RESUMEN
Super-enhancers (SEs) are expansive regions of genomic DNA that regulate the expression of genes involved in cell identity and cell fate. We recently identified developmental stage- and cell type-specific modules within the murine Vsx2 SE. Here, we show that the human VSX2 SE modules have similar developmental stage- and cell type-specific activity in reporter gene assays. By inserting the human sequence of one VSX2 SE module into a mouse with microphthalmia, eye size was rescued. To understand the function of these SE modules during human retinal development, we deleted individual modules in human embryonic stem cells and generated retinal organoids. Deleting one module results in small organoids, recapitulating the small-eyed phenotype of mice with microphthalmia, while deletion of the other module led to disruptions in bipolar neuron development. This prototypical SE serves as a model for understanding developmental stage- and cell type-specific effects of neurogenic transcription factors with complex expression patterns. Moreover, by elucidating the gene regulatory mechanisms, we can begin to examine how dysregulation of these mechanisms contributes to phenotypic diversity and disease.
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Elementos de Facilitación Genéticos , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio , Retina , Factores de Transcripción , Animales , Humanos , Ratones , Elementos de Facilitación Genéticos/genética , Evolución Molecular , Proteínas de Homeodominio/metabolismo , Proteínas de Homeodominio/genética , Células Madre Embrionarias Humanas/metabolismo , Células Madre Embrionarias Humanas/citología , Microftalmía/genética , Microftalmía/patología , Neurogénesis/genética , Organoides/metabolismo , Retina/metabolismo , Factores de Transcripción/metabolismo , Factores de Transcripción/genéticaRESUMEN
Meaningful auditory memories are formed in adults when acoustic information is delivered to the auditory cortex during heightened states of attention, vigilance, or alertness, as mediated by neuromodulatory circuits. Here, we identify that, in awake mice, acoustic stimulation triggers auditory thalamocortical projections to release adenosine, which prevents cortical plasticity (i.e., selective expansion of neural representation of behaviorally relevant acoustic stimuli) and perceptual learning (i.e., experience-dependent improvement in frequency discrimination ability). This sound-evoked adenosine release (SEAR) becomes reduced within seconds when acoustic stimuli are tightly paired with the activation of neuromodulatory (cholinergic or dopaminergic) circuits or periods of attentive wakefulness. If thalamic adenosine production is enhanced, then SEAR elevates further, the neuromodulatory circuits are unable to sufficiently reduce SEAR, and associative cortical plasticity and perceptual learning are blocked. This suggests that transient low-adenosine periods triggered by neuromodulatory circuits permit associative cortical plasticity and auditory perceptual learning in adults to occur.
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Corteza Auditiva , Animales , Ratones , Corteza Auditiva/fisiología , Adenosina , Aprendizaje/fisiología , Estimulación Acústica , SonidoRESUMEN
Super-enhancers (SEs) are expansive regions of genomic DNA that regulate the expression of genes involved in cell identity and cell fate. Recently, we found that distinct modules within a murine SE regulate gene expression of master regulatory transcription factor Vsx2 in a developmental stage- and cell-type specific manner. Vsx2 is expressed in retinal progenitor cells as well as differentiated bipolar neurons and Müller glia. Mutations in VSX2 in humans and mice lead to microphthalmia due to a defect in retinal progenitor cell proliferation. Deletion of a single module within the Vsx2 SE leads to microphthalmia. Deletion of a separate module within the SE leads to a complete loss of bipolar neurons, yet the remainder of the retina develops normally. Furthermore, the Vsx2 SE is evolutionarily conserved in vertebrates, suggesting that these modules are important for retinal development across species. In the present study, we examine the ability of these modules to drive retinal development between species. By inserting the human build of one Vsx2 SE module into a mouse with microphthalmia, eye size was rescued. To understand the implications of these SE modules in a model of human development, we generated human retinal organoids. Deleting one module results in small organoids, recapitulating the small-eyed phenotype of mice with microphthalmia, while deletion of the other module leads to a complete loss of ON cone bipolar neurons. This prototypical SE serves as a model for uncoupling developmental stage- and cell-type specific effects of neurogenic transcription factors with complex expression patterns. Moreover, by elucidating the gene regulatory mechanisms, we can begin to examine how dysregulation of these mechanisms contributes to phenotypic diversity and disease.
RESUMEN
Mutations in HNRNPH2 cause an X-linked neurodevelopmental disorder with features that include developmental delay, motor function deficits, and seizures. More than 90% of patients with hnRNPH2 have a missense mutation within or adjacent to the nuclear localization signal (NLS) of hnRNPH2. Here, we report that hnRNPH2 NLS mutations caused reduced interaction with the nuclear transport receptor Kapß2 and resulted in modest cytoplasmic accumulation of hnRNPH2. We generated 2 knockin mouse models with human-equivalent mutations in Hnrnph2 as well as Hnrnph2-KO mice. Knockin mice recapitulated clinical features of the human disorder, including reduced survival in male mice, impaired motor and cognitive functions, and increased susceptibility to audiogenic seizures. In contrast, 2 independent lines of Hnrnph2-KO mice showed no detectable phenotypes. Notably, KO mice had upregulated expression of Hnrnph1, a paralog of Hnrnph2, whereas knockin mice failed to upregulate Hnrnph1. Thus, genetic compensation by Hnrnph1 may counteract the loss of hnRNPH2. These findings suggest that HNRNPH2-related disorder may be driven by a toxic gain of function or a complex loss of HNRNPH2 function with impaired compensation by HNRNPH1. The knockin mice described here are an important resource for preclinical studies to assess the therapeutic benefit of gene replacement or knockdown of mutant hnRNPH2.
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Trastornos del Neurodesarrollo , Animales , Humanos , Masculino , Ratones , Modelos Animales de Enfermedad , Mutación , Mutación Missense , Convulsiones/genéticaRESUMEN
Williams-Beuren syndrome (WBS) is a rare disorder caused by hemizygous microdeletion of â¼27 contiguous genes. Despite neurodevelopmental and cognitive deficits, individuals with WBS have spared or enhanced musical and auditory abilities, potentially offering an insight into the genetic basis of auditory perception. Here, we report that the mouse models of WBS have innately enhanced frequency-discrimination acuity and improved frequency coding in the auditory cortex (ACx). Chemogenetic rescue showed frequency-discrimination hyperacuity is caused by hyperexcitable interneurons in the ACx. Haploinsufficiency of one WBS gene, Gtf2ird1, replicated WBS phenotypes by downregulating the neuropeptide receptor VIPR1. VIPR1 is reduced in the ACx of individuals with WBS and in the cerebral organoids derived from human induced pluripotent stem cells with the WBS microdeletion. Vipr1 deletion or overexpression in ACx interneurons mimicked or reversed, respectively, the cellular and behavioral phenotypes of WBS mice. Thus, the Gtf2ird1-Vipr1 mechanism in ACx interneurons may underlie the superior auditory acuity in WBS.
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Corteza Auditiva/fisiología , Síndrome de Williams/fisiopatología , Animales , Corteza Auditiva/citología , Modelos Animales de Enfermedad , Humanos , Células Madre Pluripotentes Inducidas , Interneuronas/citología , Interneuronas/fisiología , Ratones , Fenotipo , Transactivadores/genética , Síndrome de Williams/genéticaRESUMEN
Recent proteome and transcriptome profiling of Alzheimer's disease (AD) brains reveals RNA splicing dysfunction and U1 small nuclear ribonucleoprotein (snRNP) pathology containing U1-70K and its N-terminal 40-KDa fragment (N40K). Here we present a causative role of U1 snRNP dysfunction to neurodegeneration in primary neurons and transgenic mice (N40K-Tg), in which N40K expression exerts a dominant-negative effect to downregulate full-length U1-70K. N40K-Tg recapitulates N40K insolubility, erroneous splicing events, neuronal degeneration and cognitive impairment. Specifically, N40K-Tg shows the reduction of GABAergic synapse components (e.g., the GABA receptor subunit of GABRA2), and concomitant postsynaptic hyperexcitability that is rescued by a GABA receptor agonist. Crossing of N40K-Tg and the 5xFAD amyloidosis model indicates that the RNA splicing defect synergizes with the amyloid cascade to remodel the brain transcriptome and proteome, deregulate synaptic proteins, and accelerate cognitive decline. Thus, our results support the contribution of U1 snRNP-mediated splicing dysfunction to AD pathogenesis.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Animales , Ratones , Ribonucleoproteína Nuclear Pequeña U1/genética , Enfermedad de Alzheimer/genética , Proteoma/genética , Empalme del ARN/genética , Disfunción Cognitiva/genéticaRESUMEN
Noncanonical functions of autophagy proteins have been implicated in neurodegenerative conditions, including Alzheimer's disease (AD). The WD domain of the autophagy protein Atg16L is dispensable for canonical autophagy but required for its noncanonical functions. Two-year-old mice lacking this domain presented with robust ß-amyloid (Aß) pathology, tau hyperphosphorylation, reactive microgliosis, pervasive neurodegeneration, and severe behavioral and memory deficiencies, consistent with human disease. Mechanistically, we found this WD domain was required for the recycling of Aß receptors in primary microglia. Pharmacologic suppression of neuroinflammation reversed established memory impairment and markers of disease pathology in this novel AD model. Therefore, loss of the Atg16L WD domain drives spontaneous AD in mice, and inhibition of neuroinflammation is a potential therapeutic approach for treating neurodegeneration and memory loss. A decline in expression of ATG16L in the brains of human patients with AD suggests the possibility that a similar mechanism may contribute in human disease.
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Enfermedad de Alzheimer , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Animales , Autofagia , Modelos Animales de Enfermedad , Humanos , Ratones , Microglía/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismoRESUMEN
The expression of some proteins in the autophagy pathway declines with age, which may impact neurodegeneration in diseases, including Alzheimer's Disease. We have identified a novel non-canonical function of several autophagy proteins in the conjugation of LC3 to Rab5+, clathrin+ endosomes containing ß-amyloid in a process of LC3-associated endocytosis (LANDO). We found that LANDO in microglia is a critical regulator of immune-mediated aggregate removal and microglial activation in a murine model of AD. Mice lacking LANDO but not canonical autophagy in the myeloid compartment or specifically in microglia have a robust increase in pro-inflammatory cytokine production in the hippocampus and increased levels of neurotoxic ß-amyloid. This inflammation and ß-amyloid deposition were associated with reactive microgliosis and tau hyperphosphorylation. LANDO-deficient AD mice displayed accelerated neurodegeneration, impaired neuronal signaling, and memory deficits. Our data support a protective role for LANDO in microglia in neurodegenerative pathologies resulting from ß-amyloid deposition.
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Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Endocitosis , Proteínas Asociadas a Microtúbulos/metabolismo , Enfermedad de Alzheimer/metabolismo , Animales , Proteína 5 Relacionada con la Autofagia/deficiencia , Proteína 5 Relacionada con la Autofagia/genética , Proteínas Relacionadas con la Autofagia/deficiencia , Proteínas Relacionadas con la Autofagia/genética , Antígenos CD36/metabolismo , Citocinas/metabolismo , Modelos Animales de Enfermedad , Hipocampo/metabolismo , Péptidos y Proteínas de Señalización Intracelular/deficiencia , Péptidos y Proteínas de Señalización Intracelular/genética , Glicoproteínas de Membrana/metabolismo , Ratones , Ratones Transgénicos , Microglía/citología , Microglía/metabolismo , Células RAW 264.7 , Receptores Inmunológicos/metabolismo , Receptor Toll-Like 4/metabolismoRESUMEN
SEC24 family members are components of the coat protein complex II (COPII) machinery that interact directly with cargo or with other adapters to ensure proper sorting of secretory cargo into COPII vesicles. SEC24C is 1 of 4 mammalian SEC24 paralogs (SEC24A-D), which segregate into 2 subfamilies on the basis of sequence homology (SEC24A/SEC24B and SEC24C/SEC24D). Here, we demonstrate that postmitotic neurons, unlike professional secretory cells in other tissues, are exquisitely sensitive to loss of SEC24C. Conditional KO of Sec24c in neural progenitors during embryogenesis caused perinatal mortality and microcephaly, with activation of the unfolded protein response and apoptotic cell death of postmitotic neurons in the murine cerebral cortex. The cell-autonomous function of SEC24C in postmitotic neurons was further highlighted by the loss of cell viability caused by disrupting Sec24c expression in forebrain neurons of mice postnatally and in differentiated neurons derived from human induced pluripotent stem cells. The neuronal cell death associated with Sec24c deficiency was rescued in knockin mice expressing Sec24d in place of Sec24c. These data suggest that SEC24C is a major cargo adapter for COPII-dependent transport in postmitotic neurons in developing and adult brains and that its functions overlap at least partially with those of SEC24D in mammals.
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Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Homeostasis , Células-Madre Neurales/metabolismo , Neuronas/metabolismo , Prosencéfalo/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Animales , Vesículas Cubiertas por Proteínas de Revestimiento/genética , Humanos , Células Madre Pluripotentes Inducidas/citología , Células Madre Pluripotentes Inducidas/metabolismo , Ratones , Ratones Noqueados , Células-Madre Neurales/citología , Neuronas/citología , Prosencéfalo/citología , Proteínas de Transporte Vesicular/genéticaRESUMEN
Circuits in the auditory cortex are highly susceptible to acoustic influences during an early postnatal critical period. The auditory cortex selectively expands neural representations of enriched acoustic stimuli, a process important for human language acquisition. Adults lack this plasticity. Here we show in the murine auditory cortex that juvenile plasticity can be reestablished in adulthood if acoustic stimuli are paired with disruption of ecto-5'-nucleotidase-dependent adenosine production or A1-adenosine receptor signaling in the auditory thalamus. This plasticity occurs at the level of cortical maps and individual neurons in the auditory cortex of awake adult mice and is associated with long-term improvement of tone-discrimination abilities. We conclude that, in adult mice, disrupting adenosine signaling in the thalamus rejuvenates plasticity in the auditory cortex and improves auditory perception.
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Adenosina/metabolismo , Corteza Auditiva/metabolismo , Transducción de Señal , 5'-Nucleotidasa/metabolismo , Adenosina/administración & dosificación , Adenosina/análogos & derivados , Agonistas del Receptor de Adenosina A1/administración & dosificación , Antagonistas del Receptor de Adenosina A1/administración & dosificación , Animales , Percepción Auditiva , Proteínas Ligadas a GPI/metabolismo , Ratones , Plasticidad Neuronal , Piperidinas/administración & dosificación , Piridazinas/administración & dosificación , Receptor de Adenosina A1/metabolismo , Tálamo/metabolismoRESUMEN
Memory is formed by synapse-to-nucleus communication that leads to regulation of gene transcription, but the identity and organizational logic of signaling pathways involved in this communication remain unclear. Here we find that the transcription cofactor CRTC1 is a critical determinant of sustained gene transcription and memory strength in the hippocampus. Following associative learning, synaptically localized CRTC1 is translocated to the nucleus and regulates Fgf1b transcription in an activity-dependent manner. After both weak and strong training, the HDAC3-N-CoR corepressor complex leaves the Fgf1b promoter and a complex involving the translocated CRTC1, phosphorylated CREB, and histone acetyltransferase CBP induces transient transcription. Strong training later substitutes KAT5 for CBP, a process that is dependent on CRTC1, but not on CREB phosphorylation. This in turn leads to long-lasting Fgf1b transcription and memory enhancement. Thus, memory strength relies on activity-dependent changes in chromatin and temporal regulation of gene transcription on specific CREB/CRTC1 gene targets.
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Núcleo Celular/metabolismo , Ensamble y Desensamble de Cromatina , Factor 1 de Crecimiento de Fibroblastos/genética , Memoria , Factores de Transcripción/metabolismo , Animales , Calcineurina/metabolismo , Epigénesis Genética , Hipocampo/metabolismo , Histona Desacetilasas/metabolismo , Potenciación a Largo Plazo/genética , Lisina Acetiltransferasa 5/metabolismo , Masculino , Ratones Endogámicos C57BL , Plasticidad Neuronal/genética , Neuronas/metabolismo , Transporte de Proteínas , Transactivadores/metabolismo , Transcripción Genética , Activación Transcripcional/genéticaRESUMEN
Autism spectrum disorders (ASDs) are a group of neurodevelopmental afflictions characterized by repetitive behaviors, deficits in social interaction, and impaired communication skills. For most ASD patients, the underlying causes are unknown. Genetic mutations have been identified in about 25 percent of ASD cases, including mutations in epigenetic regulators, suggesting that dysregulated chromatin or DNA function is a critical component of ASD. Mutations in the histone acetyltransferase CREB binding protein (CBP, CREBBP) cause Rubinstein-Taybi Syndrome (RTS), a developmental disorder that includes ASD-like symptoms. Recently, genomic studies involving large numbers of ASD patient families have theoretically modeled CBP and its paralog p300 (EP300) as critical hubs in ASD-associated protein and gene interaction networks, and have identified de novo missense mutations in highly conserved residues of the CBP acetyltransferase and CH1 domains. Here we provide animal model evidence that supports this notion that CBP and its CH1 domain are relevant to autism. We show that mice with a deletion mutation in the CBP CH1 (TAZ1) domain (CBPΔCH1/ΔCH1) have an RTS-like phenotype that includes ASD-relevant repetitive behaviors, hyperactivity, social interaction deficits, motor dysfunction, impaired recognition memory, and abnormal synaptic plasticity. Our results therefore indicate that loss of CBP CH1 domain function contributes to RTS, and possibly ASD, and that this domain plays an essential role in normal motor function, cognition and social behavior. Although the key physiological functions affected by ASD-associated mutation of epigenetic regulators have been enigmatic, our findings are consistent with theoretical models involving CBP and p300 in ASD, and with a causative role for recently described ASD-associated CBP mutations.
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Trastorno Autístico/genética , Proteína de Unión a CREB/genética , Histona Acetiltransferasas/genética , Mutación , Síndrome de Rubinstein-Taybi/genética , Análisis de Varianza , Animales , Trastorno Autístico/enzimología , Trastorno Autístico/fisiopatología , Sitios de Unión/genética , Proteína de Unión a CREB/metabolismo , Anomalías Craneofaciales/genética , Anomalías Craneofaciales/fisiopatología , Hipocampo/metabolismo , Hipocampo/fisiopatología , Histona Acetiltransferasas/metabolismo , Humanos , Potenciación a Largo Plazo/genética , Potenciación a Largo Plazo/fisiología , Aprendizaje por Laberinto/fisiología , Trastornos de la Memoria/genética , Trastornos de la Memoria/fisiopatología , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora/genética , Actividad Motora/fisiología , Fenotipo , Síndrome de Rubinstein-Taybi/enzimología , Síndrome de Rubinstein-Taybi/fisiopatología , Conducta SocialRESUMEN
BACKGROUND: Daily rhythms in mammals are programmed by a master clock in the suprachiasmatic nucleus (SCN). The SCN contains two main compartments (shell and core), but the role of each region in system-level coordination remains ill defined. Herein, we use a functional assay to investigate how downstream tissues interpret region-specific outputs by using in vivo exposure to long day photoperiods to temporally dissociate the SCN. We then analyze resulting changes in the rhythms of clocks located throughout the brain and body to examine whether they maintain phase synchrony with the SCN shell or core. RESULTS: Nearly all of the 17 tissues examined in the brain and body maintain phase synchrony with the SCN shell, but not the SCN core, which indicates that downstream oscillators are set by cues controlled specifically by the SCN shell. Interestingly, we also found that SCN dissociation diminished the amplitude of rhythms in core clock gene and protein expression in brain tissues by 50-75 %, which suggests that light-driven changes in the functional organization of the SCN markedly influence the strength of rhythms in downstream tissues. CONCLUSIONS: Overall, our results reveal that body clocks receive time-of-day cues specifically from the SCN shell, which may be an adaptive design principle that serves to maintain system-level phase relationships in a changing environment. Further, we demonstrate that lighting conditions alter the amplitude of the molecular clock in downstream tissues, which uncovers a new form of plasticity that may contribute to seasonal changes in physiology and behavior.
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Encéfalo/fisiología , Relojes Circadianos , Neuronas/citología , Núcleo Supraquiasmático/citología , Animales , Encéfalo/citología , Ritmo Circadiano , Luz , Masculino , Ratones Endogámicos C57BL , Neuronas/fisiología , FotoperiodoRESUMEN
Peroxisome proliferator-activated receptor γ (PPARγ) is clinically targeted for type II diabetes treatment; however, rosiglitazone (ROSI), a PPARγ agonist, increases food intake and body/fat mass as side-effects. Mechanisms for these effects and the role of PPARγ in feeding are not understood. Therefore, we tested this role in Siberian hamsters, a model of human energy balance, and C57BL/6 mice. We tested the following: (1) how ROSI and/or GW9662 (2-chloro-5-nitro-N-phenylbenzamide; PPARγ antagonist) injected intraperitoneally or into the third ventricle (3V) affected Siberian hamster feeding behaviors; (2) whether food deprivation (FD) co-increases agouti-related protein (AgRP) and PPARγ mRNA expression in Siberian hamsters and mice; (3) whether intraperitoneally administered ROSI increases AgRP and NPY in ad libitum-fed animals; (4) whether intraperitoneally administered PPARγ antagonism blocks FD-induced increases in AgRP and NPY; and finally, (5) whether intraperitoneally administered PPARγ modulation affects plasma ghrelin. Third ventricular and intraperitoneally administered ROSI increased food hoarding and intake for 7 d, an effect attenuated by 3V GW9662, and also prevented (intraperitoneal) FD-induced feeding. FD hamsters and mice increased AgRP within the arcuate hypothalamic nucleus with concomitant increases in PPARγ exclusively within AgRP/NPY neurons. ROSI increased AgRP and NPY similarly to FD, and GW9662 prevented FD-induced increases in AgRP and NPY in both species. Neither ROSI nor GW9662 affected plasma ghrelin. Thus, we demonstrated that PPARγ activation is sufficient to trigger food hoarding/intake, increase AgRP/NPY, and possibly is necessary for FD-induced increases in feeding and AgRP/NPY. These findings provide initial evidence that FD-induced increases in AgRP/NPY may be a direct PPARγ-dependent process that controls ingestive behaviors.
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Proteína Relacionada con Agouti/biosíntesis , Núcleo Arqueado del Hipotálamo/metabolismo , Conducta Alimentaria/fisiología , Neuropéptido Y/biosíntesis , PPAR gamma/biosíntesis , ARN Mensajero/biosíntesis , Animales , Cricetinae , Conducta Alimentaria/psicología , Ratones , Ratones Endogámicos C57BL , PhodopusRESUMEN
Seasonal responses of many animal species are triggered by changes in daylength and its transduction into a neuroendocrine signal by the pineal gland through the nocturnal duration of melatonin (MEL) release. The precise central sites necessary to receive, transduce, and relay the short day (SD) fall-winter MEL signals into seasonal responses and changes in physiology and behavior are unclear. In Siberian hamsters, SDs trigger decreases in body and lipid mass, testicular regression and pelage color changes. Several candidate genes and their central sites of expression have been proposed as components of the MEL transduction system with considerable recent focus on the arcuate nucleus (ARC) and its component, the dorsomedial posterior arcuate nucleus (dmpARC). This site has been postulated as a critical relay of SD information through the modulation of a variety of neurochemicals/receptors important for the control of energy balance. Here the necessity of an intact dmpARC for SD responses was tested by making electrolytic lesions of the Siberian hamster dmpARC and then exposing them to either long days (LD) or SDs for 12wks. The SD typical decreases in body and fat mass, food intake, testicular volume, serum testosterone concentrations, pelage color change and increased UCP-1 protein expression (a proxy for brown adipose tissue thermogenesis) all occurred despite the lack of an intact dmpARC. Although the Siberian hamster dmpARC contains photoperiod-modulated constituents, these data demonstrate that an intact dmpARC is not necessary for SD responses and not integral to the seasonal energy- and reproductive-related responses measured here.
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Núcleo Arqueado del Hipotálamo/fisiología , Fotoperiodo , Animales , Peso Corporal/fisiología , Ritmo Circadiano/fisiología , Cricetinae , Ingestión de Alimentos/fisiología , Metabolismo Energético/fisiología , Femenino , Color del Cabello , Canales Iónicos/metabolismo , Masculino , Melatonina/metabolismo , Proteínas Mitocondriales/metabolismo , Phodopus , Glándula Pineal/metabolismo , Estaciones del Año , Testículo/fisiología , Testosterona/sangre , Proteína Desacopladora 1RESUMEN
Central administration of neuropeptide Y (NPY) increases food intake in laboratory rats and mice, as well as food foraging and hoarding in Siberian hamsters. The NPY-Y1 and Y5 receptors (Rs) within the hypothalamus appear sufficient to account for these increases in ingestive behaviors. Stimulation of NPY-Y2Rs in the Arcuate nucleus (Arc) has an anorexigenic effect as shown by central or peripheral administration of its natural ligand peptide YY (3-36) and pharmacological NPY-Y2R antagonism by BIIE0246 increases food intake. Both effects on food intake by NPY-Y2R agonism and antagonism are relatively short-lived lasting â¼4h. The role of NPY-Y2Rs in appetitive ingestive behaviors (food foraging/hoarding) is untested, however. Therefore, Siberians hamsters, a natural food hoarder, were housed in a semi-natural burrow/foraging system that had (a) foraging requirement (10 revolutions/pellet), no free food (true foraging group), (b) no running wheel access, free food (general malaise control) or (c) running wheel access, free food (exercise control). We microinjected BIIE0246 (antagonist) and PYY(3-36) (agonist) into the Arc to test the role of NPY-Y2Rs there on ingestive behaviors. Food foraging, hoarding, and intake were not affected by Arc BIIE0246 microinjection in fed hamsters 1, 2, 4, and 24h post injection. Stimulation of NPY-Y2Rs by PYY(3-36) inhibited food intake at 0-1 and 1-2h and food hoarding at 1-2h without causing general malaise or affecting foraging. Collectively, these results implicate a sufficiency, but not necessity, of the Arc NPY-Y2R in the inhibition of food intake and food hoarding by Siberian hamsters.
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Núcleo Arqueado del Hipotálamo/efectos de los fármacos , Arginina/análogos & derivados , Benzazepinas/farmacología , Ingestión de Alimentos/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Péptido YY/farmacología , Receptores de Neuropéptido Y/metabolismo , Animales , Núcleo Arqueado del Hipotálamo/fisiología , Arginina/farmacología , Cateterismo , Cricetinae , Relación Dosis-Respuesta a Droga , Ingestión de Alimentos/fisiología , Conducta Alimentaria/fisiología , Privación de Alimentos , Inyecciones Intraventriculares , Masculino , Phodopus , Receptores de Neuropéptido Y/agonistas , Receptores de Neuropéptido Y/antagonistas & inhibidores , Técnicas EstereotáxicasRESUMEN
Circulating concentrations of the stomach-derived "hunger-peptide" ghrelin increase in direct proportion to the time since the last meal. Exogenous ghrelin also increases food intake in rodents and humans, suggesting ghrelin may increase post-fast ingestive behaviors. Food intake after food deprivation is increased by laboratory rats and mice, but not by humans (despite dogma to the contrary) or by Siberian hamsters; instead, humans and Siberian hamsters increase food hoarding, suggesting the latter as a model of fasting-induced changes in human ingestive behavior. Exogenous ghrelin markedly increases food hoarding by ad libitum-fed Siberian hamsters similarly to that after food deprivation, indicating sufficiency. Here, we tested the necessity of ghrelin to increase food foraging, food hoarding, and food intake, and neural activation [c-Fos immunoreactivity (c-Fos-ir)] using anti-ghrelin Spiegelmer NOX-B11-2 (SPM), an l-oligonucleotide that specifically binds active ghrelin, inhibiting peptide-receptor interaction. SPM blocked exogenous ghrelin-induced increases in food hoarding the first 2 days after injection, and foraging and food intake at 1-2 h and 2-4 h, respectively, and inhibited hypothalamic c-Fos-ir. SPM given every 24 h across 48-h food deprivation inconsistently inhibited food hoarding after refeeding and c-Fos-ir, similarly to inabilities to do so in laboratory rats and mice. These results suggest that ghrelin may not be necessary for food deprivation-induced foraging and hoarding and neural activation. A possible compensatory response, however, may underlie these findings because SPM treatment led to marked increases in circulating ghrelin concentrations. Collectively, these results show that SPM can block exogenous ghrelin-induced ingestive behaviors, but the necessity of ghrelin for food deprivation-induced ingestive behaviors remains unclear.
Asunto(s)
Regulación del Apetito , Aptámeros de Nucleótidos/metabolismo , Ingestión de Alimentos , Privación de Alimentos , Ghrelina/metabolismo , Acaparamiento , Hipotálamo/metabolismo , Neuronas/metabolismo , Animales , Aptámeros de Nucleótidos/administración & dosificación , Cricetinae , Ghrelina/administración & dosificación , Ghrelina/genética , Inmunohistoquímica , Inyecciones Intraperitoneales , Masculino , Phodopus , Proteínas Proto-Oncogénicas c-fos/metabolismo , Factores de TiempoRESUMEN
Ghrelin is an orexigenic hormone produced by the stomach in direct proportion to the time since the last meal and has therefore been called a 'hunger signal'. The octanoylation of ghrelin is critical for its orexigenic functions and is dependent upon ghrelin O-acyltransferase (GOAT) catalyzation. The GOAT inhibitor, GO-CoA-Tat, decreases the circulating concentrations of octanoylated ghrelin and attenuates weight gain on a high fat diet in mice. Unlike rats and mice, Siberian hamsters and humans do not increase food intake after food deprivation, but increase food hoarding after food deprivation. In Siberian hamsters, exogenous ghrelin increases ingestive behaviors similarly to 48-56 h food deprivation. Therefore, we tested the necessity of increased ghrelin in food-deprived Siberian hamsters to stimulate ingestive behaviors. To do so we used our simulated natural housing system that allows hamsters to forage for and hoard food. Animals were given an injection of GO-CoA-Tat (i.p., 11 µmol/kg) every 6h because that is the duration of its effective inhibition of octanoylated ghrelin concentrations during a 48 h food deprivation. We found that GO-CoA-Tat attenuated food foraging (0-1h), food intake (0-1 and 2-4h), and food hoarding (0-1h and 2 and 3 days) post-refeeding compared with saline treated animals. This suggests that increased octanoylated ghrelin concentrations play a role in the food deprivation-induced increases in ingestive behavior. Therefore, ghrelin is a critical aspect of the multi-faceted mechanisms that stimulate ingestive behaviors, and might be a critical point for a successful clinical intervention scheme in humans.