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BACKGROUND: Neuropeptide Y (NPY) Y2 receptor (Y2) antagonist BIIE0246 can both inhibit and facilitate nociception. We hypothesized that Y2 function depends on inflammation or nerve injury status. METHODS: We implemented a battery of behavioral tests in mice of both sexes that received: 1) no injury; 2) an incision model of postoperative pain; 3) a spared nerve injury (SNI) model of neuropathic pain; and 4) a latent sensitization model of chronic postsurgical pain. In addition to Y2 gene expression assays, spinal Y2 G-protein coupling was studied with [ 35S]GTPγS binding assays. RESULTS: We report that intrathecal BIIE0246 increased mechanical and cold hypersensitivity, produced behavioral signs of spontaneous nociception and itch, and produced conditioned place aversion and preference in normal, uninjured mice. BIIE0246 did not change heat hypersensitivity or motor coordination. Conditional (sensory neuron-specific) Y2 deletion prevented BIIE0246-induced mechanical and cold hypersensitivity, nocifensive behaviors and aversion. Both conditional deletion and pharmacological blockade of Y2 reduced mechanical and thermal hypersensitivity after incision or nerve injury. SNI did not change the sensitivity of Y2 G-protein coupling with the Y2 agonist PYY3-36, but increased the population of Y2 that effectively coupled G-proteins. Intrathecal PYY3-36 failed to reduce SNI- or incision-induced hypersensitivity in C57BL/6N mice. Incision did not change Npy2r gene expression in dorsal root ganglion. CONCLUSIONS: We conclude that Y2 at central terminals of primary afferent neurons provide tonic inhibition of mechanical and cold nociception and itch. This switches to the promotion of mechanical and thermal hyperalgesia in models of acute and chronic postsurgical and neuropathic pain, perhaps due to an increase in the population of Y2 that effectively couple to G-proteins. These results support the development of Y2 antagonists for the treatment of chronic postsurgical and neuropathic pain.
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Neuropeptide Y (NPY) plays a crucial role in controlling energy homeostasis and feeding behaviour. The role of NPY neurons located in the arcuate nucleus of the hypothalamus (Arc) in responding to homeostatic signals has been the focus of much investigation, but most studies have used AgRP promoter-driven models, which do not fully encompass Arc NPY neurons. To directly investigate NPY-expressing versus AgRP-expressing Arc neurons function, we utilised chemogenetic techniques in NPY-Cre and AgRP-Cre animals to activate Arc NPY or AgRP neurons in the presence of food and food-related stimuli. Our findings suggest that chemogenetic activation of the broader population of Arc NPY neurons, including AgRP-positive and AgRP-negative NPY neurons, has equivalent effects on feeding behaviour as activation of Arc AgRP neurons. Our results demonstrate that these Arc NPY neurons respond specifically to caloric signals and do not respond to non-caloric signals, in line with what has been observed in AgRP neurons. Activating Arc NPY neurons significantly increases food consumption and influences macronutrient selection to prefer fat intake.
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The control of feeding and physical activity is tightly linked and coordinated. However the underlying mechanisms are unclear. One of the major regulatory systems of feeding behaviour involves neuropeptide Y (NPY) signalling, with the signalling mediated through NPY Y4 receptor also known to influence activity. Here we show that mice globally lacking the Npy4r (Npy4r-/-) in the absence of access to a running wheel behaved WT-like with regards to food intake, energy expenditure, respiratory exchange ratio and locomotion regardless of being fed on a chow or high fat diet. Interestingly however, when given the access to a running wheel, Npy4r-/- mice while having a comparable locomotor activity, showed significantly higher wheel-running activity than WT, again regardless of dietary conditions. This higher wheel-running activity in Npy4r-/-mice arose from an increased dark-phase running time rather than changes in number of running bouts or the running speed. Consistently, energy expenditure was higher in Npy4r-/- than WT mice. Importantly, food intake was reduced in Npy4r-/-mice under wheel access condition which was due to decreased feeding bouts rather than changes in meal size. Together, these findings demonstrate an important role of Npy4r signalling in the dual control of feeding and physical activity, particularly in the form of wheel-running activity.
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Ingestão de Alimentos , Metabolismo Energético , Comportamento Alimentar , Camundongos Knockout , Neuropeptídeo Y , Receptores de Neuropeptídeo Y , Transdução de Sinais , Animais , Camundongos , Dieta Hiperlipídica , Ingestão de Alimentos/fisiologia , Metabolismo Energético/fisiologia , Comportamento Alimentar/fisiologia , Locomoção/fisiologia , Camundongos Endogâmicos C57BL , Atividade Motora/fisiologia , Neuropeptídeo Y/metabolismo , Condicionamento Físico Animal/fisiologia , Receptores de Neuropeptídeo Y/metabolismo , Receptores de Neuropeptídeo Y/genética , Transdução de Sinais/fisiologiaRESUMO
Peptide YY (PYY3-36) is a post-prandially released gut hormone with potent appetite-reducing activity, the mechanism of action of which is not fully understood. Unravelling how this system physiologically regulates food intake may help unlock its therapeutic potential, whilst minimising unwanted effects. Here we demonstrate that germline and post-natal targeted knockdown of the PYY3-36 preferring receptor (neuropeptide Y (NPY) Y2 receptor (Y2R)) in the afferent vagus nerve is required for the appetite inhibitory effects of physiologically-released PYY3-36, but not peripherally administered pharmacological doses. Post-natal knockdown of the Y2R results in a transient body weight phenotype that is not evident in the germline model. Loss of vagal Y2R signalling also results in altered meal patterning associated with accelerated gastric emptying. These results are important for the design of PYY-based anti-obesity agents.
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Hormônios Gastrointestinais , Peptídeo YY , Peptídeo YY/fisiologia , Apetite/fisiologia , Nervo Vago , Ingestão de AlimentosRESUMO
OBJECTIVE: One of leptin's main targets in the hypothalamus are neuropeptide Y (NPY) neurons, with selective deletion of leptin receptors (Lepr) specifically in Npy neurons resulting in major alterations of energy partitioning between fat and bone mass. However, the specific action of these Npy+/Lepr+ neurons compared to Npy-negative Lepr (Npy-/Lepr+) neurons in regard to energy homeostasis regulation is unknown. METHODS: Specific AAV viral vectors were generated using DREADD and INTRSECT technology and used in male LeprCre/+ and LeprCre/+;NpyFlp/+ mice to assess the effect of activating either all Lepr neurons or specifically Npy+/Lepr+ or Npy-/Lepr+ neurons only on feeding, energy homeostasis control, and body composition. RESULTS: Selective stimulation of Npy+/Lepr+ neurons led to an immediate decrease in respiratory quotient followed by a delayed increase in food intake in standard chow fed, but interestingly not in high fat diet (HFD) fed mice. In addition, stimulation of Npy+/Lepr+ neurons led to a robust increase in brown adipose tissue thermogenesis and improved glucose tolerance. These effects were not observed in standard chow fed mice when Npy-/Lepr+ expressing neurons were specifically activated, suggesting the effects of leptin on these parameters are driven by NPY. However, under HFD condition when leptin levels are elevated, the stimulation of the Npy-/Lepr+ neurons increased food intake, physical activity and energy expenditure. Interestingly, chronic stimulation of Npy-positive Lepr neurons was able to increase bone mass independently of bodyweight, whilst chronic stimulation of the Npy-/Lepr+ neurons resulted in increased bodyweight and fat mass with proportionate increases in bone mass. CONCLUSIONS: Together, these data indicate that leptin signalling through Npy-positive Lepr-expressing neurons controls energy partitioning via stimulation of thermogenesis, energy expenditure, and the use of fat as a fuel source. However, under prolonged HFD, leptin resistance may occur and actions of leptin signalling through Npy-negative Lepr hypothalamic neurons may exacerbate excess food intake.
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Leptina , Neuropeptídeo Y , Camundongos , Masculino , Animais , Leptina/metabolismo , Neuropeptídeo Y/metabolismo , Receptores para Leptina/genética , Receptores para Leptina/metabolismo , Neurônios/metabolismo , Metabolismo EnergéticoRESUMO
The mammalian gut secretes a family of multifunctional peptides that affect appetite, intestinal secretions, and motility whereas others regulate the microbiota. We have found that peptide YY (PYY1-36), but not endocrine PYY3-36, acts as an antimicrobial peptide (AMP) expressed by gut epithelial paneth cells (PC). PC-PYY is packaged into secretory granules and is secreted into and retained by surface mucus, which optimizes PC-PYY activity. Although PC-PYY shows some antibacterial activity, it displays selective antifungal activity against virulent Candida albicans hyphae-but not the yeast form. PC-PYY is a cationic molecule that interacts with the anionic surfaces of fungal hyphae to cause membrane disruption and transcriptional reprogramming that selects for the yeast phenotype. Hence, PC-PYY is an antifungal AMP that contributes to the maintenance of gut fungal commensalism.
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Antifúngicos , Peptídeos Antimicrobianos , Candida , Celulas de Paneth , Fragmentos de Peptídeos , Peptídeo YY , Animais , Antifúngicos/metabolismo , Peptídeos Antimicrobianos/metabolismo , Candida/efeitos dos fármacos , Candida/fisiologia , Celulas de Paneth/metabolismo , Fragmentos de Peptídeos/metabolismo , Peptídeo YY/metabolismo , Simbiose , Humanos , CamundongosRESUMO
Chronic stress fuels the consumption of palatable food and can enhance obesity development. While stress- and feeding-controlling pathways have been identified, how stress-induced feeding is orchestrated remains unknown. Here, we identify lateral habenula (LHb) Npy1r-expressing neurons as the critical node for promoting hedonic feeding under stress, since lack of Npy1r in these neurons alleviates the obesifying effects caused by combined stress and high fat feeding (HFDS) in mice. Mechanistically, this is due to a circuit originating from central amygdala NPY neurons, with the upregulation of NPY induced by HFDS initiating a dual inhibitory effect via Npy1r signaling onto LHb and lateral hypothalamus neurons, thereby reducing the homeostatic satiety effect through action on the downstream ventral tegmental area. Together, these results identify LHb-Npy1r neurons as a critical node to adapt the response to chronic stress by driving palatable food intake in an attempt to overcome the negative valence of stress.
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Habenula , Camundongos , Animais , Vias Neurais/fisiologia , Habenula/fisiologia , Região Hipotalâmica Lateral , Área Tegmentar Ventral , Neurônios/fisiologiaRESUMO
Neuropeptide Y (NPY) in the arcuate nucleus (ARC) is known as one of the most critical regulators of feeding. However, how NPY promotes feeding under obese conditions is unclear. Here, we show that positive energy balance, induced by high-fat diet (HFD) or in genetically obese leptin-receptor-deficient mice, leads to elevated Npy2r expression especially on proopiomelanocortin (POMC) neurons, which also alters leptin responsiveness. Circuit mapping identified a subset of ARC agouti-related peptide (Agrp)-negative NPY neurons that control these Npy2r expressing POMC neurons. Chemogenetic activation of this newly discovered circuitry strongly drives feeding, while optogenetic inhibition reduces feeding. Consistent with that, lack of Npy2r on POMC neurons leads to reduced food intake and fat mass. This suggests that under energy surplus conditions, when ARC NPY levels generally drop, high-affinity NPY2R on POMC neurons is still able to drive food intake and enhance obesity development via NPY released predominantly from Agrp-negative NPY neurons.
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Leptina , Pró-Opiomelanocortina , Camundongos , Animais , Leptina/metabolismo , Pró-Opiomelanocortina/metabolismo , Neuropeptídeo Y/metabolismo , Proteína Relacionada com Agouti/metabolismo , Neurônios/metabolismo , Núcleo Arqueado do Hipotálamo , Obesidade/metabolismoRESUMO
The cell bodies of postganglionic sympathetic neurons innervating the heart primarily reside in the stellate ganglion (SG), alongside neurons innervating other organs and tissues. Whether cardiac-innervating stellate ganglionic neurons (SGNs) exhibit diversity and distinction from those innervating other tissues is not known. To identify and resolve the transcriptomic profiles of SGNs innervating the heart, we leveraged retrograde tracing techniques using adeno-associated virus (AAV) expressing fluorescent proteins (GFP or Td-tomato) with single cell RNA sequencing. We investigated electrophysiologic, morphologic, and physiologic roles for subsets of cardiac-specific neurons and found that three of five adrenergic SGN subtypes innervate the heart. These three subtypes stratify into two subpopulations; high (NA1a) and low (NA1b and NA1c) neuropeptide-Y (NPY) -expressing cells, exhibit distinct morphological, neurochemical, and electrophysiologic characteristics. In physiologic studies in transgenic mouse models modulating NPY signaling, we identified differential control of cardiac responses by these two subpopulations to high and low stress states. These findings provide novel insights into the unique properties of neurons responsible for cardiac sympathetic regulation, with implications for novel strategies to target specific neuronal subtypes for sympathetic blockade in cardiac disease.
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Neurônios , Gânglio Estrelado , Camundongos , Animais , Neurônios/metabolismo , Gânglio Estrelado/metabolismo , Coração , Neuropeptídeo Y/metabolismo , Perfilação da Expressão GênicaRESUMO
Aberrant AKT activation occurs in a number of cancers, metabolic syndrome, and immune disorders, making it an important target for the treatment of many diseases. To monitor spatial and temporal AKT activity in a live setting, we generated an Akt-FRET biosensor mouse that allows longitudinal assessment of AKT activity using intravital imaging in conjunction with image stabilization and optical window technology. We demonstrate the sensitivity of the Akt-FRET biosensor mouse using various cancer models and verify its suitability to monitor response to drug targeting in spheroid and organotypic models. We also show that the dynamics of AKT activation can be monitored in real time in diverse tissues, including in individual islets of the pancreas, in the brown and white adipose tissue, and in the skeletal muscle. Thus, the Akt-FRET biosensor mouse provides an important tool to study AKT dynamics in live tissue contexts and has broad preclinical applications.
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Técnicas Biossensoriais , Proteínas Proto-Oncogênicas c-akt , Camundongos , Animais , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transferência Ressonante de Energia de Fluorescência/métodos , Técnicas Biossensoriais/métodosRESUMO
The nucleus accumbens shell is a critical node in reward circuitry, encoding environments associated with reward. Long-range inputs from the ventral hippocampus (ventral subiculum) to the nucleus accumbens shell have been identified, yet their precise molecular phenotype remains to be determined. Here we used retrograde tracing to identify the ventral subiculum as the brain region with the densest glutamatergic (VGluT1-Slc17a7) input to the shell. We then used circuit-directed translating ribosome affinity purification to examine the molecular characteristics of distinct glutamatergic (VGluT1, VGluT2-Slc17a6) ventral subiculum to nucleus accumbens shell projections. We immunoprecipitated translating ribosomes from this population of projection neurons and analysed molecular connectomic information using RNA sequencing. We found differential gene enrichment across both glutamatergic projection neuron subtypes. In VGluT1 projections, we found enrichment of Pfkl, a gene involved in glucose metabolism. In VGluT2 projections, we found a depletion of Sparcl1 and Dlg1, genes known to play a role in depression- and addiction-related behaviours. These findings highlight potential glutamatergic neuronal-projection-specific differences in ventral subiculum to nucleus accumbens shell projections. Together these data advance our understanding of the phenotype of a defined brain circuit.
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Hipocampo , Núcleo Accumbens , Encéfalo , Hipocampo/metabolismo , Núcleo Accumbens/metabolismo , Recompensa , Animais , CamundongosRESUMO
The cell bodies of postganglionic sympathetic neurons innervating the heart primarily reside in the stellate ganglion (SG), alongside neurons innervating other organs and tissues. Whether cardiac-innervating stellate ganglionic neurons (SGNs) exhibit diversity and distinction from those innervating other tissues is not known. To identify and resolve the transcriptomic profiles of SGNs innervating the heart we leveraged retrograde tracing techniques using adeno-associated virus (AAV) expressing fluorescent proteins (GFP or Td-tomato) with single cell RNA sequencing. We investigated electrophysiologic, morphologic, and physiologic roles for subsets of cardiac-specific neurons and found that three of five adrenergic SGN subtypes innervate the heart. These three subtypes stratify into two subpopulations; high (NA1a) and low (NA1b and NA1c) Npy-expressing cells, exhibit distinct morphological, neurochemical, and electrophysiologic characteristics. In physiologic studies in transgenic mouse models modulating NPY signaling, we identified differential control of cardiac responses by these two subpopulations to high and low stress states. These findings provide novel insights into the unique properties of neurons responsible for cardiac sympathetic regulation, with implications for novel strategies to target specific neuronal subtypes for sympathetic blockade in cardiac disease.
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Thermogenesis is a centrally regulated physiological process integral for thermoregulation and energy homeostasis. However, the mechanisms and pathways involved remain poorly understood. Importantly, in this study we uncovered that in an environment of 28 °C that is within the mouse thermoneutral zone, lack of NPFF signalling leads to significant increases in energy expenditure, resting metabolic rate and brown adipose tissue (BAT) thermogenesis, which is associated with decreased body weight gain and lean tissue mass. Interestingly, when exposed to a high-fat diet (HFD) at 28 °C, Npff-/- mice lost the high energy expenditure phenotype observed under chow condition and exhibited an impaired diet-induced thermogenesis. On the other hand, under conditions of increasing levels of thermal demands, Npff-/- mice exhibited an elevated BAT thermogenesis at mild cold condition (22 °C), but initiated comparable BAT thermogenic responses as WT mice when thermal demand increased, such as an exposure to 4 °C. Together, these results reveal NPFF signalling as a novel and critical player in the control of thermogenesis, where it regulates thermosensory thermogenesis at warm condition and adjusts thermoregulation under positive energy balance to regulate diet-induced thermogenesis.
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Tecido Adiposo Marrom , Receptores de Neuropeptídeos , Termogênese , Animais , Camundongos , Tecido Adiposo Marrom/metabolismo , Dieta Hiperlipídica , Metabolismo Energético , Termogênese/fisiologia , Camundongos KnockoutRESUMO
BACKGROUND/OBJECTIVE: Female mice are often excluded from diet-induced obesity studies as they are more resistant to the obesifying effects of a high-fat diet (HFD). However, the underlying mechanisms behind this sex disparity may actually have important implications for the development and management of obesity in humans. Therefore, we systematically investigated the immediate sex-specific effects of transitioning to a HFD in C57BL/6J mice as well as monitored whether these effects are altered after sustained HFD feeding and whether sex affects the response to a return to chow, representative of dieting. METHODS: Dual X-ray absorptiometry (DXA) analysis of body composition, indirect calorimetry measurements, and qPCR analysis of hypothalamic and brainstem regions were performed on male and female C57BL/6J mice. RESULTS: HFD had immediate and dramatic effects in males, increasing fat mass by 58% in the first 3 days. The resistance to the obesifying effect of HFD in females was linked both to an ability to maintain activity levels as well as to an immediate and significantly enhanced reduction in respiratory quotient (RQ), suggesting a greater ability to utilise fat in the diet as a source of fuel. Mechanistically, this sex disparity may be at least partially due to inherent sex differences in the catabolic (POMC/CART) versus anabolic (NPY/AgRP) neurological signalling pathways. Interestingly, the reintroduction of chow following HFD had immediate and consistent responses between the sexes with body composition and most metabolic parameters normalised within 3 days. However, both sexes displayed elevated hypothalamic Npy levels reminiscent of starvation. The difference in RQ seen between the sexes on HFD was immediately abolished suggesting similar abilities to burn fat reserves for fuel. CONCLUSIONS: C57BL/6J mice have markedly different sex-specific behavioural and metabolic responses to the introduction as well as the sustained intake of a HFD, but consistent responses to a dieting situation.
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Dieta Hiperlipídica , Gorduras na Dieta , Obesidade , Proteína Relacionada com Agouti/metabolismo , Animais , Dieta Hiperlipídica/efeitos adversos , Gorduras na Dieta/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Obesidade/etiologia , Obesidade/metabolismo , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , Fatores SexuaisRESUMO
OBJECTIVE: Neuropeptide FF (NPFF) group peptides belong to the evolutionary conserved RF-amide peptide family. While they have been assigned a role as pain modulators, their roles in other aspects of physiology have received much less attention. NPFF peptides and their receptor NPFFR2 have strong and localized expression within the dorsal vagal complex that has emerged as the key centre for regulating glucose homeostasis. Therefore, we investigated the role of the NPFF system in the control of glucose metabolism and the histochemical and molecular identities of NPFF and NPFFR2 neurons. METHODS: We examined glucose metabolism in Npff-/- and wild type (WT) mice using intraperitoneal (i.p.) glucose tolerance and insulin tolerance tests. Body composition and glucose tolerance was further examined in mice after 1-week and 3-week of high-fat diet (HFD). Using RNAScope double ISH, we investigated the neurochemical identity of NPFF and NPFFR2 neurons in the caudal brainstem, and the expression of receptors for peripheral factors in NPFF neurons. RESULTS: Lack of NPFF signalling in mice leads to improved glucose tolerance without significant impact on insulin excursion after the i.p. glucose challenge. In response to an i.p. bolus of insulin, Npff-/- mice have lower glucose excursions than WT mice, indicating an enhanced insulin action. Moreover, while HFD has rapid and potent detrimental effects on glucose tolerance, this diet-induced glucose intolerance is ameliorated in mice lacking NPFF signalling. This occurs in the absence of any significant impact of NPFF deletion on lean or fat masses, suggesting a direct effect of NPFF signalling on glucose metabolism. We further reveal that NPFF neurons in the subpostrema area (SubP) co-express receptors for peripheral factors involved in glucose homeostasis regulation such as insulin and GLP1. Furthermore, Npffr2 is expressed in the glutamatergic NPFF neurons in the SubP, and in cholinergic neurons of the dorsal motor nucleus of the vagus (DMV), indicating that central NPFF signalling is likely modulating vagal output to innervated peripheral tissues including those important for glucose metabolic control. CONCLUSIONS: NPFF signalling plays an important role in the regulation of glucose metabolism. NPFF neurons in the SubP are likely to receive peripheral signals and mediate the control of whole-body glucose homeostasis via centrally vagal pathways. Targeting NPFF and NPFFR2 signalling may provide a new avenue for treating type 2 diabetes and obesity.
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Diabetes Mellitus Tipo 2 , Insulinas , Oligopeptídeos , Animais , Diabetes Mellitus Tipo 2/metabolismo , Glucose/metabolismo , Homeostase , Insulinas/metabolismo , Camundongos , Oligopeptídeos/metabolismoRESUMO
Obesogenic diets can produce hippocampal insulin resistance and impairments to hippocampal-dependent cognition. This study investigated the effect of disrupted insulin signaling in Neuropeptide Y (NPY) neurons on diet-induced deficits in hippocampal-dependent memory. Wild-type mice and mice that had a targeted knockout of insulin receptors on NPY cells (IRlox/lox;NPYCre/+) were given ad libitum access to a high-fat diet (high fat; HF), 10% sucrose solution (high sugar; HS), both high-fat diet and sucrose solution (high fat, high sugar; HFHS), or a normal fat control chow for 12 weeks. Mice were tested in the Morris Water Maze (MWM), a hippocampal-dependent spatial memory task. Glucose homeostasis was assessed via a glucose tolerance test. Independent of genotype, consumption of HF, but not HS, diet increased energy intake, body weight, and plasma leptin, and impaired glucose tolerance. Disrupted insulin signaling in NPY cells and dietary interventions did not significantly affect the ability of mice to learn the location of the platform in the MWM. However, for IRlox/lox control mice, consumption of HF, but not HS, diet resulted in reduced time spent in the target quadrant during the probe trial, suggesting a hippocampal-dependent memory deficit. IRlox/lox;NPYCre/+ mice had poor performance in the probe trial regardless of diet, suggesting a floor effect. This study did not find adverse effects of chronic sucrose intake on metabolic outcomes or hippocampal-dependent memory. These data also suggest that the effects of HF diet on hippocampal-dependent memory may be dependent on insulin signaling in hippocampal NPY cells.
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AIMS/HYPOTHESIS: Pancreatic beta cell dedifferentiation, transdifferentiation into other islet cells and apoptosis have been implicated in beta cell failure in type 2 diabetes, although the mechanisms are poorly defined. The endoplasmic reticulum stress response factor X-box binding protein 1 (XBP1) is a major regulator of the unfolded protein response. XBP1 expression is reduced in islets of people with type 2 diabetes, but its role in adult differentiated beta cells is unclear. Here, we assessed the effects of Xbp1 deletion in adult beta cells and tested whether XBP1-mediated unfolded protein response makes a necessary contribution to beta cell compensation in insulin resistance states. METHODS: Mice with inducible beta cell-specific Xbp1 deletion were studied under normal (chow diet) or metabolic stress (high-fat diet or obesity) conditions. Glucose tolerance, insulin secretion, islet gene expression, alpha cell mass, beta cell mass and apoptosis were assessed. Lineage tracing was used to determine beta cell fate. RESULTS: Deletion of Xbp1 in adult mouse beta cells led to beta cell dedifferentiation, beta-to-alpha cell transdifferentiation and increased alpha cell mass. Cell lineage-specific analyses revealed that Xbp1 deletion deactivated beta cell identity genes (insulin, Pdx1, Nkx6.1, Beta2, Foxo1) and derepressed beta cell dedifferentiation (Aldh1a3) and alpha cell (glucagon, Arx, Irx2) genes. Xbp1 deletion in beta cells of obese ob/ob or high-fat diet-fed mice triggered diabetes and worsened glucose intolerance by disrupting insulin secretory capacity. Furthermore, Xbp1 deletion increased beta cell apoptosis under metabolic stress conditions by attenuating the antioxidant response. CONCLUSIONS/INTERPRETATION: These findings indicate that XBP1 maintains beta cell identity, represses beta-to-alpha cell transdifferentiation and is required for beta cell compensation and prevention of diabetes in insulin resistance states.
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Diabetes Mellitus Tipo 2 , Resistência à Insulina , Células Secretoras de Insulina , Proteína 1 de Ligação a X-Box/metabolismo , Animais , Transdiferenciação Celular/genética , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Humanos , Insulina/metabolismo , Resistência à Insulina/genética , Células Secretoras de Insulina/metabolismo , Camundongos , Estresse Fisiológico , Proteína 1 de Ligação a X-Box/genéticaRESUMO
OBJECTIVE: Aguti-related protein (AGRP) neurons in the arcuate nucleus of the hypothalamus (ARC), which co-express neuropeptide Y (NPY), are key regulators of feeding and energy homeostasis. However, the precise role NPY has within these neurons and the specific pathways that it control are still unclear. In this article, we aimed to determine what aspects of feeding behaviour and energy homeostasis are controlled by NPY originating from AGRP neurons and which Y-receptor pathways are utilised to fulfil this function. METHODS: Novel conditional Agrpcre/+;Npylox/lox knockout mice were generated and comprehensively phenotyped, both under standard chow as well as high-fat-diet conditions. Designer receptor exclusively activated by designer drugs (DREADD) technology was used to assess the altered responses on feeding and energy homeostasis control in the absence of NPY in these neurons. Rescue experiments utilising Npy1r- and Npy2r-selective NPY ligands were performed to assess which component of the energy homeostasis control is dependent by which specific Y-receptor pathway. RESULTS: We show that the specific deletion of Npy only in AGRP neurons leads to a paradoxical mild obese phenotype associated with reduced locomotion and energy expenditure and increased feeding and Respiratory Quotient (RQ) that remain elevated under a positive energy balance. The activation of Npy-deficient AGRP neurons via DREADD's is still able to drive feeding, yet with a delayed onset. Additionally, Clozapine-N-oxide (CNO) treatment reduces locomotion without impacting on energy expenditure. Rescue experiments re-introducing Npy1r- and Npy2r-selective NPY ligands revealed that the increased feeding and RQ are mostly driven by Npy1r, whereas energy expenditure and locomotion are controlled by Npy2r signalling. CONCLUSION: Together, these results demonstrate that NPY originating from AGRP neurons is not only critical to initiate but also for continuously driving feeding, and we for the first time identify which Y-receptor controls which pathway.
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Metabolismo Energético , Neuropeptídeo Y , Proteína Relacionada com Agouti/genética , Proteína Relacionada com Agouti/metabolismo , Animais , Ligantes , Camundongos , Neurônios/metabolismo , Neuropeptídeo Y/metabolismoRESUMO
Insulin is known to act in the central nervous system to regulate several physiological and behavioural outcomes, including energy balance, glucose homeostasis and cognitive functioning. However, the neuronal populations through which insulin enhances cognitive performance remain unidentified. Insulin receptors are found in neuropeptide-Y (NPY) expressing neurons, which are abundant in the hypothalamus and hippocampus; regions involved in feeding behaviour and spatial memory, respectively. Here we show that mice with a tissue specific knockout of insulin receptors in NPY expressing neurons (IRlâ¢oâ¢x/lâ¢oâ¢x; NPYCâ¢râ¢eâ£/+) display an impaired performance in the probe trial of the Morris Water Maze compared with control mice at both the 6 and the 12, but not at the 24 months time point, consistent with a crucial role of insulin and NPY in cognitive functioning. By 24 months of age all groups demonstrated similar reductions in spatial memory performance. Together, these data suggest that the mechanisms through which insulin influences cognitive functioning are, at least in part, via insulin receptor signaling in NPY expressing neurons. These results also highlight that cognitive impairments observed in aging may be due to impaired insulin signaling.