Nesfatin-1, corticotropin-releasing hormone, thyrotropin-releasing hormone, and neuronal histamine interact in the hypothalamus to regulate feeding behavior

Examining the Potential Applicability of Orexigenic and Anorexigenic Peptides in Veterinary Medicine for the Management of Obesity in Companion Animals

This review article comprehensively explores the role of orexigenic and anorexigenic peptides in the management of obesity in companion animals, with a focus on clinical applications. Obesity in domestic animals, particularly dogs and cats, is prevalent, with significant implications for their health and well-being. Factors contributing to obesity include overfeeding, poor-quality diet, lack of physical activity, and genetic predispositions. Despite the seriousness of this condition, it is often underestimated, with societal perceptions sometimes reinforcing unhealthy behaviors. Understanding the regulation of food intake and identifying factors affecting the function of food intake-related proteins are crucial in combating obesity. Dysregulations in these proteins, whether due to genetic mutations, enzymatic dysfunctions, or receptor abnormalities, can have profound health consequences. Molecular biology techniques play a pivotal role in elucidating these mechanisms, offering insights into potential therapeutic interventions. The review categorizes food intake-related proteins into anorexigenic peptides (inhibitors of food intake) and orexigenic peptides (enhancers of food intake). It thoroughly examines current research on regulating energy balance in companion animals, emphasizing the clinical application of various peptides, including ghrelin, phoenixin (PNX), asprosin, glucagon-like peptide 1 (GLP-1), leptin, and nesfatin-1, in veterinary obesity management. This comprehensive review aims to provide valuable insights into the complex interplay between peptides, energy balance regulation, and obesity in companion animals. It underscores the importance of targeted interventions and highlights the potential of peptide-based therapies in improving the health outcomes of obese pets.

Thyrotropin-Releasing Hormone and Food Intake in Mammals: An Update

Thyrotropin-releasing hormone (TRH; pGlu-His-Pro-NH2) is an intercellular signal produced mainly by neurons. Among the multiple pharmacological effects of TRH, that on food intake is not well understood. We review studies demonstrating that peripheral injection of TRH generally produces a transient anorexic effect, discuss the pathways that might initiate this effect, and explain its short half-life. In addition, central administration of TRH can produce anorexic or orexigenic effects, depending on the site of injection, that are likely due to interaction with TRH receptor 1. Anorexic effects are most notable when TRH is injected into the hypothalamus and the nucleus accumbens, while the orexigenic effect has only been detected by injection into the brain stem. Functional evidence points to TRH neurons that are prime candidate vectors for TRH action on food intake. These include the caudal raphe nuclei projecting to the dorsal motor nucleus of the vagus, and possibly TRH neurons from the tuberal lateral hypothalamus projecting to the tuberomammillary nuclei. For other TRH neurons, the anatomical or physiological context and impact of TRH in each synaptic domain are still poorly understood. The manipulation of TRH expression in well-defined neuron types will facilitate the discovery of its role in food intake control in each anatomical scene.

Suppressive action of nesfatin-1 and nesfatin-1-like peptide on cortisol synthesis in human adrenal cortex cells

Nucleobindin-derived peptides, nesfatin-1 [NESF-1] and nesfatin-1-like-peptide [NLP] have diverse roles in endocrine and metabolic regulation. While both peptides showed a stimulatory effect on the synthesis of proopiomelanocortin (POMC), the adrenocorticotropic hormone (ACTH) precursor in mouse corticotrophs, whether NESF-1 and NLP have any direct effect on glucocorticoid [GC] synthesis in the adrenal cortex remains unknown. The main aim of this study was to determine if NESF-1 and/or NLP act directly on adrenal cortex cells to regulate cortisol synthesis in vitro. Whether NLP injection affects stress-hormone gene expression in the adrenal gland and pituitary in vivo in mice was also assessed. In addition, cortisol synthetic pathway in Nucb1 knockout mice was studied. Human adrenal cortical [H295R] cells showed immunoreactivity for both NUCB1/NLP and NUCB2/NESF-1. NLP and NESF-1 decreased the abundance of steroidogenic enzyme mRNAs, and cortisol synthesis and release through the AC/PKA/CREB pathway in H295R cells. Similarly, intraperitoneal injection of NLP in mice decreased the expression of enzymes involved in glucocorticoid (GC) synthesis in the adrenal gland while increasing the expression of Pomc, Pcsk1 and Crhr1 in the pituitary. Moreover, the melanocortin 2 receptor (Mc2r) mRNA level was enhanced in the adrenal gland samples of NLP injected mice. However, the global genetic disruption in Nucb1 did not affect most steroidogenic enzyme mRNAs, and Pomc, Pcsk2 and Crhr1 mRNAs in mice adrenal gland and pituitary gland, respectively. Collectively, these data provide the first evidence for a direct inhibition of cortisol synthesis and secretion by NLP and NESF-1. NUCB peptides might still elicit a net stimulatory effect on GC synthesis and secretion through their positive effects on ACTH-MC2R pathway in the pituitary.

The Diverse Network of Brain Histamine in Feeding: Dissect its Functions in a Circuit-Specific Way

Feeding is an intrinsic and important behavior regulated by complex molecular, cellular and circuit-level mechanisms, one of which is the brain histaminergic network. In the past decades, many studies have provided a foundation of knowledge about the relationship between feeding and histamine receptors, which are deemed to have therapeutic potential but are not successful in treating feeding- related diseases. Indeed, the histaminergic circuits underlying feeding are poorly understood and characterized. This review describes current knowledge of histamine in feeding at the receptor level. Further, we provide insight into putative histamine-involved feeding circuits based on the classic feeding circuits. Understanding the histaminergic network in a circuit-specific way may be therapeutically relevant for increasing the drug specificity and precise treatment in feeding-related diseases.

Histaminergic regulation of food intake

Histamine is a biogenic amine that acts as a neuromodulator within the brain. In the hypothalamus, histaminergic signaling contributes to the regulation of numerous physiological and homeostatic processes, including the regulation of energy balance. Histaminergic neurons project extensively throughout the hypothalamus and two histamine receptors (H1R, H3R) are strongly expressed in key hypothalamic nuclei known to regulate energy homeostasis, including the paraventricular (PVH), ventromedial (VMH), dorsomedial (DMH), and arcuate (ARC) nuclei. The activation of different histamine receptors is associated with differential effects on neuronal activity, mediated by their different G protein-coupling. Consequently, activation of H1R has opposing effects on food intake to that of H3R: H1R activation suppresses food intake, while H3R activation mediates an orexigenic response. The central histaminergic system has been implicated in atypical antipsychotic-induced weight gain and has been proposed as a potential therapeutic target for the treatment of obesity. It has also been demonstrated to interact with other major regulators of energy homeostasis, including the central melanocortin system and the adipose-derived hormone leptin. However, the exact mechanisms by which the histaminergic system contributes to the modification of these satiety signals remain underexplored. The present review focuses on recent advances in our understanding of the central histaminergic system's role in regulating feeding and highlights unanswered questions remaining in our knowledge of the functionality of this system.

Role of brain NUCB2/nesfatin-1 in stress and stress-related gastrointestinal disorders

Since the discovery of NUCB2/nesfatin-1 as a novel anorexigenic factor, the expanding function of this peptide has been elucidated in recent years. Increasing evidence suggests that NUCB2/nesfatin-1 is also involved in the regulation of stress and stress-related gastrointestinal disorders. Therefore, we investigated the relationship between NUCB2/nesfatin-1, stress and stress-related gastrointestinal disorders and summarized the results of these studies. Different stressors and duration of stress activate different NUCB2/nesfatin-1-associated brain regions and have different effects on serum corticosterone levels. Central and peripheral NUCB2/nesfatin-1 mediates stress-related gastrointestinal disorders but appears to be protective against inflammatory bowel disease. NUCB2/nesfatin-1 plays an important role in mediating the brain-gut crosstalk, but precise clarification is still needed to gain more insight into these complex relationships.

Association analysis of gut microbiota-metabolites-neuroendocrine changes in male rats acute exposure to simulated altitude of 5500 m

Hyperactivation of hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic-pituitary-thyroid (HPT) axis were found in acute high altitude challenge, but the role of gut microbiota and metabolites is unknown. We utilized adult male Sprague-Dawley rats at a simulated altitude of 5500 m for 3 days in a hypobaric-hypoxic chamber. ELISA and metabolomic analyses of serum and 16S rRNA and metabolomic analyses of fecal samples were then performed. Compared with the normoxic group, serum corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), corticosterone (CORT), and thyroxine (tT₄) were increased in the hypoxia group, whereas thyrotropin-releasing hormone (TRH) was decreased. Bacteroides, Lactobacillus, Parabacteroides, Butyricimonas, SMB53, Akkermansia, Phascolarctobacterium, and Aerococcus were enriched in hypoxia group, whereas [Prevotella], Prevotella, Kaistobacter, Salinibacterium, and Vogesella were enriched in normoxic group. Metabolomic analysis indicated that acute hypoxia significantly affected fecal and serum lipid metabolism. In addition, we found five fecal metabolites may mediate the cross-talk between TRH, tT₄, and CORT with [Prevotella], Kaistobacter, Parabacteroides, and Aerococcus, and 6 serum metabolites may mediate the effect of TRH and tT₄ on [Prevotella] and Kaistobacter by causal mediation analysis. In conclusion, this study provides new evidence that key metabolites mediate the cross-talk between gut microbiota with HPA and HPT axis under acute hypobaric hypoxia challenge.

Immunolocalization of Nesfatin-1 in the Gastrointestinal Tract of the Common Bottlenose Dolphin Tursiops truncatus

Simple Summary

Nesfatin-1 (Nesf-1) is a neuropeptide that plays important roles in regulating food intake, mainly related to its anorexigenic effect, and it is mainly distributed in the digestive systems of all vertebrates. With this study, we expand knowledge on the localization of Nesf-1 in the digestive tract of an aquatic mammalian species, the common bottlenose dolphin (Tursiops truncatus), allowing comparative study on terrestrial mammals. Dolphin tissue samples (three gastric chambers and intestine) were provided by the Mediterranean Marine Mammal Tissue Bank of the Department of Comparative Biomedicine and Food Science of the University of Padova (Italy).

Abstract

First identified as an anorexigenic peptide, in the last decades, several studies have suggested that Nesfatin-1 (Nesf-1) is a pleiotropic hormone implicated in numerous regulatory processes in peripheral organs and tissues. In vertebrates, Nesf-1 is indeed expressed in the central nervous system and peripheral organs. In this study, we characterized the pattern of Nesf-1 distribution within the digestive tract of the common bottlenose dolphin (Tursiops truncatus), composed of three gastric chambers and an intestine without a clear subdivision in the small and large intestine, also lacking a caecum. Our results indicated that Nesf-1 is widely distributed in cells of the mucosal epithelium of the gastric chambers. Most of the immunoreactivity was observed in the second chamber, compared to the first and third chambers. Immunopositivity was also found in nerve fibers and neurons, scattered or/and clustered in ganglion structures along all the examined gastrointestinal tracts. These observations add new data on the highly conserved role of Nesf-1 in the mammalian digestive system.

Possible interaction of central noradrenergic, serotoninergic and oxytocin systems with nesfatin-1 induced hypophagia and feeding behavior in newborn broiler

There are some differences between mammals and birds in terms of central food intake regulation. In avian species, the hypophagic role of nesfatin-1 has not been investigated with other neurotransmitters. Therefore, this study aimed to determine the alteration of feeding behavior following intracerebroventricular (ICV) injection of nesfatin-1 and its possible interaction with central noradrenergic, serotoninergic, and oxytocin systems in newborn broiler chicks. In experiment 1, birds received ICV injection of phosphate-buffered saline (PBS), prazosin (α₁ receptors antagonist, 10 nmol), nesfatin-1 (40 ng), and co-administration of prazosin and nesfatin-1. Experiments 2-10 were similar to experiment 1, except that yohimbine (α₂ receptors antagonist, 13 nmol), metoprolol (β₁ receptors antagonist, 24 nmol), IC1118,551 (β₂ receptors antagonist for, 5nmol), SR59230R (β₃ receptors antagonist, 20 nmol), fluoxetine (serotonin reuptake inhibitor, 10 µg), PCPA (serotonin synthesis inhibitor, 1.5 µg), 8-OH-DPAT (5-HT₁A receptors agonist, 15.25 nmol), SB242084 (5-HT₂C receptors antagonist,1.5 µg) and tocinoic acid (oxytocin receptors antagonist, 2 µg) were injected instead of prazosin. Immediately after the injection, food consumption and behavioral traits were recorded. Nesfatin-1 decreased food consumption (P < 0.05). Nesfatin-1 along with ICI118551 decreased food consumption (P < 0.05). The nesfatin-1- induced hypophagia were reduced by the simultaneous injection of PCPA and nesfatin-1 (P < 0.05). Nesfatin-1induced hypophagia were decreased by the simultaneous injection of SB242084 (P < 0.05). The nesfatin-1 -induced hypophagia were abolished by the simultaneous injection of the tocinoic acid and nesfatin-1 (P < 0.05). ICV injection of the nesfatin-1 decreased the number of steps, jumps, exploratory food, and pecks (P < 0.05) with no effect on drink pecks (P > 0.05). Nesfatin-1 significantly decreased standing time and increased both sitting time and rest time (P < 0.05). Nesfatin-1 could play an important role in feeding behavior, and its hypophagic effects were mediated by β₂ adrenergic, 5-HT₂C serotoninergic, and oxytocin receptors in neonatal chickens.

"Sibling" battle or harmony: crosstalk between nesfatin-1 and ghrelin

Ghrelin was first identified as an endogenous ligand of the growth hormone secretagogue receptor (GHSR) in 1999, with the function of stimulating the release of growth hormone (GH), while nesfatin-1 was identified in 2006. Both peptides are secreted by the same kind of endocrine cells, X/A-like cells in the stomach. Compared with ghrelin, nesfatin-1 exerts opposite effects on energy metabolism, glucose metabolism, gastrointestinal functions and regulation of blood pressure, but exerts similar effects on anti-inflammation and neuroprotection. Up to now, nesfatin-1 remains as an orphan ligand because its receptor has not been identified. Several studies have shown the effects of nesfatin-1 are dependent on the receptor of ghrelin. We herein compare the effects of nesfatin-1 and ghrelin in several aspects and explore the possibility of their interactions.

The involvement of the central cholinergic system in the hyperventilation effect of centrally injected nesfatin-1 in rats

We recently demonstrated that peripheral and central administration of nesfatin-1 in fasting and satiety states generate hyperventilation activity by increasing tidal volume (TV), respiratory rate (RR), and respiratory minute ventilation (RVM). The present study aimed to investigate the mediation of central cholinergic receptors effective in respiratory control in the hyperventilation activity of nesfatin-1. Besides this, we intended to determine possible changes in blood gases due to hyperventilation activity caused by nesfatin-1 and investigate the mediation of central cholinergic receptors in these changes. Intracerebroventricular (ICV) administration of nesfatin-1 revealed a hyperventilation response with an increase in TV, RR, RMV, and pO₂ and a decrease in pCO₂ in saturated Sprague Dawley rats. ICV pretreatment with the muscarinic receptor antagonist atropine partially blocked the RR, RMV, pO₂, and pCO₂ responses produced by nesfatin-1 while completely blocking the TV response. However, central pretreatment with nicotinic receptor antagonist mecamylamine blocked the respiratory and blood gas responses induced by nesfatin-1. The study's conclusion demonstrated that nesfatin-1 had active hyperventilation effects resulting in an increase in pO₂ and a decrease in pCO₂. The critical finding of the study was that activation of central cholinergic receptors was involved in nesfatin-1-evoked hyperventilation and blood gas responses.

Targeting Histamine and Histamine Receptors for the Precise Regulation of Feeding

Histamine has long been accepted as an anorexigenic agent. However, lines of evidence have suggested that the roles of histamine in feeding behaviors are much more complex than previously thought, being involved in satiety, satiation, feeding motivation, feeding circadian rhythm, and taste perception and memory. The functional diversity of histamine makes it a viable target for clinical management of obesity and other feeding-related disorders. Here, we update the current knowledge about the functions of histamine in feeding and summarize the underlying molecular and neural circuit mechanisms. Finally, we review the main clinical studies about the impacts of histamine-related compounds on weight control and discuss insights into future research on the roles of histamine in feeding. Despite the recent progress in histamine research, the histaminergic feeding circuits are poorly understood, and it is also worth verifying the functions of histamine receptors in a more spatiotemporally specific manner.

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.

Endogenous NUCB2/Nesfatin-1 Regulates Energy Homeostasis Under Physiological Conditions in Male Rats

Nesfatin-1 is the proteolytic cleavage product of Nucleobindin 2, which is expressed both in a number of brain nuclei (e. g., the paraventricular nucleus of the hypothalamus) and peripheral tissues. While Nucleobindin 2 acts as a calcium binding protein, nesfatin-1 was shown to affect energy homeostasis upon central nervous administration by decreasing food intake and increasing thermogenesis. In turn, Nucleobindin 2 mRNA expression is downregulated in starvation and upregulated in the satiated state. Still, knowledge about the physiological role of endogenous Nucleobindin 2/nesfatin-1 in the control of energy homeostasis is limited and since its receptor has not yet been identified, rendering pharmacological blockade impossible. To overcome this obstacle, we tested and successfully established an antibody-based experimental model to antagonize the action of nesfatin-1. This model was then employed to investigate the physiological role of endogenous Nucleobindin 2/nesfatin-1. To this end, we applied nesfatin-1 antibody into the paraventricular nucleus of satiated rats to antagonize the presumably high endogenous Nucleobindin 2/nesfatin-1 levels in this feeding condition. In these animals, nesfatin-1 antibody administration led to a significant decrease in thermogenesis, demonstrating the important role of endogenous Nucleobindin 2/nesfatin-1in the regulation of energy expenditure. Additionally, food and water intake were significantly increased, confirming and complementing previous findings. Moreover, neuropeptide Y was identified as a major downstream target of endogenous Nucleobindin 2/nesfatin-1.

[Neural pathway between the nucleus accumbens and the rostral ventrolateral medulla in a rat model of anorexia nervosa]

OBJECTIVE

To investigate the potential neural pathway connecting the nucleus accumbens (NAc) and the rostral ventrolateral medulla (RVLM), and whether the pathway participates in the regulation of cardiovascular function in a model rat of anorexia nervosa (AN).

METHODS

Rat models of AN were established by allowing voluntary activity in a running wheel with restricted feeding, with the rats having free access to normal chow without exercise as the control group. FluoroGold (FG) retrograde tracing method and multi-channel simultaneous recording technique were used to explore the possible pathway between the NAc and the RVLM.

RESULTS

The rats in AN group exhibited significantly reduced systolic blood pressure (SBP), mean arterial pressure (MAP) and heart rate (HR) with significantly increased discharge frequency of RVLM neurons in comparison with the control rats. After the injection of FG into the RVLM, retrograde labeled neurons were observed in the NAc of the rats in both the normal control and AN groups. In both groups, SBP and HR were significantly decreased in response to 400 μA electrical stimulation of the NAc accompanied by an obvious increase in the discharge frequency of the RVLM neurons; the diastolic blood pressure (DBP) and MAP were significantly lower in AN model rats than in the normal rats in response to the stimulation.

CONCLUSIONS

We successfully established a rat model of AN via hyperactivity and restricted feeding and confirm the presence of a neural pathway connecting the NAc and the RVLM. This pathway might participate in the regulation of cardiovascular function in AN model rats.

NUCB2 polymorphisms are associated with an increased risk for type 2 diabetes in the Chinese population

Background

The nucleobindin 2 (NUCB2) gene encodes the NUCB2 protein, which plays a critical role in glucose metabolism and diabetes. This study explored the correlation between NUCB2 genetic variants and type 2 diabetes mellitus (T2DM). The study further examined the different NUCB2 variants that confer risk to T2DM in Chinese Han populations.

Methods

This study evaluated the anthropometric and glycemic profiles of 578 T2DM patients and 1,609 healthy controls. Subsequently, we genotyped five single nucleotide polymorphisms (SNPs) (rs10832756, rs1330, rs10766383, rs10832757, and rs11024251) in all the study participants using a Sequenom Mass ARRAY SNP genotyping platform.

Results

The distribution of polymorphisms was significantly different between the T2DM patients and healthy controls. Our logistic regression analysis results showed that the five NUCB2 SNPs are significantly correlated with the risk for T2DM, especially rs11024251(P=2.97×10⁻⁶). Interestingly, analysis of male and female sub-populations separately showed that only two of the SNPs (rs10832757 and rs11024251) have significant correlation to T2DM in males [P=0.0244, odds ratio (OR) 1.28 and P=0.0062, OR 1.35, respectively). In females however, we identified four significant SNPs (rs1330, rs10766383, rs10832757, and rs11024251; P<0.05, OR 1.31–1.42). Furthermore, we found that rs1330 is associated with body mass index of female subpopulation only (P=0.0174, β =0.0060).

Conclusions

NUCB2 polymorphisms could have a pivotal role in the presence of T2DM. Sex-specific SNPs of NUCB2 could account for the differences in clinical features of T2DM between male and female subpopulations. Nevertheless, our results should be replicated using larger sample sizes, and experimental investigations are needed to elucidate the molecular mechanisms of the associations observed in this study.

Chronic histamine 3 receptor antagonism alleviates depression like conditions in mice via modulation of brain-derived neurotrophic factor and hypothalamus-pituitary adrenal axis

The last two decades of research has established histamine (HA) as a neurotransmitter. Since H3R antagonists are known to modulate several neurotransmitters besides HA, H3R antagonists have shown potential for the treatment of different central nervous system disorders, including depression. However, molecular mechanisms underlying the beneficial effects of H3R antagonism in depression are not clear, yet. In the present study, we investigated the antidepressant potential of ciproxifan, a selective H3R antagonist, in chronic unpredictable stress (CUS) model of depression in C57BL/6 J mice. We observed that chronic treatment of CUS mice with ciproxifan (3 mg/kg i.p.; for three weeks) alleviates depression-like symptoms such as helplessness measured by forced swim and tail suspension test (FST and TST), anhedonia measured by sucrose preference test (SPT) and social deficit measured in social behavior test. Chronic ciproxifan treatment restored CUS induced BDNF expression in the prefrontal cortex (PFC) and hippocampus. We also observed that ciproxifan modulates CUS induced NUCB2/nesfatin-1 and CRH expression in the hypothalamus and plasma corticosterone. We also determined the direct effect of HA on BDNF expression in neurons by western blotting and immunocytochemistry, and found that HA significantly induced BDNF expression, which was blocked by the H4R selective antagonist, but not by other HA receptor selective antagonists. Furthermore, ciproxifan significantly modulated NMDA glutamate receptor subunits NR2B and NR2A. Thus, these results suggest that increased HA signaling in the brain produces antidepressant-like effects in mice and modulates BDNF expression and HPA-axis.

Protective role of AgRP neuron's PDK1 against salt-induced hypertension

In the hypothalamic arcuate nucleus (ARC), orexigenic agouti-related peptide (AgRP) neurons regulate feeding behavior and energy homeostasis. The 3-phosphoinositide-dependent protein kinase-1 (PDK1) in AgRP neurons serves as a major signaling molecule for leptin and insulin, the hormones regulating feeding behavior, energy homeostasis and circulation. However, it is unclear whether PDK1 in AGRP neurons is also involved in regulation of blood pressure. This study explored it by generating and analyzing AgRP neuron-specific PDK1 knockout (Agrp-Pdk1^flox/flox) mice and effect of high salt diet on blood pressure in KO and WT mice was analyzed. Under high salt diet feeding, systolic blood pressure (SBP) of Agrp-Pdk1^flox/flox mice was significantly elevated compared to Agrp-Cre mice. When the high salt diet was switched to control low salt diet, SBP of Agrp-Pdk1^flox/flox mice returned to the basal level observed in Agrp-Cre mice within 1 week. In Agrp-Pdk1^flox/flox mice, urinary noradrenalin excretion and NUCB2 mRNA expression in hypothalamic paraventricular nucleus (PVN) were markedly upregulated. Moreover, silencing of NUCB2 in the PVN counteracted the rises in urinary noradrenalin excretions and SBP. These results demonstrate a novel role of PDK1 in AgRP neurons to counteract the high salt diet-induced hypertension by preventing hyperactivation of PVN nesfatin-1 neurons.

High levels of Nesfatin-1 in relation to the dysfunction of the hypothalamic-pituitary-adrenal and hypothalamus-pituitary-thyroid axes in depressed patients with subclinical hypothyroidism

Despite the increasing amount of evidence suggesting a relationship between depression and subclinical hypothyroidism (SCH), the exact mechanism underlying this relationship remains unclear. The main purpose of this study was to investigate the roles of plasma Nesfatin-1 levels and dysfunction of the hypothalamic-pituitary-adrenal (HPA) and hypothalamus-pituitary-thyroid (HPT) axes in the comorbidity of depression and SCH. Dysfunctions of the HPA and HPT axes were detected by measuring plasma corticosterone and thyroid-stimulating hormone (TSH) concentrations, respectively. Subjects in the patient group were selected from patients hospitalized at the Anhui Mental Health Center, and subjects in the control group were recruited from healthy volunteers. Healthy control subjects were matched to the patients in terms of weight and body mass index. The Hamilton Depression Rating Scale was administered to both the groups. The enzyme-linked immunosorbent assay method was used to measure plasma Nesfatin-1, corticosterone, and TSH levels. A radioimmunoassay kit was used for the measurement of the plasma-free triiodothyronine and plasma-free thyroxine. The results showed that the Hamilton Depression Rating Scale scores and average Nesfatin-1, corticosterone, and TSH levels were significantly higher in depressed patients with SCH than in the control group. Moreover, positive relationships were observed between Nesfatin-1 levels and the concentrations of corticosterone (r=0.626, P<0.001) and TSH (r=0.229, P=0.036) in depressed patients with SCH. These findings indicate that Nesfatin-1 is involved in the comorbidity of depression and SCH, and the mechanism underlying this involvement might be related to the dysfunction of the HPA and HPT axes.

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.

Hypothalamic L-Histidine Decarboxylase Is Up-Regulated During Chronic REM Sleep Deprivation of Rats

A competition of neurobehavioral drives of sleep and wakefulness occurs during sleep deprivation. When enforced chronically, subjects must remain awake. This study examines histaminergic neurons of the tuberomammillary nucleus of the posterior hypothalamus in response to enforced wakefulness in rats. We tested the hypothesis that the rate-limiting enzyme for histamine biosynthesis, L-histidine decarboxylase (HDC), would be up-regulated during chronic rapid eye movement sleep deprivation (REM-SD) because histamine plays a major role in maintaining wakefulness. Archived brain tissues of male Sprague Dawley rats from a previous study were used. Rats had been subjected to REM-SD by the flowerpot paradigm for 5, 10, or 15 days. For immunocytochemistry, rats were transcardially perfused with acrolein-paraformaldehyde for immunodetection of L-HDC; separate controls used carbodiimide-paraformaldehyde for immunodetection of histamine. Immunolocalization of histamine within the tuberomammillary nucleus was validated using carbodiimide. Because HDC antiserum has cross-reactivity with other decarboxylases at high antibody concentrations, titrations localized L-HDC to only tuberomammillary nucleus at a dilution of ≥ 1:300,000. REM-SD increased immunoreactive HDC by day 5 and it remained elevated in both dorsal and ventral aspects of the tuberomammillary complex. Our results suggest that up-regulation of L-HDC within the tuberomammillary complex during chronic REM-SD may be responsible for maintaining wakefulness.

Nesfatin-1 influences the excitability of gastric distension-responsive neurons in the ventromedial hypothalamic nucleus of rats

The present study investigated the effects of nesfatin-1 on gastric distension (GD)-responsive neurons via an interaction with corticotropin-releasing factor (CRF) receptor signaling in the ventromedial hypothalamic nucleus (VMH), and the potential regulation of these effects by hippocampal projections to VMH. Extracellular single-unit discharges were recorded in VHM following administration of nesfatin-1. The projection of nerve fibers and expression of nesfatin-1 were assessed by retrograde tracing and fluoro-immunohistochemical staining, respectively. Results showed that there were GD-responsive neurons in VMH; Nesfatin-1 administration and electrical stimulation of hippocampal CA1 sub-region altered the firing rate of these neurons. These changes could be partially blocked by pretreatment with the non-selective CRF antagonist astressin-B or an antibody to NUCB2/nesfatin-1. Electrolytic lesion of CA1 hippocampus reduced the effects of nesfatin-1 on VMH GD-responsive neuronal activity. These studies suggest that nesfatin-1 plays an important role in GD-responsive neuronal activity through interactions with CRF signaling pathways in VMH. The hippocampus may participate in the modulation of nesfatin-1-mediated effects in VMH.

Peripheral injection of bombesin induces c-Fos in NUCB2/nesfatin-1 neurons

As anorexigenic hormones bombesin and nucleobindin2 (NUCB2)/nesfatin-1 decrease food intake in rodents. Both hormones have been described in brain nuclei that play a role in the modulation of hunger and satiety, like the paraventricular nucleus of the hypothalamus (PVN) and the nucleus of the solitary tract (NTS). However, the direct interaction of the two hormones is unknown so far. The aim of study was to elucidate whether bombesin directly interacts with NUCB2/nesfatin-1 neurons in the PVN and NTS. Therefore, we injected bombesin intraperitoneally (ip) at two doses (26 and 32nmol/kg body weight) and assessed c-Fos activation in the PVN, arcuate nucleus (ARC) and NTS compared to vehicle treated rats (0.15M NaCl). We also performed co-localization studies with oxytocin or tyrosine hydroxylase. Bombesin at both doses increased the number of c-Fos positive neurons in the PVN (p<0.05) and NTS (p<0.05) compared to vehicle, while in the ARC no modulation was observed (p>0.05). In the PVN and NTS the number of c-Fos positive neurons colocalized with NUCB2/nesfatin-1 increased after bombesin injection compared to vehicle treatment (p<0.05). Moreover, an increase of activated NUCB2/nesfatin-1 immunoreactive neurons that co-expressed oxytocin in the PVN (p<0.05) or tyrosine hydroxylase in the NTS (p<0.05) was observed compared to vehicle. Our results show that peripherally injected bombesin activates NUCB2/nesfatin-1 neurons in the PVN and NTS giving rise to a possible interaction between bombesin and NUCB2/nesfatin-1 in the modulation of food intake.

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.

Effect of neonatal maternal separation on serum level of nesfatin-1 in rats

AIM: To explore the effect of neonatal maternal separation on the concentration of serum nesfatin-1 in rats.

METHODS: Newborn male Sprague-Dawley rats were randomly divided into either a maternal separation group or a control group. Rats in the maternal separation group received maternal separation from postnatal days 2-15. At the 8^th postnatal week, the abdominal withdrawal reflex (AWR) and electromyographic (EMG) amplitude of the external oblique muscle in response to graded colorectal distension (CRD) were examined. The levels of serum nesfatin-1 and glucocorticoid were detected using ELISA.

RESULTS: At the 8^th postnatal week, the body weight of rats in the maternal separation group was significantly lower than that in the normal control group. The levels of serum nesfatin-1 and glucocorticoid in maternal separation group were statistically higher than those in the control group. The level of glucocorticoid was positively correlated with serum nesfatin-1 level. When the balloon pressure was set at 40, 60 and 80 mmHg, AWR score and EMG amplitude in the maternal separation group were significantly higher than those in the normal control group. AWR score and EMG amplitude in the maternal separation group were positively correlated with the level of serum nesfatin-1.

CONCLUSION: Rats subjected to maternal separation showed a higher AWR score and EMG amplitude, as well as elevated levels of serum nesfatin-1. Visceral hypersensitivity induced by neonatal maternal separation may be associated with elevated level of serum nesfatin-1.

Long-term infusion of nesfatin-1 causes a sustained regulation of whole-body energy homeostasis of male Fischer 344 rats

Nesfatin-1, the N-terminal fragment of nucleobindin 2 (NUCB2), is an 82 amino-acid peptide that inhibits food intake and exerts weight-reducing effects. Nesfatin-1 has been proposed as a potential anti-obesity peptide. However, studies to date have mainly focused on the acute satiety effects of centrally administered nesfatin-1. The main objective of our studies was to characterize the long-term/chronic effects of peripheral administration of nesfatin-1 on whole-body energy balance and metabolic partitioning in male Fischer 344 rats. Short-term (1 day) subcutaneous infusion of nesfatin-1 (50 μg/kg body weight/day) using osmotic mini-pumps increased spontaneous physical activity and whole-body fat oxidation during the dark phase. This was accompanied by decreased food intake and basal metabolic rate compared to saline infused controls. On the seventh day of nesfatin-1 infusion, cumulative food intake, and total spontaneous physical activity during the dark phase were significantly reduced and elevated, respectively. Meanwhile, intraperitoneal injection of nesfatin-1 only caused a dark phase specific reduction in food intake and an increase in physical activity. NUCB2 mRNA expression in the brain and stomach, as well as serum NUCB2 concentrations were significantly reduced after 24 h fasting, while a post-prandial increase in serum NUCB2 was found in ad libitum fed rats. Collectively, our results indicate that chronic peripheral administration of nesfatin-1 at the dose tested, results in a sustained reduction in food intake and modulation of whole body energy homeostasis.

Extreme obesity is associated with variation in genes related to the circadian rhythm of food intake and hypothalamic signaling

The hypothalamus is important for regulation of energy intake. Mutations in genes involved in the function of the hypothalamus can lead to early-onset severe obesity. To look further into this, we have followed a strategy that allowed us to identify rare and common gene variants as candidates for the background of extreme obesity from a relatively small cohort. For that we focused on subjects with a well-selected phenotype and on a defined gene set and used a rich source of genetic data with stringent cut-off values. A list of 166 genes functionally related to the hypothalamus was generated. In those genes complete exome sequence data from 30 extreme obese subjects (60 genomes) were screened for novel rare indel, nonsense, and missense variants with a predicted negative impact on protein function. In addition, (moderately) common variants in those genes were analyzed for allelic association using the general population as reference (false discovery rate<0.05). Six novel rare deleterious missense variants were found in the genes for BAIAP3, NBEA, PRRC2A, RYR1, SIM1, and TRH, and a novel indel variant in LEPR. Common variants in the six genes for MBOAT4, NPC1, NPW, NUCB2, PER1, and PRRC2A showed significant allelic association with extreme obesity. Our findings underscore the complexity of the genetic background of extreme obesity involving rare and common variants of genes from defined metabolic and physiologic processes, in particular regulation of the circadian rhythm of food intake and hypothalamic signaling.

Effects of sleeve gastrectomy and gastric banding on the hypothalamic feeding center in an obese rat model

PURPOSE

Laparoscopic sleeve gastrectomy (SG) and gastric banding (GB) are popular bariatric procedures for treating morbid obesity. This study aimed to investigate changes in the hypothalamic feeding center after these surgeries in a diet-induced obese rat model.

METHODS

Obesity was induced in 60 Sprague-Dawley rats using a high-energy diet for 6 weeks. These rats were divided into four groups: the sham-operated (SO) control, pair-fed (PF) control, SG and GB groups. Six weeks after the surgery, metabolic parameters, the plasma levels of leptin, ghrelin, peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) and the hypothalamic mRNA expressions of neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) were measured.

RESULTS

Compared with those observed in the SO group, the body and fat tissue weights were significantly decreased and the metabolic parameters were significantly improved in the PF, SG and GB groups 6 weeks after surgery. The plasma ghrelin levels were significantly lower and the PYY and GLP-1 levels were significantly higher in the SG group than in the PF, GB and SO groups. Compared with that seen in the PF and GB groups, the hypothalamic mRNA expression of NPY was significantly lower and the expression of POMC was significantly higher in the SG group.

CONCLUSIONS

SG may affect the neurological pathway associated with appetite in the hypothalamus and thereby control ingestive behavior.

The effects of nesfatin-1 in the paraventricular nucleus on gastric motility and its potential regulation by the lateral hypothalamic area in rats

The current study investigated the effects of nesfatin-1 in the hypothalamic paraventricular nucleus (PVN) on gastric motility and the regulation of the lateral hypothalamic area (LHA). Using single unit recordings in the PVN, we show that nesfatin-1 inhibited the majority of the gastric distention (GD)-excitatory neurons and excited more than half of the GD-inhibitory (GD-I) neurons in the PVN, which were weakened by oxytocin receptor antagonist H4928. Gastric motility experiments showed that administration of nesfatin-1 in the PVN decreased gastric motility, which was also partly prevented by H4928. The nesfatin-1 concentration producing a half-maximal response (EC50) in the PVN was lower than the value in the dorsomedial hypothalamic nucleus, while nesfatin-1 in the reuniens thalamic nucleus had no effect on gastric motility. Retrograde tracing and immunofluorescent staining showed that nucleobindin-2/nesfatin-1 and fluorogold double-labeled neurons were observed in the LHA. Electrical LHA stimulation changed the firing rate of GD-responsive neurons in the PVN. Pre-administration of an anti- nucleobindin-2/nesfatin-1 antibody in the PVN strengthened gastric motility and decreased the discharging of the GD-I neurons induced by electrical stimulation of the LHA. These results demonstrate that nesfatin-1 in the PVN could serve as an inhibitory factor to inhibit gastric motility, which might be regulated by the LHA.

Biomarkers in the field of obesity and its related comorbidities

INTRODUCTION

The prevalence of obesity has increased dramatically in the last decades both in children and adults and is now considered a major health problem. It is associated with numerous comorbidities such as hypertension, dyslipidemia, diabetes and subsequent cardiovascular disease (CVD). One of the mechanisms that connect obesity with these comorbidities is the secretion of so-called adipocytokines or adipokines by the adipose tissue itself. Most adipokines with pro-inflammatory properties are overproduced with increasing adiposity, whereas some adipokines with anti-inflammatory or insulin-sensitizing properties, like adiponectin, are decreased. This dysregulation of adipokines production may promote obesity-linked metabolic disorders and CVD. Except adipokines a wide complex network of chemicals balances pro-inflammatory and anti-inflammatory effects.

AREAS COVERED

In this review, we summarize the role of various adipokines and other chemicals associated with obesity and its related cardiometabolic comorbidities, with a special focus on recent evidence showing their potential role as biomarkers whose expression are indicative of obesity and its complications.

EXPERT OPINION

Biomarkers associated with obesity, type 2 diabetes (T2D) and CVD could prove beneficial for early identification, proper treatment and good life assurance. Unfortunately, the complexity of biological pathways interactions is such that further research is necessary before any of these markers could reach an accurate diagnostic value.

Role of NUCB2/Nesfatin-1 in the hypothalamic control of energy homeostasis

Hunger and satiety are regulated in a complex fashion by a few food intake stimulatory (orexigenic) and a multitude of inhibitory (anorexigenic) factors produced in the periphery (mainly in the gastrointestinal tract) or directly in the brain. Within the brain, the hypothalamus plays a pivotal role as a production site of food intake regulatory factors. Importantly, this site integrates peripheral and central signaling factors to orchestrate food intake and in the long term body weight. Our knowledge on these regulatory pathways is not static but rather rapidly changing as new factors as well as up- and downstream signaling pathways of already known transmitters are uncovered. Hypothalamic nucleobindin2 (NUCB2), the precursor of nesfatin-1, was first described in 2006 and nesfatin-1 found to be a novel anorexigenic modulator of food intake and body weight. The initial report stimulated several groups to investigate the biological actions of nesfatin-1 and subsequent studies delineated the underlying brain mechanisms involved in its food reducing effect. Of interest was the demonstration that NUCB2 also exerts its anorexigenic action in the paraventricular nucleus of the hypothalamus and is regulated at this site by changes in metabolic status with a diurnal rhythm inversely related to that of feeding in rats. The present review describes the current state-of-knowledge on central nesfatin-1's effects on food intake and body weight and highlights important missing links regarding cellular signaling mechanisms involved in nesfatin-1's action.

The role of nesfatin-1 in the regulation of food intake and body weight: recent developments and future endeavors

Nesfatin-1 was discovered in 2006 and introduced as a potential novel anorexigenic modulator of food intake and body weight. The past years have witnessed increasing evidence establishing nesfatin-1 as a potent physiological inhibitor of food intake and body weight and unravelled nesfatin-1's interaction with other brain transmitters to exert its food consumption inhibitory effect. As observed for other anorexigenic brain neuropeptides, nesfatin-1 is also likely to exert additional, if not pleiotropic, actions in the brain and periphery. Recent studies established the prominent expression of the nesfatin-1 precursor, nucleobindin2 (NUCB2), in the stomach and pancreas, where nesfatin-1 influences endocrine secretion. This review will highlight the current experimental state-of-knowledge on the effects of NUCB2/nesfatin-1 on food intake, body weight and glucose homeostasis. Potential implications in human obesity will be discussed in relation to the evidence of changes in circulating levels of NUCB2/nesfatin-1 in disease states, the occurrence of genetic NUCB2 polymorphisms and--in contrast to several other hormones--the independence of leptin signalling known to be blunted under conditions of chronically increased body weight.

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.