Novel Neuropeptides in the Control of Food Intake

Nesfatin-1 is a regulator of inflammation with implications during obesity and metabolic syndrome

Nesfatin-1, derived from the nucleobindin 2 (NUCB2) precursor, is a potent anorexigenic peptide that was discovered in 2006. Since its identification in the hypothalamus, it has been shown to have wide ranging actions within and outside of the central nervous system. One of these actions is the regulation of inflammation, which could potentially be exploited therapeutically in the context of obesity-associated inflammation in adipose tissue. Here, we review recent advances in our knowledge about the ability of nesfatin-1 to control inflammation by regulating NFκB signaling, which likely attenuates pro-inflammatory cytokine production and inhibits apoptosis.

Emerging functions of neuronostatin in physiology, pathology, and potential therapeutics

Neuronostatin, a bioactive peptide hormone, was encoded by pro-somatostatin and discovered using a bioinformatic method in 2008. Neuronostatin is widely expressed in the central nervous system (CNS) and peripheral tissues, it is also highly conserved among humans, rodents, and even goldfish. The 13 and 19 amino acids and the C-terminal amidation type play important roles in physiological and pathological functions. The present study reviews the roles of neuronostatin in food intake and drinking of water, as well as in the neuroendocrine processes, pain regulation, cardiovascular and circulation function, memory and studies, depression-like effect, and energy metabolism in animals. However, the information on the physiology and pathology of neuronostatin, especially the molecular mechanism, remains scarce. Considering the broad functions of neuronostatin, this endogenous neuropeptide could be a promising therapeutic target for future research and drug design if the exact receptor could be found in humans.

The effects of neuronostatin on proliferation and differentiation of rat primary preadipocytes and 3T3-L1 cells

Neuronostatin is a peptide hormone encoded by the somatostatin gene. Biological effects of neuronostatin are mediated through activation of GPR107. There is evidence indicating that neuronostatin modulates energy homeostasis by suppressing food intake and insulin secretion, while stimulating glucagon secretion. While it was found that neuronostatin receptor is expressed in white adipose tissue, the role of neuronostatin in controlling adipose tissue formation is unknown. The aim of this study is to investigate the effects of neuronostatin on proliferation and differentiation of rat primary preadipocytes and 3T3-L1 cells. We found that neuronostatin receptor GPR107 is expressed in rat preadipocytes and 3T3-L1 cells. Neuronostatin promotes proliferation of preadipocytes via AKT activation. Downregulation of GPR107 mRNA expression and protein production results in an attenuation of neuronostatin-induced stimulation of preadipocyte proliferation. Moreover, neuronostatin reduces intracellular lipid content and the expression of adipogenesis-modulating genes C/ebpα, C/ebpβ, Pparγ, and Fabp4. In summary, these results show that neuronostatin, AKT-dependently, stimulates the proliferation of preadipocytes via GPR107. In contrast, neuronostatin inhibits the differentiation of preadipocytes into mature adipocytes.

Increased hip circumference in individuals with metabolic syndrome affects serum nesfatin-1 levels

Background

This case–control study was conducted to investigate the relationship between serum nesfatin-1 levels and nutritional status and blood parameters in patients diagnosed with metabolic syndrome.

Methods

Thirty patients (case) diagnosed with metabolic syndrome according to National Cholesterol Education Program-Adult Treatment Panel III criteria were included. Thirty healthy subjects (control) matched with patients with metabolic syndrome in terms of age, gender and body mass index were included. Three-day food consumption records were obtained. Anthropometric indices were measured and body composition was determined by bioelectrical impedance method. Biochemical parameters and serum nesfatin-1 levels were measured after 8 hours of fasting.

Results

Serum nesfatin-1 levels were 0.245±0.272 ng/mL in the case group and 0.528±0.987 ng/mL in the control group (p>0.05). There was a positive significant correlation between serum nesfatin-1 levels and body weight, waist and hip circumferences in the case group (p<0.05). Each unit increase in hip circumference measurement affects the levels of nesfatin by 0.014 times. In the control group, there was a positive significant correlation between body weight and serum nesfatin-1 levels (p<0.05). A significant correlation was detected between HbA1c and serum nesfatin-1 levels in the case group (p<0.05). A significant relationship was detected between dietary fibre intake and the serum nesfatin-1 levels in the case group (p<0.05).

Conclusions

Anthropometric indices and blood parameters were correlated with serum nesfatin-1 levels in patients with metabolic syndrome. More clinical trials may be performed to establish the relationship between serum nesfatin-1 levels and nutritional status.

Regulatory Peptide Nesfatin-1 and its Relationship with Metabolic Syndrome

Metabolic syndrome is associated with a group of conditions abdominal obesity, high triglyceride levels, reduction in low-density lipoprotein, increased blood pressure, and increased fasting blood glucose. Hence, it poses a risk for type 2 diabetes and cardiovascular diseases. The prevalence of metabolic syndrome increases with age. Nesfatin-1, which affects different systems, has recently been discovered as a regulatory peptide molecule. With the discovery of nesfatin-1, it has been reported to inhibit the intake of nutrients and have significant regulatory effects on energy metabolism. As nesfatin-1 is present in both central and peripheral tissues, it is thought to have many functions. In addition to its suppressive effect on food intake, nesfatin-1 has also been reported to have an effect on the blood glucose level for regulating cardiac functions and affecting obesity by providing weight loss. Considering the effects of nesfatin-1, it may be associated with metabolic syndrome.

Role of Nesfatin-1 in the Reproductive Axis of Male Rat

Nesfatin-1 is an important molecule in the regulation of reproduction. However, its role in the reproductive axis in male animals remains to be understood. Here, we found that nesfatin-1 was mainly distributed in the arcuate nucleus (ARC), paraventricular nucleus (PVN), periventricular nucleus (PeN), and lateral hypothalamic area (LHA) of the hypothalamus; adenohypophysis and Leydig cells in male rats. Moreover, the concentrations of serum nesfatin-1 and its mRNA in hypothalamo-pituitary-gonadal axis (HPGA) vary with the age of the male rat. After intracerebroventricular injection of nesfatin-1, the hypothalamic genes for gonadotrophin releasing hormone (GnRH), kisspeptin (Kiss-1), pituitary genes for follicle-stimulate hormone β(FSHβ), luteinizing hormone β(LHβ), and genes for testicular steroidogenic acute regulatory (StAR) expression levels were decreased significantly. Nesfatin-1 significantly increased the expression of genes for 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), and cytochrome P450 cleavage (P450scc) in the testis of pubertal rats, but their levels decreased in adult rats (P < 0.05), along with the serum FSH, LH, and testosterone (T) concentrations. After nesfatin-1 addition in vitro, T concentrations of the supernatant were significantly higher than that in the control group. These results were suggestive of the role of nesfatin-1 in the regulation of the reproductive axis in male rats.

Neuronostatin: peripheral site of action in mouse stomach

Neuronostatin is a 13-amino acid peptide encoded by somatostatin gene. It is distributed in different organs including gastrointestinal tract and has been involved in the control of food intake and gastrointestinal motility, likely through an action in the brain. So far, there are no reports about the occurrence of peripheral action sites in the gut. Therefore, the purpose of the present study was to examine, in the mouse, the effects of peripheral administration of neuronostatin on food intake within 24h and on gastrointestinal motility and to analyse neuronostatin actions on the gastric and intestinal mechanical activity in isolated preparations in vitro. When compared with PBS-treated mice, intraperitoneal neuronostatin reduced food intake in doses ranging from 1 to 15ng/g b.w. only in the first hour postinjection with a maximum effect obtained at the dose of 15ng/g b.w. (-46.9%). The peptide (15ng/g b.w.) significantly reduced gastric emptying rate (-31.1%) and gastrointestinal intestinal transit. Non-amidated neuronostatin failed to affect food intake, gastric emptying and intestinal transit, suggesting the specificity of action. In vitro, neuronostatin induced concentration-dependent gastric relaxation, which was abolished by tetrodotoxin. Neuronostatin failed to affect the spontaneous mechanical activity or the evoked cholinergic contractions in duodenum. These results suggest that exogenous neuronostatin is able to reduce mouse gastric motility by acting peripherally in the stomach, through intramural nervous plexuses. This indirectly action could cause reduction of food intake in the short term.