The anorexigenic and hypertensive effects of nesfatin-1 are reversed by pretreatment with an oxytocin receptor antagonist

Nesfatin-1 inhibits gastric acid secretion via a central vagal mechanism in rats

Nesfatin-1, a novel hypothalamic peptide, inhibits nocturnal feeding behavior and gastrointestinal motility in rodents. The effects of nesfatin-1 on gastrointestinal secretory function, including gastric acid production, have not been evaluated. Nesfatin-1 was injected into the fourth intracerebral ventricle (4V) of chronically cannulated rats to identify a nesfatin dose sufficient to inhibit food intake. Nesfatin-1 (2 μg) inhibited dark-phase food intake, in a dose-dependent fashion, for >3 h. Gastric acid production was evaluated in urethane-anesthetized rats. Nesfatin-1 (2 μg) was introduced via the 4V following endocrine stimulation of gastric acid secretion by pentagastrin (2 μg·kg(-1)·h(-1) iv), vagal stimulation with 2-deoxy-D-glucose (200 mg/kg sc), or no stimulus. Gastric secretions were collected via gastric cannula and neutralized by titration to determine acid content. Nesfatin-1 did not affect basal and pentagastrin-stimulated gastric acid secretion, whereas 2-deoxy-D-glucose-stimulated gastric acid production was inhibited by nesfatin-1 in a dose-dependent manner. c-Fos immunofluorescence in brain sections was used to evaluate in vivo neuronal activation by nesfatin-1 administered via the 4V. Nesfatin-1 caused activation of efferent vagal neurons, as evidenced by a 16-fold increase in the mean number of c-Fos-positive neurons in the dorsal motor nucleus of the vagus (DMNV) in nesfatin-1-treated animals vs. controls (P < 0.01). Finally, nesfatin-induced Ca(2+) signaling was evaluated in primary cultured DMNV neurons from neonatal rats. Nesfatin-1 caused dose-dependent Ca(2+) increments in 95% of cultured DMNV neurons. These studies demonstrate that central administration of nesfatin-1, at doses sufficient to inhibit food intake, results in inhibition of vagally stimulated secretion of gastric acid. Nesfatin-1 activates DMNV efferent vagal neurons in vivo and triggers Ca(2+) signaling in cultured DMNV neurons.

Nesfatin-1 influences the excitability of neurons in the nucleus of the solitary tract and regulates cardiovascular function

Nesfatin-1 has been identified as one of the most potent centrally acting anorexigenic peptides, and it has also been shown to play important roles in the control of cardiovascular function. In situ hybridization and immunohistochemical studies have revealed the expression of nesfatin-1 throughout the brain and, in particular, in the medullary autonomic gateway known as the nucleus of the solitary tract (NTS). The present study was thus undertaken to explore the cellular correlates and functional roles of nesfatin-1 actions in the medial NTS (mNTS). Using current-clamp electrophysiology recordings from mNTS neurons in slice preparation, we show that bath-applied nesfatin-1 directly influences the excitability of the majority of mNTS neurons by eliciting either depolarizing (42%, mean: 7.8 ± 0.8 mV) or hyperpolarizing (21%, mean: −8. 2 ± 1.0 mV) responses. These responses were observed in all electrophysiologically defined cell types in the NTS and were site specific and concentration dependent. Furthermore, post hoc single cell reverse transcriptase polymerase reaction revealed a depolarizing action of nesfatin-1 on NPY and nucleobindin-2-expressing mNTS neurons. We have also correlated these actions of nesfatin-1 on neuronal membrane potential with physiological outcomes, using in vivo microinjection techniques to demonstrate that nesfatin-1 microinjected into the mNTS induces significant increases in both blood pressure (mean AUC = 3354.1 ± 750.7 mmHg·s, n = 6) and heart rate (mean AUC = 164.8 ± 78.5 beats, n = 6) in rats. Our results provide critical insight into the circuitry and physiology involved in the profound effects of nesfatin-1 and highlight the NTS as a key structure mediating these autonomic actions.

Nesfatin-1(30-59) but not the N- and C-terminal fragments, nesfatin-1(1-29) and nesfatin-1(60-82) injected intracerebroventricularly decreases dark phase food intake by increasing inter-meal intervals in mice

Nesfatin-1 is an 82 amino acid N-terminal fragment of nucleobindin2 that was consistently shown to reduce dark phase food intake upon brain injection in rodents. We recently reported that nesfatin-1(1-82) injected intracerebroventricularly (icv) reduces dark phase feeding in mice. Moreover, intraperitoneal injection of mid-fragment nesfatin-1 (nesfatin-1(30-59)) mimics the food intake-reducing effects of nesfatin-1(1-82), whereas N-terminal (nesfatin-1(1-29)) and C-terminal fragments (nesfatin-1(60-82)) did not. We therefore characterized the structure-activity relationship of nesfatin-1 injected icv to influence the dark phase meal pattern in mice. Mouse nesfatin-1(1-29), nesfatin-1(30-59), nesfatin-1(60-82) or vehicle was injected icv in freely fed C57Bl/6 mice immediately before the dark phase and food intake was monitored using an automated episodic feeding monitoring system. Nesfatin-1(30-59) (0.1, 0.3, 0.9 nmol/mouse) induced a dose-related reduction of 4-h food intake by 28%, 49% and 49% respectively resulting in a 23% decreased cumulative 24-h food intake compared to vehicle at the 0.3 nmol/mouse dose (p<0.05). The peak reduction occurred during the 3rd (-96%) and 4th hour (-91%) post injection and was associated with a reduced meal frequency (0-4h: -47%) and prolonged inter-meal intervals (3.1-times) compared to vehicle (p<0.05), whereas meal size was not altered. In contrast, neither nesfatin-1(1-29) nor nesfatin-1(60-82) reduced dark phase food intake at equimolar doses although nesfatin-1(60-82) prolonged inter-meal intervals (1.7-times, p<0.05). Nesfatin-1(30-59) is the active core of nesfatin-1(1-82) to induce satiety indicated by a reduced meal number during the first 4h post injection. The delayed onset may be indicative of time required to modulate other hypothalamic and medullary networks regulating nocturnal feeding as established for nesfatin-1.

Nesfatin-1, a unique regulatory neuropeptide of the brain

Nesfatin-1, a newly discovered NUCB2-derived satiety neuropeptide is expressed in several neurons of forebrain, hindbrain, brainstem and spinal cord. This novel anorexigenic substance seems to play an important role in hypothalamic pathways regulating food intake and energy homeostasis. Nesfatin-1 immunoreactive cells are detectable in arcuate (ARC), paraventricular (PVN) and supraoptic nuclei (SON), where the peptide is colocalized with POMC/CART, NPY, oxytocin and vasopressin. The nesfatin-1 molecule interacts with a G-protein coupled receptor and its cytophysiological effect depends on inhibitory hyperpolarization of NPY/AgRP neurons in ARC and melanocortin signaling in PVN. Administration of nesfatin-1 significantly inhibits consumatory behavior and decreases weight gain in experimental animals. These recent findings suggest the evidence for nesfatin-1 involvement in other important brain functions such as reproduction, sleep, cognition and anxiety- or stress-related responses. The neuroprotective and antiapoptotic properties of nesfatin-1 were also reported. From the clinical viewpoint it should be noteworthy, that the serum concentration of nesfatin-1 may be a sensitive marker of epileptic seizures. However, the details of nesfatin-1 physiology ought to be clarified, and it may be considered suitable in the future, as a potential drug in the pharmacotherapy of obesity, especially in patients treated with antipsychotics and antidepressants. On the other hand, some putative nesfatin-1 antagonists may improve eating disorders.

Nucleobindins: bioactive precursor proteins encoding putative endocrine factors?

The nucleobindins, nucleobindin 1 (NUCB1) and nucleobindin 2 (NUCB2), are homologous multidomain calcium and DNA binding proteins. NUCB1 is a well-characterized Golgi protein found within the rat pituitary, liver and kidney with functions related to immunity, calcium homeostasis and G protein signaling. NUCB2 is found both in the hypothalamus and brain stem centers, as well as peripherally in the digestive tract. Renewed interest in the nucleobindins has been sparked by the recent discovery of nesfatin-1, an endocrine factor post-translationally processed from the N-terminal of NUCB2. Nesfatin-1 has quickly established itself as a novel regulator of appetite, insulin secretion, energy homeostasis and reproduction with important consequences to the etiology of metabolic diseases including diabetes and obesity. The discovery of nesfatin-1 and it endocrine functions attracted more attention to the nucleobindins that are already known to have important intracellular functions. From the sequence information available, it is possible that nucelobindins itself or nesfatin-1 like peptides within the NUCB1 could also elicit nesfatin-1-like biological functions. The research on nesfatin-1 in last 5years further adds to the importance of nucleobindins as potential endocrine precursors. This review aims to summarize some of the most recent findings on the functional significance of NUCB1, NUCB2, as well as encoded proteins and highlights the questions that remain unanswered.

Yin and Yang - the Gastric X/A-like Cell as Possible Dual Regulator of Food Intake

Ingestion of food affects secretion of hormones from enteroendocrine cells located in the gastrointestinal mucosa. These hormones are involved in the regulation of various gastrointestinal functions including the control of food intake. One cell in the stomach, the X/A-like has received much attention over the past years due to the production of ghrelin. Until now, ghrelin is the only known orexigenic hormone that is peripherally produced and centrally acting to stimulate food intake. Subsequently, additional peptide products of this cell have been described including desacyl ghrelin, obestatin and nesfatin-1. Desacyl ghrelin seems to be involved in the regulation of food intake as well and could play a counter-balancing role of ghrelin's orexigenic effect. In contrast, the initially proposed anorexigenic action of obestatin did not hold true and therefore the involvement of this peptide in the regulation of feeding is questionable. Lastly, the identification of nesfatin-1 in the same cell in different vesicles than ghrelin extended the function of this cell type to the inhibition of feeding. Therefore, this X/A-like cell could play a unique role by encompassing yin and yang properties to mediate not only hunger but also satiety.

mTOR-dependent modulation of gastric nesfatin-1/NUCB2

BACKGROUND

Nesfatin-1, an 82 amino acid peptide derived from the prohormone nucleobindin-2 (NUCB2), is a novel satiety hormone acting through a leptin-independent mechanism in the hypothalamus. The mechanisms by which production of nesfatin-1/NUCB2 is regulated remain unknown.

METHODS

Nesfatin-1/NUCB2 mRNA and immunoreactivity were examined in gastric tissue and Min-6 cells by RT-PCR and immunofluorescent staining or Western blotting.

RESULTS

Nesfatin-1/NUCB2 is co-localized with pS6K1, the downstream target of mammalian target of rapamycin (mTOR), in gastric X/A like cells. A parallel relationship between gastric mTOR signaling and nesfatin-1/NUCB2 was observed during changes in energy status. Both mTOR activity and gastric nesfatin-1/NUCB2 were down-regulated by fasting, and returned to basal levels with re-feeding. In high fat diet induced obese mice, gastric mTOR signaling and nesfatin-1/NUCB2 were increased. Inhibition of the gastric mTOR signaling by rapamycin attenuated the expression of gastric nesfatin-1/NUCB2 mRNA and protein in both lean and obese mice. Attenuation of mTOR activity by rapamycin or over-expression of TSC1 or TSC2 reduced the expression of nesfatin-1/NUCB2 in Min-6 cells, suggesting a direct effect of mTOR signaling.

CONCLUSION

Gastric mTOR is a gastric energy sensor whose activity is linked to the regulation of gastric nesfatin-1/NUCB2.

mTOR-dependent modulation of gastric nesfatin-1/NUCB2

BACKGROUND

Nesfatin-1, an 82 amino acid peptide derived from the prohormone nucleobindin-2 (NUCB2), is a novel satiety hormone acting through a leptin-independent mechanism in the hypothalamus. The mechanisms by which production of nesfatin-1/NUCB2 is regulated remain unknown.

METHODS

Nesfatin-1/NUCB2 mRNA and immunoreactivity were examined in gastric tissue and Min-6 cells by RT-PCR and immunofluorescent staining or Western blotting.

RESULTS

Nesfatin-1/NUCB2 is co-localized with pS6K1, the downstream target of mammalian target of rapamycin (mTOR), in gastric X/A like cells. A parallel relationship between gastric mTOR signaling and nesfatin-1/NUCB2 was observed during changes in energy status. Both mTOR activity and gastric nesfatin-1/NUCB2 were down-regulated by fasting, and returned to basal levels with re-feeding. In high fat diet induced obese mice, gastric mTOR signaling and nesfatin-1/NUCB2 were increased. Inhibition of the gastric mTOR signaling by rapamycin attenuated the expression of gastric nesfatin-1/NUCB2 mRNA and protein in both lean and obese mice. Attenuation of mTOR activity by rapamycin or over-expression of TSC1 or TSC2 reduced the expression of nesfatin-1/NUCB2 in Min-6 cells, suggesting a direct effect of mTOR signaling.

CONCLUSION

Gastric mTOR is a gastric energy sensor whose activity is linked to the regulation of gastric nesfatin-1/NUCB2.

Ontogenic pattern of nucleobindin-2/nesfatin-1 expression in the gastroenteropancreatic tissues and serum of Sprague Dawley rats

Nesfatin-1 is a novel metabolic hormone that has glucose-responsive insulinotropic actions. Islet β-cells and gastrointestinal tissues have been reported as abundant sources of nesfatin-1 and its precursor hormone nucleobindin-2 (NUCB2). While nesfatin-1 is emerging as a multifunctional hormone, there are no reports on the developmental expression of NUCB2/nesfatin-1. The main objective of this study was to examine the ontogenic expression of NUCB2 mRNA, and NUCB2/nesfatin-1 immunoreactivity in the pancreas, stomach and duodenum, and the circulating levels NUCB2/nesfatin-1 in Sprague Dawley rats. In addition, we also determined the co-localization of NUCB2/nesfatin-1 and insulin immunoreactivity during development. NUCB2/nesfatin-1 immunoreactivity was found in the rat stomach from postnatal days 13-27. Furthermore, NUCB2/nesfatin-1 immunoreactivity was also detected in the enteroendocrine cells of the duodenum at postnatal days 13 and 27. Duodenal NUCB2 mRNA expression at postnatal day 27 was highest. Serum NUCB2/nesfatin-1 levels on embryonic day 21 and postnatal day 1 were lower than serum NUCB2/nesfatin-1 levels of adults and neonates at postnatal days 13, 20 and 27, gradually increasing with growth, suggesting an increase in its production and secretion from tissues including the gastrointestinal tract and pancreas. Our findings indicate that NUCB2/nesfatin-1 colocalizes with insulin in the islet β-cells at all developmental stages, but the percentage of colocalization varies in an age-dependent manner. These findings suggest that NUCB2/nesfatin-1 has potential age- and tissue-specific role in the developmental physiology of rats during growth.

A novel adipocytokine, nesfatin-1 modulates peripheral arterial contractility and blood pressure in rats

Nesfatin-1 is a novel adipocytokine which exerts not only anorexigenic but also hypertensive roles through acting on hypothalamus melanocortin-3/4 receptors. Although it is logical to hypothesize that nesfatin-1 could also affect the contractile reactivity of peripheral blood vessels, it still remains to be examined. The present study was performed to test the hypothesis. In both endothelium-intact and -denuded mesenteric artery of rats, acute treatment with nesfatin-1 (10nM, 30min pretreatment) had no influence on the noradrenaline- and 5-hydroxytryptamine-induced concentration-dependent contractions. Chronic treatment of mesenteric artery with nesfatin-1 (10nM, 3days) using organ-culture method had also no influence on the agonists-induced contractions. In contrast, nesfatin-1 (10nM, 30min) significantly inhibited the sodium nitroprusside (SNP)-induced relaxations of smooth muscle in mesenteric artery. A membrane permeable cyclic GMP (cGMP) analog, 8-bromo-cGMP-induced relaxations were not affected by nesfatin-1. Consistently, the SNP-induced cGMP production in smooth muscle was impaired by nesfatin-1. Intravenous application of nesfatin-1 to rats not only increased blood pressure but also impaired the SNP-induced decreases in blood pressure. The present study for the first time reveals that nesfatin-1 affects peripheral arterial blood vessel and inhibits the nitric oxide donor-induced smooth muscle relaxations via impairing the cGMP production. The results are the first to demonstrate that nesfatin-1 modulates blood pressure through directly acting on peripheral arterial resistance.

Peripheral oxytocin suppresses food intake and causes weight loss in diet-induced obese rats

Growing evidence suggests that oxytocin plays an important role in the regulation of energy balance and that central oxytocin administration induces weight loss in diet-induced obese (DIO) animals. To gain a better understanding of how oxytocin mediates these effects, we examined feeding and neuronal responses to oxytocin in animals rendered obese following exposure to either a high-fat (HFD) or low-fat diet (LFD). Our findings demonstrate that peripheral administration of oxytocin dose-dependently reduces food intake and body weight to a similar extent in rats maintained on either diet. Moreover, the effect of oxytocin to induce weight loss remained intact in leptin receptor-deficient Koletsky (fa(k)/fa(k)) rats relative to their lean littermates. To determine whether systemically administered oxytocin activates hindbrain areas that regulate meal size, we measured neuronal c-Fos induction in the nucleus of the solitary tract (NTS) and area postrema (AP). We observed a robust neuronal response to oxytocin in these hindbrain areas that was unexpectedly increased in rats rendered obese on a HFD relative to lean, LFD-fed controls. Finally, we report that repeated daily peripheral administration of oxytocin in DIO animals elicited a sustained reduction of food intake and body weight while preventing the reduction of energy expenditure characteristic of weight-reduced animals. These findings extend recent evidence suggesting that oxytocin circumvents leptin resistance and induces weight-loss in DIO animals through a mechanism involving activation of neurons in the NTS and AP, key hindbrain areas for processing satiety-related inputs.

Minireview: nesfatin-1--an emerging new player in the brain-gut, endocrine, and metabolic axis

Nesfatin-1 is a recently identified 82-amino-acid peptide derived from the precursor protein, nucleobindin2 (NUCB2). The brain distribution of NUCB2/nesfatin-1 at the mRNA and protein level along with functional studies in rodents support a role for NUCB2/nesfatin-1 as a novel satiety molecule acting through leptin-independent mechanisms. In addition, nesfatin-1 induces a wide spectrum of central actions to stimulate the pituitary-adrenal axis and sympathetic nervous system and influences visceral functions and emotion. These central actions combined with the activation of NUCB2/nesfatin-1 neurons in the brain by various stressors are indicative of a role in the adaptive response under stressful conditions. In the periphery, evidence is mounting that nesfatin-1 exerts a direct glucose-dependent insulinotropic action on β-cells of the pancreatic islets. However, the cellular mechanisms of nesfatin-1's action remain poorly understood, partly because the receptor through which nesfatin-1 exerts its pleiotropic actions is yet to be identified.

Nutrient responsive nesfatin-1 regulates energy balance and induces glucose-stimulated insulin secretion in rats

Nesfatin-1 is a recently discovered anorexigen, and we first reported nesfatin-like immunoreactivity in the pancreatic β-cells. The aim of this study was to characterize the effects of nesfatin-1 on whole-body energy homeostasis, insulin secretion, and glycemia. The in vivo effects of continuous peripheral delivery of nesfatin-1 using osmotic minipumps on food intake and substrate partitioning were examined in ad libitum-fed male Fischer 344 rats. The effects of nesfatin-1 on glucose-stimulated insulin secretion (GSIS) were examined in isolated pancreatic islets. L6 skeletal muscle cells and isolated rat adipocytes were used to assess the effects of nesfatin-1 on basal and insulin-mediated glucose uptake as well as on major steps of insulin signaling in these cells. Nesfatin-1 reduced cumulative food intake and increased spontaneous physical activity, whole-body fat oxidation, and carnitine palmitoyltransferase I mRNA expression in brown adipose tissue but did not affect uncoupling protein 1 mRNA in the brown adipose tissue. Nesfatin-1 significantly enhanced GSIS in vivo during an oral glucose tolerance test and improved insulin sensitivity. Although insulin-stimulated glucose uptake in L6 muscle cells was inhibited by nesfatin-1 pretreatment, basal and insulin-induced glucose uptake in adipocytes from nesfatin-1-treated rats was significantly increased. In agreement with our in vivo results, nesfatin-1 enhanced GSIS from isolated pancreatic islets at both normal (5.6 mM) and high (16.7 mM), but not at low (2 mM), glucose concentrations. Furthermore, nesfatin-1/nucleobindin 2 release from rat pancreatic islets was stimulated by glucose. Collectively, our data indicate that glucose-responsive nesfatin-1 regulates insulin secretion, glucose homeostasis, and whole-body energy balance in rats.

Lipopolysaccharide increases gastric and circulating NUCB2/nesfatin-1 concentrations in rats

Bacterial lipopolysaccharide (LPS) is an established animal model to study the innate immune response to Gram-negative bacteria mimicking symptoms of infection including reduction of food intake. LPS decreases acyl ghrelin associated with decreased concentrations of circulating ghrelin-O-acyltransferase (GOAT) likely contributing to the anorexigenic effect. We also recently described the prominent expression of the novel anorexigenic hormone, nucleobindin2 (NUCB2)/nesfatin-1 in gastric X/A-like cells co-localized with ghrelin in different pools of vesicles. To investigate whether LPS would affect gastric and circulating NUCB2/nesfatin-1 concentration, ad libitum fed rats were equipped with an intravenous (iv) catheter. LPS was injected intraperitoneally (ip, 100μg/kg) and blood was withdrawn before and at 2, 5, 7 and 24h post injection and processed for NUCB2/nesfatin-1 radioimmunoassay. Gastric corpus was collected to measure NUCB2 mRNA expression by RT-qPCR and NUCB2/nesfatin-1 protein concentration by Western blot. Injection of LPS increased plasma NUCB2/nesfatin-1 concentrations by 43%, 78% and 62% compared to vehicle at 2h, 5h and 7h post injection respectively (p<0.05) and returned to baseline at 24h. The plasma NUCB2/nesfatin-1 increase at 2h was associated with increased corpus NUCB2 mRNA expression (p<0.01), whereas NUCB2 mRNA was not detectable in white blood cells. Likewise, gastric NUCB2 protein concentration was increased by 62% after LPS compared to vehicle (p<0.01). These data show that gastric NUCB2 production and release are increased in response to LPS. These changes are opposite to those of ghrelin in response to LPS supporting a differential gastric regulation of NUCB2/nesfatin-1 and ghrelin expression derived from the same cell by immune challenge.

Melanocortin control of energy balance: evidence from rodent models

Regulation of energy balance is extremely complex, and involves multiple systems of hormones, neurotransmitters, receptors, and intracellular signals. As data have accumulated over the last two decades, the CNS melanocortin system is now identified as a prominent integrative network of energy balance controls in the mammalian brain. Here, we will review findings from rat and mouse models, which have provided an important framework in which to study melanocortin function. Perhaps most importantly, this review attempts for the first time to summarize recent advances in our understanding of the intracellular signaling pathways thought to mediate the action of melanocortin neurons and peptides in control of longterm energy balance. Special attention will be paid to the roles of MC4R/MC3R, as well as downstream neurotransmitters within forebrain and hindbrain structures that illustrate the distributed control of melanocortin signaling in energy balance. In addition, distinctions and controversy between rodent species will be discussed.

Localization of nesfatin-1 neurons in the mouse brain and functional implication

Nesfatin-1 reduces food intake when injected centrally in rodents. We recently described wide distribution of nucleobindin2 (NUCB2)/nesfatin-1 immunoreactivity in rat brain autonomic nuclei activated by various stressors. We used C57BL/6 mice to localize brain NUCB2/nesfatin-1 immunoreactivity and assessed activation of NUCB2/nesfatin 1 neurons after water avoidance stress (WAS). Gastric emptying of a non-nutrient liquid was also determined. NUCB2/nesfatin-1 immunoreactivity was detected in cortical areas including piriform, insular, cingulate and somatomotor cortices, the limbic system including amygdaloid nuclei, hippocampus and septum, the basal ganglia, bed nucleus of the stria terminalis, the thalamus including paraventricular and parafascicular nuclei, the hypothalamus including supraoptic, periventricular, paraventricular (PVN), arcuate nuclei and ventromedial and lateral hypothalamic areas. Intensely labeled NUCB2/nesfatin-1 neurons were detected in a previously undefined region which we named intermediate dorsomedial hypothalamus. In the brainstem, NUCB2/nesfatin-1 immunoreactivity was detected in the raphe nuclei, Edinger-Westphal nucleus, locus coeruleus (LC), lateral parabrachial nucleus, ventrolateral medulla (VLM) and dorsal vagal complex. WAS induced Fos expression in 35% of NUCB2/nesfatin-1-immunoreactive neurons in the PVN, 50% in the LC, 54% in the rostral raphe pallidus, 58% in the VLM, 39% in the middle part of the nucleus of the solitary tract (NTS) and 33% in the caudal NTS. Nesfatin-1 injected intracerebroventricularly significantly decreased gastric emptying. These data showed that NUCB2/nesfatin-1 immunoreactivity is distributed in mouse brain areas involved in the regulation of stress response and visceral functions activated by an acute psychological stressor suggesting that nesfatin-1 might play a role in the efferent component of the stress response.

Nesfatin-1: a novel inhibitory regulator of food intake and body weight

The protein nucleobindin 2 (NUCB2) or NEFA (DNA binding/EF-hand/acidic amino acid rich region) was identified over a decade ago and implicated in intracellular processes. New developments came with the report that post-translational processing of hypothalamic NUCB2 may result in nesfatin-1, nesfatin-2 and nesfatin-3 and convergent studies showing that nesfatin-1 and full length NUCB2 injected in the brain potently inhibit the dark phase food intake in rodents including leptin receptor deficient Zucker rats. Nesfatin-1 also reduces body weight gain, suggesting a role as a new anorexigenic factor and modulator of energy balance. In light of the obesity epidemic and its associated diseases, underlying new mechanisms regulating food intake may be promising targets in the drug treatment of obese patients particularly as the vast majority of them display reduced leptin sensitivity or leptin resistance while nesfatin-1's mechanism of action is leptin independent. Although much progress on the localization of NUCB2/nesfatin-1 in the brain and periphery as well as on the understanding of nesfatin-1's anorexic effect have been achieved during the past three years, several important mechanisms have yet to be unraveled such as the identification of the nesfatin-1 receptor and the regulation of NUCB2 processing and nesfatin-1 release.

Stressor-responsive central nesfatin-1 activates corticotropin-releasing hormone, noradrenaline and serotonin neurons and evokes hypothalamic-pituitary-adrenal axis

A recently discovered satiety molecule, nesfatin-1, is localized in neurons of the hypothalamus and brain stem and colocalized with stress-related substances, corticotropin-releasing hormone (CRH), oxytocin, proopiomelanocortin, noradrenaline (NA) and 5-hydroxytryptamine (5-HT). Intracerebroventricular (icv) administration of nesfatin-1 produces fear-related behaviors and potentiates stressor-induced increases in plasma adrenocorticotropic hormone (ACTH) and corticosterone levels in rats. These findings suggest a link between nesfatin-1 and stress. In the present study, we aimed to further clarify the neuronal network by which nesfatin-1 could induce stress responses in rats. Restraint stress induced c-Fos expressions in nesfatin-1-immunoreactive neurons in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus, and in the nucleus of solitary tract (NTS), locus coeruleus (LC) and dorsal raphe nucleus (DR) in the brain stem, without altering plasma nesfatin-1 levels. Icv nesfatin-1 induced c-Fos expressions in the PVN, SON, NTS, LC, DR and median raphe nucleus, including PVN-CRH, NTS-NA, LC-NA and DR-5-HT neurons. Nesfatin-1 increased cytosolic Ca²⁺ concentration in the CRH-immunoreactive neurons isolated from PVN. Icv nesfatin-1 increased plasma ACTH and corticosterone levels. These results indicate that the central nesfatin-1 system is stimulated by stress and activates CRH, NA and 5-HT neurons and hypothalamic-pituitary-adrenal axis, evoking both central and peripheral stress responses.

Neuronostatin acts in brain to biphasically increase mean arterial pressure through sympatho-activation followed by vasopressin secretion: the role of melanocortin receptors

Neuronostatin is a recently described neuropeptide that is derived from the somatostatin preprohormone. We have shown previously that neuronostatin led to a biphasic, dose-related increase in mean arterial pressure when injected into the lateral cerebroventricle of adult, male rats. Because neuronostatin depolarized both magnocellular and parvocellular, paraventricular nucleus neurons in hypothalamic slice preparations, we hypothesized that neuronostatin elevated mean arterial pressure first by stimulating sympathetic nervous system activity followed by the release of a pressor hormone, specifically vasopressin. We found that the first phase of neuronostatin-induced increase in mean arterial pressure was reversed by pretreatment with phentolamine, indicating that phase 1 was, indeed, due to an increase in sympathetic activity. We also found that centrally injected neuronostatin led to a dose-related increase in vasopressin secretion in a time course consistent with the peak of the second phase. Furthermore, the second phase of arterial pressure elevation was reversed by pretreatment with a vasopressin 1 receptor antagonist, indicating that phase 2 was likely due to an increase in vasopressin secretion. We previously have shown that the anorexigenic and antidipsogenic effects of neuronostatin were reversed by pretreatment with the melanocortin 3/4 receptor antagonist, SHU9119, so we evaluated the ability of SHU9119 to reverse the effects of neuronostatin on MAP and vasopressin secretion. We found that SHU9119 abrogated the second phase of neuronostatin-induced increase in MAP and neuronostatin-induced vasopressin secretion, indicating that neuronostatin acts through the central melanocortin system to increase vasopressin release, ultimately leading to an elevation in MAP.

Centrally administered nesfatin-1 inhibits feeding behaviour and gastroduodenal motility in mice

Nesfatin-1 was recently identified as a peptide with anorexigenic effects that is localized in the hypothalamus and adipocytes. Not much is known about the effect of nesfatin-1 on gut motility. Food intake was measured after intracerebroventricular administration of nesfatin-1 in food-deprived mice. Antral and duodenal motility was assessed by using a manometric method in conscious fed mice. We found that centrally administered nesfatin-1 decreased food intake and inhibited gastroduodenal motility in mice. These results suggest that nesfatin-1 influences gut motility and feeding behaviour.

Central nesfatin-1 reduces the nocturnal food intake in mice by reducing meal size and increasing inter-meal intervals

Nesfatin-1 is well established to reduce food intake upon brain injection in rats, while in mice its anorexigenic action and brain expression are largely unexplored. We characterized the influence of intracerebroventricular (icv) and peripheral (intraperitoneal, ip, subcutaneous, sc) injection of nesfatin-1 on dark phase ingestive behavior using an automated feeding monitoring system and co-localized NUCB2/nesfatin-1 immunoreactivity in the associated brain areas. Nesfatin-1 (0.3, 1 or 3 μg/mouse, icv) caused a dose-related reduction of 4-h dark phase food intake by 13%, 27%, and 46% respectively. Nesfatin-1 (3 μg/mouse, icv) action had a 2-h delayed onset, 82% peak inhibition occurring at 3-4h post-injection and was long lasting (30% reduction for 12h period post-injection). Nesfatin-1 (3 μg/mouse, icv)-treated mice had a 46% lower meal frequency associated with 2-times longer inter-meal intervals and a 35% reduction in meal size compared to vehicle during the 1-4h post-injection (p<0.05). NUCB2/nesfatin-1-immunopositive neurons were found in hypothalamic (supraoptic, paraventricular, arcuate, dorsomedial, lateral) and brainstem (dorsal vagal complex) feeding regulatory nuclei. When injected peripherally, neither food intake nor feeding microstructure parameters were altered. These results demonstrate that NUCB2/nesfatin-1 is prominently expressed in mouse hypothalamus and medulla and acts in the brain to curtail the dark phase feeding by inducing satiation and satiety indicated by reduced meal size and prolonged inter-meal intervals respectively. The lack of nesfatin-1 effect when injected peripherally at a 23-times higher dose indicates a primarily central site of the anorexigenic action for nesfatin-1 in mice.

Molecular, cellular and physiological evidences for the anorexigenic actions of nesfatin-1 in goldfish

Background

Nesfatin-1 is a recently discovered anorexigen encoded in the precursor peptide, nucleobindin-2 (NUCB2) in mammals. To date, nesfatin-1 has not been described in any non-mammalian species, although some information is available in the sequenced genomes of several species. Our objective was to characterize nesfatin-1 in fish.

Methodology/Principal Findings

In the present study, we employed molecular, immunohistochemical, and physiological studies to characterize the structure, distribution, and appetite regulatory effects of nesfatin-1 in a non-mammalian vertebrate. A very high conservation in NUCB2 sequences, especially in the nesfatin-1 region was found in lower vertebrates. Abundant expression of NUCB2 mRNA was detected in several tissues including the brain and liver of goldfish. Nesfatin-1-like immunoreactive cells are present in the feeding regulatory nucleus of the hypothalamus and in the gastrointestinal tract of goldfish. Approximately 6-fold increase in NUCB2 mRNA levels was found in the liver after 7-day food-deprivation, and a similar increase was also found after short-term fasting. This points toward a possible liver specific role for NUCB2 in the control of metabolism during food-deprivation. Meanwhile, ∼2-fold increase at 1 and 3 h post-feeding and an ∼3-fold reduction after a 7-day food-deprivation was observed in NUCB2 mRNA in the goldfish hypothalamus. In vivo, a single intraperitoneal injection of the full-length native (goldfish; gf) nesfatin-1 at a dose of 50 ng/g body weight induced a 23% reduction of food intake one hour post-injection in goldfish. Furthermore, intracerebroventricular injection of gfnesfatin-1 at a dose of 5 ng/g body weight resulted in ∼50% reduction in food intake.

Conclusions/Significance

Our results provide molecular, anatomical and functional evidences to support potential anorectic and metabolic roles for endogenous nesfatin-1 in goldfish. Collectively, we provide novel information on NUCB2 in non-mammals and an anorexigenic role for nesfatin-1 in goldfish.

The melanocortins, not oxytocin, mediate the anorexigenic and antidipsogenic effects of neuronostatin

Neuronostatin, a recently discovered peptide derived from the somatostatin preprohormone, significantly inhibited both food and water intake when administered centrally in adult male rats. Because neuronostatin is highly produced in the hypothalamus, an area of the brain through which important feeding circuits, including the central melanocortin system, communicate, we sought to determine if the anorexigenic and antidipsogenic effects of neuronostatin would be reversed by pretreatment with the melanocortin 3/4 receptor antagonist, SHU9119. SHU9119 pretreatment reversed the effect of neuronostatin on both food and water intake. We have shown recently that the central oxytocin system is a potential downstream mediator of the anorexignic action of alpha-MSH. We therefore tested whether the effects of neuronostatin also were dependent upon central oxytocin receptors. Neuronostatin-induced anorexia was not reversed by pretreatment with the oxytocin receptor antagonist, OVT, suggesting that neuronostatin acts through a unique subset of POMC neurons that do not signal via central oxytocin receptors.

Nesfatin-1--role as possible new potent regulator of food intake

Nesfatin-1 is an 82 amino acid peptide recently discovered in the brain which is derived from nucleobindin2 (NUCB2), a protein that is highly conserved across mammalian species. Nesfatin-1 has received much attention over the past two years due to its reproducible food intake-reducing effect that is linked with recruitment of other hypothalamic peptides regulating feeding behavior. A growing amount of evidence also supports that various stressors activate fore- and hindbrain NUCB2/nesfatin-1 circuitries. In this review, we outline the central nervous system distribution of NUCB2/nesfatin-1, and recent developments on the peripheral expression of NUCB2/nesfatin-1, in particular its co-localization with ghrelin in gastric X/A-like cells and insulin in ss-cells of the endocrine pancreas. Functional studies related to the characteristics of nesfatin-1's inhibitory effects on dark phase food intake are detailed as well as the central activation of NUCB2/nesfatin-1 immunopositive neurons in the response to psychological, immune and visceral stressors. Lastly, potential clinical implications of targeting NUCB2/nesfatin-1 signaling and existing gaps in knowledge to ascertain the role and mechanisms of action of nesfatin-1 are presented.