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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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2
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Zhao Y, Cheng R, Zhao Y, Ge W, Yang Y, Ding Z, Xu X, Wang Z, Wu Z, Zhang J. Type 2 diabetic mice enter a state of spontaneous hibernation-like suspended animation following accumulation of uric acid. J Biol Chem 2021; 297:101166. [PMID: 34487763 PMCID: PMC8484811 DOI: 10.1016/j.jbc.2021.101166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 08/28/2021] [Accepted: 09/02/2021] [Indexed: 11/25/2022] Open
Abstract
Hibernation is an example of extreme hypometabolic behavior. How mammals achieve such a state of suspended animation remains unclear. Here we show that several strains of type 2 diabetic mice spontaneously enter into hibernation-like suspended animation (HLSA) in cold temperatures. Nondiabetic mice injected with ATP mimic the severe hypothermia analogous to that observed in diabetic mice. We identified that uric acid, an ATP metabolite, is a key molecular in the entry of HLSA. Uric acid binds to the Na+ binding pocket of the Na+/H+ exchanger protein and inhibits its activity, acidifying the cytoplasm and triggering a drop in metabolic rate. The suppression of uric acid biosynthesis blocks the occurrence of HLSA, and hyperuricemic mice induced by treatment with an uricase inhibitor can spontaneously enter into HLSA similar to that observed in type 2 diabetic mice. In rats and dogs, injection of ATP induces a reversible state of HLSA similar to that seen in mice. However, ATP injection fails to induce HLSA in pigs due to the lack of their ability to accumulate uric acid. Our results raise the possibility that nonhibernating mammals could spontaneously undergo HLSA upon accumulation of ATP metabolite, uric acid.
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Affiliation(s)
- Yang Zhao
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Rui Cheng
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Yue Zhao
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A∗STAR), Singapore
| | - Wenhao Ge
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Yunxia Yang
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Zhao Ding
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Xi Xu
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China
| | - Zhongqiu Wang
- Affiliated Hospital of Nanjing, University of Chinese Medicine, Nanjing, China
| | - Zhenguo Wu
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Jianfa Zhang
- Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing, China.
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3
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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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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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Osaka T. Hypothermia induced by inhibition of fatty acid metabolism in anesthetized rats: contributions of the forebrain and vagal afferents. Can J Physiol Pharmacol 2017; 95:652-660. [PMID: 28177663 DOI: 10.1139/cjpp-2016-0195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
2-Mercaptoacetate (MA) is an antimetabolic drug that inhibits the utilization of fatty acids as an energy source. The intravenous injection of MA (1.2 mmol·kg-1) elicited an increase in tail skin temperature and a decrease in body core temperature in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats, although administration of the same amount of NaCl did not. The respiratory exchange ratio was significantly higher after administration of MA than that after the saline treatment. On the other hand, heat production was increased by either the MA- or NaCl-injection, suggesting a nonspecific effect caused by the hyperosmolality of the solutions. These results indicate that the MA-induced hypothermia was caused by an increase in heat loss but not by a decrease in heat production. The amplitudes of heat loss responses to MA in rats fasted overnight were significantly smaller than those in fed ones, suggesting a mechanism for suppression of heat loss in the fasted state. Rats pretreated with vagotomy, capsaicin-induced desensitization of sensory nerve fibers or decerebration did not exhibit the MA-induced hypothermic responses. It is possible that the MA-induced heat loss and hypothermia were mediated by the vagal afferents and required the forebrain for the full expression of the responses.
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Affiliation(s)
- Toshimasa Osaka
- Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan.,Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan
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6
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Abstract
Many environmental conditions can constrain the ability of animals to obtain sufficient food energy, or transform that food energy into useful chemical forms. To survive extended periods under such conditions animals must suppress metabolic rate to conserve energy, water, or oxygen. Amongst small endotherms, this metabolic suppression is accompanied by and, in some cases, facilitated by a decrease in core body temperature-hibernation or daily torpor-though significant metabolic suppression can be achieved even with only modest cooling. Within some ectotherms, winter metabolic suppression exceeds the passive effects of cooling. During dry seasons, estivating ectotherms can reduce metabolism without changes in body temperature, conserving energy reserves, and reducing gas exchange and its inevitable loss of water vapor. This overview explores the similarities and differences of metabolic suppression among these states within adult animals (excluding developmental diapause), and integrates levels of organization from the whole animal to the genome, where possible. Several similarities among these states are highlighted, including patterns and regulation of metabolic balance, fuel use, and mitochondrial metabolism. Differences among models are also apparent, particularly in whether the metabolic suppression is intrinsic to the tissue or depends on the whole-animal response. While in these hypometabolic states, tissues from many animals are tolerant of hypoxia/anoxia, ischemia/reperfusion, and disuse. These natural models may, therefore, serve as valuable and instructive models for biomedical research.
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Affiliation(s)
- James F Staples
- Department of Biology, University of Western Ontario, London, Ontario, Canada
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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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Diedrich V, Kumstel S, Steinlechner S. Spontaneous daily torpor and fasting-induced torpor in Djungarian hamsters are characterized by distinct patterns of metabolic rate. J Comp Physiol B 2014; 185:355-66. [PMID: 25526676 DOI: 10.1007/s00360-014-0882-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 11/28/2014] [Accepted: 12/07/2014] [Indexed: 11/29/2022]
Abstract
The Djungarian hamster is a rodent species that expresses both spontaneous daily torpor (SDT) when acclimated to winter conditions as well as fasting-induced torpor (FIT) during summer. In an earlier report we argued that these two thermoregulatory phenomena differ in several parameters. In the present study, we further complete this comparison by showing that metabolic rate patterns differ between both SDT and FIT. SDT bouts were significantly longer and deeper compared to FIT bouts. Additionally, respiratory quotient measures support the view that SDT is entered from a state of energetic balance while FIT appears to be an emergency shutdown of energy demanding thermogenesis due to a shortage of energy sources. In a second experiment, we also confirm that brief periods of food restriction during the hamsters' torpor season increase the frequency of SDT, but do not affect its depth or duration. Although winter-acclimated animals could flexibly alter torpor frequency in order to stay in energetic balance, we also found evidence for torpor expression patterns that resembled FIT, rather than SDT. Consequently, if energetic challenges cannot be compensated with increased SDT expression any longer, the hamsters seem to be driven in a negative energy balance resulting in FIT as a last resort.
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Affiliation(s)
- Victoria Diedrich
- Institute of Zoology, University of Veterinary Medicine Hannover, Buenteweg 17, 30559, Hannover, Germany,
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Geiser F, Currie SE, O'Shea KA, Hiebert SM. Torpor and hypothermia: reversed hysteresis of metabolic rate and body temperature. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1324-9. [PMID: 25253085 DOI: 10.1152/ajpregu.00214.2014] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulated torpor and unregulated hypothermia are both characterized by substantially reduced body temperature (Tb) and metabolic rate (MR), but they differ physiologically. Although the remarkable, medically interesting adaptations accompanying torpor (e.g., tolerance for cold and ischemia, absence of reperfusion injury, and disuse atrophy) often do not apply to hypothermia in homeothermic species such as humans, the terms "torpor" and "hypothermia" are often used interchangeably in the literature. To determine how these states differ functionally and to provide a reliable diagnostic tool for differentiating between these two physiologically distinct states, we examined the interrelations between Tb and MR in a mammal (Sminthopsis macroura) undergoing a bout of torpor with those of the hypothermic response of a similar-sized juvenile rat (Rattus norvegicus). Our data show that under similar thermal conditions, 1) cooling rates differ substantially (approximately fivefold) between the two states; 2) minimum MR is approximately sevenfold higher during hypothermia than during torpor despite a similar Tb; 3) rapid, endogenously fuelled rewarming occurs in torpor but not hypothermia; and 4) the hysteresis between Tb and MR during warming and cooling proceeds in opposite directions in torpor and hypothermia. We thus demonstrate clear diagnostic physiological differences between these two states that can be used experimentally to confirm whether torpor or hypothermia has occurred. Furthermore, the data can clarify the results of studies investigating the ability of physiological or pharmacological agents to induce torpor. Consequently, we recommend using the terms "torpor" and "hypothermia" in ways that are consistent with the underlying regulatory differences between these two physiological states.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - Shannon E Currie
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - Kelly A O'Shea
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - Sara M Hiebert
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
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Geiser F, Klingenspor M, McAllan BM. A functional nexus between photoperiod acclimation, torpor expression and somatic fatty acid composition in a heterothermic mammal. PLoS One 2013; 8:e63803. [PMID: 23717487 PMCID: PMC3661731 DOI: 10.1371/journal.pone.0063803] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 04/05/2013] [Indexed: 11/18/2022] Open
Abstract
The seasonal changes in thermal physiology and torpor expression of many heterothermic mammals are controlled by photoperiod. As function at low body temperatures during torpor requires changes of tissue lipid composition, we tested for the first time whether and how fatty acids are affected by photoperiod acclimation in hamsters, Phodopus sungorus, a strongly photoperiodic species. We also examined changes in fatty acid composition in relation to those in morphology and thermal biology. Hamsters in short photoperiod had smaller reproductive organs and most had a reduced body mass in comparison to those in long photoperiod. Pelage colour of hamsters under short photoperiod was almost white while that of long photoperiod hamsters was grey-brown and black. Short photoperiod acclimation resulted in regular (28% of days) torpor use, whereas all hamsters in long photoperiod remained normothermic. The composition of total fatty acids differed between acclimation groups for brown adipose tissue (5 of 8 fatty acids), heart muscle (4 of 7 fatty acids) and leg muscle (3 of 11 fatty acids). Importantly, 54% of all fatty acids detected were correlated (r2 = 0.60 to 0.87) with the minimum surface temperature of individuals, but the responses of tissues differed. While some of the compositional changes of fatty acids were consistent with a ‘homeoviscous’ response, this was not the case for all, including the sums of saturated and unsaturated fatty acids, which did not differ between acclimation groups. Our data identify a possible nexus between photoperiod acclimation, morphology, reproductive biology, thermal biology and fatty acid composition. They suggest that some of the changes in thermal physiology are linked to the composition of tissue and organ fatty acids.
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Affiliation(s)
- Fritz Geiser
- Biologie-Zoologie, Philipps-University, Marburg, Germany.
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11
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Walton J, Grier A, Weil Z, Nelson R. Photoperiod and stress regulation of corticosteroid receptor, brain-derived neurotrophic factor, and glucose transporter GLUT3 mRNA in the hippocampus of male Siberian hamsters (Phodopus sungorus). Neuroscience 2012; 213:106-11. [DOI: 10.1016/j.neuroscience.2012.03.043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/27/2012] [Accepted: 03/30/2012] [Indexed: 11/29/2022]
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12
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Bouma HR, Verhaag EM, Otis JP, Heldmaier G, Swoap SJ, Strijkstra AM, Henning RH, Carey HV. Induction of torpor: mimicking natural metabolic suppression for biomedical applications. J Cell Physiol 2012; 227:1285-90. [PMID: 21618525 DOI: 10.1002/jcp.22850] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian hibernation consists of periods of depressed metabolism and reduced body temperature called "torpor" that are interspersed by normothermic arousal periods. Numerous cellular processes are halted during torpor, including transcription, translation, and ion homeostasis. Hibernators are able to survive long periods of low blood flow and body temperature followed by rewarming and reperfusion without overt signs of organ injury, which makes these animals excellent models for application of natural protective mechanisms to human medicine. This review examines efforts to induce torpor-like states in non-hibernating species using pharmacological compounds. Elucidating the underlying mechanisms of natural and pharmacologically induced torpor will speed the development of new clinical approaches to treat a variety of trauma and stress states in humans.
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Affiliation(s)
- Hjalmar R Bouma
- Department of Clinical Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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13
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Körtner G, Geiser F. The key to winter survival: daily torpor in a small arid-zone marsupial. Naturwissenschaften 2008; 96:525-30. [PMID: 19082573 DOI: 10.1007/s00114-008-0492-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 09/24/2008] [Accepted: 11/23/2008] [Indexed: 11/27/2022]
Abstract
Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter. All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T (a)) ranging from approximately -1 degrees C to 36 degrees C. Dunnarts usually entered torpor during the night and aroused at midday with the daily increase of T (a). Torpor was on average about twice as long (mean 11.0 +/- 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate the ecological significance of daily torpor in the wild.
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Affiliation(s)
- Gerhard Körtner
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia
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14
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Giroud S, Perret M, Le Maho Y, Momken I, Gilbert C, Blanc S. Gut hormones in relation to body mass and torpor pattern changes during food restriction and re-feeding in the gray mouse lemur. J Comp Physiol B 2008; 179:99-111. [DOI: 10.1007/s00360-008-0294-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 07/03/2008] [Accepted: 07/06/2008] [Indexed: 10/21/2022]
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15
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Abstract
The induction of hypometabolism in cells and organs to reduce ischemia damage holds enormous clinical promise in diverse fields, including treatment of stroke and heart attack. However, the thought that humans can undergo a severe hypometabolic state analogous to hibernation borders on science fiction. Some mammals can enter a severe hypothermic state during hibernation in which metabolic activity is extremely low, and yet full viability is restored when the animal arouses from such a state. To date, the underlying mechanism for hibernation or similar behaviors remains an enigma. The beneficial effect of hypothermia, which reduces cellular metabolic demands, has many well-established clinical applications. However, severe hypothermia induced by clinical drugs is extremely difficult and is associated with dramatically increased rates of cardiac arrest for nonhibernators. The recent discovery of a biomolecule, 5'-AMP, which allows nonhibernating mammals to rapidly and safely enter severe hypothermia could remove this impediment and enable the wide adoption of hypothermia as a routine clinical tool.
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Affiliation(s)
- Cheng Chi Lee
- Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030, USA.
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Workman JL, Weil ZM, Tuthill CR, Nelson RJ. Maternal pinealectomy increases depressive-like responses in Siberian hamster offspring. Behav Brain Res 2008; 189:387-91. [PMID: 18328579 DOI: 10.1016/j.bbr.2008.01.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 01/23/2008] [Accepted: 01/28/2008] [Indexed: 01/22/2023]
Abstract
This study investigated the effect of maternal pinealectomy and postnatal pinealectomy on affective responses. Siberian hamsters were born to either pinealectomized or sham-operated dams and then underwent pinealectomy or a sham operation. Maternal pinealectomy increased depressive-like responses of offspring in the forced swim test. Maternal pinealectomy increased rearing behaviour and postnatal pinealectomy increased locomotor behaviour in the open field test. These results suggest that prenatal melatonin organizes adult affective responses.
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Affiliation(s)
- Joanna L Workman
- Department of Psychology, The Ohio State University, Columbus, OH 43210, USA.
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Braulke LJ, Klingenspor M, DeBarber A, Tobias SC, Grandy DK, Scanlan TS, Heldmaier G. 3-Iodothyronamine: a novel hormone controlling the balance between glucose and lipid utilisation. J Comp Physiol B 2007; 178:167-77. [PMID: 17912534 DOI: 10.1007/s00360-007-0208-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 08/22/2007] [Accepted: 08/22/2007] [Indexed: 10/22/2022]
Abstract
3-Iodothyronamine is considered as a derivate of thyroid hormone as a result of enzymatic deiodination and decarboxylation. The physiological role of thyronamine (T1AM) is not known. The aim of this study was to analyze the metabolic response to T1AM in the Djungarian hamster Phodopus sungorus. We measured the influence of T1AM (50 mg/kg) on metabolic rate (VO(2)), body temperature (T (b)) and respiratory quotient (RQ) in this species and in BL/6 mice. T1AM treated hamsters as well as the mice showed a rapid decrease in VO(2) and T (b), accompanied by a reduction of RQ from normal values of about approximately 0.9 to approximately 0.70 for several hours. This indicates that carbohydrate utilisation is blocked by the injection of T1AM and that metabolic pathways are rerouted from carbohydrate to lipid utilisation in response to T1AM. This assumption was further supported by the observation that the treatment of T1AM caused ketonuria and a significant loss of body fat. Our results indicate that T1AM has the potential to control the balance between glucose and lipid utilisation in vivo.
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Affiliation(s)
- L J Braulke
- Department of Biology, Philipps-University Marburg, Marburg, Germany.
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18
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Drew KL, Buck CL, Barnes BM, Christian SL, Rasley BT, Harris MB. Central nervous system regulation of mammalian hibernation: implications for metabolic suppression and ischemia tolerance. J Neurochem 2007; 102:1713-1726. [PMID: 17555547 PMCID: PMC3600610 DOI: 10.1111/j.1471-4159.2007.04675.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Torpor during hibernation defines the nadir of mammalian metabolism where whole animal rates of metabolism are decreased to as low as 2% of basal metabolic rate. This capacity to decrease profoundly the metabolic demand of organs and tissues has the potential to translate into novel therapies for the treatment of ischemia associated with stroke, cardiac arrest or trauma where delivery of oxygen and nutrients fails to meet demand. If metabolic demand could be arrested in a regulated way, cell and tissue injury could be attenuated. Metabolic suppression achieved during hibernation is regulated, in part, by the central nervous system through indirect and possibly direct means. In this study, we review recent evidence for mechanisms of central nervous system control of torpor in hibernating rodents including evidence of a permissive, hibernation protein complex, a role for A1 adenosine receptors, mu opiate receptors, glutamate and thyrotropin-releasing hormone. Central sites for regulation of torpor include the hippocampus, hypothalamus and nuclei of the autonomic nervous system. In addition, we discuss evidence that hibernation phenotypes can be translated to non-hibernating species by H(2)S and 3-iodothyronamine with the caveat that the hypothermia, bradycardia, and metabolic suppression induced by these compounds may or may not be identical to mechanisms employed in true hibernation.
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Affiliation(s)
- Kelly L. Drew
- Institute of Arctic Biology, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
- Department of Chemistry and Biochemistry, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - C. Loren Buck
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska, USA
| | - Brian M. Barnes
- Institute of Arctic Biology, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Sherri L. Christian
- Institute of Arctic Biology, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Brian T. Rasley
- Department of Chemistry and Biochemistry, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Michael B. Harris
- Institute of Arctic Biology, Alaska Basic Neuroscience Program, University of Alaska Fairbanks, Fairbanks, Alaska, USA
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19
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Geiser F, McAllan BM, Kenagy GJ, Hiebert SM. Photoperiod affects daily torpor and tissue fatty acid composition in deer mice. Naturwissenschaften 2006; 94:319-25. [PMID: 17160415 DOI: 10.1007/s00114-006-0193-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Revised: 10/21/2006] [Accepted: 10/29/2006] [Indexed: 11/26/2022]
Abstract
Photoperiod and dietary lipids both influence thermal physiology and the pattern of torpor of heterothermic mammals. The aim of the present study was to test the hypothesis that photoperiod-induced physiological changes are linked to differences in tissue fatty acid composition of deer mice, Peromyscus maniculatus ( approximately 18-g body mass). Deer mice were acclimated for >8 weeks to one of three photoperiods (LD, light/dark): LD 8:16 (short photoperiod), LD 12:12 (equinox photoperiod), and LD 16:8 (long photoperiod). Deer mice under short and equinox photoperiods showed a greater occurrence of torpor than those under long photoperiods (71, 70, and 14%, respectively). The duration of torpor bouts was longest in deer mice under short photoperiod (9.3 +/- 2.6 h), intermediate under equinox photoperiod (5.1 +/- 0.3 h), and shortest under long photoperiod (3.7 +/- 0.6 h). Physiological differences in torpor use were associated with significant alterations of fatty acid composition in approximately 50% of the major fatty acids from leg muscle total lipids, whereas white adipose tissue fatty acid composition showed fewer changes. Our results provide the first evidence that physiological changes due to photoperiod exposure do result in changes in lipid composition in the muscle tissue of deer mice and suggest that these may play a role in survival of low body temperature and metabolic rate during torpor, thus, enhancing favourable energy balance over the course of the winter.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia.
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Geiser F, Law BS, Körtner G. Daily torpor in relation to photoperiod in a subtropical blossom-bat, Syconycteris australis (Megachiroptera). J Therm Biol 2005. [DOI: 10.1016/j.jtherbio.2005.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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21
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Abstract
Certain neurotropic viruses can invade the nervous system of their hosts and spread in chains of synaptically connected neurons. Consequently, it is possible to identify entire hierarchically connected circuits within an animal. In this review, we discuss the use of neurotropic herpesviruses as neuronal tract tracers. Although a variety of tract tracing viruses are available, each with its own unique infection characteristics, we focus on the widespread use of attenuated strains of pseudorabies virus (PRV), a swine herpesvirus with a broad host range. In particular, we focus on new applications of PRV for tract tracing including use of multiple infections by PRV reporter viruses to test for circuit convergence/divergence within the same animal. We provide examples of these combined application techniques within the context of an animal model to study the naturally occurring reversal of seasonal obesity in Siberian hamsters.
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Affiliation(s)
- C Kay Song
- Department of Biology, Neurobiology and Behavior Program, Georgia State University, 24 Peachtree Center Ave. NE, Atlanta, GA 30302-4010, USA
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22
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Bae HH, Larkin JE, Zucker I. Juvenile Siberian Hamsters Display Torpor and Modified Locomotor Activity and Body Temperature Rhythms in Response to Reduced Food Availability. Physiol Biochem Zool 2003; 76:858-67. [PMID: 14988801 DOI: 10.1086/381462] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2003] [Indexed: 11/04/2022]
Abstract
Siberian hamsters as young as 16 and 28 d displayed torpor in response to treatment with 2,500 mg/kg 2-deoxy-D-glucose and reduced food availability, respectively. In addition, most food-restricted hamsters displayed increased locomotor activity and elevated body temperatures in the 3 h immediately preceding daily food delivery. This anticipatory activity disappeared within a few days of reimposition of ad lib. feeding. Torpor first appeared spontaneously at approximately 13 wk of age in hamsters fed ad lib. and maintained in short day lengths. The onset of this "spontaneous" torpor was unaffected by the hamsters' history of food restriction before age 2 mo. Siberian hamsters born late in the breeding season can conserve energy by undergoing torpor immediately after weaning when they contend with food shortages and concurrent energetic challenges imposed by growth requirements and low ambient temperatures.
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Affiliation(s)
- Helen H Bae
- Group in Endocrinology, Department of Integrative Biology, University of California, Berkeley, CA 94720-1650, USA
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Bae HH, Stamper JL, Heydorn EC, Zucker I, Dark J. Role of area postrema in control of torpor in Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 2000; 279:R591-8. [PMID: 10938250 DOI: 10.1152/ajpregu.2000.279.2.r591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Siberian hamsters undergo torpor during the short days of winter and in response to glucoprivation or food restriction. We tested whether the area postrema and the adjacent nucleus of the solitary tract (hereafter the AP), which monitor metabolic fuel availability, also control the onset of torpor. Siberian hamsters that had manifested torpor spontaneously or had entered torpor in response to 2-deoxy-D-glucose (2-DG) treatment were subjected to area postrema ablations (APx). Hamsters continued to display torpor postoperatively; most features of torpor were unaffected by APx. The AP is not necessary for expression of torpor elicited by short day lengths or metabolic challenge. In contrast, decreases in food intake manifested by hamsters treated with 2-DG were counteracted by APx. In Siberian hamsters, the AP appears to mediate effects of 2-DG on food intake but not torpor.
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Affiliation(s)
- H H Bae
- Group in Endocrinology, University of California, Berkeley 94720, USA.
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