1
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Hazlerigg DG, Simonneaux V, Dardente H. Melatonin and Seasonal Synchrony in Mammals. J Pineal Res 2024; 76:e12996. [PMID: 39129720 DOI: 10.1111/jpi.12996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2024] [Revised: 05/27/2024] [Accepted: 07/16/2024] [Indexed: 08/13/2024]
Abstract
In mammals, seasonal opportunities and challenges are anticipated through programmed changes in physiology and behavior. Appropriate anticipatory timing depends on synchronization to the external solar year, achieved through the use of day length (photoperiod) as a synchronizing signal. In mammals, nocturnal production of melatonin by the pineal gland is the key hormonal mediator of photoperiodic change, exerting its effects via the hypothalamopituitary axis. In this review/perspective, we consider the key developments during the history of research into the seasonal synchronizer effect of melatonin, highlighting the role that the pars tuberalis-tanycyte module plays in this process. We go on to consider downstream pathways, which include discrete hypothalamic neuronal populations. Neurons that express the neuropeptides kisspeptin and (Arg)(Phe)-related peptide-3 (RFRP-3) govern seasonal reproductive function while neurons that express somatostatin may be involved in seasonal metabolic adaptations. Finally, we identify several outstanding questions, which need to be addressed to provide a much thorough understanding of the deep impact of melatonin upon seasonal synchronization.
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Affiliation(s)
- David G Hazlerigg
- Department of Arctic and Marine Biology, Arctic Chronobiology and Physiology Research Group, Arctic Seasonal Timekeeping Initiative (ASTI), UiT-The Arctic University of Norway, Tromsø, Norway
| | - Valérie Simonneaux
- Institute for Cellular and Integrative Neuroscience, University of Strasbourg, Strasbourg, France
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2
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Mohr SM, Dai Pra R, Platt MP, Feketa VV, Shanabrough M, Varela L, Kristant A, Cao H, Merriman DK, Horvath TL, Bagriantsev SN, Gracheva EO. Hypothalamic hormone deficiency enables physiological anorexia in ground squirrels during hibernation. Nat Commun 2024; 15:5803. [PMID: 38987241 PMCID: PMC11236985 DOI: 10.1038/s41467-024-49996-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 06/19/2024] [Indexed: 07/12/2024] Open
Abstract
Mammalian hibernators survive prolonged periods of cold and resource scarcity by temporarily modulating normal physiological functions, but the mechanisms underlying these adaptations are poorly understood. The hibernation cycle of thirteen-lined ground squirrels (Ictidomys tridecemlineatus) lasts for 5-7 months and comprises weeks of hypometabolic, hypothermic torpor interspersed with 24-48-h periods of an active-like interbout arousal (IBA) state. We show that ground squirrels, who endure the entire hibernation season without food, have negligible hunger during IBAs. These squirrels exhibit reversible inhibition of the hypothalamic feeding center, such that hypothalamic arcuate nucleus neurons exhibit reduced sensitivity to the orexigenic and anorexigenic effects of ghrelin and leptin, respectively. However, hypothalamic infusion of thyroid hormone during an IBA is sufficient to rescue hibernation anorexia. Our results reveal that thyroid hormone deficiency underlies hibernation anorexia and demonstrate the functional flexibility of the hypothalamic feeding center.
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Affiliation(s)
- Sarah M Mohr
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
| | - Rafael Dai Pra
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
| | - Maryann P Platt
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
| | - Viktor V Feketa
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
| | - Marya Shanabrough
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT, 06510, USA
| | - Luis Varela
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT, 06510, USA
- Laboratory of Glia-Neuron Interactions in the Control of Hunger. Achucarro_Basque Center for Neuroscience, 48940, Leioa, Vizcaya, Spain
- IKERBASQUE, Basque Foundation for Science, 48009, Bilbao, Vizcaya, Spain
| | - Ashley Kristant
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT, 06510, USA
| | - Haoran Cao
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA
| | - Dana K Merriman
- Department of Biology, University of Wisconsin-Oshkosh, 800 Algoma Boulevard, Oshkosh, WI, 54901, USA
| | - Tamas L Horvath
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT, 06510, USA
- Laboratory of Glia-Neuron Interactions in the Control of Hunger. Achucarro_Basque Center for Neuroscience, 48940, Leioa, Vizcaya, Spain
- IKERBASQUE, Basque Foundation for Science, 48009, Bilbao, Vizcaya, Spain
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA.
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA.
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA.
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06510, USA.
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3
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Mohr SM, Pra RD, Platt MP, Feketa VV, Shanabrough M, Varela L, Kristant A, Cao H, Merriman DK, Horvath TL, Bagriantsev SN, Gracheva EO. Hypothalamic hormone deficiency enables physiological anorexia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.03.15.532843. [PMID: 38559054 PMCID: PMC10979886 DOI: 10.1101/2023.03.15.532843] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Mammalian hibernators survive prolonged periods of cold and resource scarcity by temporarily modulating normal physiological functions, but the mechanisms underlying these adaptations are poorly understood. The hibernation cycle of thirteen-lined ground squirrels (Ictidomys tridecemlineatus) lasts for 5-7 months and comprises weeks of hypometabolic, hypothermic torpor interspersed with 24-48-hour periods of an active-like interbout arousal (IBA) state. We show that ground squirrels, who endure the entire hibernation season without food, have negligible hunger during IBAs. These squirrels exhibit reversible inhibition of the hypothalamic feeding center, such that hypothalamic arcuate nucleus neurons exhibit reduced sensitivity to the orexigenic and anorexigenic effects of ghrelin and leptin, respectively. However, hypothalamic infusion of thyroid hormone during an IBA is sufficient to rescue hibernation anorexia. Our results reveal that thyroid hormone deficiency underlies hibernation anorexia and demonstrate the functional flexibility of the hypothalamic feeding center.
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Affiliation(s)
- Sarah M. Mohr
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Rafael Dai Pra
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Maryann P. Platt
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Viktor V. Feketa
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Marya Shanabrough
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT 06510, USA
| | - Luis Varela
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT 06510, USA
- Achucarro Basque Center for Neuroscience, Leioa, Spain 48940
| | - Ashley Kristant
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT 06510, USA
| | - Haoran Cao
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Dana K. Merriman
- Department of Biology, University of Wisconsin-Oshkosh, 800 Algoma Boulevard, Oshkosh, WI 54901, USA
| | - Tamas L. Horvath
- Department of Comparative Medicine, Yale University School of Medicine, 310 Cedar Street, New Haven, CT 06510, USA
- Achucarro Basque Center for Neuroscience, Leioa, Spain 48940
| | - Sviatoslav N. Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Elena O. Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
- Kavli Institute for Neuroscience, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
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Willmore L, Minerva AR, Engelhard B, Murugan M, McMannon B, Oak N, Thiberge SY, Peña CJ, Witten IB. Overlapping representations of food and social stimuli in VTA dopamine neurons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.17.541104. [PMID: 37293057 PMCID: PMC10245666 DOI: 10.1101/2023.05.17.541104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Dopamine neurons of the ventral tegmental area (VTA DA ) respond to food and social stimuli and contribute to both forms of motivation. However, it is unclear if the same or different VTA DA neurons encode these different stimuli. To address this question, we performed 2-photon calcium imaging in mice presented with food and conspecifics, and found statistically significant overlap in the populations responsive to both stimuli. Both hunger and opposite-sex social experience further increased the proportion of neurons that respond to both stimuli, implying that modifying motivation for one stimulus affects responses to both stimuli. In addition, single-nucleus RNA sequencing revealed significant co-expression of feeding- and social-hormone related genes in individual VTA DA neurons. Taken together, our functional and transcriptional data suggest overlapping VTA DA populations underlie food and social motivation.
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Affiliation(s)
- Lindsay Willmore
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Adelaide R. Minerva
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Ben Engelhard
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
- Department of Medicine, Technion, Haifa, 3525433, Israel
| | - Malavika Murugan
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Brenna McMannon
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Nirja Oak
- Department of Medicine, Technion, Haifa, 3525433, Israel
| | - Stephan Y. Thiberge
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Catherine J. Peña
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
| | - Ilana B. Witten
- Princeton Neuroscience Institute, Princeton University, Princeton NJ 08544 USA
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5
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Comparative analysis of thyroid hormone systems in rodents with subterranean lifestyle. Sci Rep 2023; 13:3122. [PMID: 36813840 PMCID: PMC9946999 DOI: 10.1038/s41598-023-30179-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 02/17/2023] [Indexed: 02/24/2023] Open
Abstract
African mole-rats are subterranean rodents inhabiting underground burrows. This habitat entails risks of overheating, hypoxia, and scarce food availability. Consequently, many subterranean species have evolved low basal metabolism and low body temperature, but the regulation of these traits at the molecular level were unknown. Measurements of serum thyroid hormone (TH) concentrations in African mole-rats have revealed a unique TH phenotype, which deviates from the typical mammalian pattern. Since THs are major regulators of metabolic rate and body temperature, we further characterised the TH system of two African mole-rat species, the naked mole-rat (Heterocephalus glaber) and the Ansell's mole-rat (Fukomys anselli) at the molecular level in a comparative approach involving the house mouse (Mus musculus) as a well-studied laboratory model in TH research. Most intriguingly, both mole-rat species had low iodide levels in the thyroid and naked mole-rats showed signs of thyroid gland hyperplasia. However, contrary to expectations, we found several species-specific differences in the TH systems of both mole-rat species, although ultimately resulting in similar serum TH concentrations. These findings indicate a possible convergent adaptation. Thus, our study adds to our knowledge for understanding adaptations to the subterranean habitat.
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6
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Junkins MS, Bagriantsev SN, Gracheva EO. Towards understanding the neural origins of hibernation. J Exp Biol 2022; 225:273864. [PMID: 34982152 DOI: 10.1242/jeb.229542] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Hibernators thrive under harsh environmental conditions instead of initiating canonical behavioral and physiological responses to promote survival. Although the physiological changes that occur during hibernation have been comprehensively researched, the role of the nervous system in this process remains relatively underexplored. In this Review, we adopt the perspective that the nervous system plays an active, essential role in facilitating and supporting hibernation. Accumulating evidence strongly suggests that the hypothalamus enters a quiescent state in which powerful drives to thermoregulate, eat and drink are suppressed. Similarly, cardiovascular and pulmonary reflexes originating in the brainstem are altered to permit the profoundly slow heart and breathing rates observed during torpor. The mechanisms underlying these changes to the hypothalamus and brainstem are not currently known, but several neuromodulatory systems have been implicated in the induction and maintenance of hibernation. The intersection of these findings with modern neuroscience approaches, such as optogenetics and in vivo calcium imaging, has opened several exciting avenues for hibernation research.
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Affiliation(s)
- Madeleine S Junkins
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
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7
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van Rosmalen L, Hut RA. Food and temperature change photoperiodic responses in two vole species. J Exp Biol 2021; 224:273462. [PMID: 34787302 DOI: 10.1242/jeb.243030] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 11/10/2021] [Indexed: 01/23/2023]
Abstract
Seasonal timing of reproduction in voles is driven by photoperiod. We hypothesized that a negative energy balance can modify spring-programmed photoperiodic responses in the hypothalamus, controlling reproductive organ development. We manipulated energy balance by the 'work-for-food' protocol, in which voles were exposed to increasing levels of food scarcity at different ambient temperatures under long photoperiod. We found that in common voles (Microtus arvalis) and tundra voles (Microtus oeconomus), photoperiod-induced pars tuberalis thyroid-stimulating hormone β-subunit (Tshβ) expression is reduced to potentially inhibit gonadal development when food is scarce. Reduction in gonadal size is more pronounced in tundra voles, in which anterior hypothalamic Kiss1 is additionally downregulated, especially in males. Low temperature additionally leads to decreased hypothalamic Rfrp expression, which potentially may facilitate further suppression of gonadal growth. Shutting off the photoperiodic axis when food is scarce in spring may be an adaptive response to save energy, leading to delayed reproductive organ development until food resources are sufficient for reproduction, lactation and offspring survival. Defining the mechanisms through which metabolic cues modify photoperiodic responses will be important for a better understanding of how environmental cues impact reproduction.
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Affiliation(s)
- Laura van Rosmalen
- Chronobiology Unit, Groningen Institute for Evolutionary Life Sciences, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Roelof A Hut
- Chronobiology Unit, Groningen Institute for Evolutionary Life Sciences, University of Groningen, 9747 AG Groningen, The Netherlands
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8
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Little AG. Thyroid hormone regulation of thermal acclimation in ectotherms: Physiological mechanisms and ecoevolutionary implications. Mol Cell Endocrinol 2021; 530:111285. [PMID: 33891994 DOI: 10.1016/j.mce.2021.111285] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 02/07/2021] [Accepted: 04/12/2021] [Indexed: 02/07/2023]
Abstract
The pathways that regulate adaptive thermal plasticity in ectothermic vertebrates have received little attention relative to those in birds and mammals. However, there is increasing evidence that thyroid hormone represents a critical regulator of thermal plasticity in both ectothermic and endothermic vertebrates. In this review, I summarize the evidence for thyroid hormone-mediated thermal compensation responses in ectothermic vertebrates, with specific focus on effects on the whole animal, skeletal muscle, and cardiac muscle. Interestingly, these effects can differ wildly between focal tissues and species. I move on to discuss what the role of thyroid hormone in ectotherm thermal plasticity can reveal about stressor interactions and central vs. peripheral levels of thyroid hormone regulation. Lastly, I focus on the conserved nature of thyroid hormone signaling in animal thermal responses, with specific reference to the ectotherm → endotherm spectrum. I use this framework to highlight research avenues that will further resolve the evolutionary trajectory of thyroid hormone actions across animals. I hope to emphasize what thyroid hormone-mediated cold acclimation in a 3 cm fish can contribute to ongoing debates surrounding the impacts of stressor interactions, the potential costs of plasticity, the evolution of endothermy, and the impacts of global change.
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Affiliation(s)
- A G Little
- Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
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9
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Bolborea M, Langlet F. What is the physiological role of hypothalamic tanycytes in metabolism? Am J Physiol Regul Integr Comp Physiol 2021; 320:R994-R1003. [PMID: 33826442 DOI: 10.1152/ajpregu.00296.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In vertebrates, the energy balance process is tightly controlled by complex neural circuits that sense metabolic signals and adjust food intake and energy expenditure in line with the physiological requirements of optimal conditions. Within neural networks controlling energy balance, tanycytes are peculiar ependymoglial cells that are nowadays recognized as multifunctional players in the metabolic hypothalamus. However, the physiological function of hypothalamic tanycytes remains unclear, creating a number of ambiguities in the field. Here, we review data accumulated over the years that demonstrate the physiological function of tanycytes in the maintenance of metabolic homeostasis, opening up new research avenues. The presumed involvement of tanycytes in the pathophysiology of metabolic disorders and age-related neurodegenerative diseases will be finally discussed.
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Affiliation(s)
- Matei Bolborea
- Central and Peripheral Mechanisms of Neurodegeneration, INSERM U1118, Université de Strasbourg, Strasbourg, France.,School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Fanny Langlet
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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10
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Ertek S. Molecular economy of nature with two thyrotropins from different parts of the pituitary: pars tuberalis thyroid-stimulating hormone and pars distalis thyroid-stimulating hormone. Arch Med Sci 2021; 17:189-195. [PMID: 33488871 PMCID: PMC7811323 DOI: 10.5114/aoms/102476] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 01/01/2019] [Indexed: 11/19/2022] Open
Abstract
Thyrotropin (TSH) is classically known to be regulated by negative feedback from thyroid hormones and stimulated by thyrotropin-releasing hormone (TRH) from the hypothalamus. At the end of the 1990s, studies showed that thyrotroph cells from the pars tuberalis (PT) did not have TRH receptors and their TSH regulation was independent from TRH stimulation. Instead, PT-thyrotroph cells were shown to have melatonin-1 (MT-1) receptors and melatonin secretion from the pineal gland stimulates TSH-β subunit formation in PT. Electron microscopy examinations also revealed some important differences between PT and pars distalis (PD) thyrotrophs. PT-TSH also have low bioactivity in the peripheral circulation. Studies showed that they have different glycosylations and PT-TSH forms macro-TSH complexes in the periphery and has a longer half-life. Photoperiodism affects LH levels in animals via decreased melatonin causing increased TSH-β subunit expression and induction of deiodinase-2 (DIO-2) in the brain. Mammals need a light stimulus carried into the suprachiasmatic nucleus (which is a circadian clock) and then transferred to the pineal gland to synthesize melatonin, but birds have deep brain receptors and they are stimulated directly by light stimuli to have increased PT-TSH, without the need for melatonin. Photoperiodic regulations via TSH and DIO 2/3 also have a role in appetite, seasonal immune regulation, food intake and nest-making behaviour in animals. Since humans have no clear seasonal breeding period, such studies as recent ''domestication locus'' studies in poultry are interesting. PT-TSH that works like a neurotransmitter in the brain may become an important target for future studies about humans.
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Affiliation(s)
- Sibel Ertek
- Department of Endocrinology and Metabolic Diseases, Memorial Ankara Hospital, Ankara, Turkey
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11
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Frare C, Williams CT, Drew KL. Thermoregulation in hibernating mammals: The role of the "thyroid hormones system". Mol Cell Endocrinol 2021; 519:111054. [PMID: 33035626 PMCID: PMC8091518 DOI: 10.1016/j.mce.2020.111054] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 07/15/2020] [Accepted: 10/04/2020] [Indexed: 12/19/2022]
Abstract
Hibernation is a unique evolutionary adaptation to conserve energy. During the pre-hibernation (i.e. fall) season, a progressive decline in core body temperature and further decrease in metabolism underlie a seasonal modulation in thermoregulation. The onset of hibernation requires marked changes in thermoregulatory attributes including adjustment in body temperature and tissue specific increases in thermogenic capacity. The hibernation season is characterized by a regulated suppression in thermogenesis allowing the onset of torpor interrupted by periodic activation of thermogenesis to sustain interbout arousals. Thyroid hormones are known to regulate both body temperature and metabolism, and for this reason, the hypothalamic-pituitary-thyroid axis and thyroid hormones have been investigated as modulators of thermogenesis in the phenomenon of hibernation, but the mechanisms remain poorly understood. In this review, we present an overview of what is known about the thermogenic roles of thyroid hormones in hibernating species across seasons and within the hibernating season (torpor-interbout arousal cycle). Overall, the hypothalamic-pituitary-thyroid axis and thyroid hormones play a role in the pre-hibernation season to enhance thermogenic capacity. During hibernation, thermogenesis is attenuated at the level of sympathetic premotor neurons within the raphe pallidus and by deiodinase expression in the hypothalamus. Further, as recent work highlights the direct effect of thyroid hormones within the central nervous system in activating thermogenesis, we speculate how similar mechanisms may occur in hibernating species to modulate thermogenesis across seasons and to sustain interbout arousals. However, further experiments are needed to elucidate the role of thyroid hormones in hibernation, moving towards the understanding that thyroid hormones metabolism, transport and availability within tissues may be the most telling indicator of thyroid status.
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Affiliation(s)
- C Frare
- Department of Chemistry and Biochemistry University of Alaska Fairbanks, Fairbanks, AK, 99775, USA; Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Cory T Williams
- Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA; Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Kelly L Drew
- Department of Chemistry and Biochemistry University of Alaska Fairbanks, Fairbanks, AK, 99775, USA; Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA.
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12
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Shi Z, Qin M, Huang L, Xu T, Chen Y, Hu Q, Peng S, Peng Z, Qu LN, Chen SG, Tuo QH, Liao DF, Wang XP, Wu RR, Yuan TF, Li YH, Liu XM. Human torpor: translating insights from nature into manned deep space expedition. Biol Rev Camb Philos Soc 2020; 96:642-672. [PMID: 33314677 DOI: 10.1111/brv.12671] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 11/09/2020] [Accepted: 11/17/2020] [Indexed: 12/12/2022]
Abstract
During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (Tb ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.
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Affiliation(s)
- Zhe Shi
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China.,Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China.,State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China.,Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200030, China
| | - Meng Qin
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China
| | - Lu Huang
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou, 510632, China
| | - Tao Xu
- Department of Anesthesiology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, China
| | - Ying Chen
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, 100700, China
| | - Qin Hu
- College of Life Sciences and Bio-Engineering, Beijing University of Technology, Beijing, 100024, China
| | - Sha Peng
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Zhuang Peng
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Li-Na Qu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Shan-Guang Chen
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Qin-Hui Tuo
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Duan-Fang Liao
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China
| | - Xiao-Ping Wang
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China
| | - Ren-Rong Wu
- National Clinical Research Center for Mental Disorders, and Department of Psychaitry, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China
| | - Ti-Fei Yuan
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200030, China.,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226000, China
| | - Ying-Hui Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Xin-Min Liu
- Key Laboratory for Quality Evaluation of Bulk Herbs of Hunan Province, Hunan University of Chinese Medicine, Changsha, Hunan, 410208, China.,State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China.,Research Center for Pharmacology and Toxicology, Institute of Medicinal Plant Development (IMPLAD), Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100193, China
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13
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Valle S, Das C, Meddle SL, Deviche P. The effect of food restriction on the regulation of gonadotropin-releasing hormone in male house finches (Haemorhous mexicanus). Gen Comp Endocrinol 2019; 282:113196. [PMID: 31163182 DOI: 10.1016/j.ygcen.2019.05.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 05/15/2019] [Accepted: 05/31/2019] [Indexed: 01/02/2023]
Abstract
Seasonal activation of the vertebrate hypothalamic-pituitary-gonadal (HPG) axis and gonadal development is initiated by gonadotropin-releasing hormone-I (GnRH) release from the hypothalamus. In photoperiodic species, the consistent annual change in photoperiod is the primary environmental signal affecting GnRH cell activity, including changes in the synthesis and secretion of this neuropeptide. Non-photoperiodic environmental cues such as energy availability also influence HPG axis activity, but the mechanisms mediating this influence, in particular on the GnRH system, are unclear. Understanding how the neuroendocrine system integrates environmental information is critical in determining the plasticity and adaptability of physiological responses to changing environments. The primary objective of this study was to investigate GnRH-mediated changes in HPG axis activity and gonadal development in response to energy availability in a wild bird. We hypothesized that negative energy balance inhibits HPG axis activity by affecting GnRH secretion. Moderate food restriction for several weeks in male house finches, Haemorhous mexicanus, decreased body condition and inhibited photoinduced testicular growth compared to birds fed ad libitum. Food restriction did not affect plasma luteinizing hormone (LH; a correlate of GnRH release) or plasma testosterone, but it enhanced the plasma LH response to an injection of the glutamatergic agonist, N-methyl-D-aspartate (NMDA). Thus, food restriction may decrease photoinduced HPG axis activation by acting centrally, in particular by attenuating the release of accumulated GnRH stores.
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Affiliation(s)
- Shelley Valle
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
| | - Chandrima Das
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | - Simone L Meddle
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian EH25 9RG, Scotland, UK
| | - Pierre Deviche
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
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14
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Bao R, Onishi KG, Tolla E, Ebling FJP, Lewis JE, Anderson RL, Barrett P, Prendergast BJ, Stevenson TJ. Genome sequencing and transcriptome analyses of the Siberian hamster hypothalamus identify mechanisms for seasonal energy balance. Proc Natl Acad Sci U S A 2019; 116:13116-13121. [PMID: 31189592 PMCID: PMC6600942 DOI: 10.1073/pnas.1902896116] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Synthesis of triiodothyronine (T3) in the hypothalamus induces marked seasonal neuromorphology changes across taxa. How species-specific responses to T3 signaling in the CNS drive annual changes in body weight and energy balance remains uncharacterized. These experiments sequenced and annotated the Siberian hamster (Phodopus sungorus) genome, a model organism for seasonal physiology research, to facilitate the dissection of T3-dependent molecular mechanisms that govern predictable, robust, and long-term changes in body weight. Examination of the Phodopus genome, in combination with transcriptome sequencing of the hamster diencephalon under winter and summer conditions, and in vivo-targeted expression analyses confirmed that proopiomelanocortin (pomc) is a primary genomic target for the long-term T3-dependent regulation of body weight. Further in silico analyses of pomc promoter sequences revealed that thyroid hormone receptor 1β-binding motif insertions have evolved in several genera of the Cricetidae family of rodents. Finally, experimental manipulation of food availability confirmed that hypothalamic pomc mRNA expression is dependent on longer-term photoperiod cues and is unresponsive to acute, short-term food availability. These observations suggest that species-specific responses to hypothalamic T3, driven in part by the receptor-binding motif insertions in some cricetid genomes, contribute critically to the long-term regulation of energy balance and the underlying physiological and behavioral adaptations associated with the seasonal organization of behavior.
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Affiliation(s)
- Riyue Bao
- Center for Research Informatics, University of Chicago, Chicago, IL 60637
- Department of Pediatrics, University of Chicago, Chicago, IL 60637
| | - Kenneth G Onishi
- Institute for Mind and Biology, University of Chicago, Chicago, IL 60637
| | - Elisabetta Tolla
- Institute for Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G61 1QH, United Kingdom
| | - Fran J P Ebling
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
| | - Jo E Lewis
- Institute of Metabolic Sciences, University of Cambridge, Cambridge CB2 0QQ, United Kingdom
| | - Richard L Anderson
- Rowett Institute, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Perry Barrett
- Rowett Institute, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Brian J Prendergast
- Institute for Mind and Biology, University of Chicago, Chicago, IL 60637
- Department of Psychology, University of Chicago, Chicago, IL 60637
| | - Tyler J Stevenson
- Institute for Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G61 1QH, United Kingdom;
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15
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Helfer G, Barrett P, Morgan PJ. A unifying hypothesis for control of body weight and reproduction in seasonally breeding mammals. J Neuroendocrinol 2019; 31:e12680. [PMID: 30585661 DOI: 10.1111/jne.12680] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/18/2018] [Accepted: 12/21/2018] [Indexed: 02/06/2023]
Abstract
Animals have evolved diverse seasonal variations in physiology and reproduction to accommodate yearly changes in environmental and climatic conditions. These changes in physiology are initiated by changes in photoperiod (daylength) and are mediated through melatonin, which relays photoperiodic information to the pars tuberalis of the pituitary gland. Melatonin drives thyroid-stimulating hormone transcription and synthesis in the pars tuberalis, which, in turn, regulates thyroid hormone and retinoic acid synthesis in the tanycytes lining the third ventricle of the hypothalamus. Seasonal variation in central thyroid hormone signalling is conserved among photoperiodic animals. Despite this, different species adopt divergent phenotypes to cope with the same seasonal changes. A common response amongst different species is increased hypothalamic cell proliferation/neurogenesis in short photoperiod. That cell proliferation/neurogenesis may be important for seasonal timing is based on (i) the neurogenic potential of tanycytes; (ii) the fact that they are the locus of striking seasonal morphological changes; and (iii) the similarities to mechanisms involved in de novo neurogenesis of energy balance neurones. We propose that a decrease in hypothalamic thyroid hormone and retinoic acid signalling initiates localised neurodegeneration and apoptosis, which leads to a reduction in appetite and body weight. Neurodegeneration induces compensatory cell proliferation from the neurogenic niche in tanycytes and new cells are born under short photoperiod. Because these cells have the potential to differentiate into a number of different neuronal phenotypes, this could provide a mechanistic basis to explain the seasonal regulation of energy balance, as well as reproduction. This cycle can be achieved without changes in thyroid hormone/retinoic acid and explains recent data obtained from seasonal animals held in natural conditions. However, thyroid/retinoic acid signalling is required to synchronise the cycles of apoptosis, proliferation and differentiation. Thus, hypothalamic neurogenesis provides a framework to explain diverse photoperiodic responses.
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Affiliation(s)
- Gisela Helfer
- School of Chemistry and Biosciences, University of Bradford, Bradford, UK
| | - Perry Barrett
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - Peter J Morgan
- Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK
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16
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Abstract
Organisms use changes in photoperiod for seasonal reproduction to maximize the survival of their offspring. Birds have sophisticated seasonal mechanisms and are therefore excellent models for studying these phenomena. Birds perceive light via deep-brain photoreceptors and long day–induced thyroid-stimulating hormone (TSH, thyrotropin) in the pars tuberalis of the pituitary gland (PT), which cause local thyroid hormone activation within the mediobasal hypothalamus. The local bioactive thyroid hormone controls seasonal gonadotropin-releasing hormone secretion and subsequent gonadotropin secretion. In mammals, the eyes are believed to be the only photoreceptor organ, and nocturnal melatonin secretion triggers an endocrine signal that communicates information about the photoperiod to the PT to regulate TSH. In contrast, in Salmonidae fish the input pathway to the neuroendocrine output pathway appears to be localized in the saccus vasculosus. Thus, comparative analysis is an effective way to uncover the universality and diversity of fundamental traits in various organisms.
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Affiliation(s)
- Yusuke Nakane
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Laboratory of Animal Integrative Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Takashi Yoshimura
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Laboratory of Animal Integrative Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
- Division of Seasonal Biology, National Institute for Basic Biology, Myodaiji, Okazaki 444-8585, Japan
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17
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Frare C, Jenkins ME, Soldin SJ, Drew KL. The Raphe Pallidus and the Hypothalamic-Pituitary-Thyroid Axis Gate Seasonal Changes in Thermoregulation in the Hibernating Arctic Ground Squirrel ( Urocitellus parryii). Front Physiol 2018; 9:1747. [PMID: 30618783 PMCID: PMC6299024 DOI: 10.3389/fphys.2018.01747] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/20/2018] [Indexed: 01/17/2023] Open
Abstract
Thermoregulation is necessary to maintain energy homeostasis. The novel discovery of brown adipose tissue (BAT) in humans has increased research interests in better understanding BAT thermogenesis to restore energy balance in metabolic disorders. The hibernating Arctic ground squirrel (AGS) offers a novel approach to investigate BAT thermogenesis. AGS seasonally increase their BAT mass to increase the ability to generate heat during interbout arousals. The mechanisms promoting the seasonal changes in BAT thermogenesis are not well understood. BAT thermogenesis is regulated by the raphe pallidus (rPA) and by thyroid hormones produced by the hypothalamic–pituitary–thyroid (HPT) axis. Here, we investigate if the HPT axis and the rPA undergo seasonal changes to modulate BAT thermogenesis in hibernation. We used histological analysis and tandem mass spectrometry to assess activation of the HPT axis and immunohistochemistry to measure neuronal activation. We found an increase in HPT axis activation in fall and in response to pharmacologically induced torpor when adenosine A1 receptor agonist was administered in winter. By contrast, the rPA neuronal activation was lower in winter in response to pharmacologically induced torpor. Activation of the rPA was also lower in winter compared to the other seasons. Our results suggest that thermogenic capacity develops during fall as the HPT axis is activated to reach maximum capacity in winter seen by increased free thyroid hormones in response to cooling. However, thermogenesis is inhibited during torpor as sympathetic premotor neuronal activation is lower in winter, until arousal when inhibition of thermogenesis is relieved. These findings describe seasonal modulation of thermoregulation that conserves energy through attenuated sympathetic drive, but retains heat generating capacity through activation of the HPT axis.
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Affiliation(s)
- Carla Frare
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Mackenzie E Jenkins
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Steven J Soldin
- National Institutes of Health Clinical Center, Bethesda, MD, United States.,Division of Endocrinology and Metabolism, Department of Medicine, Georgetown University, Washington, DC, United States
| | - Kelly L Drew
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, United States
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18
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Ebling FJP, Lewis JE. Tanycytes and hypothalamic control of energy metabolism. Glia 2018; 66:1176-1184. [DOI: 10.1002/glia.23303] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 12/21/2017] [Accepted: 01/23/2018] [Indexed: 01/15/2023]
Affiliation(s)
- Francis J. P. Ebling
- School of Life Sciences; University of Nottingham Medical School, Queen's Medical Centre; Nottingham NG7 2UH United Kingdom
| | - Jo E. Lewis
- School of Life Sciences; University of Nottingham Medical School, Queen's Medical Centre; Nottingham NG7 2UH United Kingdom
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19
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Cubuk C, Markowsky H, Herwig A. Hypothalamic control systems show differential gene expression during spontaneous daily torpor and fasting-induced torpor in the Djungarian hamster (Phodopus sungorus). PLoS One 2017; 12:e0186299. [PMID: 29023516 PMCID: PMC5638525 DOI: 10.1371/journal.pone.0186299] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 09/28/2017] [Indexed: 12/25/2022] Open
Abstract
Djungarian hamsters are able to use spontaneous daily torpor (SDT) during the winter season as well as fasting-induced torpor (FIT) at any time of the year to cope with energetically challenging environmental conditions. Torpor is a state of severely reduced metabolism with a pronounced decrease in body temperature, which enables animals to decrease their individual energy requirements. Despite sharing common characteristics, such as reduced body mass before first torpor expression and depressed metabolism and body temperature during the torpid state, FIT and SDT differ in several physiological properties including torpor bout duration, minimal body temperature, fuel utilization and circadian organization. It remains unclear, whether SDT and FIT reflect the same phenomenon or two different physiological states. The hypothalamus has been suggested to play a key role in regulating energy balance and torpor. To uncover differences in molecular control mechanisms of torpor expression, we set out to investigate hypothalamic gene expression profiles of genes related to orexigenic (Agrp/Npy), circadian clock (Bmal1/Per1) and thyroid hormone (Dio2/Mct8) systems of animals undergoing SDT and FIT during different torpor stages. Orexigenic genes were mainly regulated during FIT and remained largely unaffected by SDT. Expression patterns of clock genes showed disturbed circadian clock rhythmicity in animals undergoing FIT, but not in animals undergoing SDT. During both, SDT and FIT, decreased Dio2 expression was detected, indicating reduced hypothalamic T3 availability in both types of torpor. Taken together, our results provide evidence that SDT and FIT also differ in certain central control mechanisms and support the observation that animals undergoing SDT are in energetical balance, whereas animals undergoing FIT display a negative energy balance. This should be carefully taken into account when interpreting data in torpor research, especially from animal models of fasting-induced hypometabolism such as mice.
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Affiliation(s)
- Ceyda Cubuk
- Zoologisches Institut, Universität Hamburg, Hamburg, Germany
| | - Hanna Markowsky
- Zoologisches Institut, Universität Hamburg, Hamburg, Germany
| | - Annika Herwig
- Institut für Neurobiologie, Universität Ulm, Ulm, Germany
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20
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Bank JHH, Wilson D, Rijntjes E, Barrett P, Herwig A. Alternation between short- and long photoperiod reveals hypothalamic gene regulation linked to seasonal body weight changes in Djungarian hamsters (Phodopus sungorus). J Neuroendocrinol 2017; 29. [PMID: 28514514 DOI: 10.1111/jne.12487] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 04/10/2017] [Accepted: 05/14/2017] [Indexed: 01/28/2023]
Abstract
Djungarian hamsters are able to reduce their body weight by more than 30% in anticipation of the winter season. This particular adaptation to extreme environmental conditions is primarily driven by a natural reduction in day length and conserved under laboratory conditions. We used this animal model to investigate hypothalamic gene expression linked to body weight regulation behind this physiological phenomenon. After an initial collective short photoperiod (SP) adaptation for 14 weeks from a preceding long photoperiod (LP), hamsters were re-exposed to LP for either 6 or 14 weeks, followed by a second re-exposure to SP for 8 weeks. Our data showed that re-exposure to LP led to an increase in body weight. In the hypothalamus Dio2, Vimentin, Crbp1 and Grp50 expression increased, whereas expression of Dio3, Mct8 and Srif decreased. The changes in body weight and gene expression were reversible in most hamsters after a further re-exposure to SP following 6 or 14 weeks in LP. Interestingly, after 14 weeks in LP, body weight loss was pronounced in six hamsters re-exposed to SP, but five hamsters did not respond. In nonresponding hamsters, a different gene expression pattern was manifested, with the exception of Dio2, which was reduced not only in SP re-exposed hamsters, but also in hamsters maintained in LP. Taken together, these data suggest that body weight regulation appears to be tightly linked to a co-ordinated regulation of several genes in the hypothalamus, including those involved in thyroid hormone metabolism.
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Affiliation(s)
- J H H Bank
- Zoologisches Institut, Universität Hamburg, Hamburg, Germany
| | - D Wilson
- The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - E Rijntjes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - P Barrett
- The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - A Herwig
- Zoologisches Institut, Universität Hamburg, Hamburg, Germany
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21
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Bank JHH, Cubuk C, Wilson D, Rijntjes E, Kemmling J, Markovsky H, Barrett P, Herwig A. Gene expression analysis and microdialysis suggest hypothalamic triiodothyronine (T3) gates daily torpor in Djungarian hamsters (Phodopus sungorus). J Comp Physiol B 2017; 187:857-868. [PMID: 28365894 DOI: 10.1007/s00360-017-1086-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 01/19/2017] [Accepted: 03/07/2017] [Indexed: 11/30/2022]
Abstract
Thyroid hormones play an important role in regulating seasonal adaptations of mammals. Several studies suggested that reduced availability of 3,3',5-triiodothyronine (T3) in the hypothalamus is required for the physiological adaptation to winter in Djungarian hamsters. We have previously shown that T3 is involved in the regulation of daily torpor, but it remains unclear, whether T3 affects torpor by central or peripheral mechanisms. To determine the effect of T3 concentrations within the hypothalamus in regulating daily torpor, we tested the hypothesis that low hypothalamic T3 metabolism would favour torpor and high T3 concentrations would not. In experiment 1 gene expression in torpid hamsters was assessed for transporters carrying thyroid hormones between cerebrospinal fluid and hypothalamic cells and for deiodinases enzymes, activating or inactivating T3 within hypothalamic cells. Gene expression analysis suggests reduced T3 in hypothalamic cells during torpor. In experiment 2, hypothalamic T3 concentrations were altered via microdialysis and torpor behaviour was continuously monitored by implanted body temperature transmitters. Increased T3 concentrations in the hypothalamus reduced expression of torpor as well as torpor bout duration and depth. Subsequent analysis of gene expression in the ependymal layer of the third ventricle showed clear up-regulation of T3 inactivating deiodinase 3 but no changes in several other genes related to photoperiodic adaptations in hamsters. Finally, serum analysis revealed that increased total T3 serum concentrations were not necessary to inhibit torpor expression. Taken together, our results are consistent with the hypothesis that T3 availability within the hypothalamus significantly contributes to the regulation of daily torpor via a central pathway.
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Affiliation(s)
- Jonathan H H Bank
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| | - Ceyda Cubuk
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| | - Dana Wilson
- The Rowett Institute, University of Aberdeen, Bucksburn, Aberdeen, UK
| | - Eddy Rijntjes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
| | - Julia Kemmling
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| | - Hanna Markovsky
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany
| | - Perry Barrett
- The Rowett Institute, University of Aberdeen, Bucksburn, Aberdeen, UK
| | - Annika Herwig
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146, Hamburg, Germany.
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22
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Lewis JE, Ebling FJP. Tanycytes As Regulators of Seasonal Cycles in Neuroendocrine Function. Front Neurol 2017; 8:79. [PMID: 28344570 PMCID: PMC5344904 DOI: 10.3389/fneur.2017.00079] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 02/20/2017] [Indexed: 12/31/2022] Open
Abstract
Annual cycles of physiology and behavior are highly prevalent in organisms inhabiting temperate and polar regions. Examples in mammals include changes in appetite and body fat composition, hibernation and torpor, growth of antlers, pelage and horns, and seasonal reproduction. The timing of these seasonal cycles reflects an interaction of changing environmental signals, such as daylength, and intrinsic rhythmic processes: circannual clocks. As neuroendocrine signals underlie these rhythmic processes, the focus of most mechanistic studies has been on neuronal systems in the hypothalamus. Recent studies also implicate the pituitary stalk (pars tuberalis) and hypothalamic tanycytes as key pathways in seasonal timing. The pars tuberalis expresses a high density of melatonin receptors, so is highly responsive to changes in the nocturnal secretion of melatonin from the pineal gland as photoperiod changes across the year. The pars tuberalis in turn regulates tanycyte function in the adjacent hypothalamus via paracrine signals. Tanycytes are radial glial cells that persist into adulthood and function as a stem cell niche. Their cell soma are embedded in the ependymal lining of the third ventricle, and they also send elaborate projections through the arcuate nucleus, many of which terminate on capillaries in the median eminence. This anatomy underlies their function as sensors of nutrients in the circulation, and as regulators of transport of hormones and metabolites into the hypothalamus. In situ hybridization studies reveal robust seasonal changes in gene expression in tanycytes, for example, those controlling transport and metabolism of thyroid hormone and retinoic acid. These hormonal signals play a key role in the initial development of the brain, and experimental manipulation of thyroid hormone availability in the adult hypothalamus can accelerate or block seasonal cyclicity in sheep and Siberian hamsters. We hypothesize that seasonal rhythms depends upon reuse of developmental mechanisms in the adult hypothalamus and that tanycytes are key orchestrators of these processes.
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Affiliation(s)
- Jo E Lewis
- School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre , Nottingham , UK
| | - Francis J P Ebling
- School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre , Nottingham , UK
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Petri I, Diedrich V, Wilson D, Fernández-Calleja J, Herwig A, Steinlechner S, Barrett P. Orchestration of gene expression across the seasons: Hypothalamic gene expression in natural photoperiod throughout the year in the Siberian hamster. Sci Rep 2016; 6:29689. [PMID: 27406810 PMCID: PMC4942572 DOI: 10.1038/srep29689] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 06/23/2016] [Indexed: 01/17/2023] Open
Abstract
In nature Siberian hamsters utilize the decrement in day length following the summer solstice to implement physiological adaptations in anticipation of the forthcoming winter, but also exploit an intrinsic interval timer to initiate physiological recrudescence following the winter solstice. However, information is lacking on the temporal dynamics in natural photoperiod of photoperiodically regulated genes and their relationship to physiological adaptations. To address this, male Siberian hamsters born and maintained outdoors were sampled every month over the course of one year. As key elements of the response to photoperiod, thyroid hormone signalling components were assessed in the hypothalamus. From maximum around the summer solstice (late-June), Dio2 expression rapidly declined in advance of physiological adaptations. This was followed by a rapid increase in Mct8 expression (T3/T4 transport), peaking early-September before gradually declining to minimum expression by the following June. Dio3 showed a transient peak of expression beginning late-August. A recrudescence of testes and body mass occurred from mid-February, but Dio2 expression remained low until late-April of the following year, converging with the time of year when responsiveness to short-day length is re-established. Other photoperiodically regulated genes show temporal regulation, but of note is a transient peak in Gpr50 around late-July.
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Affiliation(s)
- Ines Petri
- University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
| | - Victoria Diedrich
- University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
| | - Dana Wilson
- Rowett Institute for Nutrition and Health, University of Aberdeen, Greenburn Road Bucksburn, Aberdeen AB21 9SB, UK
| | - José Fernández-Calleja
- Rowett Institute for Nutrition and Health, University of Aberdeen, Greenburn Road Bucksburn, Aberdeen AB21 9SB, UK
| | - Annika Herwig
- Zoological Institute, University of Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany
| | - Stephan Steinlechner
- University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
| | - Perry Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Greenburn Road Bucksburn, Aberdeen AB21 9SB, UK
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Ortiga-Carvalho TM, Chiamolera MI, Pazos-Moura CC, Wondisford FE. Hypothalamus-Pituitary-Thyroid Axis. Compr Physiol 2016; 6:1387-428. [PMID: 27347897 DOI: 10.1002/cphy.c150027] [Citation(s) in RCA: 222] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.
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Affiliation(s)
- Tania M Ortiga-Carvalho
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Maria I Chiamolera
- Department of Medicine, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
| | - Carmen C Pazos-Moura
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Fredic E Wondisford
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA
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25
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Nishiwaki-Ohkawa T, Yoshimura T. Molecular basis for regulating seasonal reproduction in vertebrates. J Endocrinol 2016; 229:R117-27. [PMID: 27068698 DOI: 10.1530/joe-16-0066] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 04/11/2016] [Indexed: 12/31/2022]
Abstract
Animals that inhabit mid- to high-latitude regions exhibit various adaptive behaviors, such as migration, reproduction, molting and hibernation in response to seasonal cues. These adaptive behaviors are tightly regulated by seasonal changes in photoperiod, the relative day length vs night length. Recently, the regulatory pathway of seasonal reproduction has been elucidated using quail. In birds, deep brain photoreceptors receive and transmit light information to the pars tuberalis in the pituitary gland, which induces the secretion of thyroid-stimulating hormone. Thyroid-stimulating hormone locally activates thyroid hormone via induction of type 2 deiodinase in the mediobasal hypothalamus. Thyroid hormone then induces morphological changes in the terminals of neurons that express gonadotropin-releasing hormone and facilitates gonadotropin secretion from the pituitary gland. In mammals, light information is received by photoreceptors in the retina and neurally transmitted to the pineal gland, where it inhibits the synthesis and secretion of melatonin, which is crucial for seasonal reproduction. Importantly, the signaling pathway downstream of light detection and signaling is fully conserved between mammals and birds. In fish, the regulatory components of seasonal reproduction are integrated, from light detection to neuroendocrine output, in a fish-specific organ called the saccus vasculosus. Various physiological processes in humans are also influenced by seasonal environmental changes. The findings discussed herein may provide clues to addressing human diseases, such as seasonal affective disorder.
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Affiliation(s)
- Taeko Nishiwaki-Ohkawa
- Laboratory of Animal PhysiologyGraduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan Institute of Transformative Bio-Molecules (WPI-ITbM)Nagoya University, Nagoya, Japan
| | - Takashi Yoshimura
- Laboratory of Animal PhysiologyGraduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan Institute of Transformative Bio-Molecules (WPI-ITbM)Nagoya University, Nagoya, Japan Division of Seasonal BiologyNational Institute for Basic Biology, Okazaki, Japan Avian Bioscience Research CenterGraduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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26
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Little AG. A review of the peripheral levels of regulation by thyroid hormone. J Comp Physiol B 2016; 186:677-88. [DOI: 10.1007/s00360-016-0984-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 03/23/2016] [Accepted: 03/29/2016] [Indexed: 12/12/2022]
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27
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Lewis JE, Brameld JM, Hill P, Wilson D, Barrett P, Ebling FJP, Jethwa PH. Thyroid hormone and vitamin D regulate VGF expression and promoter activity. J Mol Endocrinol 2016; 56:123-34. [PMID: 26643910 PMCID: PMC4705542 DOI: 10.1530/jme-15-0224] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/03/2015] [Indexed: 01/20/2023]
Abstract
The Siberian hamster (Phodopus sungorus) survives winter by decreasing food intake and catabolizing abdominal fat reserves, resulting in a sustained, profound loss of body weight. Hypothalamic tanycytes are pivotal for this process. In these cells, short-winter photoperiods upregulate deiodinase 3, an enzyme that regulates thyroid hormone availability, and downregulate genes encoding components of retinoic acid (RA) uptake and signaling. The aim of the current studies was to identify mechanisms by which seasonal changes in thyroid hormone and RA signaling from tanycytes might ultimately regulate appetite and energy expenditure. proVGF is one of the most abundant peptides in the mammalian brain, and studies have suggested a role for VGF-derived peptides in the photoperiodic regulation of body weight in the Siberian hamster. In silico studies identified possible thyroid and vitamin D response elements in the VGF promoter. Using the human neuroblastoma SH-SY5Y cell line, we demonstrate that RA increases endogenous VGF expression (P<0.05) and VGF promoter activity (P<0.0001). Similarly, treatment with 1,25-dihydroxyvitamin D3 increased endogenous VGF mRNA expression (P<0.05) and VGF promoter activity (P<0.0001), whereas triiodothyronine (T3) decreased both (P<0.01 and P<0.0001). Finally, intra-hypothalamic administration of T3 blocked the short day-induced increase in VGF expression in the dorsomedial posterior arcuate nucleus of Siberian hamsters. Thus, we conclude that VGF expression is a likely target of photoperiod-induced changes in tanycyte-derived signals and is potentially a regulator of seasonal changes in appetite and energy expenditure.
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Affiliation(s)
- Jo E Lewis
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - John M Brameld
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - Phil Hill
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - Dana Wilson
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - Perry Barrett
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - Francis J P Ebling
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
| | - Preeti H Jethwa
- Division of Nutritional SciencesSchool of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UKSchool of Life SciencesUniversity of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UKThe Rowett Institute of Nutrition and HealthUniversity of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK
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28
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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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29
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Antibody-Mediated Inhibition of the FGFR1c Isoform Induces a Catabolic Lean State in Siberian Hamsters. Curr Biol 2015; 25:2997-3003. [PMID: 26549257 DOI: 10.1016/j.cub.2015.10.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/01/2015] [Accepted: 10/05/2015] [Indexed: 11/24/2022]
Abstract
Hypothalamic tanycytes are considered to function as sensors of peripheral metabolism. To facilitate this role, they express a wide range of receptors, including fibroblast growth factor receptor 1 (FGFR1). Using a monoclonal antibody (IMC-H7) that selectively antagonizes the FGFR1c isoform, we investigated possible actions of FGFR1c in a natural animal model of adiposity, the Siberian hamster. Infusion of IMC-H7 into the third ventricle suppressed appetite and increased energy expenditure. Likewise, peripheral treatment with IMC-H7 decreased appetite and body weight and increased energy expenditure and fat oxidation. A greater reduction in body weight and caloric intake was observed in response to IMC-H7 during the long-day fat state as compared to the short-day lean state. This enhanced response to IMC-H7 was also observed in calorically restricted hamsters maintained in long days, suggesting that it is the central photoperiodic state rather than the peripheral adiposity that determines the response to FGFR1c antagonism. Hypothalamic thyroid hormone availability is controlled by deiodinase enzymes (DIO2 and DIO3) expressed in tanycytes and is the key regulator of seasonal cycles of energy balance. Therefore, we determined the effect of IMC-H7 on hypothalamic expression of these deiodinase enzymes. The reductions in food intake and body weight were always associated with decreased expression of DIO2 in the hypothalamic ependymal cell layer containing tanycytes. These data provide further support for the notion the tanycytes are an important component of the mechanism by which the hypothalamus integrates central and peripheral signals to regulate energy intake and expenditure.
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30
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Bank JHH, Kemmling J, Rijntjes E, Wirth EK, Herwig A. Thyroid hormone status affects expression of daily torpor and gene transcription in Djungarian hamsters (Phodopus sungorus). Horm Behav 2015; 75:120-9. [PMID: 26435475 DOI: 10.1016/j.yhbeh.2015.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 09/18/2015] [Accepted: 09/30/2015] [Indexed: 12/30/2022]
Abstract
Thyroid hormones (TH) play a key role in regulation of seasonal as well as acute changes in metabolism. Djungarian hamsters (Phodopus sungorus) adapt to winter by multiple changes in behaviour and physiology including spontaneous daily torpor, a state of hypometabolism and hypothermia. We investigated effects of systemic TH administration and ablation on the torpor behaviour in Djungarian hamsters adapted to short photoperiod. Hyperthyroidism was induced by giving T4 or T3 and hypothyroidism by giving methimazole (MMI) and sodium perchlorate via drinking water. T3 treatment increased water, food intake and body mass, whereas MMI had the opposite effect. Continuous recording of body temperature revealed that low T3 serum concentrations increased torpor incidence, lowered Tb and duration, whereas high T3 serum concentrations inhibited torpor expression. Gene expression of deiodinases (dio) and uncoupling proteins (ucp) were analysed by qPCR in hypothalamus, brown adipose tissue (BAT) and skeletal muscle. Expression of dio2, the enzyme generating T3 by deiodination of T4, and ucps, involved in thermoregulation, indicated a tissue specific response to treatment. Torpor per se decreased dio2 expression irrespective of treatment or tissue, suggesting low intracellular T3 concentrations during torpor. Down regulation of ucp1 and ucp3 during torpor might be a factor for the inhibition of BAT thermogenesis. Hypothalamic gene expression of neuropeptide Y, propopiomelanocortin and somatostatin, involved in feeding behaviour and energy balance, were not affected by treatment. Taken together our data indicate a strong effect of thyroid hormones on torpor, suggesting that lowered intracellular T3 concentrations in peripheral tissues promote torpor.
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Affiliation(s)
- Jonathan H H Bank
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany
| | - Julia Kemmling
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany
| | - Eddy Rijntjes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Eva K Wirth
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Annika Herwig
- Biozentrum Grindel und Zoologisches Museum, Universität Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany.
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31
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Bolborea M, Helfer G, Ebling FJP, Barrett P. Dual signal transduction pathways activated by TSH receptors in rat primary tanycyte cultures. J Mol Endocrinol 2015; 54:241-50. [PMID: 25878058 DOI: 10.1530/jme-14-0298] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Tanycytes play multiple roles in hypothalamic functions, including sensing peripheral nutrients and metabolic hormones, regulating neurosecretion and mediating seasonal cycles of reproduction and metabolic physiology. This last function reflects the expression of TSH receptors in tanycytes, which detect photoperiod-regulated changes in TSH secretion from the neighbouring pars tuberalis. The present overall aim was to determine the signal transduction pathway by which TSH signals in tanycytes. Expression of the TSH receptor in tanycytes of 10-day-old Sprague Dawley rats was observed by in situ hybridisation. Primary ependymal cell cultures prepared from 10-day-old rats were found by immunohistochemistry to express vimentin but not GFAP and by PCR to express mRNA for Dio2, Gpr50, Darpp-32 and Tsh receptors that are characteristic of tanycytes. Treatment of primary tanycyte/ependymal cultures with TSH (100 IU/l) increased cAMP as assessed by ELISA and induced a cAMP-independent increase in the phosphorylation of ERK1/2 as assessed by western blot analysis. Furthermore, TSH (100 IU/l) stimulated a 2.17-fold increase in Dio2 mRNA expression. We conclude that TSH signal transduction in cultured tanycytes signals via Gαs to increase cAMP and via an alternative G protein to increase phosphorylation of ERK1/2.
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Affiliation(s)
- Matei Bolborea
- Rowett Institute of Nutrition and Health University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK School of Life Sciences University of Nottingham Medical School, Nottingham NG7 2UH, UK Rowett Institute of Nutrition and Health University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK School of Life Sciences University of Nottingham Medical School, Nottingham NG7 2UH, UK
| | - Gisela Helfer
- Rowett Institute of Nutrition and Health University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK School of Life Sciences University of Nottingham Medical School, Nottingham NG7 2UH, UK
| | - Francis J P Ebling
- Rowett Institute of Nutrition and Health University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK School of Life Sciences University of Nottingham Medical School, Nottingham NG7 2UH, UK
| | - Perry Barrett
- Rowett Institute of Nutrition and Health University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK School of Life Sciences University of Nottingham Medical School, Nottingham NG7 2UH, UK
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Tavolaro FM, Thomson LM, Ross AW, Morgan PJ, Helfer G. Photoperiodic effects on seasonal physiology, reproductive status and hypothalamic gene expression in young male F344 rats. J Neuroendocrinol 2015; 27:79-87. [PMID: 25443173 PMCID: PMC4329330 DOI: 10.1111/jne.12241] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 11/14/2014] [Accepted: 11/25/2014] [Indexed: 12/15/2022]
Abstract
Seasonal or photoperiodically sensitive animals respond to altered day length with changes in physiology (growth, food intake and reproductive status) and behaviour to adapt to predictable yearly changes in the climate. Typically, different species of hamsters, voles and sheep are the most studied animal models of photoperiodism. Although laboratory rats are generally considered nonphotoperiodic, one rat strain, the inbred Fischer 344 (F344) rat, has been shown to be sensitive to the length of daylight exposure by changing its physiological phenotype and reproductive status according to the season. The present study aimed to better understand the nature of the photoperiodic response in the F344 rat. We examined the effects of five different photoperiods on the physiological and neuroendocrine responses. Young male F344 rats were held under light schedules ranging from 8 h of light/day to 16 h of light/day, and then body weight, including fat and lean mass, food intake, testes weights and hypothalamic gene expression were compared. We found that rats held under photoperiods of ≥ 12 h of light/day showed increased growth and food intake relative to rats held under photoperiods of ≤ 10 h of light/day. Magnetic resonance imaging analysis confirmed that these changes were mainly the result of a change in lean body mass. The same pattern was evident for reproductive status, with higher paired testes weight in photoperiods of ≥ 12 h of light/day. Accompanying the changes in physiological status were major changes in hypothalamic thyroid hormone (Dio2 and Dio3), retinoic acid (Crabp1 and Stra6) and Wnt/β-Catenin signalling genes (sFrp2 and Mfrp). Our data demonstrate that a photoperiod schedule of 12 h of light/day is interpreted as a stimulatory photoperiod by the neuroendocrine system of young male F344 rats.
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Affiliation(s)
- F M Tavolaro
- Rowett Institute of Nutrition and Health, University of AberdeenAberdeen, UK
| | - L M Thomson
- Rowett Institute of Nutrition and Health, University of AberdeenAberdeen, UK
| | - A W Ross
- Rowett Institute of Nutrition and Health, University of AberdeenAberdeen, UK
| | - P J Morgan
- Rowett Institute of Nutrition and Health, University of AberdeenAberdeen, UK
| | - G Helfer
- Rowett Institute of Nutrition and Health, University of AberdeenAberdeen, UK
- Correspondence to: Gisela Helfer, Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK (e-mail: )
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Herwig A, Campbell G, Mayer CD, Boelen A, Anderson RA, Ross AW, Mercer JG, Barrett P. A thyroid hormone challenge in hypothyroid rats identifies T3 regulated genes in the hypothalamus and in models with altered energy balance and glucose homeostasis. Thyroid 2014; 24:1575-93. [PMID: 25087834 PMCID: PMC4229697 DOI: 10.1089/thy.2014.0169] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND The thyroid hormone triiodothyronine (T3) is known to affect energy balance. Recent evidence points to an action of T3 in the hypothalamus, a key area of the brain involved in energy homeostasis, but the components and mechanisms are far from understood. The aim of this study was to identify components in the hypothalamus that may be involved in the action of T3 on energy balance regulatory mechanisms. METHODS Sprague Dawley rats were made hypothyroid by giving 0.025% methimazole (MMI) in their drinking water for 22 days. On day 21, half the MMI-treated rats received a saline injection, whereas the others were injected with T3. Food intake and body weight measurements were taken daily. Body composition was determined by magnetic resonance imaging, gene expression was analyzed by in situ hybridization, and T3-induced gene expression was determined by microarray analysis of MMI-treated compared to MMI-T3-injected hypothalamic RNA. RESULTS Post mortem serum thyroid hormone levels showed that MMI treatment decreased circulating thyroid hormones and increased thyrotropin (TSH). MMI treatment decreased food intake and body weight. Body composition analysis revealed reduced lean and fat mass in thyroidectomized rats from day 14 of the experiment. MMI treatment caused a decrease in circulating triglyceride concentrations, an increase in nonesterified fatty acids, and decreased insulin levels. A glucose tolerance test showed impaired glucose clearance in the thyroidectomized animals. In the brain, in situ hybridization revealed marked changes in gene expression, including genes such as Mct8, a thyroid hormone transporter, and Agrp, a key component in energy balance regulation. Microarray analysis revealed 110 genes to be up- or downregulated with T3 treatment (± 1.3-fold change, p<0.05). Three genes chosen from the differentially expressed genes were verified by in situ hybridization to be activated by T3 in cells located at or close to the hypothalamic ventricular ependymal layer and differentially expressed in animal models of long- and short-term body weight regulation. CONCLUSION This study identified genes regulated by T3 in the hypothalamus, a key area of the brain involved in homeostasis and neuroendocrine functions. These include genes hitherto not known to be regulated by thyroid status.
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Affiliation(s)
- Annika Herwig
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
- Zoological Institute, University of Hamburg, Hamburg, Germany
| | - Gill Campbell
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Claus-Dieter Mayer
- Biomathematics and Statistics Scotland, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Anita Boelen
- Department of Endocrinology, Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Richard A. Anderson
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Alexander W. Ross
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Julian G. Mercer
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Perry Barrett
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
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Abstract
Most species living outside the tropical zone undergo physiological adaptations to
seasonal environmental changes and changing day length (photoperiod); this phenomenon is
called photoperiodism. It is well known that the circadian clock is involved in the
regulation of photoperiodism such as seasonal reproduction, but the mechanism underlying
circadian clock regulation of photoperiodism remains unclear. Recent molecular analysis
have revealed that, in mammals and birds, the pars tuberalis (PT) of the pituitary gland
acts as the relay point from light receptors, which receive information about the
photoperiod, to the endocrine responses. Long-day (LD)-induced thyroid-stimulating hormone
(TSH) in the PT acts as a master regulator of seasonal reproduction in the ependymal cells
(ECs) within the mediobasal hypothalamus (MBH) and activates thyroid hormone (TH) by
inducing the expression of type 2 deiodinase in both LD and short-day (SD) breeding
animals. Furthermore, the circadian clock has been found to be localized in the PT and ECs
as well as in the circadian pacemaker(s). This review purposes to summarize the current
knowledge concerning the involvement of the neuroendocrine system and circadian clock in
seasonal reproduction.
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Affiliation(s)
- Keisuke Ikegami
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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Fekete C, Lechan RM. Central regulation of hypothalamic-pituitary-thyroid axis under physiological and pathophysiological conditions. Endocr Rev 2014; 35:159-94. [PMID: 24423980 PMCID: PMC3963261 DOI: 10.1210/er.2013-1087] [Citation(s) in RCA: 185] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Accepted: 11/05/2013] [Indexed: 12/18/2022]
Abstract
TRH is a tripeptide amide that functions as a neurotransmitter but also serves as a neurohormone that has a critical role in the central regulation of the hypothalamic-pituitary-thyroid axis. Hypophysiotropic TRH neurons involved in this neuroendocrine process are located in the hypothalamic paraventricular nucleus and secrete TRH into the pericapillary space of the external zone of the median eminence for conveyance to anterior pituitary thyrotrophs. Under basal conditions, the activity of hypophysiotropic TRH neurons is regulated by the negative feedback effects of thyroid hormone to ensure stable, circulating, thyroid hormone concentrations, a mechanism that involves complex interactions between hypophysiotropic TRH neurons and the vascular system, cerebrospinal fluid, and specialized glial cells called tanycytes. Hypophysiotropic TRH neurons also integrate other humoral and neuronal inputs that can alter the setpoint for negative feedback regulation by thyroid hormone. This mechanism facilitates adaptation of the organism to changing environmental conditions, including the shortage of food and a cold environment. The thyroid axis is also affected by other adverse conditions such as infection, but the central mechanisms mediating suppression of hypophysiotropic TRH may be pathophysiological. In this review, we discuss current knowledge about the mechanisms that contribute to the regulation of hypophysiotropic TRH neurons under physiological and pathophysiological conditions.
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Affiliation(s)
- Csaba Fekete
- Department of Endocrine Neurobiology (C.F.), Institute of Experimental Medicine, Hungarian Academy of Sciences, 1083 Budapest, Hungary; Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism (C.F., R.M.L.), Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111; and Department of Neuroscience (R.M.L.), Tufts University School of Medicine, Boston, Massachusetts 02111
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Petri I, Dumbell R, Scherbarth F, Steinlechner S, Barrett P. Effect of exercise on photoperiod-regulated hypothalamic gene expression and peripheral hormones in the seasonal Dwarf Hamster Phodopus sungorus. PLoS One 2014; 9:e90253. [PMID: 24603871 PMCID: PMC3946023 DOI: 10.1371/journal.pone.0090253] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 01/31/2014] [Indexed: 12/30/2022] Open
Abstract
The Siberian hamster (Phodopus sungorus) is a seasonal mammal responding to the annual cycle in photoperiod with anticipatory physiological adaptations. This includes a reduction in food intake and body weight during the autumn in anticipation of seasonally reduced food availability. In the laboratory, short-day induction of body weight loss can be reversed or prevented by voluntary exercise undertaken when a running wheel is introduced into the home cage. The mechanism by which exercise prevents or reverses body weight reduction is unknown, but one hypothesis is a reversal of short-day photoperiod induced gene expression changes in the hypothalamus that underpin body weight regulation. Alternatively, we postulate an exercise-related anabolic effect involving the growth hormone axis. To test these hypotheses we established photoperiod-running wheel experiments of 8 to 16 weeks duration assessing body weight, food intake, organ mass, lean and fat mass by magnetic resonance, circulating hormones FGF21 and insulin and hypothalamic gene expression. In response to running wheel activity, short-day housed hamsters increased body weight. Compared to short-day housed sedentary hamsters the body weight increase was accompanied by higher food intake, maintenance of tissue mass of key organs such as the liver, maintenance of lean and fat mass and hormonal profiles indicative of long day housed hamsters but there was no overall reversal of hypothalamic gene expression regulated by photoperiod. Therefore the mechanism by which activity induces body weight gain is likely to act largely independently of photoperiod regulated gene expression in the hypothalamus.
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Affiliation(s)
- Ines Petri
- Department of Zoology, University of Veterinary Medicine, Hannover, Germany
| | - Rebecca Dumbell
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Frank Scherbarth
- Department of Zoology, University of Veterinary Medicine, Hannover, Germany
| | | | - Perry Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
- * E-mail:
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Shinomiya A, Shimmura T, Nishiwaki-Ohkawa T, Yoshimura T. Regulation of seasonal reproduction by hypothalamic activation of thyroid hormone. Front Endocrinol (Lausanne) 2014; 5:12. [PMID: 24600435 PMCID: PMC3930870 DOI: 10.3389/fendo.2014.00012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Accepted: 01/31/2014] [Indexed: 12/15/2022] Open
Abstract
Organisms living outside the tropics measure the changes in the length of the day to adapt to seasonal changes in the environment. Animals that breed during spring and summer are called long-day breeders, while those that breed during fall are called short-day breeders. Although the influence of thyroid hormone in the regulation of seasonal reproduction has been known for several decades, its precise mechanism remained unknown. Recent studies revealed that the activation of thyroid hormone within the mediobasal hypothalamus plays a key role in this phenomenon. This localized activation of the thyroid hormone is controlled by thyrotropin (thyroid-stimulating hormone) secreted from the pars tuberalis of the pituitary gland. Although seasonal reproduction is a rate-limiting factor in animal production, genes involved in photoperiodic signal transduction pathway could emerge as potential targets to facilitate domestication.
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Affiliation(s)
- Ai Shinomiya
- Division of Seasonal Biology, National Institute for Basic Biology, Okazaki, Japan
| | - Tsuyoshi Shimmura
- Division of Seasonal Biology, National Institute for Basic Biology, Okazaki, Japan
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Taeko Nishiwaki-Ohkawa
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
- Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Takashi Yoshimura
- Division of Seasonal Biology, National Institute for Basic Biology, Okazaki, Japan
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, Japan
- Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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Dardente H, Hazlerigg DG, Ebling FJP. Thyroid hormone and seasonal rhythmicity. Front Endocrinol (Lausanne) 2014; 5:19. [PMID: 24616714 PMCID: PMC3935485 DOI: 10.3389/fendo.2014.00019] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 02/10/2014] [Indexed: 12/15/2022] Open
Abstract
Living organisms show seasonality in a wide array of functions such as reproduction, fattening, hibernation, and migration. At temperate latitudes, changes in photoperiod maintain the alignment of annual rhythms with predictable changes in the environment. The appropriate physiological response to changing photoperiod in mammals requires retinal detection of light and pineal secretion of melatonin, but extraretinal detection of light occurs in birds. A common mechanism across all vertebrates is that these photoperiod-regulated systems alter hypothalamic thyroid hormone (TH) conversion. Here, we review the evidence that a circadian clock within the pars tuberalis of the adenohypophysis links photoperiod decoding to local changes of TH signaling within the medio-basal hypothalamus (MBH) through a conserved thyrotropin/deiodinase axis. We also focus on recent findings which indicate that, beyond the photoperiodic control of its conversion, TH might also be involved in longer-term timing processes of seasonal programs. Finally, we examine the potential implication of kisspeptin and RFRP3, two RF-amide peptides expressed within the MBH, in seasonal rhythmicity.
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Affiliation(s)
- Hugues Dardente
- Physiologie de la Reproduction et des Comportements, INRA, UMR085, Nouzilly, France
- CNRS, UMR7247, Nouzilly, France
- Université François Rabelais de Tours, Tours, France
- Institut français du cheval et de l’équitation, Nouzilly, France
- *Correspondence: Hugues Dardente, INRA, UMR85 Physiologie de la Reproduction et des Comportements, CNRS, UMR7247, Université François Rabelais de Tours, IFCE, F-37380 Nouzilly, France e-mail:
| | - David G. Hazlerigg
- Department of Arctic and Marine Biology, University of Tromsø, Tromsø, Norway
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Yoshimura T. Thyroid hormone and seasonal regulation of reproduction. Front Neuroendocrinol 2013; 34:157-66. [PMID: 23660390 DOI: 10.1016/j.yfrne.2013.04.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 04/21/2013] [Accepted: 04/23/2013] [Indexed: 12/15/2022]
Abstract
Organisms living outside the tropics use changes in photoperiod to adapt to seasonal changes in the environment. Several models have contributed to an understanding of this mechanism at the molecular and endocrine levels. Subtropical birds are excellent models for the study of these mechanisms because of their rapid and dramatic response to changes in photoperiod. Studies of birds have demonstrated that light is perceived by a deep brain photoreceptor and long day-induced thyrotropin (TSH) from the pars tuberalis (PT) of the pituitary gland causes local thyroid hormone activation within the mediobasal hypothalamus (MBH). The locally generated bioactive thyroid hormone, T₃, regulates seasonal gonadotropin-releasing hormone (GnRH) secretion, and hence gonadotropin secretion. In mammals, the eyes are the only photoreceptor involved in photoperiodic time perception and nocturnal melatonin secretion provides an endocrine signal of photoperiod to the PT to regulate TSH. Here, I review the current understanding of the hypothalamic mechanisms controlling seasonal reproduction in mammals and birds.
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Affiliation(s)
- Takashi Yoshimura
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
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Overexpression of suppressor of cytokine signaling 3 in the arcuate nucleus of juvenile Phodopus sungorus alters seasonal body weight changes. J Comp Physiol B 2013; 183:1101-11. [PMID: 23860586 DOI: 10.1007/s00360-013-0772-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 06/09/2013] [Accepted: 06/14/2013] [Indexed: 12/17/2022]
Abstract
The profound seasonal cycle in body weight exhibited by the Djungarian hamster (Phodopus sungorus) is associated with the development of hypothalamic leptin resistance during long day photoperiod (LD, 16:8 h light dark cycle), when body weight is elevated relative to short day photoperiod (SD, 8:16 h light dark cycle). We previously have shown that this seasonal change in physiology is associated with higher levels of mRNA for the potent inhibitor of leptin signaling, suppressor of cytokine signaling-3 (SOCS3), in the arcuate nucleus (ARC) of LD hamsters relative to hamsters in SD. The alteration in SOCS3 gene expression preceded the body weight change suggesting that SOCS3 might be the molecular switch of seasonal body weight changes. To functionally characterize the role of SOCS3 in seasonal body weight regulation, we injected SOCS3 expressing recombinant adeno-associated virus type-2 (rAAV2-SOCS3) constructs into the ARC of leptin sensitive SD hamsters immediately after weaning. Hamsters that received rAAV2 expressing enhanced green fluorescent protein (rAAV2-EGFP) served as controls. ARC-directed SOCS3 overexpression led to a significant increase in body weight over a period of 12 weeks without fully restoring the LD phenotype. This increase was partially due to elevated brown and white adipose tissue mass. Gene expression of pro-opiomelanocortin was increased while thyroid hormone converting enzyme DIO3 mRNA levels were reduced in SD hamsters with SOCS3 overexpression. In conclusion, our data suggest that ARC-directed SOCS3 overexpression partially overcomes the profound seasonal body weight cycle exhibited by the hamster which is associated with altered pro-opiomelanocortin and DIO3 gene expression.
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Herwig A, de Vries EM, Bolborea M, Wilson D, Mercer JG, Ebling FJP, Morgan PJ, Barrett P. Hypothalamic ventricular ependymal thyroid hormone deiodinases are an important element of circannual timing in the Siberian hamster (Phodopus sungorus). PLoS One 2013; 8:e62003. [PMID: 23637944 PMCID: PMC3630139 DOI: 10.1371/journal.pone.0062003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 03/15/2013] [Indexed: 01/11/2023] Open
Abstract
Exposure to short days (SD) induces profound changes in the physiology and behaviour of Siberian hamsters, including gonadal regression and up to 30% loss in body weight. In a continuous SD environment after approximately 20 weeks, Siberian hamsters spontaneously revert to a long day (LD) phenotype, a phenomenon referred to as the photorefractory response. Previously we have identified a number of genes that are regulated by short photoperiod in the neuropil and ventricular ependymal (VE) cells of the hypothalamus, although their importance and contribution to photoperiod induced physiology is unclear. In this refractory model we hypothesised that the return to LD physiology involves reversal of SD expression levels of key hypothalamic genes to their LD values and thereby implicate genes required for LD physiology. Male Siberian hamsters were kept in either LD or SD for up to 39 weeks during which time SD hamster body weight decreased before increasing, after more than 20 weeks, back to LD values. Brain tissue was collected between 14 and 39 weeks for in situ hybridization to determine hypothalamic gene expression. In VE cells lining the third ventricle, expression of nestin, vimentin, Crbp1 and Gpr50 were down-regulated at 18 weeks in SD photoperiod, but expression was not restored to the LD level in photorefractory hamsters. Dio2, Mct8 and Tsh-r expression were altered by SD photoperiod and were fully restored, or even exceeded values found in LD hamsters in the refractory state. In hypothalamic nuclei, expression of Srif and Mc3r mRNAs was altered at 18 weeks in SD, but were similar to LD expression values in photorefractory hamsters. We conclude that in refractory hamsters not all VE cell functions are required to establish LD physiology. However, thyroid hormone signalling from ependymal cells and reversal of neuronal gene expression appear to be essential for the SD refractory response.
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Affiliation(s)
- Annika Herwig
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
| | - Emmely M. de Vries
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
| | - Matei Bolborea
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
- School of Biomedical Sciences, University of Nottingham Medical School, Queen Medical Centre, Nottingham, United Kingdom
| | - Dana Wilson
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
| | - Julian G. Mercer
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
| | - Francis J. P. Ebling
- School of Biomedical Sciences, University of Nottingham Medical School, Queen Medical Centre, Nottingham, United Kingdom
| | - Peter J. Morgan
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
| | - Perry Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen, United Kingdom
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Bolborea M, Dale N. Hypothalamic tanycytes: potential roles in the control of feeding and energy balance. Trends Neurosci 2013; 36:91-100. [PMID: 23332797 PMCID: PMC3605593 DOI: 10.1016/j.tins.2012.12.008] [Citation(s) in RCA: 210] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/11/2012] [Accepted: 12/18/2012] [Indexed: 02/08/2023]
Abstract
Tanycytes, glial-like cells that line the third ventricle, are emerging as components of the hypothalamic networks that control body weight and energy balance. They contact the cerebrospinal fluid (CSF) and send processes that come into close contact with neurons in the arcuate and ventromedial hypothalamic nuclei. Tanycytes are glucosensitive and are able to respond to transmitters associated with arousal and the drive to feed. At least some tanycytes are stem cells and, in the median eminence, may be stimulated by diet to generate new neurons. The quest is on to understand how tanycytes detect and respond to changes in energy balance and how they communicate with the rest of the nervous system to effect their functions.
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Affiliation(s)
- Matei Bolborea
- School of Life Sciences, University of Warwick, Coventry, UK
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43
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Costa-e-Sousa RH, Hollenberg AN. Minireview: The neural regulation of the hypothalamic-pituitary-thyroid axis. Endocrinology 2012; 153:4128-35. [PMID: 22759379 PMCID: PMC3423621 DOI: 10.1210/en.2012-1467] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 06/14/2012] [Indexed: 12/20/2022]
Abstract
Thyroid hormone (TH) signaling plays an important role in development and adult life. Many organisms may have evolved under selective pressure of exogenous TH, suggesting that thyroid hormone signaling is phylogenetically older than the systems that regulate their synthesis. Therefore, the negative feedback system by TH itself was probably the first mechanism of regulation of circulating TH levels. In humans and other vertebrates, it is well known that TH negatively regulates its own production through central actions that modulate the hypothalamic-pituitary-thyroid (HPT) axis. Indeed, primary hypothyroidism leads to the up-regulation of the genes encoding many key players in the HPT axis, such as TRH, type 2 deiodinase (dio2), pyroglutamyl peptidase II (PPII), TRH receptor 1 (TRHR1), and the TSH α- and β-subunits. However, in many physiological circumstances, the activity of the HPT axis is not always a function of circulating TH concentrations. Indeed, circadian changes in the HPT axis activity are not a consequence of oscillation in circulating TH levels. Similarly, during reduced food availability, several components of the HPT axis are down-regulated even in the presence of lower circulating TH levels, suggesting the presence of a regulatory pathway hierarchically higher than the feedback system. This minireview discusses the neural regulation of the HPT axis, focusing on both TH-dependent and -independent pathways and their potential integration.
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Affiliation(s)
- Ricardo H Costa-e-Sousa
- Beth Israel Deaconess Medical Center and Harvard Medical School, Division Endocrinology, Diabetes and Metabolism, 330 Brookline Avenue, CLS-0738, Boston, Massachusetts 02215, USA
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Herwig A, Petri I, Barrett P. Hypothalamic gene expression rapidly changes in response to photoperiod in juvenile Siberian hamsters (Phodopus sungorus). J Neuroendocrinol 2012; 24:991-8. [PMID: 22487258 DOI: 10.1111/j.1365-2826.2012.02324.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Siberian hamsters are seasonal mammals that survive a winter climate by making adaptations in physiology and behaviour. This includes gonadal atrophy, reduced food intake and body weight. The underlying central mechanisms responsible for the physiological adaptations are not fully established but involve reducing hypothalamic tri-iodthyronine (T3) levels. Juvenile Siberian hamsters born or raised in short days (SD) respond in a similar manner, although with an inhibition of gonadal development and growth instead of reversing an established long day (LD) phenotype. Using juvenile male hamsters, the present study aimed to investigate whether the central mechanisms are similar before the establishment of the mature LD phenotype. By in situ hybridisation, we examined the response of genes involved in thyroid hormone (Dio2 and Dio3, which determine hypothalamic T3 levels) and glucose/glutamate metabolism in the ependymal layer, histamine H3 receptor and VGF as representatives of the highly responsive dorsomedial posterior arcuate nucleus (dmpARC), and somatostatin, a hypothalamic neuropeptide involved in regulating the growth axis. Differential gene expression of type 2 and type 3 deiodinase in the ependymal layer, histamine H3 receptor in the dmpARC and somatostatin in the ARC was established by the eighth day in SD. These changes are followed by alterations in glucose metabolism related genes in the ependymal layer by day 16 and increased secretogranin expression in the dmpARC by day 32. In conclusion, our data demonstrate similar but rapid and highly responsive changes in gene expression in the brain of juvenile Siberian hamsters in response to a switch from LD to SD. The data also provide a temporal definition of gene expression changes relative to physiological adaptations of body weight and testicular development and highlight the likely importance of thyroid hormone availability as an early event in the adaptation of physiology to a winter climate in juvenile Siberian hamsters.
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Affiliation(s)
- A Herwig
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, UK
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Abstract
Seasonal mammals typically of temperate or boreal habitats use the predictable annual cycle of daylength to initiate a suite of physiological and behavioural changes in anticipation of adverse environmental winter conditions, unfavourable for survival and reproduction. Daylength is encoded as the duration of production of the pineal hormone melatonin, but how the melatonin signal is decoded has been elusive. From the studies carried out in birds and mammals together with the advent of technologies such as microarray analysis of gene expression, progress has been achieved to demystify how seasonal physiology is regulated in response to the duration of melatonin signalling. The critical tissue for the action of melatonin is the pars tuberalis (PT) where melatonin receptors are located. At the molecular level, regulation of cyclic adenosine monophosphate (cAMP) signalling in this tissue is likely to be a key event for melatonin action, either an acute inhibitory action or sensitization of this pathway by prolonged stimulation of melatonin receptors reflecting durational melatonin presence. Melatonin action at the PT has been shown to have both positive and negative effects on gene transcription, incorporating components of the circadian clock as part of the mechanism of decoding the melatonin signal and regulating thyrotrophin-stimulating hormone (TSH) expression, a key output hormone of the PT. Microarray analysis of gene expression of PT tissue exposed to long and short photoperiods has identified important new genes that may be regulated by melatonin and contributing to the seasonal regulation of TSH production by this tissue. In the brain, tanycytes lining the third ventricle of the hypothalamus and regulation of thyroid hormone synthesis by PT-derived TSH in these cells are now established as an important component of the pathway leading to seasonal changes in physiology. Beyond the tanycyte, identified changes in gene expression for neuropeptides, receptors and other signalling molecules pinpoint some of the areas of the brain, the hypothalamus in particular, that are likely to be involved in the regulation of seasonal physiology.
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Affiliation(s)
- Perry Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, UK.
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46
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Menassol JB, Collet A, Chesneau D, Malpaux B, Scaramuzzi RJ. The interaction between photoperiod and nutrition and its effects on seasonal rhythms of reproduction in the ewe. Biol Reprod 2012; 86:52. [PMID: 22053094 DOI: 10.1095/biolreprod.111.092817] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In sheep, the seasonal patterns of reproductive activity are driven primarily by the annual photoperiodic cycle, but can also respond to other environmental factors, such as nutrition, yet little is known about the mechanisms underlying this interaction. This study was designed to define the interaction between photoperiodic and nutritional cues on seasonal patterns of ovarian activity, and to determine if there is a central interaction between these cues. Groups of Ile-de-France ewes were maintained in two nutritional states (restricted and well fed) under a simulated annual photoperiod of 8-16 h of light per day over two breeding seasons. At the end of the first breeding season, half of the animals of each group were ovariectomized (OVX) and fitted subcutaneously with estradiol implants. Low nutritional status shortened the season of ovarian activity, determined from the pattern of progesterone concentrations, by modifying the timing of seasonal transitions between periods of ovarian activity and anestrus. The same results were observed for the seasonal rhythm of neuroendocrine activity, assessed in the OVX ewes, from the pattern of luteinizing hormone concentrations. These results were then confirmed for neuroendocrine activity induced by a photoperiodic treatment. We conclude that nutrition centrally modulates the interpretation of photoperiod to affect seasonal reproductive transitions. The mechanisms of this interaction are discussed in the paper.
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47
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Ikegami K, Yoshimura T. Circadian clocks and the measurement of daylength in seasonal reproduction. Mol Cell Endocrinol 2012; 349:76-81. [PMID: 21767603 DOI: 10.1016/j.mce.2011.06.040] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 05/18/2011] [Accepted: 06/28/2011] [Indexed: 12/15/2022]
Abstract
Temperate zone organisms measure changes in daylength to adapt to seasonal changes in their environment. Recent studies have revealed that the long day (LD)-induced thyrotropin (TSH) in the pars tuberalis (PT) of the pituitary gland act as a master factor regulating seasonal reproduction on the the ependymal cells (ECs) within the mediobasal hypothalamus (MBH) to induce expression of type 2 deiodinase (Dio2), a thyroid hormone (TH)-activating enzyme in both LD and short day (SD) breeders. Locally activated TH in the MBH is believed to trigger GnRH secretion from the hypothalamus in LD breeders, while it terminates reproductive activity in SD breeders. Circadian clock is involved in seasonal time measurement and clock genes are expressed in the PT and ECs. Although circadian and melatonin-dependent control of TSH appears to link the circadian clock and the photoperiodic response in mammals, how this circadian clock measure daylength remains to be clarified.
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Affiliation(s)
- Keisuke Ikegami
- Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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48
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Wambiji N, Park YJ, Kim SJ, Hur SP, Takeuchi Y, Takemura A. Expression of type II iodothyronine deiodinase gene in the brain of a tropical spinefoot, Siganus guttatus. Comp Biochem Physiol A Mol Integr Physiol 2011; 160:447-52. [DOI: 10.1016/j.cbpa.2011.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Revised: 03/28/2011] [Accepted: 03/28/2011] [Indexed: 11/15/2022]
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49
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Florant GL, Healy JE. The regulation of food intake in mammalian hibernators: a review. J Comp Physiol B 2011; 182:451-67. [PMID: 22080368 DOI: 10.1007/s00360-011-0630-y] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Revised: 10/20/2011] [Accepted: 10/29/2011] [Indexed: 12/20/2022]
Abstract
One of the most profound hallmarks of mammalian hibernation is the dramatic reduction in food intake during the winter months. Several species of hibernator completely cease food intake (aphagia) for nearly 7 months regardless of ambient temperature and in many cases, whether or not food is available to them. Food intake regulation has been studied in mammals that hibernate for over 50 years and still little is known about the physiological mechanisms that control this important behavior in hibernators. It is well known from lesion experiments in non-hibernators that the hypothalamus is the main brain region controlling food intake and therefore body mass. In hibernators, the regulation of food intake and body mass is presumably governed by a circannual rhythm since there is a clear seasonal rhythm to food intake: animals increase food intake in the summer and early autumn, food intake declines in autumn and actually ceases in winter in many species, and resumes again in spring as food becomes available in the environment. Changes in circulating hormones (e.g., leptin, insulin, and ghrelin), nutrients (glucose, and free fatty acids), and cellular enzymes such as AMP-activated protein kinase (AMPK) have been shown to determine the activity of neurons involved in the food intake pathway. Thus, it appears likely that the food intake pathway is controlled by a variety of inputs, but is also acted upon by upstream regulators that are presumably rhythmic in nature. Current research examining the molecular mechanisms and integration of environmental signals (e.g., temperature and light) with these molecular mechanisms will hopefully shed light on how animals can turn off food intake and survive without eating for months on end.
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Affiliation(s)
- Gregory L Florant
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
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50
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Nilaweera K, Herwig A, Bolborea M, Campbell G, Mayer CD, Morgan PJ, Ebling FJP, Barrett P. Photoperiodic regulation of glycogen metabolism, glycolysis, and glutamine synthesis in tanycytes of the Siberian hamster suggests novel roles of tanycytes in hypothalamic function. Glia 2011; 59:1695-705. [DOI: 10.1002/glia.21216] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 06/16/2011] [Indexed: 12/27/2022]
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