kg intravenous) to induce hypoglycemic on separate days. Arterial blood samples were taken at 5 to 30-min intervals before and after drug administration to measure plasma ACTH and/or cortisol concentrations. There were no differences in the basal plasma ACTH or cortisol concentrations or in the cortisol response to exogenous ACTH1-24 with neonatal treatment or age. At 1 and 2 yr of age, the increment in plasma ACTH but not cortisol at 60 min in response to insulin-induced hypoglycemia was greater in ponies treated neonatally with ACTH than saline (P < 0.05). Neonatal cortisol overexposure induced by neonatal ACTH treatment, therefore, alters functioning of the HPA axis in adult ponies.

Antenatal glucocorticoids: where are we after forty years?

Since their introduction more than forty years ago, antenatal glucocorticoids have become a cornerstone in the management of preterm birth and have been responsible for substantial reductions in neonatal mortality and morbidity. Clinical trials conducted over the past decade have shown that these benefits may be increased further through administration of repeat doses of antenatal glucocorticoids in women at ongoing risk of preterm and in those undergoing elective cesarean at term. At the same time, a growing body of experimental animal evidence and observational data in humans has linked fetal overexposure to maternal glucocorticoids with increased risk of cardiovascular, metabolic and other disorders in later life. Despite these concerns, and somewhat surprisingly, there has been little evidence to date from randomized trials of longer-term harm from clinical doses of synthetic glucocorticoids. However, with wider clinical application of antenatal glucocorticoid therapy there has been greater need to consider the potential for later adverse effects. This paper reviews current evidence for the short- and long-term health effects of antenatal glucocorticoids and discusses the apparent discrepancy between data from randomized clinical trials and other studies.

Glucocorticoids and fetal programming part 1: Outcomes

Fetal development is a critical period for shaping the lifelong health of an individual. However, the fetus is susceptible to internal and external stimuli that can lead to adverse long-term health consequences. Glucocorticoids are an important developmental switch, driving changes in gene regulation that are necessary for normal growth and maturation. The fetal hypothalamic-pituitary-adrenal (HPA) axis is particularly susceptible to long-term programming by glucocorticoids; these effects can persist throughout the life of an organism. Dysfunction of the HPA axis as a result of fetal programming has been associated with impaired brain growth, altered behaviour and increased susceptibility to chronic disease (such as metabolic and cardiovascular disease). Moreover, the effects of glucocorticoid-mediated programming are evident in subsequent generations, and transmission of these changes can occur through both maternal and paternal lineages.

Mechanisms by which maternal obesity programs offspring for obesity: evidence from animal studies

Maternal obesity can profoundly affect offspring phenotype and predisposition to obesity and metabolic disease. Carefully controlled studies in precocial and altricial mammalian species provide insights into the involved mechanisms. These include programming of hypothalamic appetite-regulating centers to increase orexigenic relative to anorexigenic drive; increasing maternal, fetal, and offspring adrenal and peripheral tissue glucocorticoid production; and increasing maternal oxidative stress. Outcomes often show offspring sex differences that may play a role in the differential susceptibility of males and females to later-life obesity and other related metabolic diseases.

Maternal supplementation with fishmeal protects against late gestation endotoxin-induced fetal programming of the ovine hypothalamic-pituitary-adrenal axis

Adverse uterine environments caused by maternal stress (such as bacterial endotoxin) can alter programming of the fetal hypothalamic–pituitary–adrenal axis (HPAA) rendering offspring susceptible to various adulthood diseases. Thus, protection against this type of stress may be critical for ensuring offspring health. The present study was designed to determine if maternal supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFAs) during pregnancy helps to protect against stress-induced fetal programming. Briefly, 53 ewes were fed a diet supplemented with fishmeal (FM) or soybean meal (SM) from day 100 of gestation (gd100) through lactation. On gd135, half the ewes from each dietary group were challenged with either 1.2 μg/kg Escherichia coli lipopolysaccharide (LPS) endotoxin, or saline as the control. The offspring’s cortisol response to weaning stress was assessed 50 days postpartum by measuring serum cortisol concentrations 0, 6 and 24 h post weaning. Twenty-four hours post-weaning, lambs were subjected to an adrenocorticotropic hormone (ACTH) challenge (0.5 μg/kg) and serum cortisol concentrations were measured 0, 0.25, 0.5, 1 and 2 h post injection. At 5.5 months of age, offspring were also challenged with 400 ng/kg of LPS, and serum cortisol concentrations were measured 0, 2, 4 and 6 h post challenge. Interestingly, female offspring born to FM+LPS mothers had a greater cortisol response to weaning and endotoxin challenge compared with the other treatments, while female offspring born to SM+LPS mothers had a faster cortisol response to the ACTH stressor. Additionally, males born to FM+LPS mothers had a greater cortisol response to the ACTH challenge than the other treatments. Overall, FM supplementation during gestation combined with LPS challenge alters HPAA responsiveness of the offspring into adulthood.

Effects of tail docking and castration on stress responses in lambs and the influence of prenatal glucocorticoid treatment

It is common practice in Australian agriculture to remove the tails of lambs to prevent infection and to castrate males to prevent behavioural problems and unwanted reproduction. We have studied the pain and stress responses to these interventions by measuring changes in the hypothalamic-pituitary-adrenal (HPA) axis and β-endorphin levels. Further, we have evaluated the effects of prenatal exposure to dexamethasone, which is known to affect the developing HPA axis. In control animals that had received prenatal saline treatment, plasma cortisol and adrenocorticotrophin (ACTH) levels increased after the interventions in both females and males. Plasma β-endorphin levels also increased after the interventions, but the responses were less consistent. Prenatal dexamethasone exposure early in pregnancy (dexamethasone 0.14 mg kg(-1) ewe weight injection commenced on day 40 of pregnancy for four consecutive intramuscular injections at 12-hourly intervals) blunted the cortisol response to tail docking in female offspring, but not to combined tail docking and castration in males. It had no effect on ACTH or β-endorphin responses in either sex. These findings describe the stress responses to these common agricultural interventions and suggest that long-term development of the HPA axis in females is altered by prenatal exposure to dexamethasone.

Early-life glucocorticoid exposure: the hypothalamic-pituitary-adrenal axis, placental function, and long-term disease risk

An adverse early-life environment is associated with long-term disease consequences. Adversity early in life is hypothesized to elicit developmental adaptations that serve to improve fetal and postnatal survival and prepare the organism for a particular range of postnatal environments. These processes, although adaptive in their nature, may later prove to be maladaptive or disadvantageous if the prenatal and postnatal environments are widely discrepant. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids is one model of early-life adversity that contributes substantially to the propensity of developing disease. Moreover, early-life glucocorticoid exposure has direct clinical relevance because synthetic glucocorticoids are routinely used in the management of women at risk of early preterm birth. In this regard, reports of adverse events in human newborns have raised concerns about the safety of glucocorticoid treatment; synthetic glucocorticoids have detrimental effects on fetal growth and development, childhood cognition, and long-term behavioral outcomes. Experimental evidence supports a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development and changes in placental function, and many of these alterations appear to be permanent. Because the placenta is the conduit between the maternal and fetal environments, it is likely that placental function plays a key role in mediating effects of fetal glucocorticoid exposure on hypothalamic-pituitary-adrenal axis development and long-term disease risk. Here we review recent insights into how the placenta responds to changes in the intrauterine glucocorticoid environment and discuss possible mechanisms by which the placenta mediates fetal hypothalamic-pituitary-adrenal development, metabolism, cardiovascular function, and reproduction.

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.

Antenatal glucocorticoid exposure enhances the inhibition of adrenal steroidogenesis by leptin in a sex-specific fashion

Antenatal treatment with glucocorticoids (GC) poses long-lasting effects on endocrine and cardiovascular function. Given that leptin attenuates adrenal function and the reported sex differences in plasma leptin concentration, we hypothesized that antenatal GC will affect leptin levels and leptin modulation of adrenal function in a sex-specific manner. Pregnant sheep were randomly given betamethasone or vehicle at 80 days of gestational age, and offspring were allowed to deliver at term. Adrenocortical cells (ADC) were studied from male and female animals at 1.5 yr of age. Plasma leptin was increased 66% in male and 41% in female GC-treated animals (P < 0.05), but adrenal leptin mRNA was increased only in GC-treated males (P < 0.05). Whereas mRNA expression of adrenal leptin receptor isoforms showed sex (Ob-Ra and Ob-Rb) and treatment-dependent (Ob-Rb) differences, protein expression remained unchanged. GC-treated females showed greater plasma cortisol and greater ACTH-stimulated cortisol production (P < 0.05) in ADC. Leptin exerted a greater inhibitory effect on basal and stimulated cortisol by ADC from GC-treated males (P < 0.05), with no differences in females. Similarly, greater inhibitory effects on basal and ACTH-stimulated StAR and ACTH-R mRNA expression by leptin were observed in cells from GC males (P < 0.05), with no changes in females. Persistent effects of antenatal GC on leptin levels and leptin modulation of adrenal function are expressed in a sex-specific manner; males are more sensitive than females to the inhibitory influences of leptin on adrenal function, and this effect appears to be mediated by a greater inhibition of StAR and ACTH-R expression in adrenals of adult GC-treated males.

Multigenerational effects of fetal dexamethasone exposure on the hypothalamic-pituitary-adrenal axis of first- and second-generation female offspring

OBJECTIVE

Synthetic glucocorticoid (sGC) administration to women threatening preterm delivery increases neonatal survival. Evidence shows that fetal exposure to glucocorticoid levels higher than appropriate for current maturation programs offspring development. We examined fetal sGC multigenerational effects on F1 and F2 female offspring hypothalamo-pituitary-adrenal axis (HPAA) function.

STUDY DESIGN

At 0.7 gestation, pregnant F0 ewes received 4 dexamethasone injections (2 mg, approximately 60 μg/kg(-1) per day(-1), 12 hours apart) or saline (control). F1 female offspring were bred to produce F2 female offspring. Postpubertal HPAA function was tested in F1 and F2 ewes.

RESULTS

F1 and F2 ewe lambs showed reduced birthweight and morphometrics. Dexamethasone increased baseline but reduced stimulated HPAA activity in F1 and F2 female offspring.

CONCLUSION

This is the first demonstration that sGC doses in the clinical range have multigenerational effects on hypothalamo-pituitary-adrenal activity in a precocial species, indicating the need for the study of long-term effects of fetal sGC exposure.

Effects of glucocorticoid treatment given in early or late gestation on growth and development in sheep

Antenatal corticosteroids are used to augment fetal lung maturity in human pregnancy. Dexamethasone (DEX) is also used to treat congenital adrenal hyperplasia of the fetus in early pregnancy. We previously reported effects of synthetic corticosteroids given to sheep in early or late gestation on pregnancy length and fetal cortisol levels and glucocorticoids alter plasma insulin-like growth factor (IGF) and insulin-like growth factor binding protein (IGFBP) concentrations in late pregnancy and reduce fetal weight. The effects of administering DEX in early pregnancy on fetal organ weights and betamethasone (BET) given in late gestation on weights of fetal brain regions or organ development have not been reported. We hypothesized that BET or DEX administration at either stage of pregnancy would have deleterious effects on fetal development and associated hormones. In early pregnancy, DEX was administered as four injections at 12-hourly intervals over 48 h commencing at 40–42 days of gestation (dG). There was no consistent effect on fetal weight, or individual fetal organ weights, except in females at 7 months postnatal age. When BET was administered at 104, 111 and 118 dG, the previously reported reduction in total fetal weight was associated with significant reductions in weights of fetal brain, cerebellum, heart, kidney and liver. Fetal plasma insulin, leptin and triiodothyronine were also reduced at different times in fetal and postnatal life. We conclude that at the amounts given, the sheep fetus is sensitive to maternal administration of synthetic glucocorticoid in late gestation, with effects on growth and metabolic hormones that may persist into postnatal life.

Effects of antenatal corticosteroids on the hypothalamic-pituitary-adrenocortical axis of the fetus and newborn: experimental findings and clinical considerations

The hypothalamic-pituitary-adrenocortical (HPA) axis is a major neuroendocrine pathway that modulates the stress response. The glucocorticoid, cortisol, is the principal end product of the HPA axis in humans and plays a fundamental role in maintaining homeostasis and in fetal maturation and development. Antenatal administration of synthetic glucocorticoids (GCs) accelerates fetal lung maturation and has significantly decreased neonatal mortality and morbidity in infants born before 34 weeks of gestation. Exposure to excess levels of endogenous GCs and exogenous GCs (betamethasone and dexamethasone) has been shown to alter the normal development trajectory. The development and regulation of the fetal HPA axis is discussed and the experimental animal evidence presented suggests long-term adverse consequences of altered HPA function. The clinical data in infants exposed to GCs also suggest altered HPA axis function over the short term. The longer-term consequences of antenatal GC exposure on HPA axis function and subtler neurodevelopmental outcomes including adaptation to stress, cognition, behavior, and the cardiovascular and immune responses are poorly understood. Emerging clinical strategies and interventions may help in the selection of mothers at risk for preterm delivery who would benefit from existing or future formulations of antenatal GCs with a reduction in the associated risk to the fetus and newborn. Detailed longitudinal long-term follow-up of those infants exposed to synthetic GCs are needed.

Glucocorticoid exposure of sheep at 0.7 to 0.75 gestation augments late-gestation fetal stress responses

OBJECTIVES

Exposure to glucocorticoid levels inappropriately high for current maturation alters fetal hypothalamo-pituitary-adrenal axis (HPAA) development. In an established fetal sheep model, we determined whether clinical betamethasone doses used to accelerate fetal lung maturation have persistent effects on fetal HPAA hypotensive-stress responses.

STUDY DESIGN

Pregnant ewes received saline (n = 6) or betamethasone (n = 6); 2 × 110 μg/kg body weight doses injected 24 hours apart (106/107 and 112/113 days' gestational age, term 150 days). Basal adrenocorticotropin (ACTH) and cortisol and responses to fetal hypotension were measured before and 5 days after the first course and 14 days after the second course.

RESULTS

Basal ACTH and cortisol were similar with treatment. HPAA responses to hypotension increased after the second but not first course and ACTH/cortisol ratio increased indicating central HPAA effects.

CONCLUSIONS

Results demonstrate latency in the emergence of fetal HPAA hyperresponsiveness following betamethasone exposure that may explain hyperresponsiveness in full-term but not preterm neonates.

Psychobiological effects of prenatal glucocorticoid exposure in 10-year-old-children

BACKGROUND

Prenatal stress seems to have long-lasting effects on biological and psychological processes of the offspring. However, to date, there have been no studies investigating the effects of prenatal glucocorticoid exposure on psychological, endocrine, and autonomic responses to a standardized psychosocial stress test in children.

METHODS

A sample of 115 healthy, 10-year-old children was examined. The Glucocorticoids + Tocolytics group was characterized by tocolytic treatment of the mothers due to preterm labor (n = 43). In addition, the pregnant women received glucocorticoid treatment in order to accelerate fetal lung maturation in case of preterm birth. The first comparison group (Tocolytics) consisted of children whose mothers also experienced preterm labor, but did not receive glucocorticoid treatment (n = 35). In the second comparison group (CONTROL), children whose mothers had a complication-free pregnancy were assessed (n = 37). Psychological parameters (stress appraisal and mood) using self-report questionnaires as well as salivary cortisol, salivary alpha-amylase, and heart rate were measured during a standardized psychosocial stress test (Trier Social Stress Test for Children).

RESULTS

Group comparisons revealed that a subscale of stress appraisal, control expectancies, significantly differed in children who were prenatally exposed to glucocorticoids as compared to both comparison groups (F = 4.889, p = 0.009). Furthermore, significant differences between the groups were revealed for salivary cortisol. With respect to overall stress appraisal and heart rate, trends toward significance were observed between the three groups.

CONCLUSION

At the age of ten, those children who have been exposed to prenatal maternal glucocorticoids show changed psychobiological stress reactivity to a standardized psychosocial stress test as compared to control children.

The impact of chronic intrauterine inflammation on the physiologic and neurodevelopmental consequences of intermittent umbilical cord occlusion in fetal sheep

OBJECTIVE

To determine the effect of intrauterine inflammation on fetal responses to umbilical cord occlusion (UCO).

STUDY DESIGN

In pregnant sheep, lipopolysaccharide (LPS) or saline (SAL) was infused intra-amniotically for 4 weeks from 80 days of gestation (d). At 110 d, fetuses were instrumented for UCOs (5 × 2-minutes, 30-minute intervals: LPS + UCO, n = 6; SAL + UCO, n = 8) or no UCO (sham, n = 6) on 117 and 118 d. Tissues were collected at 126 d.

RESULTS

Fetal physiological responses to UCO were similar between LPS + UCO and SAL + UCO. Histologic chorioamnionitis and increased amniotic fluid interleukin 8 (IL-8) were observed in LPS + UCO pregnancies (versus SAL + UCO, P < .05). CNPase-positive oligodendrocyte number in the cerebral white matter was lower in LPS + UCO and SAL + UCO than sham (P < .05); there was no effect on astrocytes or activated microglia/macrophages. Two of the SAL + UCO fetuses had white matter lesions; none were observed in LPS + UCO or sham.

CONCLUSION

Chronic pre-existing intrauterine inflammation did not exacerbate fetal brain injury induced by intermittent UCO.

Treatment with an SSRI antidepressant restores hippocampo-hypothalamic corticosteroid feedback and reverses insulin resistance in low-birth-weight rats

Low birth weight (LBW) is associated with type 2 diabetes and depression, which may be related to prenatal stress and insulin resistance as a result of chronic hypothalamic-pituitary-adrenal (HPA) axis hyperactivity. We examined whether treatment with a selective serotonin reuptake inhibitor [escitalopram (ESC)] could downregulate HPA axis activity and restore insulin sensitivity in LBW rats. After 4-5 wk of treatment, ESC-exposed LBW (SSRI-LBW) and saline-treated control and LBW rats (Cx and LBW) underwent an oral glucose tolerance test or a hyperinsulinemic euglycemic clamp to assess whole body insulin sensitivity. Hepatic phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression and red skeletal muscle PKB Ser(473) phosphorylation were used to assess tissue-specific insulin sensitivity. mRNA expression of the hypothalamic mineralocorticoid receptor was fivefold upregulated in LBW (P < 0.05 vs. Cx), accompanied by increased corticosterone release during restraint stress and total 24-h urinary excretion (P < 0.05 vs. Cx), whole body insulin resistance (P < 0.001 vs. Cx), and impaired insulin suppression of hepatic PEPCK mRNA expression (P < 0.05 vs. Cx). Additionally, there was a tendency for reduced red muscle PKB Ser(473) phosphorylation. The ESC treatment normalized corticosterone secretion (P < 0.05 vs. LBW), whole body insulin sensitivity (P < 0.01) as well as postprandial suppression of hepatic mRNA PEPCK expression (P < 0.05), and red muscle PKB Ser(473) phosphorylation (P < 0.01 vs. LBW). We conclude that these data suggest that the insulin resistance and chronic HPA axis hyperactivity in LBW rats can be reversed by treatment with an ESC, which downregulates HPA axis activity, lowers glucocorticoid exposure, and restores insulin sensitivity in LBW rats.

Maternal undernutrition and endocrine development

Maternal undernutrition, whether it occurs before conception, throughout gestation or during lactation, may lead to physiological adaptations in the fetus that will affect the health of the offspring in adult life. The timing, severity, duration and nature of the maternal nutritional insult may affect the offspring differently. Other factors determining outcome following maternal undernutrition are fetal number and gender. Importantly, effects of maternal undernutrition may be carried over into subsequent generations. This review examines the endocrine pathways disrupted by maternal undernutrition that affect the long-term postnatal health of the offspring. Maternal and childhood undernutrition are highly prevalent in low- and middle-income countries, and, in developed countries, unintentional undernutrition may arise from maternal dieting. It is, therefore, important that we better understand the mechanisms driving the long-term effects of maternal undernutrition, as well as identifying treatments to ameliorate the associated mortality and morbidity.

The effect of early to mid-gestational nutrient restriction on female offspring fertility and hypothalamic-pituitary-adrenal axis response to stress

Primiparous ewes born as singletons to Rambouillet x Columbia crossbred ewes fed either 100% of NRC recommendations (control, Con; n = 7) or 50% of NRC (nutrient restricted, NR; n = 7) from d 28 through 78 postmating were utilized for this study. At 1 yr of age, a subset of ewes born to Con (n = 4) and NR (n = 4) mothers received jugular catheters and were subjected to a corticotrophin-releasing hormone (CRH)/arginine vasopressin (AVP) challenge, an ACTH challenge, and an isolation stress test, in which ACTH and cortisol responses were determined. A week after these challenges, estrus was monitored twice daily in all ewes from Con (n = 7) and NR mothers (n = 7). Once estrus was observed (d 0), daily blood samples were collected from ewes for progesterone through the subsequent estrus. Estrous detection and daily blood sampling were repeated during an estrous cycle in the next year, ewes were hand mated at the second estrus, and pregnancy was determined by delivery of a live lamb(s). Ewes from NR mothers tended (P = 0.10) to have a greater peak ACTH response after an intravenous CRH/AVP injection than ewes from Con mothers. The cortisol response of ewes to a CRH/AVP or ACTH challenge was not influenced by maternal nutrition. In contrast, ewes from Con mothers tended (P = 0.10) to release more ACTH in response to the isolation stress test and showed a greater (P = 0.04) cortisol release than ewes from NR mothers. Ewes from NR mothers exhibited decreased (P < 0.05) plasma progesterone in both yr 1 and 2 of the study compared with ewes from Con mothers. Furthermore, fewer (P < 0.0001) ewes from NR mothers produced a lamb (1 of 7) than ewes from Con mothers (7 of 7) during yr 2 of the study. These findings indicate that maternal undernutrition during early gestation may affect stress responses by the offspring, but has limited impact on hypothalamo-pituitary-adrenal sensitivity. Furthermore, offspring of NR ewes exhibited reduced progesterone secretion during the luteal phase of their estrous cycles and a markedly reduced fertility compared with offspring from Con ewes.

Prenatal synthetic glucocorticoid exposure alters hypothalamic-pituitary-adrenal regulation and pregnancy outcomes in mature female guinea pigs

Preterm delivery occurs in approximately 10% of all pregnancies. Prenatal exposure to synthetic glucocorticoids (sGCs) reduces the incidence of respiratory distress syndrome (RDS) in these babies. Therefore, administration of multiple courses of sGCs became common practice. Animal and human studies have demonstrated that multiple courses of sGCs can have long-term effects. While the majority of animal studies have been undertaken in male offspring, it is emerging that there are profound sex differences in the consequences of prenatal sGC exposure. To our knowledge, no studies have determined the effects of prenatal sGC exposure on hypothalamic-pituitary-adrenal (HPA) axis function in female offspring while accounting for reproductive cycle status, or determined if there are effects on pregnancy parameters. Pregnant guinea pigs were administered three courses of betamethasone (Beta), dexamethasone (Dex) or vehicle on gestational days 40/41, 50/51 and 60/61. In adulthood (age range: postnatal days 126-165), basal and activated HPA axis function were assessed at various stages of the reproductive cycle. The female offspring were then mated and underwent an undisturbed pregnancy. Females were killed in the luteal phase of the reproductive cycle following litter weaning, and molecular analysis undertaken. In the luteal phase, Beta-exposed females exhibited significantly lower basal salivary cortisol levels (P < 0.05). Dex-exposed females also exhibited significantly lower basal salivary cortisol levels during the luteal phase (P < 0.05), but increased basal salivary cortisol levels during the ostrous phase (P < 0.01). The Beta-exposed females exhibited increased glucocorticoid receptor (GR) mRNA expression in the CA1/2 region of the hippocampus (P < 0.05) and MC2R mRNA in the adrenal cortex (P < 0.05). The Dex-exposed animals exhibited higher hippocampal GR and mineralocorticoid receptor (MR) mRNA levels (P < 0.05). Beta-exposed females showed reduced fecundity (P < 0.05). In Dex-exposed females there was a lower male to female sex ratio. In conclusion, prenatal sGC exposure affects HPA axis activity, in a cycle-dependent manner, and long-term reproductive success. The clinical implications of the findings on endocrine function and pregnancy in females are profound and further follow-up is warranted in human cohorts. Furthermore, we have shown there are considerable difference in phenotypes between the Beta- and Dex-exposed females and the specific endocrine and maternal outcome is contingent on the specific sGCs administered during pregnancy.

Effects of maternal dexamethasone treatment in early pregnancy on pituitary-adrenal axis in fetal sheep

Fetal exposure to elevated levels of bioactive glucocorticoids early in gestation, as in suspected cases of congenital adrenal hyperplasia, may result in adverse neurological events. Fetal hypothalamic-pituitary-adrenal development and function may be involved. We investigated immediate and long-term effects of maternal dexamethasone (DEX) administration early in pregnancy on fetal growth and pituitary-adrenal activity in sheep. Pregnant ewes carrying singleton fetuses (total n = 119) were randomized to control (2 ml saline/ewe) or DEX-treated groups (im injections of 0.14 mg/kg ewe weight . 12 h) at 40-41 d gestation (dG). At 50, 100, 125, and 140 dG, fetal plasma and tissues were collected. DEX-exposed fetuses were lighter than controls at 100 dG (P < 0.05) but not at any other times. Fetal plasma ACTH levels and pituitary POMC and PC-1 mRNA levels were similar between groups. Fetal plasma cortisol levels were significantly reduced after DEX exposure in both male and female fetuses at 50 dG (P < 0.05), were similar at 100 and 125 dG, but were significantly higher than controls at 140 dG. At 140 dG, there was increased adrenal P450C(17) and 3beta-HSD mRNA in female fetuses and reduced expression of ACTH-R mRNA in males. Fetal hepatic CBG mRNA levels mimicked plasma cortisol patterns. DEX exposure reduced CBG only in males at 50 dG (P < 0.05). Placental mRNA levels of 11beta-HSD2 were increased after DEX in males (P < 0.05). Therefore, in sheep, early DEX may alter the developmental trajectory of the fetal hypothalamic-pituitary-adrenal axis, directly increasing fetal adrenal activation but not anterior pituitary function. In females, this effect may be attributed, in part, to increased fetal adrenal steroidogenic activity.

Should we be prescribing repeated courses of antenatal corticosteroids?

Single-course treatment with antenatal corticosteroids has been shown to enhance fetal maturation before preterm birth and to improve outcomes for the preterm infant. Based on this success, practitioners expanded use of the treatment to repeated courses of antenatal corticosteroids ahead of evidence demonstrating benefit and excluding harm. Experiments with animals and cohort studies have provided a body of evidence suggesting that repeated doses may further improve lung maturation but may be accompanied by deleterious effects on the developing brain and other organs. Randomised controlled trials of repeated treatments to date have provided mixed evidence but in general may indicate a small benefit in terms of postnatal lung function, but this is accompanied by restricted growth which may include the brain. In view of the well-established role that corticosteroids are known to play in brain development, and the marginal difference that repeated courses may make to outcome in the context of modern neonatal care, antenatal corticosteroid treatments should be restricted to single-course treatment.