d-Allulose Inhibits Ghrelin-Responsive, Glucose-Sensitive and Neuropeptide Y Neurons in the Arcuate Nucleus and Central Injection Suppresses Appetite-Associated Food Intake in Mice.

d-allulose, a rare sugar, has sweetness with few calories. d-allulose regulates feeding and glycemia, and ameliorates hyperphagia, obesity and diabetes. All these functions involve the central nervous system. However, central mechanisms underlying these effects of d-allulose remain unknown. We recently reported that d-allulose activates the anorexigenic neurons in the hypothalamic arcuate nucleus (ARC), the neurons that respond to glucagon-like peptide-1 and that express proopiomelanocortin. However, its action on the orexigenic neurons remains unknown. This study investigated the effects of d-allulose on the ARC neurons implicated in hunger, by measuring cytosolic Ca2+ concentration ([Ca2+]i) in single neurons. d-allulose depressed the increases in [Ca2+]i induced by ghrelin and by low glucose in ARC neurons and inhibited spontaneous oscillatory [Ca2+]i increases in neuropeptide Y (NPY) neurons. d-allulose inhibited 10 of 35 (28%) ghrelin-responsive, 18 of 60 (30%) glucose-sensitive and 3 of 8 (37.5%) NPY neurons in ARC. Intracerebroventricular injection of d-allulose inhibited food intake at 20:00 and 22:00, the early dark phase when hunger is promoted. These results indicate that d-allulose suppresses hunger-associated feeding and inhibits hunger-promoting neurons in ARC. These central actions of d-allulose represent the potential of d-allulose to inhibit the hyperphagia with excessive appetite, thereby counteracting obesity and diabetes.

The Orexigenic Force of Olfactory Palatable Food Cues in Rats.

Environmental cues recalling palatable foods motivate eating beyond metabolic need, yet the timing of this response and whether it can develop towards a less palatable but readily available food remain elusive. Increasing evidence indicates that external stimuli in the olfactory modality communicate with the major hub in the feeding neurocircuitry, namely the hypothalamic arcuate nucleus (Arc), but the neural substrates involved have been only partially uncovered. By means of a home-cage hidden palatable food paradigm, aiming to mimic ubiquitous exposure to olfactory food cues in Western societies, we investigated whether the latter could drive the overeating of plain chow in non-food-deprived male rats and explored the neural mechanisms involved, including the possible engagement of the orexigenic ghrelin system. The olfactory detection of a familiar, palatable food impacted upon meal patterns, by increasing meal frequency, to cause the persistent overconsumption of chow. In line with the orexigenic response observed, sensing the palatable food in the environment stimulated food-seeking and risk-taking behavior, which are intrinsic components of food acquisition, and caused active ghrelin release. Our results suggest that olfactory food cues recruited intermingled populations of cells embedded within the feeding circuitry within the Arc, including, notably, those containing the ghrelin receptor. These data demonstrate the leverage of ubiquitous food cues, not only for palatable food searching, but also to powerfully drive food consumption in ways that resonate with heightened hunger, for which the orexigenic ghrelin system is implicated.

Recording cortico-cortical evoked potentials of the human arcuate fasciculus under general anaesthesia.

OBJECTIVE: We examined the feasibility of using cortico-cortical evoked potentials (CCEPs) to monitor the major cortical white matter tract involved in language, the arcuate fasciculus (AF), during surgery under general anaesthesia. METHODS: We prospectively recruited nine patients undergoing surgery for lesions in the left peri-sylvian cortex, for whom awake surgery was not indicated. High angular resolution diffusion imaging (HARDI) tractography was used to localise frontal and temporal AF terminations, which guided intraoperative cortical strip placement. RESULTS: CCEPs were successfully evoked in 5/9 patients, showing a positive potential (P1) at 12 ms and a negative component (N1) at 21 ms when stimulating from the frontal lobe and recording in the temporal lobe. CCEP responses peaked in the posterior middle temporal gyrus. No CCEPs were evoked when stimulating temporal sites and recording from frontal contacts. CONCLUSION: For the first time, we show that CCEPs can be evoked from the peri-sylvian cortices also in adult patients who are not candidates for awake procedures. Our results are akin to those described in the awake setting and suggest the recorded activity is conveyed by the arcuate fasciculus. SIGNIFICANCE: This intraoperative approach may have promising implications in reducing deficits in patients that require surgery in language areas under general anesthesia.

Pituitary Adenylate Cyclase-Activating Polypeptide Excites Proopiomelanocortin Neurons: Implications for the Regulation of Energy Homeostasis.

OBJECTIVE: We examined whether pituitary adenylate cyclase-activating polypeptide (PACAP) excites proopiomelanocortin (POMC) neurons via PAC1 receptor mediation and transient receptor potential cation (TRPC) channel activation. METHODS: Electrophysiological recordings were done in slices from both intact male and ovariectomized (OVX) female PACAP-Cre mice and eGFP-POMC mice. RESULTS: In recordings from POMC neurons in eGFP-POMC mice, PACAP induced a robust inward current and increase in conductance in voltage clamp, and a depolarization and increase in firing in current clamp. These postsynaptic actions were abolished by inhibitors of the PAC1 receptor, TRPC channels, phospholipase C, phosphatidylinositol-3-kinase, and protein kinase C. Estradiol augmented the PACAP-induced inward current, depolarization, and increased firing, which was abrogated by estrogen receptor (ER) antagonists. In optogenetic recordings from POMC neurons in PACAP-Cre mice, high-frequency photostimulation induced inward currents, depolarizations, and increased firing that were significantly enhanced by Gq-coupled membrane ER signaling in an ER antagonist-sensitive manner. Importantly, the PACAP-induced excitation of POMC neurons was notably reduced in obese, high-fat (HFD)-fed males. In vivo experiments revealed that intra-arcuate nucleus (ARC) PACAP as well as chemogenetic and optogenetic stimulation of ventromedial nucleus (VMN) PACAP neurons produced a significant decrease in energy intake accompanied by an increase in energy expenditure, effects blunted by HFD in males and partially potentiated by estradiol in OVX females. CONCLUSIONS: These findings reveal that the PACAP-induced activation of PAC1 receptor and TRPC5 channels at VMN PACAP/ARC POMC synapses is potentiated by estradiol and attenuated under conditions of diet-induced obesity/insulin resistance. As such, they advance our understanding of how PACAP regulates the homeostatic energy balance circuitry under normal and pathophysiological circumstances.

The anorexigenic effect of vasoactive intestinal polypeptide in Japanese quail is associated with molecular changes in the arcuate and dorsomedial hypothalamic nuclei.

Vasoactive intestinal polypeptide (VIP) is involved in gastric smooth muscle relaxation, vasodilation, and gastric secretions. It is also associated with appetite regulation, eliciting an anorexigenic response in mammals, birds, and fish; however, the molecular mechanism mediating this response is not well understood. The aim of the present study was thus to investigate hypothalamic mechanisms mediating VIP-induced satiety in 7-d old Japanese quail. In experiment 1, chicks that received intracerebroventricular (ICV) injection of VIP had reduced food intake for up to 180 min after injection and reduced water intake for 90 min. In experiment 2, VIP-treated chicks that were food restricted did not reduce water intake. In experiment 3, there was increased c-Fos immunoreactivity in the arcuate (ARC) and dorsomedial (DMN) nuclei of the hypothalamus in VIP-injected quail. In experiment 4, ICV VIP was associated with decreased neuropeptide Y mRNA in the ARC and DMN and an increase in corticotropin releasing factor mRNA in the DMN. In experiment 5, VIP-treated chicks displayed fewer feed pecks and locomotor behaviors. These results demonstrate that central VIP causes anorexigenic effects that are likely associated with reductions in orexigenic tone involving the ARC and DMN.

Activation of the ARCPOMC→MeA Projection Reduces Food Intake.

Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) plays an essential role in the control of food intake and energy expenditure. Melanocortin-4 receptors (MC4Rs) are expressed in key areas that are implicated in regulating energy homeostasis. Although the importance of MC4Rs in the paraventricular hypothalamus (PVH) has been well documented, the role of MC4Rs in the medial amygdala (MeA) on feeding remains controversial. In this study, we specifically examine the role of a novel ARCPOMC→MeA neural circuit in the regulation of short-term food intake. To map a local melanocortinergic neural circuit, we use monosynaptic anterograde as well as retrograde viral tracers and perform double immunohistochemistry to determine the identity of the neurons receiving synaptic input from POMC neurons in the ARC. To investigate the role of the ARCPOMC→MeA projection on feeding, we optogenetically stimulate channelrhodopsin-2 (ChR2)-expressing POMC fibers in the MeA. Anterograde viral tracing studies reveal that ARC POMC neurons send axonal projections to estrogen receptor-α (ER-α)- and MC4R-expressing neurons in the MeA. Retrograde viral tracing experiments show that the neurons projecting to the MeA is located mainly in the lateral part of the ARC. Optogenetic stimulation of the ARCPOMC→MeA pathway reduces short-term food intake. This anorectic effect is blocked by treatment with the MC4R antagonist SHU9119. In addition to the melanocortinergic local circuits within the hypothalamus, this extrahypothalamic ARCPOMC→MeA neural circuit would play a role in regulating short-term food intake.

Ultradian Rhythms in the Hypothalamic Arcuate Nucleus Kisspeptin Neurons and Developmental Processes.

Numerous physiological processes in nature have multiple oscillations within 24 h, that is, ultradian rhythms. Compared to the circadian rhythm, which has a period of approximately one day, these short oscillations range from seconds to hours, and the mechanisms underlying ultradian rhythms remain largely unknown. This review aims to explore and emphasize the implications of ultradian rhythms and their underlying regulations. Reproduction and developmental processes show ultradian rhythms, and these physiological systems can be regulated by short biological rhythms. Specifically, we recently uncovered synchronized calcium oscillations in the organotypic culture of hypothalamic arcuate nucleus (ARN) kisspeptin neurons that regulate reproduction. Synchronized calcium oscillations were dependent on voltage-gated ion channel-mediated action potentials and were repressed by chemogenetic inhibition, suggesting that the network within the ARN and between the kisspeptin population mediates the oscillation. This minireview describes that ultradian rhythms are a general theme that underlies biological features, with special reference to calcium oscillations in the hypothalamic ARN from a developmental perspective. We expect that more attention to these oscillations might provide insight into physiological or developmental mechanisms, since many oscillatory features in nature still remain to be explored.

MCH Neurons Regulate Permeability of the Median Eminence Barrier.

Melanin-concentrating hormone (MCH)-expressing neurons are key regulators of energy and glucose homeostasis. Here, we demonstrate that they provide dense projections to the median eminence (ME) in close proximity to tanycytes and fenestrated vessels. Chemogenetic activation of MCH neurons as well as optogenetic stimulation of their projections in the ME enhance permeability of the ME by increasing fenestrated vascular loops and enhance leptin action in the arcuate nucleus of the hypothalamus (ARC). Unbiased phosphoRiboTrap-based assessment of cell activation upon chemogenetic MCH neuron activation reveals MCH-neuron-dependent regulation of endothelial cells. MCH neurons express the vascular endothelial growth factor A (VEGFA), and blocking VEGF-R signaling attenuates the leptin-sensitizing effect of MCH neuron activation. Our experiments reveal that MCH neurons directly regulate permeability of the ME barrier, linking the activity of energy state and sleep regulatory neurons to the regulation of hormone accessibility to the ARC.

Oxyntomodulin induces satiety and activates the arcuate nucleus of the hypothalamus in Japanese quail.

Oxyntomodulin (OXM) is a proglucagon-derived peptide that suppresses hunger in humans. There are some differences in its food intake-inhibitory effects among species. The central mechanisms are unclear and it is unknown if OXM is more efficacious in a gallinaceous species that has not undergone as much selection for growth as the chicken. The objective was thus to determine the effects of OXM on food and water intake and hypothalamic physiology in Japanese quail. At 7 days post-hatch, 6-h-fasted quail were injected intracerebroventricularly (ICV) or intraperitoneally (IP) with 0.32, 0.65, or 1.3 nmol of OXM. All doses decreased food intake for 180 min post-ICV injection. On a cumulative basis, water intake was not affected until 120 min, with the lowest and highest doses decreasing water intake after ICV injection. The two highest doses were anorexigenic when administered via the IP route, whereas all doses were anti-dipsogenic starting at 30 min post-injection. In hypothalamic samples collected at 1-h post-ICV injection, there was an increase in c-Fos immunoreactivity, an indicator of recent neuronal activation, in the arcuate nucleus (ARC) and dorsomedial nucleus (DMN) of the hypothalamus in OXM-injected individuals. Results suggest that quail are more sensitive than chickens to the satiety-inducing effects of OXM. The central mechanism is likely mediated through a pathway in the ARC that is conserved among species, and through activation of the DMN, an effect that is unique to quail. Such knowledge is critical for facilitating the development of novel, side effect-free anti-eating strategies to promote weight-loss in obesity.

PNOCARC Neurons Promote Hyperphagia and Obesity upon High-Fat-Diet Feeding.

Calorie-rich diets induce hyperphagia and promote obesity, although the underlying mechanisms remain poorly defined. We find that short-term high-fat-diet (HFD) feeding of mice activates prepronociceptin (PNOC)-expressing neurons in the arcuate nucleus of the hypothalamus (ARC). PNOCARC neurons represent a previously unrecognized GABAergic population of ARC neurons distinct from well-defined feeding regulatory AgRP or POMC neurons. PNOCARC neurons arborize densely in the ARC and provide inhibitory synaptic input to nearby anorexigenic POMC neurons. Optogenetic activation of PNOCARC neurons in the ARC and their projections to the bed nucleus of the stria terminalis promotes feeding. Selective ablation of these cells promotes the activation of POMC neurons upon HFD exposure, reduces feeding, and protects from obesity, but it does not affect food intake or body weight under normal chow consumption. We characterize PNOCARC neurons as a novel ARC neuron population activated upon palatable food consumption to promote hyperphagia.

Kisspeptin Neuron-Specific and Self-Sustained Calcium Oscillation in the Hypothalamic Arcuate Nucleus of Neonatal Mice: Regulatory Factors of its Synchronization.

INTRODUCTION: Synchronous and pulsatile neural activation of kisspeptin neurons in the arcuate nucleus (ARN) are important components of the gonadotropin-releasing hormone pulse generator, the final common pathway for central regulation of mammalian reproduction. However, whether ARN kisspeptin neurons can intrinsically generate self-sustained synchronous oscillations from the early neonatal period and how they are regulated remain unclear. OBJECTIVE: This study aimed to examine the endogenous rhythmicity of ARN kisspeptin neurons and its neural regulation using a neonatal organotypic slice culture model. METHODS: We monitored calcium (Ca2+) dynamics in real-time from individual ARN kisspeptin neurons in neonatal organotypic explant cultures of Kiss1-IRES-Cre mice transduced with genetically encoded Ca2+ indicators. Pharmacological approaches were employed to determine the regulations of kisspeptin neuron-specific Ca2+ oscillations. A chemogenetic approach was utilized to assess the contribution of ARN kisspeptin neurons to the population dynamics. RESULTS: ARN kisspeptin neurons in neonatal organotypic cultures exhibited a robust synchronized Ca2+ oscillation with a period of approximately 3 min. Kisspeptin neuron-specific Ca2+ oscillations were dependent on voltage-gated sodium channels and regulated by endoplasmic reticulum-dependent Ca2+ homeostasis. Chemogenetic inhibition of kisspeptin neurons abolished synchronous Ca2+ oscillations, but the autocrine actions of the neuropeptides were marginally effective. Finally, neonatal ARN kisspeptin neurons were regulated by N-methyl-D-aspartate and gamma-aminobutyric acid receptor-mediated neurotransmission. CONCLUSION: These data demonstrate that ARN kisspeptin neurons in organotypic cultures can generate synchronized and self-sustained Ca2+ oscillations. These oscillations controlled by multiple regulators within the ARN are a novel ultradian rhythm generator that is active during the early neonatal period.

17ß-Estradiol Increases Arcuate KNDy Neuronal Sensitivity to Ghrelin Inhibition of the M-Current in Female Mice.

Obesity and anorexia result in dysregulation of the hypothalamic-pituitary-gonadal axis, negatively impacting reproduction. Ghrelin, secreted from the stomach, potentially mediates negative energy states and neuroendocrine control of reproduction by acting through the growth hormone secretagogue receptor (GHSR). GHSR is expressed in hypothalamic arcuate (ARC) Kisspeptin/Neurokinin B (Tac2)/Dynorphin (KNDy) neurons. Ghrelin is known to inhibit the M-current produced by KCNQ channels in other ARC neurons. In addition, we have shown 17ß-estradiol (E2) increases Ghsr expression in KNDy neurons 6-fold and increases the M-current in NPY neurons. We hypothesize that E2 increases GHSR expression in KNDy neurons to increase ghrelin sensitivity during negative energy states. Furthermore, we suspect ghrelin targets the M-current in KNDy neurons to control reproduction and energy homeostasis. We utilized ovariectomized Tac2-EGFP adult female mice, pretreated with estradiol benzoate (EB) or oil vehicle and performed whole-cell-patch-clamp recordings to elicit the M-current in KNDy neurons using standard activation protocols in voltage-clamp. Using the selective KCNQ channel blocker XE-991 (40 µM) to target the M-current, oil- and EB-treated mice showed a decrease in the maximum peak current by 75.7 ± 13.8 pA (n = 10) and 68.0 ± 14.7 pA (n = 11), respectively. To determine the actions of ghrelin on the M-current, ghrelin was perfused (100 nM) in oil- and EB-treated mice resulting in the suppression of the maximum peak current by 58.5 ± 15.8 pA (n = 9) and 59.2 ± 11.9 pA (n = 9), respectively. KNDy neurons appeared more sensitive to ghrelin when pretreated with EB, revealing that ARC KNDy neurons are more sensitive to ghrelin during states of high E2.

Should We Make More Bone or Not, As Told by Kisspeptin Neurons in the Arcuate Nucleus.

Since its initial discovery in 2002, the neuropeptide Kisspeptin (Kiss1) has been anointed as the master regulator controlling the onset of puberty in males and females. Over the last several years, multiple groups found that Kiss1 signaling is mediated by the 7TM surface receptor GPCR54. Kiss1 mRNA is highly enriched in the basal medial and lateral subregions of the arcuate nucleus (ARC) in the medial basal hypothalamus. Thus, Kiss1ARC neurons reside in a unique anatomical location ideal for sensing and responding to circulating steroid hormones as well as nutrients. Kiss1 expression is highly responsive to fluctuations of the gonadal hormone, estrogen, with nearly 90% of Kiss1ARC neurons expressing the nuclear hormone estrogen receptor alpha (ERa). Here we review recent research that extends the function of Kiss1ARC neurons beyond the regulation of puberty and highlight their emerging, novel roles in controlling energy allocation, behavioral outputs, and sex-dependent bone remodeling in females. Indeed, some of these previously unknown functions for Kiss1 neurons are quite striking as exemplified by the remarkable increase in bone mass after manipulating estrogen signaling in Kiss1ARC neurons. Taken together, we suggest that Kiss1ARC neurons are highly sensitive to nutritional and hormonal cues that dictate energy utilization and reproduction.

Insulin-induced hypoglycaemia suppresses pulsatile luteinising hormone secretion and arcuate Kiss1 cell activation in female mice.

Stress suppresses pulsatile luteinising hormone (LH) secretion in a variety of species, although the mechanism underlying this inhibition of reproductive function remains unclear. Metabolic stress, particularly hypoglycaemia, is a clinically-relevant stress type that is modelled with bolus insulin injection (insulin-induced hypoglycaemia). The present study utilised ovariectomised C57BL/6 mice to test the hypothesis that acute hypoglycaemia suppresses pulsatile LH secretion via central mechanisms. Pulsatile LH secretion was measured in 90-minute sampling periods immediately prior to and following i.p. injection of saline or insulin. The secretion of LH was not altered over time in fed animals or acutely fasted (5 hours) animals following an i.p. saline injection. By contrast, insulin elicited a robust suppression of pulsatile LH secretion in fasted animals, preventing LH pulses in five of six mice. To identify the neuroendocrine site of impairment, a kisspeptin challenge was performed in saline or insulin pre-treated animals in a cross-over design. LH secretion in response to exogenous kisspeptin was not different between animals pre-treated with saline or insulin, indicating normal gonadotrophin-releasing hormone cell and pituitary responses during acute hypoglycaemia. Based on this finding, the effect of insulin-induced hypoglycaemia on arcuate kisspeptin (Kiss1) cell function was determined using c-Fos as a marker of neuronal activation. Insulin caused a significant suppression in the percentage of Kiss1 cells in the arcuate nucleus that contained c-Fos compared to saline-injected controls. Taken together, these data support the hypothesis that insulin-induced hypoglycaemia suppresses pulsatile LH secretion in the female mouse via predominantly central mechanisms, which culminates in the suppression of the arcuate Kiss1 population.

Role of kisspeptin neurons as a GnRH surge generator: Comparative aspects in rodents and non-rodent mammals.

Ovulation is an essential phenomenon for reproduction in mammalian females along with follicular growth. It is well established that gonadal function is controlled by the neuroendocrine system called the hypothalamus-pituitary-gonadal (HPG) axis. Gonadotropin-releasing hormone (GnRH) neurons, localized in the hypothalamus, had been considered to be the head in governing the HPG axis for a long time until the discovery of kisspeptin. In females, induction of ovulation and folliculogenesis has been linked to a surge mode and pulse mode of GnRH releases, respectively. The mechanisms of how the two modes of GnRH are differently regulated had long remained elusive. The discovery of kisspeptin neurons, distributed in two hypothalamic nuclei, such as the arcuate nucleus in the caudal hypothalamus and preoptic area or the anteroventral periventricular nucleus in the rostral hypothalamic regions, and analyses of the detailed functions of kisspeptin neurons have led marked progress on the understanding of different mechanisms regulating GnRH surges (ovulation) and GnRH pulses (folliculogenesis). The present review will focus on the role of kisspeptin neurons as the GnRH surge generator, including the sexual differentiation of the surge generation system and factors that regulate the surge generator. Comparative aspects between mammalian species are especially focused on.

The neurobiological mechanism underlying hypothalamic GnRH pulse generation: the role of kisspeptin neurons in the arcuate nucleus.

This review recounts the origins and development of the concept of the hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator. It starts in the late 1960s when striking rhythmic episodes of luteinizing hormone secretion, as reflected by circulating concentrations of this gonadotropin, were first observed in monkeys and ends in the present day. It is currently an exciting time witnessing the application, primarily to the mouse, of contemporary neurobiological approaches to delineate the mechanisms whereby Kiss1/NKB/Dyn (KNDy) neurons in the arcuate nucleus of the hypothalamus generate and time the pulsatile output of kisspeptin from their terminals in the median eminence that in turn dictates intermittent GnRH release and entry of this decapeptide into the primary plexus of the hypophysial portal circulation. The review concludes with an examination of questions that remain to be addressed.

Kisspeptin Neurons in the Arcuate Nucleus of the Hypothalamus Orchestrate Circadian Rhythms and Metabolism.

Successful reproduction in female mammals is precisely timed and must be able to withstand the metabolic demand of pregnancy and lactation. We show that kisspeptin-expressing neurons in the arcuate hypothalamus (Kiss1ARH) of female mice control the daily timing of food intake, along with the circadian regulation of locomotor activity, sleep, and core body temperature. Toxin-induced silencing of Kiss1ARH neurons shifts wakefulness and food consumption to the light phase and induces weight gain. Toxin-silenced mice are less physically active and have attenuated temperature rhythms. Because the rhythm of the master clock in the suprachiasmatic nucleus (SCN) appears to be intact, we hypothesize that Kiss1ARH neurons signal to neurons downstream of the master clock to modulate the output of the SCN. We conclude that, in addition to their well-established role in regulating fertility, Kiss1ARH neurons are a critical component of the hypothalamic circadian oscillator network that times overt rhythms of physiology and behavior.

Nociceptin/orphanin FQ modulates energy homeostasis through inhibition of neurotransmission at VMN SF-1/ARC POMC synapses in a sex- and diet-dependent manner.

BACKGROUND: Orphanin FQ (aka nociceptin; N/OFQ) binds to its nociceptin opioid peptide (NOP) receptor expressed in proopiomelanocortin (POMC) neurons within the arcuate nucleus (ARC), a critical anorexigenic component of the hypothalamic energy balance circuitry. It inhibits POMC neurons by modifying neuronal excitability both pre- and postsynaptically. We tested the hypothesis that N/OFQ inhibits neurotransmission at synapses involving steroidogenic factor (SF)-1 neurons in the ventromedial nucleus (VMN) and ARC POMC neurons in a sex- and diet-dependent fashion. METHODS: Electrophysiological recordings were done in intact male and in cycling and ovariectomized female NR5A1-Cre and eGFP-POMC mice. Energy homeostasis was assessed in wildtype animals following intra-ARC injections of N/OFQ or its saline vehicle. RESULTS: N/OFQ (1 µM) decreased light-evoked excitatory postsynaptic current (leEPSC) amplitude more so in males than in diestrus or proestrus females, which was further accentuated in high-fat diet (HFD)-fed males. N/OFQ elicited a more robust outward current and increase in conductance in males than in diestrus, proestrus, and estrus females. These pleiotropic actions of N/OFQ were abrogated by the NOP receptor antagonist BAN ORL-24 (10 µM). In ovariectomized female eGFP-POMC mice, 17ß-estradiol (E2; 100 nM) attenuated the N/OFQ-induced postsynaptic response. SF-1 neurons from NR5A1-Cre mice also displayed a robust N/OFQ-induced outward current and increase in conductance that was sexually differentiated and suppressed by E2. Finally, intra-ARC injections of N/OFQ increased energy intake and decreased energy expenditure, which was further potentiated by exposure to HFD and diminished by estradiol benzoate (20 µg/kg; s.c.). CONCLUSION: These findings show that males are more responsive to the pleiotropic actions of N/OFQ at anorexigenic VMN SF-1/ARC POMC synapses, and this responsiveness can be further enhanced under conditions of diet-induced obesity/insulin resistance.

Estrogen signaling in arcuate Kiss1 neurons suppresses a sex-dependent female circuit promoting dense strong bones.

Central estrogen signaling coordinates energy expenditure, reproduction, and in concert with peripheral estrogen impacts skeletal homeostasis in females. Here, we ablate estrogen receptor alpha (ERα) in the medial basal hypothalamus and find a robust bone phenotype only in female mice that results in exceptionally strong trabecular and cortical bones, whose density surpasses other reported mouse models. Stereotaxic guided deletion of ERα in the arcuate nucleus increases bone mass in intact and ovariectomized females, confirming the central role of estrogen signaling in this sex-dependent bone phenotype. Loss of ERα in kisspeptin (Kiss1)-expressing cells is sufficient to recapitulate the bone phenotype, identifying Kiss1 neurons as a critical node in this powerful neuroskeletal circuit. We propose that this newly-identified female brain-to-bone pathway exists as a homeostatic regulator diverting calcium and energy stores from bone building when energetic demands are high. Our work reveals a previously unknown target for treatment of age-related bone disease.

Exposure of pregnant mice to triclosan causes hyperphagic obesity of offspring via the hypermethylation of proopiomelanocortin promoter.

Triclosan (TCS), as a broad spectrum antibacterial agent, is commonly utilized in personal care and household products. Maternal urinary TCS level has been associated with changes in birth weight of infants. We in the present study investigated whether exposure of mice to 8 mg/kg TCS from gestational day (GD) 6 to GD14 alters prenatal and postnatal growth and development, and metabolic phenotypes in male and female offspring (TCS-offspring). Compared with control offspring, body weight in postnatal day (PND) 1 male or female TCS-offspring was reduced, but body weight gain was faster within postnatal 5 days. PND30 and PND60 TCS-offspring showed overweight with increases in visceral fat and adipocyte size. PND60 TCS-offspring displayed delayed glucose clearance and insulin resistance. PND30 TCS-offspring showed an increase in food intake without the changes in the oxygen consumption and respiratory exchange ratio (RER). The expression levels of proopiomelanocortin (POMC), α-melanocyte-stimulating hormone (α-MSH) and single-minded 1 (SIM1) in hypothalamus arcuate nucleus (ARC) and paraventricular nucleus (PVN), respectively, were significantly reduced in PND30 TCS-offspring compared to controls. The hypermethylation of CpG sites at the POMC promoter was observed in PND30 TCS-offspring, while the concentration of serum leptin was elevated and the level of STAT3 phosphorylation in ARC had no significant difference from control. This study demonstrates that TCS exposure during early/mid-gestation through the hypermethylation of the POMC promoter reduces the expression of anorexigenic neuropeptides to cause the postnatal hyperphagic obesity, leading to metabolic syndrome in adulthood.