Feeding regulation by neuropeptide Y on Asian corn borer Ostrinia furnacalis

The Asian Corn Borer Ostrinia furnacalis is a major agricultural pest. In this study, a full‐length neuropeptide Y (npy) gene in O. furnacalis was sequenced and cloned from cDNA library, which contains an ORF of 273 bp by encoding 90 amino acid residues. The mature OfurNPY is composed of 29 amino acids with amidation in C‐terminal. The spatiotemporal expression analysis showed that npy highest expression level was in the midgut of the fifth instar larvae (the gluttony period). When the expression of npy was knocked down by feeding or injecting dsNPY, larval food consumption, body size, and body weight were significantly inhibited compared to controls. These results indicate that NPY is an important regulator in the control of feeding of O. furnacalis.     

Characterization of Schizothorax prenanti cgnrhII gene: fasting affects cgnrhII expression

In this study, the role of chicken gonadotropin‐releasing hormone II (cgnrhII) in feeding regulation was investigated in Schizothorax prenanti. First, the full‐length S. prenanti cgnrhII cDNA consisted of 693 bp with an open reading frame of 261 bp encoding a protein of 86 amino acids. Next, cgnrhII was widely expressed in the central and peripheral tissues. Last, there were significant changes in cgnrhII mRNA expression in the fasted group compared to the fed group in the S. prenanti hypothalamus during 24 h fasting (P < 0·05). Furthermore, the cgnrhII gene expression presented a significant decrease in the fasted group compared with the fed group (P < 0·05) on days 3, 5 and 7, after re‐feeding, there was no significant changes in cgnrhII mRNA expression level between refed and fed group on day 9 (P > 0·05). Thus, the results suggest that cGnRH II expression is influenced by fasting and the gene may be involved in feeding regulation in S. prenanti.     

Characterization,tissue distribution and regulation of agouti-related protein (AgRP) in a cyprinid fish (Schizothorax prenanti)

Agouti-related protein (AgRP) is an important neuropeptide involved in the regulation of feeding in both mammals and fish. In this study, we have cloned the full-length cDNA sequence for AgRP in a cyprinid fish (Schizothorax prenanti). The AgRP gene, encoding 126-amino acids, was strongly expressed in the brain. The AgRP gene was detected in embryos at developmental stages. Further, its mRNA was detectable in unfertilized eggs. An experiment was conducted to determine the expression profile of AgRP during short-term and long-term fasting of the hypothalamus. The expression level of AgRP in unfed fish was significantly increased at 3 and 4 h post-fasting than in fed fish but did not affect AgRP mRNA expression after 14 days fasting. Overall, our results suggest that AgRP is a conserved peptide that might be involved in the regulation of short-term feeding and other physiological function in Schizothorax prenanti.     

Cloning,distribution and effects of fasting status of melanocortin 4 receptor (MC4R) in Schizothorax prenanti

Melanocortin 4 receptor (MC4R) has an important role in the regulation of energy homeostasis in both mammals and fish. In this study, MC4R was characterized in S. prenanti (Schizothorax prenanti) and designated as SpMC4R. SpMC4R cDNA is composed of 1004 nucleotides with a 978 nucleotide open reading frame encoding a protein of 326 amino acids. The SpMC4R contained predicted regions that were structural features of MCR subtypes of vertebrates. In addition, phylogenetic analyses suggested that S. prenanti MC4R was closely related to fish MC4Rs. The SpMC4R mRNA was detected in embryos at developmental stages. Further, its mRNA was detectable in unfertilized eggs. Using real-time RT-PCR, MC4R is widely expressed, with highest levels of expression in brain and ovary. An experiment was conducted to determine the expression profile of MC4R during short-term and long-term fasting of the brain. The expression level of MC4R in unfed fish was significantly increased at 6, 9 and 24 h post-fasting (hpf) and 14 days fasting than in fed fish, this suggests that MC4R is conserved peptide that might be involved in the regulation of food intake and other physiological function in S. prenanti.     

Energy Metabolic Profile of Mice after Chronic Activation of Central NPY Y1, Y2, or Y5 Receptors**

Objective: Neuropeptide Y (NPY), a 36‐amino acid peptide with orexigenic properties, is expressed abundantly in the central nervous system and binds to several NPY receptor subtypes. This study examines the roles of the NPY Y1, Y2, and Y5 receptor(s) in energy homeostasis. Research Methods and Procedures: We administered intracerebroventricular NPY (3 μg/d) or selective peptide agonists for the Y1, Y2, and Y5 receptor subtypes to C57Bl/6 mice for 6 days by mini‐osmotic pumps to assess the role of each receptor subtype in NPY‐induced obesity. Energy expenditure (EE) and respiratory quotient (RQ) were studied using indirect calorimetry. Adiposity was measured by DXA scanning and fat pad dissection. Insulin sensitivity was tested by whole‐blood glucose measurement after an insulin challenge. Results: Central administration of the selective Y1 agonist, Y5 agonist, or NPY for 6 days in mice significantly increased body weight, adiposity, and RQ, with significant hyperphagia in the Y5 agonist‐ and NPY‐treated groups but not in the Y1 agonist‐treated group. The NPY, Y1, or Y5 agonist‐treated mice had little change in total EE during ad libitum and pair‐feeding conditions. Conversely, selective activation of the Y2 receptor reduced feeding and resulted in a significant, but transient, weight loss. Discussion: Central activation of both Y1 and Y5 receptors increases RQ and adiposity, whereas only Y5 receptor activation reduces energy expended per energy ingested. Selective activation of Y2 autoreceptors leads to hypophagia and transient weight loss, with little effect on total EE. Our study indicates that all three NPY receptor subtypes may play a role in regulating energy homeostasis in mice.     

Effects of fasting and feeding on the fast‐start swimming performance of southern catfish Silurus meridionalis

This study investigated the effects of fasting and feeding on the fast‐start escape swimming performance of juvenile southern catfish Silurus meridionalis, a sit‐and‐wait forager that encounters extreme fasting and famine frequently during its lifespan. Ten to 30 days of fasting resulted in no significant change in most of the variables measured in the fast‐start response except a 20–30% decrease in the escape distance during the first 120 ms (D_120ms) relative to the control group (48 h after feeding). The ratio of the single‐bend (SB) response (lower energetic expenditure) to the double‐bend (DB) response increased significantly from 0% in the control group to 75 and 82·5% in the 20 and 30 day fasting groups, respectively. Satiated feeding (25% of body mass) resulted in a significantly lower (36·6%) maximum linear velocity (V_max) and a significantly lower (43·3%) D_120ms than in non‐fed fish (control group, 48 h after feeding). Half‐satiated feeding (12·5% of body mass), however, showed no significant effects on any of the measured variables of the fast‐start response relative to control fish. It is suggested that the increase in the ratio of SB:DB responses with fasting in S. meridionalis may reflect a trade‐off between energy conservation and maintaining high V_max, while variables of fast‐start performance were more sensitive to feeding than fasting might be an adaptive strategy to their foraging mode and food availability in their habitat.     

Looking for Food: Molecular Neuroethology of Invertebrate Feeding Behavior

The assignment of complex behavior of animals to the function of specific genes has seen significant advances in the past decade. The advent of modern tools of genetics and genomics permitted analyses that revealed a good number of neural system enriched genes whose products modulate, and whose polymorphism qualitatively or quantitatively influenced invertebrate feeding behavior. The most prominent of these genes are orthologues of foraging (for) and the neuropeptide Y (NPY)/NPY receptor. The former encodes a cyclic‐GMP‐dependent protein kinase, which functional genetics have been characterized in Drosophila melanogaster, Apis mellifera and Caenorhabditis elegans. Allelic variations and changes in the expression of the above genes could influence the initiation of particular feeding behaviors or related social phenotype. These genes have provided the first molecular insights towards feeding behavior in invertebrates. Besides detailed investigations into the neural pathways involved and mechanisms of function of the gene products, parallel studies in other animal models is imperative to understand ecological drivers of animal feeding behavior.     

Unique gene alterations are induced in FACS‐purified Fos‐positive neurons activated during cue‐induced relapse to heroin seeking

Cue‐induced heroin seeking after prolonged withdrawal is associated with neuronal activation and altered gene expression in prefrontal cortex (PFC). However, these previous studies assessed gene expression in all neurons regardless of their activity state during heroin seeking. Using Fos as a marker of neural activity, we describe distinct molecular alterations induced in activated versus non‐activated neurons during cue‐induced heroin seeking after prolonged withdrawal. We trained rats to self‐administer heroin for 10 days (6 h/day) and assessed cue‐induced heroin seeking in extinction tests after 14 or 30 days. We used fluorescent‐activated cell sorting (FACS) to purify Fos‐positive and Fos‐negative neurons from PFC 90 min after extinction testing. Flow cytometry showed that Fos‐immunoreactivity was increased in less than 10% of sparsely distributed PFC neurons. mRNA levels of the immediate early genes fosB, arc, egr1, and egr2, as well as npy and map2k6, were increased in Fos‐positive, but not Fos‐negative, neurons. In support of these findings, double‐label immunohistochemistry indicated substantial coexpression of neuropeptide Y (NPY)‐ and Arc‐immunoreactivity in Fos‐positive neurons. Our data indicate that cue‐induced relapse to heroin seeking after prolonged withdrawal induces unique molecular alterations within activated PFC neurons that are distinct from those observed in the surrounding majority of non‐activated neurons.     

Importance of Orexigenic Counter‐Regulation for Multiple Targeted Feeding Inhibition

Objective: Central feeding regulation involves both anorectic and orexigenic pathways. This study examined whether targeting both systems could enhance feeding inhibition induced by anorectic neuropeptides. Research Methods and Procedures: Experiments were carried out in 24‐hour fasted rats. Intracerebroventricular (ICV) injections were accomplished through stereotaxically implanted cannulae aimed at the lateral cerebral ventricle. Food intake of standard rat chow pellets was subsequently recorded for 2 hours. Results: Blockade of orexigenic central opioids and neuropeptide Y (NPY) by ICV naloxone (25 μg) or the NPY receptor antagonist [d‐Trp³²]NPY (NPY‐Ant; 10 μg) powerfully augmented the feeding suppression induced by ICV glucagon‐like peptide 1 (7‐36)‐amide (GLP‐1; 10 μg) or xenin‐25 (xenin; 15 μg) in 24‐hour fasted rats. Most importantly, in combination with naloxone or NPY‐Ant, even a low and ineffective dose of GLP‐1 (5 μg) caused a 40% reduction of food intake, which was augmented further when both antagonists were given in combination with GLP‐1. The combination of GLP‐1 (5 μg) and xenin (10 μg) at individually ineffective doses caused a 46% reduction of food intake, which was abolished at a 10‐fold lower dose. This ineffective dose, however, reduced food intake by 72% when administered in combination with naloxone and NPY‐Ant. Discussion: Targeting up to four pathways of feeding regulation in the central nervous system by blockade of endogenous feeding stimuli and simultaneous administration of anorectic neuropeptides potentiated reduction of food intake. This raises a promising perspective for treatment of obesity.     

Identification, tissue distribution and evaluation of brain neuropeptide Y gene expression in the Brazilian flounder Paralichthys orbignyanus

Neuropeptide Y (NPY) is one of the most potent stimulants of food intake in vertebrates, mammals and fish. However, the present knowledge about feeding behaviour in fish is still limited and based on studies in a few species. The Brazilian flounder Paralichthys orbignyanus is being considered for aquaculture, and it is important to understand the mechanisms regulating feeding in order to improve its performance in captivity. The objectives of this study were to clone NPY cDNA, evaluate the mRNA levels in different tissues of flounder, and also evaluate brain NPY expression to associate food intake with NPY expression levels. A 597 bp NPY cDNA was cloned from Brazilian flounder brain. NPY expression was detected in all the peripheral tissues analysed. No significant differences were observed in brain NPY gene expression over 24 h after food intake at a temperature of 15 ± 3°C. No correlation was observed among plasma glucose, total protein, cholesterol, triglycerides and NPY expression levels during this 24 h period. On the other hand, mRNA levels were increased after two weeks of fasting at elevated temperatures. Our results suggest that NPY mRNA levels in Brazilian flounder are affected by temperature.     

Neuropeptide Y gene expression around meal time in the Brazilian flounder Paralichthys orbignyanus

Neuropeptide Y (NPY) is considered the major stimulant for food intake in mammals and fish. Previous results indicate that NPY is involved in the feeding behaviour of the Brazilian flounder, Paralichthys orbignyanus. In this study, we evaluated hypothalamic NPY expression before (-2 h), during (0 h) and after feeding (+2 h) in two independent experiments: (1) during a normal feeding schedule and (2) in fish fasted for 2 weeks. During normal feeding, changes in the levels of NPY mRNA were periprandial, with expression levels being significantly elevated at meal time (P less than 0.05) and significantly reduced 2 h later (P less than 0.05). Comparing the fasting and unfasted groups, NPY mRNA levels were significantly higher (P less than 0.05) at -2 h and +2 h in the fasting group, but there was no difference at 0 h. In addition, the higher NPY mRNA levels that were observed in the fasting group were maintained throughout the sampling period. In summary, our results show that NPY expression was associated with meal time (0 h) in food intake regulation.     

大鼠NPY Y2受体基因的克隆及C端肽的表达和纯化

Y2受体亚型是早期发现的NPY的两种主要受体亚型之一,参与NPY所介导的多种生理和病理功能.为了制备Y2受体抗体和开展Y2受体的定位研究,用RT-PCR方法从大鼠海马的总RNA扩增NPY的Y2受体全长基因,接着PCR扩增Y2受体的C端片段,克隆入表达载体中,建立了重组NPY Y2受体C端肽的表达菌株,并对表达产物进行纯化.     

Resonant recognition model of neuropeptide Y family: hot spot amino acid distribution in the sequences

The resonant recognition model is used to predict structurally and functionally important amino acid residues (so-called hot spots) in the neuropeptide Y (NPY) family. Thirty-three polypeptides belong to this family. All of them consist of 36 amino acids. The model predicts that residues 10 and 28 in the polypeptides are hot spots. In the 33 polypeptides, most of the amino acids at residue 10 are acidic amino acids, glutamic acid and aspartic acid. Other minor amino acids, serine, glycine, and proline, have high probabilities of -turn occurrence. Amino acids at residue 28 are all branched hydrophobic amino acids, isoleucine, leucine, and valine. The profile for predicting hot spots indicates repeating patterns of residues 1–18 and residues 19–36. Absolute values at residue i and residue i + 18 are the same, but these residues have opposite signs. Therefore the model of the NPY family predicts hot spots concerning a combination of residue i and residue i + 18.