Research In Rodent Models Research Articles

Differential responses to maternal diabetes in embryo and visceral yolk sac.

Introduction: Maternal diabetes during pregnancy is well known to be associated with a higher risk for structural birth defects in the offspring. Recent searches for underlying mechanisms have largely focused on aberrant processes in the embryo itself, although prior research in rodent models implicated dysfunction also of the visceral yolk sac. The objective of our research was to investigate both tissues within the conceptus simultaneously. Methods: We conducted unbiased transcriptome profiling by RNA sequencing on pairs of individual yolk sacs and their cognate embryos, using the non-obese diabetic (NOD) mouse model. The analysis was performed at gestational day 8.5 on morphologically normal specimen to circumvent confounding by defective development. Results: Even with large sample numbers (n = 33 in each group), we observed considerable variability of gene expression, primarily driven by exposure to maternal diabetes, and secondarily by developmental stage of the embryo. Only a moderate number of genes changed expression in the yolk sac, while in the embryo, the exposure distinctly influenced the relationship of gene expression levels to developmental progression, revealing a possible role for altered cell cycle regulation in the response. Also affected in embryos under diabetic conditions were genes involved in cholesterol biosynthesis and NAD metabolism pathways. Discussion: Exposure to maternal diabetes during gastrulation changes transcriptomic profiles in embryos to a substantially greater effect than in the corresponding yolk sacs, indicating that despite yolk sac being of embryonic origin, different mechanisms control transcriptional activity in these tissues. The effects of maternal diabetes on expression of many genes that are correlated with developmental progression (i.e. somite stage) highlight the importance of considering developmental maturity in the interpretation of transcriptomic data. Our analyses identified cholesterol biosynthesis and NAD metabolism as novel pathways not previously implicated in diabetic pregnancies. Both NAD and cholesterol availability affect a wide variety of cellular signaling processes, and can be modulated by diet, implying that prevention of adverse outcomes from diabetic pregnancies may require broad interventions, particularly in the early stages of pregnancy.

303 Overview of Paternal Programming in Livestock Species

Abstract The concept of developmental programming from a maternal standpoint is well established. Perhaps even more impactful, however, is developmental programming that may arise from paternal contributions when single sires are responsible for breeding multiple females. Research in rodent models has shown that paternal obesity, high fat or low protein diets, exercise, stress, and drug and alcohol exposure can lead to epigenetic modifications in sperm and seminal plasma. Some of these changes withstand the extensive remodeling associated with fertilization and early embryo development, culminating in discernable offspring phenotypes that remain present for multiple generations. Certainly, the observations in rodent models related to alterations in offspring body weight, adiposity, metabolic responses, bone density, and reproductive outcomes and function have implications for the livestock industries if similar paternal programming phenomena exist. Livestock production systems are robust and dynamic and many paradigms exist with potential to alter male germ line epigenome, with specific changes likely related to timing of aberrant conditions relative to spermatogenesis and sperm residence in the epididymis. Within the context of routine management systems, our livestock patriarchs can experience major diet and weight changes, transportation and handling stress, environmental extremes, and/or changes in exercise duration, frequency, and intensity. In addition, livestock managers may embrace the concept of delivering specific quantities and types of feedstuffs, and apply other interventions if proven beneficial. Several research groups using livestock models have revealed that epigenetic machinery delivered in sperm and seminal plasma can be altered. A sheep model demonstrated the feeding rumen-protected methionine to rams from weaning to puberty resulted in epigenetic and phenotypic alterations still present in the F2 generation. This presentation will review the status of literature regarding paternal programming, identify knowledge gaps, and suggest areas for future research efforts with potential to enhance production efficiencies of livestock operations.

Research Progress on Neuroprotection of Insulin-like Growth Factor-1 towards Glutamate-Induced Neurotoxicity.

Insulin-like growth factor-1 (IGF-1) and its binding proteins and receptors are widely expressed in the central nervous system (CNS), proposing IGF-1-induced neurotrophic actions in normal growth, development, and maintenance. However, while there is convincing evidence that the IGF-1 system has specific endocrine roles in the CNS, the concept is emerging that IGF-I might be also important in disorders such as ischemic stroke, brain trauma, Alzheimer’s disease, epilepsy, etc., by inducing neuroprotective effects towards glutamate-mediated excitotoxic signaling pathways. Research in rodent models has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 was administered by different routes, and several clinical studies have shown safety and promise of efficacy in neurological disorders of the CNS. Focusing on the relationship between IGF-1-induced neuroprotection and glutamate-induced excitatory neurotoxicity, this review addresses the research progress in the field, intending to provide a rationale for using IGF-I clinically to confer neuroprotective therapy towards neurological diseases with glutamate excitotoxicity as a common pathological pathway.

Drosophila Trachea as a Novel Model of COPD.

COPD, a chronic obstructive pulmonary disease, is one of the leading causes of death worldwide. Clinical studies and research in rodent models demonstrated that failure of repair mechanisms to cope with increased ROS and inflammation in the lung leads to COPD. Despite this progress, the molecular mechanisms underlying the development of COPD remain poorly understood, resulting in a lack of effective treatments. Thus, an informative, simple model is highly valued and desired. Recently, the cigarette smoke-induced Drosophila COPD model showed a complex set of pathological phenotypes that resemble those seen in human COPD patients. The Drosophila trachea has been used as a premier model to reveal the mechanisms of tube morphogenesis. The association of these mechanisms to structural changes in COPD can be analyzed by using Drosophila trachea. Additionally, the timeline of structural damage, ROS, and inflammation can be studied in live organisms using fluorescently-tagged proteins. The related function of human COPD genes identified by GWAS can be screened using respective fly homologs. Finally, the Drosophila trachea can be used as a high-throughput drug screening platform to identify novel treatments for COPD. Therefore, Drosophila trachea is an excellent model that is complementary to rodent COPD models.

Age-related impairments on the touchscreen paired associates learning (PAL) task in male rats

Discovery research in rodent models of cognitive aging is instrumental for identifying mechanisms of behavioral decline in old age that can be therapeutically targeted. Clinically relevant behavioral paradigms, however, have not been widely employed in aged rats. The current study aimed to bridge this translational gap by testing cognition in a cross-species touchscreen-based platform known as paired-associates learning (PAL) and then utilizing a trial-by-trial behavioral analysis approach. This study found age-related deficits in PAL task acquisition in male rats. Furthermore, trial-by-trial analyses and testing rats on a novel interference version of PAL suggested that age-related impairments were not due to differences in vulnerability to an irrelevant distractor, motivation, or to forgetting. Rather, impairment appeared to arise from vulnerability to accumulating, proactive interference, with aged animals performing worse than younger rats in later trial blocks within a single testing session. The detailed behavioral analysis employed in this study provides new insights into the etiology of age-associated cognitive deficits.

Alterations in connectivity of the bed nucleus of the stria terminalis during early abstinence in individuals with alcohol use disorder.

For individuals with Alcohol Use Disorder (AUD), long-term recovery is difficult in part due to symptoms of anxiety that occur during early abstinence and can trigger relapse. Research in rodent models of AUD has identified the bed nucleus of the stria terminalis (BNST), a small, sexually dimorphic, subcortical region, as critical for regulating anxiety-like behaviors during abstinence, particularly in female mice. Furthermore, prolonged alcohol use and subsequent abstinence alter BNST afferent and efferent connections to other brain regions. To our knowledge, however, no studies of early abstinence have investigated BNST structural connectivity in humans during abstinence; this study addresses that gap. Nineteen participants with AUD currently in early abstinence and 20 healthy controls completed a diffusion tensor imaging (DTI) scan. BNST structural connectivity was evaluated using probabilistic tractography. A linear mixed model was used to test between-groups differences in BNST network connectivity. Exploratory analyses were conducted to test for correlations between BNST connectivity and alcohol use severity and anxiety within the abstinence group. Sex was included as a factor for all analyses. The BNST showed stronger structural connectivity with the BNST network in early abstinence women than in control women, which was not seen in men. Women also showed region-specific differences, with stronger BNST-hypothalamus structural connectivity but weaker vmPFC-BNST structural connectivity than men. Exploratory analyses also demonstrated a relationship between alcohol use severity and vmPFC-BNST structural connectivity that was moderated by sex. This study is the first to demonstrate BNST structural connectivity differences in early abstinence and revealed key sex differences. The sex-specific differences in BNST structural connectivity during early abstinence could underlie known sex differences in abstinence symptoms and relapse risk and help to inform potential sex-specific treatments.

Developmental estrogenization: Prostate gland reprogramming leads to increased disease risk with aging

While estrogens are involved in normal prostate morphogenesis and function, inappropriate early-life estrogenic exposures, either in type, dose or timing, can reprogram the prostate gland and lead to increased disease risk with aging. This process is referred to as estrogen imprinting or developmental estrogenization of the prostate gland. The present review discusses published and new evidence for prostatic developmental estrogenization that includes extensive research in rodent models combined with epidemiology findings that together have helped to uncover the architectural and molecular underpinnings that promote this phenotype. Complex interactions between steroid receptors, developmental morphoregulatory factors, epigenetic machinery and stem-progenitor cell targets coalesce to hard wire structural, cellular and epigenomic reorganization of the tissue which retains a life-long memory of early-life estrogens, ultimately predisposing the gland to prostatitis, hyperplasia and carcinogenesis with aging.

Maternal exposure to organophosphate flame retardants alters locomotor and anxiety-like behavior in male and female adult offspring

Endocrine disrupting chemicals (EDCs) are chemicals found in our environment that interrupt typical endocrine function. Some flame retardants (FRs) are EDCs as shown in their interaction with steroid and nuclear receptors. Humans are consistently exposed to flame retardants as they are used in everyday items such as plastics, clothing, toys, and electronics. Polybrominated diphenyl ethers were used as the major FR until 2004, when they were replaced by organophosphate flame retardants (OPFRs). Previous research in rodent models utilizing a commercial flame retardant mixture containing OPFRs reported alterations in anxiety-like behavior in the elevated plus maze (EPM) for rodents perinatally exposed to OPFRs. In the present study we utilize wild-type mice maternally exposed (gestational day 7 to postnatal day 14) to either an OPFR mixture of tris(1,3-dichloro-2-propyl), triphenyl phosphate, and tricresyl phosphate or a sesame seed oil vehicle. These mice were evaluated for anxiety-like behavior in adulthood on the open field test (OFT) and the light/dark box (LDB) as well as the EPM. Outcomes from the OFT and LDB indicate that males and females maternally exposed to OPFRs exhibit altered locomotor activity. Results of the EPM were sex-specific as we did not observe an effect in females; however, effects in males differed depending on exposure condition. Males maternally exposed to OPFRs exhibited an anxiolytic-like phenotype in contrast to their vehicle counterparts. This effect in perinatally OPFR-exposed males was not due to alterations in locomotor activity. Our research illustrates that there are sex- and exposure-dependent effects of perinatal OPFR exposure on adult locomotor and anxiety-like behaviors in a mouse model.

Time-restricted feeding for the prevention of cardiometabolic diseases in high-stress occupations: a mechanistic review.

Factors such as shift work, poor diet, lack of physical activity, and irregular sleep patterns put men and women employed in high-stress occupations (e.g., firefighters, police officers) at risk for cardiometabolic diseases. Time-restricted feeding (TRF) is a new approach to combatting many of these diseases; it places an emphasis on when meals are consumed, rather than calorie content. By only manipulating the eating "window," and without changing the food composition of the diet, research in rodent models has shown promising results that have health implications in people, such as obesity prevention, improved insulin sensitivity, and decreased oxidative stress, inflammation, and cholesterol synthesis. Human trials remain limited and the current data are mixed with regard to TRF and improving health. Present findings suggest the timing of the feeding-fasting window, with feeding taking place in the waking hours and fasting in the evening hours, might offer the greatest benefit for improving cardiometabolic markers. Although additional human trials are needed, TRF might reset and synchronize metabolic "clocks" found throughout the body that are disturbed with obesity, shift work, and frequent eating. Therefore, TRF might offer an effective feeding-fasting paradigm with significant clinical implications for the management and treatment of cardiometabolic diseases observed in individuals in high-stress occupations in the United States and in the US population in general. This review outlines the current rodent and human evidence in these areas and the efficacy of TRF for improving human health.

Dopamine receptor manipulation does not alter patterns of partner preference in long-term marmoset pairs

The relationship between socially monogamous mates is dynamic and regulated by neurobiological influences. Research in rodent models has indicated a key role for the neurotransmitter dopamine (DA) and its receptors (DAR) in mediating the formation and maintenance of monogamous bonds. DAR activation was pharmacologically manipulated in marmosets housed in long-term pairs. Marmosets exposed to DAR manipulation were tested in a partner preference test under two social conditions: one in which their mate could visually observe their interactions with an opposite-sex individual, and one in which their pair mate could not visually observe these interactions. Marmosets displayed a spatial preference for the mate compared to an unfamiliar conspecific, however, they displayed a sexual preference for an unfamiliar conspecific over their mate. D1R manipulation had no impact on marmoset partner preference. However, activation of D2Rs reduced the time marmosets spent in contact with either stimulus animal, indicating a decrease in social interest, but did not reduce time spent in proximity to the stimulus animals nor number of sexual solicitations. Additionally, social context (visibility of the mate) did not influence marmoset behavior. These findings suggest that D2Rs may be involved in regulating generalized, but not partner-specific, social interest in marmoset monkeys.

Inflammation, Immunity, and Vaccine Development for the Gastric Pathogen Helicobacter pylori.

It has been over 30years since a link was established between H. pylori infection of the gastric mucosa and the development of chronic gastric diseases. Research in rodent models supported by data from human tissue demonstrated that the host immune response to H. pylori is limited by host regulatory T cells. Immunization has been shown to induce a potent Th1- and Th17-mediated immune response capable of eradicating or at least significantly reducing the bacterial load of H. pylori in the stomach in small animal models. These results have not translated well to humans. Clinical trials employing many of the strategies used in rodents for oral immunization including the use of a mucosal adjuvant such as Escherichia coli LT or delivery by attenuated enteric bacteria have failed to limit H. pylori infection and have highlighted the potential toxicity of exotoxin-based mucosal adjuvants. A recent study, however, utilizing a recombinant fusion protein of H. pylori urease and the subunit B of E. coli LT, was performed on over 4000 children. Efficacy of over 70% was demonstrated against naturally acquired infection compared to control volunteers one year post-immunization. Efficacy was reduced, but still above 50% at three years. This study provided new insight into the strategies for developing an improved vaccine for widespread use in countries with high infection rates and where gastric cancer (GC) remains one of the most common causes of death due to cancer.

MicroRNA-induced silencing in epilepsy: Opportunities and challenges for clinical application.

MicroRNAs are master regulators of gene expression. Single microRNAs influence multiple proteins within diverse molecular pathways and networks. Therefore, changes in levels or activity of microRNAs can have profound effects on cellular function. This makes dysregulated microRNA-induced silencing an attractive potential disease mechanism in complex disorders like epilepsy, where numerous cellular pathways and processes are affected simultaneously. Indeed, several years of research in rodent models have provided strong evidence that acute or recurrent seizures change microRNA expression and function. Moreover, altered microRNA expression has been observed in brain and blood from patients with various epilepsy disorders, such as tuberous sclerosis. MicroRNAs can be easily manipulated using sense or antisense oligonucleotides, opening up opportunities for therapeutic intervention. Here, we summarize studies using these techniques to identify microRNAs that modulate seizure susceptibility, describe protein targets mediating some of these effects, and discuss cellular pathways, for example neuroinflammation, that are controlled by epilepsy-associated microRNAs. We critically assess current gaps in knowledge regarding target- and cell-specificity of microRNAs that have to be addressed before clinical application as therapeutic targets or biomarkers. The recent progress in understanding microRNA function in epilepsy has generated strong momentum to encourage in-depth mechanistic studies to develop microRNA-targeted therapies. Developmental Dynamics 247:94-110, 2018. © 2017 Wiley Periodicals, Inc.

Neuroimmunology and neuroepigenetics in the establishment of sex differences in the brain.

The study of sex differences in the brain is a topic of neuroscientific study that has broad reaching implications for culture, society and biomedical science. Recent research in rodent models has led to dramatic shifts in our views of the mechanisms underlying the sexual differentiation of the brain. These include the surprising discoveries of a role for immune cells and inflammatory mediators in brain masculinization and a role for epigenetic suppression in brain feminization. How and to what degree these findings will translate to human brain development will be questions of central importance in future research in this field.

Advances in optogenetic and chemogenetic methods to study brain circuits in non-human primates.

Over the last 10years, the use of opto- and chemogenetics to modulate neuronal activity in research applications has increased exponentially. Both techniques involve the genetic delivery of artificial proteins (opsins or engineered receptors) that are expressed on a selective population of neurons. The firing of these neurons can then be manipulated using light sources (for opsins) or by systemic administration of exogenous compounds (for chemogenetic receptors). Opto- and chemogenetic tools have enabled many important advances in basal ganglia research in rodent models, yet these techniques have faced a slow progress in non-human primate (NHP) research. In this review, we present a summary of the current state of these techniques in NHP research and outline some of the main challenges associated with the use of these genetic-based approaches in monkeys. We also explore cutting-edge developments that will facilitate the use of opto- and chemogenetics in NHPs, and help advance our understanding of basal ganglia circuits in normal and pathological conditions.

Cerebral and Peripheral Metabolism to Predict Successful Reperfusion After Cardiac Arrest in Rats: A Microdialysis Study.

In clinical practice, monitoring of the efficacy of resuscitation can be challenging. The prediction of cerebral and overall outcome in particular is an unmet medical need. Microdialysis is a minimally invasive technique for the continuous determination of metabolic parameters in vivo. Using this technique, we set out to establish a model allowing for concomitant determination of cerebral and peripheral metabolism in a cardiac arrest setting in rodents. Microdialysis settings were optimized in vitro and then used in male Sprague-Dawley rats. Probes were implanted into the CA1 region of the right hippocampus and the right femoral vein. With a time interval of 8min, glucose, lactate, pyruvate, and glutamate levels were determined during baseline conditions, untreated ventricular fibrillation cardiac arrest, cardiopulmonary resuscitation (CPR), reperfusion, and death. In 16 rodents, restoration of spontaneous circulation was achieved in seven animals. Characteristic metabolic changes were evident during cardiac arrest and reperfusion with both probes. Ischemic patterns in peripheral compartments were delayed and more variable compared to the changes in cerebral metabolism highlighting the importance of cerebral metabolic monitoring. Microdialysis allowed distinguishing between survivors and non-survivors 8min after termination of CPR. Cerebral glutamate showed a trend toward higher levels in non-survivors during CPR. We established a new rodent model for research in hypoxic ischemic encephalopathy. This setting allows to investigate the impact of resuscitation methods on cerebral and peripheral metabolism simultaneously. The present model may be used to evaluate different resuscitation strategies in order to optimize brain survival in future studies.

Canine Leishmania vaccines: Still a long way to go

Dogs are the main reservoir host for zoonotic visceral leishmaniasis, a sand fly-borne disease caused by Leishmania infantum. In endemic areas, “susceptible” dogs suffer from a severe disease characterized by chronic polymorphic viscerocutaneous signs that manifest several months from the exposure, whereas “resistant” dogs can remain subclinically infected for years or lifelong. The protective immune response to Leishmania is cell-mediated; for visceralizing Leishmania species a mixed T helper (Th)1/Th2 response with a dominant Th1 profile is required for protection. The activation of the adaptive immune system in naturally resistant dogs is revealed by parasite-specific lymphoproliferation, delayed-type hypersensitivity, the production of interferon-γ and tumour necrosis factor-α cytokines, and enhanced macrophage leishmanicidal activity via nitric oxide. Hence, an effective canine Leishmania vaccine should induce strong and long-lasting Th1-dominated immunity to control both infection progression and the parasite transmissibility via the vector. Preclinical research in rodent models has evaluated the efficacy of several categories of Leishmania antigens including killed parasites, cell purified fractions, parasite protein components or subunits, single or multiple chimeric recombinant proteins, plasmid DNA and viral particles encoding parasite virulence factors. Promising antigen(s)/adjuvant combinations from each of the above categories have also been tested in dogs; they mostly resulted in limited or no protection in Phase I–II studies (designed to test vaccine safety, immunogenicity and laboratory-induced protection) in which vaccinated dogs were challenged by the artificial intravenous injection of high-load L. infantum promastigotes. The recombinant A2 antigen plus saponin conferred about 40% protection against infection by this challenge system and has been registered in Brazil as a canine vaccine (LeishTec®). An increasing number of efficacy studies have privileged the use of natural challenge consisting in the long-term exposure of vaccinated dogs in endemic settings (Phase III). A 2-year field model including regular assessments by a set of standard diagnostic markers useful for an accurate infection staging has been developed. Again, most of the vaccines tested by this system, which included several antigen categories and adjuvants, failed to protect against infection and disease. Only two vaccines, consisting of parasite purified fractions with saponin derivative adjuvants, showed to confer significant protection against disease and death under natural conditions, and have been registered as canine vaccines: FML-QuilA (Leishmune®) in Brazil, and LiESP/QA-21 (CaniLeish®) in Europe.

The neurotoxicity of nitrous oxide: the facts and "putative" mechanisms.

Nitrous oxide is a widely used analgesic agent, used also in combination with anaesthetics during surgery. Recent research has raised concerns about possible neurotoxicity of nitrous oxide, particularly in the developing brain. Nitrous oxide is an N-methyl-d-aspartate (NMDA)-antagonist drug, similar in nature to ketamine, another anaesthetic agent. It has been linked to post-operative cardiovascular problems in clinical studies. It is also widely known that exposure to nitrous oxide during surgery results in elevated homocysteine levels in many patients, but very little work has investigated the long term effect of these increased homocysteine levels. Now research in rodent models has found that homocysteine can be linked to neuronal death and possibly even cognitive deficits. This review aims to examine the current knowledge of mechanisms of action of nitrous oxide, and to describe some pathways by which it may have neurotoxic effects.

Functionally altered neurocircuits in a rat model of treatment-resistant depression show prominent role of the habenula

Treatment-resistant depression (TRD) remains a pressing clinical problem. Optimizing treatment requires better definition of the function and specificity of the brain circuits involved. To investigate disease-related alterations of brain function we used a genetic animal model of TRD, congenital learned helplessness (cLH), and functional magnetic resonance imaging as a translational tool. High-resolution regional cerebral blood volume (rCBV) and resting-state functional connectivity measurements were acquired at 9.4T to determine regional dysfunction and interactions that could serve as vulnerability markers for TRD. Effects of cLH on rCBV were determined by statistical parametric mapping using 35 atlas-based regions of interest. Effects of cLH on functional connectivity were assessed by seed region analyses. Significant bilateral rCBV reductions were observed in the lateral habenula, dentate gyrus and subiculum of cLH rats. In contrast, focal bilateral increase in rCBV was observed in the bed nucleus of stria terminalis (BNST), a component of the habenular neurocircuitry. Functional connectivity was primarily enhanced in cLH rats, most notably with respect to serotonergic projections from the dorsal raphe nucleus to the forebrain, within the hippocampal-prefrontal network and between the BNST and lateral frontal regions. Dysregulation of neurocircuitry similar to that observed in depressed patients was detected in cLH rats, supporting the validity of the TRD model and suitability of high-field fMRI as a translational technology to detect and monitor vulnerability markers. Our findings also define neurocircuits that can be studied for TRD treatment in patients, and could be employed for translational research in rodent models.

Development of a Simple Miniature Thermochemical Ablation Device Suitable for Tumor Ablation Research in Rodent Models

Thermochemical ablation is a recently developed minimally invasive method with potential for solid tumor treatment such as in liver cancer. A recently described prototype device, however, is too large for use in the more common rodent models of cancer. In this report we describe a simple, low-cost variant of the device that is easy to assemble, small enough to be readily applicable to small animal models, and then demonstrate its use in an ex vivo model for ablation. It should therefore enable study of the method without requiring specialized equipment or access to a machine shop for device manufacture.

Early Postnatal Nutrition Determines Adult Physical Activity and Energy Expenditure in Female Mice

Decades of research in rodent models has shown that early postnatal overnutrition induces excess adiposity and other components of metabolic syndrome that persist into adulthood. The specific biologic mechanisms explaining the persistence of these effects, however, remain unknown. On postnatal day 1 (P1), mice were fostered in control (C) or small litters (SL). SL mice had increased body weight and adiposity at weaning (P21), which persisted to adulthood (P180). Detailed metabolic studies indicated that female adult SL mice have decreased physical activity and energy expenditure but not increased food intake. Genome-scale DNA methylation profiling identified extensive changes in hypothalamic DNA methylation during the suckling period, suggesting that it is a critical period for developmental epigenetics in the mouse hypothalamus. Indeed, SL mice exhibited subtle and sex-specific changes in hypothalamic DNA methylation that persisted from early life to adulthood, providing a potential mechanistic basis for the sustained physiological effects. Expression profiling in adult hypothalamus likewise provided evidence of widespread sex-specific alterations in gene expression. Together, our data indicate that early postnatal overnutrition leads to a reduction in spontaneous physical activity and energy expenditure in females and suggest that early postnatal life is a critical period during which nutrition can affect hypothalamic developmental epigenetics.