Hypothalamic substrates of metabolic imprinting

Microglia are Required for Developmental Specification of AgRP Innervation in the Hypothalamus of Offspring Exposed to Maternal High Fat Diet During Lactation

Nutritional fluctuations that occur early in life dictate metabolic adaptations that will affect susceptibility to weight gain and obesity later in life. The postnatal period in mice represents a time of dynamic changes in hypothalamic development and maternal consumption of a high fat diet during the lactation period (MHFD) changes the composition of milk and leads to enhanced susceptibility to obesity in offspring. Agouti-related peptide (AgRP) neurons in the arcuate nucleus of the hypothalamus (ARH) react to changes in multiple metabolic signals and distribute neuroendocrine information to other brain regions, such as the paraventricular hypothalamic nucleus (PVH), which is known to integrate a variety of signals that regulate body weight. Development of neural projections from AgRP neurons to the PVH occurs during the lactation period and these projections are reduced in MHFD offspring, but underlying developmental mechanisms remain largely unknown. Microglia are the resident immune cells of the central nervous system and are involved in refinement of neural connections and modulation of synaptic transmission. Because high fat diet exposure causes activation of microglia in adults, a similar activation may occur in offspring exposed to MHFD and play a role in sculpting hypothalamic feeding circuitry. Genetically targeted axonal labeling and immunohistochemistry were used to visualize AgRP axons and microglia in postnatal mice derived from MHFD dams and morphological changes quantified. The results demonstrate regionally localized changes to microglial morphology in the PVH of MHFD offspring that suggest enhanced surveillance activity and are temporally restricted to the period when AgRP neurons innervate the PVH. In addition, axon labeling experiments confirm a significant decrease in AgRP innervation of the PVH in MHFD offspring and provide direct evidence of synaptic pruning of AgRP inputs to the PVH. Microglial depletion with the Colony-stimulating factor 1 receptor inhibitor PLX5622 determined that the decrease in AgRP innervation observed in MHFD offspring is dependent on microglia, and that microglia are required for weight gain that emerges as early as weaning in offspring of MHFD dams. However, these changes do not appear to be dependent on the degree of microglial mediated synaptic pruning. Together, these findings suggest that microglia are activated by exposure to MHFD and interact directly with AgRP axons during development to permanently alter their density, with implications for developmental programming of metabolic phenotype.

Repetitive transcranial direct current stimulation modulates the brain-gut-microbiome axis in obese rodents

Background

Complex interactions between the brain, gut and adipose tissue allow to recognize obesity as a neurometabolic disorder. The recent data have shown that gut microbiota can play a potential role in obesity development. Transcranial direct current stimulation (tDCS) is a safe and non-invasive technique to modulate the activity of cerebral cortex and other connected brain areas also in context of appetite control. The objective of this study was to evaluate the effects of repetitive anodal tDCS (AtDCS) of prefrontal cortex on feeding behavior, metabolic status and selected phyla of gut microbiota in rats with obesity induced by high-calorie diet (HCD).

Methods

32 female Wistar rats were equally divided into 4 subgroups depending on diet effect (lean versus obese) and type of stimulation (active versus sham tDCS versus no stimulation). Feed intake, body weight, blood lipoproteins and leptin levels as well as Firmicutes and Bacteroidetes in intestines and stool were examined.

Results

HCD changed feeding behavior and metabolic parameters typically for obesity-related ranges and resulted in an abundance of Firmicutes at the expanse of Bacteroidetes in the large intestine and stool. AtDCS decreased appetite, body weight, and cholesterol levels. In addition, AtDCS reduced ratio of the average number of Firmicutes to average number of Bacteroidetes in all examined tissues.

Conclusions

Repetitive AtDCS is not only effective for appetite restriction but can also modulate gut microbiome composition which demonstrates the existence of the brain–gut–microbiome axis and points at this technique as a promising complementary treatment for obesity. However, the effects should be further replicated in human studies.

Leptin coordinates efferent sympathetic outflow to the white adipose tissue through the midbrain centrally-projecting Edinger-Westphal nucleus in male rats

The centrally-projecting Edinger-Westphal nucleus (EWcp) hosts a large population of neurons expressing urocortin 1 (Ucn1) and about half of these neurons also express the leptin receptor (LepRb). Previously, we have shown that the peripheral adiposity hormone leptin signaling energy surfeit modulates EWcp neurons' activity. Here, we hypothesized that Ucn1/LepRb neurons in the EWcp would act as a crucial neuronal node in the brain-white adipose tissue (WAT) axis modulating efferent sympathetic outflow to the WAT. We showed that leptin bound to neurons of the EWcp stimulated STAT3 phosphorylation, and increased Ucn1-production in a time-dependent manner. Besides, retrograde transneuronal tract-tracing using pseudorabies virus (PRV) identified EWcp Ucn1 neurons connected to WAT. Interestingly, reducing EWcp Ucn1 contents by ablating EWcp LepRb-positive neurons with leptin-saporin, did not affect food intake and body weight gain, but substantially (+26%) increased WAT weight accompanied by a higher plasma leptin level and changed plasma lipid profile. We also found that ablation of EWcp Ucn1/LepRb neurons resulted in lower respiratory quotient and oxygen consumption one week after surgery, but was comparable to sham values after 3 and 5 weeks of surgery. Taken together, we report that EWcp/LepRb/Ucn1 neurons not only respond to leptin signaling but also control WAT size and fat metabolism without altering food intake. These data suggest the existence of a EWcp-WAT circuitry allowing an organism to recruit fuels without being able to eat in situations such as the fight-or-flight response.

Relationship of prenatal maternal obesity and diabetes to offspring neurodevelopmental and psychiatric disorders: a narrative review

Obesity and diabetes is a worldwide public health problem among women of reproductive age. This narrative review highlights recent epidemiological studies regarding associations of maternal obesity and diabetes with neurodevelopmental and psychiatric disorders in offspring, and provides an overview of plausible underlying mechanisms and challenges for future human studies. A comprehensive search strategy selected terms that corresponded to the domains of interest (maternal obesity, different types of diabetes, offspring cognitive functions and neuropsychiatric disorders). The databases searched for articles published between January 2010 and April 2019 were PubMed, Web of Science and CINAHL. Evidence from epidemiological studies strongly suggests that maternal pre-pregnancy obesity is associated with increased risks for autism spectrum disorder, attention-deficit hyperactivity disorder and cognitive dysfunction with modest effect sizes, and that maternal diabetes is associated with the risk of the former two disorders. The influence of maternal obesity on other psychiatric disorders is less well studied, but there are reports of associations with increased risks for offspring depression, anxiety, schizophrenia and eating disorders, at modest effect sizes. It remains unclear whether these associations are due to intrauterine mechanisms or explained by confounding family-based sociodemographic, lifestyle and genetic factors. The plausible underlying mechanisms have been explored primarily in animal models, and are yet to be further investigated in human studies.

The Complex Interactions Between Obesity, Metabolism and the Brain

Obesity is increasing at unprecedented levels globally, and the overall impact of obesity on the various organ systems of the body is only beginning to be fully appreciated. Because of the myriad of direct and indirect effects of obesity causing dysfunction of multiple tissues and organs, it is likely that there will be heterogeneity in the presentation of obesity effects in any given population. Taken together, these realities make it increasingly difficult to understand the complex interplay between obesity effects on different organs, including the brain. The focus of this review is to provide a comprehensive view of metabolic disturbances present in obesity, their direct and indirect effects on the different organ systems of the body, and to discuss the interaction of these effects in the context of brain aging and the development of neurodegenerative diseases.

Maternal high-fat diet results in cognitive impairment and hippocampal gene expression changes in rat offspring

Consumption of a high-fat diet has long been known to increase risk for obesity, diabetes, and the metabolic syndrome. Further evidence strongly suggests that these same metabolic disorders are associated with an increased risk of cognitive impairment later in life. Now faced with an expanding global burden of obesity and increasing prevalence of dementia due to an aging population, understanding the effects of high-fat diet consumption on cognition is of increasingly critical importance. Further, the developmental origins of many adult onset neuropsychiatric disorders have become increasingly clear, indicating a need to investigate effects of various risk factors, including diet, across the lifespan. Here, we use a rat model to assess the effects of maternal diet during pregnancy and lactation on cognition and hippocampal gene expression of offspring. Behaviorally, adult male offspring of high-fat fed dams had impaired object recognition memory and impaired spatial memory compared to offspring of chow-fed dams. In hippocampus, we found decreased expression of Insr, Lepr, and Slc2a1 (GLUT1) among offspring of high-fat fed dams at postnatal day 21. The decreased expression of Insr and Lepr persisted at postnatal day 150. Together, these data provide additional evidence to suggest that maternal exposure to high-fat diet during pregnancy and lactation can have lasting effects on the brain, behavior, and cognition on adult offspring.

Oxidative Stress, Maternal Diabetes, and Autism Spectrum Disorders

Autism spectrum disorders (ASD) are a group of early-onset neurodevelopmental conditions characterized by alterations in brain connectivity with cascading effects on neuropsychological functions. To date, in the framework of an increasing interest about environmental conditions which could interact with genetic factors in ASD pathogenesis, many authors have stressed that changes in the intrauterine environment at different stages of pregnancy, such as those linked to maternal metabolic pathologies, may lead to long-term conditions in the newborn. In particular, a growing number of epidemiological studies have highlighted the role of obesity and maternal diabetes as a risk factor for developing both somatic and psychiatric disorders in humans, including ASD. While literature still fails in identifying specific etiopathological mechanisms, a growing body of evidence is available about the presence of a relationship between maternal immune dysregulation, inflammation, oxidative stress, and the development of ASD in the offspring. In this framework, results from high-fat diet animal models about the role played by oxidative stress in shaping offspring neurodevelopment may help in clarifying the pathways through which maternal metabolic conditions are linked with ASD. The aim of this review is to provide an overview of literature about the effects of early life insults linked to oxidative stress which may be involved in ASD etiopathogenesis and how this relationship can be explained in biological terms.

Maternal protein restriction during lactation modulated the expression and activity of rat offspring hepatic CYP1A1, CYP1A2, CYP2B1, CYP2B2, and CYP2E1 during development

Early nutrition plays a long-term role in the predisposition to chronic diseases and influences the metabolism of several drugs. This may happen through cytochromes P450 (CYPs) regulation, which are the main enzymes responsible for the metabolism of xenobiotics. Here, we analyzed the effects of maternal protein restriction (MPR) on the expression and activity of hepatic offspring’s CYPs during 90 days after birth, using Wistar rats as a mammal model. Hepatic CYP1A1, CYP1A2, CYP2B1, CYP2B2 and CYP2E1 mRNA and protein expression, and associated catalytic activities (ECOD, EROD, MROD, BROD, PROD and PNPH) were evaluated in 15-, 30-, 60-, and 90-day-old offspring from dams fed with either a 0% protein (MPR groups) or a standard diet (C groups) during the 10 first days of lactation. Results showed that most CYP genes were induced in 60- and 90-day-old MPR offspring. The inductions detected in MPR60 and MPR90 were of 5.0- and 2.0-fold (CYP1A2), 3.7- and 2.0-fold (CYP2B2) and 9.8- and 5.8– fold (CYP2E1), respectively, and a 3.8-fold increase of CYP2B1 in MPR90. No major alterations were detected in CYP protein expression. The most relevant CYP catalytic activities’ alterations were observed in EROD, BROD and PNPH. Nevertheless, they did not follow the same pattern observed for mRNA expression, except for an induction of EROD in MPR90 (3.5-fold) and of PNPH in MPR60 (2.2-fold). Together, these results suggest that MPR during lactation was capable of altering the expression and activity of the hepatic CYP enzymes evaluated in the offspring along development.

BPA, an energy balance disruptor

Bisphenol A (BPA) is used extensively in the world and is present in a diverse range of manufactured articles including dental resins, polycarbonate plastics, and the inner coating of food cans. It is a high volume chemical, with global production at 3.6 × 10(9) kg per year. BPA was identified as a high priority for assessment of human health risk because it was considered to present greatest potential for human exposure. Most studies of the health effects of BPA have focused on endocrine disruption leading to reproductive toxicity, but it displays additional side effects, including liver damage, disrupted pancreatic β-cell function, thyroid hormone disruption, and obesity-promoting effects. In this article, we reviewed specifically on the effects of BPA in energy balance.

Interaction between neonatal maternal deprivation and serum leptin levels on metabolism, pubertal development, and sexual behavior in male and female rats

BACKGROUND

Maternal deprivation (MD) during neonatal life can have long-term effects on metabolism and behavior, with males and females responding differently. We previously reported that MD during 24 h at postnatal day (PND) 9 blocks the physiological neonatal leptin surge in both sexes. It is known that modifications in neonatal leptin levels can affect metabolism in adulthood. Thus, we hypothesized that at least some of the long-term metabolic changes that occur in response to MD are due to the decline in serum leptin during this critical period of development. Hence, we predicted that treatment with leptin during MD would normalize these metabolic changes, with this response also differing between the sexes.

METHODS

MD was carried-out in Wistar rats for 24 h on PND9. Control and MD rats of both sexes were treated from PND 9 to 13 with leptin (3 mg/kg/day sc) or vehicle. Weight gain, food intake, glucose tolerance, and pubertal onset were monitored. Sexual behavior was analyzed in males. Rats were killed at PND90, and serum hormones and hypothalamic neuropeptides involved in metabolic control and reproduction were measured. Results were analyzed by three-way analysis of covariance using sex, MD, and leptin treatment as factors and litter as the covariate and employing repeated measures where appropriate.

RESULTS

In males, MD advanced the external signs of puberty and increased serum insulin and triglyceride levels and hypothalamic proopiomelanocortin mRNA levels at PND90. Neonatal leptin treatment normalized these effects. In contrast, MD decreased circulating triglycerides, as well as estradiol levels, in females at PND90 and these changes were also normalized by neonatal leptin treatment. Neonatal leptin treatment also had long-term effects in control rats as it advanced the external signs of puberty in control males, but delayed them in females. Neonatal leptin treatment increased serum insulin and hypothalamic mRNA levels of the leptin receptor and cocaine- and amphetamine-regulated transcript in control males and increased orexin mRNA levels in controls of both sexes. Although pubertal onset in males was advanced by either MD or neonatal leptin treatment in males and delayed by leptin treatment in females, the mRNA levels of hypothalamic neuropeptides and receptors related to reproduction were not affected by MD or neonatal leptin treatment in either sex at PND90.

CONCLUSIONS

These findings indicate that some of the long-term changes in metabolic and reproductive parameters induced by MD, such as advanced pubertal onset and increased hypothalamic proopiomelanocortin (POMC) expression, hyperinsulinemia, and hypertriglyceridemia in adult males and decreased serum triglyceride and estradiol levels in females, are most likely due to the decrease in leptin levels during the period of MD.

Maternal high-fat diet programming of the neuroendocrine system and behavior

This article is part of a Special Issue "SBN 2014". Maternal obesity, metabolic state, and diet during gestation have profound effects on offspring development. The prevalence of neurodevelopmental and mental health disorders has risen rapidly in the last several decades in parallel with the rise in obesity rates. Evidence from epidemiological studies indicates that maternal obesity and metabolic complications increase the risk of offspring developing behavioral disorders such as attention deficit hyperactivity disorder (ADHD), autism spectrum disorders (ASD), and schizophrenia. Animal models show that a maternal diet high in fat similarly disrupts behavioral programming of offspring, with animals showing social impairments, increased anxiety and depressive behaviors, reduced cognitive development, and hyperactivity. Maternal obesity, metabolic conditions, and high fat diet consumption increase maternal leptin, insulin, glucose, triglycerides, and inflammatory cytokines. This leads to increased risk of placental dysfunction, and altered fetal neuroendocrine development. Changes in brain development that likely contribute to the increased risk of behavioral and mental health disorders include increased inflammation in the brain, as well as alterations in the serotonergic system, dopaminergic system and hypothalamic-pituitary-adrenal (HPA) axis.

Developmental programming of energy balance regulation: is physical activity more ‘programmable’ than food intake?

Extensive human and animal model data show that environmental influences during critical periods of prenatal and early postnatal development can cause persistent alterations in energy balance regulation. Although a potentially important factor in the worldwide obesity epidemic, the fundamental mechanisms underlying such developmental programming of energy balance are poorly understood, limiting our ability to intervene. Most studies of developmental programming of energy balance have focused on persistent alterations in the regulation of energy intake; energy expenditure has been relatively underemphasised. In particular, very few studies have evaluated developmental programming of physical activity. The aim of this review is to summarise recent evidence that early environment may have a profound impact on establishment of individual propensity for physical activity. Recently, we characterised two different mouse models of developmental programming of obesity; one models fetal growth restriction followed by catch-up growth, and the other models early postnatal overnutrition. In both studies, we observed alterations in body-weight regulation that persisted to adulthood, but no group differences in food intake. Rather, in both cases, programming of energy balance appeared to be due to persistent alterations in energy expenditure and spontaneous physical activity (SPA). These effects were stronger in female offspring. We are currently exploring the hypothesis that developmental programming of SPA occurs via induced sex-specific alterations in epigenetic regulation in the hypothalamus and other regions of the central nervous system. We will summarise the current progress towards testing this hypothesis. Early environmental influences on establishment of physical activity are likely an important factor in developmental programming of energy balance. Understanding the fundamental underlying mechanisms in appropriate animal models will help determine whether early life interventions may be a practical approach to promote physical activity in man.

Developmental programming of hypothalamic neuroendocrine systems

There is increasing evidence to suggest that the perinatal environment may alter the developmental programming of hypothalamic neuroendocrine systems in a manner that predisposes offspring to the development of metabolic syndrome. Although it is unclear how these effects might be mediated, it has been shown that changes in neuroendocrine programing during critical periods of development, either via maternal metabolic programming or other factors, can alter a fetus's metabolic fate. This review summarizes the hypothalamic circuits that mediate energy homeostasis and discusses the various factors that may influence the development and functioning of these neural systems, as well as the possible cognitive impairments that may arise as a result of these metabolic influences.

Developmental specification of metabolic circuitry

The hypothalamus contains a core circuitry that communicates with the brainstem and spinal cord to regulate energy balance. Because metabolic phenotype is influenced by environmental variables during perinatal development, it is important to understand how these neural pathways form in order to identify key signaling pathways that are responsible for metabolic programming. Recent progress in defining gene expression events that direct early patterning and cellular specification of the hypothalamus, as well as advances in our understanding of hormonal control of central neuroendocrine pathways, suggest several key regulatory nodes that may represent targets for metabolic programming of brain structure and function. This review focuses on components of central circuitry known to regulate various aspects of energy balance and summarizes what is known about their developmental neurobiology within the context of metabolic programming.

Epigenetic mechanisms affecting regulation of energy balance: many questions, few answers

Extensive human and animal model data show that nutrition and other environmental influences during critical periods of embryonic, fetal, and early postnatal life can affect the development of body weight regulatory pathways, with permanent consequences for risk of obesity. Epigenetic processes are widely viewed as a leading mechanism to explain the lifelong persistence of such "developmental programming" of energy balance. Despite meaningful progress in recent years, however, significant research obstacles impede our ability to test this hypothesis. Accordingly, this review attempts to summarize progress toward answering the following outstanding questions: Is epigenetic dysregulation a major cause of human obesity? In what cells/tissues is epigenetic regulation most important for energy balance? Does developmental programming of human body weight regulation occur via epigenetic mechanisms? Do epigenetic mechanisms have a greater impact on food intake or energy expenditure? Does epigenetic inheritance contribute to transgenerational patterns of obesity? In each case, significant obstacles and suggested approaches to surmounting them are elaborated.

Sensitive periods for hormonal programming of the brain

During sensitive periods, information from the external and internal environment that occurs during particular phases of development is relayed to the brain to program neural development. Hormones play a central role in this process. In this review, we first discuss sexual differentiation of the brain as an example of hormonal programming. Using sexual differentiation, we define sensitive periods, review cellular and molecular processes that can explain their restricted temporal window, and discuss challenges in determining the precise timing of the temporal window. We then briefly review programming effects of other hormonal systems and discuss how programming of these systems interact with sexual differentiation.

Major epigenetic development distinguishing neuronal and non-neuronal cells occurs postnatally in the murine hypothalamus

Prenatal and early postnatal environment can persistently alter one's risk of obesity. Environmental effects on hypothalamic developmental epigenetics constitute a likely mechanism underlying such 'developmental programming' of energy balance regulation. To advance our understanding of these processes, it is essential to develop approaches to disentangle the cellular and regional heterogeneity of hypothalamic developmental epigenetics. We therefore performed genome-scale DNA methylation profiling in hypothalamic neurons and non-neuronal cells at postnatal day 0 (P0) and P21 and found, surprisingly, that most of the DNA methylation differences distinguishing these two cell types are established postnatally. In particular, neuron-specific increases in DNA methylation occurred extensively at genes involved in neuronal development. Quantitative bisulfite pyrosequencing verified our methylation profiling results in all 15 regions examined, and expression differences were associated with DNA methylation at several genes. We also identified extensive methylation differences between the arcuate (ARH) and paraventricular nucleus of the hypothalamus (PVH). Integrating these two data sets showed that genomic regions with PVH versus ARH differential methylation strongly overlap with those undergoing neuron-specific increases from P0 to P21, suggesting that these developmental changes occur preferentially in either the ARH or PVH. In particular, neuron-specific methylation increases at the 3' end of Shh localized to the ARH and were positively associated with gene expression. Our data indicate a key role for DNA methylation in establishing the gene expression potential of diverse hypothalamic cell types, and provide the novel insight that early postnatal life is a critical period for cell type-specific epigenetic development in the murine hypothalamus.

Neonatal leptin exposure specifies innervation of presympathetic hypothalamic neurons and improves the metabolic status of leptin-deficient mice

The paraventricular nucleus of the hypothalamus (PVH) consists of distinct functional compartments regulating neuroendocrine, behavioral, and autonomic activities that are involved in the homeostatic control of energy balance. These compartments receive synaptic inputs from neurons of the arcuate nucleus of the hypothalamus (ARH) that contains orexigenic agouti-related peptide (AgRP) and anorexigenic pro-opiomelanocortin (POMC) neuropeptides. The axon outgrowth from the ARH to PVH occurs during a critical postnatal period and is influenced by the adipocyte-derived hormone leptin, which promotes its development. However, little is known about leptin's role in specifying patterns of cellular connectivity in the different compartments of the PVH. To address this question, we used retrograde and immunohistochemical labeling to evaluate neuronal inputs onto sympathetic preautonomic and neuroendocrine neurons in PVH of leptin-deficient mice (Lep(ob)/Lep(ob)) exposed to a postnatal leptin treatment. In adult Lep(ob)/Lep(ob) mice, densities of AgRP- and α-melanocortin stimulating hormone (αMSH)-immunoreactive fibers were significantly reduced in neuroendocrine compartments of the PVH, but only AgRP were reduced in all regions containing preautonomic neurons. Moreover, postnatal leptin treatment significantly increased the density of AgRP-containing fibers and peptidergic inputs onto identified preautonomic, but not onto neuroendocrine cells. Neonatal leptin treatment neither rescued αMSH inputs onto neuroendocrine neurons, nor altered cellular ratios of inhibitory and excitatory inputs. These effects were associated with attenuated body weight gain, food intake and improved physiological response to sympathetic stimuli. Together, these results provide evidence that leptin directs cell type-specific patterns of ARH peptidergic inputs onto preautonomic neurons in the PVH, which contribute to normal energy balance regulation.

Unraveling the mechanisms responsible for the comorbidity between metabolic syndrome and mental health disorders

The increased prevalence and high comorbidity of metabolic syndrome (MetS) and mental health disorders (MHDs) have prompted investigation into the potential contributing mechanisms. There is a bidirectional association between MetS and MHDs including schizophrenia, bipolar disorder, depression, anxiety, attention-deficit/hyperactivity disorder, and autism spectrum disorders. Medication side effects and social repercussions are contributing environmental factors, but there are a number of shared underlying neurological and physiological mechanisms that explain the high comorbidity between these two disorders. Inflammation is a state shared by both disorders, and it contributes to disruptions of neuroregulatory systems (including the serotonergic, dopaminergic, and neuropeptide Y systems) as well as dysregulation of the hypothalamic-pituitary-adrenal axis. MetS in pregnant women also exposes the developing fetal brain to inflammatory factors that predispose the offspring to MetS and psychopathologies. Due to the shared nature of these conditions, treatment should address aspects of both mental health and metabolic disorders. Additionally, interventions that can interrupt the transfer of increased risk of the disorders to the next generation need to be developed. © 2013 S. Karger AG, Basel.

Maternal high fat diet consumption during the perinatal period programs offspring behavior

The environment that a developing offspring experiences during the perinatal period is markedly influenced by maternal health and diet composition. Evidence from both epidemiological studies and animal models indicates that maternal diet and metabolic status play a critical role in programming the neural circuitry that regulates behavior, resulting in long-term consequences for offspring behavior. Maternal diet and metabolic state influence the behavior of offspring directly by impacting the intrauterine environment and indirectly by modulating maternal behavior. The mechanisms by which maternal diet and metabolic profile shape the perinatal environment remain largely unknown, but recent research has found that increases in inflammatory cytokines, nutrients (glucose and fatty acids), and hormones (insulin and leptin) affect the environment of the developing offspring. Offspring exposed to maternal obesity and high fat diet consumption during development are more susceptible to developing mental health and behavioral disorders such as anxiety, depression, attention deficit hyperactivity disorder, and autism spectrum disorders. Recent evidence suggests that this increased risk for behavioral disorders is driven by modifications in the development of neural pathways involved in behavioral regulation. In particular, research indicates that the development of the serotonergic system is impacted by exposure to maternal obesity and high fat diet consumption, and this disruption may underlie many of the behavioral disturbances observed in these offspring. Given the high rates of obesity and high fat diet consumption in pregnant women, it is vital to examine the influence that maternal nutrition and metabolic profile have on the developing offspring.

Testing the efficacy of quercetin in mitigating bisphenol A toxicity in liver and kidney of mice

Quercetin (3,5,7,3',4'-pentahydroxy flavone) is a potent antioxidant found in various fruits and vegetables. The present investigation was an attempt to evaluate the mitigatory effect of quercetin on the damage caused by bisphenol A (BPA; 2,2-bis (4-hydroxyphenyl) propane), a well-known xenoestrogen, on liver and kidney of mice. Swiss strain adult male albino mice were orally administered with 120 and 240 mg/kg body weight (bw)/day BPA with or without quercetin (60 mg/kg bw/day) for 30 days. On the completion of the treatment period, animals were killed; organs were isolated and used for the study. Results revealed that oral administration of BPA for 30 days caused significant and dose-dependent decrease in body weight. Absolute and relative organ weights, total lipid and cholesterol contents were significantly increased in liver and kidney of mice when compared with vehicle control. BPA treatment also caused, when compared with vehicle control, a statistically significant reductions in the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase as well as in glutathione and total ascorbic acid contents; however, significant increase was found in malondialdehyde (MDA) levels. Histopathological studies revealed hepatocellular necrosis, cytoplasmic vacuolization and decrease in hepatocellular compactness in liver as well as distortion of the tubules, increased vacuolization, necrosis and disorganization of glomerulus in the kidney of BPA-treated mice. All these effects were dose-dependent. Co-treatment with quercetin (60 mg/kg bw) and BPA (low dose and high dose) alleviates the changes in body weight, as well as absolute and relative organ weights of mice. It also ameliorates the oxidative stress created by BPA by lowering MDA levels and by increasing enzymatic and nonenzymatic antioxidants as well as it brings back the normal histoarchitecture of liver and kidney of mice. The present results revealed that graded doses of BPA caused oxidative damage in liver and kidney of mice, which is mitigated by quercetin.

Early postnatal overnutrition: potential roles of gastrointestinal vagal afferents and brain-derived neurotrophic factor

Abnormal perinatal nutrition (APN) results in a predisposition to develop obesity and the metabolic syndrome and thus may contribute to the prevalence of these disorders. Obesity, including that which develops in organisms exposed to APN, has been associated with increased meal size. Vagal afferents of the gastrointestinal (GI) tract contribute to regulation of meal size by transmitting satiation signals from gut-to-brain. Consequently, APN could increase meal size by altering this signaling, possibly through changes in expression of factors that control vagal afferent development or function. Here two studies that addressed these possibilities are reviewed. First, meal patterns, meal microstructure, and the structure and density of vagal afferents that innervate the intestine were examined in mice that experienced early postnatal overnutrition (EPO). These studies provided little evidence for EPO effects on vagal afferents as it did not alter meal size or vagal afferent density or structure. However, these mice exhibited modest hyperphagia due to a satiety deficit. In parallel, the possibility that brain-derived neurotrophic factor (BDNF) could mediate APN effects on vagal afferent development was investigated. Brain-derived neurotrophic factor was a strong candidate because APN alters BDNF levels in some tissues and BDNF knockout disrupts development of vagal sensory innervation of the GI tract. Surprisingly, smooth muscle-specific BDNF knockout resulted in early-onset obesity and hyperphagia due to increases in meal size and frequency. Microstructure analysis revealed decreased decay of intake rate during a meal in knockouts, suggesting that the loss of vagal negative feedback contributed to their increase in meal size. However, meal-induced c-Fos activation within the dorsal vagal complex suggested this effect could be due to augmentation of vago-vagal reflexes. A model is proposed to explain how high-fat diet consumption produces increased obesity in organisms exposed to APN, and may be required to reveal effects of EPO on vagal function.

Tanycytes of the hypothalamic median eminence form a diet-responsive neurogenic niche

Adult hypothalamic neurogenesis has been recently reported, but the cell of origin and function of these newborn neurons are unknown. We utilize genetic fate mapping to show that median eminence tanycytes generate newborn neurons; blocking this neurogenesis alters weight and metabolic activity in adult mice. These findings describe a previously unreported neurogenic niche within the mammalian hypothalamus with important implications for metabolism.

Influence of pre- and peri-natal nutrition on skeletal acquisition and maintenance

Early life nutrition has substantial influences on postnatal health, with both under- and overnutrition linked with permanent metabolic changes that alter reproductive and immune function and significantly increase metabolic disease risk in offspring. Since perinatal nutrition depends in part on maternal metabolic condition, maternal diet during gestation and lactation is a risk factor for adult metabolic disease. Such developmental responses may be adaptive, but might also result from constraints on, or pathological changes to, normal physiology. The rising prevalence of both obesity and osteoporosis, and the identification of links among bone, fat, brain, and gut, suggest that obesity and osteoporosis may be related, and moreover that their roots may lie in early life. Here we focus on evidence for how maternal diet during gestation and lactation affects metabolism and skeletal acquisition in humans and in animal models. We consider the effects of overall caloric restriction, and macronutrient imbalances including high fat, high sucrose, and low protein, compared to normal diet. We then discuss potential mechanisms underlying the skeletal responses, including perinatal developmental programming via disruption of the perinatal leptin surge and/or epigenetic changes, to highlight unanswered questions and identify the most critical areas for future research.

The Impact of Maternal High-Fat Diet Consumption on Neural Development and Behavior of Offspring

Maternal diet and metabolic state are important factors in determining the environment experienced during perinatal development. Epidemiological studies and evidence from animal models provide evidence that a mother's diet and metabolic condition are important in programming the neural circuitry that regulates behavior, resulting in a persistent impact on the offspring's behavior. Potential mechanisms by which maternal diet and metabolic profile influence the perinatal environment include placental dysfunction and increases in circulating factors such as inflammatory cytokines, nutrients (glucose and fatty acids) and hormones (insulin and leptin). Maternal obesity and high-fat diet (HFD) consumption exposure during development have been observed to increase the risk of developing serious mental health and behavioral disorders including anxiety, depression, attention deficit hyperactivity disorder and autism spectrum disorder. The increased risk of developing these behavioral disorders is postulated to be due to perturbations in the development of neural pathways that regulate behavior, including the serotonergic, dopaminergic and melanocortinergic systems. It is critical to examine the influence that a mother's nutrition and metabolic profile have on the developing offspring considering the current and alarmingly high prevalence of obesity and HFD consumption in pregnant women.

Leptin in early life: a key factor for the development of the adult metabolic profile

Leptin levels during the perinatal period are important for the development of metabolic systems involved in energy homeostasis. In rodents, there is a postnatal leptin surge, with circulating leptin levels increasing around postnatal day (PND) 5 and peaking between PND 9 and PND 10. At this time circulating leptin acts as an important trophic factor for the development of hypothalamic circuits that control energy homeostasis and food seeking and reward behaviors. Blunting the postnatal leptin surge results in long-term leptin insensitivity and increased susceptibility to diet-induced obesity during adulthood. Pharmacologically increased leptin levels in the postnatal period also have long-term effects on metabolism. Nevertheless, this effect is controversial as postnatal hyperleptinemia is reported to both increase and decrease the predisposition to obesity in adulthood. The different effects reported in the literature could be explained by the different moments at which this hormone was administered, suggesting that modifications of the neonatal leptin surge at specific time points could selectively affect the development of central and peripheral systems that are undergoing modifications at this moment resulting in different metabolic and behavioral outcomes. In addition, maternal nutrition and the hormonal environment during pregnancy and lactation may also modulate the offspring's response to postnatal modifications in leptin levels. This review highlights the importance of leptin levels during the perinatal period in the development of metabolic systems that control energy homeostasis and how modifications of these levels may induce long-lasting and potentially irreversible effects on metabolism.

Early metabolic programming of puberty onset: impact of changes in postnatal feeding and rearing conditions on the timing of puberty and development of the hypothalamic kisspeptin system

Kiss1 neurons have recently emerged as a putative conduit for the metabolic gating of reproduction, with leptin being a regulator of hypothalamic Kiss1 expression. Early perturbations of the nutritional status are known to predispose to different metabolic disorders later in life and to alter the timing of puberty; however, the potential underlying mechanisms remain poorly defined. Here we report how changes in the pattern of postnatal feeding affect the onset of puberty and evaluate key hormonal and neuropeptide [Kiss1/kisspeptin (Kp)] alterations linked to these early nutritional manipulations. Female rats were raised in litters of different sizes: small (four pups per dam: overfeeding), normal (12 pups per dam), and large litters (20 pups per litter: underfeeding). Postnatal overfeeding resulted in persistently increased body weight and earlier age of vaginal opening, as an external sign of puberty, together with higher levels of leptin and hypothalamic Kiss1 mRNA. Conversely, postnatal underfeeding caused a persistent reduction in body weight, lower ovarian and uterus weights, and delayed vaginal opening, changes that were paralleled by a decrease in leptin and Kiss1 mRNA levels. Kisspeptin-52 immunoreactivity (Kp-IR) in the hypothalamus displayed similar patterns, with lower numbers of Kp-IR neurons in the arcuate nucleus of postnatally underfed animals, and a trend for increased Kp-positive fibers in the periventricular area of early overfed rats. Yet, gonadotropin responses to Kp at puberty were similar in all groups, except for enhanced responsiveness to low doses of Kp-10 in postnatally underfed rats. In conclusion, our data document that the timing of puberty is sensitive to both overfeeding and subnutrition during early (postnatal) periods and suggest that alterations in hypothalamic expression of Kiss1/kisspeptin may underlie at least part of such programming phenomenon.

Leptin signaling modulates the activity of urocortin 1 neurons in the mouse nonpreganglionic Edinger-Westphal nucleus

A recent study systematically characterized the distribution of the long form of the leptin receptor (LepRb) in the mouse brain and showed substantial LepRb mRNA expression in the nonpreganglionic Edinger-Westphal nucleus (npEW) in the rostroventral part of the midbrain. This nucleus hosts the majority of urocortin 1 (Ucn1) neurons in the rodent brain, and because Ucn1 is a potent satiety hormone and electrical lesioning of the npEW strongly decreases food intake, we have hypothesized a role of npEW-Ucn1 neurons in leptin-controlled food intake. Here, we show by immunohistochemistry that npEW-Ucn1 neurons in the mouse contain LepRb and respond to leptin administration with induction of the Janus kinase 2-signal transducer and activator of transcription 3 pathway, both in vivo and in vitro. Furthermore, systemic leptin administration increases the Ucn1 content of the npEW significantly, whereas in mice that lack LepRb (db/db mice), the npEW contains considerably reduced amount of Ucn1. Finally, we reveal by patch clamping of midbrain Ucn1 neurons that leptin administration reduces the electrical firing activity of the Ucn1 neurons. In conclusion, we provide ample evidence for leptin actions that go beyond leptin's well-known targets in the hypothalamus and propose that leptin can directly influence the activity of the midbrain Ucn1 neurons.

Central dopaminergic circuitry controlling food intake and reward: implications for the regulation of obesity

Prevalence of obesity in the general population has increased in the past 15 years from 15% to 35%. With increasing obesity, the coincident medical and social consequences are becoming more alarming. Control over food intake is crucial for the maintenance of body weight and represents an important target for the treatment of obesity. Central nervous system mechanisms responsible for control of food intake have evolved to sense the nutrient and energy levels in the organism and to coordinate appropriate responses to adjust energy intake and expenditure. This homeostatic system is crucial for maintenance of stable body weight over long periods of time of uneven energy availability. However, not only the caloric and nutritional value of food but also hedonic and emotional aspects of feeding affect food intake. In modern society, the increased availability of highly palatable and rewarding (fat, sweet) food can significantly affect homeostatic balance, resulting in dysregulated food intake. This review will focus on the role of hypothalamic and mesolimbic/mesocortical dopaminergic (DA) circuitry in coding homeostatic and hedonic signals for the regulation of food intake and maintenance of caloric balance. The interaction of dopamine with peripheral and central indices of nutritional status (e.g., leptin, ghrelin, neuropeptide Y), and the susceptibility of the dopamine system to prenatal insults will be discussed. Additionally, the importance of alterations in dopamine signaling that occur coincidently with obesity will be addressed.

Perinatal exposure to high-fat diet programs energy balance, metabolism and behavior in adulthood

The perinatal environment plays an important role in programming many aspects of physiology and behavior including metabolism, body weight set point, energy balance regulation and predisposition to mental health-related disorders such as anxiety, depression and attention deficit hyperactivity disorder. Maternal health and nutritional status heavily influence the early environment and have a long-term impact on critical central pathways, including the melanocortinergic, serotonergic system and dopaminergic systems. Evidence from a variety of animal models including rodents and nonhuman primates indicates that exposure to maternal high-fat diet (HFD) consumption programs offspring for increased risk of adult obesity. Hyperphagia and increased preference for fatty and sugary foods are implicated as mechanisms for the increased obesity risk. The effects of maternal HFD consumption on energy expenditure are unclear, and future studies need to address the impact of perinatal HFD exposure on this important component of energy balance regulation. Recent evidence from animal models also indicates that maternal HFD consumption increases the risk of offspring developing mental health-related disorders such as anxiety. Potential mechanisms for perinatal HFD programming of neural pathways include circulating factors, such as hormones (leptin, insulin), nutrients (fatty acids, triglycerides and glucose) and inflammatory cytokines. As maternal HFD consumption and obesity are common and rapidly increasing, we speculate that future generations will be at increased risk for both metabolic and mental health disorders. Thus, it is critical that future studies identify therapeutic strategies that are effective at preventing maternal HFD-induced malprogramming.

Molecular pathways controlling development of thalamus and hypothalamus: from neural specification to circuit formation

The embryonic diencephalon gives rise to the vertebrate thalamus and hypothalamus, which play essential roles in sensory information processing and control of physiological homeostasis and behavior, respectively. In this review, we present new steps toward characterizing the molecular pathways that control development of these structures, based on findings in a variety of model organisms. We highlight advances in understanding how early regional patterning is orchestrated through the action of secreted signaling molecules such as Sonic hedgehog and fibroblast growth factors. We address the role of individual transcription factors in control of the regional identity and neural differentiation within the developing diencephalon, emphasizing the contribution of recent large-scale gene expression studies in providing an extensive catalog of candidate regulators of hypothalamic neural cell fate specification. Finally, we evaluate the molecular mechanisms involved in the experience-dependent development of both thalamo-cortical and hypothalamic neural circuitry.

Obesity and leptin resistance: distinguishing cause from effect

Because leptin reduces food intake and body weight, the coexistence of elevated leptin levels with obesity is widely interpreted as evidence of 'leptin resistance.' Indeed, obesity promotes a number of cellular processes that attenuate leptin signaling (referred to here as 'cellular leptin resistance') and amplify the extent of weight gain induced by genetic and environmental factors. As commonly used, however, the term 'leptin resistance' embraces a range of phenomena that are distinct in underlying mechanisms and pathophysiological implications. Moreover, the induction of cellular leptin resistance by obesity complicates efforts to distinguish the mechanisms that predispose to weight gain from those that result from it. We suggest a framework for approaching these issues and important avenues for future investigation.

Effects of undernourishment on the hypothalamic orexinergic system

The present study examined the effects of a severely restricted diet during the pre- and postnatal periods with later nutritional rehabilitation on orexin hypothalamic neurons in male and female Wistar rats. Immunocytochemistry was used to reveal orexin-immunoreactive (orexin-ir) cells in the ventromedial hypothalamus (VMH), dorsomedial hypothalamus (DMH), lateral hypothalamic area (LH) and the perifornical nucleus (PF). Dietary restriction decreased the number of orexin-ir cells in the LH, whereas DMH or PF orexin-ir populations were not affected in either male or female rats. Nutritional rehabilitation resulted in a differential recovery that depended on the period during which rehabilitation occurred and on the sex of the animal. In summary, our study suggests that the hypothalamic nuclei implicated in eating behavior present a differential vulnerability to adverse environmental conditions during development. Specifically, among the studied nuclei only the LH orexin-ir cells were sensitive to severe food deprivation during development in male and female rats. These results suggest that starvation interferes with developmental events that occur during CNS sexual differentiation.

Early life programming and neurodevelopmental disorders

For more than a century, clinical investigators have focused on early life as a source of adult psychopathology. Early theories about psychic conflict and toxic parenting have been replaced by more recent formulations of complex interactions of genes and environment. Although the hypothesized mechanisms have evolved, a central notion remains: early life is a period of unique sensitivity during which experience confers enduring effects. The mechanisms for these effects remain almost as much a mystery today as they were a century ago. Recent studies suggest that maternal diet can program offspring growth and metabolic pathways, altering lifelong susceptibility to diabetes and obesity. If maternal psychosocial experience has similar programming effects on the developing offspring, one might expect a comparable contribution to neurodevelopmental disorders, including affective disorders, schizophrenia, autism, and eating disorders. Due to their early onset, prevalence, and chronicity, some of these disorders, such as depression and schizophrenia, are among the highest causes of disability worldwide according to the World Health Organization 2002 report. Consideration of the early life programming and transcriptional regulation in adult exposures supports a critical need to understand epigenetic mechanisms as a critical determinant in disease predisposition. Incorporating the latest insight gained from clinical and epidemiological studies with potential epigenetic mechanisms from basic research, the following review summarizes findings from a workshop on Early Life Programming and Neurodevelopmental Disorders held at the University of Pennsylvania in 2009.

Meal parameters and vagal gastrointestinal afferents in mice that experienced early postnatal overnutrition

Early postnatal overnutrition results in a predisposition to develop obesity due in part to hypothalamic and sympathetic dysfunction. Potential involvement of another major regulatory system component--the vagus nerve--has not been examined. Moreover, feeding disturbances have rarely been investigated prior to development of obesity when confounds due to obesity are minimized. To examine these issues, litters were culled on the day of birth to create small litters (SL; overnutrition), or normal size litters (NL; normal nutrition). Body weight, fat pad weight, meal patterns, and vagal sensory duodenal innervation were compared between SL and NL adult mice prior to development of obesity. Meal patterns were studied 18 h/day for 3 weeks using a balanced diet. Then vagal mechanoreceptors were labeled using anterograde transport of wheatgerm agglutinin-horseradish peroxidase injected into the nodose ganglion and their density and morphology were examined. Between postnatal day 1 and weaning, body weight of SL mice was greater than for NL mice. By young adulthood it was similar in both groups, whereas SL fat pad weight was greater in males, suggesting postnatal overnutrition produced a predisposition to obesity. SL mice exhibited increased food intake, decreased satiety ratio, and increased first meal rate (following mild food deprivation) compared to NL mice, suggesting postnatal overnutrition disrupted satiety. The density and structure of intestinal IGLEs appeared similar in SL and NL mice. Thus, although a vagal role cannot be excluded, our meal parameter and anatomical findings provided no evidence for significant postnatal overnutrition effects on vagal gastrointestinal afferents.

Leptin intake during the suckling period improves the metabolic response of adipose tissue to a high-fat diet

BACKGROUND

The intake of leptin during the suckling period protects against obesity and improves insulin and central leptin sensitivity in adult rats.

OBJECTIVE

We analyzed whether leptin treatment to neonates may also improve later peripheral leptin sensitivity in adipose tissue under high-fat (HF) diet conditions.

DESIGN

Male rats were supplemented with a daily oral dose of leptin or the vehicle (controls) during the suckling period. After weaning, animals were fed a normal-fat or an HF diet until the age of 6 months. At this age, mRNA and protein levels of the long-form leptin receptor (OB-Rb) and the expression of other genes related with energy metabolism were measured in various adipose depots (inguinal, mesenteric and retroperitoneal).

RESULTS

HF-diet feeding resulted in lower OB-Rb mRNA and protein levels in internal depots in controls but not in leptin-treated animals; these animals maintained OB-Rb mRNA and protein levels under HF-diet conditions in these depots, particularly in the mesenteric one, and this was accompanied by increased expression of genes related with energy uptake (GLUT4, CD36), fatty acid oxidation (peroxisome proliferator activated receptor-alpha (PPARalpha), CPT1, UCP3) and lipogenesis (PPARgamma, GPAT). Leptin-treatment also ameliorated HF-diet-induced hepatic fat accumulation occurring in control animals.

CONCLUSION

Leptin treatment during the suckling period may improve the lasting effects of HF-diet feeding on leptin receptor abundance in the adipose tissue and increase its oxidative capacity, resulting in a better handling and partitioning of excess fuel. This, together with the described improvement of central leptin sensitivity, may explain why these animals are more protected against diet-induced obesity and its metabolic-related disorders.

Gamma-protocadherins regulate the functional integrity of hypothalamic feeding circuitry in mice

The hypothalamic neuronal circuits that modulate energy homeostasis become mature and functional during early postnatal life. However, the molecular mechanism underlying this developmental process remains largely unknown. Here we use a mouse genetic approach to investigate the role of gamma-protocadherins (Pcdh-gammas) in hypothalamic neuronal circuits. First, we show that rat insulin promoter (RIP)-Cre conditional knockout mice lacking Pcdh-gammas in a broad subset of hypothalamic neurons are obese and hyperphagic. Second, specific deletion of Pcdh-gammas in anorexigenic proopiomelanocortin (POMC) expressing neurons also leads to obesity. Using cell lineage tracing, we show that POMC and RIP-Cre expressing neurons do not overlap but interact with each other in the hypothalamus. Moreover, excitatory synaptic inputs are reduced in Pcdh-gamma deficient POMC neurons. Genetic evidence from both knockout models shows that Pcdh-gammas can regulate POMC neuronal function autonomously and non-autonomously through cell-cell interaction. Taken together, our data demonstrate that Pcdh-gammas regulate the formation and functional integrity of hypothalamic feeding circuitry in mice.

Metabolic imprinting in obesity

Increasing evidence indicates that early metabolic programming contributes to escalating obesity rates in children and adults. Metabolic imprinting is involved in the establishment of set points for physiologic and metabolic responses in adulthood. Evidence from epidemiological studies and animal models indicates that maternal health and nutritional status during gestation and lactation have long-term effects on central and peripheral systems that regulate energy balance in the developing offspring. Perinatal nutrition also impacts susceptibility to developing metabolic disorders and plays a role in programming body weight set points. The states of maternal energy status and health that are implicated in predisposing offspring to increased risk of developing obesity include maternal overnutrition, diabetes, and undernutrition. This chapter discusses the evidence from epidemiologic studies and animal models that each of these states of maternal energy status results in metabolic imprinting of obesity in offspring. Also, the potential molecular mediators of metabolic imprinting of obesity by maternal energy status including glucose, insulin, leptin, inflammatory cytokines and epigenetic mechanisms are considered.

Bisphenol A: Perinatal exposure and body weight

Bisphenol A (BPA) is a component of polycarbonate and other plastics including resins that line food and beverage containers. BPA is known to leach from products in contact with food and drink, and is therefore thought to be routinely ingested. In a recent cross sectional study, BPA was detected in urine samples from 92.6% of the US population examined. The potential for BPA to influence body weight is suggested by in vitro studies demonstrating effects of BPA on adipocyte differentiation, lipid accumulation, glucose transport and adiponectin secretion. Data from in vivo studies have revealed dose-dependent and sex dependent effects on body weight in rodents exposed perinatally to BPA. The mechanisms through which perinatal BPA exposure acts to exert persistent effects on body weight and adiposity remain to be determined. Possible targets of BPA action are discussed.

Role of various neurotransmitters in mediating the long-term endocrine consequences of prenatal alcohol exposure

Adult rats and mice born to dams exposed to alcohol (fetal alcohol-exposed [FAE]) exhibit enhanced activity of their hypothalamic-pituitary-adrenal (HPA) axis when exposed to stressors. However, the mechanisms responsible for this phenomenon remain incompletely understood. Here two possibilities are reviewed: one that pertains to nitric oxide (NO), an unstable gas that stimulates the HPA axis; and one that focuses on catecholamines, which also stimulate this axis. Significant alterations were not observed in levels of NO synthase, the enzyme responsible for NO formation, in the paraventricula nucleus (PVN) of FAE rats. However, the stimulatory influence of this gas on the hypothalamic-pituitary-adrenal (HPA) axis was enhanced in these animals, thereby providing a mechanism likely to participate in the neuroendocrine hyperactivity that is the hallmark of this model. It was also recently shown that, while the ability of catecholamines to release adrenocorticotropic hormone (ACTH) was comparable in control rats and rats exposed to alcohol during embryonic development, there was a significant upregulation of the C1 brain-stem region when these latter animals were exposed to mild footshocks. Since this region sends prominent projections to the PVN, its increased activity may participate in the HPA axis hyperactivity observed in FAE offspring. Finally, microarray technology was used to search for potential differences in genes present in the brains of control and FAE mice. When these brains were collected on day 17.5 of embryonic development, several genes were upregulated, while others were downregulated, which may provide potential new candidates that mediate the influence of prenatal alcohol on the HPA axis of adult offspring.

Maternal high-fat diet and fetal programming: increased proliferation of hypothalamic peptide-producing neurons that increase risk for overeating and obesity

Recent studies in adult and weanling rats show that dietary fat, in close association with circulating lipids, can stimulate expression of hypothalamic peptides involved in controlling food intake and body weight. In the present study, we examined the possibility that a fat-rich diet during pregnancy alters the development of these peptide systems in utero, producing neuronal changes in the offspring that persist postnatally in the absence of the diet and have long-term consequences. The offspring of dams on a high-fat diet (HFD) versus balanced diet (BD), from embryonic day 6 to postnatal day 15 (P15), showed increased expression of orexigenic peptides, galanin, enkephalin, and dynorphin, in the paraventricular nucleus and orexin and melanin-concentrating hormone in the perifornical lateral hypothalamus. The increased density of these peptide-expressing neurons, evident in newborn offspring as well as P15 offspring cross-fostered at birth to dams on the BD, led us to examine events that might be occurring in utero. During gestation, the HFD stimulated the proliferation of neuroepithelial and neuronal precursor cells of the embryonic hypothalamic third ventricle. It also stimulated the proliferation and differentiation of neurons and their migration toward hypothalamic areas where ultimately a greater proportion of the new neurons expressed the orexigenic peptides. This increase in neurogenesis, closely associated with a marked increase in lipids in the blood, may have a role in producing the long-term behavioral and physiological changes observed in offspring after weaning, including an increase in food intake, preference for fat, hyperlipidemia, and higher body weight.