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Haugg E, Borner J, Stalder G, Kübber‐Heiss A, Giroud S, Herwig A. Comparative transcriptomics of the garden dormouse hypothalamus during hibernation. FEBS Open Bio 2024; 14:241-257. [PMID: 37925593 PMCID: PMC10839406 DOI: 10.1002/2211-5463.13731] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/25/2023] [Accepted: 11/02/2023] [Indexed: 11/06/2023] Open
Abstract
Torpor or heterothermy is an energy-saving mechanism used by endotherms to overcome harsh environmental conditions. During winter, the garden dormouse (Eliomys quercinus) hibernates with multiday torpor bouts and body temperatures of a few degrees Celsius, interrupted by brief euthermic phases. This study investigates gene expression within the hypothalamus, the key brain area controlling energy balance, adding information on differential gene expression potentially relevant to orchestrate torpor. A de novo assembled transcriptome of the hypothalamus was generated from garden dormice hibernating under constant darkness without food and water at 5 °C. Samples were collected during early torpor, late torpor, and interbout arousal. During early torpor, 765 genes were differentially expressed as compared with interbout arousal. Twenty-seven pathways were over-represented, including pathways related to hemostasis, extracellular matrix organization, and signaling of small molecules. Only 82 genes were found to be differentially expressed between early and late torpor, and no pathways were over-represented. During late torpor, 924 genes were differentially expressed relative to interbout arousal. Despite the high number of differentially expressed genes, only 10 pathways were over-represented. Of these, eight were also observed to be over-represented when comparing early torpor and interbout arousal. Our results are largely consistent with previous findings in other heterotherms. The addition of a transcriptome of a novel species may help to identify species-specific and overarching torpor mechanisms through future species comparisons.
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Affiliation(s)
- Elena Haugg
- Institute of NeurobiologyUlm UniversityGermany
| | - Janus Borner
- Sackler Institute for Comparative GenomicsAmerican Museum of Natural HistoryNew YorkNYUSA
| | - Gabrielle Stalder
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
| | - Anna Kübber‐Heiss
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
| | - Sylvain Giroud
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
- Energetics Lab, Department of BiologyNorthern Michigan UniversityMarquetteMIUSA
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2
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Yamaguchi H, Murphy KR, Fukatsu N, Sato K, Yamanaka A, de Lecea L. Dorsomedial and preoptic hypothalamic circuits control torpor. Curr Biol 2023; 33:5381-5389.e4. [PMID: 37992720 DOI: 10.1016/j.cub.2023.10.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 09/25/2023] [Accepted: 10/31/2023] [Indexed: 11/24/2023]
Abstract
Endotherms can survive low temperatures and food shortage by actively entering a hypometabolic state known as torpor. Although the decrease in metabolic rate and body temperature (Tb) during torpor is controlled by the brain, the specific neural circuits underlying these processes have not been comprehensively elucidated. In this study, we identify the neural circuits involved in torpor regulation by combining whole-brain mapping of torpor-activated neurons, cell-type-specific manipulation of neural activity, and viral tracing-based circuit mapping. We find that Trpm2-positive neurons in the preoptic area and Vgat-positive neurons in the dorsal medial hypothalamus are activated during torpor. Genetic silencing shows that the activity of either cell type is necessary to enter the torpor state. Finally, we show that these cells receive projections from the arcuate and suprachiasmatic nucleus and send projections to brain regions involved in thermoregulation. Our results demonstrate an essential role of hypothalamic neurons in the regulation of Tb and metabolic rate during torpor and identify critical nodes of the torpor regulatory network.
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Affiliation(s)
- Hiroshi Yamaguchi
- Department of Neural Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601, Japan; PRESTO, Japan Science and Technology Agency (JST), Tokyo, Japan.
| | - Keith R Murphy
- Department of Psychiatry and Behavioral Sciences, Stanford University, 1201 Welch Road, Stanford, CA 94305, USA
| | - Noriaki Fukatsu
- Department of System Biology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 464-8601, Japan; Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 464-8601, Japan
| | - Kazuhide Sato
- Institute for Advanced Research, Nagoya University, Nagoya, Aichi 466-8550, Japan
| | | | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University, 1201 Welch Road, Stanford, CA 94305, USA.
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3
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2022; 6:313. [PMID: 35087956 PMCID: PMC8764563 DOI: 10.12688/wellcomeopenres.17379.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2022] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to review the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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Affiliation(s)
- Michael Ambler
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Timna Hitrec
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Anthony Pickering
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
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4
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2021; 6:313. [DOI: 10.12688/wellcomeopenres.17379.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2021] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to take a critical view of the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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5
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Richardson RR, Groenen M, Liu M, Mountford SJ, Briddon SJ, Holliday ND, Thompson PE. Heterodimeric Analogues of the Potent Y1R Antagonist 1229U91, Lacking One of the Pharmacophoric C-Terminal Structures, Retain Potent Y1R Affinity and Show Improved Selectivity over Y4R. J Med Chem 2020; 63:5274-5286. [PMID: 32364733 DOI: 10.1021/acs.jmedchem.0c00027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The cyclic dimeric peptide 1229U91 (GR231118) has an unusual structure and displays potent, insurmountable antagonism of the Y1 receptor. To probe the structural basis for this activity, we have prepared ring size variants and heterodimeric compounds, identifying the specific residues underpinning the mechanism of 1229U91 binding. The homodimeric structure was shown to be dispensible, with analogues lacking key pharmacophoric residues in one dimer arm retaining high antagonist affinity. Compounds 11d-h also showed enhanced Y1R selectivity over Y4R compared to 1229U91.
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Affiliation(s)
- Rachel R Richardson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia.,Institute of Cell Signalling, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Marleen Groenen
- Institute of Cell Signalling, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Mengjie Liu
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Simon J Mountford
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Stephen J Briddon
- Institute of Cell Signalling, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Nicholas D Holliday
- Institute of Cell Signalling, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
| | - Philip E Thompson
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia
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6
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Regan MD, Flynn-Evans EE, Griko YV, Kilduff TS, Rittenberger JC, Ruskin KJ, Buck CL. Shallow metabolic depression and human spaceflight: a feasible first step. J Appl Physiol (1985) 2020; 128:637-647. [PMID: 31999524 DOI: 10.1152/japplphysiol.00725.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Synthetic torpor is an induced state of deep metabolic depression (MD) in an organism that does not naturally employ regulated and reversible MD. If applied to spaceflight crewmembers, this metabolic state may theoretically mitigate numerous biological and logistical challenges of human spaceflight. These benefits have been the focus of numerous recent articles where, invariably, they are discussed in the context of hypothetical deep MD states in which the metabolism of crewmembers is profoundly depressed relative to basal rates. However, inducing these deep MD states in humans, particularly humans aboard spacecraft, is currently impossible. Here, we discuss shallow MD as a feasible first step toward synthetic torpor during spaceflight and summarize perspectives following a recent NASA-hosted workshop. We discuss methods to safely induce shallow MD (e.g., sleep and slow wave enhancement via acoustic and photoperiod stimulation; moderate sedation via dexmedetomidine), which we define as an ~20% depression of metabolic rate relative to basal levels. We also discuss different modes of shallow MD application (e.g., habitual versus targeted, whereby shallow MD is induced routinely throughout a mission or only under certain circumstances, respectively) and different spaceflight scenarios that would benefit from its use. Finally, we propose a multistep development plan toward the application of synthetic torpor to human spaceflight, highlighting shallow MD's role. As space agencies develop missions to send humans further into space than ever before, shallow MD has the potential to confer health benefits for crewmembers, reduce demands on spacecraft capacities, and serve as a testbed for deeper MD technologies.
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Affiliation(s)
- Matthew D Regan
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin
| | - Erin E Flynn-Evans
- Fatigue Countermeasures Laboratory, Human Systems Integration Division, NASA Ames Research Center, Moffett Field, California
| | - Yuri V Griko
- Countermeasure Development Laboratory, Space Biosciences Division, NASA Ames Research Center, Moffett Field, California
| | - Thomas S Kilduff
- Biosciences Division, Center for Neuroscience, SRI International, Menlo Park, California
| | - Jon C Rittenberger
- Guthrie Robert Packer Hospital Emergency Medicine Program, Geisinger Commonwealth School of Medicine, Scranton, Pennsylvania
| | - Keith J Ruskin
- Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois
| | - C Loren Buck
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona
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7
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Abstract
Torpor is a peculiar mammalian behaviour, characterized by the active reduction of metabolic rate, followed by a drop in body temperature. To enter torpor, the activation of all thermogenic organs that could potentially defend body temperature must be prevented. Most of these organs, such as the brown adipose tissue, are controlled by the key thermoregulatory region of the Raphe Pallidus (RPa). Currently, it is not known which brain areas mediate the entrance into torpor. To identify these areas, the expression of the early gene c-Fos at torpor onset was assessed in different brain regions in mice injected with a retrograde tracer (Cholera Toxin subunit b, CTb) into the RPa region. The results show a network of hypothalamic neurons that are specifically activated at torpor onset and a direct torpor-specific projection from the Dorsomedial Hypothalamus to the RPa that could putatively mediate the suppression of thermogenesis during torpor.
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8
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Kiriyama K, Goto T, Yamamoto H, Ara T, Takahashi H, Jheng HF, Nomura W, Inoue H, Nakata R, Kawada T. Lactobacillus helveticus-MIKI-020 enhances hepatic FGF21 expression and decreases the core body temperature during sleep in mice. J Funct Foods 2019. [DOI: 10.1016/j.jff.2019.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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9
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Silvani A, Cerri M, Zoccoli G, Swoap SJ. Is Adenosine Action Common Ground for NREM Sleep, Torpor, and Other Hypometabolic States? Physiology (Bethesda) 2019; 33:182-196. [PMID: 29616880 DOI: 10.1152/physiol.00007.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This review compares two states that lower energy expenditure: non-rapid eye movement (NREM) sleep and torpor. Knowledge on mechanisms common to these states, and particularly on the role of adenosine in NREM sleep, may ultimately open the possibility of inducing a synthetic torpor-like state in humans for medical applications and long-term space travel. To achieve this goal, it will be important, in perspective, to extend the study to other hypometabolic states, which, unlike torpor, can also be experienced by humans.
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Affiliation(s)
- Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Matteo Cerri
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy.,National Institute of Nuclear Physics (INFN), Section of Bologna, Bologna , Italy
| | - Giovanna Zoccoli
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Steven J Swoap
- Department of Biology, Williams College , Williamstown, Massachusetts
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10
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Eltahan HM, Bahry MA, Yang H, Han G, Nguyen LTN, Ikeda H, Ali MN, Amber KA, Furuse M, Chowdhury VS. Central NPY-Y5 sub-receptor partially functions as a mediator of NPY-induced hypothermia and affords thermotolerance in heat-exposed fasted chicks. Physiol Rep 2018; 5. [PMID: 29208684 PMCID: PMC5727273 DOI: 10.14814/phy2.13511] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 12/26/2022] Open
Abstract
Exposure of chicks to a high ambient temperature (HT) has previously been shown to increase neuropeptide Y (NPY) mRNA expression in the brain. Furthermore, it was found that NPY has anti‐stress functions in heat‐exposed fasted chicks. The aim of the study was to reveal the role of central administration of NPY on thermotolerance ability and the induction of heat‐shock protein (HSP) and NPY sub‐receptors (NPYSRs) in fasted chicks with the contribution of plasma metabolite changes. Six‐ or seven‐day‐old chicks were centrally injected with 0 or 375 pmol of NPY and exposed to either HT (35 ± 1°C) or control thermoneutral temperature (CT: 30 ± 1°C) for 60 min while fasted. NPY reduced body temperature under both CT and HT. NPY enhanced the brain mRNA expression of HSP‐70 and ‐90, as well as of NPYSRs‐Y5, ‐Y6, and ‐Y7, but not ‐Y1, ‐Y2, and ‐Y4, under CT and HT. A coinjection of an NPYSR‐Y5 antagonist (CGP71683) and NPY (375 pmol) attenuated the NPY‐induced hypothermia. Furthermore, central NPY decreased plasma glucose and triacylglycerol under CT and HT and kept plasma corticosterone and epinephrine lower under HT. NPY increased plasma taurine and anserine concentrations. In conclusion, brain NPYSR‐Y5 partially afforded protective thermotolerance in heat‐exposed fasted chicks. The NPY‐mediated reduction in plasma glucose and stress hormone levels and the increase in free amino acids in plasma further suggest that NPY might potentially play a role in minimizing heat stress in fasted chicks.
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Affiliation(s)
- Hatem M Eltahan
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Mohammad A Bahry
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Hui Yang
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Guofeng Han
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Linh T N Nguyen
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Hiromi Ikeda
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Mohamed N Ali
- Agriculture Research Center, Animal Production Research Institute, Agriculture Ministry, Cairo, Egypt
| | - Khairy A Amber
- Division for Poultry Production, Faculty of Agriculture, Kafr-Elsheikh University, Kafr-Elsheikh, Egypt
| | - Mitsuhiro Furuse
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Vishwajit S Chowdhury
- Division for Experimental Natural Science, Faculty of Arts and Science, Graduate School of Bioresource and Bioenvironmental Science, Kyushu University, Fukuoka, Japan
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11
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Cubuk C, Kemmling J, Fabrizius A, Herwig A. Transcriptome Analysis of Hypothalamic Gene Expression during Daily Torpor in Djungarian Hamsters ( Phodopus sungorus). Front Neurosci 2017; 11:122. [PMID: 28348515 PMCID: PMC5346580 DOI: 10.3389/fnins.2017.00122] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 02/27/2017] [Indexed: 01/03/2023] Open
Abstract
Animals living at high or temperate latitudes are challenged by extensive changes in environmental conditions over seasons. Djungarian hamsters (Phodopus sungorus) are able to cope with extremely cold ambient temperatures and food scarcity in winter by expressing spontaneous daily torpor. Daily torpor is a circadian controlled voluntary reduction of metabolism that can reduce energy expenditure by up to 65% when used frequently. In the past decades it has become more and more apparent, that the hypothalamus is likely to play a key role in regulating induction and maintenance of daily torpor, but the molecular signals, which lead to the initiation of daily torpor, are still unknown. Here we present the first transcriptomic study of hypothalamic gene expression patterns in Djungarian hamsters during torpor entrance. Based on Illumina sequencing we were able to identify a total number of 284 differentially expressed genes, whereby 181 genes were up- and 103 genes down regulated during torpor entrance. The 20 most up regulated group contained eight genes coding for structure proteins, including five collagen genes, dnha2 and myo15a, as well as the procoagulation factor vwf. In a proximate approach we investigated these genes by quantitative real-time PCR (qPCR) analysis over the circadian cycle in torpid and normothermic animals at times of torpor entrance, mid torpor, arousal and post-torpor. These qPCR data confirmed up regulation of dnah2, myo15a, and vwf during torpor entrance, but a decreased mRNA level for all other investigated time points. This suggests that gene expression of structure genes as well as the procoagulation factor are specifically initiated during the early state of torpor and provides evidence for protective molecular adaptions in the hypothalamus of Djungarian hamsters including changes in structure, transport of biomolecules and coagulation.
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Affiliation(s)
- Ceyda Cubuk
- Zoologisches Institut, Universität Hamburg Hamburg, Germany
| | - Julia Kemmling
- Zoologisches Institut, Universität Hamburg Hamburg, Germany
| | | | - Annika Herwig
- Zoologisches Institut, Universität Hamburg Hamburg, Germany
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12
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Drew KL, Frare C, Rice SA. Neural Signaling Metabolites May Modulate Energy Use in Hibernation. Neurochem Res 2017; 42:141-150. [PMID: 27878659 PMCID: PMC5284051 DOI: 10.1007/s11064-016-2109-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 10/05/2016] [Accepted: 11/11/2016] [Indexed: 12/23/2022]
Abstract
Despite an epidemic in obesity and metabolic syndrome limited means exist to effect adiposity or metabolic rate other than life style changes. Here we review evidence that neural signaling metabolites may modulate thermoregulatory pathways and offer novel means to fine tune energy use. We extend prior reviews on mechanisms that regulate thermogenesis and energy use in hibernation by focusing primarily on the neural signaling metabolites adenosine, AMP and glutamate.
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Affiliation(s)
- Kelly L Drew
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA.
| | - Carla Frare
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Sarah A Rice
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
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13
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Jastroch M, Giroud S, Barrett P, Geiser F, Heldmaier G, Herwig A. Seasonal Control of Mammalian Energy Balance: Recent Advances in the Understanding of Daily Torpor and Hibernation. J Neuroendocrinol 2016; 28. [PMID: 27755687 DOI: 10.1111/jne.12437] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 10/07/2016] [Accepted: 10/15/2016] [Indexed: 12/20/2022]
Abstract
Endothermic mammals and birds require intensive energy turnover to sustain high body temperatures and metabolic rates. To cope with the energetic bottlenecks associated with the change of seasons, and to minimise energy expenditure, complex mechanisms and strategies are used, such as daily torpor and hibernation. During torpor, metabolic depression and low body temperatures save energy. However, these bouts of torpor, lasting for hours to weeks, are interrupted by active 'euthermic' phases with high body temperatures. These dynamic transitions require precise communication between the brain and peripheral tissues to defend rheostasis in energetics, body mass and body temperature. The hypothalamus appears to be the major control centre in the brain, coordinating energy metabolism and body temperature. The sympathetic nervous system controls body temperature by adjustments of shivering and nonshivering thermogenesis, with the latter being primarily executed by brown adipose tissue. Over the last decade, comparative physiologists have put forward integrative studies on the ecophysiology, biochemistry and molecular regulation of energy balance in response to seasonal challenges, food availability and ambient temperature. Mammals coping with such environments comprise excellent model organisms for studying the dynamic regulation of energy metabolism. Beyond the understanding of how animals survive in nature, these studies also uncover general mechanisms of mammalian energy homeostasis. This research will benefit efforts of translational medicine aiming to combat emerging human metabolic disorders. The present review focuses on recent advances in the understanding of energy balance and its neuronal and endocrine control during the most extreme metabolic fluctuations in nature: daily torpor and hibernation.
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Affiliation(s)
- M Jastroch
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center & German Diabetes Center (DZD), Helmholtz Zentrum München, Neuherberg, Germany
| | - S Giroud
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - P Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - F Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - G Heldmaier
- Animal Physiology, Philipps-Universität Marburg, Marburg, Germany
| | - A Herwig
- Zoological Institute, University of Hamburg, Hamburg, Germany
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14
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Cubuk C, Bank JHH, Herwig A. The Chemistry of Cold: Mechanisms of Torpor Regulation in the Siberian Hamster. Physiology (Bethesda) 2016; 31:51-9. [DOI: 10.1152/physiol.00028.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Siberian hamsters use spontaneous daily torpor, a state of hypometabolism and hypothermia, to save energy during winter. Multiple neuroendocrine signals set the scene for spontaneous torpor to occur, and several brain areas have been identified as potential sites for torpor regulation. Here, we summarize the known mechanisms of a fascinating physiological state in the Siberian hamster.
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Affiliation(s)
- Ceyda Cubuk
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Hamburg, Germany
| | - Jonathan H. H. Bank
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Hamburg, Germany
| | - Annika Herwig
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Hamburg, Germany
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15
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Chong ACN, Greendyk RA, Zeltser LM. Distinct networks of leptin- and insulin-sensing neurons regulate thermogenic responses to nutritional and cold challenges. Diabetes 2015; 64:137-46. [PMID: 25125486 PMCID: PMC4274810 DOI: 10.2337/db14-0567] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Defense of core body temperature (Tc) can be energetically costly; thus, it is critical that thermoregulatory circuits are modulated by signals of energy availability. Hypothalamic leptin and insulin signals relay information about energy status and are reported to promote thermogenesis, raising the possibility that they interact to direct an appropriate response to nutritional and thermal challenges. To test this idea, we used an Nkx2.1-Cre driver to generate conditional knockouts (KOs) in mice of leptin receptor (L(2.1)KO), insulin receptor (I(2.1)KO), and double KOs of both receptors (D(2.1)KO). L(2.1)KOs are hyperphagic and obese, whereas I(2.1)KOs are similar to controls. D(2.1)KOs exhibit higher body weight and adiposity than L(2.1)KOs, solely due to reduced energy expenditure. At 20-22°C, fed L(2.1)KOs maintain a lower baseline Tc than controls, which is further decreased in D(2.1)KOs. After an overnight fast, some L(2.1)KOs dramatically suppress energy expenditure and enter a torpor-like state; this behavior is markedly enhanced in D(2.1)KOs. When fasted mice are exposed to 4°C, L(2.1)KOs and D(2.1)KOs both mount a robust thermogenic response and rapidly increase Tc. These observations support the idea that neuronal populations that integrate information about energy stores to regulate the defense of Tc set points are distinct from those required to respond to a cold challenge.
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Affiliation(s)
- Angie C N Chong
- Institute of Human Nutrition, Columbia University, New York, NY Naomi Berrie Diabetes Center, Columbia University, New York, NY
| | | | - Lori M Zeltser
- Naomi Berrie Diabetes Center, Columbia University, New York, NY Department of Pathology and Cell Biology, Columbia University, New York, NY
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16
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Abstract
The continuous rise in obesity is a major concern for future healthcare management. Many strategies to control body weight focus on a permanent modification of food intake with limited success in the long term. Metabolism or energy expenditure is the other side of the coin for the regulation of body weight, and strategies to enhance energy expenditure are a current focus for obesity treatment, especially since the (re)-discovery of the energy depleting brown adipose tissue in adult humans. Conversely, several human illnesses like neurodegenerative diseases, cancer, or autoimmune deficiency syndrome suffer from increased energy expenditure and severe weight loss. Thus, strategies to modulate energy expenditure to target weight gain or loss would improve life expectancies and quality of life in many human patients. The aim of this book chapter is to give an overview of our current understanding and recent progress in energy expenditure control with specific emphasis on central control mechanisms.
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17
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Doherty AH, Florant GL, Donahue SW. Endocrine regulation of bone and energy metabolism in hibernating mammals. Integr Comp Biol 2014; 54:463-83. [PMID: 24556365 DOI: 10.1093/icb/icu001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Precise coordination among organs is required to maintain homeostasis throughout hibernation. This is particularly true in balancing bone remodeling processes (bone formation and resorption) in hibernators experiencing nutritional deprivation and extreme physical inactivity, two factors normally leading to pronounced bone loss in non-hibernating mammals. In recent years, important relationships between bone, fat, reproductive, and brain tissues have come to light. These systems share interconnected regulatory mechanisms of energy metabolism that potentially protect the skeleton during hibernation. This review focuses on the endocrine and neuroendocrine regulation of bone/fat/energy metabolism in hibernators. Hibernators appear to have unique mechanisms that protect musculoskeletal tissues while catabolizing their abundant stores of fat. Furthermore, the bone remodeling processes that normally cause disuse-induced bone loss in non-hibernators are compared to bone remodeling processes in hibernators, and possible adaptations of the bone signaling pathways that protect the skeleton during hibernation are discussed. Understanding the biological mechanisms that allow hibernators to survive the prolonged disuse and fasting associated with extreme environmental challenges will provide critical information regarding the limit of convergence in mammalian systems and of skeletal plasticity, and may contribute valuable insight into the etiology and treatment of human diseases.
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Affiliation(s)
- Alison H Doherty
- *Department of Biology, Colorado State University, Fort Collins, CO 80523-1620, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1620, USA*Department of Biology, Colorado State University, Fort Collins, CO 80523-1620, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1620, USA
| | - Gregory L Florant
- *Department of Biology, Colorado State University, Fort Collins, CO 80523-1620, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1620, USA
| | - Seth W Donahue
- *Department of Biology, Colorado State University, Fort Collins, CO 80523-1620, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1620, USA
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18
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Van der Zee CEEM. Hypothalamic plasticity of neuropeptide Y is lacking in brain-type creatine kinase double knockout mice with defective thermoregulation. Eur J Pharmacol 2013; 719:137-144. [PMID: 23891845 DOI: 10.1016/j.ejphar.2013.07.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 06/28/2013] [Accepted: 07/01/2013] [Indexed: 01/14/2023]
Abstract
The neural substrate of adaptive thermoregulation in mice lacking both brain-type creatine kinase isoforms is further investigated. The cytosolic brain-type creatine kinase (CK-B) and mitochondrial ubiquitous creatine kinase (UbCKmit) are expressed in neural cells throughout the central and peripheral nervous system, where they have an important role in cellular energy homeostasis. Several integral functions appear altered when creatine kinases are absent in the brain (Jost et al., 2002; Streijger et al., 2004, 2005), which has been explained by inefficient neuronal transmission. The CK--/-- double knockout mice demonstrate every morning a body temperature drop of ~1.0 °C, and they have impaired thermogenesis, as revealed by severe hypothermia upon cold exposure. This defective thermoregulation is not associated with abnormal food intake, decreased locomotive activity, or increased torpor sensitivity. Although white and brown adipose tissue fat pads are diminished in CK--/-- mice, intravenous norepinephrine infusion results in a normal brown adipose tissue response with increasing core body temperatures, indicating that the sympathetic innervation functions correctly (Streijger et al., 2009). This study revealed c-fos changes following a cold challenge, and that neuropeptide Y levels were decreased in the paraventricular nucleus of wildtype, but not CK--/--, mice. A reduction in hypothalamic neuropeptide Y is coupled to increased uncoupling protein 1 expression in brown adipose tissue, resulting in thermogenesis. In CK--/-- mice the neuropeptide Y levels did not change. This lack of hypothalamic plasticity of neuropeptide Y might be the result of inefficient neuronal transmission or can be explained by the previous observation of reduced circulating levels of leptin in CK--/-- mice.
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Affiliation(s)
- Catharina E E M Van der Zee
- Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
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19
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Bartfai T, Conti B. Molecules affecting hypothalamic control of core body temperature in response to calorie intake. Front Genet 2012; 3:184. [PMID: 23097647 PMCID: PMC3466567 DOI: 10.3389/fgene.2012.00184] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 08/31/2012] [Indexed: 01/07/2023] Open
Abstract
Core body temperature (CBT) and calorie intake are main components of energy homeostasis and two important regulators of health, longevity, and aging. In homeotherms, CBT can be influenced by calorie intake as food deprivation or calorie restriction (CR) lowers CBT whereas feeding has hyperthermic effects. The finding that in mice CBT prolonged lifespan independently of CR, suggested that the mechanisms modulating CBT may represent important regulators of aging. Here we summarize the current knowledge on the signaling molecules and their receptors that participate in the regulation of CBT responses to calorie intake. These include hypothalamic neuropeptides regulating feeding but also energy expenditure via modulation of thermogenesis. We also report studies indicating that nutrient signals can contribute to regulation of CBT by direct action on hypothalamic preoptic warm-sensitive neurons that in turn regulate adaptive thermogenesis and hence CBT. Finally, we show the role played by two orphans G protein-coupled receptor: GPR50 and GPR83, that were recently demonstrated to regulate temperature-dependent energy expenditure.
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Affiliation(s)
- Tamas Bartfai
- Department of Chemical Physiology, The Scripps Research Institute La Jolla, CA, USA
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20
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Iliff BW, Swoap SJ. Central adenosine receptor signaling is necessary for daily torpor in mice. Am J Physiol Regul Integr Comp Physiol 2012; 303:R477-84. [PMID: 22785425 DOI: 10.1152/ajpregu.00081.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When calorically restricted at cool ambient temperatures, mice conserve energy by entering torpor, during which metabolic rate (MR), body temperature (T(b)), heart rate (HR), and locomotor activity (LMA) decrease. Treatment with exogenous adenosine produces a similar hypometabolic state. In this study, we conducted a series of experiments using the nonspecific adenosine receptor antagonists aminophylline and 8-sulfophenyltheophylline (8-SPT) to test the hypothesis that adenosine signaling is necessary for torpor in fasted mice. In the first experiment, mice were subcutaneously infused with aminophylline while T(b), HR, and LMA were continuously monitored using implanted radiotelemeters. During a 23-h fast, saline-treated mice were torpid for 518 ± 43 min, whereas aminophylline-treated mice were torpid for significantly less time (54 ± 20 min). In a second experiment, aminophylline was infused subcutaneously into torpid mice to test the role of adenosine in the maintenance of torpor. Aminophylline reversed the hypometabolism, hypothermia, bradycardia, and hypoactivity of torpor, whereas saline did not. In the third and fourth experiments, the polar adenosine antagonist 8-SPT, which does not cross the blood-brain barrier, was infused either subcutaneously or intracerebroventricularly to test the hypothesis that both peripheral and central adenosine receptor signaling are necessary for the maintenance of torpor. Intracerebroventricular, but not subcutaneous, infusion of 8-SPT causes a return to euthermia. These findings support the hypothesis that adenosine is necessary for torpor in mice and further suggest that whereas peripheral adenosine signaling is not necessary for the maintenance of torpor, antagonism of central adenosine is sufficient to disrupt torpor.
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Affiliation(s)
- Benjamin W Iliff
- Department of Biology, Williams College, Williamstown, MA 01267, USA
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21
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Chu LP, Swoap SJ. Oral bezafibrate induces daily torpor and FGF21 in mice in a PPAR alpha dependent manner. J Therm Biol 2012. [DOI: 10.1016/j.jtherbio.2011.11.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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22
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Bouma HR, Verhaag EM, Otis JP, Heldmaier G, Swoap SJ, Strijkstra AM, Henning RH, Carey HV. Induction of torpor: mimicking natural metabolic suppression for biomedical applications. J Cell Physiol 2012; 227:1285-90. [PMID: 21618525 DOI: 10.1002/jcp.22850] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian hibernation consists of periods of depressed metabolism and reduced body temperature called "torpor" that are interspersed by normothermic arousal periods. Numerous cellular processes are halted during torpor, including transcription, translation, and ion homeostasis. Hibernators are able to survive long periods of low blood flow and body temperature followed by rewarming and reperfusion without overt signs of organ injury, which makes these animals excellent models for application of natural protective mechanisms to human medicine. This review examines efforts to induce torpor-like states in non-hibernating species using pharmacological compounds. Elucidating the underlying mechanisms of natural and pharmacologically induced torpor will speed the development of new clinical approaches to treat a variety of trauma and stress states in humans.
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Affiliation(s)
- Hjalmar R Bouma
- Department of Clinical Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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23
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Bechtold DA, Sidibe A, Saer BRC, Li J, Hand LE, Ivanova EA, Darras VM, Dam J, Jockers R, Luckman SM, Loudon ASI. A role for the melatonin-related receptor GPR50 in leptin signaling, adaptive thermogenesis, and torpor. Curr Biol 2011; 22:70-7. [PMID: 22197240 DOI: 10.1016/j.cub.2011.11.043] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 11/03/2011] [Accepted: 11/21/2011] [Indexed: 12/21/2022]
Abstract
The ability of mammals to maintain a constant body temperature has proven to be a profound evolutionary advantage, allowing members of this class to thrive in most environments on earth. Intriguingly, some mammals employ bouts of deep hypothermia (torpor) to cope with reduced food supply and harsh climates [1, 2]. During torpor, physiological processes such as respiration, cardiac function, and metabolic rate are severely depressed, yet the neural mechanisms that regulate torpor remain unclear [3]. Hypothalamic responses to energy signals, such as leptin, influence the expression of torpor [4-7]. We show that the orphan receptor GPR50 plays an important role in adaptive thermogenesis and torpor. Unlike wild-type mice, Gpr50(-/-) mice readily enter torpor in response to fasting and 2-deoxyglucose administration. Decreased thermogenesis in Gpr50(-/-) mice is not due to a deficit in brown adipose tissue, the principal site of nonshivering thermogenesis in mice [8]. GPR50 is highly expressed in the hypothalamus of several species, including man [9, 10]. In line with this, altered thermoregulation in Gpr50(-/-) mice is associated with attenuated responses to leptin and a suppression of thyrotropin-releasing hormone. Thus, our findings identify hypothalamic circuits involved in torpor and reveal GPR50 to be a novel component of adaptive thermogenesis in mammals.
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24
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Shimizu N, Chikahisa S, Kitaoka K, Nishino S, Séi H. Refeeding after a 24-hour fasting deepens NREM sleep in a time-dependent manner. Physiol Behav 2011; 104:480-7. [PMID: 21605579 DOI: 10.1016/j.physbeh.2011.05.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 05/06/2011] [Accepted: 05/06/2011] [Indexed: 10/18/2022]
Abstract
Sleep/wake cycle is regulated by a variety of neuropeptides in the hypothalamus, a brain region that also regulates energy homeostasis and feeding behavior. Since circadian rhythms are affected by energy metabolism and feeding condition, we investigated whether changes in feeding regimen would influence sleep/wake parameters and body temperature. We monitored sleep and body temperature across three days of baseline (day 1), fasting (day 2), and refeeding (day 3) conditions under ordinary ambient temperature and employed different refeeding schedules. Refeeding at ZT1 following the 24-h fasting enhanced EEG delta power in NREM sleep. However, when the time of refeeding was set at either ZT7 or ZT12, the enhancement of EEG delta power was attenuated. The amount of NREM sleep was not largely affected by a 24-h fasting started at ZT1, although fasting that started at ZT12 changed the temporal distribution of NREM sleep. Hypothalamic nNOS mRNA level was increased both before and after refeeding at ZT1 compared with control condition, while there was no significant change in mice refed at ZT7. Level of NPY mRNA in the arcuate nucleus was increased before the refeeding only at ZT1. These results suggest that refeeding after a 24-h fasting makes NREM sleep deeper in a time-dependent manner.
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Affiliation(s)
- Noriyuki Shimizu
- Department of Integrative Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan
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25
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Bousquet-Moore D, Mains RE, Eipper BA. Peptidylgycine α-amidating monooxygenase and copper: a gene-nutrient interaction critical to nervous system function. J Neurosci Res 2011; 88:2535-45. [PMID: 20648645 DOI: 10.1002/jnr.22404] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Peptidylgycine alpha-amidating monooxygenase (PAM), a highly conserved copper-dependent enzyme, is essential for the synthesis of all amidated neuropeptides. Biophysical studies revealed that the binding of copper to PAM affects its structure, and cell biological studies demonstrated that the endocytic trafficking of PAM was sensitive to copper. We review data indicating that genetic reduction of PAM expression and mild copper deficiency in mice cause similar alterations in several physiological functions known to be regulated by neuropeptides: thermal regulation, seizure sensitivity, and anxiety-like behavior.
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26
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Abe K, Kuo L, Zukowska Z. Neuropeptide Y is a mediator of chronic vascular and metabolic maladaptations to stress and hypernutrition. Exp Biol Med (Maywood) 2010; 235:1179-84. [PMID: 20881322 DOI: 10.1258/ebm.2010.009136] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Neuropeptide Y (NPY) is a central neuromodulator and peripheral sympathetic neurotransmitter that also has important regulatory roles in cardiovascular, neuroendocrine, immune and metabolic functions during stress. Focusing on the peripheral actions of the peptide in rodent models, we summarize recent studies from our laboratory demonstrating that stress-induced release of NPY mediates accelerated atherosclerosis/restenosis, obesity and metabolic-like syndrome, particularly when combined with a high fat, high sugar diet. In this review, we propose mechanisms of NPY's actions, its receptors and cellular substrates that increase the risk for cardiovascular and metabolic diseases when chronic stress is associated with pre-existing vascular injury and/or states of hypernutrition.
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Affiliation(s)
- Ken Abe
- Department of Physiology and Biophysics, Georgetown University Medical Center, 3900 Reservoir Rd NW, Washington, DC 20057, USA
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27
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Healy JE, Ostrom CE, Wilkerson GK, Florant GL. Plasma ghrelin concentrations change with physiological state in a sciurid hibernator (Spermophilus lateralis). Gen Comp Endocrinol 2010; 166:372-8. [PMID: 20005230 PMCID: PMC2834803 DOI: 10.1016/j.ygcen.2009.12.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 10/22/2009] [Accepted: 12/04/2009] [Indexed: 12/29/2022]
Abstract
Ghrelin is a recently discovered hormone which has profound effects on food intake and lipogenesis in mammals. In all mammals studied thus far, plasma ghrelin concentrations are increased before a meal and decrease immediately following a meal; ghrelin levels increase with fasting. The golden-mantled ground squirrel Spermophilus lateralis (also known as Callospermophilus lateralis (see Helgen et al., 2009) is a diurnal hibernator which has a robust annual cycle of body mass gain and loss that is primarily controlled by food intake. We hypothesized that in spring, summer, and autumn, the endogenous ghrelin concentrations of hibernators would be similar to those of non-hibernators, but that during the winter hibernation season, plasma ghrelin concentrations would be low or undetectable. We found that peripherally injected ghrelin significantly increased food intake in June. Plasma ghrelin concentrations were significantly increased through 5 days of fasting during a short-term fast in summer. Over a 24h period, ghrelin concentrations increased at night and decreased during the day with drops corresponding to times when squirrels were eating. In January, ghrelin concentrations are low but measurable even while animals are at low body temperature (Tb). This is the first report of ghrelin concentrations in a non-photoperiodic hibernator. We suggest that ghrelin may be important for the regulation of food intake and the body mass cycle in mammals that hibernate.
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Affiliation(s)
- Jessica E Healy
- Department of Biology, Colorado State University, Fort Collins, CO, USA.
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28
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ISHIDA NK, UCHIDA D, DOI R, OISHI K, CHIKAHISA S, SEI H, HAMASAKA Y, SUZUKI T, HANAI S. Role of PPARα in control of torpor through FGF21-NPY pathway: From circadian clock genes to seasonal change and cardiovascular disease. Sleep Biol Rhythms 2010. [DOI: 10.1111/j.1479-8425.2009.00413.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Zhang L, Macia L, Turner N, Enriquez RF, Riepler SJ, Nguyen AD, Lin S, Lee NJ, Shi YC, Yulyaningsih E, Slack K, Baldock PA, Herzog H, Sainsbury A. Peripheral neuropeptide Y Y1 receptors regulate lipid oxidation and fat accretion. Int J Obes (Lond) 2009; 34:357-73. [PMID: 19918245 DOI: 10.1038/ijo.2009.232] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Neuropeptide Y and its Y receptors are important players in the regulation of energy homeostasis. However, while their functions in feeding regulation are well recognized, functions in other critical aspects of energy homeostasis are largely unknown. To investigate the function of Y1 receptors in the regulation of energy homeostasis, we examined energy expenditure, physical activity, body composition, oxidative fuel selection and mitochondrial oxidative capacity in germline Y1(-/-) mice as well as in a conditional Y1-receptor-knockdown model in which Y1 receptors were knocked down in peripheral tissues of adult mice. RESULTS Germline Y1(-/-) mice of both genders not only exhibit a decreased respiratory exchange ratio, indicative of increased lipid oxidation, but interestingly also develop late-onset obesity. However, the increased lipid oxidation is a primary effect of Y1 deletion rather than secondary to increased adiposity, as young Y1(-/-) mice are lean and show the same effect. The mechanism behind this is likely because of increased liver and muscle protein levels of carnitine palmitoyltransferase-1 (CPT-1) and maximal activity of key enzymes involved in beta-oxidation; beta-hydroxyacyl CoA dehydrogenase (betaHAD) and medium-chain acyl-CoA dehydrogenase (MCAD), leading to increased mitochondrial capacity for fatty acid transport and oxidation. These effects are controlled by peripheral Y1-receptor signalling, as adult-onset conditional Y1 knockdown in peripheral tissues also leads to increased lipid oxidation, liver CPT-1 levels and betaHAD activity. Importantly, these mice are resistant to diet-induced obesity. CONCLUSIONS This work shows the primary function of peripheral Y1 receptors in the regulation of oxidative fuel selection and adiposity, opening up new avenues for anti-obesity treatments by targeting energy utilization in peripheral tissues rather than suppressing appetite by central effects.
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Affiliation(s)
- L Zhang
- Neuroscience Research Program, Garvan Institute of Medical Research, Darlinghurst, Sydney, New South Wales, Australia
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30
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Bousquet-Moore D, Prohaska JR, Nillni EA, Czyzyk T, Wetsel WC, Mains RE, Eipper BA. Interactions of peptide amidation and copper: novel biomarkers and mechanisms of neural dysfunction. Neurobiol Dis 2009; 37:130-40. [PMID: 19815072 DOI: 10.1016/j.nbd.2009.09.016] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/10/2009] [Accepted: 09/27/2009] [Indexed: 01/14/2023] Open
Abstract
Mammalian genomes encode only a small number of cuproenzymes. The many genes involved in coordinating copper uptake, distribution, storage and efflux make gene/nutrient interactions especially important for these cuproenzymes. Copper deficiency and copper excess both disrupt neural function. Using mice heterozygous for peptidylglycine alpha-amidating monooxygenase (PAM), a cuproenzyme essential for the synthesis of many neuropeptides, we identified alterations in anxiety-like behavior, thermoregulation and seizure sensitivity. Dietary copper supplementation reversed a subset of these deficits. Wildtype mice maintained on a marginally copper-deficient diet exhibited some of the same deficits observed in PAM(+/-) mice and displayed alterations in PAM metabolism. Altered copper homeostasis in PAM(+/-) mice suggested a role for PAM in the cell type specific regulation of copper metabolism. Physiological functions sensitive to genetic limitations of PAM that are reversed by supplemental copper and mimicked by copper deficiency may serve as indicators of marginal copper deficiency.
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Affiliation(s)
- Danielle Bousquet-Moore
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
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31
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Role of PPARα in the control of torpor through FGF21-NPY pathway: From circadian clock to seasonal change in mammals. PPAR Res 2009; 2009:412949. [PMID: 19536348 PMCID: PMC2695967 DOI: 10.1155/2009/412949] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 03/03/2009] [Accepted: 04/02/2009] [Indexed: 12/17/2022] Open
Abstract
In nature, hibernating animals encounter fasting, cold temperature and short day seasonally. Torpor is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism to adapt such a severe environment. Ablation of the central clock synchronizer, the suprachiasmatic nucleus in brain, abolishes torpor, a hibernation-like state, implicating the circadian clock involved in this seasonal change. Biologists knows well the energy source of daily heterotherms/hibernators changed from glucose to lipids in winter. Here we review several lines of evidence of a master transcriptional regulator in lipid catabolism, PPARα, in the control of torpor through FGF21-NPY pathway. This indicate the importance of circadian—and photoperiod—regulation of PPARα to tell seasons in our body.
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32
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Bousquet-Moore D, Ma XM, Nillni EA, Czyzyk TA, Pintar JE, Eipper BA, Mains RE. Reversal of physiological deficits caused by diminished levels of peptidylglycine alpha-amidating monooxygenase by dietary copper. Endocrinology 2009; 150:1739-47. [PMID: 19022883 PMCID: PMC2659272 DOI: 10.1210/en.2008-1202] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Amidated peptides are critically involved in many physiological functions. Genetic deletion of peptidylglycine alpha-amidating monooxygenase (PAM), the only enzyme that can synthesize these peptides, is embryonically lethal. The goal of the present study was the identification of physiological functions impaired by haploinsufficiency of PAM. Regulation of the hypothalamic-pituitary-thyroid axis and body temperature, functions requiring contributions from multiple amidated peptides, were selected for evaluation. Based on serum T(4) and pituitary TSH-beta mRNA levels, mice heterozygous for PAM (PAM(+/-)) were euthyroid at baseline. Feedback within the hypothalamic-pituitary-thyroid axis was impaired in PAM(+/-) mice made hypothyroid using a low iodine/propylthiouracil diet. Despite their normal endocrine response to cold, PAM(+/-) mice were unable to maintain body temperature as well as wild-type littermates when kept in a 4 C environment. When provided with additional dietary copper, PAM(+/-) mice maintained body temperature as well as wild-type mice. Pharmacological activation of vasoconstriction or shivering also allowed PAM(+/-) mice to maintain body temperature. Cold-induced vasoconstriction was deficient in PAM(+/-) mice. This deficit was eliminated in PAM(+/-) mice receiving a diet with supplemental copper. These results suggest that dietary deficiency of copper, coupled with genetic deficits in PAM, could result in physiological deficits in humans.
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Affiliation(s)
- D Bousquet-Moore
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030-3401, USA
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33
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Abstract
Hibernation is one of the most dramatic examples of phenotypic plasticity in mammals. During periods of food shortage and/or reduced ambient temperatures hibernating mammals become heterothermic, allowing their body temperature to decrease while entering an energy-conserving torpid state. In order to survive the multi-month hibernation season many species engage in hyperphagy, dramatically increasing adipose stores prior to the onset of hibernation. Nuclear receptors are a superfamily of transcription factors many of which bind lipophilic molecules as ligands. They regulate a variety of processes including energy homeostasis, carbohydrate and lipid metabolism, inflammation and circadian rhythm. Given that lipids are integral in the hibernation phenotype they may play important regulatory roles through their interactions with nuclear receptors. Here we review current knowledge and suggest possible roles in mammalian hibernation for peroxisome proliferator-activated receptors (PPARs), farnesoid X receptors (FXRs), liver X receptors (LXRs), retinoid-related orphan receptors (RORs) and Rev-ERBs.
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Affiliation(s)
- Clark J Nelson
- Department of Comparative Biosciences, University of Wisconsin School of Veterinary Medicine, Madison, WI 53706, USA
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34
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Gutman R, Hacmon-Keren R, Choshniak I, Kronfeld-Schor N. Effect of food availability and leptin on the physiology and hypothalamic gene expression of the golden spiny mouse: a desert rodent that does not hoard food. Am J Physiol Regul Integr Comp Physiol 2008; 295:R2015-23. [DOI: 10.1152/ajpregu.00105.2008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Food availability and quality in desert habitats are spatially and temporally unpredictable, and animals face periods of food shortage. The golden spiny mouse ( Acomys russatus) is an omnivorous desert rodent that does not hoard food, requiring it to withstand such periods by physiological means alone. In response to food restriction, plasma leptin concentrations, core body temperature, and energy expenditure of the spiny mouse decrease significantly after 24 h, and most spiny mice are able to maintain their body mass to ∼85% of ad libitum for a prolonged period of time. Both 1-day food deprivation and long-term food restriction had a significant effect on body mass and plasma leptin concentrations, which decreased significantly with a high correlation, as well as on the orexigenic agouti-related protein, which increased significantly as a result of the 24-h food deprivation; and on neuropeptide Y (NPY), in which the increase was more pronounced under long-term food restriction. Food restriction and food deprivation had no effect, however, on the anorexigenic pro-opiomelanocortin and cocaine and amphetamine-related transcript. Leptin administration to food-restricted spiny mice did not affect food intake or the rate of decrease in body mass, indicating that it cannot overcome the drive to eat when food is scarce. However, it did result in a significant decrease in NPY levels, and the spiny mice spent less time at low body temperatures compared with PBS-treated golden spiny mice. These results show that in food-restricted golden spiny mice, leptin affects thermogenesis, but not food consumption, and suggest that the thermoregulatory effects of leptin are mediated by NPY.
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Chikahisa S, Tominaga K, Kawai T, Kitaoka K, Oishi K, Ishida N, Rokutan K, Séi H. Bezafibrate, a peroxisome proliferator-activated receptors agonist, decreases body temperature and enhances electroencephalogram delta-oscillation during sleep in mice. Endocrinology 2008; 149:5262-71. [PMID: 18787029 DOI: 10.1210/en.2008-0285] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor family. PPARs play a critical role in lipid and glucose metabolism. We examined whether chronic treatment with bezafibrate, a PPAR agonist, would alter sleep and body temperature (BT). Mice fed with a control diet were monitored for BT, electroencephalogram (EEG), and electromyogram for 48 h under light-dark conditions. After obtaining the baseline recording, the mice were provided with bezafibrate-supplemented food for 2 wk, after which the same recordings were performed. Two-week feeding of bezafibrate decreased BT, especially during the latter half of the dark period. BT rhythm and sleep/wake rhythm were phase advanced about 2-3 h by bezafibrate treatment. Bezafibrate treatment also increased the EEG delta-power in nonrapid eye movement sleep compared with the control diet attenuating its daily amplitude. Furthermore, bezafibrate-treated mice showed no rebound of EEG delta-power in nonrapid eye movement sleep after 6 h sleep deprivation, whereas values in control mice largely increased relative to baseline. DNA microarray, and real-time RT-PCR analysis showed that bezafibrate treatment increased levels of Neuropeptide Y mRNA in the hypothalamus at both Zeitgeber time (ZT) 10 and ZT22, and decreased proopiomelanocortin-alpha mRNA in the hypothalamus at ZT10. These findings demonstrate that PPARs participate in the control of both BT and sleep regulation, which accompanied changes in gene expression in the hypothalamus. Activation of PPARs may enhance deep sleep and improve resistance to sleep loss.
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Affiliation(s)
- Sachiko Chikahisa
- Department of Integrative Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan
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Swoap SJ. The pharmacology and molecular mechanisms underlying temperature regulation and torpor. Biochem Pharmacol 2008; 76:817-24. [PMID: 18644349 DOI: 10.1016/j.bcp.2008.06.017] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 06/02/2008] [Accepted: 06/02/2008] [Indexed: 01/08/2023]
Abstract
The ability to enter a hypometabolic state upon restriction of caloric intake is pivotal for animal survival: balancing the energy budget in endotherms can be a real struggle when food is not available and/or the demand for heat production to maintain homeothermy becomes excessive. Bouts of torpor, characterized by metabolic rates well below a basal metabolic rate and core body temperatures that may be just a few degrees above the ambient temperature, are utilized among many organisms across the animal kingdom, including those that could be described as typical laboratory animals, like the mouse or hamster. Daily heterotherms, which are the focus of this commentary, enter shallow torpor bouts and do so usually under acute food shortage conditions and a relatively cool environment. Due to their small size, the body temperature of these animals is very responsive to food deprivation, pharmacological inhibition of metabolic rate, and cardiovascular depressants. This commentary examines recent developments concerning the neuroendocrine mechanisms in place that may mediate fasting-induced torpor in daily heterotherms. Further this commentary highlights pharmacological induction of hypothermia in small mammals.
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Affiliation(s)
- Steven J Swoap
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
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