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Haugg E, Borner J, Stalder G, Kübber‐Heiss A, Giroud S, Herwig A. Comparative transcriptomics of the garden dormouse hypothalamus during hibernation. FEBS Open Bio 2024; 14:241-257. [PMID: 37925593 PMCID: PMC10839406 DOI: 10.1002/2211-5463.13731] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/25/2023] [Accepted: 11/02/2023] [Indexed: 11/06/2023] Open
Abstract
Torpor or heterothermy is an energy-saving mechanism used by endotherms to overcome harsh environmental conditions. During winter, the garden dormouse (Eliomys quercinus) hibernates with multiday torpor bouts and body temperatures of a few degrees Celsius, interrupted by brief euthermic phases. This study investigates gene expression within the hypothalamus, the key brain area controlling energy balance, adding information on differential gene expression potentially relevant to orchestrate torpor. A de novo assembled transcriptome of the hypothalamus was generated from garden dormice hibernating under constant darkness without food and water at 5 °C. Samples were collected during early torpor, late torpor, and interbout arousal. During early torpor, 765 genes were differentially expressed as compared with interbout arousal. Twenty-seven pathways were over-represented, including pathways related to hemostasis, extracellular matrix organization, and signaling of small molecules. Only 82 genes were found to be differentially expressed between early and late torpor, and no pathways were over-represented. During late torpor, 924 genes were differentially expressed relative to interbout arousal. Despite the high number of differentially expressed genes, only 10 pathways were over-represented. Of these, eight were also observed to be over-represented when comparing early torpor and interbout arousal. Our results are largely consistent with previous findings in other heterotherms. The addition of a transcriptome of a novel species may help to identify species-specific and overarching torpor mechanisms through future species comparisons.
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Affiliation(s)
- Elena Haugg
- Institute of NeurobiologyUlm UniversityGermany
| | - Janus Borner
- Sackler Institute for Comparative GenomicsAmerican Museum of Natural HistoryNew YorkNYUSA
| | - Gabrielle Stalder
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
| | - Anna Kübber‐Heiss
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
| | - Sylvain Giroud
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife EcologyUniversity of Veterinary MedicineViennaAustria
- Energetics Lab, Department of BiologyNorthern Michigan UniversityMarquetteMIUSA
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2
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Kawach R, Diedrich V, Gruber A, Leopold K, Herwig A, Vujić Spasić M. Seasonal and fasting induced changes in iron metabolism in Djungarian hamsters. PLoS One 2023; 18:e0293971. [PMID: 37930992 PMCID: PMC10627461 DOI: 10.1371/journal.pone.0293971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 10/20/2023] [Indexed: 11/08/2023] Open
Abstract
Djungarian hamsters are small rodents that show pronounced physiological acclimations in response to changes in photoperiod, and unfavorable environmental conditions such as reduced food availability and low external temperature. These include substantial adjustments, such as severe body weight loss and the use of daily torpor. Torpor is a state of decreased physiological activity in eutherms, usually marked by low metabolic rate and a reduced body temperature. In this study, we investigated the effects of photoperiodic acclimation and food deprivation on systemic iron metabolism in Djungarian hamsters. Our study illustrates the association between liver iron levels and the incidence of torpor expression during the course of the experiment. Moreover, we show that both, acclimation to short photoperiods and long-term food restriction, associated with iron sequestration in the liver. This effect was accompanied with hypoferremia and mild reduction in the expression of principal iron-hormone, hepcidin. In addition to iron, the levels of manganese, selenium, and zinc were increased in the liver of hamsters under food restriction. These findings may be important factors for regulating physiological processes in hamsters, since iron and other trace elements are essential for many metabolic and physiological processes.
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Affiliation(s)
- Rawan Kawach
- Institute of Comparative Molecular Endocrinology, Ulm University, Ulm, Germany
| | | | - Andreas Gruber
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany
| | - Kerstin Leopold
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, Ulm, Germany
| | - Annika Herwig
- Institute of Neurobiology, Ulm University, Ulm, Germany
| | - Maja Vujić Spasić
- Institute of Comparative Molecular Endocrinology, Ulm University, Ulm, Germany
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3
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Diedrich V, Haugg E, Van Hee J, Herwig A. Role of glucose in daily torpor of Djungarian hamsters ( Phodopus sungorus): challenge of continuous in vivo blood glucose measurements. Am J Physiol Regul Integr Comp Physiol 2023; 325:R359-R379. [PMID: 37519255 DOI: 10.1152/ajpregu.00040.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/03/2023] [Accepted: 07/23/2023] [Indexed: 08/01/2023]
Abstract
Djungarian hamsters use daily torpor to save energy during winter. This metabolic downstate is part of their acclimatization strategy in response to short photoperiod and expressed spontaneously without energy challenges. During acute energy shortage, torpor incidence, depth, and duration can be modulated. Torpor induction might rely on glucose availability as acute metabolic energy source. To investigate this, the present study provides the first continuous in vivo blood glucose measurements of spontaneous daily torpor in short photoperiod-acclimated and fasting-induced torpor in long photoperiod-acclimated Djungarian hamsters. Glucose levels were almost identical in both photoperiods and showed a decrease during resting phase. Further decreases appeared during spontaneous daily torpor entrance, parallel with metabolic rate but before body temperature, while respiratory exchange rates were rising. During arousal, blood glucose tended to increase, and pretorpor values were reached at torpor termination. Although food-restricted hamsters underwent a considerable energetic challenge, blood glucose levels remained stable during the resting phase regardless of torpor expression. The activity phase preceding a torpor bout did not reveal changes in blood glucose that might be used as torpor predictor. Djungarian hamsters show a robust, circadian rhythm in blood glucose irrespective of season and maintain appropriate levels throughout complex acclimation processes including metabolic downstates. Although these measurements could not reveal blood glucose as proximate torpor induction factor, they provide new information about glucose availability during torpor. Technical innovations like in vivo microdialysis and in vitro transcriptome or proteome analyses may help to uncover the connection between torpor expression and glucose metabolism.
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Affiliation(s)
| | - Elena Haugg
- Institute of Neurobiology, Ulm University, Ulm, Germany
| | - Justin Van Hee
- Data Sciences International, St. Paul, Minnesota, United States
| | - Annika Herwig
- Institute of Neurobiology, Ulm University, Ulm, Germany
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4
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Noakes MJ, Przybylska-Piech AS, Wojciechowski MS, Jefimow M. Is torpor a water conservation strategy? Heterothermic responses to acute water and food deprivation are repeatable among individuals of Phodopus sungorus. J Therm Biol 2022; 109:103321. [DOI: 10.1016/j.jtherbio.2022.103321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 07/01/2022] [Accepted: 08/30/2022] [Indexed: 10/14/2022]
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Maloney CM, Careau V. Individual variation in heat substitution: is activity in the cold energetically cheaper for some individuals than others? J Exp Biol 2022; 225:276466. [PMID: 36036801 DOI: 10.1242/jeb.244186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 08/25/2022] [Indexed: 11/20/2022]
Abstract
In many endotherms, a potentially important yet often overlooked mechanism to save energy is the use of the heat generated by active skeletal muscles to replace heat that would have been generated by thermogenesis (i.e., "activity-thermoregulatory heat substitution"). While substitution has been documented numerous times, the extent of individual variation in substitution has never been quantified. Here, we used a home-cage respirometry system to repeatedly measure substitution through the concomitant monitoring of metabolic rate (MR) and locomotor activity in 46 female white-footed mice (Peromyscus leucopus). A total of 117 measures of substitution were taken by quantifying the difference in the slope of the relationship between MR and locomotor activity speed at two different ambient temperatures. Consistency repeatability (±se) of substitution was 0.313±0.131 - hence, about a third of the variation in substitution occurs at the among-individual level. Body length and heart mass were positively correlated with substitution whereas surface area was negatively correlated with substitution. These two sub-organismal traits accounted for the majority of the among-individual variation (i.e., individual differences in substitution were not significant after accounting for these traits). Overall, our results imply that the energetic cost of activity below the thermoneutral zone is consistently cheaper from some individuals than others, and that the energy saved from substitution might be available to invest in fitness-enhancing activities.
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Affiliation(s)
- Caroline M Maloney
- Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Vincent Careau
- Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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Przybylska-Piech AS, Jefimow M. Siberian hamsters nonresponding to short photoperiod use fasting-induced torpor. J Exp Biol 2022; 225:275527. [PMID: 35615921 DOI: 10.1242/jeb.244222] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/17/2022] [Indexed: 11/20/2022]
Abstract
Nonresponding Siberian hamsters Phodopus sungorus do not develop the winter phenotype with white fur, low body mass (mb) and spontaneous torpor use in response to short photoperiod. However, their thermoregulatory response to fasting remains unknown. We measured body temperature and mb of 12 nonresponders acclimated to short photoperiod and then to cold, and fasted four times for 24h. Four individuals used torpor and in total we recorded 19 torpor bouts, which were shallow, short, and occurred at night. Moreover fasting increased the heterothermy index in all hamsters. Low mb was not a prerequisite for torpor use and mb loss correlated with neither heterothermy index nor torpor use. This is the first evidence that individuals which do not develop the winter phenotype, can use torpor or increase body temperature variability to face unpredictable, adverse environmental conditions. Despite the lack of seasonal changes, thermoregulatory adjustments may increase winter survival probability of nonresponders.
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Affiliation(s)
- Anna S Przybylska-Piech
- Department of Vertebrate Zoology and Ecology; Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, ul. Lwowska 1, 87-100 Toruń, Poland
| | - Małgorzata Jefimow
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, ul. Lwowska 1, 87-100 Toruń, Poland
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HORII Y, OKADERA K, MIYAWAKI S, SHIINA T, SHIMIZU Y. <i>Suncus murinus</i> as a novel model animal that is suitable for elucidating the mechanism of daily torpor. Biomed Res 2022; 43:53-57. [DOI: 10.2220/biomedres.43.53] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yuuki HORII
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Kanako OKADERA
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Shingo MIYAWAKI
- Laboratory of Veterinary Surgery, Faculty of Applied Biological Sciences, Gifu University
| | - Takahiko SHIINA
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
| | - Yasutake SHIMIZU
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University
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8
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Haugg E, Borner J, Diedrich V, Herwig A. Comparative transcriptomics of the Djungarian hamster hypothalamus during short photoperiod acclimation and spontaneous torpor. FEBS Open Bio 2022; 12:443-459. [PMID: 34894101 PMCID: PMC8804604 DOI: 10.1002/2211-5463.13350] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/30/2021] [Accepted: 12/10/2021] [Indexed: 12/03/2022] Open
Abstract
The energy-saving strategy of Djungarian hamsters (Phodopus sungorus, Cricetidae) to overcome harsh environmental conditions comprises of behavioral, morphological, and physiological adjustments, including spontaneous daily torpor, a metabolic downstate. These acclimatizations are triggered by short photoperiod and orchestrated by the hypothalamus. Key mechanisms of long-term photoperiodic acclimatizations have partly been described, but specific mechanisms that acutely control torpor remain incomplete. Here, we performed comparative transcriptome analysis on hypothalamus of normometabolic hamsters in their summer- and winter-like state to enable us to identify changes in gene expression during photoperiodic acclimations. Comparing nontorpid and torpid hamsters may also be able to pin down mechanisms relevant for torpor control. A de novo assembled transcriptome of the hypothalamus was generated from hamsters acclimated to long photoperiod or to short photoperiod. The hamsters were sampled either during long photoperiod normothermia, short photoperiod normothermia, or short photoperiod-induced spontaneous torpor with a body temperature of 24.6 ± 1.0 °C, or. The mRNA-seq analysis revealed that 32 and 759 genes were differentially expressed during photoperiod or torpor, respectively. Biological processes were not enriched during photoperiodic acclimatization but were during torpor, where transcriptional and metabolic processes were reinforced. Most extremely regulated genes (those genes with |log2(FC)| > 2.0 and padj < 0.05 of a pairwise group comparison) underpinned the role of known key players in photoperiodic comparison, but these genes exhibit adaptive and protective adjustments during torpor. Targeted analyses of genes from potentially involved hypothalamic systems identified gene regulation of previously described torpor-relevant systems and a potential involvement of glucose transport.
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Affiliation(s)
- Elena Haugg
- Institute of NeurobiologyUlm UniversityGermany
| | - Janus Borner
- Institute of Evolutionary Ecology and Conservation GenomicsUlm UniversityGermany
- Sackler Institute for Comparative GenomicsAmerican Museum of Natural HistoryNew YorkNYUSA
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Haugg E, Herwig A, Diedrich V. Body Temperature and Activity Adaptation of Short Photoperiod-Exposed Djungarian Hamsters ( Phodopus sungorus): Timing, Traits, and Torpor. Front Physiol 2021; 12:626779. [PMID: 34305626 PMCID: PMC8294097 DOI: 10.3389/fphys.2021.626779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 05/24/2021] [Indexed: 11/13/2022] Open
Abstract
To survive the Siberian winter, Djungarian hamsters (Phodopus sungorus) adjust their behavior, morphology, and physiology to maintain energy balance. The reduction of body mass and the improvement of fur insulation are followed by the expression of spontaneous daily torpor, a state of reduced metabolism during the resting phase to save additional energy. Since these complex changes require time, the upcoming winter is anticipated via decreasing photoperiod. Yet, the extent of adaptation and torpor use is highly individual. In this study, adaptation was triggered by an artificially changed light regime under laboratory conditions with 20°C ambient temperature and food and water ad libitum. Two approaches analyzed data on weekly measured body mass and fur index as well as continuously recorded core body temperature and activity during: (1) the torpor period of 60 hamsters and (2) the entire adaptation period of 11 hamsters, aiming to identify parameters allowing (1) a better prediction of torpor expression in individuals during the torpor period as well as (2) an early estimation of the adaptation extent and torpor proneness. In approach 1, 46 torpor-expressing hamsters had a median torpor incidence of 0.3, covering the spectrum from no torpor to torpor every day within one representative week. Torpor use reduced the body temperature during both photo- and scotophase. Torpor was never expressed by 14 hamsters. They could be identified by a high, constant body temperature during the torpor period and a low body mass loss during adaptation to a short photoperiod. Already in the first week of short photoperiod, approach 2 revealed that the hamsters extended their activity over the prolonged scotophase, yet with reduced scotophase activity and body temperature. Over the entire adaptation period, scotophase activity and body temperature of the scoto- and photophases were further reduced, later accompanied by a body mass decline and winter fur development. Torpor was expressed by those hamsters with the most pronounced adaptations. These results provide insights into the preconditions and proximate stimuli of torpor expression. This knowledge will improve experimental planning and sampling for neuroendocrine and molecular research on torpor regulation and has the potential to facilitate acute torpor forecasting to eventually unravel torpor regulation processes.
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Affiliation(s)
- Elena Haugg
- Institute of Neurobiology, Ulm University, Ulm, Germany
| | - Annika Herwig
- Institute of Neurobiology, Ulm University, Ulm, Germany
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10
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Piscitiello E, Herwig A, Haugg E, Schröder B, Breves G, Steinlechner S, Diedrich V. Acclimation of intestinal morphology and function in Djungarian hamsters ( Phodopus sungorus) related to seasonal and acute energy balance. J Exp Biol 2021; 224:jeb232876. [PMID: 33376143 DOI: 10.1242/jeb.232876] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 12/17/2020] [Indexed: 02/01/2023]
Abstract
Small mammals exhibit seasonal changes in intestinal morphology and function via increased intestine size and resorptive surface and/or nutrient transport capacity to increase energy yield from food during winter. This study investigated whether seasonal or acute acclimation to anticipated or actual energetic challenges in Djungarian hamsters also resulted in higher nutrient resorption capacities owing to changes in small intestine histology and physiology. The hamsters show numerous seasonal energy-saving adjustments in response to short photoperiod. As spontaneous daily torpor represents one of these adjustments related to food quality and quantity, it was hypothesized that the hamsters' variable torpor expression patterns are influenced by their individual nutrient uptake capacity. Hamsters under short photoperiod showed longer small intestines and higher mucosal electrogenic transport capacities for glucose relative to body mass. Similar observations were made in hamsters under long photoperiod and food restriction. However, this acute energetic challenge caused a stronger increase of glucose transport capacity. Apart from that, neither fasting-induced torpor in food-restricted hamsters nor spontaneous daily torpor in short photoperiod-exposed hamsters clearly correlated with mucosal glucose transport capacity. Both seasonally anticipated and acute energetic challenges caused adjustments in the hamsters' small intestine. Short photoperiod appeared to induce an integration of these and other acclimation processes in relation to body mass to achieve a long-term adjustment of energy balance. Food restriction seemed to result in a more flexible, short-term strategy of maximizing energy uptake possibly via mucosal glucose transport and reducing energy consumption via torpor expression as an emergency response.
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Affiliation(s)
- Emiliana Piscitiello
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Piazza di Porta San Donato 2, 40126 Bologna, Italy
| | - Annika Herwig
- Institute of Neurobiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Elena Haugg
- Institute of Neurobiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Bernd Schröder
- Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany
| | - Gerhard Breves
- Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany
| | - Stephan Steinlechner
- Department of Zoology, University of Veterinary Medicine Hannover, Bünteweg 17, 30559 Hannover, Germany
| | - Victoria Diedrich
- Institute of Neurobiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Geiser F. Seasonal Expression of Avian and Mammalian Daily Torpor and Hibernation: Not a Simple Summer-Winter Affair †. Front Physiol 2020; 11:436. [PMID: 32508673 PMCID: PMC7251182 DOI: 10.3389/fphys.2020.00436] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 04/08/2020] [Indexed: 12/17/2022] Open
Abstract
Daily torpor and hibernation (multiday torpor) are the most efficient means for energy conservation in endothermic birds and mammals and are used by many small species to deal with a number of challenges. These include seasonal adverse environmental conditions and low food/water availability, periods of high energetic demands, but also reduced foraging options because of high predation pressure. Because such challenges differ among regions, habitats and food consumed by animals, the seasonal expression of torpor also varies, but the seasonality of torpor is often not as clear-cut as is commonly assumed and differs between hibernators and daily heterotherms expressing daily torpor exclusively. Hibernation is found in mammals from all three subclasses from the arctic to the tropics, but is known for only one bird. Several hibernators can hibernate for an entire year or express torpor throughout the year (8% of species) and more hibernate from late summer to spring (14%). The most typical hibernation season is the cold season from fall to spring (48%), whereas hibernation is rarely restricted to winter (6%). In hibernators, torpor expression changes significantly with season, with strong seasonality mainly found in the sciurid and cricetid rodents, but seasonality is less pronounced in the marsupials, bats and dormice. Daily torpor is diverse in both mammals and birds, typically is not as seasonal as hibernation and torpor expression does not change significantly with season. Torpor in spring/summer has several selective advantages including: energy and water conservation, facilitation of reproduction or growth during development with limited resources, or minimisation of foraging and thus exposure to predators. When torpor is expressed in spring/summer it is usually not as deep and long as in winter, because of higher ambient temperatures, but also due to seasonal functional plasticity. Unlike many other species, subtropical nectarivorous blossom-bats and desert spiny mice use more frequent and pronounced torpor in summer than in winter, which is related to seasonal availability of nectar or water. Thus, seasonal use of torpor is complex and differs among species and habitats.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology CO2, University of New England, Armidale, NSW, Australia
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12
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Eto T, Sakamoto SH, Okubo Y, Tsuzuki Y, Koshimoto C, Morita T. Individual variation of daily torpor and body mass change during winter in the large Japanese field mouse (Apodemus speciosus). J Comp Physiol B 2018; 188:1005-1014. [PMID: 30194463 DOI: 10.1007/s00360-018-1179-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 08/12/2018] [Accepted: 09/03/2018] [Indexed: 11/24/2022]
Abstract
Daily torpor is a strategy used by some overwintering small endotherms to aid in energy conservation. However, the pattern of torpor varies among individuals within species and populations, even under the same environmental conditions, with significant implications for survival rate and reproductive success. Body mass is one factor that may influence this variation, especially in some small mammals that accumulate fat stores prior to overwintering. However, to our knowledge there has been no previous study examining the detailed relationships between torpor expression and body mass change in small mammals that hoard food as an energy resource during winter. The large Japanese field mouse, Apodemus speciosus, whose winter survival strategy depends on food caches instead of fat stores, displays daily torpor under artificial winter conditions (short-day photoperiod and cold). The present study clarifies the characteristics and patterns of daily torpor and body mass change in this species in the laboratory. Although expression of daily torpor was facilitated progressively as in other species, the observed patterns of torpor expression and body mass change showed considerable individual variation. Moreover, there was no obvious correlation between body mass and daily torpor expression. Therefore, it is suggested that in A. speciosus body mass may not contribute to individual variation of daily torpor during winter. Daily torpor during winter may be adjusted by not only mechanisms common to other small mammals, but also species-specific factors relating to the external or internal reserves of energy in small mammals.
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Affiliation(s)
- Takeshi Eto
- Interdisciplinary Graduate School of Agriculture and Engineering, Kibana Campus, University of Miyazaki, Miyazaki, 889-2192, Japan.,Center for Toki and Ecological Restoration, Niigata University, Niigata, 952-0103, Japan
| | - Shinsuke H Sakamoto
- Faculty of Agriculture, Kibana Campus, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Yoshinobu Okubo
- Interdisciplinary Graduate School of Agriculture and Engineering, Kibana Campus, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Yasuhiro Tsuzuki
- Faculty of Agriculture, Kibana Campus, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Chihiro Koshimoto
- Division of Bio-Resources, Frontier Science Research Center, Kiyotake Campus, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Tetsuo Morita
- Faculty of Agriculture, Kibana Campus, University of Miyazaki, Miyazaki, 889-2192, Japan. .,Division of Bio-Resources, Frontier Science Research Center, Kiyotake Campus, University of Miyazaki, Miyazaki, 889-1692, Japan.
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Mahlert B, Gerritsmann H, Stalder G, Ruf T, Zahariev A, Blanc S, Giroud S. Implications of being born late in the active season for growth, fattening, torpor use, winter survival and fecundity. eLife 2018; 7:31225. [PMID: 29458712 PMCID: PMC5819945 DOI: 10.7554/elife.31225] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Accepted: 01/10/2018] [Indexed: 12/05/2022] Open
Abstract
For hibernators, being born late in the active season may have important effects on growth and fattening, hence on winter survival and reproduction. This study investigated differences in growth, fattening, energetic responses, winter survival and fecundity between early-born (‘EB’) and late-born (‘LB’) juvenile garden dormice (Eliomys quercinus). LB juveniles grew and gained mass twice as fast as EB individuals. Torpor use was low during intensive growth, that are, first weeks of body mass gain, but increased during pre-hibernation fattening. LB juveniles showed higher torpor use, reached similar body sizes but lower fat content than EB individuals before hibernation. Finally, LB individuals showed similar patterns of hibernation, but higher proportion of breeders during the following year than EB dormice. These results suggest that torpor is incompatible with growth but promotes fattening and consolidates pre-hibernation fat depots. In garden dormice, being born late in the reproductive season is associated with a fast life history. Garden dormice are small rodents which are common in European woodlands. They were historically widespread from Portugal in the west to the Urals (Russia) in the east. However they are now largely confined to western Europe with north-eastern and eastern populations having become scattered and fragmented. During the course of a year in northern and central Europe, they make the most of the warm season to fatten up and to produce up to two litters of youngsters. When winter comes, dormice enter hibernation, sometimes for more than six months. During this time, they must rely on their fat reserves to survive. Every year, the young from the second litter have less time to prepare for the winter compared to their siblings born earlier in the season. So, how do they still manage to get ready on time for hibernation? Here, Mahlert et al. studied captive pups from first and second litters for their first year, following them as they grew up, entered and then emerged from their first hibernation. The late-born individuals developed nearly twice as fast as the ones born early in the season. In fact, both reached a similar body size, but the second-litter dormice had less fat reserves. Just before their first winter, both early- and late-born animals increasingly started to enter torpor – short and daily resting-like periods when the body slows down. Torpor rarely happens when animals are growing (because growth requires a warm body), but it is useful to help storing and consolidating fat before the cold months. Late-born dormice experienced more torpor on average than their first-litter peers. Both groups survived their first hibernation; but when they emerged, late-born individuals were more likely to reproduce that year. In other words, the dormice which grew quickly might also have sexually matured earlier. This could suggest that animals born later in the season have a faster life history: they grow rapidly, reproduce quickly but may die younger than their early-born peers. Mahlert et al. highlighted how early-life events can shape the course of animals’ existences and influence how their bodies operate. It remains to be examined how these circumstances may affect the individuals in the longer term, and perhaps even their descendants.
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Affiliation(s)
- Britta Mahlert
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Hanno Gerritsmann
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Gabrielle Stalder
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Thomas Ruf
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Alexandre Zahariev
- Université de Strasbourg, IPHC, Strasbourg, France.,CNRS, UMR7178, Strasbourg, France
| | - Stéphane Blanc
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria.,Université de Strasbourg, IPHC, Strasbourg, France.,CNRS, UMR7178, Strasbourg, France
| | - Sylvain Giroud
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
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14
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Chi QS, Li XJ, Wang DH. 2-Deoxy-D-glucose, not mercaptoacetate, induces a reversible reduction of body temperature in male desert hamsters (Phodopus roborovskii). J Therm Biol 2017; 71:189-194. [PMID: 29301689 DOI: 10.1016/j.jtherbio.2017.11.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 11/18/2017] [Accepted: 11/20/2017] [Indexed: 11/17/2022]
Abstract
The initiation of torpor is supposed to be related to the availability of metabolic fuels. Studies on metabolic fuel inhibition of glucose by using 2-deoxy-D-glucose (2DG) or fatty acid by mercaptoacetate (MA) in heterothermic mammals produced mixed outcomes. To examine the roles of availability of glucose and fatty acid in the initiation of torpor in desert hamsters (Phodopus roborovskii), we intraperitoneally administrated 2DG and MA to summer-acclimated male hamsters while body temperature (Tb), metabolic rate (MR) and respiratory quotient (RQ) were simultaneously recorded to monitor their thermoregulatory response. 2DG induced a reversible reduction of Tb in desert hamsters both at ambient temperature (Ta) of 23°C and 5°C. At Ta of 23°C, Tb, MR and RQ decreased in a dose-dependent manner with a large Tb-Ta differential (> 6.5°C) and a lowest Tb of 28.0°C which were comparable to those in fasted hamsters. At Ta of 5°C, 2DG-treated hamsters also decreased Tb to the same level as at Ta 23°C, but MR was significantly higher than that at Ta of 23°C at each dose, suggesting doses of 2DG directly affected the hypothalamic Tb set-point. Different from fasted hamsters which maintain normothermic at Ta of 5°C, 2DG-treated hamsters showed a substantial reduction of Tb at Ta 5°C, indicating an overwhelming effect on the thermoregulatory system regardless of Ta. Furthermore, the rapid decrease of Tb and outstretched body posture in 2DG-treated hamsters suggest that the effects of 2DG were not simply mimicking the torpor pathways but that other mechanisms are involved. Interestingly, MA failed to induce a torpor-like state in male desert hamsters. Our results suggest that availability of glucose rather than fatty acid plays an important role for initiation of torpor in desert hamsters.
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Affiliation(s)
- Qing-Sheng Chi
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beichen Xilu, Chaoyang, Beijing 100101, China
| | - Xiu-Juan Li
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beichen Xilu, Chaoyang, Beijing 100101, China; Institute of Health Sciences, Anhui University, Hefei, Anhui 230601, China
| | - De-Hua Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beichen Xilu, Chaoyang, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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15
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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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16
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Chi QS, Wan XR, Geiser F, Wang DH. Fasting-induced daily torpor in desert hamsters (Phodopus roborovskii). Comp Biochem Physiol A Mol Integr Physiol 2016; 199:71-77. [PMID: 27215346 DOI: 10.1016/j.cbpa.2016.05.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 05/12/2016] [Accepted: 05/18/2016] [Indexed: 10/21/2022]
Abstract
Daily torpor is frequently expressed in small rodents when facing energetically unfavorable ambient conditions. Desert hamsters (Phodopus roborovskii, ~20g) appear to be an exception as they have been described as homeothermic. However, we hypothesized that they can use torpor because we observed reversible decreases of body temperature (Tb) in fasted hamsters. To test this hypothesis we (i) randomly exposed fasted summer-acclimated hamsters to ambient temperatures (Tas) ranging from 5 to 30°C or (ii) supplied them with different rations of food at Ta 23°C. All desert hamsters showed heterothermy with the lowest mean Tb of 31.4±1.9°C (minimum, 29.0°C) and 31.8±2.0°C (minimum, 29.0°C) when fasted at Ta of 23°C and 19°C, respectively. Below Ta 19°C, the lowest Tb and metabolic rate increased and the proportion of hamsters using heterothermy declined. At Ta 5°C, nearly all hamsters remained normothermic by increasing heat production, suggesting that the heterothermy only occurs in moderately cold conditions, perhaps to avoid freezing at extremely low Tas. During heterothermy, Tbs below 31°C with metabolic rates below 25% of those during normothermia were detected in four individuals at Ta of 19°C and 23°C. Consequently, by definition, our observations confirm that fasted desert hamsters are capable of shallow daily torpor. The negative correlation between the lowest Tbs and amount of food supply shows that heterothermy was mainly triggered by food shortage. Our data indicate that summer-acclimated desert hamsters can express fasting-induced shallow daily torpor, which may be of significance for energy conservation and survival in the wild.
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Affiliation(s)
- Qing-Sheng Chi
- State Key Laboratory of Integrated Management for Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xin-Rong Wan
- State Key Laboratory of Integrated Management for Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - De-Hua Wang
- State Key Laboratory of Integrated Management for Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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17
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Geiser F, Gasch K, Bieber C, Stalder GL, Gerritsmann H, Ruf T. Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor. ACTA ACUST UNITED AC 2016; 219:2166-72. [PMID: 27207637 DOI: 10.1242/jeb.137828] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/02/2016] [Indexed: 01/22/2023]
Abstract
Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (>30%) when basking at ambient temperatures (Ta) of ∼15 and 0°C. Interestingly, body temperature (Tb) also was significantly reduced from 34.7±0.6°C (Ta 15°C, not basking) to 30.4±2.0°C (Ta 0°C, basking), which resulted in an extremely low (<50% of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at Ta 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average Tb of 22.0±2.6°C; movement to the basking lamp occurred at Tb<20.0°C. Energy expenditure for rewarming was significantly reduced (by >50%) during radiant heat-assisted rewarming; however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and Tb during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting Tb and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts, where basking is common, but also for P. sungorus and probably other cold-climate mammals.
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Affiliation(s)
- Fritz Geiser
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Kristina Gasch
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Claudia Bieber
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Gabrielle L Stalder
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Hanno Gerritsmann
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
| | - Thomas Ruf
- Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine Vienna, Savoyenstrasse 1, Vienna 1160, Austria
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18
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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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19
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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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