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Mota CMD, Madden CJ. Neural circuits of long-term thermoregulatory adaptations to cold temperatures and metabolic demands. Nat Rev Neurosci 2024; 25:143-158. [PMID: 38316956 DOI: 10.1038/s41583-023-00785-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2023] [Indexed: 02/07/2024]
Abstract
The mammalian brain controls heat generation and heat loss mechanisms that regulate body temperature and energy metabolism. Thermoeffectors include brown adipose tissue, cutaneous blood flow and skeletal muscle, and metabolic energy sources include white adipose tissue. Neural and metabolic pathways modulating the activity and functional plasticity of these mechanisms contribute not only to the optimization of function during acute challenges, such as ambient temperature changes, infection and stress, but also to longitudinal adaptations to environmental and internal changes. Exposure of humans to repeated and seasonal cold ambient conditions leads to adaptations in thermoeffectors such as habituation of cutaneous vasoconstriction and shivering. In animals that undergo hibernation and torpor, neurally regulated metabolic and thermoregulatory adaptations enable survival during periods of significant reduction in metabolic rate. In addition, changes in diet can activate accessory neural pathways that alter thermoeffector activity. This knowledge may be harnessed for therapeutic purposes, including treatments for obesity and improved means of therapeutic hypothermia.
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Affiliation(s)
- Clarissa M D Mota
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, USA
| | - Christopher J Madden
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, USA.
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2
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Speakman JR, Hall KD. Models of body weight and fatness regulation. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220231. [PMID: 37661735 PMCID: PMC10475878 DOI: 10.1098/rstb.2022.0231] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/13/2023] [Indexed: 09/05/2023] Open
Abstract
Body weight and fatness appear to be regulated phenomena. Several different theoretical models are available to capture the essence of this idea. These include the set-point, dynamic equilibrium, adiposity force, control theory-settling point, Hall-Guo, operation point and dual intervention point (DIP) models. The set-point model posits a single reference point around which levels of fat are regulated. The dynamic equilibrium model suggests that the apparent regulation of body fat around a reference point is an illusion owing to the necessary impacts of weight change on energy expenditure. Control theory focuses on the importance of feedback gain and suggests set-point and dynamic equilibrium are ends of a continuum of feedback gain. Control theory models have also been called 'settling point' models. The Hall-Guo, operation point and DIP models also bring together the set-point and dynamic equilibrium ideas into a single framework. The DIP proposes a zone of indifference where dynamic equilibrium 'regulation' predominates, bounded by upper and lower intervention points beyond which physiological mechanisms are activated. The drifty gene hypothesis is an idea explaining where this individual variation in the upper intervention point might come from. We conclude that further experiments to test between the models are sorely required. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.
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Affiliation(s)
- John R. Speakman
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong Province, 518055, People's Republic of China
- School of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, People's Republic of China
- China Medical University, Shenyang, Liaoning Province, 110122, People's Republic of China
| | - Kevin D. Hall
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
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3
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2022; 6:313. [PMID: 35087956 PMCID: PMC8764563 DOI: 10.12688/wellcomeopenres.17379.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2022] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to review the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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Affiliation(s)
- Michael Ambler
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Timna Hitrec
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Anthony Pickering
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
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4
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Ren Y, Song S, Liu X, Yang M. Phenotypic changes in the metabolic profile and adiponectin activity during seasonal fattening and hibernation in female Daurian ground squirrels (Spermophilus dauricus). Integr Zool 2020; 17:297-310. [PMID: 33190391 DOI: 10.1111/1749-4877.12504] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Seasonal hibernation has provided an opportunity to study animals' phenotypic plasticity in adaptation to changing environment. In the present study focusing on the female Daurian ground squirrel (Spermophilus dauricus)-a well demonstrated seasonal hibernator-we examined their behavioral, morphological, and metabolic changes during fattening, hibernation, and emergence. Our data indicated high levels of food intake, fat deposition, and body mass increases during fattening compared to hibernation. The levels of serum glucose and triglycerides were also higher during fattening than during hibernation and emergence. Interestingly, although squirrels showed signs of obesity and elevated triglycerides in serum during fattening, triglyceride levels in the liver and skeletal muscles remained unchanged. Our data also indicated that adiponectin levels in serum and cerebrospinal fluid were different between fattening and hibernation. Levels of adiponectin receptor 1 in the skeletal muscle remained low during fattening but peaked in late hibernation. In contrast, adiponectin receptor 2 in the liver showed a steady increase during fattening, which was followed by a significant decrease at early hibernation. Our data indicate that adiponectin may play an important role in preventing heterotopic fat accumulation in a receptor- and organ-specific manner, as well as in facilitating the switch from glucose metabolism to lipid metabolism during fattening and hibernation in female Daurian ground squirrels.
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Affiliation(s)
- Yue Ren
- College of life Sciences, Shenyang Normal University, Shenyang, China
| | - Shiyi Song
- College of life Sciences, Shenyang Normal University, Shenyang, China
| | - Xinyu Liu
- College of life Sciences, Shenyang Normal University, Shenyang, China
| | - Ming Yang
- College of life Sciences, Shenyang Normal University, Shenyang, China
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Xing X, Liu S, Liu XY, Yang M, Wang DH. Cold exposure increased hypothalamic orexigenic neuropeptides but not food intake in fattening Daurian ground squirrels. ZOOLOGY 2020; 143:125834. [PMID: 32947220 DOI: 10.1016/j.zool.2020.125834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 08/11/2020] [Accepted: 08/14/2020] [Indexed: 11/19/2022]
Abstract
Energy balance and thermoregulation in many fat-storing seasonal hibernators show a circannual rhythm. To understand the physiological mechanisms of the seasonal pre-hibernation fattening related to the regulation of energy expenditure and thermogenesis, we cold-exposed fattening Daurian ground squirrels (Spermophilus dauricus) in late summer for 3 weeks. We predicted that cold-exposed squirrels would increase food intake rather than express torpor to accommodate both fattening and thermoregulatory fuel allocation. Food intake and body mass were quantified. After 3 weeks, body compositions, serum leptin concentration, expression of hypothalamic neuropeptides related to regulation of energy balance and uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) were measured. There was no change in body mass after 3-weeks of cold exposure. Hypothalamic orexigenic neuropeptides and UCP1 levels in BAT were up-regulated after cold exposure. Food intake, serum leptin concentration and the expression of leptin signal suppressors, suppressor of cytokine signaling 3 and protein tyrosine phosphatase 1B, in hypothalamus showed no differences compared with controls. The core body temperature was unaffected by cold exposure. Our data suggest that cold exposure affected fattening mainly because of the increased heat loss, whereas energy balance and thermoregulation are under control of a strong circannual rhythm in the Daurian ground squirrels.
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Affiliation(s)
- Xin Xing
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Sciences, Peking University, Beijing, 100871, China
| | - Shuai Liu
- College of Life Science, Shenyang Normal University, Shenyang, 110034, China
| | - Xin-Yu Liu
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China; College of Life Science, Shenyang Normal University, Shenyang, 110034, China
| | - Ming Yang
- College of Life Science, Shenyang Normal University, Shenyang, 110034, China.
| | - De-Hua Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, China.
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Mohr SM, Bagriantsev SN, Gracheva EO. Cellular, Molecular, and Physiological Adaptations of Hibernation: The Solution to Environmental Challenges. Annu Rev Cell Dev Biol 2020; 36:315-338. [PMID: 32897760 DOI: 10.1146/annurev-cellbio-012820-095945] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Thriving in times of resource scarcity requires an incredible flexibility of behavioral, physiological, cellular, and molecular functions that must change within a relatively short time. Hibernation is a collection of physiological strategies that allows animals to inhabit inhospitable environments, where they experience extreme thermal challenges and scarcity of food and water. Many different kinds of animals employ hibernation, and there is a spectrum of hibernation phenotypes. Here, we focus on obligatory mammalian hibernators to identify the unique challenges they face and the adaptations that allow hibernators to overcome them. This includes the cellular and molecular strategies used to combat low environmental and body temperatures and lack of food and water. We discuss metabolic, neuronal, and hormonal cues that regulate hibernation and how they are thought to be coordinated by internal clocks. Last, we touch on questions that are left to be addressed in the field of hibernation research. Studies from the last century and more recent work reveal that hibernation is not simply a passive reduction in body temperature and vital parameters but rather an active process seasonally regulated at the molecular, cellular, and organismal levels.
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Affiliation(s)
- Sarah M Mohr
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA; .,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06510, USA;
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA;
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA; .,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06510, USA;
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Oliver SR, Anderson KJ, Hunstiger MM, Andrews MT. Turning down the heat: Down-regulation of sarcolipin in a hibernating mammal. Neurosci Lett 2018; 696:13-19. [PMID: 30528880 DOI: 10.1016/j.neulet.2018.11.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/30/2018] [Accepted: 11/30/2018] [Indexed: 02/01/2023]
Abstract
Hibernation in mammals is a whole-body phenotype that involves profound reductions in oxygen consumption, metabolic reactions, core body temperature, neural activity and heart rate. An important aspect of mammalian hibernation is the ability to reverse this state of hypothermic torpor by rewarming and subsequent arousal. Brown adipose tissue (BAT) and skeletal muscle shivering have been characterized as the predominant driving forces for thermogenesis during arousal. Conversely, the thermogenic contribution of these organs needs to be minimized as hibernating mammals enter torpor. Because skeletal muscle accounts for approximately 40% of the dry mass of the typical mammalian body, we aim to broaden the spotlight to include the importance of down-regulating skeletal muscle non-shivering thermogenesis during hibernation to allow for whole-body cooling and long-term maintenance of a depressed core body temperature when the animal is in torpor. This minireview will briefly describe the current understanding of thermoregulation in hibernating mammals and present new preliminary data on the importance of skeletal muscle and the micro-peptide sarcolipin as a major thermogenic target.
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Affiliation(s)
- S Ryan Oliver
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
| | - Kyle J Anderson
- Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, MN 55812, USA.
| | - Moriah M Hunstiger
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
| | - Matthew T Andrews
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA.
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Abstract
Human obesity has a large genetic component, yet has many serious negative consequences. How this state of affairs has evolved has generated wide debate. The thrifty gene hypothesis was the first attempt to explain obesity as a consequence of adaptive responses to an ancient environment that in modern society become disadvantageous. The idea is that genes (or more precisely, alleles) predisposing to obesity may have been selected for by repeated exposure to famines. However, this idea has many flaws: for instance, selection of the supposed magnitude over the duration of human evolution would fix any thrifty alleles (famines kill the old and young, not the obese) and there is no evidence that hunter-gatherer populations become obese between famines. An alternative idea (called thrifty late) is that selection in famines has only happened since the agricultural revolution. However, this is inconsistent with the absence of strong signatures of selection at single nucleotide polymorphisms linked to obesity. In parallel to discussions about the origin of obesity, there has been much debate regarding the regulation of body weight. There are three basic models: the set-point, settling point and dual-intervention point models. Selection might act against low and high levels of adiposity because food unpredictability and the risk of starvation selects against low adiposity whereas the risk of predation selects against high adiposity. Although evidence for the latter is quite strong, evidence for the former is relatively weak. The release from predation ∼2-million years ago is suggested to have led to the upper intervention point drifting in evolutionary time, leading to the modern distribution of obesity: the drifty gene hypothesis. Recent critiques of the dual-intervention point/drifty gene idea are flawed and inconsistent with known aspects of energy balance physiology. Here, I present a new formulation of the dual-intervention point model. This model includes the novel suggestion that food unpredictability and starvation are insignificant factors driving fat storage, and that the main force driving up fat storage is the risk of disease and the need to survive periods of pathogen-induced anorexia. This model shows why two independent intervention points are more likely to evolve than a single set point. The molecular basis of the lower intervention point is likely based around the leptin pathway signalling. Determining the molecular basis of the upper intervention point is a crucial key target for future obesity research. A potential definitive test to separate the different models is also described.
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Affiliation(s)
- John R Speakman
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China .,Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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Martin R, Shapiro JI. Role of adipocytes in hypertension. World J Hypertens 2016; 6:66-75. [DOI: 10.5494/wjh.v6.i2.66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 06/02/2016] [Indexed: 02/06/2023] Open
Abstract
Although it has known for some time that obesity is associated with salt sensitivity and hypertension, recent data suggests that the adipocyte may actually be the proximate cause of this physiological changes. In the following review, the data demonstrating this association as well as the potentially operative pathophysiological mechanisms are reviewed and discussed.
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Xing X, Tang GB, Sun MY, Yu C, Song SY, Liu XY, Yang M, Wang DH. Leptin regulates energy intake but fails to facilitate hibernation in fattening Daurian ground squirrels (Spermophilus dauricus). J Therm Biol 2016; 57:35-43. [PMID: 27033037 DOI: 10.1016/j.jtherbio.2016.01.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 01/26/2016] [Indexed: 10/22/2022]
Abstract
Body fat storage before hibernation affects the timing of immergence in Daurian ground squirrels (Spermophilus dauricus). Leptin is an adipose signal and plays vital role in energy homeostasis mainly by action in brain. To test the hypothesis that leptin plays a role in facilitating the process of hibernation, squirrels were administrated with recombinant murine leptin (1μg/day) through intracerebroventricular (ICV) injection for 12 days during fattening. From day 7 to 12, animals were moved into a cold room (5±1°C) with constant darkness which functioned as hibernaculum. Energy intake, body mass and core body temperature (Tb) were continuously monitored throughout the course of experiment. Resting metabolic rate (RMR) was measured under both warm and cold conditions. At the end of leptin administration, we measured the serum concentration of hormones related to energy regulation, mRNA expression of hypothalamic neuropeptides and uncoupling protein 1 (UCP1) levels in brown adipose tissue (BAT). Our results showed that during leptin administration, the cumulative food intake and increase of body mass were suppressed while Tb and RMR were unaltered. The proportion of torpid squirrels was not different between two groups. At the end of leptin administration, the expressions of hypothalamic neuropeptide Y and agouti gene-related protein were suppressed. There were no differences in UCP1 mRNA expression or protein content in BAT between groups. Our data suggest that leptin can affect energy intake via hypothalamic neuropeptides, but is not involved in the initiation of hibernation in fattening Daurian ground squirrels.
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Affiliation(s)
- Xin Xing
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Gang-Bin Tang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang, Beijing 100101, China
| | - Ming-Yue Sun
- College of Life Science, Shenyang Normal University, 253 Huanghe North Street, Shenyang 110034, China
| | - Chao Yu
- College of Life Science, Shenyang Normal University, 253 Huanghe North Street, Shenyang 110034, China
| | - Shi-Yi Song
- College of Life Science, Shenyang Normal University, 253 Huanghe North Street, Shenyang 110034, China
| | - Xin-Yu Liu
- College of Life Science, Shenyang Normal University, 253 Huanghe North Street, Shenyang 110034, China
| | - Ming Yang
- College of Life Science, Shenyang Normal University, 253 Huanghe North Street, Shenyang 110034, China.
| | - De-Hua Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang, Beijing 100101, China.
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Xu MM, Wang DH. Water deprivation up-regulates urine osmolality and renal aquaporin 2 in Mongolian gerbils (Meriones unguiculatus). Comp Biochem Physiol A Mol Integr Physiol 2016; 194:37-44. [PMID: 26806059 DOI: 10.1016/j.cbpa.2016.01.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 01/16/2016] [Accepted: 01/16/2016] [Indexed: 01/30/2023]
Abstract
To better understand how desert rodents adapt to water scarcity, we examined urine osmolality, renal distribution and expression of aquaporins (AQPs) in Mongolian gerbils (Meriones unguiculatus) during 7 days of water deprivation (WD). Urine osmolality of the gerbils during WD averaged 7503 mOsm kg(-1). Renal distributions of AQP1, AQP2, and AQP3 were similar to that described in other rodents. After the 7 day WD, renal AQP2 was up-regulated, while resting metabolic rate and total evaporative water loss decreased by 43% and 36%, respectively. Our data demonstrated that Mongolian gerbils showed high urine concentration, renal AQPs expression and body water conservation to cope with limited water availability, which may be critical for their survival during dry seasons in cold deserts.
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Affiliation(s)
- Meng-Meng Xu
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
| | - De-Hua Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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