Suppression Of Feeding Behavior Research Articles

Hypothalamic nesfatin-1 mediates feeding behavior via MC3/4R-ERK signaling pathway after weight loss in obese Sprague-Dawley rats

Nesfatin-1 is an anorexic peptide derived from nucleobindin 2 (NUCB2). An increase in hypothalamic nesfatin-1 inhibits feeding behavior and promotes weight loss. However, the effects of weight loss on hypothalamic nesfatin-1 levels are unclear. In this study, obese rats lost weight in three ways: Calorie Restriction diet (CRD), Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). We found an increase in nesfatin-1 serum and cerebrospinal fluid levels after weight loss in obese Sprague-Dawley (SD) rats. Moreover, weight loss also increased hypothalamic melanocortin 3/4 receptor (MC3/4R) and extracellular regulated kinase phosphorylation (p-ERK) signaling. Third ventricle administration of antisense morpholino oligonucleotide (MON) against the gene encoding NUCB2 inhibited hypothalamic nesfatin-1 and p-ERK signaling, increased food intake and reduced body weight loss in SG and RYGB obese rats. Third ventricle administration of SHU9119 (MC3/4R blocker) blocked hypothalamic MC3/4R, inhibited p-ERK signaling, increased food intake and reduced body weight loss in SG and RYGB obese rats. These findings indicate that weight loss leads to an increase in hypothalamic nesfatin-1. The increase in hypothalamic nesfatin-1 participates in regulating feeding behavior through the MC3/4R-ERK signaling especially after SG and RYGB.

SUN-098 Goldfish Insulin: Molecular Cloning, Hepatic Regulation by Spexin, and Mechanisms for Feeding Control in Fish Model

Insulin is a key hormone for metabolism and glucose homeostasis. In mammals, it also acts as a satiety factor with inhibitory effect on food intake, but its biological actions in appetite control in lower vertebrates is still unknown. Spexin (SPX), a neuropeptide with pleotropic functions, has been recently confirmed to be a novel satiety factor in fish model via functional coupling with insulin, although the details of their interactions have yet to be elucidated. In this study, using goldfish as a model, the mechanism for feeding regulation by insulin and its functional interactions with SPX at hepatic level were examined. As a first step, goldfish insulin was cloned and found to be widely expressed at tissue level, especially with high levels of expression in the liver and visceral fat. In silico modeling also showed that the 3D structure of the mature peptide of goldfish insulin was highly comparable if not identical to its human counterpart. In goldfish liver cell culture, insulin mRNA level could be up-regulated by SPX treatment via PLC/IP3/PKC and Ca2+/CaM/CaMK-II pathways, while the opposite was true by removing endogenous SPX using immunoneutralization with SPX antiserum. In whole animal experiment, IP injection with insulin was found to inhibit feeding behavior and food consumption in goldfish. Similar treatment in vivo was also effective in elevating POMC, CART, CCK and leptin mRNA levels with concurrent drop in NPY, AGRP and apelin transcript expression in the telencephalon, optic tectum and hypothalamus, the brain areas known to be involved in feeding control in fish models. Using brain cell culture prepared from these three areas, similar changes in transcript expression for the respective orexigenic and anorexigenic factors were also noted with insulin treatment in a time- and dose-dependent manner. These findings, as a whole, suggest that SPX can act in an autocrine/paracrine manner to induce insulin expression in goldfish liver and the subsequence rise of insulin in circulation presumably can inhibit food intake through differential regulation of orexigenic/anorexigenic signals expressed in brain areas involved in appetite control in fish model.

Experimental Pediatric Obesity Impairs Central Control of Food Behavior

According to WHO in 2016, 41 million children in their frist5 years of age are either overweight or obese. Overweight and obese children have a higher risk to stay obese into adulthood and present more incidences to develop chronic diseases. The control of the food and energy intake is essentially controlled and integrated by hypothalamic neuropeptide with anorexigenic and orexigenic functions such as ‘cocaine‐and‐amphetamine‐regulated transcript (CART) co‐expressing neurons, which suppress feeding behavior or activation of agouti related‐peptide (AgRP) co‐expressing neurons that induces an increase in appetite response. Additionally to the peptides, specific receptors also play a key role in the control of the food behavior, such as 5‐HT1b and 5‐HT2c, acting regulating meal size and eating rate in association to the neuropeptides. Until the moment the effect of pediatric obesity and the expression of these neuropeptides and receptors remains to be more explored. Three days after delivery, the puppies were randomly assigned into two groups: Controls (nine pups per mother, n=6) or Overfed (three pups per mother, n=6). At 21 days, all male pups began to receive water and commercial chow ad libitum until 60 days of age. We evaluate body weight‐BW, 24 hours food intake‐FI, blood glucose and triglycerides levels, CART, AgRP, 5‐HT1b, and 5‐HT2c gene expression. Our data demonstrate that reduction in litter size induce the increase in BW since the seventh day of life and maintains until the sacrifice (7, 22, 60th, p<0.001). Associated with BW, we observed an increase in FI in dark cycle (p<0.01) and in light cycle (p<0.05). Evaluating serum patterns, we verify an increase in glucose (p<0.05) and in triglycerides (p<0.001). At the molecular levels, we observe an impressive decrease in CART expression (p<0.001) in the overfed group. Taken our data together, we suggest that neonatal overfed induce energetic disturb increasing the risk of metabolic syndrome in a possible mechanism mediated to alteration on neuropeptide signaling in the central control of food behavior.Support or Funding InformationFACEPE APQ grant #0164‐4.05/15; This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ‐ Brasil (CAPES) ‐ Finance code 001This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Melanocortin-3 Receptors Expressed on Agouti-Related Peptide Neurons Inhibit Feeding Behavior in Female Mice.

ObjectiveActivation of hypothalamic agouti-related peptide (AgRP)+ve neurons during energy deficit is a negative valence signal, rapidly activating food seeking behaviors. This study examined the roles of MC3Rs expressed by AgRP+ve neurons.MethodsAgRP-MC3R mice expressing MC3Rs selectively in AgRP+ve neurons were generated by crossing AgRP-IRES-Cre mice with LoxTBMc3r mice containing a “loxP-STOP-loxP” sequence in the 5’ UTR. Body weight, body composition and feeding behavior were assessed during ad libitum and timed-restricted feeding conditions.ResultsIn females, food intake of AgRP-IRES-Cre(+ve) (n=7) or AgRP-IRES-Cre(-ve) (n=9) mice was not significantly different; these mice were therefore pooled to form the “control” group. Female AgRP-MC3R mice exhibited lower food intake (25.4±2.4 kJ/12h, n=6) compared to controls (35.3±1.8 kJ/12h, n=16) and LoxTBMc3r mice (32.1±2.1 kJ/12h, n=9) in the active phase during the dark period. Food intake during the rest phase (lights-on) when mice consume less food (9–10 kJ) was normal between genotypes. Body weight and composition of AgRP-MC3R and LoxTBMc3r mice was similar, suggesting compensatory mechanisms for reduced calorie intake. Remarkably, AgRP-MC3R mice continued to consume less food during re-feeding after fasting and timed-restricted feeding.ConclusionsMC3Rs expressed on AgRP+ve neurons appear to exert a strong inhibitory signal on hypothalamic networks governing feeding behavior.

To eat or not to eat: ontogeny of hypothalamic feeding controls and a role for leptin in modulating life-history transition in amphibian tadpoles.

Many animal life histories entail changing feeding ecology, but the molecular bases for these transitions are poorly understood. The amphibian tadpole is typically a growth and dispersal life-history stage. Tadpoles are primarily herbivorous, and they capitalize on growth opportunities to reach a minimum body size to initiate metamorphosis. During metamorphic climax, feeding declines, at which time the gastrointestinal (GI) tract remodels to accommodate the carnivorous diet of the adult frog. Here we show that anorexigenic hypothalamic feeding controls are absent in the tadpole, but develop during metamorphosis concurrent with the production of the satiety signal leptin. Before metamorphosis there is a large increase in leptin mRNA in fat tissue. Leptin receptor mRNA increased during metamorphosis in the preoptic area/hypothalamus, the key brain region involved with the control of food intake and metabolism. This corresponded with an increase in functional leptin receptor, as evidenced by induction of socs3 mRNA and phosphorylated STAT3 immunoreactivity, and suppression of feeding behaviour after injection of recombinant frog leptin. Furthermore, we found that immunoneutralization of leptin in tadpoles at metamorphic climax caused them to resume feeding. The absence of negative regulation of food intake in the tadpole allows the animal to maximize growth prior to metamorphosis. Maturation of leptin-responsive neural circuits suppresses feeding during metamorphosis to facilitate remodelling of the GI tract.

AIM interneurons mediate feeding suppression through the TYRA-2 receptor in C. elegans

Feeding behavior is the most fundamental behavior in C. elegans. Our previous results have dissected the central integration circuit for the regulation of feeding, which integrates opposing sensory inputs and regulates feeding behavior in a nonlinear manner. However, the peripheral integration that acts downstream of the central integration circuit to modulate feeding remains largely unknown. Here, we find that a Gαi/o-coupled tyramine receptor, TYRA-2, is involved in peripheral feeding suppression. TYRA-2 suppresses feeding behavior via the AIM interneurons, which receive tyramine/octopamine signals from RIM/RIC neurons in the central integration circuit. Our results reveal previously unidentified roles for the receptor TYRA-2 and the AIM interneurons in feeding regulation, providing a further understanding of how biogenic amines tyramine and octopamine regulate feeding behavior.

Rapid binge-like eating and body weight gain driven by zona incerta GABA neuron activation.

The neuronal substrate for binge eating, which can at times lead to obesity, is not clear. We find that optogenetic stimulation of mouse zona incerta (ZI) γ-aminobutyric acid (GABA) neurons or their axonal projections to paraventricular thalamus (PVT) excitatory neurons immediately (in 2 to 3 seconds) evoked binge-like eating. Minimal intermittent stimulation led to body weight gain; ZI GABA neuron ablation reduced weight. ZI stimulation generated 35% of normal 24-hour food intake in just 10 minutes. The ZI cells were excited by food deprivation and the gut hunger signal ghrelin. In contrast, stimulation of excitatory axons from the parasubthalamic nucleus to PVT or direct stimulation of PVT glutamate neurons reduced food intake. These data suggest an unexpected robust orexigenic potential for the ZI GABA neurons.

Suprachiasmatic vasopressin to paraventricular oxytocin neurocircuit in the hypothalamus relays light reception to inhibit feeding behavior.

Light synchronizes the body's circadian rhythms by modulating the master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. In modern lifestyles that run counter to normal circadian rhythms, the extended and/or irregular light exposure impairs circadian rhythms and, consequently, promotes feeding and metabolic disorders. However, the neuronal pathway through which light is coupled to feeding behavior is less elucidated. The present study employed the light exposure during the dark phase of the day in rats and observed its effect on neuronal activity and feeding behavior. Light exposure acutely suppressed food intake and elevated c-Fos expression in the AVP neurons of SCN and the oxytocin (Oxt) neurons of paraventricular nucleus (PVN) in the hypothalamus. The light-induced suppression of food intake was abolished by blockade of the Oxt receptor in the brain. Retrograde tracer analysis demonstrated the projection of SCN AVP neurons to the PVN. Furthermore, intracerebroventricular injection of AVP suppressed food intake and increased c-Fos in PVN Oxt neurons. Intra-PVN injection of AVP exerted a stronger anorexigenic effect than intracerebroventriclar injection. AVP also induced intracellular Ca2+ signaling and increased firing frequency in Oxt neurons in PVN slices. These results reveal the novel neurocircuit from SCN AVP to PVN Oxt that relays light reception to inhibition of feeding behavior. This light-induced neurocircuit may serve as a pathway for forming the circadian feeding rhythm and linking irregular light exposure to arrhythmic feeding and, consequently, obesity and metabolic diseases.

PT709. Dopaminergic functions suppress feeding behavior through neuropeptides in the hypothalamus.

PT709. Dopaminergic functions suppress feeding behavior through neuropeptides in the hypothalamus.

Effects of central administration of oxytocin-saporin cytotoxin on chronic inflammation and feeding/drinking behaviors in adjuvant arthritic rats

An increase in the arthritis index as a marker of chronic inflammation and suppression of food intake are observed in adjuvant arthritic (AA) rats. Our previous study demonstrated that central oxytocin (OXT)-ergic pathways were activated potently in AA rats. In the present study, OXT-saporin (SAP) cytotoxin, which chemically disrupts OXT signaling was administered centrally to determine whether central OXT may be involved in the developments of chronic inflammation and alteration of feeding/drinking behavior in AA rats. The arthritis index was significantly enhanced in AA rats pretreated with OXT-SAP administered intrathecally (i.t.) but not intracerebroventricularly (i.c.v.). Suppression of food intake was significantly attenuated transiently in AA rats pretreated with OXT-SAP administered i.c.v. but not i.t. Suppression of drinking behavior was not affected by i.t. or i.c.v. administration of OXT-SAP in AA rats. In addition, intraperitoneal administration of an OXT receptor antagonist did not change the arthritis index or feeding/drinking behavior in AA rats. These results suggest that central OXT-ergic pathways may be involved in anti-inflammation at the spinal level and suppression of feeding behavior at the forebrain-brainstem level in AA rats.

Opioid systems in the lateral hypothalamus regulate feeding behavior through orexin and GABA neurons

The hypothalamus controls feeding behavior. Since central opioid systems may regulate feeding behavior, we examined the role of μ-, δ- and κ-opioid receptors in the lateral hypothalamus (LH), the hunger center, in feeding behavior of mice. Non-selective (naloxone; 3mg/kg, s.c.) and selective μ- (β-funaltrexamine, β-FNA; 10mg/kg, s.c.), δ- (naltrindole; 3mg/kg, s.c.) and κ- (norbinaltorphimine, norBNI; 20mg/kg, s.c.) opioid receptor antagonists significantly decreased food intake in food-deprived mice. The injection of naloxone (20μg/side) into the LH significantly decreased food intake whereas the injection of naloxone (20μg/side) outside of the LH did not affect food intake. The injection of β-FNA (2μg/side), naltrindole (1μg/side) or norBNI (2μg/side) into the LH significantly decreased food intake. Furthermore, all these antagonists significantly decreased the mRNA level of preproorexin, but not those of other hypothalamic neuropeptides. In addition, the injection of the GABAA receptor agonist muscimol (5μg/side) into the LH significantly decreased food intake, and this effect was abolished by the GABAA receptor antagonist bicuculline (50μg/side). Muscimol (1mg/kg, i.p.) decreased the mRNA level of preproorexin in the hypothalamus. Naloxone (3mg/kg, s.c.) significantly increased the GABA level in the LH and both bicuculline and the GABA release inhibitor 3-mercaptopropionic acid (3-MP, 5μg/side) attenuated the inhibitory effect of naloxone on feeding behavior. 3-MP also attenuated the effects of β-FNA and norBNI, but not that of naltrindole. These results show that opioid systems in the LH regulate feeding behavior through orexin neurons. Moreover, μ- and κ-, but not δ-, opioid receptor antagonists inhibit feeding behavior by activating GABA neurons in the LH.

Inhibition of opioid systems in the hypothalamus as well as the mesolimbic area suppresses feeding behavior of mice

Opioid receptors, especially μ-opioid receptors, in the ventral tegmental area (VTA) and nucleus accumbens (NAcc) are reported to regulate food motivation. However, the roles of μ-, δ- and κ-opioid receptors are not fully understood. Moreover, since μ-, δ- and κ-opioid receptors are reported to distribute in the hypothalamus, these receptors in the hypothalamus might regulate feeding behavior. Thus, the present study investigated the role of μ-, δ- and κ-opioid receptors in the VTA, the NAcc and the hypothalamus in the regulation of feeding behavior. Male ICR mice were subjected to a feeding test after food deprivation for 16h. The mRNA levels of proopiomelanocortin (POMC), preproenkephalin (PENK) and prodynorphin (PDYN), the precursors of endogenous opioid peptides, were measured by reverse transcription-polymerase chain reaction (RT-PCR). The systemic injection of non-selective (naloxone) and selective μ (β-funaltrexamine; β-FNA), δ (naltrindole) and κ (norbinaltorphimine; norBNI) opioid receptor antagonists markedly reduced food intake. In contrast, the systemic injection of preferential μ (morphine), selective δ (KNT-127) and κ (U-50,488) opioid receptor agonists did not change food intake. The mRNA levels of POMC, PENK and PDYN were decreased in the hypothalamus and the midbrain after food deprivation, whereas the mRNA levels of PENK and PDYN, but not POMC, were decreased in the ventral striatum. The injection of naloxone into the NAcc, VTA and lateral hypothalamus (LH), but not the ventromedial nucleus of the hypothalamus, significantly decreased food intake. The injection of β-FNA and naltrindole into the LH, but not the VTA or NAcc, decreased food intake. The injection of norBNI into the LH and VTA, but not the NAcc, decreased food intake. These results indicate that μ-, δ- and κ-opioid receptors in the LH play a more important role in the regulation of feeding behavior than those receptors in the VTA and the NAcc.

Sa2022 Subliminal Esophageal Acid Exposure Is Associated With an Increase of Right Insula Functional Connectivity in the Homeostatic Afferent Processing Network

Background/Aim: Excessive stress in modern society is associated with development of functional dyspepsia, which presents with symptoms of epigastric pain, early satiety and postprandial fullness. The central neural peptides, members of the corticotropin-releasing factor family, play key roles in response to stress. We previously reported that urocortin1 (UCN1) suppressed feeding behavior in fasted rats through an α2-adrenergic receptor (α2AR) activation, which decreases ghrelin secretion (DDW 2014). However, the influence of UCN1 on gastrointestinal (GI) function remains unclear. To elucidate this, we investigated the changes in gastric emptying and GI motility in UCN1-treated rats. Methods: UCN1 (300 pmol/rat) or phosphate-buffered saline (PBS) were intracerebroventricularly (ICV) injected to Sprague-Dawley rats, and gastric emptying and plasma ghrelin levels 2 h after oral administration of test meal were measured. The α2-AR antagonist, yohimbine (5 mg/kg) 15 min before ICV were intraperitoneal(IP) administered to UCN1-treated rats. Furthermore, ghrelin (3 nmol/rat, intravenous (IV)) were administered to UCN1-treated rats. In another set of experiment, the effects of co-administration of rikkunshito (RKT; 1000 mg/kg, which is an endogenous ghrelin enhancer) and with the ghrelin receptor antagonist ([D-Lys3] GHRP-6; 4 μmol/kg IV) was investigated. GI motility was investigated to determine the effects of ghrelin or RKT to UCN1-treated rats using a strain gauge force transducer in free-moving condition. Results: UCN1-treated rats exhibited significantly delayed gastric emptying. Administration of yohimbine improved gastric emptying (UCN1: 22.9±6.5 %, UCN1+yohimbine: 58.5±7.6 %, p<0.05) and significantly increased plasma ghrelin levels (UCN1:47.2±3.6 fmol/mL, UCN1+yohimbine: 81.9±7.8 fmol/mL, p<0.05). Exogenous administration of ghrelin restored delayed gastric empting. Administration of RKT significantly prevented delayed gastric empting and decreased plasma ghrelin levels. The gastric function of RKT was blocked by co-administration of the ghrelin receptor antagonist. ICV injection of UCN1 decreased the amplitude of contraction in the stomach while increasing the amplitude in the duodenum. Motility index of the stomach, but not the duodenum, was significantly reduced by treatment with UCN1 (PBS: 92.1 ± 10.1%, UCN1: 62.8 ± 4.7%), which was improved by the administration of ghrelin or RKT (99.03 ± 7.95%, p<0.05). Conclusions UCN1-induced gastric motility dysfunction with decrease in plasma ghrelin levels wasmediated byα2-AR activation. Disturbance in endogenous ghrelin dynamics play an important role in the functional abnormality of the upper GI tract under stressful conditions.

Sa2021 The Stress Hormone Urocortin 1 Induces Gastric Dysfunction by α2-Adrenergic Receptor-Mediated Decrease in Ghrelin Signal in Rats

Background/Aim: Excessive stress in modern society is associated with development of functional dyspepsia, which presents with symptoms of epigastric pain, early satiety and postprandial fullness. The central neural peptides, members of the corticotropin-releasing factor family, play key roles in response to stress. We previously reported that urocortin1 (UCN1) suppressed feeding behavior in fasted rats through an α2-adrenergic receptor (α2AR) activation, which decreases ghrelin secretion (DDW 2014). However, the influence of UCN1 on gastrointestinal (GI) function remains unclear. To elucidate this, we investigated the changes in gastric emptying and GI motility in UCN1-treated rats. Methods: UCN1 (300 pmol/rat) or phosphate-buffered saline (PBS) were intracerebroventricularly (ICV) injected to Sprague-Dawley rats, and gastric emptying and plasma ghrelin levels 2 h after oral administration of test meal were measured. The α2-AR antagonist, yohimbine (5 mg/kg) 15 min before ICV were intraperitoneal(IP) administered to UCN1-treated rats. Furthermore, ghrelin (3 nmol/rat, intravenous (IV)) were administered to UCN1-treated rats. In another set of experiment, the effects of co-administration of rikkunshito (RKT; 1000 mg/kg, which is an endogenous ghrelin enhancer) and with the ghrelin receptor antagonist ([D-Lys3] GHRP-6; 4 μmol/kg IV) was investigated. GI motility was investigated to determine the effects of ghrelin or RKT to UCN1-treated rats using a strain gauge force transducer in free-moving condition. Results: UCN1-treated rats exhibited significantly delayed gastric emptying. Administration of yohimbine improved gastric emptying (UCN1: 22.9±6.5 %, UCN1+yohimbine: 58.5±7.6 %, p<0.05) and significantly increased plasma ghrelin levels (UCN1:47.2±3.6 fmol/mL, UCN1+yohimbine: 81.9±7.8 fmol/mL, p<0.05). Exogenous administration of ghrelin restored delayed gastric empting. Administration of RKT significantly prevented delayed gastric empting and decreased plasma ghrelin levels. The gastric function of RKT was blocked by co-administration of the ghrelin receptor antagonist. ICV injection of UCN1 decreased the amplitude of contraction in the stomach while increasing the amplitude in the duodenum. Motility index of the stomach, but not the duodenum, was significantly reduced by treatment with UCN1 (PBS: 92.1 ± 10.1%, UCN1: 62.8 ± 4.7%), which was improved by the administration of ghrelin or RKT (99.03 ± 7.95%, p<0.05). Conclusions UCN1-induced gastric motility dysfunction with decrease in plasma ghrelin levels wasmediated byα2-AR activation. Disturbance in endogenous ghrelin dynamics play an important role in the functional abnormality of the upper GI tract under stressful conditions.

Effect of peptide agonists of peripheral opioid receptors on operant feeding behavior and food motivation in rats.

We studied the effect of intragastric administration of peptide agonists of μ-opioid receptors (DAMGO) and δ-opioid receptors (DADLE) on food consumption and food motivation during operant feeding behavior of different intensity and effectiveness. To obtain one food granule, trained rats should press a lever 1 time (day 1), 2 times (day 2), 4 times (day 3), 8 times (day 4), 16 times (day 5), or 32 times (day 6). Activation of δ-opioid receptors in the stomach was followed by suppression of feeding behavior at low energy expenditure. The level of food motivation under these conditions practically did not differ from the control. Activation of μ-opioid receptors in the stomach suppressed energy-consuming feeding behavior, which was accompanied by an increase in the level of food motivation. It can be hypothesized that protein metabolites exhibiting μ-opioid activity probably provide afferent signals into CNS via the vagus nerve to terminate energy expenditure under adverse conditions (although food motivation is not satisfied). Food motivation under these conditions probably contributes to the behavior aimed towards the search for more available food.

Serotonin 2C receptor contributes to gender differences in stress-induced hypophagia in aged mice

The combination of depression and anorexia may influence morbidity and progressive physical disability in the elderly. Gender differences exist in hypothalamic-pituitary-adrenal axis activation following stress exposure. The objective of this study was to investigate gender differences in feeding behavior under novelty stress in aged mice. Food intake measurement, immunohistochemical assessment, and mRNA expression analysis were conducted to investigate the role of serotonin 2C receptor (5-HT(2C)R) and its relationship with ghrelin in stress-induced suppression of feeding behavior in aged mice. After exposure to novelty stress, a 21-fold increase in plasma corticosterone and remarkable suppression of food intake were observed in aged male mice. Furthermore, a 5-HT(2C)R agonist suppressed food intake in aged male mice. Novelty stress induced a 7-fold increase in 5-HT(2C)R and c-Fos co-expressing cells in the paraventricular nucleus of the hypothalamus in aged male mice but caused no change in aged female mice. Plasma acylated ghrelin levels decreased in stressed aged male mice and administration of the 5-HT(2C)R antagonist inhibited this decrease. The 5-HT(2C)R antagonist also reversed the suppression of food intake in estrogen receptor α agonist-treated aged male mice. Therefore, conspicuously suppressed feeding behavior in novelty stress-exposed aged male mice may be mediated by 5-HT(2C)R hypersensitivity, leading to hypoghrelinemia. The hypersensitivity may partly be due to estrogen receptor activation in aged male mice.

Peripheral Injection of Chicken Growth Hormone-Releasing Hormone Inhibits Feeding Behavior in Chicks.

Growth hormone-releasing hormone (GHRH), a stimulator of growth hormone (GH) secretion, is known to have several physiological roles such as the regulation of feeding behavior in mammals. Recently, we have reported that central injection of chicken GHRH decreased food intake in chicks, however, its peripheral role on feeding behavior has not been clarified. The purpose of the present study was to investigate the effect of peripheral injection of GHRH on feeding behavior in chicks (Gallus gallus). Intraperitoneal (IP) injection of GHRH47 (1 nmol), full length form of chicken GHRH significantly decreased food intake in chicks although the injection of GHRH27 and GHRH27-NH2, short forms of chicken GHRH had no effect. The IP injection of GHRH47 did not induced any abnormal behavior, suggesting that GHRH47-induced anorexia might not be related to abnormal behavior such as sleeping, hyperactivity and convulsion. The anorexigenic effect of GHRH47 seemed not to be related to GH because IP injection of bovine GH did not affect feeding behavior in chicks. Collectively, these results suggest that peripheral GHRH is related to inhibit feeding behavior in chicks.

Leptin i mehanizam delovanja leptina

Leptin is a hormone produced by the adipose tissue, which has effects on the central nervous system. Leptin is bound to its Ob receptor on hypo-thalamic neurons to inhibit feeding behavior and to increase sympathetically-mediated thermogenesis. In addition to anorexia and thermogenesis, leptin also has direct peripheral and central nervous system-mediated effects on the endocrine, vascular, hematopoietc, immune and musculoskeletal systems. Leptin accomplishes its effects using distributed network of leptin receptors and differential molecular signaling pathways. Leptinemia is increased in obesity because of increased adipocyte mass, but obese subjects exhibit resistance to the anorexic and metabolic effects of leptin. However, multiple studies have shown that leptin can increase sympathetic nerve activity to non-thermogenic tissues in rodents causing obesity-related hypertension. One potential explanation of this paradox is selective leptin resistance. Compared with large and persuasive number of studies on the sympathetic and blood pressure effects of leptin in experimental animals, relatively little attention was given to these effects of leptin in humans. This review article presents recent findings related to leptin and its mechanism of action, and also the role of leptin in patophysiological conditions.

Central administration of chicken growth hormone-releasing hormone decreases food intake in chicks

Growth hormone-releasing hormone (GHRH) is well known as a stimulator of growth hormone (GH) secretion. GHRH not only stimulates GH release but also modifies feeding behavior and energy homeostasis in rodents. In chickens (Gallus gallus domesticus), on the other hand, two types of GHRH, namely, chicken GHRH (cGHRH) and cGHRH-like peptide (cGHRH-LP), have been identified. The purpose of the present study was to investigate the effect of central injection of cGHRH and cGHRH-LP on feeding behavior in chicks. Intracerebroventricular (ICV) injection of both cGHRH and cGHRH-LP (0.04 to 1nmol) significantly decreased food intake without any abnormal behavior in chicks. Furthermore, the feeding-inhibitory effect was not abolished by co-injection of the antagonist for pituitary adenylate cyclase-activating polypeptide (PACAP) or corticotropin-releasing hormone (CRH) receptors, suggesting that the anorexigenic effect of cGHRH and cGHRH-LP might not be related to the PACAP and CRH systems in the brain of chicks. Finally, 24-h food deprivation increased mRNA expression of cGHRH but not cGHRH-LP in the diencephalon. These results suggest that central cGHRH is related to inhibiting feeding behavior and energy homeostasis in chicks.

Functions of two distinct "prolactin-releasing peptides" evolved from a common ancestral gene.

Prolactin-releasing peptide (PrRP) is one of the RF-amide peptides and was originally identified in the bovine hypothalamus as a stimulator of prolactin (PRL) release. Independently, another RF-amide peptide was found in Japanese crucian carp and named Carassius-RFa (C-RFa), which shows high homology to PrRP and stimulates PRL secretion in teleost fish. Therefore, C-RFa has been recognized as fish PrRP. However, recent work has revealed that PrRP and C-RFa in non-mammalian vertebrates are encoded by separate genes originated through duplication of an ancestral gene. Indeed, both PrRP and C-RFa are suggested to exist in teleost, amphibian, reptile, and avian species. Therefore, we propose that non-mammalian PrRP (C-RFa) be renamed PrRP2. Despite a common evolutionary origin, PrRP2 appears to be a physiological regulator of PRL, whereas this is not a consistent role for PrRP itself. Further work revealed that the biological functions of PrRP and PrRP2 are not limited solely to PRL release, because they are also neuromodulators of several hypothalamus–pituitary axes and are involved in some brain circuits related to the regulation of food intake, stress, and cardiovascular functions. However, these actions appear to be different among vertebrates. For example, central injection of PrRP inhibits feeding behavior in rodents and teleosts, while it stimulates it in chicks. Therefore, both PrRP and PrRP2 have acquired diverse actions through evolution. In this review, we integrate the burgeoning information of structures, expression profiles, and multiple biological actions of PrRP in higher vertebrates, as well as those of PrRP2 in non-mammals.