Early metabolic defects in dexamethasone-exposed and undernourished intrauterine growth restricted rats

The Fetal Environment and the Development of Hypertension-The Epigenetic Modification by Glucocorticoids

Intrauterine growth restriction (IUGR) is a risk factor for postnatal cardiovascular, metabolic, and psychiatric disorders. In most IUGR models, placental dysfunction that causes reduced 11β-hydroxysteroid dehydrogenase 2 (11βHSD2) activity, which degrades glucocorticoids (GCs) in the placenta, resulting in fetal GC overexposure. This overexposure to GCs continues to affect not only intrauterine fetal development itself, but also the metabolic status and neural activity in adulthood through epigenetic changes such as microRNA change, histone modification, and DNA methylation. We have shown that the IUGR model induced DNA hypomethylation in the paraventricular nucleus (PVN) in the brain, which in turn activates sympathetic activities, the renin-angiotensin system (RAS), contributing to the development of salt-sensitive hypertension. Even in adulthood, strong stress and/or exogenous steroids have been shown to induce epigenetic changes in the brain. Furthermore, DNA hypomethylation in the PVN is also observed in other hypertensive rat models, which suggests that it contributes significantly to the origins of elevated blood pressure. These findings suggest that if we can alter epigenetic changes in the brain, we can treat or prevent hypertension.

Maternal Low-Protein Diet During Nursing Leads to Glucose-Insulin Dyshomeostasis and Pancreatic-Islet Dysfunction by Disrupting Glucocorticoid Responsiveness in Male Rats

Both perinatal malnutrition and elevated glucocorticoids are pivotal triggers of the growing global pandemic of metabolic diseases. Here, we studied the effects of metabolic stress responsiveness on glucose-insulin homeostasis and pancreatic-islet function in male Wistar offspring whose mothers underwent protein restriction during lactation. During the first two weeks after delivery, lactating dams were fed a low-protein (4% protein, LP group) or normal-protein diet (22.5% protein, NP group). At 90 days of age, male rat offspring were challenged with food deprivation (72 h of fasting), intracerebroventricular (icv) injection of dexamethasone (2 µL, 2.115 mmol/L) or chronic intraperitoneal injection of dexamethasone (1 mg/kg body weight/5 days). Body weight, food intake, intravenous glucose tolerance test (ivGTT) results, insulin secretion and biochemical parameters were assessed. LP rats did not display significant metabolic changes after long-term starvation (p > 0.05) or under the central effect of dexamethasone (p = 0.999). Chronic dexamethasone induced rapid hyperglycemia (~1.2-fold, p < 0.001) and hyperinsulinemia (NP: 65%; LP: 216%; p < 0.001), decreased insulin sensitivity (NP: ~2-fold; LP: ~4-fold; p < 0.001), reduced insulinemia (20%) and increased glycemia (35%) only in NP rats under ivGTT conditions (p < 0.001). Glucose and acetylcholine insulinotropic effects, as well as the muscarinic receptor antagonist response, were reduced by chronic dexamethasone only in pancreatic islets from NP rats (p < 0.05). The direct effect of dexamethasone on pancreatic islets reduced insulin secretion (NP: 60.2%, p < 0.001; LP: 33.8%, p < 0.001). Peripheral glucose-insulin dyshomeostasis and functional failure of pancreatic islets in LP rats, as evidenced by an impaired acute and chronic response to metabolic stress, may be due to excessive corticosterone action as a long-term consequence.

Gestational administration of vitamin D improves maternal care and prevents anxiety-like behavior in male and female Wistar rats prenatally exposed to dexamethasone

Prenatal overexposure to glucocorticoids (GC) can lead to behavioral changes in adulthood. We aimed to explore the effects of gestational administration of vitamin D on the behavioral responses of dams and their offspring prenatally exposed to dexamethasone (DEX). Vitamin D (500UI) was given daily during the whole pregnancy (VD group). Half of the groups that received vitamin D were treated with DEX (0.1 mg/kg, VD + DEX group) daily between the 14th and 19th days of pregnancy. The corresponding control groups of progenitors were assigned (CTL and DEX groups, respectively). Maternal care and the dam's behaviors were evaluated during lactation. The offspring had developmental and behavioral parameters evaluated during lactation and at 3, 6, and 12 months of age. Gestational administration of vitamin D increased maternal care and had an anxiolytic-like effect on the dams, but the latter was blocked in DEX-treated dams. Prenatal DEX partially impaired neural development and caused an anxiety-like phenotype in the male and female offspring at 6 months, which was prevented by gestational administration of vitamin D. As well, gestational vitamin D improved memory just in the male offspring, but this response was suppressed by prenatal DEX. We concluded that gestational vitamin D could prevent anxiety-like behavior in adult male and female rats prenatally exposed to DEX, which might be, in part, a result of the maternal care improvement.

Fetal growth restriction followed by early catch-up growth impairs pancreatic islet morphology in male rats

Fetal growth restriction (FGR), followed by postnatal early catch-up growth, is associated with an increased risk of metabolic dysfunction, including type 2 diabetes in humans. This study aims to determine the effects of FGR and early catch-up growth after birth on the pathogenesis of type 2 diabetes, with particular attention to glucose tolerance, pancreatic islet morphology, and fibrosis, and to elucidate its mechanism using proteomics analysis. The FGR rat model was made by inducing mild intrauterine hypoperfusion using ameroid constrictors (ACs). On day 17 of pregnancy, ACs were affixed to the uterine and ovarian arteries bilaterally, causing a 20.9% reduction in birth weight compared to sham pups. On postnatal day 4 (P4), the pups were assigned to either the good nutrition (GN) groups with 5 pups per dam to ensure postnatal catch-up growth or poor nutrition groups with 15 pups per dam to maintain lower body weight. After weaning, all pups were fed regular chow food ad libitum (P21). Rats in both FGR groups developed glucose intolerance; however, male rats in the FGR good nutrition (FGR-GN) group also developed hypertriglyceridemia and dysmorphic pancreatic islets with fibrosis. A comprehensive and functional analysis of proteins expressed in the pancreas showed that FGR, followed by early catch-up growth, severely aggravated cell adhesion-related protein expression in male offspring. Thus, FGR and early catch-up growth caused pancreatic islet morphological abnormalities and fibrosis associated with the disturbance of cell adhesion-related protein expressions. These changes likely induce glucose intolerance and dyslipidemia in male rats.

Perinatal stress exposure induced oxidative stress, metabolism disorder, and reduced GLUT-2 in adult offspring of rats

PURPOSE

Growing evidence has demonstrated that adversity in early life, especially in the prenatal and postnatal period, may change the programming of numerous body systems and cause the incidence of various disorders in later life. Accordingly, this experimental animal study aimed to investigate the effect of stress exposure during perinatal (prenatal and/or postnatal) on the induction of oxidative stress in the pancreas and its effect on glucose metabolism in adult rat offspring.

METHODS

In this experimental study based on maternal exposure to variable stress throughout the perinatal period, the pups were divided into eight groups, as follows: control group (C); prepregnancy, pregnancy, lactation stress group (PPPLS); prepregnancy stress group (PPS); pregnancy stress group (PS); lactation stress group (LS); prepregnancy, pregnancy stress group (PPPS); pregnancy, lactation stress group (PLS); and prepregnancy, lactation stress group (PPLS). Following an overnight fast on postnatal day (PND) 64, plasma glucose, insulin, leptin levels, and lipid profiles were evaluated in the offspring groups. GLUT-2 protein levels, lipid peroxidation, antioxidant status, and number of beta-cells in the pancreatic islets of Langerhans as well as the weights of intra-abdominal fat and adrenal glands were assessed. Levels of plasma corticosterone were determined in the different groups of mothers and offspring.

RESULTS

The levels of plasma corticosterone, insulin, and HOMA-B index increased, whereas glucose level and QUICKI index were reduced in the perinatal stress groups compared to C group (p < 0.001 to p < 0.05). Plasma triglyceride, LDL, and cholesterol level rose significantly, but HDL level decreased in the perinatal stress groups compared to C group (p < 0.001 to p < 0.05). Perinatal stress raised MDA concentrations and reduced the activities of antioxidant enzymes in plasma and pancreas compared to C group (p < 0.001 to p < 0.05). GLUT-2 protein levels and number of beta-cells in the stress groups declined compared to C group (p < 0.001 to p < 0.05). Intra-abdominal fat weight decreased in the PPS, PS, and LS groups compared to C group (p < 0.001 to p < 0.01), but adrenal gland weight remained unchanged.

CONCLUSION

Our results showed that long-term exposure to elevated levels of corticosterone during critical development induces metabolic syndrome in adult male rats.

Transforming growth factor-β receptor 1: An intervention target for genetic poor cartilage quality induced by prenatal dexamethasone exposure

INTRODUCTION

Fetal-originated osteoarthritis is relative to poor cartilage quality and may exhibit transgenerational genetic effects. Previous findings revealed prenatal dexamethasone exposure (PDE) induced poor cartilage quality in offspring.

OBJECTIVES

This study focused on further exploring molecular mechanism, heritability, and early intervention of fetal-originated osteoarthritis.

METHODS

Pregnant rats (F0) were segregated into control and PDE groups depending upon whether dexamethasone was administered on gestational days (GDs) 9-20. Some female offspring were bred with healthy males during postnatal week (PW) 8 to attain the F2 and F3 generations. The F3-generation rats were administrated with glucosamine intragastrically at PW12 for 6 weeks. The knee cartilages of male and female rats at different time points were harvested to assay their morphologies and functions. Furthermore, primary chondrocytes from the F3-generation rats were isolated to confirm the mechanism and intervention target of glucosamine.

RESULTS

Compared with the control, female and male rats in each generation of PDE group showed thinner cartilage thicknesses; shallower and uneven staining; fewer chondrocytes; higher Osteoarthritis Research Society International scores; and lower mRNA and protein expression of SP1, TGFβR1, Smad2, SOX9, ACAN and COL2A1. After F3-generation rats were treated with glucosamine, all of the above changes could be reversed. In primary chondrocytes isolated from the F3-generation rats of PDE group, glucosamine promoted SP1 expression and binding to TGFβR1 promoter to increase the expression of TGFβR1, p-Smad2, SOX9, ACAN and COL2A1, but these were prevented by SB431542 (a potent and selective inhibitor of TGFβR1).

CONCLUSIONS

PDE induced chondrodysplasia in offspring and stably inherited in F3-generation rats, which was related to decreased expression of SP1/TGFβR1/Smad2/SOX9 pathway to reduce the cartilage matrix synthesis, without major sex-based variations. Glucosamine could alleviate the poor genetic cartilage quality in offspring induced by PDE by up-regulating SP1/TGFβR1 signaling, which was prevented by a TGFβR1 inhibitor. This study elucidated the molecular mechanism and therapeutic target (TGFβR1) of genetic chondrodysplasia caused by PDE, which provides a research basis for precisely treating fetal-originated osteoarthritis.

Catch-up growth in juvenile rats, fat expansion, and dysregulation of visceral adipose tissue

BACKGROUND

Accelerated catch-up growth following intrauterine restriction increases the risk of developing visceral adiposity and metabolic abnormalities. However, the underlying molecular mechanisms of such metabolic programming are still poorly understood.

METHODS

A Wistar rat model of catch-up growth following intrauterine restriction was used. A gene expression array was performed in the retroperitoneal adipose tissue sampled at postnatal day (PD) 42.

RESULTS

Five hundred and forty-six differentially expressed genes (DEGs) were identified (adjusted p value < 0.05). Gene ontology enrichment analysis identified pathways related to immune and lipid metabolic processes, brown fat cell differentiation, and regulation of PI3K. Ccl21, Npr3, Serpina3n, Pnpla3, Slc2a4, and Serpina12 were validated to be upregulated in catch-up pups (all p < 0.01) and related to several fat expansion and metabolic parameters, including body weight at PD42, postnatal body weight gain, white and brown adipose tissue mass, plasma triglycerides, and insulin resistance index (all p < 0.05).

CONCLUSIONS

Genes related to immune and metabolic processes were upregulated in retroperitoneal adipose tissue following catch-up growth in juvenile rats and were found to be associated with fat expansion and metabolic parameters. Our results provide evidence for several dysregulated genes in white adipose tissue that could help develop novel strategies to prevent the metabolic abnormalities associated with catch-up growth.

IMPACT

Catch-up growth presents several dysregulated genes in white adipose tissue related to metabolic abnormalities. Ccl21, Npr3, Serpina3n, Pnpla3, Slc2a4, and Serpina12 were validated to be upregulated in catch-up pups and related to visceral fat expansion and metabolic parameters. Profiling and validation of these dysregulated genes in visceral adipose tissue could help develop novel strategies to prevent the metabolic abnormalities associated with catch-up growth.

Sex-specific changes in peripheral metabolism in a model of chronic anxiety induced by prenatal stress

BACKGROUND

Prenatal stress is associated with increased susceptibility to psychiatric and metabolic disorders later in life. Prenatal exposure to stress mediators may have sex-dependent effects on offspring brain and metabolic function, promoting a sex-specific vulnerability to psychopathology and metabolic alterations at adulthood. In this work, the impact of prenatal stress on glucose homeostasis and peripheral metabolism of male and female offspring was investigated in a chronic anxiety animal model.

METHODS

Pregnant Wistar rats were injected with saline or glucocorticoid (dexamethasone: 1 mg/kg, subcutaneous) at gestational days 18 and 19. Male and female offspring weight was monitored, and anxious-like behaviour and peripheral insulin-sensitive tissues were analysed at adulthood.

RESULTS

At birth, females and males prenatally exposed to stress presented decreased body weight which remained low in females. At adulthood, a morphological disorganization of the Langerhans islets was observed in both sexes prenatally exposed to stress, yet not changes in insulin levels were detected. Also, prenatal stress increased glucose transporter 4 (GLUT-4) levels in female and male adipose tissues and decreased insulin receptor levels in the liver and skeleton muscle but only in females.

CONCLUSIONS

Exposure to stress mediators in critical periods of development negatively affects behaviour and metabolism. Prenatal stress programmes offspring peripheral metabolism in a sex-specific manner, emphasizing that the response to stress in critical periods of development may be sex-specific having each sex different vulnerabilities to psychiatric and metabolic disorders. Considering sex-specificities may provide critical clues for the design of preventive strategies and for early therapeutic intervention.

The laboratory rat: Age and body weight matter

Animal experimentation helps us to understand human biology. Rodents and, in particular, rats are among the most common animals used in animal experiments. Reporting data on animal age, animal body weight, and animal postnatal developmental stages is not consistent, which can cause the failure to translate animal data to humans. This review summarizes age-related postnatal developmental stages in rats by addressing age-related changes in their body weights. The age and body weight of animals can affect drug metabolism, gene expression, metabolic parameters, and other dependent variables measured in animal studies. In addition, considering the age and the body weight of the animals is of particular importance in animal modeling of human diseases. Appropriate reporting of age, body weight, and the developmental stage of animals used in studies can improve animal to human translation.

Dexamethasone-induced intrauterine growth restriction modulates expression of placental vascular growth factors and fetal and placental growth

Prenatal exposure to glucocorticoids (GC) is a central topic of interest in medicine since GCs are essential for the maturation of fetal organs and intrauterine growth. Synthetic glucocorticoids, which are used in obstetric practice, exert beneficial effects on the fetus, but have also been reported to lead to intrauterine growth retardation (IUGR). In this study, a model of growth restriction in mice was established through maternal administration of dexamethasone during late gestation. We hypothesised that GC overexposure may adversely affect placental angiogenesis and fetal and placental growth. Female BALB/c mice were randomly assigned to control or dexamethasone treatment, either left to give birth or euthanised on days 15, 16, 17 and 18 of gestation followed by collection of maternal and fetal tissue. The IUGR rate increased to 100% in the dexamethasone group (8 mg/kg body weight on gestational days 14 and 15) and pups had clinical features of symmetrical IUGR at birth. Dexamethasone administration significantly decreased maternal body weight gain and serum corticosterone levels. Moreover, prenatal dexamethasone treatment not only induced fetal growth retardation but also decreased placental weight. In IUGR placentas, VEGFA protein levels and mRNA expression of VEGF receptors were reduced and NOS activity was lower. Maternal dexamethasone administration also reduced placental expression of the GC receptor, αGR. We demonstrated that maternal dexamethasone administration causes fetal and placental growth restriction. Furthermore, we propose that the growth retardation induced by prenatal GC overexposure may be caused, at least partially, by an altered placental angiogenic profile.

Maternal Protein Restriction Increases Autophagy in the Pancreas of Newborn Rats

A maternal low-protein diet increases the susceptibility of offspring to type 2 diabetes by inducing alterations in β cell mass and function. However, the mechanism of this pancreas injury remains poorly understood. The present study aimed to assess whether autophagy is altered in the pancreas of intrauterine growth restriction (IUGR). In addition, the autophagy associated mammalian target of rapamycin complex 1 (mTORC1) signaling and endoplasmic reticulum (ER) stress were further evaluated in the pancreas. The maternal protein restriction IUGR rat model was established as the IUGR group, and assessed alongside normal newborn rats (CON group). Then, the levels of autophagy markers were assessed by transmission electron microscopy, immunofluorescence, quantitative real-time PCR (qRT-PCR) and Western blot, respectively. In addition, mTORC1 signaling effectors were evaluated by Western blot; ER stress was quantitated by immunohistochemistry, qRT-PCR and Western blotting. Compared with the control group, the IUGR group showed increased levels of the autophagy markers LC3II and Beclin1, with decreased mTORC1 signaling activity. In addition, ER stress was confirmed in β cells of the IUGR group. These findings provided evidence that maternal protein restriction enhances autophagy in newborn pancreas, where ER stress was also induced in β cells, which might effect the pancreas development.

Panel of suitable reference genes and its gender differences of fetal rat liver under physiological conditions and exposure to dexamethasone during pregnancy

The panel of suitable reference genes in the fetal liver have not been reported. In this study, five commonly used reference genes (GAPDH, β-actin, Rn18 s, Rpl13a, and Rps29) were firstly selected as candidates. Bestkeeper, GeNorm, and NormFinder software were then used to screen out the panel of suitable reference genes of male and female fetal rat liver under physiological and prenatal dexamethasone exposure (PDE) conditions. Finally, we verified the reliability of the screened panel of reference genes by standardizing sterol regulatory element binding protein 1c (SREBP1c) expression with different reference genes. The results showed that GAPDH + Rn18 s and GAPDH + Rpl13a were respectively the panel of suitable reference genes in male and female rat fetal liver under the physiological model, while Rn18 s + Rps29 and GAPDH + Rn18 s were respectively under the PDE model. The results showed that different reference genes affected the statistical results of SREBP1c expression, and the screened panel of suitable reference genes under the PDE model had smaller intragroup differences, when compared with other reference genes under physiological and PDE models. In conclusion, we screened and determined that the panel of suitable reference genes were GAPDH + Rn18 s and Rn18 s + Rps29 in the male rat fetal liver under physiological and PDE models, while they were GAPDH + Rpl13a and GAPDH + Rn18 s in the females, and confirmed that the selection of the panel of suitable reference genes in the fetal liver had gender differences and pathological model specificity.

Molecular mechanisms governing offspring metabolic programming in rodent models of in utero stress

The results of different human epidemiological datasets provided the impetus to introduce the now commonly accepted theory coined as 'developmental programming', whereby the presence of a stressor during gestation predisposes the growing fetus to develop diseases, such as metabolic dysfunction in later postnatal life. However, in a clinical setting, human lifespan and inaccessibility to tissue for analysis are major limitations to study the molecular mechanisms governing developmental programming. Subsequently, studies using animal models have proved indispensable to the identification of key molecular pathways and epigenetic mechanisms that are dysregulated in metabolic organs of the fetus and adult programmed due to an adverse gestational environment. Rodents such as mice and rats are the most used experimental animals in the study of developmental programming. This review summarises the molecular pathways and epigenetic mechanisms influencing alterations in metabolic tissues of rodent offspring exposed to in utero stress and subsequently programmed for metabolic dysfunction. By comparing molecular mechanisms in a variety of rodent models of in utero stress, we hope to summarise common themes and pathways governing later metabolic dysfunction in the offspring whilst identifying reasons for incongruencies between models so to inform future work. With the continued use and refinement of such models of developmental programming, the scientific community may gain the knowledge required for the targeted treatment of metabolic diseases that have intrauterine origins.

Fetal growth restriction mice are more likely to exhibit depression-like behaviors due to stress-induced loss of dopaminergic neurons in the VTA

Fetal growth restriction (FGR) is a severe perinatal complication that can increase risk for mental illness. To investigate the mechanism by which FGR mice develop mental illness in adulthood, we established the FGR mouse model and the FGR mice did not display obvious depression-like behaviors, but after environmental stress exposure, FGR mice were more likely to exhibit depression-like behaviors than control mice. Moreover, FGR mice had significantly fewer dopaminergic neurons in the ventral tegmental area but no difference in serotoninergic neurons in the dorsal raphe. RNA-seq analysis showed that the downregulated genes in the midbrain of FGR mice were associated with many mental diseases and were especially involved in the regulation of NMDA-selective glutamate receptor (NMDAR) activity. Furthermore, the NMDAR antagonist memantine can relieve the stress-induced depression-like behaviors of FGR mice. In summary, our findings provide a theoretical basis for future research and treatment of FGR-related depression.

Stress, Sex, and Sugar: Glucocorticoids and Sex-Steroid Crosstalk in the Sex-Specific Misprogramming of Metabolism

Early-life exposures to environmental insults can misprogram development and increase metabolic disease risk in a sex-dependent manner by mechanisms that remain poorly characterized. Modifiable factors of increasing public health relevance, such as diet, psychological stress, and endocrine-disrupting chemicals, can affect glucocorticoid receptor signaling during gestation and lead to sex-specific postnatal metabolic derangements. Evidence from humans and animal studies indicate that glucocorticoids crosstalk with sex steroids by several mechanisms in multiple tissues and can affect sex-steroid-dependent developmental processes. Nonetheless, glucocorticoid sex-steroid crosstalk has not been considered in the glucocorticoid-induced misprogramming of metabolism. Herein we review what is known about the mechanisms by which glucocorticoids crosstalk with estrogen, androgen, and progestogen action. We propose that glucocorticoid sex-steroid crosstalk is an understudied mechanism of action that requires consideration when examining the developmental misprogramming of metabolism, especially when assessing sex-specific outcomes.

Cholinergic-pathway-weakness-associated pancreatic islet dysfunction: a low-protein-diet imprint effect on weaned rat offspring

Currently, metabolic disorders are one of the major health problems worldwide, which have been shown to be related to perinatal nutritional insults, and the autonomic nervous system and endocrine pancreas are pivotal targets of the malprogramming of metabolic function. We aimed to assess glucose–insulin homeostasis and the involvement of cholinergic responsiveness (vagus nerve activity and insulinotropic muscarinic response) in pancreatic islet capacity to secrete insulin in weaned rat offspring whose mothers were undernourished in the first 2 weeks of the suckling phase. At delivery, dams were fed a low-protein (4% protein, LP group) or a normal-protein diet (20.5% protein, NP group) during the first 2 weeks of the suckling period. Litter size was adjusted to six pups per mother, and rats were weaned at 21 days old. Weaned LP rats presented a lean phenotype (P < 0.01); hypoglycaemia, hypoinsulinaemia and hypoleptinaemia (P < 0.05); and normal corticosteronaemia (P > 0.05). In addition, milk insulin levels in mothers of the LP rats were twofold higher than those of mothers of the NP rats (P < 0.001). Regarding glucose–insulin homeostasis, weaned LP rats were glucose-intolerant (P < 0.01) and displayed impaired pancreatic islet insulinotropic function (P < 0.05). The M3 subtype of the muscarinic acetylcholine receptor (M3mAChR) from weaned LP rats was less responsive, and the superior vagus nerve electrical activity was reduced by 30% (P < 0.01). A low-protein diet in the suckling period malprogrammes the vagus nerve to low tonus and impairs muscarinic response in the pancreatic β-cells of weaned rats, which are imprinted to secrete inadequate insulin amounts from an early age.

Perinatal programming of metabolic diseases: The role of glucocorticoids

The worldwide increase in metabolic diseases has urged the scientific community to improve our understanding about the mechanisms underlying its cause and effects. A well supported area of studies had related maternal stress with early programming to the later metabolic diseases. Mechanisms upon origins of metabolic disturbances are not yet fully understood, even though stressful factors rising glucocorticoids have been put out as pivotal trigger by programming metabolic diseases as long-term consequence. Considering energy balance and glucose homeostasis, by producing and/or sensing regulator signals, hypothalamus-pituitary-adrenal axis and endocrine pancreas are directly affected by glucocorticoids excess. We focus on the evidences reporting the role of increased glucocorticoids due to perinatal insults on the physiological systems involved in the metabolic homeostasis and in the target organs such as endocrine pancreas, white adipose tissue and blood vessels. Besides, we review some mechanisms underlining the malprogramming of type 2 diabetes, obesity and hypertension. Studies on this field are currently ongoing and even there is a good understanding regarding the effects of glucocorticoids addressing metabolic diseases, few is known about the relationship between maternal insults rising glucocorticoids to pups' metabolic disturbances, a thorough understanding about that may provide pivotal clinical clues regarding those disorders.

Dlk1 expression relates to visceral fat expansion and insulin resistance in male and female rats with postnatal catch-up growth

BACKGROUND

Although prenatal and postnatal programming of metabolic diseases in adulthood is well established, the mechanisms underpinning metabolic programming are not. Dlk1, a key regulator of fetal development, inhibits adipocyte differentiation and restricts fetal growth.

METHODS

Assess DLk1 expression in a Wistar rat model of catch-up growth following intrauterine restriction. Dams fed ad libitum delivered control pups (C) and dams on a 50% calorie-restricted diet delivered pups with low birth weight (R). Restricted offspring fed a standard rat chow showed catch-up growth (R/C) but those kept on a calorie-restricted diet did not (R/R).

RESULTS

Decreased Dlk1 expression was observed in adipose tissue and skeletal muscle of R/C pups along with excessive visceral fat accumulation, decreased circulating adiponectin, increased triglycerides and HOMA-IR (from p < 0.05 to p < 0.0001). Moreover, in R/C pups the reduced Dlk1 expression in adipose tissue and skeletal muscle correlated with visceral fat (r = -0.820, p < 00001) and HOMA-IR (r = -0.745, p = 0.002).

CONCLUSIONS

Decreased Dlk1 expression relates to visceral fat expansion and insulin resistance in a rat model of catch-up growth following prenatal growth restriction. Modulation of Dlk1 expression could be among the targets for the early prevention of fetal programming of adult metabolic disorders.

Developmental exposure to the endocrine disruptor tolylfluanid induces sex-specific later-life metabolic dysfunction

Endocrine-disrupting chemicals (EDCs) are implicated in the developmental mis-programming of energy metabolism. This study examined the impact of combined gestational and lactational exposure to the fungicide tolylfluanid (TF) on metabolic physiology in adult offspring. C57BL/6 J dams received standard rodent chow or the same diet containing 67 mg/kg TF. Offspring growth and metabolism were assessed up to 22 weeks of age. TF-exposed offspring exhibited reduced weaning weight. Body weight among female offspring remained low throughout the study, while male offspring matched controls by 17 weeks of age. Female offspring exhibited reduced glucose tolerance, markedly enhanced systemic insulin sensitivity, reduced adiposity, and normal gluconeogenic capacity during adulthood. In contrast, male offspring exhibited impaired glucose tolerance with unchanged insulin sensitivity, no differences in adiposity, and increased gluconeogenic capacity. These data indicate that developmental exposure to TF induces sex-specific metabolic disruptions that recapitulate key aspects of other in utero growth restriction models.

Course-, dose-, and stage-dependent toxic effects of prenatal dexamethasone exposure on long bone development in fetal mice

Dexamethasone is routinely used for treating those mothers at risk for preterm delivery. However, overexposure to exogenous glucocorticoids induces bone loss in offspring, and the "critical window" and safe dose of this treatment are largely unknown. In this study, we found that femoral length, and the length of the primary ossification center were significantly reduced in fetal mice after repeated prenatal dexamethasone exposure (PDE). Compared with single-course exposure on gestational day (GD)15, newborn mice with repeated PDE (3 times, from GD15 to 17) showed a significant decrease in femoral trabecular bone mass with decreased trabecular number and thickness. For those newborn mice treated after repeated PDE at different doses (0, 0.2, 0.8, and 1.2 mg/kg/d), the toxic effect of dexamethasone on bone development was observed at 0.8 and 1.2 mg/kg/d. More severe retardation in bone development was observed in the fetal mice after PDE at 0.8 mg/kg/d during GD12-14, compared with that during GD15-17. Interestingly, stronger toxic effects were observed in male newborn mice after PDE than were observed in female newborn mice. In conclusion, PDE with multiple course, higher dose, or exposure at an early stage of pregnancy have stronger toxic effects on bone development of fetal mice.

Precocious glucocorticoid exposure reduces skeletal muscle satellite cells in the fetal rat

Perinatal skeletal muscle growth rates are a function of protein and myonuclear accretion. Precocious exposure of the fetus to glucocorticoids (GLC) in utero impairs muscle growth. Reduced muscle protein synthesis rates contribute to this response, but the consequences for myonuclear hyperplasia are unknown. To test the hypothesis that blunting of Pax7+ muscle progenitor cell proliferative activity by GLC in vivo also contributes to reduced fetal muscle growth, pregnant rats were administered dexamethasone (DEX: 1 mg/L drinking water) from embryonic day (ED) 13 to ED21. Their responses were compared to pair-fed (PF) and ad libitum-fed controls (CON). Bromodeoxyuridine (BrdU) was administered before delivery to measure myonuclear accretion. Fetal hind limb and diaphragm muscles were collected at term and analyzed for myofiber cross-sectional area (CSA), total and BrdU+ myonuclei, Pax7+ nuclei, MyoD and myogenin protein and mRNA abundance and myosin heavy chain (MyHC) isoform composition. Mean fiber CSA, myonuclei/myofiber and Pax7+ nuclei/myofiber ratios were reduced in DEX compared to those in CON and PF muscles; CSA/myonucleus, BrdU+/total myonuclei and BrdU+ myonuclei/Pax7+ nuclei were similar among groups. Myogenin abundance was reduced and MyHC-slow was increased in DEX fetuses. The data are consistent with GLC inhibition of muscle progenitor cell proliferation limiting satellite cell and myonuclear accretion. The response of PF-fed compared to CON muscles indicated that decreased food consumption by DEX dams contributed to the smaller myofiber CSA but did not affect Pax7+ nuclear accretion. Thus, the effect on satellite cell reserve and myonuclear number also contributes to the blunting of fetal muscle growth by GLC.

Maternal treatment with dexamethasone during gestation alters sexual development markers in the F1 and F2 male offspring of Wistar rats

Maternal treatment with dexamethasone (Dex) in threatening preterm delivery alters activities at the hypothalamic–pituitary–adrenal axis in the offspring. This alteration may interfere with reproductive function. The impact of gestational Dex exposure on male reproductive function of the offspring was investigated. A total of 25 pregnant rats randomly assigned to five groups (n=5) were treated with normal saline (control), Dex (100 μg/kg/day sc) during gestation days (GD) 1–7, 8–14, 15–21 and 1–21, respectively. Birth weight, anogenital distance (AGD), pubertal age, sperm parameters, hormonal profile and histopathology of testis and epididymis were determined in the F1 and F2 offspring. Results showed a significant increase (P<0.05) in pubertal age, serum corticosterone and gonadotropin-releasing hormone (GnRH) levels in the male offspring of DexGD 15–21 and 1–21 groups and a significant decrease (P<0.05) in serum testosterone, luteinizing hormone, birth weight and AGD at birth in the male F1 offspring. In the F2 offspring, there was a significant reduction (P<0.05) in serum corticosterone, testosterone, follicle-stimulating hormone and GnRH when compared with the control. Dex treatment at GD 15–21 and 1–21 significantly reduced (P<0.05) sperm motility and normal morphology in the F1 and F2 offspring. Maternal Dex treatment in rats during late gestation may disrupt sexual development markers in the F1 and F2 male offspring.

The consequences of fetal growth restriction on brain structure and neurodevelopmental outcome

Fetal growth restriction (FGR) is a significant complication of pregnancy describing a fetus that does not grow to full potential due to pathological compromise. FGR affects 3-9% of pregnancies in high-income countries, and is a leading cause of perinatal mortality and morbidity. Placental insufficiency is the principal cause of FGR, resulting in chronic fetal hypoxia. This hypoxia induces a fetal adaptive response of cardiac output redistribution to favour vital organs, including the brain, and is in consequence called brain sparing. Despite this, it is now apparent that brain sparing does not ensure normal brain development in growth-restricted fetuses. In this review we have brought together available evidence from human and experimental animal studies to describe the complex changes in brain structure and function that occur as a consequence of FGR. In both humans and animals, neurodevelopmental outcomes are influenced by the timing of the onset of FGR, the severity of FGR, and gestational age at delivery. FGR is broadly associated with reduced total brain volume and altered cortical volume and structure, decreased total number of cells and myelination deficits. Brain connectivity is also impaired, evidenced by neuronal migration deficits, reduced dendritic processes, and less efficient networks with decreased long-range connections. Subsequent to these structural alterations, short- and long-term functional consequences have been described in school children who had FGR, most commonly including problems in motor skills, cognition, memory and neuropsychological dysfunctions.

Glucocorticoids as regulatory signals during intrauterine development

NEW FINDINGS

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

Differential Effects of Intrauterine Growth Restriction on the Regional Neurochemical Profile of the Developing Rat Brain

Intrauterine growth restricted (IUGR) infants are at increased risk for neurodevelopmental deficits that suggest the hippocampus and cerebral cortex may be particularly vulnerable. Evaluate regional neurochemical profiles in IUGR and normally grown (NG) 7-day old rat pups using in vivo ¹H magnetic resonance (MR) spectroscopy at 9.4 T. IUGR was induced via bilateral uterine artery ligation at gestational day 19 in pregnant Sprague-Dawley dams. MR spectra were obtained from the cerebral cortex, hippocampus and striatum at P7 in IUGR (N = 12) and NG (N = 13) rats. In the cortex, IUGR resulted in lower concentrations of phosphocreatine, glutathione, taurine, total choline, total creatine (P < 0.01) and [glutamate]/[glutamine] ratio (P < 0.05). Lower taurine concentrations were observed in the hippocampus (P < 0.01) and striatum (P < 0.05). IUGR differentially affects the neurochemical profile of the P7 rat brain regions. Persistent neurochemical changes may lead to cortex-based long-term neurodevelopmental deficits in human IUGR infants.

Protective effects of maternal nutritional supplementation with lactoferrin on growth and brain metabolism

BACKGROUND

Intrauterine growth restriction (IUGR) is a major risk factor for both perinatal and long-term morbidity. Bovine lactoferrin (bLf) is a major milk glycoprotein considered as a pleiotropic functional nutrient. The impact of maternal supplementation with bLf on IUGR-induced sequelae, including inadequate growth and altered cerebral development, remains unknown.

METHODS

IUGR was induced through maternal dexamethasone infusion (100 μg/kg during last gestational week) in rats. Maternal supplementation with bLf (0.85% in food pellet) was provided during both gestation and lactation. Pup growth was monitored, and Pup brain metabolism and gene expression were studied using in vivo (1)H NMR spectroscopy, quantitative PCR, and microarray in the hippocampus at postnatal day (PND)7.

RESULTS

Maternal bLf supplementation did not change gestational weight but increased the birth body weight of control pups (4%) with no effect on the IUGR pups. Maternal bLf supplementation allowed IUGR pups to recover a normalized weight at PND21 (weaning) improving catch-up growth. Significantly altered levels of brain metabolites (γ-aminobutyric acid, glutamate, N-acetylaspartate, and N-acetylaspartylglutamate) and transcripts (brain-derived neurotrophic factor (BDNF), divalent metal transporter 1 (DMT-1), and glutamate receptors) in IUGR pups were normalized with maternal bLf supplementation.

CONCLUSION

Our data suggest that maternal bLf supplementation is a beneficial nutritional intervention able to revert some of the IUGR-induced sequelae, including brain hippocampal changes.

Nutritional manipulations in the perinatal period program adipose tissue in offspring

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

Prenatal food restriction induces a hypothalamic-pituitary-adrenocortical axis-associated neuroendocrine metabolic programmed alteration in adult offspring rats

BACKGROUND AND AIMS

Intrauterine growth restriction produces susceptibility to adult metabolic syndrome, which may be caused by the permanent alteration of the hypothalamic-pituitary-adrenocortical (HPA) axis. We aimed to verify that HPA axis-associated neuroendocrine metabolic programming is altered in food-restricted (FR) offspring.

METHODS

Maternal rats were fed a restricted diet from gestational day 11 until full-term delivery, all pups were fed a high-fat diet after weaning and exposed to unpredictable chronic stress (UCS) during postnatal weeks 17-20.

RESULTS

Serum levels of adrenocorticotrophic hormone and corticosterone in adult offspring of the prenatal FR group were lower than the control (CN) rats before UCS but increased significantly after UCS. Serum glucose levels in the FR group were normal before UCS but increased after UCS. Serum insulin levels were significantly decreased in FR males but showed a slight increase in FR females before UCS; however, insulin levels decreased significantly in the FR male and female rats after UCS. Before UCS, serum lipid levels were higher in the FR males but were normal in the FR females; after UCS, FR males had a slight decrease and FR females had an increasing trend in serum lipids levels. Lipid droplets in the hypothalamus, pituitary gland, and livers of the FR group indicated steatosis.

CONCLUSIONS

These results suggest that prenatal food restriction alters HPA axis-associated neuroendocrine metabolism in adult offspring fed a high-fat diet, which may originate from the intrauterine programming and increase the susceptibility to adult metabolic diseases.