Arcuate Nucleus Research Articles

FRI007 Kisspeptin Does Not Affect Food Intake In Women With Overweight Or Obesity

Abstract Disclosure: C. Izzi-Engbeaya: None. M. Choudhury: None. B. Patel: None. B. Muzi: None. A. Qayum: None. E.G. Mills: None. M. Ahsan: None. M. Phylactou: None. S. Clarke: None. L. Aslett: None. A.N. Comninos: None. A. Abbara: None. T. Tan: None. W.S. Dhillo: None. Background: Kisspeptin neurons in the hypothalamus are believed to play a role in mediating the interaction between metabolic and reproductive health. Functional neuroanatomical connections exist between kisspeptin neurons and appetite-regulating neurons in the arcuate nucleus of the hypothalamus. Female (but not male) global kisspeptin receptor knockout mice have reduced food intake compared to controls. However, studies of kisspeptin administration have yielded conflicting results, with either decreased, or unchanged food intake reported in rodent studies. Consistent with some of the literature, kisspeptin administration does not influence food intake in men. However, the effects of kisspeptin on food intake have not previously been studied in women. Research Question: What is the effect of kisspeptin administration on food intake in women? Methodology: A randomized controlled crossover study was performed in women with overweight or obesity (BMI >25 kg/m2) who were not in receipt of exogenous oral and/or transdermal estrogens or progestins. Each woman attended two study visits in random order following an overnight fast. During each study visit they received either a 2-hour intravenous infusion of kisspeptin-54 at a rate of 1.0 nmol/kg/hr, or a rate-matched vehicle infusion. The study was single-blinded, with participants unaware of the infusion identity. Participants were given an ad libitum meal 45 minutes after the start of each infusion. Blood samples were taken for reproductive and metabolic profiling, and visual analogue scales (VAS) to assess hunger were completed at regular intervals throughout both study visits. Data are presented as mean±SD. Results: 17 women (age 49±12 years, BMI 34±7 kg/m2) completed both study visits. As expected, LH levels were higher during kisspeptin than during vehicle infusion (p<0.01), confirming bioactivity of the kisspeptin dose. Pre-meal estradiol levels were similar during kisspeptin and vehicle infusions (p=0.34). There were no differences in pre-meal hunger VAS scores 30 mins after the start of the infusion (kisspeptin 5.2±2.7 vs vehicle 5.9±2.3, p=0.33) or bodyweight-adjusted food intake (kisspeptin 6.8±3.7 kcal/kg vs vehicle 6.2±2.8 kcal/kg, p=0.33). There were also no differences in glucose (p=0.97) or insulin (p=0.68) levels between kisspeptin and vehicle infusions. Conclusions: Acute intravenous administration of a biologically active dose of kisspeptin did not affect food intake or hunger in women with overweight or obesity. Furthermore, kisspeptin administration did not alter fasting or post-prandial glucose levels. This is the first study to examine the effects of kisspeptin on hunger and food intake in women and provides reassuring safety data for the ongoing development of kisspeptin-based therapeutics. Presentation: Friday, June 16, 2023

FRI284 The GnRH Pulse Generator Activity In Mouse Models Of Polycystic Ovary Syndrome

Abstract Disclosure: Z. Zhou: None. M. Pardo-Navarro: None. S.Y. Han: None. A.E. Herbison: None. Up to one in five women worldwide suffer from polycystic ovary syndrome (PCOS), a condition typified by problems with fertility, high androgen levels, and altered metabolism. Primarily due to the unknown aetiology of this disorder, limited strategies are available for PCOS treatment. The hypothalamic GnRH pulse generator is responsible for driving the pulsatile release of LH to control ovarian function. As PCOS patients show profound increase in LH pulse frequency, it is thought that over-activity of the GnRH pulse generator may have a major role in generating the sub-fertility of women with PCOS. Recent studies involving the real-time imaging of neural activity in genetic mouse models have revealed that a population of kisspeptin neurons located in the arcuate nucleus of the hypothalamus is the long-sought after “GnRH pulse generator”. These arcuate kisspeptin neurons exhibit synchronization events (SEs) that correlate perfectly with pulsatile LH secretion. With this technique, we aimed to characterize the activity pattern of the arcuate kisspeptin neurons in two most-widely used mouse models of PCOS: prenatal androgen (PNA) and peripubertal androgen models. In the first model, PNA female mice exhibited near-acyclic estrous cycles as previously reported, but surprisingly exhibited only a slightly (∼30%) increased frequency of arcuate kisspeptin neuron SEs over a 24-hour recording period compared to the controls. The profiles and dynamics of individual SEs were not different between PNA and control animals. Concurrent fiber photometry recording and serial blood sampling showed that each SE is tightly followed by an LH pulse in all animals. Three weeks following ovariectomy, the SE frequency and profile were not different between PNA and control mice. In the second peripubertal model, female mice implanted with dihydrotestosterone capsules at 3-weeks of age exhibited significant weight gain but decreased arcuate kisspeptin neuron activity over a 24-hour recording period also without changes in SE dynamics compared to the controls. In conclusion, it appears that neither of the two most-commonly used PCOS mouse models mirror the human condition in which many PCOS women exhibit robust increases in pulsatile LH secretion. Presentation: Friday, June 16, 2023

FRI064 The Role Of GLP-1 Receptor Agonists In The Treatment Of Pituitary And Hypothalamic Tumor Induced Obesity

Abstract Disclosure: C.S. Botero Suarez: None. D. Broutin: None. H. Yau: None. Introduction: Glucagon-like peptide-1 receptor agonists (GLP1-RA) act by stimulating the GLP-1 receptor resulting in a reduction in food intake, increased energy expenditure, and improved glycemic control. The role of GLP1-RA in pituitary/suprasellar tumors causing hyperphagia and hypothalamic obesity is yet unknown. We present a case of a patient with a large non-functional pituitary mass resulting in severe hyperphagia and hypothalamic obesity. A trial of GLP-1RA showed significant improvement of hyperphagia. Case Description: A 30-year-old African American male is seen in the Endocrinology clinic. He was recently diagnosed with a non-functional pituitary mass 2 months prior, after a presentation of hyperphagia, significant weight gain, and altered personality changes causing significant social distress. He underwent transsphenoidal pituitary resection which resulted in postoperative hypopituitarism. His physical exam showed normal vital signs, a weight of 185 lbs, and a BMI of 25. His medications included hydrocortisone total of 15 mg daily, desmopressin 0.1mg daily, levothyroxine 137mcg daily, and risperidone 1mg daily. A brain MRI showed postoperative changes depicted by a T1 hyperintensity within the sella as well as T2 hyperintensity of the chiasm and hypothalamus indicating edema and a mass effect. Based on his presentation of marked hyperphagia and rapid weight gain with suggestive imaging, the clinical diagnosis of hypothalamic obesity was made. Further follow-up revealed a rapid weight gain of 45 lbs in 2 months, a worsening glycemic control, and a HbA1C of 7.2% compared to a HbA1C of 5.4% in his prior visit. Lab work showed a TSH of 0.017 mlU/mL, fT4 of 1.4ng/dL, prolactin 3.94 ng/mL, alpha subunit of 0.1 ng/mL (reference 0.1-0.5 ng/mL), ACTH of 15 pg/mL, morning cortisol of < 3 ug/dL. Given the significant metabolic consequences of his marked hyperphagia, related weight gain, and new onset of diabetes, the patient was started on semaglutide 0.5mg weekly and later up-titrated to 1mg weekly. There was marked improvement of hyperphagia, and his weight remained neutral at the 3-month follow-up. Discussion: Hyperphagia is a rare presentation of sellar and suprasellar tumors and can lead to hypothalamic obesity. Tumors can affect the arcuate nucleus of the hypothalamus, which is a key regulator of energy homeostasis and is regulated by orexigenic (AgRP/NPY) and anorexigenic neurons (POMC/CART). GLP-1R agonists, have shown to cause significant weight loss due to decreased gastric emptying and stimulating POMC/CART neurons, but they also inhibit neuropeptide Y (NPY) and agouti-related peptide (AgRP), leading to reduced hunger, energy intake, and food cravings. Although the clinical role of GLP1-RA in pituitary tumors with significant hyperphagia is unknown, we believe early initiation can help avoid a rapid progression of obesity and glycemic deterioration. Presentation: Friday, June 16, 2023

FRI274 Dopamine Transporter-Expressing Leptin-Sensitive Neurons In The Ventral Premammillary Nucleus Innervate Kiss1 Neurons

Abstract Disclosure: C. Sáenz de Miera: None. L. Heikkinen: None. C. Broberger: None. C.F. Elias: None. Pubertal development is tightly regulated by energy balance, and easily disrupted in states of excess or negative energy reserves. This crosstalk between metabolism and reproduction is orchestrated by complex neural networks coordinated by circulating hormones, notably, leptin action in the hypothalamus plays a critical role. The ventral premammillary nucleus (PMv) is rich in leptin receptor (LepRb) neurons, and acts as an essential relay for leptin action on reproduction. Here, we describe a novel subpopulation of leptin sensitive neurons within the PMv that express dopamine transporter (DATPMv). We observed that in both prepubertal and adult females in diestrous, virtually all DATPMv neurons express LepRb mRNA and respond to acute leptin treatment with phosphorylation of the intracellular marker signal transducer and activator of transcription 3 (pSTAT3). Electrophyisological recordings from DAT-CRE;R26tdTomato (DAT-tdTom) mice show that DATPMv cells in adult females have a higher resting membrane potential than those in prepubertal females. DAT mRNA expression in the PMv is higher in prepubertal than in adult females. However, DAT mRNA expression was similar in adult females in diestrous, ovariectomized (OVX), and OVX treated with estradiol, indicating that the age difference observed is not due to the increase in estradiol during pubertal maturation. To trace DATPMv projections, we injected an adenoassociated virus expressing Cre-dependent channelrhodopsin (ChR2-mCherry) in the PMv of adult female DAT-Cre;Kiss1-hrGFP mice, which express GFP driven by kiss1 regulatory elements. ChR2-mCherry projections were observed in the anteroventral periventricular nucleus (AVPV) surrounding Kiss1-hrGFP neurons, a population critical for sexual maturation and positive estrogen feedback in females. No projections were observed near arcuate nucleus Kiss1-hrGFP neurons, in the medial preoptic area (MPOA) or near GnRH neurons. This contrasts with previous observations of dense projections from the overall PMv LepRb population to the MPOA, surrounding GnRH cell bodies suggesting the DATPMv subpopulation has different target areas than the non-DAT LepRb neurons. Using DAT-tdTOM females we observed that overall tdTom projections to the AVPV are denser in adult diestrous than in prepubertal females. Overall, these findings suggest that the DAT expressing LepR subpopulation in the PMv play a role in leptin regulation of sexual maturation via actions on AVPV kisspeptin neurons. Presentation: Friday, June 16, 2023

THU128 Transcription Factor ETV5 In POMC Neurons Regulate Energy And Glucose Homeostasis

Abstract Disclosure: S. Gahlot: None. A. Caron: None. S. Lee: None. J.K. Elmquist: None. Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARH) are critical for the regulation of energy balance and glucose homeostasis. Pomc gene transcription is regulated by the Erythrocyte Transformation Specific (ETS)-domain transcription factors, including Etv1, Etv2, Etv4, and Etv5. Large-scale genome-wide association studies have identified ETV5 genetic variants linked with human obesity and body mass index. Histological studies in adult mouse pituitaries also show the co-localization of ETV5 with POMC and POMC-derived peptides: adrenocorticotropic hormone (ACTH) and alpha-melanocyte stimulating hormone (α-MSH). Furthermore, whole-body Etv5 knockout mice are lean, severely glucose intolerant and hypoinsulinaemic. While these findings suggest a potential role for Etv5 in the control of energy and glucose balance, the role of Etv5 remains unknown. This study aims to determine whether ETV5 binds to the Pomc promoter to alter its expression and regulate energy balance and glucose homeostasis. To assess whether ETV5 binds to the Pomc promoter, we performed chromatin immunoprecipitation with quantitative real-time PCR (ChIP-qPCR) in C57BL/6J mice. ChIP-qPCR determined that Etv5 directly binds to the Pomc promoter. We further performed luciferase reporter assay in mouse neuroblastoma N2a cell lysates to measure the Pomc promoter activity after Etv5 knockdown or overexpression. Luciferase assay revealed that Etv5 knockdown increased, while Etv5 overexpression reduced the Pomc promoter activity in N2a cells. Also, Etv5 overexpression blocked the leptin-induced POMC activation. Further, to determine the role of Etv5 in POMC neurons to regulate energy balance and glucose homeostasis, we used the Cre/loxP system to selectively delete Etv5 from POMC neurons both prenatally and postnatally. Mice were fed either a standard chow or a 60% high-fat diet (HFD), followed by serial body weight, food intake, body composition, metabolic assessment, glucose tolerance and insulin tolerance test measurements. We found that mice with a prenatal deletion of Etv5 in POMC neurons had reduced body weight, reduced lean mass, and were protected from HFD-induced insulin resistance. Similarly, postnatal deletion of Etv5 in POMC neurons resulted in reduced body weight, lean mass and fat mass, and increased insulin sensitivity and energy expenditure in mice of 8 weeks age. We also performed electrophysiological recordings in hypothalamic slices from these mice to assess POMC neuron excitability. We found that loss of Etv5 increased the activity and electrical excitability of POMC neurons. These findings highlight a previously unrecognized role of Etv5 in POMC neurons in the regulation of energy balance and glucose homeostasis. These results also point to the potential therapeutic applications for Etv5 against obesity. Presentation: Thursday, June 15, 2023

FRI001 Tanycytic Thyroid-stimulating Hormone Receptor Activation Increases Blood-Hypothalamus Barrier Permeability And Induces Appetite In Female Mice

Abstract Disclosure: H.S. Kannangara: None. B. Jocoll: None. S. Miyashita: None. A. Gumerova: None. F. Korkmaz: None. R. Witztum: None. S. Sims: None. U. Cheliadinova: None. G. Pevnev: None. O. Moldavski: None. T. Frolinger: None. T. Yuen: None. V. Ryu: None. M. Zaidi: None. In addition to its well-known action to trigger thyroid hormone production, thyroid-stimulating hormone (TSH) is released in the brain, and its receptor (TSHR) has been found in brain sites, including the tanycytes of the third ventricle, that regulate ingestive behavior and convey metabolic information across the blood-hypothalamus barrier (BHB). Our recent work highlights largely undiscovered role for TSHRs in the tanycytes. Here, we tested the hypothesis that tanycytic TSHR activation triggers rapid remodeling of BHB vascular permeability inducing appetite. We compared hypothalamic vascular permeability of food deprived (FD) and ad libitum fed (AL) Tshr+/- and their wild type (WT) counterparts exploiting transmission electron microscopy studies and immunofluorescence for constitutive tight junction protein Claudin-1 and homodimer glycoprotein MECA-32, primarily expressed in tanycytes and endothelial cells, respectively. Fasting significantly increased the organization of tanycytic honeycomb pattern of Claudin-1 and fenestral MECA-32-associated diaphragms in the median eminence and arcuate nucleus implying decreased BHB vascular permeability in Tshr+/- mice. Transmission electron microscopy confirmed immunofluorescence results. In a separate gain-of-function experiment, TSHR activation by the small molecule MS438 increased BHB vascular permeability as evidenced by decreased Claudin-1 and MECA-32 immunostaining. Tanycytic TSHR activation significantly increased both food foraging and intake as during one-hour refeeding after FD. Surprisingly, refeeding restored neuronal activation marker c-Fos expression in the paraventricular nucleus of the hypothalamus, parabrachial nucleus and nucleus of the solitary tract, though failed to do so in the paraventricular nucleus and nucleus of the solitary tract of MS438-injected mice. Collectively, these data infer that modulation of tanycytic TSHRs plays an important role in BHB plasticity in relation with ingestive behavior. Presentation: Friday, June 16, 2023

SAT592 Sexually Dimorphic Modulation Of Arcuate Kisspeptin Neurons Activity In Response To NPY

Abstract Disclosure: N.D. Mansano: None. R. Frazao: None. Kisspeptin neurons are part of an intricate brain circuit that receives neuronal inputs related tonutritional status from at least three neuronal populations, including NPY/AgRP and POMC neurons of the arcuate nucleus of the hypothalamus (ARH) and cells in the ventral premammillary nucleus. Its well-known action on the HPG axis, hypothalamic kisspeptin neurons also modulate the activity of specific neurons of the paraventricular and the dorsomedial nuclei of the hypothalamus, regions involved in the regulation of appetite and energy expenditure. However, it is not completely elucidated if NPY can influence the HPG axis through the modulation of kisspeptin neuron activity. To determine the NPY effect in the hypothalamic kisspeptin neurons we performed whole-cell patch-clamp recordings. The hypothalamic slices were obtained from the adult Kiss1/hrGFP female (diestrus-stage) or male mice. Kisspeptin cells located in the arcuate nucleus of the hypothalamus (ARHkisspeptin) and at the anteroventral periventricular and rostral periventricular nuclei (AVPV/PeNkisspeptin) were recorded. On female mice, ARHkisspeptin neurons exhibited a rest membrane potential (RMP) average of -52.5±2.5 mV (-40 to -62 mV) and 1.3±0.2 GΩ input resistance (IR). NPY induced the hyperpolarization of 45% of the ARHkisspeptin neurons (n= 9 of 20 cells, out of 9 mice). ARHkisspeptin neuron’s RMP hyperpolarization was followed by a significant decrease in IR and frequency of action potentials (fAPS). In the AVPV/PeNkisspeptin neurons showed RMP average of -69.6±1.9 mV (-51 to - 88 mV) and IR of 0.8±0.09 GΩ (n=18 cells out of 9 mice). No significant NPY-induced effect was noted when recordings were performed on AVPV/PeNkisspeptin cells from female mice. To elucidate if the ARHkisspeptin neuron’s hyperpolarization depends on action potentials (APs) mediated by synaptic transmission we further evaluated NPY effects in the presence of TTX and amino acid receptor antagonists (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10μM), DL-2-amino-5-phosphonopentanoic acid (AP5, 50μM), and picrotoxin (50μM). NPY induced no effect on ARHkisspeptin neuron’s RMP, and IR in the presence of TTX and amino acid receptor antagonists. Suggesting that NPY-induced hyperpolarization of ARHkisspeptin neurons is an indirect effect. To further verify whether sex must be considered as a biological variable to study the NPY effect, we recorded ARHkisspeptin cells from male mice. ARHkisspeptin neurons recorded from male mice exhibited RPM average of -55.6±1.5 (-45 to -66 mV) and IR of 1.5±0.15 GΩ (n= 13 cells out of 10 mice). Interestingly, NPY induced no effect on RMP, IR, or fAPs in male animals. In conclusion, our results suggest that NPY-induced hyperpolarization of ARHkisspeptin cells depends on AP’s mediate synaptic transmission, as a sex-specific effect. Presentation: Saturday, June 17, 2023

Fasting Modulates GABAergic Synaptic Transmission to Arcuate Kisspeptin Neurons in Female Mice.

It is well-established that the hypothalamic-pituitary-gonadal (HPG) axis is suppressed due to negative energy balance. However, less information is available on whether kisspeptin neuronal activity contributes to fasting-induced responses. In the present study, female and male mice were fasted for 24 hours or provided food ad libitum (fed group) to determine whether acute fasting is sufficient to modulate kisspeptin neuronal activity. In female mice, fasting attenuated luteinizing hormone (LH) and prolactin (PRL) serum levels and increased follicle-stimulating hormone levels compared with the fed group. In contrast, fasting did not affect gonadotropin or PRL secretion in male mice. By measuring genes related to LH pulse generation in micropunches obtained from the arcuate nucleus of the hypothalamus (ARH), we observed that fasting reduced Kiss1 mRNA levels in female and male mice. In contrast, Pdyn expression was upregulated only in fasted female mice, whereas no changes in the Tac2 mRNA levels were observed in both sexes. Interestingly, the frequency and amplitude of the GABAergic postsynaptic currents recorded from ARH kisspeptin neurons (ARHKisspeptin) were reduced in 24-hour fasted female mice but not in males. Additionally, neuropeptide Y induced a hyperpolarization in the resting membrane potential of ARHKisspeptin neurons of fed female mice but not in males. Thus, the response of ARHKisspeptin neurons to fasting is sexually dependent with a female bias, associated with changes in gonadotropins and PRL secretion. Our findings suggest that GABAergic transmission to ARHKisspeptin neurons modulates the activity of the HPG axis during situations of negative energy balance.

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.

Differential voluntary feed intake and whole transcriptome profiling in the hypothalamus of young sheep offered CP and phosphorus-deficient diets.

A reduction in voluntary feed intake is observed in ruminants consuming nutrient-deficient diets, such as those with a low CP or P content, and has been attributed to active metabolic regulation, rather than a physical constraint. The hypothalamus is the key integrator of feed intake regulation in mammals. The objectives of this experiment were to (1) establish a model of metabolic feed intake regulation in ruminants consuming diets of variable CP and P content, and (2) determine key biochemical pathways and influential points of regulation within the hypothalamus. Merino wethers [n=40; 23.7±1.4kg liveweight (mean±SD)] were fed one of five dietary treatments (n=8/treatment) for 63days in individual pens. The treatments included targeted combinations of high (H) and low (L) CP (110 and 55g/kg DM) and high and low P (2.5 and 0.7g/kg DM) with 9MJ metabolisable energy (ME) per kg DM which were fed ad libitum (UMEI; unrestricted ME intake) resulting in four experimental diets (HCP-HP-UMEI, LCP-HP-UMEI, HCP-LP-UMEI and LCP-LP-UMEI). An additional nutritional treatment (HCP-HP-RMEI) restricted intake of the HCP-HP diet to an equivalent ME intake of wethers consuming the LCP-LP-UMEI treatment. Wethers offered the LCP-HP-UMEI, HCP-LP-UMEI and LCP-LP-UMEI treatments consumed 42, 32 and 49% less total DM (P≤0.05), respectively than the HCP-HP-UMEI treatment, and this was not attributable to any physical limitation of the rumen. Plasma concentrations of urea nitrogen and inorganic phosphate indicated that these nutrient deficiencies were successfully established. To assess potential mechanisms, RNA-seq was conducted on samples from the arcuate nucleus (ARC), ventromedial hypothalamus and lateral hypothalamus of the wethers, yielding a total of 301, 8 and 148 differentially expressed genes across all pairwise comparisons, respectively. The expression of NPY, AGRP and CARTPT, known for their regulatory role in mammalian feed intake regulation, had a similar transcriptional response in the ARC of wethers consuming nutrient-deficient treatments and those consuming a ME-restricted treatment, despite these wethers expressing behaviours indicative of satiated and hungry states, respectively. In addition, genes involved with glycolysis (TPI1), the citric acid cycle (CS, OGDH, GLUD1, GOT1) and oxidative phosphorylation (COX5A, ATP5MC1, ATP5F1B, ATP5MC3) were downregulated in the ARC of wethers fed a nutrient deficient (LCP-LP-UMEI) relative to the non-deficient (HCP-HP-UMEI) treatment. In summary, a model for voluntary feed intake restriction was established to determine genome-wide molecular changes in the hypothalamus of young ruminants.

Study on the protective mechanism of neuropeptide S in neonates with hypoxic ischemic encephalopathy

Hypoxic-ischemic brain damage (HIBD) is a severe complication of neonatal asphyxia that contributes significantly to neonatal mortality, cerebral palsy, and delays in intellectual and motor development. Neuropeptide S (NPS) plays a role in the regulation of various physiological processes. This study aimed to determine the morphological localization of NPS in hypothalamic target neurons during HIBD, providing a basis for further investigation of HIBD. Seven-day-old SD neonatal male rats were assigned to a sham group and a model group to establish the HIBD model. Then, the rats in the model group were further averagely divided into the NPS group and the normal saline group. Immunohistochemical staining of Fos immunoreactivity (Fos-IR) found that NPS administration resulted in a significant increase in the count of Fos-IR neurons in the suprachiasmatic nucleus (122%), paraventricular nucleus (108%), dorsal tuberomammillary nucleus (174% and 386%), ventromedial hypothalamic nucleus (116%), arcuate nucleus (167%), perifornical nucleus (320%), ventral tuberomammillary nucleus (441%), and lateral hypothalamic area (278%) (P < 0.0001), compared to the normal saline group. During HIBD, NPS can protect the above neurons and activate the above target neurons in the hypothalamus to participate in the sleep and wake cycle, mood, diet, circadian rhythm, temperature and neuroendocrine regulation.

Perinatal metabolic inflammation in the hypothalamus impairs the development of homeostatic feeding circuitry.

Over the past few decades, there has been a global increase in childhood obesity. This rise in childhood obesity contributes to the susceptibility of impaired metabolism during both childhood and adulthood. The hypothalamus, specifically the arcuate nucleus (ARC), houses crucial neurons involved in regulating homeostatic feeding. These neurons include proopiomelanocortin (POMC) and agouti-related peptide (AGRP) secreting neurons. They play a vital role in sensing nutrients and metabolic hormones like insulin, leptin, and ghrelin. The neurogenesis of AGRP and POMC neurons completes at birth; however, axon development and synapse formation occur during the postnatal stages in rodents. Insulin, leptin, and ghrelin are the essential regulators of POMC and AGRP neurons. Maternal obesity and postnatal overfeeding or a high-fat diet (HFD) feeding cause metabolic inflammation, disrupted signaling of metabolic hormones, netrin-1, and neurogenic factors, neonatal obesity, and defective neuronal development in animal models; however, the mechanism is unclear. Within the hypothalamus and other brain areas, there exists a wide range of interconnected neuronal populations that regulate various aspects of feeding. However, this review aims to discuss how perinatal metabolic inflammation influences the development of POMC and AGRP neurons within the hypothalamus.

Chronic estradiol exposure suppresses luteinizing hormone surge without affecting kisspeptin neurons and estrogen receptor alpha in anteroventral periventricular nucleus†.

Mammalian ovulation is induced by a luteinizing hormone surge, which is triggered by elevated plasma estrogen levels; however, chronic exposure to high levels of estradiol is known to inhibit luteinizing hormone secretion. In the present study, we hypothesized that the inhibition of the luteinizing hormone surge by chronic estradiol exposure is due to the downregulation of the estrogen receptor alpha in kisspeptin neurons at hypothalamic anteroventral periventricular nucleus, which is known as the gonadotropin-releasing hormone/luteinizing hormone surge generator. Animals exposed to estradiol for 2days showed an luteinizing hormone surge, whereas those exposed for 14days showed a significant suppression of luteinizing hormone. Chronic estradiol exposure did not affect the number of kisspeptin neurons and the percentage of kisspeptin neurons with estrogen receptor alpha or c-Fos in anteroventral periventricular nucleus, but it did affect the number of kisspeptin neurons in arcuate nucleus. Furthermore, chronic estradiol exposure did not affect gonadotropin-releasing hormone neurons. In the pituitary, 14-day estradiol exposure significantly reduced the expression of Lhb mRNA and LHβ-immunoreactive areas. Gonadotropin-releasing hormone-induced luteinizing hormone release was also reduced significantly by 14-day estradiol exposure. We revealed that the suppression of an luteinizing hormone surge by chronic estradiol exposure was induced in association with the significant reduction in kisspeptin neurons in arcuate nucleus, luteinizing hormone expression in the pituitary, and pituitary responsiveness to gonadotropin-releasing hormone, and this was not caused by changes in the estrogen receptor alpha-expressing kisspeptin neurons in anteroventral periventricular nucleus and gonadotropin-releasing hormone neurons, which are responsible for estradiol positive feedback.

Fructooligosaccharides and galactooligosaccharides improve hepatic steatosis via gut microbiota-brain axis modulation

Studies have shown that gut dysbiosis is associated with the steatotic liver disease associated with metabolic dysfunction (MALSD) and its severity. This study evaluated the effects of two commercially available prebiotics fructooligosaccharides (FOS) and galactooligosaccharides(GOS) on hepatic adipogenesis, inflammation, and gut microbiota in high-fat diet-induced MALSD. The results indicated that FOS and GOS effectively reduced insulin resistance, hyperglycaemia, triglyceridemia, cholesterolaemia, and IL-1β serum levels. Moreover, FOS and GOS modulated the lipogenic (SREBP-1c, ACC, and FAS) and lipolytic (ATGL) signalling pathways, and reduced inflammatory markers such as p-NFκB-65, IL-6, iNOS, COX-2, TNF-α, IL-1β, and nitrotyrosine. FOS and GOS also enhanced the abundance of acetate producers’ bacteria Bacteroides acidifaciens and Bacteroides dorei. FOS and GOS also induced positive POMC/GPR43 neurons at the arcuate nucleus, indicating hypothalamic signalling modulation. Our results suggest that FOS and GOS attenuated MALSD by reducing the hepatic lipogenic pathways and intestinal permeability through the gut microbiota-brain axis.

Lesions of KNDy and Kiss1R Neurons in the Arcuate Nucleus Produce Different Effects on LH Pulse Patterns in Female Sheep.

The current model for the synchronization of GnRH neural activity driving GnRH and LH pulses proposes that a set of arcuate (ARC) neurons that contain kisspeptin, neurokinin B, and dynorphin (KNDy neurons) is the GnRH pulse generator. This study tested the functional role of ovine KNDy neurons in pulse generation and explored the roles of nearby Kiss1 receptor (Kiss1R)-containing cells using lesions produced with saporin (SAP) conjugates. Injection of NK3-SAP ablated over 90% of the KNDy cells, while Kiss-SAP (saporin conjugated to kisspeptin-54) lesioned about two-thirds of the Kiss1R population without affecting KNDy or GnRH cell number. Both lesions produced a dramatic decrease in LH pulse amplitude but had different effects on LH pulse patterns. NK3-SAP increased interpulse interval, but Kiss-SAP did not. In contrast, Kiss-SAP disrupted the regular hourly occurrence of LH pulses, but NK3-SAP did not. Because Kiss1R is not expressed in KNDy cells, HiPlex RNAScope was used to assess the colocalization of 8 neurotransmitters and 3 receptors in ARC Kiss1R-containing cells. Kiss1R cells primarily contained transcript markers for GABA (68%), glutamate (28%), ESR1 (estrogen receptor-α) mRNA, and OPRK1 (kappa opioid receptor) mRNA. These data support the conclusion that KNDy neurons are essential for GnRH pulses in ewes, whereas ARC Kiss1R cells are not but do maintain the amplitude and regularity of GnRH pulses. We thus propose that in sheep, ARC Kiss1R neurons form part of a positive feedback circuit that reinforces the activity of the KNDy neural network, with GABA or glutamate likely being involved.

Suprachiasmatic nucleus promotes hyperglycemia induced by sleep delay

Short sleep is linked to disturbances in glucose metabolism and may induce a prediabetic condition. The biological clock in the suprachiasmatic nucleus (SCN) regulates the glucose rhythm in the circulation and the sleep-wake cycle. SCN vasopressin neurons (SCNVP) control daily glycemia by regulating the entrance of glucose into the arcuate nucleus (ARC). Thus, we hypothesized that sleep delay may influence SCN neuronal activity. We, therefore, investigated the role of SCNVP when sleep is disrupted by forced locomotor activity. After 2h of sleep delay, rats exhibited decreased SCNVP neuronal activity, a decrease in the glucose transporter GLUT1 expression in tanycytes lining the third ventricle, lowered glucose entrance into the ARC, and developed hyperglycemia. The association between reduced SCNVP neuronal activity and hyperglycemia in sleep-delayed rats was evidenced by injecting intracerebroventricular vasopressin; this increased GLUT1 immunoreactivity in tanycytes, thus promoting normoglycemia. Following sleep recovery, glucose levels decreased, whereas SCNVP neuronal activity increased. These results imply that sleep-delay-induced changes in SCNVP activity lead to glycemic impairment, inferring that disruption of biological clock function might represent a critical step in developing type 2 diabetes.

Fasting increases circulating angiotensin levels and brain Agtr1a expression in male rats.

In addition to being recognised for involvement in cardiovascular control and hydromineral balance, the renin-angiotensin system (RAS) has also been associated with the neuroendocrine control of energy balance. One of the main brain sites for angiotensin II (ANG II)/type 1 receptor (AT1 R) signalling is the subfornical organ (SFO), a circumventricular organ related to the control of autonomic functions, motivated behaviours and energy metabolism. Thus, we hypothesised that circulating ANG II may act on the SFO AT1 R receptors to integrate metabolic and hydromineral balance. We evaluated whether food deprivation can modulate systemic RAS activity and Agrt1a brain expression, and if ANG II/AT1 R signalling influences the hypothalamic expression of mRNAs encoding neuropeptides and food and water ingestion in fed and fasted Wistar rats. We found a significant increase in both ANG I and ANG II plasma levels after 24 and 48 h of fasting. Expression of Agrt1a mRNA in the SFO and paraventricular nucleus (PVN) also increased after food deprivation for 48 h. Treatment of fasted rats with low doses of losartan in drinking water attenuated the decrease in glycemia and meal-associated water intake without changing the expression in PVN or arcuate nucleus of mRNAs encoding selected neuropeptides related to energy homeostasis control. These findings point to a possible role of peripheral ANG II/SFO-AT1 R signalling in the control of refeeding-induced thirst. On the other hand, intracerebroventricular losartan treatment decreased food and water intake over dark time in fed but not in fasted rats.

The neurocircuitry of fasting-induced glucocorticoid release

Activation of the hypothalamus-pituitary-adrenal gland (HPA) axis confers adaptations to homeostatic perturbations including food scarcity. A comprehensive new study by Douglass etal. disentangled how agouti-related peptide (AgRP)-expressing neurons of the arcuate nucleus (ARC) trigger rapid HPA-axis activation in response to fasting, which is mediated by repression of a tonic, inhibitory neuro circuit.

Effect of Hypoglycemic Drugs on Kisspeptin Expression in the Hypothalamic Arcuate Nucleus of PCOS Rats.

To investigate the change in hypothalamic kisspeptin-1 (Kiss1) expression during the development of polycystic ovary syndrome (PCOS) and hypoglycemic drug intervention. Letrozole lavage was used to construct a polycystic ovary rat model. After successful modeling, we treated PCOS rats with metformin, pioglitazone, and acarbose, and we then observed changes in weight, estrus, glucose tolerance, insulin resistance, sex hormones, and hypothalamic kiss1 expression. PCOS rats exhibited increased body weight, abnormal estrous cycle, impaired glucose tolerance, insulin resistance, increased testosterone level, increased luteinizing hormone level, and increased Kiss1 expression in the hypothalamus. However, intervention with metformin, pioglitazone, and acarbose improved the reproductive and metabolic disorders as well as reduced hypothalamic Kiss1 expression. The expression of hypothalamic Kiss1 may play an important role in the pathogenesis of PCOS. Metformin, pioglitazone, and acarbose may reduce the expression of hypothalamic Kiss1 by improving insulin resistance, thereby improving reproductive and metabolic disorders in PCOS rats.

Neonatal overnutritional programming impairs the hypophagia and neuron activation induced by acute lipopolysaccharide in adult male rats

ABSTRACT Nutritional status during critical windows in early development can challenge metabolic functions and physiological responses to immune stress in adulthood, such as the systemic inflammation induced by lipopolysaccharide (LPS). The aim of this study was to investigate the long-term effects of post-natal over- and undernutrition on the anorexigenic effect of LPS and its association with neuronal activation in the brainstem and hypothalamus of male rats. Animals were raised in litters of 3 (small – SL), 10 (normal – NL), or 16 (large – LL) pups per dam. On post-natal day 60, male rats were treated with LPS (500 µg/Kg) or vehicle for the evaluation of food intake and c-Fos expression in the area postrema (AP), nucleus of solitary tract (NTS), and paraventricular (PVN), arcuate (ARC), ventromedial (VMH), and dorsomedial (DMH) nuclei of the hypothalamus. SL, NL, and LL animals showed a decreased food consumption after LPS treatment. In under- and normonourished animals, peripheral LPS induced an increase in neuronal activation in the brainstem, PaV, PaMP, and ARC and a decrease in the number of c-Fos-ir neurons in the DMH. Overnourished rats showed a reduced hypophagic response, lower neuron activation in the NTS and PaMP, and no response in the DMH induced by LPS. These results indicate that early nutritional programming displays different responses to LPS, by means of neonatal overnutrition decreasing LPS-mediated anorexigenic effect and neuronal activation in the NTS and hypothalamic nuclei.