1
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Gao Z, Guan J, Yin S, Liu F. The role of ATP in sleep-wake regulation: In adenosine-dependent and -independent manner. Sleep Med 2024; 119:147-154. [PMID: 38678758 DOI: 10.1016/j.sleep.2024.04.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 03/31/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
ATP plays a crucial role as an energy currency in the body's various physiological functions, including the regulation of the sleep-wake cycle. Evidence from genetics and pharmacology demonstrates a strong association between ATP metabolism and sleep. With the advent of new technologies such as optogenetics, genetically encoded biosensors, and novel ATP detection methods, the dynamic changes in ATP levels between different sleep states have been further uncovered. The classic mechanism for regulating sleep by ATP involves its conversion to adenosine, which increases sleep pressure when accumulated extracellularly. However, emerging evidence suggests that ATP can directly bind to P2 receptors and influence sleep-wake regulation through both adenosine-dependent and independent pathways. The outcome depends on the brain region where ATP acts and the expression type of P2 receptors. This review summarizes the experimental evidence on the relationship between ATP levels and changes in sleep states and outlines the mechanisms by which ATP is involved in regulating the sleep-wake cycle through both adenosine-dependent and independent pathways. Hopefully, this review will provide a comprehensive understanding of the current research basis and progress in this field and promote further investigations into the specific mechanisms of ATP in regulating sleep.
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Affiliation(s)
- Zhenfei Gao
- Shanghai Key Laboratory of Sleep Disordered Breathing, Department of Otolaryngology-Head and Neck Surgery, Otolaryngology Institute of Shanghai Jiaotong University, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China
| | - Jian Guan
- Shanghai Key Laboratory of Sleep Disordered Breathing, Department of Otolaryngology-Head and Neck Surgery, Otolaryngology Institute of Shanghai Jiaotong University, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
| | - Shankai Yin
- Shanghai Key Laboratory of Sleep Disordered Breathing, Department of Otolaryngology-Head and Neck Surgery, Otolaryngology Institute of Shanghai Jiaotong University, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
| | - Feng Liu
- Shanghai Key Laboratory of Sleep Disordered Breathing, Department of Otolaryngology-Head and Neck Surgery, Otolaryngology Institute of Shanghai Jiaotong University, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
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2
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Natsubori A, Hirai S, Kwon S, Ono D, Deng F, Wan J, Miyazawa M, Kojima T, Okado H, Karashima A, Li Y, Tanaka KF, Honda M. Serotonergic neurons control cortical neuronal intracellular energy dynamics by modulating astrocyte-neuron lactate shuttle. iScience 2023; 26:105830. [PMID: 36713262 PMCID: PMC9881222 DOI: 10.1016/j.isci.2022.105830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 08/15/2022] [Accepted: 12/12/2022] [Indexed: 01/07/2023] Open
Abstract
The central serotonergic system has multiple roles in animal physiology and behavior, including sleep-wake control. However, its function in controlling brain energy metabolism according to the state of animals remains undetermined. Through in vivo monitoring of energy metabolites and signaling, we demonstrated that optogenetic activation of raphe serotonergic neurons increased cortical neuronal intracellular concentration of ATP, an indispensable cellular energy molecule, which was suppressed by inhibiting neuronal uptake of lactate derived from astrocytes. Raphe serotonergic neuronal activation induced cortical astrocytic Ca2+ and cAMP surges and increased extracellular lactate concentrations, suggesting the facilitation of lactate release from astrocytes. Furthermore, chemogenetic inhibition of raphe serotonergic neurons partly attenuated the increase in cortical neuronal intracellular ATP levels as arousal increased in mice. Serotonergic neuronal activation promoted an increase in cortical neuronal intracellular ATP levels, partly mediated by the facilitation of the astrocyte-neuron lactate shuttle, contributing to state-dependent optimization of neuronal intracellular energy levels.
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Affiliation(s)
- Akiyo Natsubori
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan,Corresponding author
| | - Shinobu Hirai
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Soojin Kwon
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Daisuke Ono
- Department of Neuroscience Ⅱ, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan,Department of Neural Regulation, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Fei Deng
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing 100871, China,PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China
| | - Jinxia Wan
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing 100871, China,PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China
| | - Momoka Miyazawa
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan,Faculty of Science Division Ⅱ, Tokyo University of Science, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Takashi Kojima
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Haruo Okado
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Akihiro Karashima
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, Sendai 982-8577, Japan
| | - Yulong Li
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing 100871, China,PKU-IDG/McGovern Institute for Brain Research, Beijing 100871, China
| | - Kenji F. Tanaka
- Division of Brain Sciences, Institute for Advanced Medical Research, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Makoto Honda
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
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3
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Takahashi T, Stoiljkovic M, Song E, Gao XB, Yasumoto Y, Kudo E, Carvalho F, Kong Y, Park A, Shanabrough M, Szigeti-Buck K, Liu ZW, Kristant A, Zhang Y, Sulkowski P, Glazer PM, Kaczmarek LK, Horvath TL, Iwasaki A. LINE-1 activation in the cerebellum drives ataxia. Neuron 2022; 110:3278-3287.e8. [PMID: 36070749 PMCID: PMC9588660 DOI: 10.1016/j.neuron.2022.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 06/29/2022] [Accepted: 08/05/2022] [Indexed: 02/06/2023]
Abstract
Dysregulation of long interspersed nuclear element 1 (LINE-1, L1), a dominant class of transposable elements in the human genome, has been linked to neurodegenerative diseases, but whether elevated L1 expression is sufficient to cause neurodegeneration has not been directly tested. Here, we show that the cerebellar expression of L1 is significantly elevated in ataxia telangiectasia patients and strongly anti-correlated with the expression of epigenetic silencers. To examine the role of L1 in the disease etiology, we developed an approach for direct targeting of the L1 promoter for overexpression in mice. We demonstrated that L1 activation in the cerebellum led to Purkinje cell dysfunctions and degeneration and was sufficient to cause ataxia. Treatment with a nucleoside reverse transcriptase inhibitor blunted ataxia progression by reducing DNA damage, attenuating gliosis, and reversing deficits of molecular regulators for calcium homeostasis in Purkinje cells. Our study provides the first direct evidence that L1 activation can drive neurodegeneration.
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Affiliation(s)
- Takehiro Takahashi
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Milan Stoiljkovic
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Eric Song
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Xiao-Bing Gao
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Yuki Yasumoto
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Eriko Kudo
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Fernando Carvalho
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Yong Kong
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Annsea Park
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Marya Shanabrough
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Klara Szigeti-Buck
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Zhong-Wu Liu
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Ashley Kristant
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Yalan Zhang
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Parker Sulkowski
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Peter M Glazer
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Leonard K Kaczmarek
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Tamas L Horvath
- Department of Comparative Medicine and Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT 06510, USA.
| | - Akiko Iwasaki
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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4
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Stutz B, Waterson MJ, Šestan-Peša M, Dietrich MO, Škarica M, Sestan N, Racz B, Magyar A, Sotonyi P, Liu ZW, Gao XB, Matyas F, Stoiljkovic M, Horvath TL. AgRP neurons control structure and function of the medial prefrontal cortex. Mol Psychiatry 2022; 27:3951-3960. [PMID: 35906488 PMCID: PMC9891653 DOI: 10.1038/s41380-022-01691-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/28/2022] [Accepted: 06/29/2022] [Indexed: 02/07/2023]
Abstract
Hypothalamic agouti-related peptide and neuropeptide Y-expressing (AgRP) neurons have a critical role in both feeding and non-feeding behaviors of newborn, adolescent, and adult mice, suggesting their broad modulatory impact on brain functions. Here we show that constitutive impairment of AgRP neurons or their peripubertal chemogenetic inhibition resulted in both a numerical and functional reduction of neurons in the medial prefrontal cortex (mPFC) of mice. These changes were accompanied by alteration of oscillatory network activity in mPFC, impaired sensorimotor gating, and altered ambulatory behavior that could be reversed by the administration of clozapine, a non-selective dopamine receptor antagonist. The observed AgRP effects are transduced to mPFC in part via dopaminergic neurons in the ventral tegmental area and may also be conveyed by medial thalamic neurons. Our results unmasked a previously unsuspected role for hypothalamic AgRP neurons in control of neuronal pathways that regulate higher-order brain functions during development and in adulthood.
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Affiliation(s)
- Bernardo Stutz
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Michael J Waterson
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Matija Šestan-Peša
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Marcelo O Dietrich
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Mario Škarica
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Nenad Sestan
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Bence Racz
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
| | - Aletta Magyar
- Institute of Cognitive Neuroscience and Psychology, Research Center for Natural Sciences, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Peter Sotonyi
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
| | - Zhong-Wu Liu
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Xiao-Bing Gao
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Ferenc Matyas
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
- Institute of Cognitive Neuroscience and Psychology, Research Center for Natural Sciences, Budapest, Hungary
- Institute of Experimental Medicine, Budapest, Hungary
| | - Milan Stoiljkovic
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Tamas L Horvath
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA.
- Yale Center for Molecular and Systems Metabolism, Yale University School of Medicine, New Haven, CT, USA.
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary.
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5
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Gao XB, Horvath TL. From Molecule to Behavior: Hypocretin/orexin Revisited From a Sex-dependent Perspective. Endocr Rev 2022; 43:743-760. [PMID: 34792130 PMCID: PMC9277634 DOI: 10.1210/endrev/bnab042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Indexed: 11/19/2022]
Abstract
The hypocretin/orexin (Hcrt/Orx) system in the perifornical lateral hypothalamus has been recognized as a critical node in a complex network of neuronal systems controlling both physiology and behavior in vertebrates. Our understanding of the Hcrt/Orx system and its array of functions and actions has grown exponentially in merely 2 decades. This review will examine the latest progress in discerning the roles played by the Hcrt/Orx system in regulating homeostatic functions and in executing instinctive and learned behaviors. Furthermore, the gaps that currently exist in our knowledge of sex-related differences in this field of study are discussed.
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Affiliation(s)
- Xiao-Bing Gao
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Tamas L Horvath
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
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6
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Zhou Y, Gu B, Brichant G, Singh JP, Yang H, Chang H, Zhao Y, Cheng C, Liu ZW, Alderman MH, Lu L, Yang X, Gao XB, Taylor HS. The steroid hormone estriol (E3) regulates epigenetic programming of fetal mouse brain and reproductive tract. BMC Biol 2022; 20:93. [PMID: 35491423 PMCID: PMC9059368 DOI: 10.1186/s12915-022-01293-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 04/11/2022] [Indexed: 12/13/2022] Open
Abstract
Abstract
Background
Estriol (E3) is a steroid hormone formed only during pregnancy in primates including humans. Although E3 is synthesized at large amounts through a complex pathway involving the fetus and placenta, it is not required for the maintenance of pregnancy and has classically been considered virtually inactive due to associated very weak canonical estrogen signaling. However, estrogen exposure during pregnancy may have an effect on organs both within and outside the reproductive system, and compounds with binding affinity for estrogen receptors weaker than E3 have been found to impact reproductive organs and the brain. Here, we explore potential effects of E3 on fetal development using mouse as a model system.
Results
We administered E3 to pregnant mice, exposing the fetus to E3. Adult females exposed to E3 in utero (E3-mice) had increased fertility and superior pregnancy outcomes. Female and male E3-mice showed decreased anxiety and increased exploratory behavior. The expression levels and DNA methylation patterns of multiple genes in the uteri and brains of E3-mice were distinct from controls. E3 promoted complexing of estrogen receptors with several DNA/histone modifiers and their binding to target genes. E3 functions by driving epigenetic change, mediated through epigenetic modifier interactions with estrogen receptors rather than through canonical nuclear transcriptional activation.
Conclusions
We identify an unexpected functional role for E3 in fetal reproductive system and brain. We further identify a novel mechanism of estrogen action, through recruitment of epigenetic modifiers to estrogen receptors and their target genes, which is not correlated with the traditional view of estrogen potency.
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7
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Watts AG, Kanoski SE, Sanchez-Watts G, Langhans W. The physiological control of eating: signals, neurons, and networks. Physiol Rev 2022; 102:689-813. [PMID: 34486393 PMCID: PMC8759974 DOI: 10.1152/physrev.00028.2020] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.
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Affiliation(s)
- Alan G Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Scott E Kanoski
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Graciela Sanchez-Watts
- The Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, Eidgenössische Technische Hochschule-Zürich, Schwerzenbach, Switzerland
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8
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Mavanji V, Pomonis B, Kotz CM. Orexin, serotonin, and energy balance. WIREs Mech Dis 2022; 14:e1536. [PMID: 35023323 PMCID: PMC9286346 DOI: 10.1002/wsbm.1536] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/27/2021] [Accepted: 08/23/2021] [Indexed: 12/02/2022]
Abstract
The lateral hypothalamus is critical for the control of ingestive behavior and spontaneous physical activity (SPA), as lesion or stimulation of this region alters these behaviors. Evidence points to lateral hypothalamic orexin neurons as modulators of feeding and SPA. These neurons affect a broad range of systems, and project to multiple brain regions such as the dorsal raphe nucleus, which contains serotoninergic neurons (DRN) important to energy homeostasis. Physical activity is comprised of intentional exercise and SPA. These are opposite ends of a continuum of physical activity intensity and structure. Non‐goal‐oriented behaviors, such as fidgeting, standing, and ambulating, constitute SPA in humans, and reflect a propensity for activity separate from intentional activity, such as high‐intensity voluntary exercise. In animals, SPA is activity not influenced by rewards such as food or a running wheel. Spontaneous physical activity in humans and animals burns calories and could theoretically be manipulated pharmacologically to expend calories and protect against obesity. The DRN neurons receive orexin inputs, and project heavily onto cortical and subcortical areas involved in movement, feeding and energy expenditure (EE). This review discusses the function of hypothalamic orexin in energy‐homeostasis, the interaction with DRN serotonin neurons, and the role of this orexin‐serotonin axis in regulating food intake, SPA, and EE. In addition, we discuss possible brain areas involved in orexin–serotonin cross‐talk; the role of serotonin receptors, transporters and uptake‐inhibitors in the pathogenesis and treatment of obesity; animal models of obesity with impaired serotonin‐function; single‐nucleotide polymorphisms in the serotonin system and obesity; and future directions in the orexin–serotonin field. This article is categorized under:Metabolic Diseases > Molecular and Cellular Physiology
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Affiliation(s)
- Vijayakumar Mavanji
- Research Service, Minneapolis VA Health Care System, Minneapolis, Minnesota, USA
| | - Brianna Pomonis
- Research Service, Minneapolis VA Health Care System, Minneapolis, Minnesota, USA
| | - Catherine M Kotz
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, USA.,Geriatric Research Education and Clinical Center, Minneapolis VA Health Care System, Minneapolis, Minnesota, USA
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9
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Tan Y, Hang F, Liu ZW, Stoiljkovic M, Wu M, Tu Y, Han W, Lee AM, Kelley C, Hajós M, Lu L, de Lecea L, De Araujo I, Picciotto MR, Horvath TL, Gao XB. Impaired hypocretin/orexin system alters responses to salient stimuli in obese male mice. J Clin Invest 2021; 130:4985-4998. [PMID: 32516139 DOI: 10.1172/jci130889] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 06/03/2020] [Indexed: 12/27/2022] Open
Abstract
The brain has evolved in an environment where food sources are scarce, and foraging for food is one of the major challenges for survival of the individual and species. Basic and clinical studies show that obesity or overnutrition leads to overwhelming changes in the brain in animals and humans. However, the exact mechanisms underlying the consequences of excessive energy intake are not well understood. Neurons expressing the neuropeptide hypocretin/orexin (Hcrt) in the lateral/perifonical hypothalamus (LH) are critical for homeostatic regulation, reward seeking, stress response, and cognitive functions. In this study, we examined adaptations in Hcrt cells regulating behavioral responses to salient stimuli in diet-induced obese mice. Our results demonstrated changes in primary cilia, synaptic transmission and plasticity, cellular responses to neurotransmitters necessary for reward seeking, and stress responses in Hcrt neurons from obese mice. Activities of neuronal networks in the LH and hippocampus were impaired as a result of decreased hypocretinergic function. The weakened Hcrt system decreased reward seeking while altering responses to acute stress (stress-coping strategy), which were reversed by selectively activating Hcrt cells with chemogenetics. Taken together, our data suggest that a deficiency in Hcrt signaling may be a common cause of behavioral changes (such as lowered arousal, weakened reward seeking, and altered stress response) in obese animals.
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Affiliation(s)
- Ying Tan
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.,Department of Neurosurgery, Guizhou Provincial People's Hospital, Guiyang, Guizhou, China
| | - Fu Hang
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.,Guangxi Reproductive Medical Research Center, First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, China
| | - Zhong-Wu Liu
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Milan Stoiljkovic
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Mingxing Wu
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.,Department of Ophthalmology, Second Affiliate Hospital of Chongqing Medical University, Chongqing, China
| | - Yue Tu
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA.,Department of Traditional Chinese Medicine Health Preservation, Second Clinic Medical School, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Wenfei Han
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Angela M Lee
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Craig Kelley
- Joint Biomedical Engineering Program, SUNY Downstate and NYU Tandon, Brooklyn, New York, USA
| | - Mihály Hajós
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Lingeng Lu
- Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, Connecticut, USA
| | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, California, USA
| | - Ivan De Araujo
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Marina R Picciotto
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Tamas L Horvath
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Xiao-Bing Gao
- Department of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
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10
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Synchronous neuronal interactions in rat hypothalamic culture: a novel model for the study of network dynamics in metabolic disorders. Exp Brain Res 2021; 239:755-764. [PMID: 33388905 DOI: 10.1007/s00221-020-05977-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 10/29/2020] [Indexed: 12/23/2022]
Abstract
Synchronous neural activity is a feature of normal brain function, and altered synchronization is observed in several neurological diseases. Dysfunction in hypothalamic pathways leads to obesity, suggesting that hypothalamic neural synchrony is critical for energy homeostasis. The lateral hypothalamic orexin neurons are extensively interconnected with other brain structures and are important for energy balance. Earlier studies show that rats with higher orexin sensitivity are obesity resistant. Similarly, topiramate, an anti-epileptic drug, has been shown to reduce weight in humans. Since orexin enhances neuronal excitation, we hypothesized that obesity-resistant rats with higher orexin sensitivity may exhibit enhanced hypothalamic synchronization. We further hypothesized that anti-obesity agents such as orexin and topiramate will enhance hypothalamic synchronization. To test this, we examined neural synchronicity in primary embryonic hypothalamic cell cultures, obtained from embryonic day 18 (E18) obesity-susceptible Sprague-Dawley (SD) and obesity-resistant rats. Hypothalamic tissue was cultured in multielectrode array (MEA), and recordings were performed twice weekly, from 4th to 32nd day in vitro (DIV). Next, we tested the effects of orexin and topiramate application on neural synchronicity of hypothalamic cultures obtained from SD rat embryos. Signals were analyzed for synchronization using cross correlation. Our results showed that (1) obesity-resistant hypothalamus exhibits significantly higher synchronization compared to obesity-sensitive hypothalamus; and (2) orexin and topiramate enhance hypothalamic synchronization. These results support that enhanced orexin sensitivity is associated with greater neural synchronization, and that anti-obesity treatments enhance network synchronization, thus constrain variability in hypothalamic output signals, to extrahypothalamic structures involved in energy homeostasis.
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Natsubori A, Tsunematsu T, Karashima A, Imamura H, Kabe N, Trevisiol A, Hirrlinger J, Kodama T, Sanagi T, Masamoto K, Takata N, Nave KA, Matsui K, Tanaka KF, Honda M. Intracellular ATP levels in mouse cortical excitatory neurons varies with sleep-wake states. Commun Biol 2020; 3:491. [PMID: 32895482 PMCID: PMC7477120 DOI: 10.1038/s42003-020-01215-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 07/31/2020] [Indexed: 02/06/2023] Open
Abstract
Whilst the brain is assumed to exert homeostatic functions to keep the cellular energy status constant under physiological conditions, this has not been experimentally proven. Here, we conducted in vivo optical recordings of intracellular concentration of adenosine 5'-triphosphate (ATP), the major cellular energy metabolite, using a genetically encoded sensor in the mouse brain. We demonstrate that intracellular ATP levels in cortical excitatory neurons fluctuate in a cortex-wide manner depending on the sleep-wake states, correlating with arousal. Interestingly, ATP levels profoundly decreased during rapid eye movement sleep, suggesting a negative energy balance in neurons despite a simultaneous increase in cerebral hemodynamics for energy supply. The reduction in intracellular ATP was also observed in response to local electrical stimulation for neuronal activation, whereas the hemodynamics were simultaneously enhanced. These observations indicate that cerebral energy metabolism may not always meet neuronal energy demands, consequently resulting in physiological fluctuations of intracellular ATP levels in neurons.
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Affiliation(s)
- Akiyo Natsubori
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan.
| | - Tomomi Tsunematsu
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8578, Japan
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan
- Advanced Interdisciplinary Research Division, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Akihiro Karashima
- Tohoku Institute of Technology, 35-1, Yagiyama Kasumi-cho, Taihaku-ku, Sendai, 982-8577, Japan
| | - Hiromi Imamura
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Naoya Kabe
- Neural Prosthesis Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan
| | - Andrea Trevisiol
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany
| | - Johannes Hirrlinger
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Liebigstrasse 27, 04103, Leipzig, Germany
| | - Tohru Kodama
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan
| | - Tomomi Sanagi
- Advanced Interdisciplinary Research Division, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Kazuto Masamoto
- Department of Mechanical and Intelligent Systems Engineering, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan
| | - Norio Takata
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Gottingen, 37075, Germany
| | - Ko Matsui
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8578, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Makoto Honda
- Sleep Disorders Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan
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Melnick I, Krishtal OA, Colmers WF. Integration of energy homeostasis and stress by parvocellular neurons in rat hypothalamic paraventricular nucleus. J Physiol 2020; 598:1073-1092. [PMID: 31952096 DOI: 10.1113/jp279387] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/16/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Central regulation of energy homeostasis and stress are believed to be reciprocally regulated, i.e. excessive food intake suppresses, while prolonged hunger exacerbates, stress responses in vivo. This relationship may be mediated by neuroendocrine parvocellular corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus that receive both stress- and feeding-related input. We find that hunger strongly and selectively potentiates, while re-feeding suppresses, a cellular analogue of a stress response induced by acute glucopenia in CRH neurons in rat hypothalamic slices. Neuronal activation in response to glucopenia was mediated synaptically, via the relative enhancement of glutamate over GABA input. These results illustrate how acute stress responses may be initiated in vivo and show that it is reciprocally integrated with energy balance via local hypothalamic mechanisms acting at the level of CRH neurons and their afferent terminals. ABSTRACT Increased food intake is a common response to help cope with stress, implying the existence of a previously postulated but imperfectly understood, inverse relationship between the regulation of feeding and stress. We have identified components of the neural circuitry that can integrate these homeostatic responses. Prior fasting (∼24 h) potentiates, and re-feeding suppresses, excitatory responses to acute glucopenia in about half of the corticotropin releasing hormone (CRH)-expressing, putatively neurosecretory, stress-related neurons in the paraventricular nucleus of the hypothalamus studied. Glucoprivation stress ex vivo resulted from a preferential relative increase in excitatory (glutamatergic) over inhibitory (GABAergic) inputs. Putative preautonomic cells were less sensitive to fasting, and showed a predominant inhibition to acute glucopenia. We conclude that hunger may sensitize hypothalamic stress responses by acting via local mechanisms, at the level of CRH neurons and their presynaptic inputs. Those mechanisms involve neither presynaptic ATP-sensitive potassium channels nor postsynaptic ATP levels.
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Affiliation(s)
- Igor Melnick
- Bogomoletz Institute of Physiology, Bogomoletz str 4, Kiev, 01024, Ukraine
| | - Oleg A Krishtal
- Bogomoletz Institute of Physiology, Bogomoletz str 4, Kiev, 01024, Ukraine
| | - William F Colmers
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7
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Bian H, Huang L, Li B, Hu Q, Liang X, Tang J, Zhang JH. The arousal effect of hyperbaric oxygen through orexin/hypocretin an upregulation on ketamine/ethanol-induced unconsciousness in male rats. J Neurosci Res 2019; 98:201-211. [PMID: 30895638 DOI: 10.1002/jnr.24414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 02/01/2019] [Accepted: 03/01/2019] [Indexed: 01/18/2023]
Abstract
Approaches that facilitate the recovery from coma would have enormous impacts on patient outcomes and medical economics. Orexin-producing neurons release orexins (also known as hypocretins) energy-dependently to maintain arousal. Hyperbaric oxygen (HBO) could increase ATP levels by preserving mitochondrial function. We investigated, for the first time, the arousal effects of HBO and orexins mechanisms in a rat model of unconsciousness induced by ketamine or ethanol. A total of 120 Sprague-Dawley male rats were used in this study. Unconsciousness was induced either by intraperitoneal injection of ketamine or ethanol. The HBO treatment (100% O2 at 3 ATA) was administered immediately after unconsciousness induction for 1 hr. SB334867, orexin-1 receptor (OX1R) inhibitor, or JNJ10397049, orexin-2 receptor (OX2R) inhibitor was administered 30 min intraperitoneally before unconsciousness induction. Loss of righting reflex test (LORR) and Garcia test were used to evaluate the unconsciousness duration and neurological deficits after recovering from unconsciousness, respectively. Enzyme-linked immunosorbent assay was used to measure brain tissue ATP and orexin A levels. Ketamine or ethanol injection resulted in LORR immediately and neurological deficits 6 hr after unconsciousness induction. HBO treatment significantly reduced the LORR duration, improved Garcia scores and unregulated ATP and orexin A levels in the brain tissue. Administration of OX1R inhibitor or OX2 R inhibitor abolished arousal and neurological benefits of HBO. In conclusion, HBO exerted arousal-promoting effects on unconscious rats induced by ketamine or ethanol. The underlying mechanism was via, at least in part, ATP/orexin A upregulation. HBO may be a practical clinical approach to accelerate unconsciousness recovery in patients.
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Affiliation(s)
- Hetao Bian
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California.,Department of Neurology, Jining First People's Hospital, Jining, China.,Mental Health Center of Wuhan University Renmin Hospital, Wuhan, China
| | - Lei Huang
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California.,Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, California
| | - Bo Li
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California
| | - Qin Hu
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California
| | - Xiping Liang
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California
| | - Jiping Tang
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California
| | - John H Zhang
- Division of Physiology, Department of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California.,Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, California.,Department of Anesthesiology, School of Medicine, Loma Linda University, Loma Linda, California
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Briggs C, Bowes SC, Semba K, Hirasawa M. Sleep deprivation-induced pre- and postsynaptic modulation of orexin neurons. Neuropharmacology 2018; 154:50-60. [PMID: 30586566 DOI: 10.1016/j.neuropharm.2018.12.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 12/20/2018] [Accepted: 12/21/2018] [Indexed: 10/27/2022]
Abstract
Sleep/wake states are controlled by sleep- and wake-promoting systems, and transitions between states are thought to be regulated by their reciprocal inhibition and homeostatic sleep need. Orexin neurons are known to promote wake maintenance and stabilize the sleep/wake switch. Thus, we asked whether orexin neurons are modulated by homeostatic sleep need. Rats were sleep deprived or left undisturbed to rest for 6 h, then acute brain slices were generated for patch clamp recordings. We found that sleep deprivation increased firing and reduced spike frequency adaptation in response to excitatory drive in orexin neurons. These changes were specific to D-type orexin neurons which, unlike H-type orexin neurons, lack A-type current. In D-type orexin neurons, sleep deprivation decreased afterhyperpolarizing potential, which was associated with increased gain, measured as the slope of the input-output relationship. These effects were mimicked by inhibition of SK channels. Furthermore, sleep deprivation resulted in presynaptic inhibition of excitatory inputs to both D-type and H-type orexin neurons, which preferentially affected sparse synaptic inputs while sparing high frequency synaptic activities. Taken together, our results indicate that sleep deprivation modulates the gain control and synaptic gating in orexin neurons. These pre-and postsynaptic changes would tune orexin neurons to strong wake-promoting excitatory signals, while dampening weak synaptic inputs to allow transition to sleep in the absence of such strong signals. These mechanisms are consistent with a role of orexin neurons not only as a key state stabilizer, but also as a homeostatic wake integrator in the sleep/wake switch. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.
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Affiliation(s)
- Chantalle Briggs
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, 300 Prince Philip Drive, St. John's, NL, A1B 3V6, Canada; Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, 5850 College Street, Halifax, NS, B3H 4R2, Canada
| | - Sherri C Bowes
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, 300 Prince Philip Drive, St. John's, NL, A1B 3V6, Canada
| | - Kazue Semba
- Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, 5850 College Street, Halifax, NS, B3H 4R2, Canada; Department of Psychiatry, Faculty of Medicine, Dalhousie University, 5909 Veterans' Memorial Lane, Halifax, NS, B3H 2E2, Canada; Department of Psychology and Neuroscience, Faculty of Science, Dalhousie University, 1355 Oxford Street, Halifax, NS, B3H 4R2, Canada
| | - Michiru Hirasawa
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, 300 Prince Philip Drive, St. John's, NL, A1B 3V6, Canada.
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15
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Arrigoni E, Chee MJS, Fuller PM. To eat or to sleep: That is a lateral hypothalamic question. Neuropharmacology 2018; 154:34-49. [PMID: 30503993 DOI: 10.1016/j.neuropharm.2018.11.017] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/08/2018] [Accepted: 11/12/2018] [Indexed: 12/15/2022]
Abstract
The lateral hypothalamus (LH) is a functionally and anatomically complex brain region that is involved in the regulation of many behavioral and physiological processes including feeding, arousal, energy balance, stress, reward and motivated behaviors, pain perception, body temperature regulation, digestive functions and blood pressure. Despite noteworthy experimental efforts over the past decades, the circuit, cellular and synaptic bases by which these different processes are regulated by the LH remains incompletely understood. This knowledge gap links in large part to the high cellular heterogeneity of the LH. Fortunately, the rapid evolution of newer genetic and electrophysiological tools is now permitting the selective manipulation, typically genetically-driven, of discrete LH cell populations. This, in turn, permits not only assignment of function to discrete cell groups, but also reveals that considerable synergistic and antagonistic interactions exist between key LH cell populations that regulate feeding and arousal. For example, we now know that while LH melanin-concentrating hormone (MCH) and orexin/hypocretin neurons both function as sensors of the internal metabolic environment, their roles regulating sleep and arousal are actually opposing. Additional studies have uncovered similarly important roles for subpopulations of LH GABAergic cells in the regulation of both feeding and arousal. Herein we review the role of LH MCH, orexin/hypocretin and GABAergic cell populations in the regulation of energy homeostasis (including feeding) and sleep-wake and discuss how these three cell populations, and their subpopulations, may interact to optimize and coordinate metabolism, sleep and arousal. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.
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Affiliation(s)
- Elda Arrigoni
- Department of Neurology, Beth Israel Deaconess Medical Center, Division of Sleep Medicine, Harvard Medical School, Boston, MA, 02215, USA.
| | - Melissa J S Chee
- Department of Neuroscience, Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Patrick M Fuller
- Department of Neurology, Beth Israel Deaconess Medical Center, Division of Sleep Medicine, Harvard Medical School, Boston, MA, 02215, USA
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16
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Goforth PB, Myers MG. Roles for Orexin/Hypocretin in the Control of Energy Balance and Metabolism. Curr Top Behav Neurosci 2017; 33:137-156. [PMID: 27909992 DOI: 10.1007/7854_2016_51] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The neuropeptide hypocretin is also commonly referred to as orexin, since its orexigenic action was recognized early. Orexin/hypocretin (OX) neurons project widely throughout the brain and the physiologic and behavioral functions of OX are much more complex than initially conceived based upon the stimulation of feeding. OX most notably controls functions relevant to attention, alertness, and motivation. OX also plays multiple crucial roles in the control of food intake, metabolism, and overall energy balance in mammals. OX signaling not only promotes food-seeking behavior upon short-term fasting to increase food intake and defend body weight, but, conversely, OX signaling also supports energy expenditure to protect against obesity. Furthermore, OX modulates the autonomic nervous system to control glucose metabolism, including during the response to hypoglycemia. Consistently, a variety of nutritional cues (including the hormones leptin and ghrelin) and metabolites (e.g., glucose, amino acids) control OX neurons. In this chapter, we review the control of OX neurons by nutritional/metabolic cues, along with our current understanding of the mechanisms by which OX and OX neurons contribute to the control of energy balance and metabolism.
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Affiliation(s)
- Paulette B Goforth
- Department of Pharmacology, University of Michigan, 1000 Wall St, 5131 Brehm Tower, Ann Arbor, MI, 48105, USA
| | - Martin G Myers
- Departments of Internal Medicine, and Molecular and Integrative Physiology, University of Michigan, 1000 Wall St, 6317 Brehm Tower, Ann Arbor, MI, 48105, USA.
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17
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Santoro A, Campolo M, Liu C, Sesaki H, Meli R, Liu ZW, Kim JD, Diano S. DRP1 Suppresses Leptin and Glucose Sensing of POMC Neurons. Cell Metab 2017; 25:647-660. [PMID: 28190775 PMCID: PMC5366041 DOI: 10.1016/j.cmet.2017.01.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Revised: 11/30/2016] [Accepted: 01/10/2017] [Indexed: 11/24/2022]
Abstract
Hypothalamic pro-opiomelanocortin (POMC) neurons regulate energy and glucose metabolism. Intracellular mechanisms that enable these neurons to respond to changes in metabolic environment are ill defined. Here we show reduced expression of activated dynamin-related protein (pDRP1), a mitochondrial fission regulator, in POMC neurons of fed mice. These POMC neurons displayed increased mitochondrial size and aspect ratio compared to POMC neurons of fasted animals. Inducible deletion of DRP1 of mature POMC neurons (Drp1fl/fl-POMC-cre:ERT2) resulted in improved leptin sensitivity and glucose responsiveness. In Drp1fl/fl-POMC-cre:ERT2 mice, POMC neurons showed increased mitochondrial size, ROS production, and neuronal activation with increased expression of Kcnj11 mRNA regulated by peroxisome proliferator-activated receptor (PPAR). Furthermore, deletion of DRP1 enhanced the glucoprivic stimulus in these neurons, causing their stronger inhibition and a greater activation of counter-regulatory responses to hypoglycemia that were PPAR dependent. Together, these data unmasked a role for mitochondrial fission in leptin sensitivity and glucose sensing of POMC neurons.
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Affiliation(s)
- Anna Santoro
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Michela Campolo
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Chen Liu
- Department of Internal Medicine, Division of Hypothalamic Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Rosaria Meli
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Pharmacy, University of Naples "Federico II," 80131 Napoli, Italy
| | - Zhong-Wu Liu
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Jung Dae Kim
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Sabrina Diano
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA; Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
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UCP2 Regulates Mitochondrial Fission and Ventromedial Nucleus Control of Glucose Responsiveness. Cell 2016; 164:872-83. [PMID: 26919426 DOI: 10.1016/j.cell.2016.02.010] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/08/2015] [Accepted: 02/03/2016] [Indexed: 01/21/2023]
Abstract
The ventromedial nucleus of the hypothalamus (VMH) plays a critical role in regulating systemic glucose homeostasis. How neurons in this brain area adapt to the changing metabolic environment to regulate circulating glucose levels is ill defined. Here, we show that glucose load results in mitochondrial fission and reduced reactive oxygen species in VMH neurons mediated by dynamin-related peptide 1 (DRP1) under the control of uncoupling protein 2 (UCP2). Probed by genetic manipulations and chemical-genetic control of VMH neuronal circuitry, we unmasked that this mitochondrial adaptation determines the size of the pool of glucose-excited neurons in the VMH and that this process regulates systemic glucose homeostasis. Thus, our data unmasked a critical cellular biological process controlled by mitochondrial dynamics in VMH regulation of systemic glucose homeostasis.
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Gao XB, Hermes G. Neural plasticity in hypocretin neurons: the basis of hypocretinergic regulation of physiological and behavioral functions in animals. Front Syst Neurosci 2015; 9:142. [PMID: 26539086 PMCID: PMC4612503 DOI: 10.3389/fnsys.2015.00142] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 10/02/2015] [Indexed: 12/22/2022] Open
Abstract
The neuronal system that resides in the perifornical and lateral hypothalamus (Pf/LH) and synthesizes the neuropeptide hypocretin/orexin participates in critical brain functions across species from fish to human. The hypocretin system regulates neural activity responsible for daily functions (such as sleep/wake homeostasis, energy balance, appetite, etc.) and long-term behavioral changes (such as reward seeking and addiction, stress response, etc.) in animals. The most recent evidence suggests that the hypocretin system undergoes substantial plastic changes in response to both daily fluctuations (such as food intake and sleep-wake regulation) and long-term changes (such as cocaine seeking) in neuronal activity in the brain. The understanding of these changes in the hypocretin system is essential in addressing the role of the hypocretin system in normal physiological functions and pathological conditions in animals and humans. In this review, the evidence demonstrating that neural plasticity occurs in hypocretin-containing neurons in the Pf/LH will be presented and possible physiological, behavioral, and mental health implications of these findings will be discussed.
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Affiliation(s)
- Xiao-Bing Gao
- Section of Comparative Medicine, Yale University School of Medicine New Haven, CT, USA ; Program on Integrative Cell Signaling and Neurobiology of Metabolism (ICSNM), Yale University School of Medicine New Haven, CT, USA
| | - Gretchen Hermes
- Department of Psychiatry, Yale University School of Medicine New Haven, CT, USA
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Heat and oxidative stress alter the expression of orexin and its related receptors in avian liver cells. Comp Biochem Physiol A Mol Integr Physiol 2015; 191:18-24. [PMID: 26419694 DOI: 10.1016/j.cbpa.2015.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 07/07/2015] [Accepted: 08/19/2015] [Indexed: 10/23/2022]
Abstract
Orexins (A and B) or hypocretins (1 and 2) are hypothalamic orexigenic neuropeptides that are involved in the regulation of several physiological processes in mammals. Recently, orexin has been shown to activate the hypothalamic-pituitary-adrenal (HPA) stress axis and emerging evidences identify it as a stress modulator in mammals. However, the regulation of orexin system by stress itself remains unclear. Here, we investigate the effects of heat, 4-Hydroxynonenal (4-HNE) and hydrogen peroxide (H2O2) stress on the hepatic expression of orexin (ORX) and its related receptors (ORXR1/2) in avian species. Using in vivo and in vitro models, we found that heat stress significantly down-regulated ORX and ORXR1/2 mRNA and protein abundances in quail liver and LMH cells. H2O2, however, decreased ORX protein and increased ORX mRNA levels in a dose dependent manner (P<0.05). The absence of correlation between orexin mRNA and protein levels suggests that H2O2 treatment modulates post-transcriptional mechanisms. 4-HNE had a biphasic effect on orexin system expression, with a significant up-regulation at low doses (10 and 20μM) and a significant down-regulation at a high dose (30μM). Taken together, our data indicated that hepatic orexin system could be a molecular signature in the heat and oxidative stress response.
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Acetylcholine Acts through Nicotinic Receptors to Enhance the Firing Rate of a Subset of Hypocretin Neurons in the Mouse Hypothalamus through Distinct Presynaptic and Postsynaptic Mechanisms .. eNeuro 2015; 2. [PMID: 26322330 PMCID: PMC4551500 DOI: 10.1523/eneuro.0052-14.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurons expressing the neuropeptide hypocretin regulate many behavioral functions, including sleep, motivation, and behaviors related to addiction. The ability of nicotine to stimulate nicotinic acetylcholine receptors (nAChRs) is essential for its addictive properties, but little is known about whether, and how, nicotine and the endogenous neurotransmitter acetylcholine affect hypocretin neurons. Hypocretin/orexin neurons regulate many behavioral functions, including addiction. Nicotine acts through nicotinic acetylcholine receptors (nAChRs) to alter firing rate of neurons throughout the brain, leading to addiction-related behaviors. While nAChRs are expressed in the hypothalamus and cholinergic fibers project to this structure, it is unclear how acetylcholine modulates the activity of hypocretin neurons. In this study, we stimulated hypocretin neurons in mouse brain slices with ACh in the presence of atropine to dissect presynaptic and postsynaptic modulation of these neurons through nAChRs. Approximately one-third of tested hypocretin neurons responded to pressure application of ACh (1 mM) with an increase in firing frequency. Stimulation of postsynaptic nAChRs with ACh or nicotine resulted in a highly variable inward current in approximately one-third of hypocretin neurons. In contrast, ACh or nicotine (1 µM) reliably decreased the frequency of miniature EPSCs (mEPSCs). Antagonism of nAChRs with mecamylamine also suppressed mEPSC frequency, suggesting that an endogenous, tonic activation of presynaptic nAChRs might be required for maintaining functional mEPSC frequency. Antagonism of heteromeric (α4β2) or homomeric (α7) nAChRs alone suppressed mEPSCs to a lesser extent. Finally, blocking internal calcium release reduced the frequency of mEPSCs, occluding the suppressive effect of presynaptic ACh. Taken together, these data provide a mechanism by which phasic ACh release enhances the firing of a subset of hypocretin neurons through postsynaptic nAChRs, but disrupts tonic, presynaptic nAChR-mediated glutamatergic inputs to the overall population of hypocretin neurons, potentially enhancing the signal-to-noise ratio during the response of the nAChR-positive subset of neurons.
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Leptin acts via lateral hypothalamic area neurotensin neurons to inhibit orexin neurons by multiple GABA-independent mechanisms. J Neurosci 2014; 34:11405-15. [PMID: 25143620 DOI: 10.1523/jneurosci.5167-13.2014] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The adipocyte-derived hormone leptin modulates neural systems appropriately for the status of body energy stores. Leptin inhibits lateral hypothalamic area (LHA) orexin (OX; also known as hypocretin)-producing neurons, which control feeding, activity, and energy expenditure, among other parameters. Our previous results suggest that GABAergic LHA leptin receptor (LepRb)-containing and neurotensin (Nts)-containing (LepRb(Nts)) neurons lie in close apposition with OX neurons and control Ox mRNA expression. Here, we show that, similar to leptin, activation of LHA Nts neurons by the excitatory hM3Dq DREADD (designer receptor exclusively activated by designer drugs) hyperpolarizes membrane potential and suppresses action potential firing in OX neurons in mouse hypothalamic slices. Furthermore, ablation of LepRb from Nts neurons abrogated the leptin-mediated inhibition, demonstrating that LepRb(Nts) neurons mediate the inhibition of OX neurons by leptin. Leptin did not significantly enhance GABAA-mediated inhibitory synaptic transmission, and GABA receptor antagonists did not block leptin-mediated inhibition of OX neuron activity. Rather, leptin diminished the frequency of spontaneous EPSCs onto OX neurons. Furthermore, leptin indirectly activated an ATP-sensitive potassium (K(ATP)) channel in OX neurons, which was required for the hyperpolarization of OX neurons by leptin. Although Nts did not alter OX activity, galanin, which is coexpressed in LepRb(Nts) neurons, inhibited OX neurons, whereas the galanin receptor antagonist M40 (galanin-(1-12)-Pro3-(Ala-Leu)2-Ala amide) prevented the leptin-induced hyperpolarization of OX cells. These findings demonstrate that leptin indirectly inhibits OX neurons by acting on LHA LepRb(Nts) neurons to mediate two distinct GABA-independent mechanisms of inhibition: the presynaptic inhibition of excitatory neurotransmission and the opening of K(ATP) channels.
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Sheng Z, Santiago AM, Thomas MP, Routh VH. Metabolic regulation of lateral hypothalamic glucose-inhibited orexin neurons may influence midbrain reward neurocircuitry. Mol Cell Neurosci 2014; 62:30-41. [PMID: 25107627 PMCID: PMC6524643 DOI: 10.1016/j.mcn.2014.08.001] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/23/2014] [Accepted: 08/02/2014] [Indexed: 12/20/2022] Open
Abstract
Lateral hypothalamic area (LHA) orexin neurons modulate reward-based feeding by activating ventral tegmental area (VTA) dopamine (DA) neurons. We hypothesize that signals of peripheral energy status influence reward-based feeding by modulating the glucose sensitivity of LHA orexin glucose-inhibited (GI) neurons. This hypothesis was tested using electrophysiological recordings of LHA orexin-GI neurons in brain slices from 4 to 6week old male mice whose orexin neurons express green fluorescent protein (GFP) or putative VTA-DA neurons from C57Bl/6 mice. Low glucose directly activated ~60% of LHA orexin-GFP neurons in both whole cell and cell attached recordings. Leptin indirectly reduced and ghrelin directly enhanced the activation of LHA orexin-GI neurons by glucose decreases from 2.5 to 0.1mM by 53±12% (n=16, P<0.001) and 41±24% (n=8, P<0.05), respectively. GABA or neurotensin receptor blockade prevented leptin's effect on glucose sensitivity. Fasting increased activation of LHA orexin-GI neurons by decreased glucose, as would be predicted by these hormonal effects. We also evaluated putative VTA-DA neurons in a novel horizontal slice preparation containing the LHA and VTA. Decreased glucose increased the frequency of spontaneous excitatory post-synaptic currents (sEPSCs; 125 ± 40%, n=9, P<0.05) and action potentials (n=9; P<0.05) in 45% (9/20) of VTA DA neurons. sEPSCs were completely blocked by AMPA and NMDA glutamate receptor antagonists (CNQX 20 μM, n=4; APV 20μM, n=4; respectively), demonstrating that these sEPSCs were mediated by glutamatergic transmission onto VTA DA neurons. Orexin-1 but not 2 receptor antagonism with SB334867 (10μM; n=9) and TCS-OX2-29 (2μM; n=5), respectively, blocks the effects of decreased glucose on VTA DA neurons. Thus, decreased glucose increases orexin-dependent excitatory glutamate neurotransmission onto VTA DA neurons. These data suggest that the glucose sensitivity of LHA orexin-GI neurons links metabolic state and reward-based feeding.
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Affiliation(s)
- Zhenyu Sheng
- New Jersey Med. Sch., Rutgers University, Newark, NJ 07103, United States
| | - Ammy M Santiago
- New Jersey Med. Sch., Rutgers University, Newark, NJ 07103, United States
| | - Mark P Thomas
- Univ. Northern Colorado, Greeley, CO 80639, United States
| | - Vanessa H Routh
- New Jersey Med. Sch., Rutgers University, Newark, NJ 07103, United States.
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Landry JP, Hawkins C, Wiebe S, Balaban E, Pompeiano M. Opposing effects of hypoxia on catecholaminergic locus coeruleus and hypocretin/orexin neurons in chick embryos. Dev Neurobiol 2014; 74:1030-7. [PMID: 24753448 DOI: 10.1002/dneu.22182] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/06/2014] [Accepted: 04/14/2014] [Indexed: 02/01/2023]
Abstract
Terrestrial vertebrate embryos face a risk of low oxygen availability (hypoxia) that is especially great during their transition to air-breathing. To better understand how fetal brains respond to hypoxia, we examined the effects of low oxygen availability on brain activity in late-stage chick embryos (day 18 out of a 21-day incubation period). Using cFos protein expression as a marker for neuronal activity, we focused on two specific, immunohistochemically identified cell groups known to play an important role in regulating adult brain states (sleep and waking): the noradrenergic neurons of the Locus Coeruleus (NA-LC), and the Hypocretin/Orexin (H/O) neurons of the hypothalamus. cFos expression was also examined in the Pallium (the avian analog of the cerebral cortex). In adult mammalian brains, cFos expression changes in a coordinated way in these areas. In chick embryos, oxygen deprivation simultaneously activated NA-LC while deactivating H/O-producing neurons; it also increased cFos expression in the Pallium. Activity in one pallial primary sensory area was significantly related to NA-LC activity. These data reveal that at least some of the same neural systems involved in brain-state control in adults may play a central role in orchestrating prenatal hypoxic responses, and that these circuits may show different patterns of coordination than seen in adults.
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Affiliation(s)
- Jeremy P Landry
- Department of Psychology, McGill University, Montreal, Quebec, Canada, H3A 1B1
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Abstract
The basic elements of animal behavior that are critical to survival include energy, arousal, and motivation: Energy intake and expenditure are fundamental to all organisms for the performance of any type of function; according to the Yerkes-Dodson law, an optimal level of arousal is required for animals to perform normal functions; and motivation is critical to goal-oriented behaviors in higher animals. The brain is the primary organ that controls these elements and, through evolution, has developed specialized structures to accomplish this task. The orexin/hypocretin system in the perifornical/lateral hypothalamus, which was discovered 15 years ago, is one such specialized area. This review summarizes a fast-growing body of evidence discerning how the orexin/hypocretin system integrates internal and external cues to regulate energy intake that can then be used to generate sufficient arousal for animals to perform innate and goal-oriented behaviors.
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Affiliation(s)
- Xiao-Bing Gao
- Yale Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, Connecticut 06520; ,
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Dietrich MO, Liu ZW, Horvath TL. Mitochondrial dynamics controlled by mitofusins regulate Agrp neuronal activity and diet-induced obesity. Cell 2013; 155:188-99. [PMID: 24074868 PMCID: PMC4142434 DOI: 10.1016/j.cell.2013.09.004] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 07/11/2013] [Accepted: 08/23/2013] [Indexed: 12/11/2022]
Abstract
Mitochondria are key organelles in the maintenance of cellular energy metabolism and integrity. Here, we show that mitochondria number decrease but their size increase in orexigenic agouti-related protein (Agrp) neurons during the transition from fasted to fed to overfed state. These fusion-like dynamic changes were cell-type specific, as they occurred in the opposite direction in anorexigenic pro-opiomelanocortin (POMC) neurons. Interfering with mitochondrial fusion mechanisms in Agrp neurons by cell-selectively knocking down mitofusin 1 (Mfn1) or mitofusin 2 (Mfn2) resulted in altered mitochondria size and density in these cells. Deficiency in mitofusins impaired the electric activity of Agrp neurons during high-fat diet (HFD), an event reversed by cell-selective administration of ATP. Agrp-specific Mfn1 or Mfn2 knockout mice gained less weight when fed a HFD due to decreased fat mass. Overall, our data unmask an important role for mitochondrial dynamics governed by Mfn1 and Mfn2 in Agrp neurons in central regulation of whole-body energy metabolism.
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Affiliation(s)
- Marcelo O Dietrich
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS 90035, Brazil.
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Potdar S, Sheeba V. Lessons From Sleeping Flies: Insights fromDrosophila melanogasteron the Neuronal Circuitry and Importance of Sleep. J Neurogenet 2013; 27:23-42. [DOI: 10.3109/01677063.2013.791692] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Chase MH. A unified survival theory of the functioning of the hypocretinergic system. J Appl Physiol (1985) 2013; 115:954-71. [PMID: 23640599 DOI: 10.1152/japplphysiol.00700.2012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This article advances the theory that the hypocretinergic (orexinergic) system initiates, coordinates, and maintains survival behaviors and survival-related processes (i.e., the Unified Survival Theory of the Functioning of the Hypocretinergic System or "Unified Hypocretinergic Survival Theory"). A priori presumptive support for the Unified Hypocretinergic Survival Theory emanates from the fact that neurons that contain hypocretin are located in the key executive central nervous system (CNS) site, the lateral hypothalamus, that for decades has been well-documented to govern core survival behaviors such as fight, flight, and food consumption. In addition, the hypocretinergic system exhibits the requisite morphological and electrophysiological capabilities to control survival behaviors and related processes. Complementary behavioral data demonstrate that all facets of "survival" are coordinated by the hypocretinergic system and that hypocretinergic directives are not promulgated except during survival behaviors. Importantly, it has been shown that survival behaviors are selectively impacted when the hypocretinergic system is impaired or rendered nonfunctional, whereas other behaviors are relatively unaffected. The Unified Hypocretinergic Survival Theory resolves the disparate, perplexing, and often paradoxical-appearing results of previous studies; it also provides a foundation for future hypothesis-driven basic science and clinical explorations of the hypocretinergic system.
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Affiliation(s)
- Michael H Chase
- WebSciences International, Veterans Affairs-Greater Los Angeles Healthcare System, University of California, Los Angeles School of Medicine, Los Angeles, California
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Burdakov D, Karnani MM, Gonzalez A. Lateral hypothalamus as a sensor-regulator in respiratory and metabolic control. Physiol Behav 2013; 121:117-24. [PMID: 23562864 DOI: 10.1016/j.physbeh.2013.03.023] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 02/25/2013] [Accepted: 03/06/2013] [Indexed: 02/04/2023]
Abstract
Physiological fluctuations in the levels of hormones, nutrients, and gasses are sensed in parallel by interacting control systems distributed throughout the brain and body. We discuss the logic of this arrangement and the definitions of "sensing"; and then focus on lateral hypothalamic (LH) control of energy balance and respiration. LH neurons control diverse behavioral and autonomic processes by projecting throughout the neuraxis. Three recently characterized types of LH cells are discussed here. LH orexin/hypocretin (ORX) neurons fire predominantly during wakefulness and are thought to promote reward-seeking, arousal, obesity resistance, and adaptive thermogenesis. Bidirectional control of ORX cells by extracellular macronutrients may add a new regulatory loop to these processes. ORX neurons also stimulate breathing and are activated by acid/CO2in vivo and in vitro. LH melanin-concentrating hormone (MCH) neurons fire mostly during sleep, promote physical inactivity, weight gain, and may impair glucose tolerance. Reported stimulation of MCH neurons by glucose may thus modulate energy homeostasis. Leptin receptor (LepR) neurons of the LH are distinct from ORX and MCH neurons, and may suppress feeding and locomotion by signaling to the mesolimbic dopamine system and local ORX neurons. Integration within the ORX-MCH-LepR microcircuit is suggested by anatomical and behavioral data, but requires clarification with direct assays of functional connectivity. Further studies of how LH circuits counteract evolutionarily-relevant environmental fluctuations will provide key information about the logic and fragilities of brain controllers of healthy homeostasis.
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Affiliation(s)
- Denis Burdakov
- King's College London, MRC Center for Developmental Neurobiology, London, UK; MRC National Institute for Medical Research, London, UK.
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Woodside B, Budin R, Wellman MK, Abizaid A. Many mouths to feed: the control of food intake during lactation. Front Neuroendocrinol 2012; 33:301-14. [PMID: 23000403 DOI: 10.1016/j.yfrne.2012.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 09/04/2012] [Accepted: 09/05/2012] [Indexed: 01/07/2023]
Abstract
Providing nutrients to their developing young is perhaps the most energetically demanding task facing female mammals. In this paper we focus primarily on studies carried out in rats to describe the changes in the maternal brain that enable the dam to meet the energetic demands of her offspring. In rats, providing milk for their litter is associated with a dramatic increase in caloric intake, a reduction in energy expenditure and changes in the pattern of energy utilization as well as storage. These behavioral and physiological adaptations result, in part, from alterations in the central pathways controlling energy balance. Differences in circulating levels of metabolic hormones such as leptin, ghrelin and insulin as well as in responsiveness to these signals between lactating and nonlactating animals, contribute to the modifications in energy balance pathways seen postpartum. Suckling stimulation from the pups both directly, and through the hormonal state that it induces in the mother, plays a key role in facilitating these adaptations.
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Affiliation(s)
- Barbara Woodside
- Center for Studies in Behavioral Neurobiology/Groupe de recherches en neurobiologie comportementale, Concordia University, Montreal, Canada.
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Parsons MP, Belanger-Willoughby N, Linehan V, Hirasawa M. ATP-sensitive potassium channels mediate the thermosensory response of orexin neurons. J Physiol 2012; 590:4707-15. [PMID: 22802589 DOI: 10.1113/jphysiol.2012.236497] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
High body temperatures are generally associated with somnolence, lethargy, hypophagia and anhedonia. Orexin neurons have been suggested to play a role in such sickness behaviours due to their known functions in appetite, behavioural and autonomic activation. Furthermore, the activity of orexin neurons is inhibited by lipopolysaccharide that induces fever. However, the cellular mechanism(s) underlying this suppression of orexin neurons was unknown. We used patch-clamp recordings in acute rat brain slices to demonstrate that orexin neurons, including those projecting to the wake-promoting locus coeruleus, are inhibited by increasing the ambient temperature by a 2-4°C increment between 26 and 40°C. This effect was not mediated by conventional thermosensing mechanisms but instead involved the activation of ATP-sensitive potassium (KATP) channels. Since KATP channels can also sense energy substrate levels and cellular metabolism, our results suggest that orexin neurons can integrate the state of energy balance and body temperature, and adjust their output accordingly. Thus, the thermosensitivity of orexin neurons may be an important part of maintaining energy homeostasis during hyperthermia and fever.
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Affiliation(s)
- Matthew P Parsons
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, 300 Prince Philip Drive, St John's, NL, A1B 3V6, Canada
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Gao XB. Plasticity in neurons synthesizing wake/arousal promoting hormone hypocretin/orexin. VITAMINS AND HORMONES 2012; 89:35-59. [PMID: 22640607 DOI: 10.1016/b978-0-12-394623-2.00003-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The hypothalamus is a critical brain structure regulating physiological functions essential to the survival of individuals and species. One of the striking characteristics of this brain region is the abundance of nerve cells (neurons) expressing a great numbers of neurotransmitters and neuromodulators, among which are hormones released into the blood stream through brain neuroendocrinological routes. The neurons in the lateral hypothalamus take part in intra- and extrahypothalamic circuits controlling basic physiological functions essential for the well being of animal bodies (such as cardiovascular function, respiratory function, immune responses, etc.), animal behaviors required for the maintenance of the survival of individuals (food foraging, flight, fight, etc.) and species (reproductive function), and higher brain functions (learning and memory, mental state, etc.). Hypocretin (also called orexin) comprises of two neuropeptides exclusively synthesized by neurons in the perifornical/lateral hypothalamus. Although hypocretin/orexin was initially found to enhance food intake, it is now clear that the functions mediated by hypocretin/orexin are well beyond what were originally proposed. Specifically, hypocretin/orexin is a crucial promoter of wakefulness; deficiency in the hypocretin/orexin system leads to diseases and disorders such as narcolepsy. It is clear that neurons synthesizing hypocretin/orexin are consistently under regulation originating from various parts of the brain and that the status of activity in hypocretin/orexin neurons is closely related with the nutritional and behavioral state of animals. Therefore, the demand to make adaptive changes in hypocretin/orexin neurons to accommodate the changes in the external environment and behavioral state of animals is expected. The latest developments in the studies of plasticity in hypocretin/orexin neurons under the challenges from environmental and behavioral factors have dramatically shaped the understanding of the roles of hypocretin/orexin neurons in the maintenance of the survival of animals. More importantly, the studies of plasticity in hypocretin/orexin neurons as the consequence of physiological, behavioral, and environmental challenges may shed new insight on the understanding and treatment of sleep disorders (such as insomnia).
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Affiliation(s)
- Xiao-Bing Gao
- Section of Comparative Medicine, Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut, USA
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Abstract
The orexins/hypocretins are endogenous, modulatory and multifunctional neuropeptides with prominent influence on several physiological processes. The influence of orexins on energy expenditure is highlighted with focus on orexin action on individual components of energy expenditure. As orexin stabilizes and maintains normal states of arousal and the sleep/wake cycle, we also highlight orexin mediation of sleep and how sleep interacts with energy expenditure.
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Affiliation(s)
- Jennifer A Teske
- Department of Nutritional Sciences, University of Arizona and Southern Arizona VA Health Care System, Tucson, Arizona, USA
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Abstract
In this chapter, we give an overview of the current status of the role of orexins in feeding and energy homeostasis. Orexins, also known as hypocretins, initially were discovered in 1998 as hypothalamic regulators of food intake. A little later, their far more important function as regulators of sleep and arousal came to light. Despite their restricted distribution, orexin neurons have projections throughout the entire brain, with dense projections especially to the paraventricular nucleus of the thalamus, the arcuate nucleus of the hypothalamus, and the locus coeruleus and tuberomammillary nucleus. Its two receptors are orexin receptor 1 and orexin receptor 2. These receptors show a specific and localized distribution in a number of brain regions, and a variety of different actions has been demonstrated upon their binding. Our group showed that through the autonomic nervous system, the orexin system plays a key role in the control of glucose metabolism, but it has also been shown to stimulate sympathetic outflow, to increase body temperature, heart rate, blood pressure, and renal sympathetic nerve activity. The well-known effects of orexin on the control of food intake, arousal, and wakefulness appear to be more extensive than originally thought, with additional effects on the autonomic nervous system, that is, to increase body temperature and energy metabolism.
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Venner A, Karnani MM, Gonzalez JA, Jensen LT, Fugger L, Burdakov D. Orexin neurons as conditional glucosensors: paradoxical regulation of sugar sensing by intracellular fuels. J Physiol 2011; 589:5701-8. [PMID: 22005675 PMCID: PMC3249044 DOI: 10.1113/jphysiol.2011.217000] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 10/16/2011] [Indexed: 01/26/2023] Open
Abstract
Central orexin/hypocretin neurons promote wakefulness, feeding and reward-seeking, and control blood glucose levels by regulating sympathetic outflow to the periphery. Glucose itself directly suppresses the electrical activity and cytosolic calcium levels of orexin cells. Recent in vitro studies suggested that glucose inhibition of orexin cells may be mechanistically unusual, because it persists under conditions where glucose metabolism is unlikely. To investigate this further, and to clarify whether background metabolic state regulates orexin cell glucosensing, here we analysed glucose responses of orexin cells in mouse brain slices, in the presence and absence of metabolic inhibitors and physiological energy substrates. Consistent with their documented insensitivity to glucokinase inhibitors, the glucose responses of orexin cells persisted in the presence of the mitochondrial poison oligomycin or the glial toxin fluoroacetate. Unexpectedly, in the presence of oligomycin, the magnitude of the glucose response was significantly enhanced. In turn, 2-deoxyglucose, a non-metabolizable glucose analogue, elicited larger responses than glucose. Conversely, intracellular pyruvate dose-dependently suppressed the glucose responses, an effect that was blocked by oligomycin. The glucose responses were also suppressed by intracellular lactate and ATP. Our new data suggest that other energy substrates not only fail to mimic the orexin glucose response, but paradoxically suppress it in a metabolism-dependent manner. We propose that this unexpected intrinsic property of orexin cells allows them to act as 'conditional glucosensors' that preferentially respond to glucose during reduced background energy levels.
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Affiliation(s)
- Anne Venner
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK
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