Arcuate Nucleus Of The Hypothalamus Research Articles

Electrophysiological Comparison of Definitive Pro-opiomelanocortin Neurons in the Arcuate Nucleus and the Retrochiasmatic Area of Male and Female Mice.

Pro-opiomelanocortin (POMC)-expressing neurons in the arcuate nucleus of the hypothalamus (ARC) are considered a major site of leptin action. Due to increasing evidence that POMC neurons are highly heterogeneous and indications that the conventional molecular tools to study their functions have important limitations, a reassessment of leptin's effects on definitive POMC neurons is needed. POMC neurons are also expressed in the retrochiasmatic area (RCA), where their function is poorly understood. Furthermore, the response of POMC neurons to leptin in females is largely unknown. Therefore, the present study aimed to determine the differences in leptin responsiveness of POMC neurons in the ARC and the RCA using a mouse model allowing adult-inducible fluorescent labeling. We performed whole-cell patch clamp electrophysiology on 154 POMC neurons from male and female mice. We confirmed and extended the model by which leptin depolarizes POMC neurons, in both the ARC and the RCA. Furthermore, we characterized the electrophysiological properties of an underappreciated subpopulation representing ∼10% of hypothalamic POMC neurons that are inhibited by leptin. We also provide evidence that sex does not appear to be a major determinant of basal properties and leptin responsiveness of POMC neurons, but that females are overall less responsive to leptin compared to males.

Metabolic, neuroendocrine and behavioral effects of social defeat in male and female mice using the chronic non-discriminatory social defeat stress model

Stress-related disorders predominately affect females, yet preclinical models of chronic stress exclusively use males especially in models where social stressors are studied. Here, we implemented a 21-day novel social defeat paradigm in which a female and male C57 intruder are simultaneously placed in the cage of a territorial, resident CD-1 male mouse, and the resident proceeds to attack both intruders. Mice were given access to a regular laboratory diet, high in carbohydrates, and a palatable diet, high in fat. Chronic social defeat stress using this paradigm resulted in increased caloric intake in male and female mice, with the effects being more pronounced in females. We observed sex differences in high fat diet intake in response to stress, which was correlated with higher levels of plasma ghrelin observed in female mice but not male mice. Furthermore, females exposed to chronic stress displayed changes in growth hormone secretatogue receptor (ghsr) and neuropeptide-y (npy) expression in the arcuate nucleus of the hypothalamus, potentially increasing ghrelin sensitivity and inducing changes in diet choice and caloric intake. Behavioral results show that females tended to spend more time interacting during the social interaction test, compared to males who displayed higher vigilance towards the stranger mouse. Overall, our results highlight unique neurometabolic alterations in female mice in response to stress that is not present in male mice and may be important for coping with chronic stress and sustaining reproductive function.

Dietary wheat gluten induces astro- and microgliosis in the hypothalamus of male mice.

Gluten, which is found in cereals such as wheat, rye and barley, makes up a major dietary component in most western nations, and has been shown to promote body mass gain and peripheral inflammation in mice. In the current study, we investigated the impact of gluten on central inflammation that is typically associated with diet-induced obesity. While we found no effect of gluten when added to a low-fat diet (LFD), male mice fed high fat diet (HFD) enriched with gluten increased body mass and adiposity compared with mice fed HFD without gluten. We furthermore found that gluten, when added to the LFD, increases circulating C-reactive protein levels. Gluten regardless of whether it was added to LFD or HFD led to a profound increase in the number of microglia and astrocytes in the arcuate nucleus of the hypothalamus, as detected by immunohistochemistry for ionised calcium binding adaptor molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP), respectively. In mice fed LFD, gluten mimicked the immunogenic effects of HFD exposure and when added to HFD led to a further increase in the number of immunoreactive cells. Taken together, our results confirm a moderate obesogenic effect of gluten when fed to mice exposed to HFD and for the first-time report gluten-induced astro- and microgliosis suggesting the development of hypothalamic injury in rodents.

Electroacupuncture for weight loss by regulating microglial polarization in the arcuate nucleus of the hypothalamus

Electroacupuncture (EA) has a weight loss effect, but the underlying molecular mechanisms of weight loss with EA have not been fully elucidated. This study aimed to investigate the modulatory effects of EA on the phenotype of hypothalamic microglia in obese mice. A total of 50 male C57BL/6J mice were used in this study. There were three groups in this experiment: The conventional diet group (Chow group), the high-fat diet group (HFD group), and the EA intervention group (HFD + EA group). EA was applied at “Tianshu (ST25)”, “Guanyuan (RN4)”, “Zusanli (ST36)” and “Zhongwan (RN12)” every day for 10 min. Hematoxylin and eosin (H&E) staining, immunohistochemical staining, and real-time PCR were applied in this study. The results showed that EA intervention was associated with a decrease in body weight, food intake, adipose tissue weight, and adipocyte size. At the same time, EA induced microglia to exhibit an M2 phenotype, representing reduced iNOS/TNF-α and increased Arg-1/IL-10/BDNF, which may be due to the promotion of TREM2 expression. EA also reduced microglia enrichment in the hypothalamic arcuate nucleus and declined TLR4 and IL-6, inhibiting microglia-mediated neuroinflammation. In addition, EA treatment promoted POMC expression, which may be associated with reduced food intake and weight loss in obese mice. This work provides novel evidence of EA against obesity. However, further study is necessary of EA as a therapy for obesity.

Mitochondria-derived peptide SHLP2 regulates energy homeostasis through the activation of hypothalamic neurons

Small humanin-like peptide 2 (SHLP2) is a mitochondrial-derived peptide implicated in several biological processes such as aging and oxidative stress. However, its functional role in the regulation of energy homeostasis remains unclear, and its corresponding receptor is not identified. Hereby, we demonstrate that both systemic and intracerebroventricular (ICV) administrations of SHLP2 protected the male mice from high-fat diet (HFD)-induced obesity and improved insulin sensitivity. In addition, the activation of pro-opiomelanocortin (POMC) neurons by SHLP2 in the arcuate nucleus of the hypothalamus (ARC) is involved in the suppression of food intake and the promotion of thermogenesis. Through high-throughput structural complementation screening, we discovered that SHLP2 binds to and activates chemokine receptor 7 (CXCR7). Taken together, our study not only reveals the therapeutic potential of SHLP2 in metabolic disorders but also provides important mechanistic insights into how it exerts its effects on energy homeostasis.

Potential for NPY receptor-related therapies for polycystic ovary syndrome: an updated review.

Polycystic ovary syndrome (PCOS) is a complex endocrine disease that can cause female infertility and bring economic burden to families and to society. The clinical and/or biochemical manifestations include hyperandrogenism, persistent anovulation, and polycystic ovarian changes, often accompanied by insulin resistance and obesity. Although its pathogenesis is unclear, PCOS involves the abnormal regulation of the hypothalamic-pituitary-ovarian axis and the abnormal activation of GnRH neurons. Neuropeptide Y (NPY) is widely distributed in the arcuate nucleus of the hypothalamus and functions as the physiological integrator of two neuroendocrine systems, one governing feeding and the other controlling reproduction. In recent years, an increasing number of studies have focused on the improvement of the reproductive and metabolic status of PCOS through the therapeutic application of NPY and its receptors.In this review, we summarize the central and peripheral regulation of NPY and its receptors in the development of PCOS and discuss the potential for NPY receptor-related therapies for PCOS.

1523-P: A Leptin-Mediated Interoceptive Network between the Brain and Brown Adipose Tissue

Obesity is attributed to chronic disruption in energy homeostasis. This phenomenon is controlled by systemic and local signals such as leptin, a nutrient-sensitive signal secreted primarily by the white adipose tissue (WAT). Previously, interscapular brown adipose tissue (iBAT) has been shown to express undetectable or very low levels of leptin. Unexpectedly, in this study, we observed that iBAT leptin expression displayed a distinct circadian pattern and fluctuated with nutritional and ambient temperature. These observations suggest a vital role of iBAT leptin in the regulation of energy homeostasis. To explore this idea, we performed gain and loss of function experiments by overexpressing (LEPOE) or knocking down (LEPKD) leptin selectively in UCP1+ cells of iBAT, respectively. We found that LEPOE reduced food intake while LEPKD increased it in normal and fasting-induced feeding conditions. Notably, LEPOE/LEPKD selectively increased/decreased the mRNA expression of leptin in the iBAT without affecting circulating leptin levels, indicating a possible paracrine role of iBAT leptin. In supporting this point of view, we found that the leptin receptor is highly expressed in the iBAT-associated sensory nerve (iBAT-SN). Moreover, iBAT-specific leptin infusion activated leptin signaling in the iBAT-SN and subsequently stimulated proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus. Conversely, chemical ablation of iBAT-SN increased food intake and blunted hypothalamic POMC activation induced by iBAT-specific leptin infusion. These findings indicate that iBAT possesses a structural and functional basis for paracrine leptin signaling via iBAT-SN, which cross-talks with POMC neurons to modulate energy homeostasis. Our results support an unappreciated metabolic role of iBAT leptin in energy homeostasis. Disclosure M.D.Munoz: None. X.Yang: None. V.C.Torres irizarry: None. P.Luo: None. L.Carrillo-sáenz: None. N.Antony: None. C.Liew: None. P.Xu: None. Funding National Institutes of Health (R01DK123098); U.S. Department of Defense (W81XWH-19-PRMRP-DA); Diabetes Research and Training Center (DK020595)

Cell-specific transcriptome changes in the hypothalamic arcuate nucleus in a mouse deoxycorticosterone acetate-salt model of hypertension.

A common preclinical model of hypertension characterized by low circulating renin is the "deoxycorticosterone acetate (DOCA)-salt" model, which influences blood pressure and metabolism through mechanisms involving the angiotensin II type 1 receptor (AT1R) in the brain. More specifically, AT1R within Agouti-related peptide (AgRP) neurons of the arcuate nucleus of the hypothalamus (ARC) has been implicated in selected effects of DOCA-salt. In addition, microglia have been implicated in the cerebrovascular effects of DOCA-salt and angiotensin II. To characterize DOCA-salt effects upon the transcriptomes of individual cell types within the ARC, we used single-nucleus RNA sequencing (snRNAseq) to examine this region from male C57BL/6J mice that underwent sham or DOCA-salt treatment. Thirty-two unique primary cell type clusters were identified. Sub-clustering of neuropeptide-related clusters resulted in identification of three distinct AgRP subclusters. DOCA-salt treatment caused subtype-specific changes in gene expression patterns associated with AT1R and G protein signaling, neurotransmitter uptake, synapse functions, and hormone secretion. In addition, two primary cell type clusters were identified as resting versus activated microglia, and multiple distinct subtypes of activated microglia were suggested by sub-cluster analysis. While DOCA-salt had no overall effect on total microglial density within the ARC, DOCA-salt appeared to cause a redistribution of the relative abundance of activated microglia subtypes. These data provide novel insights into cell-specific molecular changes occurring within the ARC during DOCA-salt treatment, and prompt increased investigation of the physiological and pathophysiological significance of distinct subtypes of neuronal and glial cell types.

Transcriptomic analysis reveals the effects of maternal exposure to bisphenol AF on hypothalamic development in male neonatal mice

Fragmented data suggest that bisphenol AF (BPAF), a chemical widely used in a variety of products, might have potential impacts on the hypothalamus. Here, we employed male neonatal mice following maternal exposure to explore the effects of low-dose BPAF on hypothalamic development by RNA-sequencing. We found that maternal exposure to approximately 50 µg/(kg·day) BPAF from postanal day (PND) 0 to PND 15 altered the hypothalamic transcriptome, primarily involving the pathways and genes associated with extracellular matrix (ECM) and intercellular adhesion, neuroendocrine regulation, and neurological processes. Further RNA analysis confirmed the changes in the expression levels of concerned genes. Importantly, we further revealed that low-dose BPAF posed a stimulatory impact on pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus and induced the browning of inguinal white adipose tissue. All findings indicate that developmental exposure to low-dose BPAF could interfere with hypothalamic development and thereby lead to alterations in the metabolism. Interestingly, 5000 µg/(kg·day) BPAF caused slighter, non-significant or even inverse alterations than the low dose of 50 µg/(kg·day), displaying a dose-independent effect. Further observations suggest that the the dose-independent effects of BPAF might be associated with oxidative stress and inflammatory responses caused by the high dose. Overall, our study highlights a risk of low-dose BPAF to human neuroendocrine regulation and metabolism.

Subacute high-refined carbohydrate diet leads to abnormal reproductive control of the hypothalamic-pituitary axis in female rats

We previously reported that female rats placed on a diet containing refined carbohydrates (HCD) resulted in obesity and reproductive abnormalities, such as high serum LH concentration and abnormal ovarian function. However, the impacts at the hypothalamic-pituitary (HP) function, specifically regarding pathways linked to reproductive axis modulation are unknown. In this study, we assessed whether subacute feeding with HCD results in abnormal reproductive control in the HP axis. Female rats were fed with HCD for 15 days and reproductive HP axis morphophysiology was assessed. HCD reduced hypothalamic mRNA expression (Kiss1, Lepr, and Amhr2) and increased pituitary LHβ+ cells. These changes likely contribute to the increase in serum LH concentration observed in HCD. Blunted estrogen negative feedback was observed in HCD, with increased kisspeptin protein expression in the arcuate nucleus of the hypothalamus (ARH), lower LHβ+ cells and LH concentration in ovariectomized (OVX)+HCD rats. Thus, these data suggest that HCD feeding led to female abnormal reproductive control of HP axis.

Regulation of Thyroid Hormone Levels by Hypothalamic Thyrotropin-Releasing Hormone Neurons.

Background: Thyrotropin-releasing hormone (TRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) have been identified as direct regulators of thyrotropin (TSH) and thyroid hormone (TH) levels. They play a significant role in context of negative feedback by TH at the level of TRH gene expression and during fasting when TH levels fall due, in part, to suppression of TRH gene expression. Methods: To test these functions directly for the first time, we used a chemogenetic approach and activated PVN TRH neurons in both fed and fasted mice. Next, to demonstrate the signals that regulate the fasting response in TRH neurons, we activated or inhibited agouti-related protein (AgRP)/neuropeptide Y (NPY) neurons in the arcuate nucleus of the hypothalamus of fed or fasted mice, respectively. To determine if the same TRH neurons responsive to melanocortin signaling mediate negative feedback by TH, we disrupted the thyroid hormone receptor beta (TRβ) in all melanocortin 4 receptor (MC4R) neurons in the PVN. Results: Activation of TRH neurons led to increased TSH and TH levels within 2 hours demonstrating the specific role of PVN TRH neurons in the regulation of the hypothalamic-pituitary-thyroid (HPT) axis. Moreover, activation of PVN TRH neurons prevented the fall in TH levels in fasting mice. Stimulation of AgRP/NPY neurons led to a fall in TH levels despite increasing feeding. Inhibition of these same neurons prevented the fall in TH levels during a fast presumably via their ability to directly regulate PVN TRH neurons via, in part, the MC4R. Surprisingly, TH-mediated feedback was not impaired in mice lacking TRβ in MC4R neurons. Conclusions: TRH neurons are major regulators of the HPT axis and the fasting-induced suppression of TH levels. The latter relies, at least in part, on the activation of AgRP/NPY neurons in the arcuate nucleus. Interestingly, present data do not support an important role for TRβ signaling in regulating MC4R neurons in the PVN. Thus, it remains possible that different subsets of TRH neurons in the PVN mediate responses to energy balance and to TH feedback.

Review: Gestational and postnatal nutritional effects on the neuroendocrine control of puberty and subsequent reproductive performance in heifers.

Pubertal attainment is an intricate biological process that involves maturation of the reproductive neuroendocrine axis and increased pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone. Nutrition is a critical environmental factor controlling the timing of puberty attainment. Nutrient restriction during early postnatal development delays puberty, whereas increased feed intake and adiposity during this period hasten pubertal maturation by imprinting the hypothalamus. Moreover, the dam's nutrition during gestation can program the neuroendocrine system in the developing fetus and has the potential to advance or delay puberty in the offspring. Leptin, a hormone produced primarily by adipose cells, plays an important role in communicating energy status to the brain and regulating sexual maturation. Leptin's regulation of GnRH release is mediated by an upstream neuronal network since GnRH neurons do not contain the leptin receptor. Two groups of neurons located in the arcuate nucleus of the hypothalamus that express neuropeptide Y (NPY), an orexigenic peptide, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide, are central elements of the neural circuitry that relay inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Moreover, KNDy neurons, neurons in the arcuate nucleus that co-express kisspeptin, neurokinin B (NKB), and dynorphin, also play a role in the metabolic regulation of puberty. Our studies in beef heifers demonstrate that increased rates of BW gain during early postweaning (4-9 mo of age) result in reduced expression of NPY mRNA, increased expression of proopiomelanocortin and kisspeptin receptor mRNA, reduced NPY inhibitory inputs to GnRH neurons, and increased excitatory αMSH inputs to KNDy neurons. Finally, our most recent data demonstrate that nutrition of the cow during the last two trimesters of gestation can also induce transcriptional and structural changes in hypothalamic neurocircuitries in the heifer progeny that likely persist long-term after birth. Managerial approaches, such as supplementation of the dam during gestation (fetal programming), creep feeding, early weaning, and stair-step nutritional regimens have been developed to exploit brain plasticity and advance pubertal maturation in heifers.

CPT1A in AgRP neurons is required for sex-dependent regulation of feeding and thirst

BackgroundFatty acid metabolism in the hypothalamus has an important role in food intake, but its specific role in AgRP neurons is poorly understood. Here, we examined whether carnitinea palmitoyltransferase 1A (CPT1A), a key enzyme in mitochondrial fatty acid oxidation, affects energy balance.MethodsTo obtain Cpt1aKO mice and their control littermates, Cpt1a(flox/flox) mice were crossed with tamoxifen-inducible AgRPCreERT2 mice. Food intake and body weight were analyzed weekly in both males and females. At 12 weeks of age, metabolic flexibility was determined by ghrelin-induced food intake and fasting–refeeding satiety tests. Energy expenditure was analyzed by calorimetric system and thermogenic activity of brown adipose tissue. To study fluid balance the analysis of urine and water intake volumes; osmolality of urine and plasma; as well as serum levels of angiotensin and components of RAAS (renin–angiotensin–aldosterone system) were measured. At the central level, changes in AgRP neurons were determined by: (1) analyzing specific AgRP gene expression in RiboTag–Cpt1aKO mice obtained by crossing Cpt1aKO mice with RiboTag mice; (2) measuring presynaptic terminal formation in the AgRP neurons with the injection of the AAV1-EF1a-DIO-synaptophysin-GFP in the arcuate nucleus of the hypothalamus; (3) analyzing AgRP neuronal viability and spine formations by the injection AAV9-EF1a-DIO-mCherry in the arcuate nucleus of the hypothalamus; (4) analyzing in situ the specific AgRP mitochondria in the ZsGreen-Cpt1aKO obtained by breeding ZsGreen mice with Cpt1aKO mice. Two-way ANOVA analyses were performed to determine the contributions of the effect of lack of CPT1A in AgRP neurons in the sex.ResultsChanges in food intake were just seen in male Cpt1aKO mice while only female Cpt1aKO mice increased energy expenditure. The lack of Cpt1a in the AgRP neurons enhanced brown adipose tissue activity, mainly in females, and induced a substantial reduction in fat deposits and body weight. Strikingly, both male and female Cpt1aKO mice showed polydipsia and polyuria, with more reduced serum vasopressin levels in females and without osmolality alterations, indicating a direct involvement of Cpt1a in AgRP neurons in fluid balance. AgRP neurons from Cpt1aKO mice showed a sex-dependent gene expression pattern, reduced mitochondria and decreased presynaptic innervation to the paraventricular nucleus, without neuronal viability alterations.ConclusionsOur results highlight that fatty acid metabolism and CPT1A in AgRP neurons show marked sex differences and play a relevant role in the neuronal processes necessary for the maintenance of whole-body fluid and energy balance.

Fasting and prolonged food restriction differentially affect GH secretion independently of GH receptor signaling in AgRP neurons.

Growth hormone (GH) receptor (GHR) is abundantly expressed in neurons that co-release the agouti-related protein (AgRP) and neuropeptide Y (NPY) in the arcuate nucleus of the hypothalamus (ARH). Since ARHAgRP/NPY neurons regulate several hypothalamic-pituitary-endocrine axes, this neuronal population possibly modulates GH secretion via a negative feedback loop, particularly during food restriction, when ARHAgRP/NPY neurons are highly active. The present study aims to determine the importance of GHR signaling in ARHAgRP/NPY neurons on the pattern of GH secretion in fed and food-deprived male mice. Additionally, we compared the effect of two distinct situations of food deprivation: 16 h of fasting or four days of food restriction (40% of usual food intake). Overnight fasting strongly suppressed both basal and pulsatile GH secretion. Animals lacking GHR in ARHAgRP/NPY neurons (AgRP∆GHR mice) did not exhibit differences in GH secretion either in the fed or fasted state, compared to control mice. In contrast, four days of food restriction increased GH pulse frequency, basal GH secretion, and pulse irregularity/complexity (measured by sample entropy), whereas pulsatile GH secretion was not affected in both control and AgRP∆GHR mice. Hypothalamic Ghrh mRNA levels were unaffected by fasting or food restriction, but Sst expression increased in acutely fasted mice, but decreased after prolonged food restriction in both control and AgRP∆GHR mice. Our findings indicate that short-term fasting and prolonged food restriction differentially affect the pattern of GH secretion, independently of GHR signaling in ARHAgRP/NPY neurons.

Hypothalamic Kisspeptin Neurons as a Target for Whole-Cell Patch-Clamp Recordings.

Kisspeptins are essential for the maturation of the hypothalamic-pituitary-gonadal (HPG) axis and fertility. Hypothalamic kisspeptin neurons located in the anteroventral periventricular nucleus and rostral periventricular nucleus, as well as the arcuate nucleus of the hypothalamus, project to gonadotrophin-releasing hormone (GnRH) neurons, among other cells. Previous studies have demonstrated that kisspeptin signaling occurs through the Kiss1 receptor (Kiss1r), ultimately exciting GnRH neuron activity. In humans and experimental animal models, kisspeptins are sufficient for inducing GnRH secretion and, consequently, luteinizing hormone (LH) and follicle stimulant hormone (FSH) release. Since kisspeptins play an essential role in reproductive functions, researchers are working to assess how the intrinsic activity of hypothalamic kisspeptin neurons contributes to reproduction-related actions and identify the primary neurotransmitters/neuromodulators capable of changing these properties. The whole-cell patch-clamp technique has become a valuable tool for investigating kisspeptin neuron activity in rodent cells. This experimental technique allows researchers to record and measure spontaneous excitatory and inhibitory ionic currents, resting membrane potential, action potential firing, and other electrophysiological properties of cell membranes. In the present study, crucial aspects of the whole-cell patch-clamp technique, known as electrophysiological measurements that define hypothalamic kisspeptin neurons, and a discussion of relevant issues about the technique, are reviewed.

Asprosin promotes feeding through SK channel-dependent activation of AgRP neurons.

Asprosin, a recently identified adipokine, activates agouti-related peptide (AgRP) neurons in the arcuate nucleus of the hypothalamus (ARH) via binding to protein tyrosine phosphatase receptor δ (Ptprd) to increase food intake. However, the intracellular mechanisms responsible for asprosin/Ptprd-mediated activation of AgRPARH neurons remain unknown. Here, we demonstrate that the small-conductance calcium-activated potassium (SK) channel is required for the stimulatory effects of asprosin/Ptprd on AgRPARH neurons. Specifically, we found that deficiency or elevation of circulating asprosin increased or decreased the SK current in AgRPARH neurons, respectively. AgRPARH-specific deletion of SK3 (an SK channel subtype highly expressed in AgRPARH neurons) blocked asprosin-induced AgRPARH activation and overeating. Furthermore, pharmacological blockade, genetic knockdown, or knockout of Ptprd abolished asprosin's effects on the SK current and AgRPARH neuronal activity. Therefore, our results demonstrated an essential asprosin-Ptprd-SK3 mechanism in asprosin-induced AgRPARH activation and hyperphagia, which is a potential therapeutic target for the treatment of obesity.

Activation of calcium-sensing receptors in the basolateral nucleus of the amygdala inhibits food intake and induces anxiety-depressive-like emotions via dopamine system

The calcium-sensing receptor (CaSR) is abundantly expressed in gastrointestinal mucosa and participates in the regulation of feeding by affecting hormone secretion. Studies have demonstrated that the CaSR is also expressed in feeding-related brain areas, such as the hypothalamus and limbic system, but the effect of the central CaSR on feeding has not been reported. Therefore, the aim of this study was to explore the effect of the CaSR in the basolateral amygdala (BLA) on feeding, and the potential mechanism was also studied. CaSR agonist R568 was microinjected into the BLA of male Kunming mice to investigate the effects of the CaSR on food intake and anxiety-depression-like behaviours. The enzyme-linked immunosorbent assay (ELISA) and fluorescence immunohistochemistry were used to explore the underlying mechanism. Our results showed that microinjection of R568 into the BLA could inhibit both standard and palatable food intake in mice for 0–2 h, induce anxiety-depression-like behaviours, increase glutamate levels in the BLA, and activate dynorphin and gamma-aminobutyric acid neurons through the N-methyl-D-aspartate receptor and thus reduce the content of dopamine in the arcuate nucleus of the hypothalamus (ARC) and ventral tegmental area (VTA), respectively. Our findings suggest that activation of the CaSR in the BLA inhibited food intake and caused anxiety-depression-like emotions. The reduced dopamine levels in the VTA and ARC via glutamatergic signals are involved in these functions of CaSR.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia.

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

A critical update on the leptin-melanocortin system.

The discovery of leptin in 1994 was an "eureka moment" in the field of neurometabolism that provided new opportunities to better understand the central control of energy balance and glucose metabolism. Rapidly, a prevalent model in the field emerged that pro-opiomelanocortin (POMC) neurons were key in promoting leptin's anorexigenic effects and that the arcuate nucleus of the hypothalamus (ARC) was a key region for the regulation of energy homeostasis. While this model inspired many important discoveries, a growing body of literature indicates that this model is now outdated. In this review, we re-evaluate the hypothalamic leptin-melanocortin model in light of recent advances that directly tackle previous assumptions, with a particular focus on the ARC. We discuss how segregated and heterogeneous these neurons are, and examine how the development of modern approaches allowing spatiotemporal, intersectional, and chemogenetic manipulations of melanocortin neurons has allowed a better definition of the complexity of the leptin-melanocortin system. We review the importance of leptin in regulating glucose homeostasis, but not food intake, through direct actions on ARC POMC neurons. We further highlight how non-POMC, GABAergic neurons mediate leptin's direct effects on energy balance and influence POMC neurons.

Profiling mouse brown and white adipocytes to identify metabolically relevant small ORFs and functional microproteins

Microproteins (MPs) are a potentially rich source of uncharacterized metabolic regulators. Here, we use ribosome profiling (Ribo-seq) to curate 3,877 unannotated MP-encoding small ORFs (smORFs) in primary brown, white, and beige mouse adipocytes. Of these, we validated 85 MPs by proteomics, including 33 circulating MPs in mouse plasma. Analyses of MP-encoding mRNAs under different physiological conditions (high-fat diet) revealed that numerous MPs are regulated in adipose tissue invivo and are co-expressed with established metabolic genes. Furthermore, Ribo-seq provided evidence for the translation of Gm8773, which encodes a secreted MP that is homologous to human and chicken FAM237B. Gm8773 is highly expressed in the arcuate nucleus of the hypothalamus, and intracerebroventricular administration of recombinant mFAM237B showed orexigenic activity in obese mice. Together, these data highlight the value of this adipocyte MP database in identifying MPs with roles in fundamental metabolic and physiological processes such as feeding.