Lesion of NPY Receptor-expressing Neurons in Perifornical Lateral Hypothalamus Attenuates Glucoprivic Feeding.

Glucoprivic feeding is one of several counterregulatory responses (CRRs) that facilitates restoration of euglycemia following acute glucose deficit (glucoprivation). Our previous work established that glucoprivic feeding requires ventrolateral medullary (VLM) catecholamine (CA) neurons that coexpress neuropeptide Y (NPY). However, the connections by which VLM CA/NPY neurons trigger increased feeding are uncertain. We have previously shown that glucoprivation, induced by an anti-glycolygic agent 2-deoxy-D-glucose (2DG), activates perifornical lateral hypothalamus (PeFLH) neurons and that expression of NPY in the VLM CA/NPY neurons is required for glucoprivic feeding. We therefore hypothesized that glucoprivic feeding and possibly other CRRs require NPY-sensitive PeFLH neurons. To test this, we used the ribosomal toxin conjugate NPY-saporin (NPY-SAP) to selectively lesion NPY receptor-expressing neurons in the PeFLH of male rats. We found that NPY-SAP destroyed a significant number of PeFLH neurons, including those expressing orexin, but not those expressing melanin-concentrating hormone. The PeFLH NPY-SAP lesions attenuated 2DG-induced feeding but did not affect 2DG-induced increase in locomotor activity, sympathoadrenal hyperglycemia, or corticosterone release. The 2DG-induced feeding response was also significantly attenuated in NPY-SAP-treated female rats. Interestingly, PeFLH NPY-SAP lesioned male rats had reduced body weights and decreased dark cycle feeding, but this effect was not seen in female rats. We conclude that a NPY projection to the PeFLH is necessary for glucoprivic feeding, but not locomotor activity, hyperglycemia, or corticosterone release, in both male and female rats.

Ninjin'yoeito modulates feeding and activity under negative energy balance conditions via the NPY system.

The central and peripheral neuropeptide Y (NPY) system is critically involved in feeding and energy homeostasis control. Disease conditions as well as aging can lead to reduced functionality of the NPY system and boosting it represents a promising option to improve health outcomes in these situations. Here we show that Ninjin-yoeito (NYT), a Japanese kampo medicine comprising twelve herbs, and known to be effective to treat anorexia and frailty, mediates part of its action via NPY/peptide YY (PYY) related pathways. Especially under negative energy homeostasis conditions NYT is able to promote feeding and reduces activity to conserve energy. These effects are in part mediated via signalling through the NPY system since lack of Y4 receptors or PYY leading to modification in these responses highlighting the possibility for combination treatment to improve aging related conditions on energy homeostasis control.

Conditional inactivation of Npy1r gene in mice induces sex-related differences of metabolic and behavioral functions.

Sex hormone-driven differences in gene expression have been identified in experimental animals, highlighting brain neuronal populations implicated in dimorphism of metabolic and behavioral functions. Neuropeptide Y-Y1 receptor (NPY-Y1R) system is sexually dimorphic and sensitive to gonadal steroids. In the present study we compared the phenotype of male and female conditional knockout mice (Npy1rrfb mice), carrying the inactivation of Npy1r gene in excitatory neurons of the brain limbic system. Compared to their male control (Npy1r2lox) littermates, male Npy1rrfb mice exhibited hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis that is associated with anxiety and executive dysfunction, reduced body weight growth, after-fasting refeeding, white adipose tissue (WAT) mass and plasma leptin levels. Conversely, female Npy1rrfb mice displayed an anxious-like behavior but no differences in HPA axis activity, executive function and body weight, compared to control females. Moreover, conditional inactivation of Npy1r gene induced an increase of subcutaneous and gonadal WAT weight and plasma leptin levels and a compensatory decrease of Agouti-related protein immunoreactivity in the hypothalamic arcuate (ARC) nucleus in females, compared to their respective control littermates. Interestingly, Npy1r mRNA expression was reduced in the ARC and in the paraventricular hypothalamic nuclei of female, but not male mice. These results demonstrated that female mice are resilient to hormonal and metabolic effects of limbic Npy1r gene inactivation, suggesting the existence of an estrogen-dependent relay necessary to ensure the maintenance of the homeostasis, that can be mediated by hypothalamic Y1R.

Emerging therapeutic potential for peptide YY for obesity-diabetes.

The vast majority of research to date on the gut hormone Peptide YY (PYY) has focused on appetite suppression and body weight regulation effects. These biological actions are believed to occur through interaction of PYY with hypothalamic Y2 receptors. However, more recent studies have added additional knowledge to understanding of the physiological, and potential therapeutic, roles of PYY beyond obesity alone. Thus, PYY has now been shown to impart improvements in pancreatic beta-cell survival and function, with obvious benefits for diabetes. This effect has been linked mainly to binding and activation of Y1 receptors by PYY, but more evidence is still required in this regard. Given the potential therapeutic promise of PYY-derived compounds, and complexity of receptor interactions, it is important to fully understand the complete biological action profile of PYY. Therefore, the current review aims to compile, evaluate and summarise current knowledge on PYY, with particular emphasis on obesity and diabetes treatment, and the importance of specific Y receptor interactions for this.

Knockdown of the transcript of ERK in the brain modulates hypothalamic neuropeptide-mediated appetite control in amphetamine-treated rats.

BACKGROUND AND PURPOSE: Amphetamine is a releaser of dopamine stored in synaptic terminals, which can suppress appetite by changing the expression levels of neuropeptide Y (NPY) and proopiomelanocortin (POMC) in the hypothalamus. This study explored whether ERKs are involved in appetite control mediated by cAMP response element binding protein (CREB), NPY and POMC in amphetamine-treated rats. EXPERIMENTAL APPROACH: Rats were given amphetamine for 4 days, and changes in feeding behaviour and expression levels of phosphorylated-ERK (pERK), pCREB, NPY and melanocortin MC3 receptors were examined and compared. KEY RESULTS: Following amphetamine treatment, food intake, body weight and NPY expression decreased, whereas the expression of pERK, pCREB, MC3 receptors and pCREB/DNA binding activity increased. In amphetamine-treated rats, both cerebral ERK knockdown and pretreatment with a peripheral dopamine receptor antagonist decreased NPY but increased pERK, pCREB and MC3 receptor expression. Moreover, the immunofluorescence of hypothalamic pERK increased following amphetamine treatment. CONCLUSIONS AND IMPLICATIONS: These results suggest that ERK/CREB signalling participates in the effects mediated by dopamine receptor/NPY/POMC on appetite control in rats treated with amphetamine. These findings advance the knowledge on the involvement of ERK/CREB signalling in the reciprocal regulation by NPY and POMC of appetite after amphetamine treatment.

Dietary macronutrient composition affects hypothalamic appetite regulation in chicks.

OBJECTIVE: The objective was to determine the effects of high-protein and high-fat diets, and fasting and refeeding, on appetite regulation in chicks. METHODS: Day of hatch chicks were fed one of four diets: basal, high protein (25% crude protein), and 15 and 30% high fat (15 and 30% metabolizable energy derived from soybean oil, respectively), and assigned to one of three treatments at 4 days: (1) access to feed, (2) 3 hours of fasting, or (3) fasting followed by 1 hour of refeeding. The hypothalamus was collected, total RNA isolated, and mRNA abundance measured. RESULTS: Food intake was reduced in chicks fed the high-protein and high-fat diets. Agouti-related peptide, neuropeptide Y (NPY), NPY receptors 1, 2, and 5, melanocortin receptors 3 and 4 (MC3R and 4R, respectively), mesotocin, corticotropin-releasing factor (CRF), and CRF receptor sub-type 2 (CRFR2) mRNAs were greatest in chicks that consumed the basal diet. Refeeding was associated with increased MC3R mRNA in the high-protein diet group. CRFR2 mRNA was increased by fasting and refeeding in chicks that consumed the high-protein diet. DISCUSSION: Food intake and hypothalamic gene expression of some important appetite-associated factors were reduced in chicks fed the high-protein or high-fat diets. Fasting and refeeding accentuated several differences and results suggest that the CRF and melanocortin pathways are involved.

Dietary macronutrient composition and central neuropeptide Y injection affect dietary preference and hypothalamic gene expression in chicks.

OBJECTIVE: The objective of this study was to determine the influence of dietary macronutrient composition on central NPY's orexigenic effect in chicks. METHODS: Day-of-hatch chicks were fed one of three diets (3000 kcal ME/kg) ad libitum from hatch: high carbohydrate (HC), high fat (HF; 30% ME derived from soybean oil), and high protein (HP; 25 vs. 22% CP). In Experiment 1, chicks received intracerebroventricular injections of 0 (vehicle), 0.2, or 2.0 nmol NPY on day 4 and food intake was recorded for 6 hours. In Experiment 2, chicks were given all three diets before and after injection. In Experiment 3, hypothalamus was collected at 1-hour post-injection for gene expression analysis. RESULTS: The HC diet-fed chicks responded with a greater increase, while the chicks fed the HF diet had a lower threshold response in food intake to NPY. Neuropeptide Y dose-dependently increased food intake in chicks fed the HC and HP diets. Chicks administered 0.2 nmol NPY preferred the HC and HP diets over the HF diet. Relative quantities of hypothalamic NPYR1 and MC4R mRNA were reduced by NPY in chicks that consumed the HP and HC diets, respectively. DISCUSSION: Consumption of the HC diet was associated with the most robust NPY-induced increase in food intake. Injection of NPY accentuated differences among dietary groups in hypothalamic gene expression of several appetite-associated factors, results suggesting that the NPY/agouti-related peptide and melanocortin pathways are associated with some of the diet- and NPY-induced differences observed in this study.

Maternal high-fat diet induces metabolic stress response disorders in offspring hypothalamus.

Maternal obesity has been shown to increase the risk of obesity and related disorders in the offspring, which has been partially attributed to changes of appetite regulators in the offspring hypothalamus. On the other hand, endoplasmic reticulum (ER) stress and autophagy have been implicated in hypothalamic neuropeptide dysregulation, thus may also play important roles in such transgenerational effect. In this study, we show that offspring born to high-fat diet-fed dams showed significantly increased body weight and glucose intolerance, adiposity and plasma triglyceride level at weaning. Hypothalamic mRNA level of the orexigenic neuropeptide Y (NPY) was increased, while the levels of the anorexigenic pro-opiomelanocortin (POMC), NPY1 receptor (NPY1R) and melanocortin-4 receptor (MC4R) were significantly downregulated. In association, the expression of unfolded protein response (UPR) markers including glucose-regulated protein (GRP)94 and endoplasmic reticulum DNA J domain-containing protein (Erdj)4 was reduced. By contrast, protein levels of autophagy-related genes Atg5 and Atg7, as well as mitophagy marker Parkin, were slightly increased. The administration of 4-phenyl butyrate (PBA), a chemical chaperone of protein folding and UPR activator, in the offspring from postnatal day 4 significantly reduced their body weight, fat deposition, which were in association with increased activating transcription factor (ATF)4, immunoglobulin-binding protein (BiP) and Erdj4 mRNA as well as reduced Parkin, PTEN-induced putative kinase (PINK)1 and dynamin-related protein (Drp)1 protein expression levels. These results suggest that hypothalamic ER stress and mitophagy are among the regulatory factors of offspring metabolic changes due to maternal obesity.

Dietary overload lithium decreases the adipogenesis in abdominal adipose tissue of broiler chickens.

To investigate the toxic effects of dietary overload lithium on the adipogenesis in adipose tissue of chicken and the role of hypothalamic neuropeptide Y (NPY) in this process, one-day-old male chicks were fed with the basal diet added with 0 (control) or 100mg lithium/kg diet from lithium chloride (overload lithium) for 35days. Abdominal adipose tissue and hypothalamus were collected at day 6, 14, and 35. As a percentage of body weight, abdominal fat decreased (p<0.001) at day 6, 14, and 35, and feed intake and body weight gain decreased during day 7-14, and day 15-35 in overload lithium treated broilers as compared to control. Adipocyte diameter and DNA content in abdominal adipose tissue were significantly lower in overload-lithium treatment than control at day 35, although no significant differences were observed at day 6 and 14. Dietary overload lithium decreased (p<0.01) transcriptional expression of preadipocyte proliferation makers ki-67 (KI67), microtubule-associated protein homolog (TPX2), and topoisomerase 2-alpha (TOP2A), and preadipocyte differentiation transcriptional factors peroxisome proliferator-activated receptor-γ (PPARγ), and CCAAT/enhancer binding protein (C/EBP) α mRNA abundance in abdominal adipose tissue. In hypothalamus, dietary overload lithium influenced (p<0.001) NPY, and NPY receptor (NPYR) 6 mRNA abundance at day 6 and 14, but not at day 35. In conclusion, dietary overload lithium decreased the adipogenesis in abdominal adipose tissue of chicken, which was accompanied by depressing transcriptional expression of adipogenesis-associated factors. Hypothalamic NPY had a potential role in the adipogenesis in abdominal adipose tissue of broilers with a short-term overload lithium treatment.

Duplication of neuropeptide Y and peptide YY in Nile tilapia Oreochromis niloticus and their roles in food intake regulation.

In vertebrates, the neuropeptide Y (NPY) family peptides have been recognized as key players in food intake regulation. NPY centrally promotes feeding, while peptide YY (PYY) and pancreatic polypeptide (PP) mediate satiety. The teleost tetraploidization is well-known to generate duplicates of both NPY and PYY; however, the functional diversification between the duplicate genes, especially in the regulation of food intake, remains unknown. In this study, we identified the two duplicates of NPY and PYY in Nile tilapia (Oreochromis niloticus). Both NPYa and NPYb were primarily expressed in the central nervous system (CNS), but the mRNA levels of NPYb were markedly lower than those of NPYa. Hypothalamic mRNA expression of NPYa, but not NPYb, decreased after feeding and increased after 7-days of fasting. However, both NPYa and NPYb caused a significant increase in food intake after an intracranial injection of 50ng/g body weight dose. PYYb, one of the duplicates of PYY, had an extremely high expression in the foregut and midgut, whereas another form of duplicate PYYa showed only moderate expression in the CNS. Both hypothalamic PYYa and foregut PYYb mRNA expression increased after feeding and decreased after 7-days of fasting. Furthermore, the intracranial injection of PYYb decreased food intake, but PYYa had no significant effect. Our results suggested that although the mature peptides of NPYa and NPYb can both stimulate food intake, NPYa is the main endogenous functional NPY for feeding regulation. A functional division has been identified in the duplicates of PYY, which deems PYYb as a gut-derived anorexigenic peptide and PYYa as a CNS-specific PYY in Nile tilapia.

Neuropeptide Y1 Receptor Regulates Glucocorticoid-Induced Inhibition of Osteoblast Differentiation in Murine MC3T3-E1 Cells via ERK Signaling.

High dose glucocorticoid (GC) administration impairs the viability and function of osteoblasts, thus causing osteoporosis and osteonecrosis. Neuropeptide Y1 receptor (Y1 receptor) is expressed in bone tissues and cells, and regulates bone remodeling. However, the role of Y1 receptor in glucocorticoid-induced inhibition of osteoblast differentiation remains unknown. In the present study, osteoblastic cell line MC3T3-E1 cultured in osteogenic differentiation medium was treated with or without of 10-7 M dexamethasone (Dex), Y1 receptor shRNA interference, Y1 receptor agonist [Leu31, Pro34]-NPY, and antagonist BIBP3226. Cell proliferation and apoptosis were assessed by cell counting kit-8 (CCK-8) assay and cleaved caspase expression, respectively. Osteoblast differentiation was evaluated by Alizarin Red S staining and osteogenic marker gene expressions. Protein expression was detected by Western blot analysis. Dex upregulated the expression of Y1 receptor in MC3T3-E1 cells associated with reduced osteogenic gene expressions and mineralization. Blockade of Y1 receptor by shRNA transfection and BIBP3226 significantly attenuated the inhibitory effects of Dex on osteoblastic activity. Y1 receptor signaling modulated the activation of extracellular signal-regulated kinases (ERK) as well as the expressions of osteogenic genes. Y1 receptor agonist inhibited ERK phosphorylation and osteoblast differentiation, while Y1 receptor blockade exhibited the opposite effects. Activation of ERK signaling by constitutive active mutant of MEK1 (caMEK) abolished Y1 receptor-mediated Dex inhibition of osteoblast differentiation in MC3T3-E1 cells. Taken together, Y1 receptor regulates Dex-induced inhibition of osteoblast differentiation in murine MC3T3-E1 cells via ERK signaling. This study provides a novel role of Y1 receptor in the process of GC-induced suppression in osteoblast survival and differentiation.

Association analysis between feed efficiency studies and expression of hypothalamic neuropeptide genes in laying ducks.

Residual feed intake (RFI) is now considered a more reasonable metric to evaluate animal feed efficiency. In this study, the correlation between RFI and other feed efficiency traits was investigated and gene expression within the hypothalamus was determined in low RFI (LRFI) and high RFI (HRFI) ducks. Further, several hypothalamic neuropeptide genes were measured using quantitative real-time PCR. The mean feed intake value was 160 g/day, whereas the egg mass laid (EML) and body weight were approximately 62.4 g/day and 1.46 kg respectively. Estimates for heritability of RFI, feed conversion ratio (FCR) and feed intake were 0.26, 0.18 and 0.23 respectively. RFI is phenotypically positively correlated with feed intake and FCR (P < 0.01). The expression of neuropeptide Y (NPY) and neuropeptide Y receptor Y5 (NPY5R) mRNA was higher in HRFI ducks compared with LRFI ducks (P < 0.05), whereas that of proopiomelanocortin (POMC), melanocortin 4 receptor (MC4R) and cholecystokinin (CCK) was lower (P < 0.05). The mRNA expression of gonadotropin-releasing hormone 1 (luteinizing-releasing hormone) (GNRH1) and prolactin receptor (PRLR) was unchanged between LRFI and HRFI ducks. The results indicate that selection for LRFI could reduce feed intake without significant changes in EML, whereas selection on FCR will increase EML.

Attenuated Weight Gain with the Novel Analog of Olanzapine Linked to Sarcosinyl Moiety (PGW5) Compared to Olanzapine.

Olanzapine-induced weight gain is associated with atherosclerosis, hypertension, dyslipidemia, and diabetes. We synthesized a novel antipsychotic drug (PGW5) possessing an olanzapine moiety linked to sarcosine, a glycine transporter 1 inhibitor. In this study, we compared the metabolic effects of PGW5 and olanzapine in a female rat model of weight gain. Female rats were treated daily with oral olanzapine (4 mg/kg), PGW5 (25 mg/kg), or vehicle for 16 days. Behavioral tests were conducted on days 12-14. Biochemical analyses were performed at the end of the treatment. A significant increase in body weight was observed in the olanzapine-treated group, while the PGW5 group did not differ from the controls. The open field test showed hypo-locomotion in the olanzapine-treated animals as compared to PGW5 and control groups. A significant increase in hypothalamic protein expression of the neuropeptide Y5 receptor and a decrease in pro-opiomelanocortin messenger ribonucleic acid (mRNA) levels were detected following PGW5 treatment, but not after olanzapine administration. PGW5 appears to possess minor metabolic effects compared with the parent compound olanzapine. The differential modulation of brain peptides associated with appetite regulation is possibly involved in the attenuation of metabolic effects by PGW5.

Chronic gastric electrical stimulation leads to weight loss via modulating multiple tissue neuropeptide Y, orexin, α-melanocyte-stimulating hormone and oxytocin in obese rats.

OBJECTIVES: Gastric electrical stimulation (GES) has great potential for the treatment of obesity. We investigated the impact of chronic GES on the alteration of adipose tissue and the regulation of neuropeptide Y (NPY), orexin (OX), α-melanocyte-stimulating hormone (α-MSH) and oxytocin (OXT), and their receptors in several tissues. MATERIAL AND METHODS: Most of the experiments included three groups of diet-induced obesity rats: (1) sham-GES (SGES); (2) GL-6mA (GES with 6 mA, 4 ms, 40 Hz, 2 s on, 3 s off at lesser curvature); and (3) SGES-PF (SGES rats receiving pair feeding to match the consumption of GL-6mA rats). Chronic GES was applied for 2 h every day for 4 weeks. During treatment with GES, food intake and body weight were monitored weekly. The alteration of epididymal fat weight, gastric emptying, and expression of peptides and their receptors in several tissues were determined. RESULTS: GL-6mA was more potent than SGES-PF in decreasing body weight gain, epididymal fat tissue weight, adipocyte size and gastric emptying. Chronic GES significantly altered NPY, OX, α-MSH and OXT and their receptors in the hypothalamus, adipose tissue and stomach. CONCLUSIONS: Chronic GES effectively leads to weight loss by reducing food intake, fat tissue weight and gastric emptying. NPY, α-MSH, orexin and OXT, and their receptors in the hypothalamus, adipose tissue and stomach appear to be involved in the anti-obesity effects of chronic GES.

Actions of NPY, and its Y1 and Y2 receptors on pulsatile growth hormone secretion during the fed and fasted state.

The hypothalamic NPY system plays an important role in regulating food intake and energy expenditure. Different biological actions of NPY are assigned to NPY receptor subtypes. Recent studies demonstrated a close relationship between food intake and growth hormone (GH) secretion; however, the mechanism through which endogenous NPY modulates GH release remains unknown. Moreover, conclusive evidence demonstrating a role for NPY and Y-receptors in regulating the endogenous pulsatile release of GH does not exist. We used genetically modified mice (germline Npy, Y1, and Y2 receptor knock-out mice) to assess pulsatile GH secretion under both fed and fasting conditions. Deletion of NPY did not impact fed GH release; however, it reversed the fasting-induced suppression of pulsatile GH secretion. The recovery of GH secretion was associated with a reduction in hypothalamic somatotropin release inhibiting factor (Srif; somatostatin) mRNA expression. Moreover, observations revealed a differential role for Y1 and Y2 receptors, wherein the postsynaptic Y1 receptor suppresses GH secretion in fasting. In contrast, the presynaptic Y2 receptor maintains normal GH output under long-term ad libitum-fed conditions. These data demonstrate an integrated neural circuit that modulates GH release relative to food intake, and provide essential information to address the differential roles of Y1 and Y2 receptors in regulating the release of GH under fed and fasting states.

Ginseng panaxoside Rb1 reduces body weight in diet-induced obese mice.

Crude extracts from ginseng demonstrated anti-obesity properties. Ginsenoside Rb1 is the main component of ginseng, however, there are only few studies examining its effects in obesity. In the present study, we evaluated its potential anti-obesity effects in the murine model of diet-induced obesity. Seventy male C57BL/6 mice were randomly divided to consume for 12 weeks either chow diet (N = 8) or high-fat (HF) diet (N = 62). The latter mice were then divided into four groups: diet-induced obesity group (DIO; N = 10), obesity-resistant group (OR; N = 10), HF group (N = 5), and the group whose diet was changed from HF to normal diet (DC; N = 5). Intraperitoneal injections of Rb-1 were administered daily to mice in the DIO and OR groups for 3 weeks. Body weight and energy intake were monitored, and fasting blood glucose, lipids, neuropeptide Y, Y2 receptor, and peptide YY were quantified. Compared with HF group, weight gain and food intake of DIO mice with Rb-1 injection was significantly decreased (p < 0.05). Further, levels of blood glucose and some lipids were also decreased in DIO-Rb1 group compared with HF group. Furthermore, Rb1 was also found to modulate serum levels of PYY and NPY, and mRNA expression of NPY, Y2 receptor and PYY in tissue samples of DIO mice. Taken together, ginsenoside Rb1 may be useful in the treatment of obesity via modifying the serum content and mRNA expression of NPY, Y2 receptor and PYY.

Inhibiting neuropeptide Y Y1 receptor modulates melanocortin receptor- and NF-κB-mediated feeding behavior in phenylpropanolamine-treated rats.

Neuropeptide Y (NPY) and nuclear factor-kappa B (NF-κB) are involved in regulating anorexia elicited by phenylpropanolamine (PPA), a sympathomimetic drug. This study explored whether NPY Y1 receptor (Y1R) is involved in this process, and a potential role for the proopiomelanocortin system was identified. Rats were given PPA once a day for 4days. Changes in the hypothalamic expression of the NPY, Y1R, NF-κB, and melanocortin receptor 4 (MC4R) levels were assessed and compared. The results indicated that food intake and NPY expression decreased, with the largest reductions observed on Day 2 (approximately 50% and 45%, respectively), whereas NF-κB, MC4R, and Y1R increased, achieving maximums on Day 2 (160%, 200%, and 280%, respectively). To determine the role of Y1R, rats were pretreated with Y1R antisense or a Y1R antagonist via intracerebroventricular injection 1h before the daily PPA dose. Y1R knockdown and inhibition reduced PPA anorexia and partially restored the normal expression of NPY, MC4R, and NF-κB. The data suggest that hypothalamic Y1R participates in the appetite-suppression from PPA by regulating MC4R and NF-κB. The results of this study increase our understanding of the molecular mechanisms in PPA-induced anorexia.

The identification of neuropeptide Y receptor subtype involved in phenylpropanolamine-induced increase in oxidative stress and appetite suppression.

Hypothalamic neuropeptide Y (NPY) and superoxide dismutase (SOD) have been reported to participate in the regulation of appetite-suppressing effect of phenylpropanolamine (PPA), a sympathomimetic agent. This study explored whether Y1 receptor (Y1R) and/or Y5 receptor (Y5R) was involved in this regulation. Wistar rats were treated with PPA for 24 h. Changes in food intake and hypothalamic NPY, Y1R, Y5R, and SOD contents were assessed and compared. Results showed that food intake and NPY contents were decreased following PPA treatment, while Y1R and SOD contents were increased and Y5R contents remained unchanged. Moreover, although Y1R or Y5R knockdown by themselves could modify the food intake, Y1R but not Y5R knockdown could modify PPA-induced anorexia as well as NPY and SOD contents. In addition, selective inhibition of Y1R but not Y5R could modulate PPA-induced anorexia. It is suggested that Y1R but not Y5R participates in the anorectic response of PPA via the modulation of NPY and SOD. Results provide molecular mechanism of NPY-mediated PPA anorexia and may aid the understanding of the toxicology of PPA.

Neuropeptide Y stimulates food intake in the Zebrafish, Danio rerio.

Neuropeptide Y (NPY) is a potent orexigenic neuropeptide implicated in feeding regulation in mammals. However, except for the case of the goldfish, the involvement of NPY in the feeding behaviour of teleost fish has not well been studied. Therefore, we investigated the role of NPY in food intake using a zebrafish (Danio rerio) model because the molecular bases of NPY and its receptor have been well studied in this species. We examined the effect of feeding status on NPY-like immunoreactivity and the expression level of the NPY transcript in the brain. The number of neuronal cells showing NPY-like immunoreactivity in the hypothalamic regions, including the periventricular nucleus of posterior tuberculum and the posterior tuberal nucleus, was significantly increased in fish fasted for 7 days. NPY mRNA levels in the hypothalamus, but not the telencephalon, obtained from fish fasted for 7 days were higher than those in fish that had been fed normally. We then investigated the effect of i.c.v. administration of NPY on food intake. Cumulative food intake was significantly increased by i.c.v. administration of NPY (at 1 and 10 pmol/g body weight; BW) during a 60-min observation period. The NPY-induced orexigenic action (at 10 pmol/g BW) was blocked by treatment with a NPY Y1 receptor antagonist, BIBP-3226, at 100 pmol/g BW. These results indicate that NPY acts as an orexigenic factor in the zebrafish.

Effects of estrous cycle and sex on the expression of neuropeptide Y Y1 receptor in discrete hypothalamic and limbic nuclei of transgenic mice.

In the present study we used a transgenic mouse model, carrying the neuropeptide Y (NPY) Y1 receptor gene promoter linked to the LacZ reporter gene (Y1R/LacZ mice) to test the hypothesis of its up-regulation by gonadal hormones. Y1 receptor gene expression was detected by means of histochemical procedures and quantitative image analysis in the paraventricular nucleus, arcuate nucleus, medial preoptic nucleus, ventromedial nucleus and bed nucleus of stria terminalis of two-month-old female mice at different stages of estrous cycle. Qualitative and quantitative analyses showed that Y1R/LacZ transgene expression was higher in the paraventricular, arcuate, and ventromedial nuclei of proestrus mice as compared to mice in the other stages of the estrous cycle. In addition, we performed a comparison with a group of sexually active males. In this comparison a significant difference (less in males) was observed between males and proestrus females in the same nuclei. In conclusion, these data indicate that fluctuations in circulating levels of gonadal hormones, depending by estrous cycle, are paralleled by changes in the expression of NPY Y1 receptor in the hypothalamic nuclei involved in the control of both energy balance and reproduction.