Food intake is regulated by the hypothalamus, including the melanocortin and neuropeptide Y (NPY) systems in the arcuate nucleus. The NPY Y2 receptor (Y2R), a putative inhibitory presynaptic receptor, is highly expressed on NPY neurons in the arcuate nucleus, which is accessible to peripheral hormones. Peptide YY3-36 (PYY3-36), a Y2R agonist, is released from the gastrointestinal tract postprandially in proportion to the calorie content of a meal. Here we show that peripheral injection of PYY3-36 in rats inhibits food intake and reduces weight gain. PYY3-36 also inhibits food intake in mice but not in Y2r-null mice, which suggests that the anorectic effect requires the Y2R. Peripheral administration of PYY3-36 increases c-Fos immunoreactivity in the arcuate nucleus and decreases hypothalamic Npy messenger RNA. Intra-arcuate injection of PYY3-36 inhibits food intake. PYY3-36 also inhibits electrical activity of NPY nerve terminals, thus activating adjacent pro-opiomelanocortin (POMC) neurons. In humans, infusion of normal postprandial concentrations of PYY3-36 significantly decreases appetite and reduces food intake by 33% over 24 h. Thus, postprandial elevation of PYY3-36 may act through the arcuate nucleus Y2R to inhibit feeding in a gut–hypothalamic pathway.

BRIEF COMMUNICATION ARISING: Gut hormone PYY3-36 physiologically inhibits food intake

Food intake and energy expenditure are regulated by peripheral signals providing feedback on nutrient status and adiposity to the central nervous system. One of these signals is the pancreatic hormone, insulin. Unlike peripheral administration of insulin, which often causes weight gain, central administration of insulin leads to a reduction in food intake and body weight when administered long-term. This is a result of feedback processes in regions of the brain that regulate food intake. Within the hypothalamus, the arcuate nucleus (ARC) contains subpopulations of neurones that produce orexinergic neuropeptides agouti-related peptide (AgRP)/neuropeptide Y (NPY) and anorexigenic neuropeptides, pro-opiomelanocortin (POMC)/cocaine- and amphetamine-regulated transcript (CART). Intracerebroventricular infusion of insulin down-regulates the expression of AgRP/NPY at the same time as up-regulating expression of POMC/CART. Recent evidence suggests that insulin activity within the amygdala may play an important role in regulating energy balance. Insulin infusion into the central nucleus of the amygdala (CeA) can decrease food intake, possibly by modulating activity of NPY and other neurone subpopulations. Insulin signalling within the CeA can also influence stress-induced obesity. Overall, it is evident that the CeA is a critical target for insulin signalling and the regulation of energy balance.

The regulation of food intake by insulin in the central nervous system.

Hypothalamus is the most critical center in the brain for regulation of food intake. Hypothalamus performs this function through special nuclei. The most important of these nuclei is PVN, because in addition to receiving input from special hypothalamic nuclei, it also receives input from other regions of the brain, as well circulation. Inputs received from other areas of the brain via special receptors including: MCR, GABA, IR, LepR, CBR, OXR, HR, NPY, D, CRF, and GHSR. Due to the presence of several receptors on VMH, different neurotransmitters and neuromodulators related to central food intake regulation effect on this nucleus. These neurotransmitters include two categories: orexigenic and anorexigenic. Orexigenic neuropeptides such as: NPY, orexin, endocannabinoids, glutamate, urocortin, and ghrelin. Anorexigenic neuropeptides included: MSH, CRF, leptin, insulin, BDNF, histamine, and dopamine. Then, VMH integrates these inputs from the bind of these neurotransmitters to their receptors, and sends the final feedback to other brain regions. The VMH is the first satiety center in the brain, and it receives various inputs from different regions of the brain and circulation via multiple receptors, as well as integrating these inputs and sending the appropriate output to other areas of the brain, VMH plays an important role in central control of food intake. Therefore, throughout this review article would discuss the function of this nucleus on central regulation of food intake via various neuropeptides and receptors. 
Legend: ARC: Arcuate nucleus. PVN: Paraventricular nucleus. VMH: Ventromedial hypothalamus. SF1: Serotonergic factor 1. BDNF: Brain-derived neurotropic factor. POMC: pro-opiomelanocortin. AgRP/NPY: Agouti related protein/ Neuropeptide Y. VTA: Ventral tegmental area. CB: Endocannabinoidergic neuron. OX: Orexin neuron. TB: Tuberommillary nucleus. H: Histaminergic neuron. D: Dopaminergic neuron. G: Glutamatergic neuron.: Stimulatory projection.: Inhibitory projection.

The Role of Ventromedial Hypothalamus Receptors in the Central Regulation of Food Intake

Appetite is controlled by a complex system of central and peripheral signals interacting to modulate the ingestion response. Several brain mediators with complex networks adjust food intake in birds. Based on the available literature, these mediators have interactions with a number of other neurotransmitters (NTS) involved in feed intake. It means that, NTS regulate feeding behavior through mediating other peptide and NTs activity. In birds, insulin known as a hypophagic hormone that is interplaying with neuropeptide Y (NPY), pro-opiomelanocortin (POMC), and corticotropin-releasing factor (CRF) in brain. Another hormone ghrelin, inhibits food intake in birds and other mediators, such as glutamate, endocannabinoid system (ECS), serotonin (5-hydroxytryptamine, 5-HT), and norepinephrine (NE), which play a key role in ghrelin-induced hypophagia. Another involved peptide on feeding behavior in chickens called nociceptin/orphanin FQ (N/OFQ) is modulated by histamine, glutamate, dopamine (DA), gamma-aminobutyric acid (GABA), agouti-related protein (AgRP), and cocaine and amphetamine-regulated transcript (CART). Some of the NTS such as opioid have both orexigenic and anorexigenic effects in birds while has interaction with NE, glutamate, histamine, DA, and cannabinoids (CBs). Thus, interaction among mediators is a prominent process needs to be considered in order to understanding the mechanisms underlying feed intake regulation in birds. This review aims to investigate the role of major regulators and their mediatory interactions with one another in poultry feeding behavior. According to mentioned interactions, it seems that dopamine, serotonin, and glutamate have the most interactions with other NT systems. Therefore, they play an axial role in the central regulation of food intake in CNS.

The Crosstalk Between Brain Mediators Regulating Food Intake Behavior in Birds: A Review

Response of the thyroid axis and appetite-regulating peptides to fasting and overfeeding in goldfish (Carassius auratus)

1. The present study was conducted to investigate whether brain somatostatin increases feed intake in neonatal chickens. The mediating role of neuropeptide Y receptors on feed intake induced by som...

Interaction of neuropeptide Y receptors (NPY1, NPY2 and NPY5) with somatostatin on somatostatin-induced feeding behaviour in neonatal chicken

Some neuropeptides such as neuropeptide Y (NPY) maintain energy balance. The aim of this study was to investigate the role of insulin on feed intake and their interaction with NPY receptors (NPY1, NPY2, and NPY5) in newly hatched chickens (5-day-old chickens). This study was performed in 7 experiments (in each experiment, 4 groups with 6 replications). In the first 4 experiments were used to investigate the doses of insulin (2.5, 5 and 10 ng), NPY1, NPY2, and NPY5 receptors antagonist (1.25, 2.5 and 5 μg) on feed intake via intraventricular injection were evaluated, as well as effective and sub-effective doses were determined. After that, the interactions of these compounds with insulin were investigated in 3 experiments. In experiments 5, 6 and 7, chickens received, NPY1, NPY2, and NPY5 receptors antagonist, prior to injection of insulin, respectively; then the chicken was injected with insulin to study the feed intake. In each experiment, the control group received a control solution. Then, in each experiment cumulative feed intake were measured up to 120 min after injection. NPY2 receptor antagonist, resulted in increased feed intake (p   0.05). It is concluded that, insulin has a decreasing effect on newly hatched chicken’s feed intake via NPY1 and NPY2 receptors.

Survey the Effect of Insulin on Modulating Feed Intake Via NPY Receptors in 5-Day-Old Chickens

Food consumption and body weight regulations are done in the hypothalamus. Indeed, hypothalamus is the brain’s main area in controlling food intake. Hypothalamus controls food intake via special nuclei such as: ARC, PVN, DMH, VMH and LHA. PVN are second order neurons. This nucleus received multiple inputs from different areas of the brain via specific and non-specific receptors. NPYR and α2-adrenoceptors are orexigenic receptors, but Melanocortin receptors are anorexigenic receptors. PVN integrated inputs from multiple areas, and then transmitted various outputs for central regulation of food intake. To identify neural pathways and the role of neurotransmitters on central control of food intake in PVN, multiple researches have been done via injection of various neurotransmitters on the laboratory animals. Leptin applies its effect on regulation of feeding behaviours through arcuate nucleus-paraventricular nucleus axis and MC4R receptor. Also, Insulin is a hypophagic neurotransmitter, and its hypophagic effect applied in PVN via NPY1 and MC4R receptors. Ghrelin has a biphasic effect on food intake in birds and mammals. In birds, ghrelin inhibits food intake, but in mammals stimulated food intake. In birds, ghrelin via 5HT2A receptor on CRF neurons located on PVN reduced food intake. In mammals via GHSR (ghrelin receptor) and NPY1 receptors increased food intake. Somatostatin acts in the brain as an inhibitory and hyperphagic neurotransmitter. Hyperphagic effect of Somatostatin on PVN exert via SST2, OX1 and NPY1 receptors respectively. Therefore, PVN has an important effect on central regulation of food intake via different neurotransmitters and pathway. The role of PVN in central regulation of food intake. ARC arcuate nucleus, PVN paraventricular nucleus, LHA lateral hypothalamus area, CRF Corticotropin-realising factor, POMC pro-opiomelanocortin, CART Cocaine and amphetamine-regulated transcript, NPY/AgRP neuropeptide Y/agouti-related protein, Y1R NPY1 receptor, GHSR growth hormone secretagogues receptor, LEPR Leptin receptor, INSR Insulin receptor, OX1R orexin receptor, MC4R Melanocortin4 receptor, SST2R Somatostatin2 receptor.

Role of Paraventricular Nucleus in Regulation of Feeding Behaviour and the Design of Intranuclear Neuronal Pathway Communications

Neuropeptide Y (NPY) plays a mediatory role in cerebral insulin function by maintaining energy balance. The current study was designed to determine the role of insulin in food intake and its intera...

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Shiba Yousefvand

Papers

Interaction of neuropeptide Y receptors (NPY1, NPY2 and NPY5) with somatostatin on somatostatin-induced feeding behaviour in neonatal chicken

The Role of Ventromedial Hypothalamus Receptors in the Central Regulation of Food Intake

Survey the Effect of Insulin on Modulating Feed Intake Via NPY Receptors in 5-Day-Old Chickens

Role of Paraventricular Nucleus in Regulation of Feeding Behaviour and the Design of Intranuclear Neuronal Pathway Communications

Hypophagic effects of insulin are mediated via NPY1/NPY2 receptors in broiler cockerels