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

Interactions between nesfatin-1 and the autonomic nervous system-An overview

Nesfatin-1, an 82-amino acid polypeptide derived from the precursor protein nucleobindin-2 (NUCB2), was first discovered in 2006 in the rat hypothalamus. The effects and distribution of nesfatin-1 immunopositive neurons in the brain and spinal cord point towards a role of NUCB2/nesfatin-1 in autonomic regulation. Therefore, studies which have been conducted to investigate the interplay between nesfatin-1 and the autonomic nervous system were examined, and the outcomes of this research were summarized. NUCB2/nesfatin-1 immunoreactivity is widely distributed in autonomic centers of the brain and spinal cord in both rodents and humans. In several regions of the hypothalamus, midbrain and brainstem, nesfatin-1 modulates autonomic functions. On the other hand, the autonomic nervous system also influences the activity of nesfatin-1 neurons. Here, the vagus nerve seems to be a crucial factor in the regulation of nesfatin-1. In summary, although data here is still sparse, there is a clear interplay between nesfatin-1 and the autonomic nervous system, the precise clarification of which still requires further research to gain more insight into these complex relationships.

Nesfatin-1-like peptide is a negative regulator of cardiovascular functions in zebrafish and goldfish

Nucleobindins (NUCB1 and NUCB2) were originally identified as calcium and DNA binding proteins. Nesfatin-1 (NEFA/nucleobindin-2-Encoded Satiety and Fat-Influencing proteiN-1) is an 82 amino acid anorexigenic peptide encoded in the N-terminal region of NUCB2. We have shown that nesfatin-1 is a cardiosuppressor in zebrafish. Both NUCB1 and NUCB2 possess a -very highly conserved bioactive core. It was found that a nesfatin-1-like peptide (NLP) encoded in NUCB1 suppresses food intake in fish. In this research, we investigated whether NLP has nesfatin-1-like effects on cardiovascular functions. NUCB1/NLP-like immunoreactivity was found in the atrium and ventricle of the heart and skeletal muscle of zebrafish. Intraperitoneal injection (IP) of either zebrafish NLP or rat NLP suppressed cardiac functions in both zebrafish and goldfish. Irisin and RyR1b mRNA expression was downregulated by NLP in zebrafish cardiac and skeletal muscles. However, cardiac ATP2a2 mRNA expression was elevated after NLP injection. Administration of scrambled NLP did not affect irisin, RyR1b or ATP2a2 mRNA expression in zebrafish. Together, these results implicate NLP as a suppressor of cardiovascular physiology in zebrafish and goldfish.

A comparative account of nesfatin-1 in vertebrates

Nesfatin-1 was discovered as an anorexigenic peptide derived from proteolytic cleavage of the prepropeptide, nucleobindin 2 (NUCB2). It is widely expressed in central as well as peripheral tissues and is known to have pleiotropic effects such as regulation of feeding, reproduction, cardiovascular functions and maintenance of glucose homeostasis. In order to execute its multifaceted role, nesfatin-1 employs diverse signaling pathways though its receptor has not been identified till date. Further, nesfatin-1 is reported to be under the regulatory effect of feeding state, nutritional status as well as several metabolic and reproductive hormones. This peptide has also been associated with variety of human diseases, especially metabolic, reproductive, cardiovascular and mental disorders. The current review is aimed to present a consolidated picture and highlight lacunae for further investigation in order to develop a deeper comprehensive understanding on physiological significance of nesfatin-1 in vertebrates.

The goldfish Carassius auratus: an emerging animal model for comparative cardiac research

The use of unconventional model organisms is significantly increasing in different fields of research, widely contributing to advance life sciences understanding. Among fishes, the cyprinid Carassius auratus (goldfish) is largely used for studies on comparative and evolutionary endocrinology, neurobiology, adaptive and conservation physiology, as well as for translational research aimed to explore mechanisms that may be useful in an applicative biomedical context. More recently, the research possibilities offered by the goldfish are further expanded to cardiac studies. A growing literature is available to illustrate the complex networks involved in the modulation of the goldfish cardiac performance, also in relation to the influence of environmental signals. However, an overview on the existing current knowledge is not yet available. By discussing the mechanisms that in C. auratus finely regulate the cardiac function under basal conditions and under environmental challenges, this review highlights the remarkable flexibility of the goldfish heart in relation not only to the basic morpho-functional design and complex neuro-humoral traits, but also to its extraordinary biochemical-metabolic plasticity and its adaptive potential. The purpose of this review is also to emphasize the power of the heart of C. auratus as an experimental tool useful to investigate mechanisms that could be difficult to explore using more conventional animal models and complex cardiac designs.

Colocalized neurotransmitters in the hindbrain cooperate in adaptation to chronic hypernatremia

Chronic hypernatremia activates the central osmoregulatory mechanisms and inhibits the function of the hypothalamic-pituitary-adrenal (HPA) axis. Noradrenaline (NE) release into the periventricular anteroventral third ventricle region (AV3V), the supraoptic (SON) and hypothalamic paraventricular nuclei (PVN) from efferents of the caudal ventrolateral (cVLM) and dorsomedial (cDMM) medulla has been shown to be essential for the hypernatremia-evoked responses and for the HPA response to acute restraint. Notably, the medullary NE cell groups highly coexpress prolactin-releasing peptide (PrRP) and nesfatin-1/NUCB2 (nesfatin), therefore, we assumed they contributed to the reactions to chronic hypernatremia. To investigate this, we compared two models: homozygous Brattleboro rats with hereditary diabetes insipidus (DI) and Wistar rats subjected to chronic high salt solution (HS) intake. HS rats had higher plasma osmolality than DI rats. PrRP and nesfatin mRNA levels were higher in both models, in both medullary regions compared to controls. Elevated basal tyrosine hydroxylase (TH) expression and impaired restraint-induced TH, PrRP and nesfatin expression elevations in the cVLM were, however, detected only in HS, but not in DI rats. Simultaneously, only HS rats exhibited classical signs of chronic stress and severely blunted hormonal reactions to acute restraint. Data suggest that HPA axis responsiveness to restraint depends on the type of hypernatremia, and on NE capacity in the cVLM. Additionally, NE and PrRP signalization primarily of medullary origin is increased in the SON, PVN and AV3V in HS rats. This suggests a cooperative action in the adaptation responses and designates the AV3V as a new site for PrRP's action in hypernatremia.

Nesfatin-1 in cardiovascular orchestration: From bench to bedside

Since the discovery of Nesfatin-1 in 2006, intensive research was finalized to further and deeper investigate the precise physiological functions of the peptide at both central and peripheral levels, rapidly enriching the knowledge regarding this intriguing molecule. Nesfatin-1 is a hypothalamic peptide generated via the post-translational processing of its precursor Nucleobindin 2, a protein supposed to play a role in many biological processes thanks to its ability to bind calcium and to interact with different intracellular proteins. Nesfatin-1 is mainly known for its anorexic properties, but it also controls water intake and glucose homeostasis. Recent experimental evidences describe the peptide as a possible direct/indirect orchestrator of central and peripheral cardiovascular control. A specific Nesfatin-1 receptor still remains to be identified although numerous studies suggest that the peptide activates extra- and intracellular regulatory pathways by involving several putative binding sites. The present paper was designed to systematically review the latest findings about Nesfatin-1, focusing on its cardiovascular regulatory properties under normal and physiopathological conditions. The hope is to provide the conceptual basis to consider Nesfatin-1 not only as a pleiotropic neuroendocrine molecule, but also as a homeostatic modulator of the cardiovascular function and with a crucial role in cardiovascular diseases.

Can Nesfatin-1 Predict Hypertension in Obese Children?

Objective

The prevalence of childhood obesity is increasing and leads to co-morbidities such as hypertension. However, it is still not clear why some obese individuals are hypertensive and others not. Nesfatin-1 is a recently discovered anorexigenic peptide which also has effects on blood pressure (BP). Our aim was to evaluate the relationship between obesity-related hypertension and Nesfatin-1.

Methods

This cross-sectional study comprised 87 obese children. The patients were divided into two groups; hypertensive (n=30) and normotensive (n=57) obese. The American Academy of Pediatrics guidelines were used to diagnose hypertension. Blood samples were collected after 12 hours of fasting to investigate Nesfatin-1 concentrations. We also evaluated serum trace elements in addition to the routine blood tests.

Results

Body mass index (BMI), weight and serum Nesfatin-1 concentrations were higher in the hypertensive group (p=0.002, p=0.001, and p=0.007, respectively). There was no difference between serum zinc levels, but Copper (Cu) levels were significantly lower in the hypertensive group (p=0.248, p=0.007, respectively). There were positive correlations between BP and BMI and weight Z-scores and a negative correlation with Cu. The optimal cut-off value of Nesfatin-1 to predict hypertension was found to be >1.8 ng/mL, with a specificity of 71.9% and a sensitivity of 96.7% [area under the curve=0.703, 95% confidence interval (CI): 0.577-0.809; p=0.002]. In multiple logistic regression analysis Nesfatin-1 [Odds ratio (OR)=1.103, 95% CI: 1.039-1.171; p=0.001], Cu (OR=0.947, 95% CI: 0.915-0.979; p=0.001) and BMI for age Z-score (OR=56.277, 95% CI: 5.791-546.907; p=0.001) still remained significant predictors of hypertension.

Conclusion

Nesfatin-1 levels are higher and are an independent predictor of hypertension in obese subjects.

Exploring cardiac plasticity in teleost: the role of humoral modulation

The fish heart represents an established natural model for evaluating basic mechanisms of the coordinated physiological reactions which maintain cardiac steady-state. This is due to its relatively simple design, but also to its multilevel morpho-functional flexibility which allows adequate responses to a variety of intrinsic (body size and shape, swimming performance, etc.), and extrinsic (temperature, salinity, oxygen level, water chemistry, etc.) factors related to the animal life style. Nowadays, although many gaps are still present, a huge literature is available about the mechanisms that fine-tune fish cardiac performance, particularly in relation to the influence exerted by substances possessing cardio-modulatory properties. Based on these premises, this review will provide an overview of the existing current knowledge regarding the humoral control of cardiac performance in fish. The role of both classic (i.e. catecholamines, angiotensin II and natriuretic peptides), and emerging cardioactive substances (i.e. the chromogranin-A-derived peptides vasostatins, catestatin and serpinin) will be illustrated and discussed. Moreover, an example of cardiomodulation elicited by peptides (e.g., nesfatin-1) associated to the regulation of feeding and metabolism will be provided. The picture will hopefully emphasize the complex circuits that sustain fish cardiac performance, also highliting the power of the teleost heart as an experimental model to deciphering mechanisms that could be difficult to explore in more elaborated cardiac morpho-functional designs.

Centrally and peripherally injected nesfatin-1-evoked respiratory responses

Nesfatin-1, which is an anorexiogenic peptide, plays a crucial role as a neurotransmitter and/or neuromodulator in the central nervous system for cardiovascular control and energy balance etc. It is expressed abundantly in multiple brain nuclei including central respiratory control areas such as nucleus tractus solitarius, nucleus ambiguous, dorsal vagal complex, dorsal motor nucleus of the vagus nerve, and hypothalamus. To date, no previous studies have been found to report nesfatin-1-evoked respiratory effects. Therefore, the present study was designed to investigate the possible impacts of centrally and/or peripherally injected nesfatin-1 on respiratory parameters in either 12h-fasted or fed-ad libitum rats. Intracerebroventricular (ICV) administration of nesfatin-1 provoked significant hyperventilation by increasing tidal volume (TV), respiratory rate (RR) and respiratory minute ventilation (RMV) in both the 12h-fasted and the fed-ad libitum Spraque Dawley rats in dose- and time- dependent manner. Moreover, the hyperventilatory effects of centrally injected nesfatin-1 were more potent in the fed-ad libitum rats. Intravenous injection of nesfatin-1 induced a significant rise in RR and RMV, but not in TV, in the fed-ad libitum rats. In conclusion, these findings plainly report that both centrally and/or peripherally injected nesfatin-1 induces significant hyperventilatory effects in the 12h-fasted and the fed-ad libitum rats. These hyperventilatory effects of nesfatin-1 might show a discrepancy according to the food intake of the rats and the delivery method of the peptide.

Current Understanding of the Role of Nesfatin-1

Nesfatin-1 was discovered in 2006 and implicated in the regulation of food intake. Subsequently, its widespread central and peripheral distribution gave rise to additional effects. Indeed, a multitude of actions were described, including modulation of gastrointestinal functions, glucose and lipid metabolism, thermogenesis, mediation of anxiety and depression, as well as cardiovascular and reproductive functions. Recent years have witnessed a great increase in our knowledge of these effects and their underlying mechanisms, which will be discussed in the present review. Lastly, gaps in knowledge will be highlighted to foster further studies.

Novel transmitters in brain stem vagal neurocircuitry: new players on the pitch

The last few decades have seen a major increase in the number of neurotransmitters and neuropeptides recognized as playing a role in brain stem neurocircuits, including those involved in homeostatic functions such as stress responsiveness, gastrointestinal motility, feeding, and/or arousal/wakefulness. This minireview will focus on the known physiological role of three of these novel neuropeptides, i.e., apelin, nesfatin-1, and neuropeptide-S, with a special emphasis on their hypothetical roles in vagal signaling related to gastrointestinal motor functions.

Nesfatin-1 promotes VSMC migration and neointimal hyperplasia by upregulating matrix metalloproteinases and downregulating PPARγ

The dedifferentiation, proliferation and migration of vascular smooth muscle cells (VSMCs) are essential in the progression of hypertension, atherosclerosis and intimal hyperplasia. Nesfatin-1 is a potential modulator in cardiovascular functions. However, the role of nesfatin-1 in VSMC biology has not been explored. The present study was designed to determine the regulatory role of nesfatin-1 in VSMC proliferation, migration and intimal hyperplasia after vascular injury. Herein, we demonstrated that nesfatin-1 promoted VSMC phenotype switch from a contractile to a synthetic state, stimulated VSMC proliferation and migration in vitro. At the molecular level, nesfatin-1 upregulated the protein and mRNA levels, as well as the promoter activities of matrix metalloproteinase 2 (MMP-2) and MMP-9, but downregulated peroxisome proliferator-activated receptor γ (PPARγ) levels and promoter activity in VSMCs. Blockade of MMP-2/9 or activation of PPARγ prevented the nesfatin-1-induced VSMC proliferation and migration. In vivo, knockdown of nesfatin-1 ameliorated neointima formation following rat carotid injury. Taken together, our results indicated that nesfatin-1 stimulated VSMC proliferation, migration and neointimal hyperplasia by elevating MMP2/MMP-9 levels and inhibiting PPARγ gene expression.

Serum Cytokine Levels are related to Nesfatin-1/NUCB2 Expression in the Implantation Sites of Spontaneous Abortion Model of CBA/j × DBA/2 Mice

The process of spontaneous abortion involves a complex mechanism with various cytokines, growth factors, and hormones during the pregnancy. However, the mechanism underlying spontaneous abortion by pro- and anti-inflammatory cytokines in the serum during the pregnancy is not fully understood. Therefore, the purpose of this study was to examine the relationship between the serum levels of pro- and anti-inflammatory cytokines and spontaneous abortion using the CBA/j × DBA/2 mouse model. Serum levels of pro-inflammatory cytokines, such as IFN-γ, IL-1α and TNF-α were not increased in abortion model mice, but anti-inflammatory cytokines, such as IL-4, IL-13 and IL-1ra were decreased compared to normal pregnant mice. In addition, serum levels of chemokine, such as SDF-1, G-CSF, M-CSF, IL-16, KC and MCP-1 were decreased in abortion model mice compared to normal pregnant mice. However, the expression levels of nesfatin-1/NUCB2 mRNA and protein in the uteri of implantation sites were significantly higher in abortion model mice than normal pregnant mice. These results suggest that uterine nesfatin-1/NUCB2 expression may be down-regulated by inflammatory cytokines and chemokines in the serum of pregnant mice. Moreover, this study suggests the possibility that nesfatin-1/NUCB2 expressed in the implantation sites may be associated with the maintenance of pregnancy.

Nesfatin-1: functions and physiology of a novel regulatory peptide

Nesfatin-1 was identified in 2006 as a potent anorexigenic peptide involved in the regulation of homeostatic feeding. It is processed from the precursor-peptide NEFA/nucleobindin 2 (NUCB2), which is expressed both in the central nervous system as well as in the periphery, from where it can access the brain via non-saturable transmembrane diffusion. In hypothalamus and brainstem, nesfatin-1 recruits the oxytocin, the melancortin and other systems to relay its anorexigenic properties. NUCB2/nesfatin-1 peptide expression in reward-related areas suggests that nesfatin-1 might also be involved in hedonic feeding. Besides its initially discovered anorexigenic properties, over the last years, other important functions of nesfatin-1 have been discovered, many of them related to energy homeostasis, e.g. energy expenditure and glucose homeostasis. Nesfatin-1 is not only affecting these physiological processes but also the alterations of the metabolic state (e.g. fat mass, glycemic state) have an impact on the synthesis and release of NUCB2 and/or nesfatin-1. Furthermore, nesfatin-1 exerts pleiotropic actions at the level of cardiovascular and digestive systems, as well as plays a role in stress response, behavior, sleep and reproduction. Despite the recent advances in nesfatin-1 research, a putative receptor has not been identified and furthermore potentially distinct functions of nesfatin-1 and its precursor NUCB2 have not been dissected yet. To tackle these open questions will be the major objectives of future research to broaden our knowledge on NUCB2/nesfatin-1.

High-fat diet-induced downregulation of anorexic leukemia inhibitory factor in the brain stem

OBJECTIVE

High-fat diet (HFD) is known to induce low-grade hypothalamic inflammation. Whether inflammation occurs in other brain areas remains unknown. This study tested the effect of short-term HFD on cytokine gene expression and identified leukemia inhibitory factor (LIF) as a responsive cytokine in the brain stem. Thus, functional and cellular effects of LIF in the brain stem were investigated.

METHODS

Male rats were fed chow or HFD for 3 days, and then gene expression was analyzed in different brain regions for IL-1β, IL-6, TNF-α, and LIF. The effect of intracerebroventricular injection of LIF on chow intake and body weight was also tested. Patch clamp recording was performed in the nucleus tractus solitarius (NTS).

RESULTS

HFD increased pontine TNF-α mRNA while downregulating LIF in all major parts of the brain stem, but not in the hypothalamus or hippocampus. LIF injection into the cerebral aqueduct suppressed food intake without conditioned taste aversion, suggesting that LIF can induce anorexia via lower brain regions without causing malaise. In the NTS, a key brain stem nucleus for food intake regulation, LIF induced acute changes in neuronal excitability.

CONCLUSIONS

HFD-induced downregulation of anorexic LIF in the brain stem may provide a permissive condition for HFD overconsumption. This may be at least partially mediated by the NTS.

Ultrasonography reveals in vivo dose-dependent inhibition of end systolic and diastolic volumes, heart rate and cardiac output by nesfatin-1 in zebrafish

Nesfatin-1 is an 82 amino acid peptide that inhibits food intake in rodents and fish. While endogenous nesfatin-1, and its role in the regulation of food intake and hormone secretion has been reported in fish, information on cardiovascular functions of nesfatin-1 in fish is in its infancy. We hypothesized that cardiac NUCB2 expression is meal responsive and nesfatin-1 is a cardioregulatory peptide in zebrafish. NUCB2/nesfatin-1 like immunoreactivity was detected in zebrafish cardiomyocytes. Real-time quantitative PCR analysis found that the cardiac expression of NUCB2A mRNA in unfed fish decreased at 1h post-regular feeding time. Food deprivation for 7days did not change NUCB2A mRNA expression. However, NUCB2B mRNA expression was increased in the heart of zebrafish after a 7-day food deprivation. Ultrasonography of zebrafish heart at 15min post-intraperitoneal injection of nesfatin-1 (250 and 500ng/g body weight) showed a dose-dependent inhibition of end diastolic and end systolic volumes. A dose dependent decrease in heart rate and cardiac output was observed in zebrafish that received nesfatin-1, but no changes in stroke volume were found. Nesfatin-1 treatment caused a significant increase in the expression of Atp2a2a mRNA encoding the calcium-handling pump, SERCA2a, while it had no effects on the expression of calcium handling protein RyR1b encoding mRNA. Our data support cardiosuppressive effects of nesfatin-1 in zebrafish, and reveals energy availability as one determinant of cardiac NUCB2 mRNA expression.

Nesfatin-1: a new energy-regulating peptide with pleiotropic functions. Implications at cardiovascular level

Nesfatin-1 is a new energy-regulating peptide widely expressed at both central and peripheral tissues with pleiotropic effects. In the last years, the study of nesfatin-1 actions and its possible implication in the development of different diseases has created a great interest among the scientific community. In this review, we will summarize nesfatin-1 main functions, focusing on its cardiovascular implications.

Th 17 Cells and Nesfatin-1 are associated with Spontaneous Abortion in the CBA/j × DBA/2 Mouse Model

The pregnancy and abortion process involves a complex mechanism with various immune cells present in the implantation sites and several hormones associated with pregnancy, such as leptin, ghrelin and nesfatin-1. However, the mechanism underlying spontaneous abortion by maternal T helper 17 (Th17) present in the implantation sites and nesfatin-1, which is of anorexigenic hormones, is not fully understood so far. Therefore, the purpose of this study was to examine the possible roles of Th17 cells present in the implantation sites and nesfatin-1 expressed in the uterus on spontaneous abortion using the CBA/j × DBA/2 mouse model. Th17 transcription factor, ROR-γt mRNA expression was significantly increased in the abortion sites compared with the implantation sites of abortion model mice on day 14.5 and 19.5 of pregnancy. In addition, the expression levels of IL(-1)7A mRNA were significantly higher in abortion sites than in implantation sites on day 14.5 and 19.5. Moreover, the nesfatin-1/NUCB2 protein and mRNA levels were increased in abortion sites compared with levels in implantation sites of both normal pregnant and abortion model mice on day 14.5 of pregnancy. Interestingly, nesfatin- 1/NUCB2 serum levels were not changed throughout the whole pregnancy in abortion model mice, but its serum level was dramatically increased on day 14.5, and then rapidly decreased on day 19.5 in normal pregnant mice. In this study, we showed for the first time the expression of nesfatin-1/NUCB2 mRNA and protein in implantation sites during pregnancy. The present results suggest that Th17 cells in the uterus may play an important role in the period of implantation and for maintenance of pregnancy. Furthermore, the present results suggest that Th17 cells in implantation sites may be a key regulator for maintenance of pregnancy and provides evidence that activation of these cells may be regulated by nesfatin-1/NUCB2. Further study is needed to elucidate the role of nesfatin-1 expressed in the uterus during pregnancy.

Nesfatin-1 as a new positive inotrope in the goldfish (Carassius auratus) heart

The hypothalamic neuropeptide Nesfatin-1 is present in both mammals and teleosts in which it elicits anorexigenic effects. In mammals, Nesfatin-1 acts on the heart by inducing negative inotropism and lusitropism, and cardioprotection against ischemic damages. We evaluated whether in teleosts, Nesfatin-1 also influences cardiac performance. In the goldfish (Carassius auratus), mature, fully processed Nesfatin-1 was detected in brain, gills, intestine and skeletal muscle, but not in the cardiac ventricle. However, on the isolated and perfused working goldfish heart, exogenous Nesfatin-1 induced a positive inotropic effect, revealed by a dose-dependent increase of stroke volume (SV) and stroke work (SW). Positive inotropism was abolished by inhibition of adenylate cyclase (AC; MDL123330A) and cAMP-dependent kinase (PKA; KT5720), suggesting a cAMP/PKA-mediated pathway. This was confirmed by the increased cAMP concentrations revealed by ELISA on Nesfatin-1-treated hearts. Perfusion with Diltiazem, Thapsigargin and PD98059 showed the involvement of L-type calcium channels, SERCA2a pumps and ERK1/2, respectively. The role of ERK1/2 and phospholamban in Nesfatin-1-induced cardiostimulation was supported by Western blotting analysis. In conclusion, this is the first report showing that in teleosts, Nesfatin-1 potentiates mechanical cardiac performance, strongly supporting the evolutionary importance of the peptide in the control of the cardiac function of vertebrates.

Hypothalamic Nesfatin-1 Stimulates Sympathetic Nerve Activity via Hypothalamic ERK Signaling

Nesfatin-1 acts on the hypothalamus and regulates the autonomic nervous system. However, the hypothalamic mechanisms of nesfatin-1 on the autonomic nervous system are not well understood. In this study, we found that intracerebroventricular (ICV) administration of nesfatin-1 increased the extracellular signal-regulated kinase (ERK) activity in rats. Furthermore, the activity of sympathetic nerves, in the kidneys, liver, and white adipose tissue (WAT), and blood pressure was stimulated by the ICV injection of nesfatin-1, and these effects were abolished owing to pharmacological inhibition of ERK. Renal sympathoexcitatory and hypertensive effects were also observed with nesfatin-1 microinjection into the paraventricular hypothalamic nucleus (PVN). Moreover, nesfatin-1 increased the number of phospho (p)-ERK1/2-positive neurons in the PVN and coexpression of the protein in neurons expressing corticotropin-releasing hormone (CRH). Pharmacological blockade of CRH signaling inhibited renal sympathetic and hypertensive responses to nesfatin-1. Finally, sympathetic stimulation of WAT and increased p-ERK1/2 levels in response to nesfatin-1 were preserved in obese animals such as rats that were fed a high-fat diet and leptin receptor-deficient Zucker fatty rats. These findings indicate that nesfatin-1 regulates the autonomic nervous system through ERK signaling in PVN-CRH neurons to maintain cardiovascular function and that the antiobesity effect of nesfatin-1 is mediated by hypothalamic ERK-dependent sympathoexcitation in obese animals.

Nesfatin-1 - More than a food intake regulatory peptide

Nesfatin-1 was discovered a decade ago and despite the fact that it represents just one of a multitude of food intake-inhibiting factors it received increasing attention. This led to a detailed characterization of NUCB2/nesfatin-1's physiological property to reduce food intake and also gave rise to an involvement in the long term regulation of body weight, especially under conditions of obesity. In addition, studies indicated the involvement of NUCB2/nesfatin-1 in other homeostatic functions as well: glucose homeostasis, water intake, gastrointestinal functions, temperature regulation, cardiovascular functions, puberty onset and sleep. These pleiotropic actions underline the physiological relevance of this peptide. Recently, the involvement of NUCB2/nesfatin-1 in psychiatric disorders such as anxiety has been investigated giving rise to the speculation that NUCB2/nesfatin-1 represents a peptidergic link between eating and anxiety/depression disorders.

The role of centrally injected nesfatin-1 on cardiovascular regulation in normotensive and hypotensive rats

This study investigated the cardiovascular effects of nesfatin-1 in normotensive rats and animals subjected to hypotensive hemorrhage. Hemorrhagic hypotension was induced by withdrawal 2 mL blood/100 g body weight over a period of 10 min. Acute hemorrhage led to a severe and long-lasting decrease in mean arterial pressure (MAP) and heart rate (HR). Intracerebroventricularly (i.c.v.) administered nesfatin-1 (100 pmol) increased MAP in both normotensive and hemorrhaged rats. Nesfatin-1 also caused bradycardia in normotensive and tachycardia in hemorrhaged rats. Centrally injected nesfatin-1 (100 pmol, i.c.v.) also increased plasma catecholamine, vasopressin and renin concentrations in control animals and potentiated the rise in all three cardiovascular mediators produced by hemorrhage. These findings indicate that centrally administered nesfatin-1 causes a pressor response in conscious normotensive and hemorrhaged rats and suggest that enhanced sympathetic activity and elevated vasopressin and renin concentrations mediate the cardiovascular effects of the peptide.

Expression of Nesfatin-1/NUCB2 in Fetal, Neonatal and Adult Mice

Nesfatin-1/NUCB2, which is associated with the control of appetite and energy metabolism, was reported for the first time to be expressed in the hypothalamus. However, recent studies have shown that nesfatin-1/NUCB2 was expressed not only in the hypothalamus, but also in various tissues including digestive and reproductive organs. We also demonstrated that nesfatin-1/NUCB2 was expressed in the reproductive organs, pituitary gland, heart, lung, and gastrointestinal tract of the adult mouse. However, little is known about nesfatin-1/NUCB2 expression in fetal and neonatal mice. Therefore, we examined here the distribution of nesfatin-1/NUCB2 in various organs of fetal and neonatal mice and compared them with the distribution in adult mice. As a result of immunohistochemical staining, nesfatin-1/NUCB2 protein was expressed relatively higher in the lung, kidney, heart, and liver compared to other organs in the fetus. Western blot results also showed that nesfatin-1/NUCB2 protein was detected in the lung, kidney, heart, and stomach. Next, we compared the expression levels of nesfatin-1/NUCB2 mRNA in the fetus and neonate with the expression levels in both male and female adult mice. The expression levels in heart, lung, stomach, and kidney were higher compared with other organs in fetal and neonatal mice and in both male and female adult mice. Interestingly, the expression of nesfatin-1/NUCB2 mRNA in the kidney was devrepamatically increased in male and female adult mice compared to fetal and neonatal mice. These results indicate that nesfatin-1/NUCB2 may regulate the development and physiological function of mouse organs. In the future, we need more study on the function of nesfatin-1/NUCB2, which is highly expressed in the heart, lung, and kidney during mouse development.

Nesfatin-1 as a new potent regulator in reproductive system

Nesfatin-1 is a recently discovered anorexigenic peptide which is distributed in several brain areas implicated in the feeding and metabolic regulation. Recently, it has been reported that nesfatin-1 is expressed not only in brain, but also in peripheral organs such as digestive organs, adipose tissues, heart, and reproductive organs. Nesfatin-1 is markedly expressed in the pancreas, stomach and duodenum. Eventually, the nesfatin-1 expression in the digestive organs may be regulated by nutritional status, which suggests a regulatory role of peripheral nesfatin-1 in energy homeostasis. Nesfatin-1 is also detected in the adipose tissues of humans and rodents, indicating that nesfatin-1 expression in the fat may regulate food intake independently, rather than relying on leptin. In addition, nesfatin-1 is expressed in the heart as a cardiac peptide. It suggests that nesfatin-1 may regulate cardiac function and encourage clinical potential in the presence of nutrition-dependent physio-pathologic cardiovascular diseases. Currently, only a few studies demonstrate that nesfatin-1 is expressed in the reproductive system. However, it is not clear yet what function of nesfatin-1 is in the reproductive organs. Here, we summarize the expression of nesfatin-1 and its roles in brain and peripheral organs and discuss the possible roles of nesfatin-1 expressed in reproductive organs, including testis, epididymis, ovary, and uterus. We come to the conclusion that nesfatin-1 as a local regulator in male and female reproductive organs may regulate the steroidogenesis in the testis and ovary and the physiological activity in epididymis and uterus.

Glycemic state regulates melanocortin, but not nesfatin-1, responsiveness of glucose-sensing neurons in the nucleus of the solitary tract

The nucleus of the solitary tract (NTS) is a medullary integrative center with critical roles in the coordinated control of energy homeostasis. Here, we used whole cell current-clamp recordings on rat NTS neurons in slice preparation to identify the presence of physiologically relevant glucose-sensing neurons. The majority of NTS neurons (n = 81) were found to be glucose-responsive, with 35% exhibiting a glucose-excited (GE) phenotype (mean absolute change in membrane potential: 9.5 ± 1.1 mV), and 21% exhibiting a glucose-inhibited (GI) response (mean: 6.3 ± 0.7 mV). Furthermore, we found glucose-responsive cells are preferentially influenced by the anorexigenic peptide α-melanocyte-stimulating hormone (α-MSH), but not nesfatin-1. Accordingly, alterations in glycemic state have profound effects on the responsiveness of NTS neurons to α-MSH, but not to nesfatin-1. Indeed, NTS neurons showed increasing responsiveness to α-MSH as extracellular glucose concentrations were decreased, and in hypoglycemic conditions, all NTS neurons were depolarized by α-MSH (mean 10.6 ± 3.2 mV; n = 8). Finally, decreasing levels of extracellular glucose correlated with a significant hyperpolarization of the baseline membrane potential of NTS neurons, highlighting the modulatory effect of glucose on the baseline excitability of cells in this region. Our findings reveal individual NTS cells are capable of integrating multiple sources of metabolically relevant inputs, highlight the rapid capacity for plasticity in medullary melanocortin circuits, and emphasize the critical importance of physiological recording conditions for electrophysiological studies pertaining to the central control of energy homeostasis.

Nesfatin-1 increases energy expenditure and reduces food intake in rats

OBJECTIVE

Energy homeostasis results from a balance of food intake and energy expenditure, accomplished by the interaction of peripheral and central nervous signals. The recently discovered adipokine nesfatin-1 is involved in the central control of food intake, but whether it also participates in the regulation of thermogenesis is unknown.

METHODS

Nesfatin-1 was administered intracerebroventricularly to freely moving, male Wistar rats and direct calorimetry was performed to assess its effects on thermogenesis. Furthermore, food intake was measured and hypothalamic and N. tractus solitarius (NTS) neuropeptide expression was determined by quantitative real-time polymerace chain reaction. Leptin, which is involved in both the regulation of food intake and thermogenesis, was used as positive control.

RESULTS

For the first time it was shown that central nervous administration of nesfatin-1 profoundly increases thermogenesis in rats to a similar extent as leptin and the role of both peptides in the control of food intake was confirmed. Nesfatin-1 significantly downregulated neuropeptide Y (NPY) mRNA expression in both hypothalamus and NTS.

CONCLUSIONS

The results strongly support the prominent role of nesfatin-1 for both energy expenditure and food intake and NPY neurons appear to be involved in this effect.

Cellular actions of nesfatin-1 in the subfornical organ

Nesfatin-1, a centrally acting anorexigenic peptide, is produced in several brain areas involved in metabolic processes and has been implicated in the control of ingestive behaviours and cardiovascular functions. The present study aimed to determine whether the subfornical organ (SFO), a central nervous system (CNS) site that has been extensively implicated in the regulation of appetite and thirst, may represent a potential site for central actions of nesfatin-1. We first used the reverse transcriptase-polymerase chain reaction and were able to confirm the presence of mRNA for the nucleobindin-2 gene in the SFO. We then used whole-cell patch clamp recordings to investigate the influence of nesfatin-1 on the membrane potential of dissociated SFO neurones. A total of 80.3% (49 of 61) of neurones tested showed a response to nesfatin-1 (100 nm, 10 nm and 1 nm). Of these, 47.5% depolarised, with a mean depolarisation of 8.2 ± 0.9 mV (n = 29) and 32.8% hyperpolarised with a mean hyperpolarisation of -8.9 ± 1.2 mV (n = 20). Peak magnitudes were seen at a concentration of 1 nm nesfatin-1, whereas no effect was observed at 100 pm nesftain-1 (n = 3). Furthermore, voltage clamp ramp and step protocols revealed a nesfatin-1 induced activation of the delayed rectifier potassium conductance, IK . Pharmacological blockade of this conductance greatly reduced the magnitude and occurrence of the observed hyperpolarisations. The present study thus demonstrates that nesfatin-1 has the ability to influence the membrane potential of SFO neurones, and thus identifies the SFO as a potential site at which nesfatin-1 may act to regulate ingestive behaviour and cardiovascular control.

Neural circuitry underlying the central hypertensive action of nesfatin-1: melanocortins, corticotropin-releasing hormone, and oxytocin

Nesfatin-1 is produced in the periphery and in the brain where it has been demonstrated to regulate appetite, stress hormone secretion, and cardiovascular function. The anorexigenic action of central nesfatin-1 requires recruitment of neurons producing the melanocortins and centrally projecting oxytocin (OT) and corticotropin-releasing hormone (CRH) neurons. We previously have shown that two components of this pathway, the central melanocortin and oxytocin systems, contribute to the hypertensive action of nesfatin-1 as well. We hypothesized that the cardiovascular effect of nesfatin-1 also was dependent on activation of neurons expressing CRH receptors, and that the order of activation of the melanocortin-CRH-oxytocin circuit was preserved for both the anorexigenic and hypertensive actions of the peptide. Pretreatment of male rats with the CRH-2 receptor antagonist astressin2B abrogated nesfatin-1-induced increases in mean arterial pressure (MAP). Furthermore, the hypertensive action of CRH was blocked by pretreatment with an oxytocin receptor antagonist ornithine vasotocin (OVT), indicating that the hypertensive effect of nesfatin-1 may require activation of oxytocinergic (OTergic) neurons in addition to recruitment of CRH neurons. Interestingly, we found that the hypertensive effect of α-melanocyte stimulating hormone (α-MSH) itself was not blocked by either astressin2B or OVT. These data suggest that while α-MSH-producing neurons are part of a core melanocortin-CRH-oxytocin circuit regulating food intake, and a subpopulation of melanocortin neurons activated by nesfatin-1 do mediate the hypertensive action of the peptide, α-MSH can signal independently from this circuit to increase MAP.

Nesfatin-1: role as possible new anti-obesity treatment

In this article, we review on the current concepts about Nesfatin-1 as a new anti-obesity treatment and evaluate the existing issues in the context of this knowledge and the available literature. The intent is to enable clinicians to know Nesfatin-1 as a new anti-obesity treatment and make rational decisions based on this perspective as possible clinical application. Future research should seek to clarify whether Nesfatin-1 would be beneficial in the management of obesity.

α-MSH exerts direct postsynaptic excitatory effects on NTS neurons and enhances GABAergic signaling in the NTS

The central melanocortin system plays an essential role in the regulation of energy balance. While anorexigenic effects of α-melanocyte-stimulating hormone (α-MSH) acting in the nucleus of the solitary tract (NTS), a critical medullary autonomic control center, have been established, the cellular events underlying these effects are less well characterized. In this study, we used whole-cell patch-clamp electrophysiology to examine firstly whether α-MSH exerts direct postsynaptic effects on the membrane potential of rat NTS neurons in slice preparation, and secondly whether α-MSH influences GABAergic signaling in the NTS. In normal artificial cerebrospinal fluid, perfusion of α-MSH (500 nM) resulted in a depolarization in 39% of cells (n=16, mean 6.14±0.54 mV), and a hyperpolarization in 22% of cells (n=9, -6.79±1.02 mV). Studies using tetrodotoxin to block neuronal communication revealed α-MSH exerts direct depolarizing effects on some NTS neurons, and indirect inhibitory effects on others. A third subset of neurons is simultaneously directly depolarized and indirectly hyperpolarized by α-MSH, resulting in a net lack of effect on membrane potential. The inhibitory inputs influenced by α-MSH were identified as GABAergic, as α-MSH increased the frequency, but not amplitude, of inhibitory postsynaptic currents (IPSCs) in 50% of NTS neurons. α-MSH had no effect on the frequency or amplitude of miniature IPSCs. Furthermore, pharmacological blockade of GABAA and GABAB receptors, and physical removal of all synaptic inputs via cellular dissociation, abolished hyperpolarizations induced by α-MSH. We conclude α-MSH exerts direct, postsynaptic excitatory effects on a subset of NTS neurons. By exciting GABAergic NTS neurons and presynaptically enhancing GABAergic signaling, α-MSH also indirectly inhibits other NTS cells. These findings provide critical insight into the cellular events underlying medullary melanocortin anorexigenic effects, and expand the understanding of the circuitries involved in central melanocortin signaling.

Nesfatin-1 in human and murine cardiomyocytes: synthesis, secretion, and mobilization of GLUT-4

Nesfatin-1, a satiety-inducing peptide identified in hypothalamic regions that regulate energy balance, is an integral regulator of energy homeostasis and a putative glucose-dependent insulin coadjuvant. We investigated its production by human cardiomyocytes and its effects on glucose uptake, in the main cardiac glucose transporter GLUT-4 and in intracellular signaling. Quantitative RT-PCR, Western blots, confocal immunofluorescence microscopy, and ELISA of human and murine cardiomyocytes and/or cardiac tissue showed that cardiomyocytes can synthesize and secrete nesfatin-1. Confocal microscopy of cultured cardiomyocytes after GLUT-4 labeling showed that nesfatin-1 mobilizes this glucose transporter to cell peripherals. The rate of 2-deoxy-D-[(3)H]glucose incorporation demonstrated that nesfatin-1 induces glucose uptake by HL-1 cells and cultured cardiomyocytes. Nesfatin-1 induced dose- and time-dependent increases in the phosphorylation of ERK1/2, AKT, and AS160. In murine and human cardiac tissue, nesfatin-1 levels varied with diet and coronary health. In conclusion, human and murine cardiomyocytes can synthesize and secrete nesfatin-1, which is able to induce glucose uptake and the mobilization of the glucose transporter GLUT-4 in these cells. Nesfatin-1 cardiac levels are regulated by diet and coronary health.

Gastric distension activates NUCB2/nesfatin-1-expressing neurons in the nucleus of the solitary tract

Brainstem structures such as the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus nerve (DMNX) are essential for the digestive function of the stomach. A large number of neurotransmitters including glutamate and gamma-aminobutyric acid (GABA) are involved in the central control of gastric functions. However, the neuropeptidergic systems implicated in this process remain undetermined. Nesfatin-1 was recently identified as a neuropeptide cleaved from the N-terminal part of NEFA/nucleobindin 2 precursor (NUCB2). Central administration of this neuropeptide inhibits food consumption and gastroduodenal motility in rodents. Interestingly, the NTS and the DMNX contain a dense population of NUCB2/nesfatin-1 cell bodies. These observations led us to investigate the possible involvement of NUCB2/nesfatin-1 neurons in the brainstem neuronal pathways that modulate gastric functions. We observed an activation of NTS NUCB2/nesfatinergic neurons after gastric distention in rats. In addition, we found that several NTS NUCB2/nesfatinergic neurons were GABAergic. Finally, when fluorogold was injected at the stomach level, many retrogradely labeled neurons were observed in the DMNX which were also positive for NUCB2/nesfatin-1. Taken together, these observations suggest for the first time that NUCB2/nesfatin-1 neurons of the NTS are sensitive to gastric distension and then may contribute to the satiety signal.

Multi-functional peptide hormone NUCB2/nesfatin-1

The recently discovered nesfatin-1 is regulated by hunger and satiety. The precursor protein NUCB2 is proteolytically cleaved into three resulting fragments: nesfatin-1, nesfatin-2, and nesfatin-3. The middle segment of nesfatin-1 (M30) is responsible for limiting food intake, while the exact physiological role of nesfatin-2 and nesfatin-3 are not currently known yet. This hormone plays role/roles on diabetic hyperphagia, epilepsy, mood, stress, sleeping, anxiety, hyperpolarization, depolarization, and reproductive functions. This review will address nesfatin, focusing on its discovery and designation, biochemical structure, scientific evidence of its anorexigenic character, the results of the human and animal studies until the present day, its main biochemical and physiological effects, and its possible clinical applications.

Decreased plasma nesfatin-1 levels in patients with acute myocardial infarction

Nesfatin-1 is a novel anorexigenic hormone which has close relationship with diabetes, obese, anorexia nervosa, psychiatric disorders and neurogenic diseases. The aim of our study was to evaluate levels of plasma nesfatin-1 among patients presenting with coronary artery disease and the correlation between nesfatin-1 levels and other clinical parameters. Fasting plasma levels of nesfatin-1 were tested in 48 acute myocardial infarction (AMI) patients, 74 stable angina pectoris (SAP) patients and 34 control subjects. All of them were examined by coronary angiography. The severity of coronary atherosclerosis was assessed using the Gensini score. Plasma nesfatin-1 levels were significantly lower in AMI group than SAP group or control group (0.91±0.08 ng/mL vs. 0.98±0.19 ng/mL and 1.09±0.39 ng/mL, respectively, P<0.05). In AMI patients, plasma nesfatin-1 levels were negatively correlated with high-sensitivity C-reactive protein, neutrophil% or Gensini scores. Such information implies that lower nesfatin-1 concentration may play a very important role in the development of AMI.

Nesfatin-1 activates cardiac vagal neurons of nucleus ambiguus and elicits bradycardia in conscious rats

Nesfatin-1, a peptide whose receptor is yet to be identified, has been involved in the modulation of feeding, stress, and metabolic responses. More recently, increasing evidence supports a modulatory role for nesfatin-1 in autonomic and cardiovascular activity. This study was undertaken to test if the expression of nesfatin-1 in the nucleus ambiguus, a key site for parasympathetic cardiac control, may be correlated with a functional role. As we have previously demonstrated that nesfatin-1 elicits Ca²⁺ signaling in hypothalamic neurons, we first assessed the effect of this peptide on cytosolic Ca²⁺ in cardiac pre-ganglionic neurons of nucleus ambiguus. We provide evidence that nesfatin-1 increases cytosolic Ca²⁺ concentration via a Gi/o-coupled mechanism. The nesfatin-1-induced Ca²⁺ rise is critically dependent on Ca²⁺ influx via P/Q-type voltage-activated Ca²⁺ channels. Repeated administration of nesfatin-1 leads to tachyphylaxis. Furthermore, nesfatin-1 produces a dose-dependent depolarization of cardiac vagal neurons via a Gi/o-coupled mechanism. In vivo studies, using telemetric and tail-cuff monitoring of heart rate and blood pressure, indicate that microinjection of nesfatin-1 into the nucleus ambiguus produces bradycardia not accompanied by a change in blood pressure in conscious rats. Taken together, our results identify for the first time that nesfatin-1 decreases heart rate by activating cardiac vagal neurons of nucleus ambiguus. Our results indicate that nesfatin-1, one of the most potent feeding peptides, increases cytosolic Ca²⁺ by promoting Ca²⁺ influx via P/Q channels and depolarizes nucleus ambiguus neurons; both effects are Gi/o-mediated. In vivo studies indicate that microinjection of nesfatin-1 into nucleus ambiguus produces bradycardia in conscious rats. This is the first report that nesfatin-1 increases the parasympathetic cardiac tone.

Neuron discharge and c-Fos expression in the nucleus of the solitary tract following electroacupuncture at acupoints of the Yangming Stomach Meridian of Foot

The nucleus of the solitary tract (nucleus tractus solitarii; NTS) is a primary center for both visceral afferents and somatic afferents. Previous experiments have demonstrated that the NTS is closely connected to the stomach and acupoints in the Yangming Stomach Meridian of Foot (ST Meridian). In this study, extracellular recording and immunochemistry methods were used to analyze the discharge of neurons and c-Fos protein expression in the NTS following acupuncture at different acupoints and a nonacupoint. A total of 104 discharging neurons were detected in the NTS of 52 rats, of which 86 provided complete data. After acupuncture at Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint, the neuron response rate in the NTS was 65.12%, 51.16%, 46.51%, 34.88% and 31.40% respectively. For neuron response rate, there was a significant difference among Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint (p < 0.01 or p < 0.05). In the other 48 rats, the number of c-Fos immunoreactive neurons in the NTS by electroacupuncture (EA) at Sibai (ST 2) group was significantly higher than that EA at other acupoints and the nonacupoint (p < 0.05 or p < 0.01). EA at both Zusanli (ST 36) and Neiting (ST 44) increased c-Fos immunoreactive neurons significantly over EA at Quanliao (SI 18) and the nonacupoint (p < 0.05 or p < 0.01), while there was no difference between EA at Quanliao (SI 18) and the nonacupoint group (p > 0.05). The experiments demonstrated that the afferent convergence in NTS are different by body surface points stimulus, which suggests that the NTS might be a primary center in the central nervous system receiving acupoints stimulus from the ST Meridian.