Estrogen: A master regulator of bioenergetic systems in the brain and body

Estrogen is a fundamental regulator of the metabolic system of the female brain and body. Within the brain, estrogen regulates glucose transport, aerobic glycolysis, and mitochondrial function to generate ATP. In the body, estrogen protects against adiposity, insulin resistance, and type II diabetes, and regulates energy intake and expenditure. During menopause, decline in circulating estrogen is coincident with decline in brain bioenergetics and shift towards a metabolically compromised phenotype. Compensatory bioenergetic adaptations, or lack thereof, to estrogen loss could determine risk of late-onset Alzheimer’s disease. Estrogen coordinates brain and body metabolism, such that peripheral metabolic state can indicate bioenergetic status of the brain. By generating biomarker profiles that encompass peripheral metabolic changes occurring with menopause, individual risk profiles for decreased brain bioenergetics and cognitive decline can be created. Biomarker profiles could identify women at risk while also serving as indicators of efficacy of hormone therapy or other preventative interventions.     

Combined treatment with valproic acid and estrogen has neuroprotective effects in ovariectomized mice with Alzheimer’s disease

Postmenopausal women with Alzheimer’s disease (AD) exhibit dramatically reduced sensitivity to estrogen replacement therapy, which is though to be related to an estrogen receptor (ER)α/ERβ ratio imbalance arising from a significantly decreased level of ERs of the brain. The aim of our study was to investigate whether valproic acid (VPA) can enhance the beneficial effects of estrogen on cognitive function through restoration of ERα and ERβ expression in the brain. We removed the ovaries of female APP/PS1 mice to simulate the low estrogen levels present in postmenopausal women and then administered VPA (30 mg/kg, intraperitoneal injection, once daily), 17β-estradiol (E2) (2.4 μg, intraperitoneal injection, once daily), liquiritigenin (LG) (50 μg/kg, intragastric infusion, once daily), VPA + E2, or VPA + LG for 4 successive weeks. Compared with treatment with a single drug, treatment with VPA + E2 or VPA + LG significantly increased the level of glycogen synthase kinase 3β, increased the expression of estrogen receptor α, reduced the expression of small ubiquitin-like modifiers, and increased the level of estrogen receptor β. This resulted in enhanced sensitivity to estrogen therapy, reduced amyloid β aggregation, reduced abnormal phosphorylation of the tau protein, reduced neuronal loss, increased dendritic spine and postsynaptic density, and significantly alleviated memory loss and learning impairment in mice. This study was approved by the Chongqing Medical University Animal Protection and Ethics Committee, China on March 6, 2013.

Chinese Library Classification No. R453; R741; Q579.1+3     

Beta2-containing neuronal nicotinic receptors as major actors in the flexible choice between conflicting motivations

Beside a critical role in nicotine addiction, the role of nicotinic receptors in cognitive or emotional processes remains difficult to elucidate, mostly because of a lack of specificity of compounds and because they up or down regulate easily. Using knockout mice may be one key to elucidate the role of nicotinic receptors stimulated by their endogenous ligand acetylcholine. We and others have previously explored the behaviour of mice knockout for the beta2-subunit containing nicotinic receptor - β2*nAChRs - β2^−/− mice. These mice exhibit a particular kind of hyperactive locomotion, with profound deficits in cognitive and social interaction tasks, only when they have to show flexible choices. We wonder here whether the latter is due to a lack of motor control - i.e. motor impulsivity, a lack of estimation of reward value - i.e. cognitive impulsivity, and/or a lack of appropriate ranking or choice between different motivations.We designed behavioural tasks allowing the study of these distinct processes in mice. Our current results highlight the important role of β2*nAChRs in flexible behaviours in conflicting situations, such as social contact, spatial exploration and food consumption. They also show that the cognitive deficits exhibited by β2^−/− mice cannot be explained by impaired inhibitory behaviours.Although social cognition is considerably enriched in humans as compared to rodents, we provide here novel data for the neurobiology of flexible social behaviours that could ultimately be useful for humans. Indeed, the ability to show flexible behaviours and to display adapted social interactions is profoundly impaired in a myriad of psychiatric disorders.     

Central nervous system regulation of food intake and energy expenditure: role of galanin-mediated feeding behavior

Galanin is a neuropeptide widely expressed in the brain. It is implicated in energy expenditure, feeding, and the regulation of body weight. Numerous studies have revealed that galanin regulates food intake via galanin receptors, 5-HT_1A receptor and adrenergic α-2 receptor. In this review, we summarize recent findings that reveal the essential role of galanin in increasing food intake as well as body weight and that identify the individual galanin receptor subtypes involved in the brain’s modulation of food intake and energy expenditure, to provide a theoretical basis for further studies of different aspects of galanin action.     

Interleukin-6 Gene Knockout Influences Energy Balance Regulating Peptides in the Hypothalamic Paraventricular and Supraoptic Nuclei

Interleukin (IL)-6 is a pro-inflammatory cytokine that also affects metabolic function because IL-6 depleted (IL-6^−/−) mice develop late-onset obesity. IL-6 appears to act in the central nervous system, presumably in the hypothalamus, to increase energy expenditure that appears to involve stimulation of the sympathetic nervous system. In the present study, we explored possible central mechanisms for the effects exerted by IL-6 on body fat. Therefore, we measured the effects of IL-6 depletion in IL-6^−/− mice on expression of key hypothalamic peptide genes involved in energy balance by the real time polymerase chain reaction. Additionally, co-localisation between such peptides and IL-6 receptor α was investigated by immunohistochemistry. IL-6 deficiency decreased the expression of several peptides found in the paraventricular nucleus (PVN), which is a nucleus that has been attributed an adipostatic function. For example, corticotrophin-releasing hormone (CRH), which is reported to stimulate the sympathetic nervous system, was decreased by 40% in older IL-6^−/− mice. Oxytocin, which is reported to prevent obesity, was also decreased in older IL-6^−/− animals, as was arginine vasopressin (AVP). The IL-6 receptor α was abundantly expressed in the PVN, but also in the supraoptic nucleus, and was shown to be co-expressed to a high extent with CRH, AVP, oxytocin and thyrotrophin-releasing hormone. These data indicate that depletion of endogenous IL-6, a body fat suppressing cytokine, is associated with the decreased expression of CRH and oxytocin (i.e. energy balance regulating peptides) as well as AVP in the PVN. Because IL-6 receptor α is co-expressed with CRH, oxytocin and AVP, IL-6 could stimulate the expression of these peptides directly.     

Ghrelin‐mediated improvements in the metabolic phenotype in the R6/2 mouse model of Huntington's disease

Huntington's disease (HD) is a heritable neurodegenerative disorder, characterised by metabolic disturbances, along with cognitive and psychiatric impairments. Targeting metabolic HD dysfunction via the maintenance of body weight and fat mass and restoration of peripheral energy metabolism can improve the progression of neurological symptoms. In this respect, we focused on the therapeutic potential of the orexigenic peptide hormone ghrelin, which plays an important role in promoting a positive energy balance. In the present study, we found a significant disruption of circadian metabolic regulation in a R6/2 mouse HD model in the late stage of disease. Daily circadian rhythms of activity, energy expenditure, respiratory exchange ratio and feeding were strongly attenuated in R6/2 mice. During the rest phase, R6/2 mice had a higher total activity, elevated energy expenditure and excessive water consumption compared to control mice. We also found that, in the late stage of disease, R6/2 mice had ghrelin axis deficiency as a result of low circulating ghrelin levels, in addition to down‐regulation of the ghrelin receptor and several key signalling molecules in the hypothalamus, as well as a reduced responsiveness to exogenous peripheral ghrelin. We demonstrated that, in pre‐symptomatic mice, responsiveness to ghrelin is preserved. Chronic ghrelin treatment efficiently increased lean body mass and decreased the energy expenditure and fat utilisation of R6/2 mice in the early stage of disease. In addition, ghrelin treatment was also effective in the normalisation of drinking behaviour and the rest activity of these mice. Ghrelin treatment could provide a novel therapeutic possibility for delaying disease progression; however, deficiency in ghrelin receptor expression could limit its therapeutic potential in the late stage of disease.     

Interleukin-18 null mutation increases weight and food intake and reduces energy expenditure and lipid substrate utilization in high-fat diet fed mice

ObjectiveThe proinflammatory cytokine interleukin-18 (IL-18) putatively modulates food intake and energy metabolism, but the effects of IL-18 in high-fat diet fed animals are unknown. Whether IL-18 alters basal metabolic rate or metabolic processes of living is unknown. Here, we tested the hypothesis that IL-18 modulates weight gain, energy intake, whole-body energy expenditure, and utilization of lipid as a fuel substrate in high-fat diet fed mice.MethodsFood intake, whole-body metabolism, and motor activity of IL-18 knockout mice were compared to those of wildtype littermates; anorectic effects of intracerebroventricular IL-18 administration were compared between IL-18 receptor knockout, IL-18/IL-18R knockout and wildtype mice.ResultsChow-reared IL-18 knockout mice were overweight at 6 months of age and then gained excess weight on both low-fat and high-fat diets, ate more high-fat diet, and showed reduced whole-body energy expenditure and increased respiratory exchange ratios. Reductions in energy expenditure of IL-18 knockout mice were seen across fasting vs. feeding conditions, low- vs. high-fat diets, high vs. low levels of physical activity and times of day, suggesting actions on basal metabolic rate. The circadian amplitude of energy expenditure, but not respiratory exchange ratio, food intake, or motor activity, also was blunted in IL-18 knockout mice. Central IL-18 administration reduced high-fat diet intake in wildtype mice, but not in mice lacking the IL-18 receptor.ConclusionThe loss-of-function results support the hypothesis that endogenous IL-18 suppresses appetite and promote energy expenditure and lipid fuel substrate utilization not only during sickness, but also in healthy adults consuming high-fat diets.     

Is the CCK2 receptor essential for normal regulation of body weight and adiposity?

Cholecystokinin (CCK) is a gastrointestinal satiety signal released from the duodenum to terminate feeding, via CCK1 receptors. CCK2 receptors are considered to be involved in anxiety. CCK2 receptor knockout mice have increased body weight and food intake. Little is known regarding the effects of CCK2 receptor deficiency on adipose distribution and hypothalamic feeding regulators such as neuropeptide Y (NPY), a powerful stimulator of feeding. Adult (10 week) CCK2 receptor knockout and wild-type mice were anaesthetized and killed by decapitation. Brain sections, organs and fat tissue were dissected. Plasma leptin, insulin and brain NPY content were measured by radioimmunoassay. Female CCK2 receptor knockout mice weighed more than control mice (22.0 +/- 0.2 vs. 19.9 +/- 0.4 g, P < 0.05), with this difference being less marked in male mice (26.4 +/- 0.4 vs. 25.6 +/- 0.6 g). Fat masses in all locations sampled were significantly smaller in CCK2 receptor knockout mice of both genders (P < 0.05), resulting in lower plasma leptin and insulin levels. NPY concentrations were significantly increased in arcuate nucleus and anterior hypothalamus in both male and female CCK2 receptor knockout mice, and total hypothalamic NPY content was increased by 7 and 9% in males and females, respectively (P < 0.05). CCK2 receptor deletion was associated with increased body weight and hypothalamic NPY content, but reduced fat masses and plasma leptin and insulin. Increased NPY might contribute to increased food intake in CCK2 receptor knockout mice. Further work needs to focus on the metabolic changes.     

On the Central Mechanism Underlying Ghrelin's Chronic Pro-Obesity Effects in Rats: New Insights from Studies Exploiting a Potent Ghrelin Receptor Antagonist

In the present study, we explore the central nervous system mechanism underlying the chronic central effects of ghrelin with respect to increasing body weight and body fat. Specifically, using a recently developed ghrelin receptor antagonist, GHS-R1A (JMV2959), we investigate the role of GHS-R1A in mediating the effects of ghrelin on energy balance and on hypothalamic gene expression. As expected, in adult male rats, chronic central treatment with ghrelin for 14 days, when compared to vehicle-treated control rats, resulted in an increased body weight, lean mass and fat mass (assessed by dual X-ray absorptiometry), dissected white fat pad weight, cumulative food intake, food efficiency, respiratory exchange ratio and a decrease of energy expenditure. Co-administration of the ghrelin receptor antagonist JMV2959 suppressed/blocked the majority of these effects, with the notable exception of ghrelin-induced food intake and food efficiency. The hypothesis emerging from these data, namely that GHS-R1A mediates the chronic effects of ghrelin on fat accumulation, at least partly independent of food intake, is discussed in light of the accompanying data regarding the hypothalamic genes coding for peptides and receptors involved in energy balance regulation, which were found to have altered expression in these studies.     

Role of plasminogen in macrophage accumulation during liver repair

Introduction

Although the involvement of plasminogen in liver repair has been reported, its roles are still poorly understood. Here, we investigated the role of plasminogen in accumulations of macrophages and neutrophils after liver injury in mice with gene deficient of plasminogen (Plg^−/−) or its wild type (Plg^+/+).

Materials and Methods

Mice received traumatic liver injury caused by stabbing on the lobe or hepatic ischemia-reperfusion, and the damaged sites were histologically analyzed.

Results

After the traumatic liver injury, both the stab wound and the damaged tissue were decreased until day 7 in the Plg^+/+ mice. In contrast, both the stab wound and the damaged tissue were still remained until day 7 in the Plg^−/− mice. On day 4 after traumatic liver injury, macrophages were abundant at the surrounding area of the damaged site in the Plg^+/+ mice. However, the macrophage accumulation was impaired in the Plg^−/− mice. After hepatic ischemia-reperfusion injury, macrophage accumulation and decrease in the damaged tissue were also observed in the Plg^+/+ mice until day 7. In contrast, these responses were also impaired in the Plg^−/− mice. Furthermore, neutrophil accumulation at the surrounding area of the damaged site was also impaired in the Plg^−/− mice on day 4 after both liver traumatic liver injury and hepatic ischemia-reperfusion injury.

Conclusions

Our data indicate that plasminogen plays a crucial role in macrophage accumulation together with the neutrophil accumulation after liver injury in both models, which may be essential for triggering the subsequent healing responses including decrease in the damaged tissue.     

ERα Signaling in GHRH/Kiss1 Dual-Phenotype Neurons Plays Sex-Specific Roles in Growth and Puberty

Gonadal steroids modulate growth hormone (GH) secretion and the pubertal growth spurt via undefined central pathways. GH-releasing hormone (GHRH) neurons express estrogen receptor α (ERα) and androgen receptor (AR), suggesting changing levels of gonadal steroids during puberty directly modulate the somatotropic axis. We generated mice with deletion of ERα in GHRH cells (GHRH^ΔERα), which displayed reduced body length in both sexes. Timing of puberty onset was similar in both groups, but puberty completion was delayed in GHRH^ΔERα females. Lack of AR in GHRH cells (GHRH^ΔAR mice) induced no changes in body length, but puberty completion was also delayed in females. Using a mouse model with two reporter genes, we observed that, while GHRH^tdTom neurons minimally colocalize with Kiss1^hrGFP in prepubertal mice, ∼30% of GHRH neurons coexpressed both reporter genes in adult females, but not in males. Developmental analysis of Ghrh and Kiss1 expression suggested that a subpopulation of ERα neurons in the arcuate nucleus of female mice undergoes a shift in phenotype, from GHRH to Kiss1, during pubertal transition. Our findings demonstrate that direct actions of gonadal steroids in GHRH neurons modulate growth and puberty and indicate that GHRH/Kiss1 dual-phenotype neurons play a sex-specific role in the crosstalk between the somatotropic and gonadotropic axes during pubertal transition.SIGNIFICANCE STATEMENT Late maturing adolescents usually show delayed growth and bone age. At puberty, gonadal steroids have stimulatory effects on the activation of growth and reproductive axes, but the existence of gonadal steroid-sensitive neuronal crosstalk remains undefined. Moreover, the neural basis for the sex differences observed in the clinical arena is unknown. Lack of ERα in GHRH neurons disrupts growth in both sexes and causes pubertal delay in females. Deletion of androgen receptor in GHRH neurons only delayed female puberty. In adult females, not males, a subset of GHRH neurons shift phenotype to start producing Kiss1. Thus, direct estrogen action in GHRH/Kiss1 dual-phenotype neurons modulates growth and puberty and may orchestrate the sex differences in endocrine function observed during pubertal transition.     

Central Versus Peripheral Antagonism of Cannabinoid CB1 Receptor in Obesity: Effects of LH-21, a Peripherally Acting Neutral Cannabinoid Receptor Antagonist, in Zucker Rats

The endogenous cannabinoid system plays an important modulatory role in feeding behaviour and metabolism, acting at both central and peripheral levels. Chronic administration of cannabinoid CB₁ receptor antagonists has been found to be effective in experimental obesity. However, clinically available cannabinoid receptor antagonists are inverse agonists that can target CB₁ receptors located in both central circuits regulating appetite and motivation and in peripheral organs regulating metabolism and energy expenditure. This profile complicates understanding of cannabinoid CB₁ receptor blockade as a therapeutic strategy in obesity and metabolic disorders. This review aims to explore the relevance of both inverse agonism and peripheral cannabinoid receptor blockade on the beneficial actions of chronic cannabinoid receptor blockade, by comparing the actions of the reference antagonist/inverse agonist rimonabant and the newly designed drug LH-21. LH-21 is a triazol derivative and a neutral cannabinoid receptor antagonist; it has a poor penetration rate into the central nervous system. When given acutely it decreases food intake and enhances the anorectic actions of oleoylethanolamide, a feeding suppressant lipid that acts on peripheral sensory terminals in a similar way as rimonabant. Unlike rimonabant, chronic administration of LH-21 (3 mg/kg) reduces feeding but does not improve hypertriglyceridaemia or hypercholesterolaemia; nor does it reduce liver fat deposits in Zucker rats. These results suggest that the inverse agonism and/or the antagonism of central cannabinoid CB₁ receptors are necessary for the metabolic benefits of cannabinoid CB₁ receptor blockade, but not for the appetite reduction.     

The role of histaminergic H1 and H3 receptors in food intake: A mechanism for atypical antipsychotic-induced weight gain?

Atypical antipsychotics such as olanzapine and clozapine are effective at treating the multiple domains of schizophrenia, with a low risk of extra-pyramidal side-effects. However a major downfall to their use is metabolic side-effects particularly weight gain/obesity, which occurs by unknown mechanisms. The present paper explores the potential candidature of histaminergic neurotransmission in the mechanisms of atypical antipsychotic-induced weight gain, with a focus on the histaminergic H1 and H3 receptors. Olanzapine and clozapine have a high affinity for the H1 receptor, and meta-analyses show a strong correlation between risk of weight gain and H1 receptor affinity. In addition, olanzapine treatment decreases H1 receptor binding and mRNA expression in the rat hypothalamus. Furthermore, a complex role is emerging for the histamine H3 receptor in the control of hunger. The H3 receptor is a pre-synaptic autoreceptor that inhibits the synthesis and release of histamine, and a heteroreceptor that inhibits other neurotransmitters such as serotonin (5-HT), noradrenaline (NA) and acetylcholine (ACh), which are also implicated in the regulation of food intake. Thus, the H3 receptor is in a prime position to regulate food intake, both through its control of histamine and its influence on other feeding pathways. We proposed that a mechanism for atypical antipsychotic-induced weight gain may be partly through the H3 receptor, as a drug-induced decrease in H1 receptor activity may decrease histamine tone through the H3 autoreceptors, compounding the weight gain problem. In addition, atypical antipsychotics may affect food intake by influencing 5-HT, NA and ACh release via interactions with the H3 heteroreceptor.     

Deletion of the gene encoding MyD88 protects from anorexia in a mouse tumor model

The anorexia–cachexia syndrome, characterized by a rise in energy expenditure and loss of body weight that paradoxically are associated with loss of appetite and decreased food intake, contributes significantly to the morbidity and mortality in cancer. While the pathophysiology of cancer anorexia–cachexia is poorly understood, evidence indicates that pro-inflammatory cytokines are key mediators of this response. Although inflammation hence is recognized as an important component of cancer anorexia–cachexia, the molecular pathways involved are largely unknown. We addressed this issue in mice carrying a deletion of the gene encoding MyD88, the key intracellular adaptor molecule in Toll-like and interleukin-1 family receptor signaling. Wild-type and MyD88-deficient mice were transplanted subcutaneously with a syngenic methylcholanthrene-induced tumor (MCG 101) and daily food intake and body weight were recorded. Wild-type mice showed progressively reduced food intake from about 5 days after tumor transplantation and displayed a slight body weight loss after 10 days when the experiment was terminated. In contrast, MyD88-deficient mice did not develop anorexia, and displayed a positive body weight development during the observation period. While the MyD88-deficient mice on average developed somewhat smaller tumors than wild-type mice, this did not explain the absence of anorexia, because anorexia was seen in wild-type mice with similar tumor mass as non-anorexic knock-out mice. These data suggest that MyD88-dependent mechanisms are involved in the metabolic derangement during cancer anorexia–cachexia and that innate immune signaling is important for the development of this syndrome.     

Chemically defined projections linking the mediobasal hypothalamus and the lateral hypothalamic area

Recent studies have identified several neuropeptide systems in the hypothalamus that are critical in the regulation of body weight. The lateral hypothalamic area (LHA) has long been considered essential in regulating food intake and body weight. Two neuropeptides, melanin-concentrating hormone (MCH) and the orexins (ORX), are localized in the LHA and provide diffuse innervation of the neuraxis, including monosynaptic projections to the cerebral cortex and autonomic preganglionic neurons. Therefore, MCH and ORX neurons may regulate both cognitive and autonomic aspects of food intake and body weight regulation. The arcuate nucleus also is critical in the regulation of body weight, because it contains neurons that express leptin receptors, neuropeptide Y (NPY), α-melanin-stimulating hormone (α-MSH), and agouti-related peptide (AgRP). In this study, we examined the relationships of these peptidergic systems by using dual-label immunohistochemistry or in situ hybridization in rat, mouse, and human brains. In the normal rat, mouse, and human brain, ORX and MCH neurons make up segregated populations. In addition, we found that AgRP- and NPY-immunoreactive neurons are present in the medial division of the human arcuate nucleus, whereas α-MSH-immunoreactive neurons are found in the lateral arcuate nucleus. In humans, AgRP projections were widespread in the hypothalamus, but they were especially dense in the paraventricular nucleus and the perifornical area. Moreover, in both rat and human, MCH and ORX neurons receive innervation from NPY-, AgRP-, and α-MSH-immunoreactive fibers. Projections from populations of leptin-responsive neurons in the mediobasal hypothalamus to MCH and ORX cells in the LHA may link peripheral metabolic cues with the cortical mantle and may play a critical role in the regulation of feeding behavior and body weight. J. Comp. Neurol. 402:442–459, 1998. © 1998 Wiley-Liss, Inc.     

Hypothalamic orexin, OX1, αMSH, NPY and MCRs expression in dopaminergic D2R knockout mice

In 5-month-old male and female dopamine receptor 2 (D2R) knockout mice food intake per animal was unaltered while food per g BW was increased. We wished to evaluate the effect of D2R disruption on different components of energy balance and food intake regulation. We determined hypothalamic orexin precursor (PPO) expression, its receptor OX1, serum leptin levels, hypothalamic leptin receptor (OBR), circulating and pituitary α MSH levels, as well as central MC3 and MC4 receptors and NPY mRNA in wildtype and D2R knockout mice (KO).Loss of D2R caused a marked increase in serum prolactin levels, to higher levels in females compared to male KO mice. On the other hand, it produced a female-specific increase in circulating αMSH, and hypothalamic αMSH content, while neurointermediate αMSH content was decreased in both sexes. No differences were found in hypothalamic NPY, MC3R or MC4R concentration. Hypothalamic PPO mRNA expression was significantly decreased only in female KOs, while OX1 mRNA was not different between genotypes. Serum leptin levels were also similar in both genotypes.Our results show that in female and not in male mice disruption of the D2R produces two potentially anorexigenic events: an increase in serum and hypothalamic αMSH, and a decrease in hypothalamic orexin expression. Very high prolactin levels, which are orexigenic, probably counterbalance these effects, so that food intake is slightly altered. In males, on the other hand, hypothalamic PPO, and serum or hypothalamic αMSH are not modified, and increased prolactin levels may account for increased food intake per g BW. These results suggest a sexually dimorphic participation of the D2R in food intake regulation.     

Deletion of insulin-regulated aminopeptidase in mice decreases susceptibility to pentylenetetrazol-induced generalized seizures

The peptide angiotensin IV (Ang IV) influences seizure susceptibility in rat and mouse models. Indeed, Ang IV has been shown to protect rats from limbic seizures in the focal pilocarpine model. Moreover, both anticonvulsive and antiepileptogenic effects of Ang IV have been reported in the acute pentylenetetrazol (PTZ) and kindling model of generalized seizures in mice. It has been hypothesized that the latter effects on seizures could be established via a modulatory effect on dopamine receptors in the basal ganglia or via an indirect interaction between Ang IV and adenosine A1 receptors. However, a possible role for insulin-regulated aminopeptidase (IRAP), the high affinity binding site for Ang IV, has not been studied yet. To unequivocally unravel the involvement of IRAP in generalized seizure generation, we investigated the susceptibility of male IRAP wild-type (IRAP^+/+) and knock-out (IRAP^−/−) mice to PTZ-induced seizures. Challenging these mice intravenously with PTZ resulted in significantly increased thresholds for myoclonic twitch and generalized clonic seizures with loss of righting reflexes in IRAP^−/− mice compared to their IRAP^+/+ littermates. These behavioural data were confirmed by video-electrocorticography monitoring. Our study shows that IRAP^−/− mice are less sensitive to the development of PTZ-induced seizures and suggests that IRAP is involved in generalized seizure generation.     

Cannabinoid receptor 1 in the vagus nerve is dispensable for body weight homeostasis but required for normal gastrointestinal motility

The cannabinoid receptor 1 (CB(1)R) is required for body weight homeostasis and normal gastrointestinal motility. However, the specific cell types expressing CB(1)R that regulate these physiological functions are unknown. CB(1)R is widely expressed, including in neurons of the parasympathetic branches of the autonomic nervous system. The vagus nerve has been implicated in the regulation of several aspects of metabolism and energy balance (e.g., food intake and glucose balance), and gastrointestinal functions including motility. To directly test the relevance of CB(1)R in neurons of the vagus nerve on metabolic homeostasis and gastrointestinal motility, we generated and characterized mice lacking CB(1)R in afferent and efferent branches of the vagus nerve (Cnr1(flox/flox); Phox2b-Cre mice). On a chow or on a high-fat diet, Cnr1(flox/flox); Phox2b-Cre mice have similar body weight, food intake, energy expenditure, and glycemia compared with Cnr1(flox/flox) control mice. Also, fasting-induced hyperphagia and after acute or chronic pharmacological treatment with SR141716 [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole carboxamide] (CB(1)R inverse agonist) paradigms, mutants display normal body weight and food intake. Interestingly, Cnr1(flox/flox); Phox2b-Cre mice have increased gastrointestinal motility compared with controls. These results unveil CB(1)R in the vagus nerve as a key component underlying normal gastrointestinal motility.     

Neonatal Bisphenol A exposure alters sexually dimorphic gene expression in the postnatal rat hypothalamus

Developmental exposure to Bisphenol A (BPA), a component of polycarbonate and epoxy resins, has been purported to adversely impact reproductive function in female rodents. Because neonatal life is a critical window for the sexual dimorphic organization of the hypothalamic-pituitary-gonadal (HPG) axis, interference with this process could underlie compromised adult reproductive physiology. The goal of the present study was to determine if neonatal BPA exposure interferes with sex specific gene expression of estrogen receptor alpha (ERα), ER beta (ERβ) and kisspeptin (Kiss1) in the anterior and mediobasal hypothalamus. Long Evans (LE) neonatal rats were exposed to vehicle, 10 μg estradiol benzoate (EB), 50 mg/kg BPA or 50 μg/kg BPA by subcutaneous injection daily from postnatal day 0 (PND 0) to PND 2. Gene expression was assessed by in situ hybridization on PNDs 4 and 10. Within the anterior hypothalamus ERα expression was augmented by BPA in PND 4 females, then fell to male-typical levels by PND 10. ERβ expression was not altered by BPA on PND 4, but significantly decreased or eliminated in both sexes by PND 10. Kiss1 expression was diminished by BPA in the anterior hypothalamus, especially in females. There were no significant impacts of BPA in the mediobasal hypothalamus. Collectively, BPA effects did not mirror those of EB. The results show that neonatal hypothalamic ER and Kiss1 expression is sensitive to BPA exposure. This disruption may alter sexually dimorphic hypothalamic organization and underlie adult reproductive deficiencies. Additionally, the discordant effects of EB and BPA indicate that BPA likely disrupts hypothalamic organization by a mechanism other than simply acting as an estrogen mimic.     

Intact brown adipose tissue thermogenesis is required for restorative sleep responses after sleep loss

Metabolic signals related to feeding and body temperature regulation have profound effects on vigilance. Brown adipose tissue (BAT) is a key effector organ in the regulation of metabolism in several species, including rats and mice. Significant amounts of active BAT are also present throughout adulthood in humans. The metabolic activity of BAT is due to the tissue‐specific presence of the uncoupling protein‐1 (UCP‐1). To test the involvement of BAT thermogenesis in sleep regulation, we investigated the effects of two sleep‐promoting stimuli in UCP‐1‐deficient mice. Sleep deprivation by gentle handling increased UCP‐1 mRNA expression in BAT and elicited rebound increases in non‐rapid‐eye‐movement sleep and rapid‐eye‐movement sleep accompanied by elevated slow‐wave activity of the electroencephalogram. The rebound sleep increases were significantly attenuated, by ~ 35–45%, in UCP‐1‐knockout (KO) mice. Wild‐type (WT) mice with capsaicin‐induced sensory denervation of the interscapular BAT pads showed similar impairments in restorative sleep responses after sleep deprivation, suggesting a role of neuronal sleep‐promoting signaling from the BAT. Exposure of WT mice to 35 °C ambient temperature for 5 days led to increased sleep and body temperature and suppressed feeding and energy expenditure. Sleep increases in the warm environment were significantly suppressed, by ~ 50%, in UCP‐1‐KO animals while their food intake and energy expenditure did not differ from those of the WTs. These results suggest that the metabolic activity of the BAT plays a role in generating a metabolic environment that is permissive for optimal sleep. Impaired BAT function may be a common underlying cause of sleep insufficiency and metabolic disorders.