Glucocorticoid programming of adult disease

Glucocorticoid receptor expression as an integrative measure to assess glucocorticoid plasticity and efficiency in evolutionary endocrinology: A perspective

Organisms have to cope with the changes that take place in their environment in order to keep their physical and psychological stability. In vertebrates, the hypothalamic-pituitary-adrenal (HPA) axis plays a key role in mediating phenotypic adjustments to environmental changes, primarily by regulating glucocorticoids (GCs). Although circulating GCs have widely been used as proxy for individual health and fitness, our understanding of HPA regulation is still very limited, especially in free-living animals. Circulating GCs only exert their actions when they are bound to receptors, and therefore, GC receptors play a pivotal role mediating HPA regulation and GC downstream phenotypic changes. Because under challenging conditions GC actions (as well as negative feedback activation) occur mainly through binding to low-affinity glucocorticoid receptors (GR), we propose that GR activity, and in particular GR expression, may play a crucial role in GC regulation and dynamics, and be ultimately related to organismal capacity to appropriately respond to environmental changes. Thus, we suggest that GR expression will provide more comprehensive information of GC variation and function. To support this idea, we compile previous evidence demonstrating the fundamental role of GR on GC responses and the fine-tuning of circulating GCs. We also make predictions about the phenotypic differences in GC responsiveness - and ultimately HPA regulation capacity - associated with differences in GR expression, focusing on GC plasticity and efficiency. Finally, we discuss current priorities and limitations of integrating measures of GR expression into evolutionary endocrinology and ecology studies, and propose further research directions towards the use of GR expression and the study of the mechanisms regulating GR activity to gather information on coping strategies and stress resilience. Our goals are to provide an integrative perspective that will prompt reconsideration on the ecological and physiological interpretation of current GC measurements, and motivate further research on the role of GR in tuning individual responses to dynamic environments.

The fetal inflammatory response syndrome: the origins of a concept, pathophysiology, diagnosis, and obstetrical implications

The fetus can deploy a local or systemic inflammatory response when exposed to microorganisms or, alternatively, to non-infection-related stimuli (e.g., danger signals or alarmins). The term "Fetal Inflammatory Response Syndrome" (FIRS) was coined to describe a condition characterized by evidence of a systemic inflammatory response, frequently a result of the activation of the innate limb of the immune response. FIRS can be diagnosed by an increased concentration of umbilical cord plasma or serum acute phase reactants such as C-reactive protein or cytokines (e.g., interleukin-6). Pathologic evidence of a systemic fetal inflammatory response indicates the presence of funisitis or chorionic vasculitis. FIRS was first described in patients at risk for intraamniotic infection who presented preterm labor with intact membranes or preterm prelabor rupture of the membranes. However, FIRS can also be observed in patients with sterile intra-amniotic inflammation, alloimmunization (e.g., Rh disease), and active autoimmune disorders. Neonates born with FIRS have a higher rate of complications, such as early-onset neonatal sepsis, intraventricular hemorrhage, periventricular leukomalacia, and death, than those born without FIRS. Survivors are at risk for long-term sequelae that may include bronchopulmonary dysplasia, neurodevelopmental disorders, such as cerebral palsy, retinopathy of prematurity, and sensorineuronal hearing loss. Experimental FIRS can be induced by intra-amniotic administration of bacteria, microbial products (such as endotoxin), or inflammatory cytokines (such as interleukin-1), and animal models have provided important insights about the mechanisms responsible for multiple organ involvement and dysfunction. A systemic fetal inflammatory response is thought to be adaptive, but, on occasion, may become dysregulated whereby a fetal cytokine storm ensues and can lead to multiple organ dysfunction and even fetal death if delivery does not occur ("rescued by birth"). Thus, the onset of preterm labor in this context can be considered to have survival value. The evidence so far suggests that FIRS may compound the effects of immaturity and neonatal inflammation, thus increasing the risk of neonatal complications and long-term morbidity. Modulation of a dysregulated fetal inflammatory response by the administration of antimicrobial agents, anti-inflammatory agents, or cell-based therapy holds promise to reduce infant morbidity and mortality.

Cardiovascular effects of prenatal stress-Are there implications for cerebrovascular, cognitive and mental health outcome?

Prenatal stress programs offspring cognitive and mental health outcome. We reviewed whether prenatal stress also programs cardiovascular dysfunction which potentially modulates cerebrovascular, cognitive and mental health disorders. We focused on maternal stress and prenatal glucocorticoid (GC) exposure which have different programming effects. While maternal stress induced cortisol is mostly inactivated by the placenta, synthetic GCs freely cross the placenta and have different receptor-binding characteristics. Maternal stress, particularly anxiety, but not GC exposure, has adverse effects on maternal-fetal circulation throughout pregnancy, probably by co-activation of the maternal sympathetic nervous system, and by raising fetal catecholamines. Both effects may impair neurodevelopment. Experimental data also suggest that severe maternal stress and GC exposure during early and mid-gestation may increase the risk for cardiovascular disorders. Human data are scarce and especially lacking for older age. Programming mechanisms include aberrations in cardiac and kidney development, and functional changes in the renin-angiotensin-aldosterone-system, stress axis and peripheral and coronary vasculature. Adequate experimental or human studies examining the consequences for cerebrovascular, cognitive and mental disorders are unavailable.

Prenatal therapeutics and programming of cardiovascular function

Cardiovascular diseases (CVD) are a leading cause of mortality worldwide. Despite recognizing the importance of risk factors in dictating CVD susceptibility and onset, patient treatment remains a challenging endeavor. Increasingly, the benefits of prevention and mitigation of risk factors earlier in life are being acknowledged. The developmental origins of health and disease posits that insults during specific periods of development can influence long-term health outcomes; this occurs because the developing organism is highly plastic, and hence vulnerable to environmental perturbations. By extension, targeted therapeutics instituted during critical periods of development may confer long-term protection, and thus reduce the risk of CVD in later life. This review provides a brief overview of models of developmental programming, and then discusses the impact of perinatal therapeutic interventions on long-term cardiovascular function in the offspring. The discussion focuses on bioactive food components, as well as pharmacological agents currently approved for use in pregnancy; in short, those agents most likely to be used in pregnancy and early childhood.

Does growth impairment underlie the adverse effects of dexamethasone on development of noradrenergic systems?

Glucocorticoids are given in preterm labor to prevent respiratory distress but these agents evoke neurobehavioral deficits in association with reduced brain region volumes. To determine whether the neurodevelopmental effects are distinct from growth impairment, we gave developing rats dexamethasone at doses below or within the therapeutic range (0.05, 0.2 or 0.8 mg/kg) at different stages: gestational days (GD) 17-19, postnatal days (PN) 1-3 or PN7-9. In adolescence and adulthood, we assessed the impact on noradrenergic systems in multiple brain regions, comparing the effects to those on somatic growth or on brain region growth. Somatic growth was reduced with exposure in all three stages, with greater sensitivity for the postnatal regimens; brain region growth was impaired to a lesser extent. Norepinephrine content and concentration were reduced depending on the treatment regimen, with a rank order of deficits of PN7-9 > PN1-3 > GD17-19. However, brain growth impairment did not parallel reduced norepinephrine content in magnitude, dose threshold, sex or regional selectivity, or temporal pattern, and even when corrected for reduced brain region weights (norepinephrine per g tissue), the dexamethasone-exposed animals showed subnormal values. Regression analysis showed that somatic growth impairment accounted for an insubstantial amount of the reduction in norepinephrine content, and brain growth impairment accounted for only 12%, whereas specific effects on norepinephrine accounted for most of the effect. The adverse effects of dexamethasone on noradrenergic system development are not simply related to impaired somatic or brain region growth, but rather include specific targeting of neurodifferentiation.

Developmental neurotoxicity resulting from pharmacotherapy of preterm labor, modeled in vitro: Terbutaline and dexamethasone, separately and together

Terbutaline and dexamethasone are used in the management of preterm labor, often for durations of treatment exceeding those recommended, and both have been implicated in increased risk of neurodevelopmental disorders. We used a variety of cell models to establish the critical stages at which neurodifferentiation is vulnerable to these agents and to determine whether combined exposures produce a worsened outcome. Terbutaline selectively promoted the initial emergence of glia from embryonic neural stem cells (NSCs). The target for terbutaline shifted with developmental stage: at later developmental stages modeled with C6 and PC12 cells, terbutaline had little effect on glial differentiation (C6 cells) but impaired the differentiation of neuronotypic PC12 cells into neurotransmitter phenotypes. In contrast to the specificity shown by terbutaline, dexamethasone affected both neuronal and glial differentiation at all stages, impairing the emergence of both cell types in NSCs but with a much greater impairment for glia. At later stages, dexamethasone promoted glial cell differentiation (C6 cells), while shifting neuronal cell differentiation so as to distort the balance of neurotransmitter phenotypes (PC12 cells). Finally, terbutaline and dexamethasone interacted synergistically at the level of late stage glial cell differentiation, with dexamethasone boosting the ability of terbutaline to enhance indices of glial cell growth and neurite formation while producing further decrements in glial cell numbers. Our results support the conclusion that terbutaline and dexamethasone are directly-acting neuroteratogens, and further indicate the potential for their combined use in preterm labor to worsen neurodevelopmental outcomes.

Carbenoxolone exposure during late gestation in rats alters placental expressions of p53 and estrogen receptors

Gestational carbenoxolone exposure inhibits placental 11β-hydroxysteroid dehydrogenase (11β-HSD), the physiological barrier for glucocorticoids, which increases fetal exposure to glucocorticoids and induces intrauterine growth restriction (IUGR). We hypothesized that carbenoxolone exposure influences the expression of placental estrogen receptors-α and β (ERα & ERβ) and p53 leading to inhibited fetal and placental growth. Pregnant Sprague-Dawley rats were injected twice daily with either carbenoxolone (10mg/kg; s.c.) or vehicle (control group) from gestational days (dg) 12 onwards. Maternal blood and placentas were collected on 16 dg, 19 dg and 21 dg. The expression of ERα, ERβ and p53 were studied in placental basal and labyrinth zones by RT-PCR, Western blotting and immunohistochemistry. Carbenoxolone did not affect placental and fetal body weights, but ELISA showed decreased estradiol levels on 19 dg and 21 dg, and increased maternal luteinizing hormone levels on all dg. The follicle stimulating hormone levels decreased on 16 dg and 19 dg, and increased on 21 dg. Carbenoxolone decreased ERα mRNA levels on 16 dg in both zones and its protein level on 19 dg in the labyrinth zone. However, carbenoxolone increased ERβ mRNA levels on 19 dg and 21 dg and protein levels on 16 dg and 19 dg in the labyrinth zone. The p53 mRNA levels increased on all dg, but its protein levels increased on 21 dg in both zones. In conclusion, carbenoxolone exposure changes placental p53, ERα, ERβ expression in favor of cell death but these changes do not induce IUGR in rats.

Maternal corticosterone exposure in the mouse programs sex-specific renal adaptations in the renin-angiotensin-aldosterone system in 6-month offspring

Short‐term maternal corticosterone (Cort) administration at mid‐gestation in the mouse reduces nephron number in both sexes while programming renal and cardiovascular dysfunction in 12‐month male but not female offspring. The renal renin–angiotensin–aldosterone system (RAAS), functions in a sexually dimorphic manner to regulate both renal and cardiovascular physiology. This study aimed to identify if there are sex‐specific differences in basal levels of the intrarenal RAAS and to determine the impact of maternal Cort exposure on the RAAS in male and female offspring at 6 months of age. While intrarenal renin concentrations were higher in untreated females compared to untreated males, renal angiotensin II concentrations were higher in males than females. Furthermore, basal plasma aldosterone concentrations were greater in females than males. Cort exposed male but not female offspring had reduced water intake and urine excretion. Cort exposure increased renal renin concentrations and elevated mRNA expression of Ren1, Ace2, and Mas1 in male but not female offspring. In addition, male Cort exposed offspring had increased expression of the aldosterone receptor, Nr3c2 and renal sodium transporters. In contrast, Cort exposure increased Agtr1a mRNA levels in female offspring only. This study demonstrates that maternal Cort exposure alters key regulators of renal function in a sex‐specific manner at 6 months of life. These finding likely contribute to the disease outcomes in male but not female offspring in later life and highlights the importance of renal factors other than nephron number in the programming of renal and cardiovascular disease.

Protective effect of early prenatal stress on the induction of asthma in adult mice: Sex-specific differences

Adversities faced during the prenatal period can be related to the onset of diseases in adulthood. However, little is known about the effects on the respiratory system. This study aimed to evaluate the effects of prenatal stress in two different time-points during pregnancy on pulmonary function and on the inflammatory profile of mice exposed to an asthma model. Male and female BALB/c mice were divided into 3 groups: control (CON), prenatal stress from the second week of pregnancy (PNS1) and prenatal stress on the last week of pregnancy (PNS2). Both PNS1 and PNS2 pregnant females were submitted to restraint stress. As adults, fear/anxiety behaviors were assessed, and animals were subjected to an asthma model induced by ovalbumin. Pulmonary function, inflammatory parameters in bronchoalveolar lavage (BAL) and histology were evaluated. There was a significant decrease in the number of entries and time spent in the central quadrant on the open field test for the PNS1 animals. Females (PNS1) showed improved pulmonary function (airway resistance, tissue damping and pulmonary elastance), significant increase in the percentage of neutrophils and lymphocytes and a decrease in eosinophils when compared to controls. There was a significant decrease in inflammatory cytokines in BAL of both males (IL-5 and IL-13) and females (IL-4, IL-5 and IL-13) from PNS1 and PNS2 when compared to the CON group. Prenatal stress starting from the beginning of pregnancy reduces the impact of asthma development in adult female mice, showing an improved pulmonary function and a lower inflammatory response in the lungs.

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.

A review of the genetic and epigenetic factors affecting lamb survival

Poor lamb survival pre-weaning is a major source of reproductive inefficiency in Australian sheep flocks. While nutrition and management options have been extensively researched and promoted to improve lamb survival, the present review focuses on the prospects for obtaining genetic gain and helps identify selection strategies for boosting such gains to improve overall reproductive efficiency in the Australian sheep industry. Estimated heritability for lamb survival using linear model analysis is low, although use of threshold models suggests that heritability could be higher, which, if true, could help explain the substantial genetic gains obtained in long-term selection experiments. Epigenetic mechanisms may hinder selection and quantitative trait-loci identification through confounding and/or masking genetic variances and co-variances. With sufficient information, these effects could be considered in genetic evaluations by identifying those components that are amenable to selection. Regarding indirect selection, finding effective criteria for improving lamb survival has proved elusive. Most measures of maternal behaviour, temperament and lambing difficulty researched are poorly correlated genetically with lamb survival. Of lamb behaviours and thermo-genic indicators studied, latency to bleat following handling by humans is moderately genetically correlated with lamb survival, as is neonatal rectal temperature. Industry application remains to be adequately explored for the more promising of these measures. Finally, in lieu of direct selection for lamb survival, there is merit in selecting for multiple-rearing ability or its equivalent, possibly with additional selection criteria for lamb survival and reproductive efficiency.

Prenatal dexamethasone augments the neurobehavioral teratology of chlorpyrifos: significance for maternal stress and preterm labor

Glucocorticoids are the consensus treatment given in preterm labor and are also elevated by maternal stress; organophosphate exposures are virtually ubiquitous, so human developmental coexposures to these two agents are common. This study explores how prenatal dexamethasone exposure modifies the neurobehavioral teratology of chlorpyrifos, one of the most widely used organophosphates. We administered dexamethasone to pregnant rats on gestational days 17-19 at a standard therapeutic dose (0.2 mg/kg); offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1 mg/kg) that produces barely-detectable (<10%) inhibition of brain cholinesterase activity. Dexamethasone did not alter brain chlorpyrifos concentrations, nor did either agent alone or in combination affect brain thyroxine levels. Assessments were carried out from adolescence through adulthood encompassing T-maze alternation, Figure 8 maze (locomotor activity, habituation), novelty-suppressed feeding and novel object recognition tests. For behaviors where chlorpyrifos or dexamethasone individually had small effects, the dual exposure produced larger, significant effects that reflected additivity (locomotor activity, novelty-suppressed feeding, novel object recognition). Where the individual effects were in opposite directions or were restricted to only one agent, we found enhancement of chlorpyrifos' effects by prenatal dexamethasone (habituation). Finally, for behaviors where controls displayed a normal sex difference in performance, the combined treatment either eliminated or reversed the difference (locomotor activity, novel object recognition). Combined exposure to dexamethasone and chlorpyrifos results in a worsened neurobehavioral outcome, providing a proof-of-principle that prenatal glucocorticoids can create a subpopulation with enhanced vulnerability to environmental toxicants.

Prenatal dexamethasone augments the sex-selective developmental neurotoxicity of chlorpyrifos: implications for vulnerability after pharmacotherapy for preterm labor

Glucocorticoids are routinely given in preterm labor and are also elevated by maternal stress; organophosphate exposures are virtually ubiquitous, so coexposures to these two agents are pervasive. We administered dexamethasone to pregnant rats on gestational days 17-19 at a standard therapeutic dose (0.2mg/kg); offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1mg/kg) that produces barely-detectable (<10%) inhibition of brain cholinesterase activity. We evaluated indices for acetylcholine (ACh) synaptic function throughout adolescence, young adulthood and later adulthood, in brain regions possessing the majority of ACh projections and cell bodies; we measured nicotinic ACh receptor binding, hemicholinium-3 binding to the presynaptic choline transporter and choline acetyltransferase activity, all known targets for the adverse developmental effects of dexamethasone and chlorpyrifos given individually. Dexamethasone did not enhance the systemic toxicity of chlorpyrifos, as evidenced by weight gain and measurements of cholinesterase inhibition during chlorpyrifos treatment. Nevertheless, it enhanced the loss of presynaptic ACh function selectively in females, who ordinarily show sparing of organophosphate developmental neurotoxicity relative to males. Females receiving the combined treatment showed decrements in choline transporter binding and choline acetyltransferase activity that were unique (not found with either treatment alone), as well as additive decrements in nicotinic receptor binding. On the other hand, males given dexamethasone showed no augmentation of the effects of chlorpyrifos. Our findings indicate that prior dexamethasone exposure could create a subpopulation that is especially vulnerable to the adverse effects of organophosphates or other developmental neurotoxicants.

Role of glucocorticoid in developmental programming: evidence from zebrafish

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

Maternal corticosterone exposure in the mouse has sex-specific effects on placental growth and mRNA expression

Maternal exposure to increased synthetic glucocorticoids (GC) during pregnancy is known to disturb fetal development and increase the risk of long-term disease. Maternal exposure to elevated levels of natural GC is likely to be common yet is relatively understudied. The placenta plays an important role in regulating fetal exposure to maternal GC but is itself vulnerable to maternal insults. This study uses a mouse model of maternal corticosterone (Cort) exposure to investigate its effects on the developing placenta. Mice were treated with Cort (33 μg/kg·h) for 60 h starting at embryonic d 12.5 (E12.5) before collection of placentas at E14.5 and E17.5. Although Cort exposure did not affect fetal size, placentas of male fetuses were larger at E17.5 in association with changes in placental Igf2. This increase in size was associated with an increase in placental thickness and an increase in placental junctional zone volume. Placentas from female fetuses were of normal size and had no changes in growth factor mRNA levels. The expression of the protective enzyme 11β-hydroxysteroid dehydrogenase type 2 was increased at E14.5 but was decreased in males at E17.5. In contrast, the expression of Nr3c1 (which encodes the GC receptor) was increased during the Cort exposure and remained elevated at E17.5 in the placentas of male fetuses. Our study has shown that maternal Cort exposure infers a sex-specific alteration to normal placental growth and growth factor expression, thus further adding to our understanding of the mechanisms of male dominance of programmed disease.

Chlorpyrifos developmental neurotoxicity: interaction with glucocorticoids in PC12 cells

Prenatal coexposures to glucocorticoids and organophosphate pesticides are widespread. Glucocorticoids are elevated by maternal stress and are commonly given in preterm labor; organophosphate exposures are virtually ubiquitous. We used PC12 cells undergoing neurodifferentiation in order to assess whether dexamethasone enhances the developmental neurotoxicity of chlorpyrifos, focusing on models relevant to human exposures. By themselves, each agent reduced the number of cells and the combined exposure elicited a correspondingly greater effect than with either agent alone. There was no general cytotoxicity, as cell growth was actually enhanced, and again, the combined treatment evoked greater cellular hypertrophy than with the individual compounds. The effects on neurodifferentiation were more complex. Chlorpyrifos alone had a promotional effect on neuritogenesis whereas dexamethasone impaired it; combined treatment showed an overall impairment greater than that seen with dexamethasone alone. The effect of chlorpyrifos on differentiation into specific neurotransmitter phenotypes was shifted by dexamethasone. Either agent alone promoted differentiation into the dopaminergic phenotype at the expense of the cholinergic phenotype. However, in dexamethasone-primed cells, chlorpyrifos actually enhanced cholinergic neurodifferentiation instead of suppressing this phenotype. Our results indicate that developmental exposure to glucocorticoids, either in the context of stress or the therapy of preterm labor, could enhance the developmental neurotoxicity of organophosphates and potentially of other neurotoxicants, as well as producing neurobehavioral outcomes distinct from those seen with either individual agent.

Dexamethasone enhances oxidative stress-induced cell death in murine neural stem cells

Glucocorticoids (GCs) are essential for normal brain development; however, there is consistent evidence that prenatal exposure of the fetal brain to excess GCs permanently modifies the phenotype of neuronal cells. In this paper, the murine-derived multipotent stem cell line C17.2 was used, as an in vitro model, to investigate the impact of GCs on neural stem cell survival. Our results indicate that dexamethasone (Dex) increases the sensitivity of murine neural stem cells (NSCs) to 2,3-methoxy-1,4-naphthoquinone-induced apoptosis, and this effect could be blocked by the glucocorticoid-receptor (GR) antagonist mifepristone, strongly suggesting the involvement of the GR. Furthermore, our results show that Dex decreases cell number and induces a G1-arrest. We hypothesized that the mitochondria are the main target of Dex. Interestingly, after treatment with Dex, 72% of the investigated genes involved in the mitochondrial respiratory chain are down-regulated, as well as 29% of the genes encoding for antioxidant enzymes. In conclusion, using the C17.2 cell line as a model to study developmental neurotoxicity in vitro, we have shown that GCs can increase cellular sensitivity to oxidative stress and alter the phenotype of NCSs.

Sex specific changes in placental growth and MAPK following short term maternal dexamethasone exposure in the mouse

OBJECTIVES

Maternal glucocorticoid (GC) exposure during pregnancy can alter fetal development and program the onset of disease in adult offspring. The placenta helps protect the fetus from excess GC exposure but is itself susceptible to maternal insults and may be involved in sex dependant regulation of fetal programming. This study aimed to investigate the effects of maternal GC exposure on the developing placenta.

STUDY DESIGN AND MAIN OUTCOME MEASURES

Pregnant mice were treated with dexamethasone (DEX-1 μg/kg/h) or saline (SAL) for 60 h via minipump beginning at E12.5. Placentas were collected at E14.5 and E17.5 and the expression of growth factors and placental transporters examined by real-time PCR and/or Western blot. Histological analysis was performed to assess for morphological changes.

RESULTS

At E14.5, DEX exposed male and female fetuses had a lower weight compared to SAL animals but placental weight was lower in females only. Hsd11b2 and Vegfa gene expression was increased and MAPK1 protein expression decreased in the placentas of females only. At E17.5 placental and fetal body weights were similar and differences in MAPK were no longer present although HSD11B2 protein was elevated in placentas of DEX females. Levels of glucose or amino acid transporters were unaffected.

CONCLUSIONS

Results suggest sex specific responses to maternal GCs within the placenta. Decreased levels of MAPK protein in placentas of female fetuses suggest alterations in the MAPK pathway may contribute to the lower placental weights in this sex. This may contribute towards sex specific fetal programming of adult disease.

Mimicking maternal smoking and pharmacotherapy of preterm labor: fetal nicotine exposure enhances the effect of late gestational dexamethasone treatment on noradrenergic circuits

Smoking during pregnancy increases the risk of preterm delivery, which in turn necessitates the common use of glucocorticoids to prevent respiratory distress syndrome. Accordingly, there is a substantial population exposed conjointly to fetal nicotine and glucocorticoids (typically dexamethasone). We administered nicotine to pregnant rats throughout gestation, using a regimen (3 mg/kg/day by osmotic minipump) that maintains plasma nicotine levels within the range seen in smokers; on gestational days 17, 18 and 19, we gave 0.2 mg/kg of dexamethasone. We assessed norepinephrine levels in three brain regions (frontal/parietal cortex, brainstem, cerebellum) throughout adolescence, young adulthood and later adulthood, and contrasted the persistent effects with comparable measures in peripheral tissues (heart, liver). In adolescence, males showed initial deficits in the frontal/parietal cortex with either dexamethasone alone or the combined treatment, with resolution to normal by young adulthood; the group exposed to both nicotine+dexamethasone showed subsequent elevations that emerged in full adulthood and persisted through five months of age, an effect not seen with either agent separately. In females, the combined exposure produced an initial deficit that resolved by young adulthood, without any late-emerging changes. We did not see comparable effects in the other brain regions or peripheral tissues. This indicates that nicotine exposure sensitizes the developing brain to the adverse effects of dexamethasone treatment, producing sex-selective changes in innervation and/or activity of specific noradrenergic circuits. The fact that the combined treatment produced greater effects points to potentially worsened neurobehavioral outcomes after pharmacotherapy of preterm labor in the offspring of smokers.

The conflicting effects of maternal nutrient restriction and early-life obesity on renal health

Epidemiological and animal studies have demonstrated that early-life nutrition alters the metabolic responses and generates structural changes in complex tissues, such as the kidneys, which may lead to a reduction in the offspring lifespan. Independently, obesity induces a spontaneous low-grade chronic inflammatory response by modulating several of the major metabolic pathways that ultimately compromise long-term renal health. However, the combined effects of maternal nutrition and early-life obesity in the development of renal diseases are far from conclusive. Previous results, using the ovine model, demonstrated that the combination of a reduction in fetal nutrition and juvenile obesity induced a series of adaptations associated with severe metabolic syndrome in the heart and adipose tissue. Surprisingly, exposure to an obesogenic environment in the kidney of those offspring produced an apparent reduction in glomerulosclerosis in relation to age- and weight-matched controls. However, this reduction in cellular apoptosis was accompanied by a rise in glomerular filtration rate and blood pressure of equal intensity when compared with obese controls. The intention of this review is to explain the adaptive responses observed in this model, based on insights into the mechanism of renal fetal programming, and their potential interactions with some of the metabolic changes produced by obesity.

The impact of maternal cortisol concentrations on child arterial elasticity

Epidemiological studies suggest that glucocorticoid excess in the fetus may contribute to the pathophysiology of cardiovascular diseases in adulthood. However, the impact of maternal glucocorticoid on the cardiovascular system of the offspring has not been much explored in studies involving humans, especially in childhood. The objective of this study was to assess the influence of maternal cortisol concentrations on child arterial elasticity. One hundred and thirty pregnant women followed from 1997 to 2000, and respective children 5–7 years of age followed from 2004 to 2006 were included in the study. Maternal cortisol was determined in saliva by an enzyme immunoassay utilizing the mean concentration of nine samples of saliva. Arterial elasticity was assessed by the large artery elasticity index (LAEI; the capacitive elasticity of large arteries) by recording radial artery pulse wave, utilizing the equipment HDI/PulseWave CR-2000 Cardiovascular Profiling System®. The nutritional status of the children was determined by the body mass index (BMI). Insulin concentration was assessed by chemiluminescence, and insulin resistance by the homeostasis model assessment. Blood glucose, total cholesterol and fractions (LDL-c and HDL-c) and triglyceride concentrations were determined by automated enzymatic methods. The association between maternal cortisol and child arterial elasticity was assessed by multivariate linear regression analysis. There was a statistically significant association between maternal cortisol and LAEI (P= 0.02), controlling for birth weight, age, BMI and HDL-c of the children. This study suggests that exposure to higher glucocorticoid concentrations in the prenatal period is associated to lower arterial elasticity in childhood, an earlier cardiovascular risk marker.

Cushing's syndrome, glucocorticoids and the kidney

Glucocorticoids (GCs) affect renal development and function in fetal and mature kidneys both indirectly, by influencing the cardiovascular system, and directly, by their effects on glomerular and tubular function. Excess GCs due to endogenous GC overproduction in Cushing's syndrome or exogenous GC administration plays a pivotal role in hypertension and causes increased cardiac output, total peripheral resistance and renal blood flow. Glucocorticoids increase renal vascular resistance (RVR) in some species and experimental settings and decrease RVR in others. Short term administration of adrenocorticotrophic hormone or GCs causes an increased glomerular filtration rate (GFR) in humans, rats, sheep and dogs. Interestingly, chronic exposure may cause a decreased GFR in combination with a higher cardiovascular risk in human patients with Cushing's syndrome. Glomerular dysfunction leads to proteinuria and albuminuria in canine and human Cushing's patients, and some cases also show histological evidence of glomerulosclerosis. Tubular dysfunction is reflected by an impaired urinary concentrating ability and disturbed electrolyte handling, which can potentially result in increased sodium reabsorption, hypercalciuria and urolithiasis. Conversely, chronic kidney disease can also alter GC metabolism. More research needs to be performed to further evaluate the renal consequences of Cushing's syndrome because of its implications for therapeutic aspects as well as the general well-being of the patient. Because there is a high incidence of Cushing's syndrome in canines, which is similar to the syndrome in humans, dogs are an interesting animal model to investigate the link between hypercortisolism and renal function.

Mimicking maternal smoking and pharmacotherapy of preterm labor: interactions of fetal nicotine and dexamethasone on serotonin and dopamine synaptic function in adolescence and adulthood

Fetal coexposure to nicotine and dexamethasone is common: maternal smoking increases the incidence of preterm delivery and glucocorticoids are the consensus treatment for prematurity. We gave pregnant rats 3mg/kg/day of nicotine throughout gestation, a regimen that reproduces smokers' plasma levels, and then on gestational days 17, 18 and 19, we administered 0.2mg/kg of dexamethasone. We evaluated developmental indices for serotonin (5HT) and dopamine synaptic function throughout adolescence, young adulthood and later adulthood, assessing the brain regions possessing major 5HT and dopamine projections and cell bodies. Males displayed persistent upregulation of 5HT(1A) and 5HT(2) receptors and the 5HT transporter, with a distinct hierarchy of effects: nicotine<dexamethasone<combined treatment. Females showed downregulation of the 5HT(1A) receptor with the same rank order; both sexes displayed presynaptic hyperactivity of 5HT and dopamine pathways as evidenced by increased neurotransmitter turnover. Superimposed on these overall effects, there were significant differences in temporal and regional relationships among the different treatments, often involving effects that emerged later in life, after a period of apparent normality. This indicates that nicotine and dexamethasone do not simply produce an initial neuronal injury that persists throughout the lifespan but rather, they alter the developmental trajectory of synaptic function. The fact that the combined treatment produced greater effects for many parameters points to potentially worse neurobehavioral outcomes after pharmacotherapy of preterm labor in the offspring of smokers.

The relationship between cortisol concentrations in pregnancy and systemic vascular resistance in childhood

OBJECTIVE

To assess the relationship between cortisol concentrations in the last trimester of pregnancy and systemic vascular resistance - SVR in childhood.

MATERIALS AND METHODS

This study is part of a cohort involving 130 Brazilian pregnant women and their children, ages 5 to 7years. Maternal cortisol was determined in saliva by an enzyme immunoassay utilizing the mean concentration of 9 samples of saliva (3 in each different day), collected at the same time, early in the morning. SVR was assessed by the HDI/PulseWave CR-2000 Cardiovascular Profiling System(R). Socioeconomic and demographic characteristics and life style factors were determined by a questionnaire. The nutritional status of the women and children was assessed by the body mass index - BMI. The association between maternal cortisol and SVR in childhood was calculated by multivariate linear regression analysis.

RESULTS

There were statistically significant associations between maternal cortisol and SVR (p=0.043) and BMI-z score of the children (p=0.027), controlling for maternal BMI, birth weight, age, and gender of the children.

CONCLUSION

As far as we know this is the first study in the literature assessing the association between cortisol concentrations in pregnancy and SVR in childhood. Overall, the data suggest that exposure to excess glucocorticoid in the prenatal period is associated to vascular complications in childhood, predisposing to cardiovascular diseases in later life.

Prenatal stress programming of offspring feeding behavior and energy balance begins early in pregnancy

To examine the long-term effects of stress experienced early in gestation on the programming of offspring feeding behaviors and energy balance, pregnant mice were exposed to stress during early pregnancy (days 1-7) and adult offspring examined on chow and high fat diets for long-term outcomes. Placental 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) and insulin-like growth factor 2 (IGF-2) expression was measured to determine the possible sex-specific contribution of prenatal stress (PNS) on fetal programming of embryo growth and development during early pregnancy. PNS mice showed a basal hyperphagia when on chow diet. Prenatal treatment differences were ameliorated when adult mice were on a high fat diet. Interestingly, PNS male mice also had significantly reduced body weights compared to control males on both chow and high fat diets. Body composition analyses revealed reduced body fat and increased lean mass in PNS mice on the high fat diet, but no differences were detected in plasma leptin or insulin-like growth factor 1 (IGF-1) levels. Mechanistic examination of gene expression in embryonic day 12 placentas found that early PNS was associated with increased IGF-2 expression and sex-dependent effects of stress on 11 beta-HSD2, supporting specific aspects of early pregnancy. These studies suggest that the long-term effects of stress during pregnancy on programming of feeding behavior and energy homeostasis begin much earlier in development than previously thought.

A nationwide study on the risk of autism after prenatal stress exposure to maternal bereavement

OBJECTIVE

Prenatal stress has been linked to several adverse neurobehavioral outcomes, which may share a common pathophysiology with autism. We aimed to examine whether prenatal stress exposure after maternal bereavement is associated with an increased risk of autism later in life.

METHODS

We conducted a nationwide population-based cohort study of all 1492709 singletons in Denmark born from 1978 to 2003. A total of 37275 children were born to women who lost a close relative during pregnancy or up to 1 year before pregnancy. These children were included in the exposed group, and the remaining children were in the unexposed group. All children were followed up from birth until their death, migration, onset of autism, or the end of 2006. Information on autism was obtained from the Danish Psychiatric Central Register. We used Cox regression models to estimate hazard ratios in the exposed group compared with those in the unexposed group.

RESULTS

Maternal bereavement during the prenatal period was not associated with an increased risk of autism in the offspring. The hazard ratios did not differ by the nature of the exposure (maternal relationship to the deceased or cause of death). The hazard ratios were comparable between the 5 prenatal exposure periods under study (7-12 months before pregnancy, 0-6 months before pregnancy, first trimester, second trimester, and third trimester).

CONCLUSIONS

This is the first population-based cohort study to examine the effect of prenatal stress on autism in childhood. Our data do not support any strong association between prenatal stress after maternal bereavement and the risk of autism.

Plasma and renal renin concentrations in adult sheep after prenatal betamethasone exposure

This study examined whether renin expression and secretion and plasma angiotensin II (Ang II) levels were altered in adult sheep exposed to antenatal betamethasone. Pregnant sheep received injections of 0.17 mg/kg betamethasone or vehicle, at 80 and 81 days of gestation, and offspring were studied at 6 and 18 months of age. At 6 months, plasma prorenin concentrations were significantly lower in betamethasone animals (4.63 +/- 0.64 vs 7.09 +/- 0.83 ng angiotensin I/mL/h, P < .01). The percentage of plasma active renin was significantly higher in the betamethasone group (31.93 +/- 4.09% vs 18.57 +/- 2.79%, P < .01). Plasma and renocortical renin levels were similar in both groups at 18 months, but plasma renin activity was lower than at 6 months. Ang II levels were suppressed by betamethasone. The data indicate that prenatal exposure to betamethasone alters processing and secretion of renin in offspring at 6 months, but that this difference is not apparent at 18 months.

Long-term low level glucocorticoid exposure induces persistent repression in chromatin

Environmental exposure to low concentration hormones can have permanent epigenetic effects in animals and humans. The consequence of long-term low concentration glucocorticoid exposure was investigated in cell culture using glucocorticoid responsive genes organized in alternative chromatin structures. The MMTV promoter is induced by short-term glucocorticoid exposure on either an integrated (normal chromatin) or transient (unstructured chromatin) promoter. Longer hormone treatment causes a transient refractory repression of only the integrated promoter. Exposure to low concentrations of hormone for several passages persistently represses the integrated MMTV and endogenous glucocorticoid responsive promoters. The glucocorticoid receptor cannot bind to persistently repressed promoters. Induction by androgens is also inhibited on the repressed MMTV promoter. Similarly, osmotic stress induction of the endogenous Sgk gene is repressed. Persistent repression by glucocorticoids targets glucocorticoid responsive genes using a chromatin-dependent mechanism that disrupts binding of both GR-dependent and GR-independent transcription complexes.

Developmental programming of a reduced nephron endowment: more than just a baby's birth weight

The risk of developing many adult-onset diseases, including hypertension, type 2 diabetes, and renal disease, is increased in low-birth-weight individuals. A potential underlying mechanism contributing to the onset of these diseases is the formation of a low nephron endowment during development. Evidence from the human, as well as many experimental animal models, has shown a strong association between low birth weight and a reduced nephron endowment. However, other animal models, particularly those in which the mother is exposed to elevated glucocorticoids for a short period, have shown a 20-40% reduction in nephron endowment without discernible changes in the birth weight of offspring. Such findings emphasize that a low birth weight is one, but certainly not the only, predictor of nephron endowment and suggests reduced nephron endowment and risk of developing adult-onset disease, even among normal-birth-weight individuals. Recognition of the dissociation between birth weight and nephron endowment is important for future studies aimed at elucidating the role of a reduced nephron endowment in the developmental programming of adult disease.

Evo-devo of infantile and childhood growth

Human size is a tradeoff between the evolutionary advantages and disadvantages of being small or big. We now propose that adult size is determined to an important extent during transition from infancy to childhood. This transition is marked by a growth spurt. A delay in the transition has a lifelong impact on stature and is responsible for 44% of children with short stature in developed countries and many more in developing countries. Here, we present the data and theory of an evolutionary adaptive strategy of plasticity in the timing of transition from infancy into childhood to match the prevailing energy supply. We propose that humans have evolved to withstand energy crises by decreasing their body size, and that evolutionary short-term adaptations to energy crises trigger a predictive adaptive response that modify the transition into childhood, culminating in short stature.

Genetic predisposition to hypertension sensitizes borderline hypertensive rats to the hypertensive effects of prenatal glucocorticoid exposure

An adverse intrauterine environment can increase the incidence of hypertension and other cardiovascular disease risk factors. However, in clinical and experimental studies the magnitude of the effect is variable. Possibly, the relative influence of the prenatal environment on cardiovascular disease is determined in part by genetic factors that predispose individuals to the development of environmentally induced hypertension. We tested this hypothesis by comparing the effects of prenatal dexamethasone treatment (Dex, 300 microg kg(-1) i.p. on days 15 and 16 of gestation) in borderline hypertensive rats (BHR) and control Wistar-Kyoto (WKY) rats. Blood pressure, heart rate and plasma corticosterone values were measured at rest during the middle of the day, and during 1 h of restraint stress in the adult offspring using indwelling arterial catheters implanted at least 4 days prior to data collection. Compared with the saline (vehicle) control treatment, prenatal dexamethasone significantly (P < 0.05) increased baseline mean arterial pressure in male (123 +/- 2 versus 131 +/- 3 mmHg, saline versus Dex) and female (121 +/- 2 versus 130 +/- 2 mmHg, saline versus Dex) BHR, but not in male (108 +/- 3 versus 113 +/- 2 mmHg, saline versus Dex) or female (112 +/- 2 versus 110 +/- 2 mmHg, saline versus Dex) WKY rats. Relative to saline treatment, prenatal Dex also significantly increased baseline heart rate (328 +/- 6 versus 356 +/- 5 beats min(-1), saline versus Dex) and plasma corticosterone (5 +/- 2 versus 24 +/- 4 microg dl(-1), saline versus Dex), and prolonged the corticosterone response to acute stress, selectively in female BHR. However, prenatal Dex significantly enhanced the arterial pressure response to acute stress only in female WKY, while Dex augmented the elevation in heart rate during stress only in male rats. We conclude that prenatal dexamethasone increased baseline arterial pressure selectively in BHR, and plasma corticosterone only in female BHR. In contrast, prenatal Dex enhanced cardiovascular reactivity to stress in both BHR and WKY rats.

The fetal inflammatory response syndrome

The fetal inflammatory response syndrome (FIRS) is a condition characterized by systemic inflammation and an elevation of fetal plasma interleukin-6. This syndrome has been observed in fetuses with preterm labor with intact membranes, preterm prelabor rupture of the membranes, and also fetal viral infections such as cytomegalovirus. FIRS is a risk factor for short-term perinatal morbidity and mortality after adjustment for gestational age at delivery and also for the development of long-term sequelae such as bronchopulmonary dysplasia and brain injury. Multiorgan involvement in FIRS has been demonstrated in the hematopoietic system, thymus, adrenal glands, skin, kidneys, heart, lung, and brain. This article reviews the fetal systemic inflammatory response as a mechanism of disease. Potential interventions to control an exaggerated inflammatory response in utero are also described.

Cortisol-cortisone ratios in small for gestational age (SGA) children without postnatal catch-up growth

OBJECTIVE

Low birthweight is a risk factor for metabolic and cardiovascular disorders in later adult life. Changes in the activity of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) and the consequent disequilibrium between cortisol (F) and cortisone (E) are thought to be a key mechanism for these effects. We investigated whether prenatal programming leads to alterations in F/E ratios on a systemic level.

DESIGN, PATIENTS AND METHODS

In a cross-sectional, retrospective study we analysed sera of 132 children born small for gestational age (SGA) (aged 2-13 years) with persistent short stature [< -2 standard deviation score (SDS)] and of 25 children born appropriate for gestational age (AGA) (aged 4-11 years) with normal body height. Thirty-one per cent of the SGA and 44% of the AGA children were born preterm. Serum E and F concentrations were measured using tandem mass spectrometry. To exclude species-specific effects, we studied the 11beta-HSD system by measuring the ratio of corticosterone (B) to dehydrocorticosterone (11OH-B) in rats that were born SGA after protein restriction of the female dams during pregnancy.

RESULTS

F, E and the F/E ratio in serum did not differ in these children when comparing SGA to children who were born AGA and had normal height. The concentrations were independent of weight and length SDS at birth as well as gestational age. In rats born SGA, the B/11OH-B ratio was not different to that in normal control animals at 6, 11 and 15 weeks of life.

CONCLUSION

We found no alterations in systemic cortisol-cortisone conversion either in short children born SGA or in SGA rats. However, local modifications of the 11beta-HSD system may be possible.

Animal models for small for gestational age and fetal programming of adult disease

Fetal growth retardation is a fetal adaptation in response to inadequate supply of oxygen and/or nutrients. Animal models of intrauterine growth retardation are an invaluable tool to question the genetic, molecular and cellular events that determine fetal growth and development. Rodent and non-litter bearing animals are mammalian system with similar embryology,anatomy and physiology to humans. Utilization of these systems has led to a greater understanding of the pathophysiology and consequences of intrauterine growth retardation. These observations are comparable to that observed in humans born small for gestational age, and are of interest because of the known association between poor fetal growth and development of adult disease. All the experimental manipulations described here have altered a number of metabolic and physiological variables, but the pattern of alterations seems to vary with the procedure and species employed. This review describes animal models for intrauterine growth retardation and assesses their potentials and limitations at aiming to improve strategies for the prevention of adult disease.

Altered 24-hour blood pressure profiles in children and adolescents with classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency

OBJECTIVE

Children and adolescents with classical congenital adrenal hyperplasia have been shown to be at risk for obesity associated with higher insulin and leptin levels. Because these factors are also known to cause hypertension, the aim of this study was to analyze 24-h blood pressure profiles and their relation to different clinical and laboratory parameters.

DESIGN

Fifty-five subjects, aged between 5.3 and 19.0 yr, were enrolled in a prospective, cross-sectional study. All patients had genetically proven 21-hydroxylase deficiency and underwent ambulatory 24-h blood pressure monitoring during a period off school/work. RESULTS (MEDIAN, RANGE): The median body mass index of the cohort was significantly elevated [1.09 sd score (SDS), -2.45 to 3.77]. Daytime and nighttime systolic blood pressures were also significantly elevated (0.67 SDS, -1.5-4.1; 0.63 SDS, -0.91 to 3.3), whereas daytime diastolic blood pressure was significantly lowered (-0.81 SDS, -2.6 to 3.2) and normal during the night (0.11 SDS, -2.0 to 2.0). Overall, there was a normal nocturnal drop of systolic (12.8%, 2.1-22.8) but not diastolic blood pressure (17.2%, 0.90-25.8). The different parameters of systolic and diastolic blood pressures were significantly correlated with body mass index and skinfold thickness (r(s) = 0.271-0.486). There was no correlation with equivalent hydrocortisone and fludrocortisone dosage and laboratory parameters except for serum leptin and insulin.

CONCLUSIONS

Our data show altered 24-h blood pressure profiles with elevated systolic levels correlated with the degree of overweight and obesity, whereas normal-weight patients tended to diastolic hypotension.

Maternal dexamethasone treatment at midgestation reduces nephron number and alters renal gene expression in the fetal spiny mouse

We investigated the effects of maternal glucocorticoid exposure in the spiny mouse, a precocial species with a relatively long gestation, few offspring, and in which nephrogenesis is complete before birth. We hypothesized that exposure of the fetus to glucocorticoids before the formation of glomeruli would result in adult hypertensive offspring with fewer nephrons. Furthermore, we hypothesized that this nephron deficit would result from changes in expression of genes involved in branching morphogenesis. Osmotic pumps implanted in pregnant spiny mice at midgestation (day 20) delivered dexamethasone (dex; 125 microg/kg) or saline for 60 h. Females were killed at day 23 of gestation and kidneys were frozen for real-time PCR analysis or allowed to deliver their offspring. At 20 wk of age, blood pressure was measured in the offspring for 1 wk before nephron number was determined using unbiased stereology. Males and females exposed to dex had significantly fewer nephrons (male: saline: 7,870 +/- 27, dex: 6,878 +/- 173; female: saline: 7,526 +/- 62, dex: 5,886 +/- 382; P < 0.001) compared with controls. Dex had no effect on basal blood pressure. Fetal kidneys collected at day 23 of gestation from dex-exposed mothers showed increased mRNA expression of BMP4 (P < 0.05), TGF-beta(1) (P < 0.05), genes known to inhibit branching morphogenesis and gremlin (P < 0.01), an antagonist of BMP4, compared with saline controls. This study shows for the first time an upregulation of branching morphogenic genes in the fetal kidney in a model of excess maternal glucocorticoids that leads to a nephron deficit in the adult. This study also provides evidence that a reduced nephron number does not necessarily lead to development of hypertension.

Acute and long-term effects of clinical doses of antenatal glucocorticoids in the developing fetal sheep kidney

OBJECTIVES

The controversy regarding potential long-term side effects of antenatal steroid administration for accelerating fetal lung maturation is still unresolved despite more than 30 years of experience. Studies in animals have demonstrated that administration of glucocorticoids during pregnancy alters renal expression of several key regulatory molecules at different developmental stages followed in most cases with the development of hypertension in the adult. We studied the effects of betamethasone on the expression of (1) NA,K-ATPAse pump; (2) the Na/H exchanger 3 (NAHE3); (3) angiotensin receptor (AT1 and AT2); and (4) the type 1 dopamine receptor (D1R).

METHODS

Pregnant sheep were treated with either 0.17 mg/kg betamethasone or vehicle 24 hours apart at 80 and 81 days' gestation. Fetal kidneys were harvested at 81 and 135 days' gestation. Protein and mRNA levels were measured in kidney cortex.

RESULTS

Betamethasone had acute and long-term effects on fetal kidney cortex gene expression. Acutely, mRNA abundance for AT2 was significantly lower and that of NHE3 significantly higher than in controls (0.4 +/- 0.02 vs 0.7 +/- 0.05; 1.2 +/- 0.16 vs 0.4 +/- 0.04; P < .05). At 135 days' gestation, AT2 receptor abundance remained lower than control (0.2 +/- 0.02 vs 0.4 +/- 0.02; P < .05), whereas D1R expression was higher (0.8 +/- 0.17 vs 0.5 +/- 0.06; P < .05). No changes in Na,K-ATPase of AT1 receptor at either of the two time points studied were observed. Antenatal steroid administration was not associated with premature labor or a reduction in either body weight or kidney weight.

CONCLUSION

Our findings strongly suggest that antenatal glucocorticoid administration according to National Institutes of Health (NIH) consensus guidelines may alter human fetal renal development. Further studies are needed to establish a direct relationship between alterations in fetal renal gene expression and the development of hypertension in adulthood.

Programming placental nutrient transport capacity

Many animal studies and human epidemiological findings have shown that impaired growth in utero is associated with physiological abnormalities in later life and have linked this to tissue programming during suboptimal intrauterine conditions at critical periods of development. However, few of these studies have considered the contribution of the placenta to the ensuing adult phenotype. In mammals, the major determinant of intrauterine growth is the placental nutrient supply, which, in turn, depends on the size, morphology, blood supply and transporter abundance of the placenta and on synthesis and metabolism of nutrients and hormones by the uteroplacental tissues. This review examines the regulation of placental nutrient transfer capacity and the potential programming effects of nutrition and glucocorticoid over-exposure on placental phenotype with particular emphasis on the role of the Igf2 gene in these processes.