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Hudson NJ, Cramp RL, Franklin CE. Dramatic genome-wide reprogramming of mRNA in hypometabolic muscle. Comp Biochem Physiol B Biochem Mol Biol 2024; 272:110952. [PMID: 38355035 DOI: 10.1016/j.cbpb.2024.110952] [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: 11/16/2023] [Revised: 01/17/2024] [Accepted: 02/10/2024] [Indexed: 02/16/2024]
Abstract
In response to seasonal droughts, the green striped burrowing frog Cyclorana alboguttata enters a reversible hypometabolic state called aestivation where heart rate and oxygen consumption can be reduced despite warm (>25C°) ambient temperatures. With a view to understanding molecular mechanisms we profiled aestivating versus control gastrocnemius muscle using mRNA sequencing. This indicated an extensive metabolic reprogramming, with nearly a quarter of the entire transcriptome (3996 of 16,960 mRNA) exhibiting a nominal >2-fold change. Consistent with a physiological adaptation to spare carbohydrate reserves, carbohydrate catabolism was systemically downregulated. A 630-fold downregulation of ENO3 encoding the enolase enzyme was most striking. The 590 frog orthologs of mRNA encoding the mitoproteome were, viewed as a population, significantly downregulated during aestivation, although not to the same extent as mRNA encoding carbohydrate catabolism. Prominent examples include members of the TCA cycle (IDH2), electron transport chain (NDUFA6), the ATP synthase complex (ATP5F1B) and ADP/ATP intracellular transport (SLC25A4). Moreover, mRNA derived from the mt genome itself (e.g. mt-ND1) were also downregulated. Most prominent among the upregulated mRNA are those encoding aspects of regulated proteolysis including the proteosome (e.g. PSME4L), peptidases (USP25), atrogins (FBXO32) and ubiquitination (VCP). Finally, we note the ∼5-fold upregulation of the mRNA EIFG3 that encodes part of the EIF4F complex. This possesses global control of protein synthesis. Given protein synthesis is repressed in aestivating frogs this indicates the skeletal musculature is poised for accelerated translation of mRNA upon emergence, supporting a strategy to rapidly restore function when the summer rains come.
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Affiliation(s)
- Nicholas J Hudson
- School of Agriculture and Food Sustainability, The University of Queensland, Gatton, Queensland 4343, Australia.
| | - Rebecca L Cramp
- School of the Environment, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Craig E Franklin
- School of the Environment, The University of Queensland, St. Lucia, Queensland 4072, Australia. https://twitter.com/Franklin_EcoLab
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2
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Zhang K, Cao J, Zhao Z. Fat accumulation in striped hamsters (Cricetulus barabensis) reflects the temperature of prior cold acclimation. Front Zool 2024; 21:4. [PMID: 38350982 PMCID: PMC10865701 DOI: 10.1186/s12983-024-00523-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 01/30/2024] [Indexed: 02/15/2024] Open
Abstract
BACKGROUND Proper adjustments of metabolic thermogenesis play an important role in thermoregulation in endotherm to cope with cold and/or warm ambient temperatures, however its roles in energy balance and fat accumulation remain uncertain. Our study aimed to investigate the effect of previous cold exposure (10 and 0 °C) on the energy budgets and fat accumulation in the striped hamsters (Cricetulus barabensis) in response to warm acclimation. The body mass, energy intake, resting metabolic rate (RMR) and nonshivering thermogenesis (NST), serum thyroid hormone levels (THs: T3 and T4), and the activity of brown adipose tissue (BAT), indicated by cytochrome c oxidase (COX) activity and uncoupling protein 1 (ucp1) expression, were measured following exposure to the cold (10 °C and 0 °C) and transition to the warm temperature (30 °C). RESULTS The hamsters at 10 °C and 0 °C showed significant increases in energy intake, RMR and NST, and a considerable reduction in body fat than their counterparts kept at 21 °C. After being transferred from cold to warm temperature, the hamsters consumed less food, and decreased RMR and NST, but they significantly increased body fat content. Interestingly, the hamsters that were previously exposed to the colder temperature showed significantly more fat accumulation after transition to the warm. Serum T3 levels, BAT COX activity and ucp1 mRNA expression were significantly increased following cold exposure, and were considerably decreased after transition to the warm. Furthermore, body fat content was negatively correlated with serum T3 levels, BAT COX activity and UCP1 expression. CONCLUSION The data suggest that the positive energy balance resulting from the decreased RMR and NST in BAT under the transition from the cold to the warm plays important roles in inducing fat accumulation. The extent of fat accumulation in the warm appears to reflect the temperature of the previous cold acclimation.
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Affiliation(s)
- Kaiyuan Zhang
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou, 325035, China
| | - Jing Cao
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou, 325035, China
| | - Zhijun Zhao
- College of Life and Environmental Science, Zhejiang Provincial Key Laboratory for Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou, 325035, China.
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Jankovic A, Kalezic A, Korac A, Buzadzic B, Storey KB, Korac B. Integrated Redox-Metabolic Orchestration Sustains Life in Hibernating Ground Squirrels. Antioxid Redox Signal 2024; 40:345-368. [PMID: 36802926 DOI: 10.1089/ars.2021.0277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Significance: The ultimate manifestations of life, birth, survival under various environmental pressures and death are based on bioenergetics. Hibernation is a unique survival strategy for many small mammals that is characterised by severe metabolic depression and transition from euthermia to hypothermia (torpor) at body temperatures close to 0°C. These manifestations of life were made possible by the remarkable "social" behavior of biomolecules during billions of years of evolution: the evolution of life with oxygen. Oxygen was necessary for energy production and the evolutionary explosion of aerobic organisms. Recent Advances: Nevertheless, reactive oxygen species, formed through oxidative metabolism, are dangerous-they can kill a cell and, on the other hand, play a plethora of fundamentally valuable roles. Therefore, the evolution of life depended on energy metabolism and redox-metabolic adaptations. The more extreme the conditions for survival are, the more sophisticated the adaptive responses of organisms become. Hibernation is a beautiful illustration of this principle. Hibernating animals use evolutionarily conserved molecular mechanisms to survive adverse environmental conditions, including reducing body temperature to ambient levels (often to ∼0°C) and severe metabolic depression. This long-built secret of life lies at the intersection of oxygen, metabolism, and bioenergetics, and hibernating organisms have learned to exploit all the underlying capacities of molecular pathways to survive. Critical Issues: Despite such drastic changes in phenotype, tissues and organs of hibernators sustain no metabolic or histological damage during hibernation or upon awakening from hibernation. This was made possible by the fascinating integration of redox-metabolic regulatory networks whose molecular mechanisms remain undisclosed to this day. Future Directions: Discovering these molecular mechanisms is not warranted only to understand hibernation in itself but to help explain complex medical conditions (hypoxia/reoxygenation, organ transplantation, diabetes, and cancer) and to even help overcome limitations associated with space travel. This is a review of integrated redox-metabolic orchestration in hibernation. Antioxid. Redox Signal. 40, 345-368.
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Affiliation(s)
- Aleksandra Jankovic
- Department of Physiology, Institute for Biological Research "Sinisa Stankovic," National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Andjelika Kalezic
- Department of Physiology, Institute for Biological Research "Sinisa Stankovic," National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | | | - Biljana Buzadzic
- Department of Physiology, Institute for Biological Research "Sinisa Stankovic," National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | | | - Bato Korac
- Department of Physiology, Institute for Biological Research "Sinisa Stankovic," National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
- Faculty of Biology, University of Belgrade, Belgrade, Serbia
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Nowack J, Stawski C, Geiser F, Levesque DL. Rare and Opportunistic Use of Torpor in Mammals-An Echo from the Past? Integr Comp Biol 2023; 63:1049-1059. [PMID: 37328423 PMCID: PMC10714912 DOI: 10.1093/icb/icad067] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 05/25/2023] [Accepted: 05/29/2023] [Indexed: 06/18/2023] Open
Abstract
Torpor was traditionally seen as a winter survival mechanism employed by animals living in cold and highly seasonal habitats. Although we now know that torpor is also used by tropical and subtropical species, and in response to a variety of triggers, torpor is still largely viewed as a highly controlled, seasonal mechanism shown by Northern hemisphere species. To scrutinize this view, we report data from a macroanalysis in which we characterized the type and seasonality of torpor use from mammal species currently known to use torpor. Our findings suggest that predictable, seasonal torpor patterns reported for Northern temperate and polar species are highly derived forms of torpor expression, whereas the more opportunistic and variable forms of torpor that we see in tropical and subtropical species are likely closer to the patterns expressed by ancestral mammals. Our data emphasize that the torpor patterns observed in the tropics and subtropics should be considered the norm and not the exception.
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Affiliation(s)
- Julia Nowack
- School of Biological and Environmental Sciences, Liverpool John Moores University, L3 3AF Liverpool, UK
| | - Clare Stawski
- School of Science, Technology and Engineering, University of the Sunshine Coast (USC), Maroochydore DC, QLD 4558, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
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Emser SV, Spielvogel CP, Millesi E, Steinborn R. Mitochondrial polymorphism m.3017C>T of SHLP6 relates to heterothermy. Front Physiol 2023; 14:1207620. [PMID: 37675281 PMCID: PMC10478271 DOI: 10.3389/fphys.2023.1207620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/31/2023] [Indexed: 09/08/2023] Open
Abstract
Heterothermic thermoregulation requires intricate regulation of metabolic rate and activation of pro-survival factors. Eliciting these responses and coordinating the necessary energy shifts likely involves retrograde signalling by mitochondrial-derived peptides (MDPs). Members of the group were suggested before to play a role in heterothermic physiology, a key component of hibernation and daily torpor. Here we studied the mitochondrial single-nucleotide polymorphism (SNP) m.3017C>T that resides in the evolutionarily conserved gene MT-SHLP6. The substitution occurring in several mammalian orders causes truncation of SHLP6 peptide size from twenty to nine amino acids. Public mass spectrometric (MS) data of human SHLP6 indicated a canonical size of 20 amino acids, but not the use of alternative translation initiation codons that would expand the peptide. The shorter isoform of SHLP6 was found in heterothermic rodents at higher frequency compared to homeothermic rodents (p < 0.001). In heterothermic mammals it was associated with lower minimal body temperature (T b, p < 0.001). In the thirteen-lined ground squirrel, brown adipose tissue-a key organ required for hibernation, showed dynamic changes of the steady-state transcript level of mt-Shlp6. The level was significantly higher before hibernation and during interbout arousal and lower during torpor and after hibernation. Our finding argues to further explore the mode of action of SHLP6 size isoforms with respect to mammalian thermoregulation and possibly mitochondrial retrograde signalling.
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Affiliation(s)
- Sarah V. Emser
- Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
- Genomics Core Facility, VetCore, University of Veterinary Medicine, Vienna, Austria
| | - Clemens P. Spielvogel
- Department of Biomedical Imaging and Image-Guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
| | - Eva Millesi
- Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
| | - Ralf Steinborn
- Genomics Core Facility, VetCore, University of Veterinary Medicine, Vienna, Austria
- Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
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Giroud S, Ragger MT, Baille A, Hoelzl F, Smith S, Nowack J, Ruf T. Food availability positively affects the survival and somatic maintenance of hibernating garden dormice (Eliomys quercinus). Front Zool 2023; 20:19. [PMID: 37226260 PMCID: PMC10207780 DOI: 10.1186/s12983-023-00498-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/15/2023] [Indexed: 05/26/2023] Open
Abstract
BACKGROUND Torpor is an energy saving strategy achieved by substantial reductions of metabolic rate and body temperature that enables animals to survive periods of low resource availability. During hibernation (multiday torpor), the frequency of periodic rewarming-characterised by high levels of oxidative stress-is associated with shortening of telomeres, a marker of somatic maintenance. OBJECTIVES In this study, we determined the impact of ambient temperature on feeding behaviour and telomere dynamics in hibernating garden dormice (Eliomys quercinus) over winter. This obligate hibernator prepares for hibernation by accumulating fat stores but can also feed during hibernation. METHODOLOGY Food intake, torpor pattern, changes in telomere length, and body mass change were assessed in animals housed at experimentally controlled temperatures of either 14 °C (i.e., a mild winter) or 3 °C (i.e., a cold winter) over 6 months. RESULTS When hibernating at 14 °C, dormice experienced 1.7-fold more frequent and 2.4-fold longer inter-bout euthermia, and spent significantly less time torpid, compared to animals hibernating at 3 °C. Higher food intake enabled individuals to compensate for increased energetic costs when hibernating at milder temperatures (14 °C vs. 3 °C), to buffer body mass loss and thus increase winter survival. Interestingly, we observed a significant increase of telomere length over the entire hibernation period, irrespective of temperature treatment. CONCLUSION We conclude that higher temperatures during winter, if associated with sufficient food availability, can have a positive effect on the individual's energy balance and somatic maintenance. These results suggest that winter food availability might be a crucial determinant for the survival of the garden dormouse in the context of ever-increasing environmental temperatures.
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Affiliation(s)
- Sylvain Giroud
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Savoyenstraße 1, 1160, Vienna, Austria.
| | - Marie-Therese Ragger
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Savoyenstraße 1, 1160, Vienna, Austria
| | - Amélie Baille
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Savoyenstraße 1, 1160, Vienna, Austria
| | - Franz Hoelzl
- Konrad Lorenz Institute of Ethology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Steve Smith
- Konrad Lorenz Institute of Ethology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Julia Nowack
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Savoyenstraße 1, 1160, Vienna, Austria
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Thomas Ruf
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine, Savoyenstraße 1, 1160, Vienna, Austria
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7
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Spangenberg DK, Fuhrman AE, Larsen DA, Beckman BR. A correlation between seasonally changing photoperiod, whole body lipid, and condition factor in juvenile spring Chinook salmon (Oncorhynchus tshawytscha). PLoS One 2023; 18:e0285380. [PMID: 37200396 DOI: 10.1371/journal.pone.0285380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 04/21/2023] [Indexed: 05/20/2023] Open
Abstract
The regulation of lipid stores is a central process for the physiology and ecology of fishes. Seasonal variation in lipid stores has been directly linked to survival of fishes across periods of food deprivation. We assessed whether a seasonally changing photoperiod was correlated to seasonal changes in energetic status to help better understand these important processes. Groups of first feeding Chinook salmon fry were introduced to a seasonal photoperiod cycle, but the point of entrance into the seasonal cycle varied from near the winter solstice (December), to either side of the spring equinox (February & May). Temperature and feeding rate were similar for all treatments. Subsequently, condition factor and whole body lipid content were assessed through a seasonal progression. Throughout most of the experiment, length and weight did not differ between the different photoperiod treatments, however whole body lipid and Fulton's condition factor did. Furthermore, changes in both whole body lipid and Fulton's condition factor in all treatment groups followed a similar seasonal pattern that was inversely related to day length (highest K and lipid levels found during days with the least light). These results suggest that regardless of age or size, there is a correlation between seasonal changes in photoperiod and changes in body composition in juvenile Chinook salmonids.
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Affiliation(s)
- Dina K Spangenberg
- Environmental Fisheries Science Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - Abby E Fuhrman
- Environmental Fisheries Science Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - Donald A Larsen
- Environmental Fisheries Science Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - Brian R Beckman
- Environmental Fisheries Science Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
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Abstract
We address the question of ultimate selective advantages of hibernation. Biologists generally seem to accept the notion that multiday torpor is primarily a response to adverse environmental conditions, namely cold climate and low food abundance. We closely examine hibernation, and its summer equivalent estivation, in the edible dormouse, Glis glis. We conclude that in this species, hibernation is not primarily driven by poor conditions. Dormice enter torpor with fat reserves in years that are unfavourable for reproduction but provide ample food supply for animals to sustain themselves and even gain body energy reserves. While staying in hibernacula below ground, hibernators have much higher chances of survival than during the active season. We think that dormice enter prolonged torpor predominantly to avoid predation, mainly nocturnal owls. Because estivation in summer is immediately followed by hibernation, this strategy requires a good body condition in terms of fat reserves. As dormice age, they encounter fewer occasions to reproduce when calorie-rich seeds are available late in the year, and phase advance the hibernation season. By early emergence from hibernation, the best territories can be occupied and the number of mates maximised. However, this advantage comes at the cost of increased predation pressure that is maximal in spring. We argue the predator avoidance is generally one of the primary reasons for hibernation, as increased perceived predation pressure leads to an enhanced torpor use. The edible dormouse may be just an example where this behaviour becomes most obvious, on the population level and across large areas.
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Tøien Ø, Barnes BM, Ruf T. Do bears hibernate in the woods? Comment on 'Why bears hibernate? Redefining the scaling energetics of hibernation'. Proc Biol Sci 2022; 289:20221396. [PMID: 36476007 PMCID: PMC9554731 DOI: 10.1098/rspb.2022.1396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Øivind Tøien
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Brian M. Barnes
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Thomas Ruf
- Research Institute of Wildlife Ecology, University of Veterinary Medicine, 1210 Vienna, Austria
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Williams CT, Chmura HE, Deal CK, Wilsterman K. Sex-differences in Phenology: A Tinbergian Perspective. Integr Comp Biol 2022; 62:980-997. [PMID: 35587379 DOI: 10.1093/icb/icac035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 04/18/2022] [Accepted: 04/23/2022] [Indexed: 11/13/2022] Open
Abstract
Shifts in the timing of cyclic seasonal life-history events are among the most commonly reported responses to climate change, with differences in response rates among interacting species leading to phenological mismatches. Within a species, however, males and females can also exhibit differential sensitivity to environmental cues and may therefore differ in their responsiveness to climate change, potentially leading to phenological mismatches between the sexes. This occurs because males differ from females in when and how energy is allocated to reproduction, resulting in marked sex-differences in life-history timing across the annual cycle. In this review, we take a Tinbergian perspective and examine sex differences in timing of vertebrates from adaptive, ontogenetic, mechanistic, and phylogenetic viewpoints with the goal of informing and motivating more integrative research on sexually dimorphic phenologies. We argue that sexual and natural selection lead to sex-differences in life-history-timing and that understanding the ecological and evolutionary drivers of these differences is critical for connecting climate-driven phenological shifts to population resilience. Ontogeny may influence how and when sex differences in life-history timing arise because the early-life environment can profoundly affect developmental trajectory, rates of reproductive maturation, and seasonal timing. The molecular mechanisms underlying these organismal traits are relevant to identifying the diversity and genetic basis of population- and species-level responses to climate change, and promisingly, the molecular basis of phenology is becoming increasingly well-understood. However, because most studies focus on a single sex, the causes of sex-differences in phenology critical to population resilience often remain unclear. New sequencing tools and analyses informed by phylogeny may help generate hypotheses about mechanism as well as insight into the general "evolvability" of sex differences across phylogenetic scales, especially as trait and genome resources grow. We recommend that greater attention be placed on determining sex-differences in timing mechanisms and monitoring climate change responses in both sexes, and we discuss how new tools may provide key insights into sex-differences in phenology from all four Tinbergian domains.
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Affiliation(s)
- Cory T Williams
- Department of Biology, Colorado State University, 1878 Campus Delivery Fort Collins, CO 80523, USA
| | - Helen E Chmura
- Institute of Arctic Biology, University of Alaska Fairbanks, 2140 Koyukuk Drive, Fairbanks, AK 99775, USA.,Rocky Mountain Research Station, United States Forest Service, 800 E. Beckwith Ave, Missoula, MT 59801, USA
| | - Cole K Deal
- Department of Biology, Colorado State University, 1878 Campus Delivery Fort Collins, CO 80523, USA
| | - Kathryn Wilsterman
- Department of Biology, Colorado State University, 1878 Campus Delivery Fort Collins, CO 80523, USA
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Mikes M, Rice SA, Bibus D, Kitaysky A, Drew KL. Translating PUFA omega 6:3 ratios from wild to captive hibernators (Urocitellus parryii) enhances sex-dependent mass-gain without increasing physiological stress indicators. J Comp Physiol B 2022; 192:529-540. [PMID: 35503574 PMCID: PMC9197884 DOI: 10.1007/s00360-022-01437-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/20/2022] [Accepted: 03/30/2022] [Indexed: 11/28/2022]
Abstract
Omega 3 polyunsaturated fatty acids (PUFAs) are well-documented for their influence on health and weight loss. Recent studies indicate omega 3 PUFAs may exert a negative impact on cellular stress and physiology in some hibernators. We asked if physiological stress indicators, lipid peroxidation and mass gain in Arctic Ground Squirrels (AGS) were negatively influenced by naturally occurring dietary omega 3 PUFA levels compared to omega 3 PUFA levels found in common laboratory diets. We found plasma fatty acid profiles of free-ranging AGS to be high in omega 3 PUFAs with balanced omega 6:3 ratios, while standard laboratory diets and plasma of captive AGS are high in omega 6 and low in omega 3 PUFAs with higher omega 6:3 ratios. Subsequently, we designed a diet to mimick free-range AGS omega 6:3 ratios in captive AGS. Groups of wild-caught juvenile AGS were either fed: (1) Mazuri Rodent Chow (Standard Rodent chow, 4.95 omega 6:3 ratio), or (2) balanced omega 6:3 chow (Balanced Diet, 1.38 omega 6:3). AGS fed the Balanced Diet had plasma omega 6:3 ratios that mimicked plasma profiles of wild AGS. Balanced Diet increased female body mass before hibernation, but did not influence levels of cortisol in plasma or levels of the lipid peroxidation product 4-HNE in brown adipose tissue. Overall, as the mass gain is critical during pre-hibernation for obligate hibernators, the results show that mimicking a fatty acid profile of wild AGS facilitates sex-dependent mass accumulation without increasing stress indicators.
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Affiliation(s)
- Monica Mikes
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.,Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Sarah A Rice
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, USA. .,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.
| | - Doug Bibus
- Lipid Technologies, LLC, Austin, MN, USA
| | - Alexander Kitaysky
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.,Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA
| | - Kelly L Drew
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, USA.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA
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12
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Genoud M. The seasonal variation of basal metabolic rate is related to the expression of torpor among small mammals. J Therm Biol 2022; 104:103197. [DOI: 10.1016/j.jtherbio.2022.103197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 01/18/2022] [Accepted: 01/21/2022] [Indexed: 10/19/2022]
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13
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Siutz C, Ruf T, Monecke S, Millesi E. Morphometric parameters predict body fat proportions in common hamsters. J Mammal 2021; 103:471-480. [PMID: 35418810 PMCID: PMC8996034 DOI: 10.1093/jmammal/gyab137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 10/02/2021] [Indexed: 12/01/2022] Open
Abstract
Common hamsters (Cricetus cricetus) are hibernators that rely both on body fat reserves and food stores for the winter period. They face an ongoing population decline in most parts of their distribution and recently were classified as critically endangered. Knowledge on individual body fat proportions in this species is of particular interest for conservation, because it could contribute to better understand the high plasticity in overwintering strategies, overwinter mortality rates, individual variations in reproductive output, and give information on the animals’ health state. To calculate body fat proportions, we validated a method that can be applied in the field without the use of anesthesia. To develop this method, we first analyzed the body fat in carcasses of common hamsters using Soxhlet extractions and measured four morphometric parameters (body mass, head length, tibia length, foot length). The morphometric measurements were then integrated in a linear regression model to predict body fat proportions based on the measured values. The morphometric variables yielded an explained variance (adjusted R2) of 96.42% and body fat proportions were predicted with a mean absolute error of 1.27 ± 0.11% from measured values. We applied the model to predict body fat for available field data, which consistently produced reliable values. By measuring the four morphometric parameters and following the provided instructions, body fat proportions can be reliably and noninvasively estimated in captive or free-ranging common hamsters. Furthermore, the method could be applicable to other rodents after species-specific validation.
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Affiliation(s)
- Carina Siutz
- Department of Behavioral and Cognitive Biology, Faculty of Life Sciences, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
| | - Thomas Ruf
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Savoyenstraße 1, 1160 Vienna, Austria
| | - Stefanie Monecke
- Institut des Neurosciences Cellulaires et Intégratives (INCI), Neurobiologie des Rythmes, CNRS UPR-3212, Université de Strasbourg, 8 allée du général Rouvillois, 67000 Strasbourg, France
- Institute of Medical Psychology, Medical Faculty, Ludwig-Maximilians-University Munich, Goethestrasse 31/ I, 80336 Munich, Germany
| | - Eva Millesi
- Department of Behavioral and Cognitive Biology, Faculty of Life Sciences, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
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Landscape drivers of site occupancy by remnant populations of arctic ground squirrels (Urocitellus parryii). EUR J WILDLIFE RES 2021. [DOI: 10.1007/s10344-021-01534-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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15
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Frare C, Williams CT, Drew KL. Thermoregulation in hibernating mammals: The role of the "thyroid hormones system". Mol Cell Endocrinol 2021; 519:111054. [PMID: 33035626 PMCID: PMC8091518 DOI: 10.1016/j.mce.2020.111054] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 07/15/2020] [Accepted: 10/04/2020] [Indexed: 12/19/2022]
Abstract
Hibernation is a unique evolutionary adaptation to conserve energy. During the pre-hibernation (i.e. fall) season, a progressive decline in core body temperature and further decrease in metabolism underlie a seasonal modulation in thermoregulation. The onset of hibernation requires marked changes in thermoregulatory attributes including adjustment in body temperature and tissue specific increases in thermogenic capacity. The hibernation season is characterized by a regulated suppression in thermogenesis allowing the onset of torpor interrupted by periodic activation of thermogenesis to sustain interbout arousals. Thyroid hormones are known to regulate both body temperature and metabolism, and for this reason, the hypothalamic-pituitary-thyroid axis and thyroid hormones have been investigated as modulators of thermogenesis in the phenomenon of hibernation, but the mechanisms remain poorly understood. In this review, we present an overview of what is known about the thermogenic roles of thyroid hormones in hibernating species across seasons and within the hibernating season (torpor-interbout arousal cycle). Overall, the hypothalamic-pituitary-thyroid axis and thyroid hormones play a role in the pre-hibernation season to enhance thermogenic capacity. During hibernation, thermogenesis is attenuated at the level of sympathetic premotor neurons within the raphe pallidus and by deiodinase expression in the hypothalamus. Further, as recent work highlights the direct effect of thyroid hormones within the central nervous system in activating thermogenesis, we speculate how similar mechanisms may occur in hibernating species to modulate thermogenesis across seasons and to sustain interbout arousals. However, further experiments are needed to elucidate the role of thyroid hormones in hibernation, moving towards the understanding that thyroid hormones metabolism, transport and availability within tissues may be the most telling indicator of thyroid status.
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Affiliation(s)
- C Frare
- Department of Chemistry and Biochemistry University of Alaska Fairbanks, Fairbanks, AK, 99775, USA; Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Cory T Williams
- Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA; Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Kelly L Drew
- Department of Chemistry and Biochemistry University of Alaska Fairbanks, Fairbanks, AK, 99775, USA; Institute of Arctic Biology, Center for Transformative Research in Metabolism, University of Alaska Fairbanks 2140 Koyukuk Drive, Fairbanks, AK, 99775, USA.
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Watts AJ, Logan SM, Kübber-Heiss A, Posautz A, Stalder G, Painer J, Gasch K, Giroud S, Storey KB. Regulation of Peroxisome Proliferator-Activated Receptor Pathway During Torpor in the Garden Dormouse, Eliomys quercinus. Front Physiol 2020; 11:615025. [PMID: 33408645 PMCID: PMC7779809 DOI: 10.3389/fphys.2020.615025] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/03/2020] [Indexed: 11/16/2022] Open
Abstract
Differential levels of n-6 and n-3 essential polyunsaturated fatty acids (PUFAs) are incorporated into the hibernator’s diet in the fall season preceding prolonged, multi-days bouts of torpor, known as hibernation. Peroxisome proliferator-activated receptor (PPAR) transcriptional activators bind lipids and regulate genes involved in fatty acid transport, beta-oxidation, ketogenesis, and insulin sensitivity; essential processes for survival during torpor. Thus, the DNA-binding activity of PPARα, PPARδ, PPARγ, as well as the levels of PPARγ coactivator 1α (PGC-1α) and L-fatty acid binding protein (L-FABP) were investigated in the hibernating garden dormouse (Eliomys quercinus). We found that dormice were hibernating in a similar way regardless of the n-6/n-3 PUFA diets fed to the animals during the fattening phase prior to hibernation. Further, metabolic rates and body mass loss during hibernation did not differ between dietary groups, despite marked differences in fatty acid profiles observed in white adipose tissue prior and at mid-hibernation. Overall, maintenance of PPAR DNA-binding activity was observed during torpor, and across three n-6/n-3 ratios, suggesting alternate mechanisms for the prioritization of lipid catabolism during torpor. Additionally, while no change was seen in L-FABP, significantly altered levels of PGC-1α were observed within the white adipose tissue and likely contributes to enhanced lipid metabolism when the diet favors n-6 PUFAs, i.e., high n-6/n-3 ratio, in both the torpid and euthermic state. Altogether, the maintenance of lipid metabolism during torpor makes it likely that consistent activity or levels of the investigated proteins are in aid of this metabolic profile.
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Affiliation(s)
| | | | - Anna Kübber-Heiss
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Annika Posautz
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Gabrielle Stalder
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Johanna Painer
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Kristina Gasch
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Sylvain Giroud
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
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18
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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: 39] [Impact Index Per Article: 9.8] [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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19
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Zhang VY, Williams CT, Palme R, Buck CL. Glucocorticoids and activity in free-living arctic ground squirrels: Interrelationships between weather, body condition, and reproduction. Horm Behav 2020; 125:104818. [PMID: 32698015 DOI: 10.1016/j.yhbeh.2020.104818] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/25/2020] [Accepted: 07/10/2020] [Indexed: 01/13/2023]
Abstract
The dynamic relationship between glucocorticoids and behavior are not well understood in wild mammals. We investigated how weather, body condition, and reproduction interact to affect cortisol levels and activity patterns in a free-living population of arctic ground squirrels (Urocitellus parryii). As a proxy for foraging and escape behaviors, collar-mounted accelerometers and light loggers were used to measure above-ground activity levels and the amount of time squirrels spent below the surface, respectively. Fecal cortisol metabolites (FCMs) were quantified to assess glucocorticoid secretion in squirrels. Male and female squirrels differed in above-ground activity levels and time spent below-ground across the active season, with males being most active during mating and females most active during lactation. We also found that female, but not male, squirrels exhibited seasonal variation in FCM levels, with concentrations highest during mid-lactation and lowest after the lactation period. In female squirrels, the seasonal relationships between breeding stage, activity, and FCM levels were also consistent with changes in maternal investment and the preparative role that glucocorticoids are hypothesized to play in energy mobilization. Body condition was not associated with FCM levels in squirrels. As predicted, deteriorating weather also influenced FCM levels and activity patterns in squirrels. FCM concentrations were affected by an interaction between temperature and wind speed when seasonal temperatures were lowest. In addition, above-ground activity, but not time spent below-ground, positively correlated with FCM levels. These results suggest that, although ground squirrels avoid inclement weather by remaining below-ground, activation of the stress axis may stimulate foraging activity.
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Affiliation(s)
- Victor Y Zhang
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Cory T Williams
- Institute of Arctic Biology and Department of Biology & Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Rupert Palme
- Department of Biomedical Sciences, University of Veterinary Medicine, A-1210 Vienna, Austria
| | - C Loren Buck
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
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20
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A Unique Energy-Saving Strategy during Hibernation Revealed by Multi-Omics Analysis in the Chinese Alligator. iScience 2020; 23:101202. [PMID: 32534442 PMCID: PMC7298530 DOI: 10.1016/j.isci.2020.101202] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/16/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022] Open
Abstract
Many ectotherms hibernate in face of the harsh winter conditions to improve their survival rate. However, the molecular mechanism underlying this process remains unclear. Here, we explored the hibernation mechanism of Chinese alligator using integrative multi-omics analysis. We revealed that (1) the thyroid hormone biosynthesis, nutrition absorption and metabolism, muscle contraction, urinary excretion and immunity function pathways are overall downregulated during hibernation; (2) the fat catabolism is completely suppressed, contrasting with the upregulation of hepatic fatty-acid-transporter CPT1A, suggesting a unique energy-saving strategy that differs from that in hibernating mammals; (3) the hibernation-related genes are not only directly regulated by DNA methylation but also controlled by methylation-dependent transcription networks. In addition, we identified and compared tissue-specific, species-specific, and conserved season-biased miRNAs, demonstrating complex post-transcriptional regulation during hibernation. Our study revealed the genetic and epigenetic mechanisms underlying hibernation in the Chinese alligator and provided molecular insights into the evolution of hibernation regulation.
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21
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Nowack J, Levesque DL, Reher S, Dausmann KH. Variable Climates Lead to Varying Phenotypes: “Weird” Mammalian Torpor and Lessons From Non-Holarctic Species. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00060] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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22
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Ryan CC, Burns LE, Broders HG. Changes in underground roosting patterns to optimize energy conservation in hibernating bats. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0340] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Non-migratory bats in colder climates use hibernation to survive winter. By reducing metabolic rate (i.e., using torpor), bats can survive winter on stored fat reserves. During hibernation, bats arouse from torpor and may move within the hibernaculum, a process called “internal migration”. We hypothesized that internal migration occurs to optimize hibernation energetics in that bats move to select a microclimate to minimize energy expenditure both by seeking cooler areas of the hibernacula and avoiding those with large temperature fluctuations. Early in the winter, we observed that 62% of bats were roosting in the warmer, less energy efficient, deepest 50% of an abandoned mine hibernaculum. Late in the season, there was a shift towards the cooler entrance area, thereby decreasing energy demands during the torpid period, with 78% of bats in the mine roosting within 50 m of the entrance. Although there was no significant effect of hibernation period (i.e., early vs. late winter) on the number of bats in huddles, the largest huddles occurred close to the entrance in late winter. To fully understand and manage bat populations, it is important to understand that hibernation is a dynamic process with bats moving and interacting with one another throughout the season.
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Affiliation(s)
- Caleb C. Ryan
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Lynne E. Burns
- Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada
| | - Hugh G. Broders
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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23
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Wang X, Watt CF, Sinclair KJ, McKenzie CA, Staples JF, MacCannell ADV. Thermoneutral temperature reduces liver volume but increases fat content in a mammalian hibernator. J Therm Biol 2019; 83:172-177. [PMID: 31331516 DOI: 10.1016/j.jtherbio.2019.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 05/04/2019] [Accepted: 05/19/2019] [Indexed: 11/25/2022]
Abstract
Hibernators survive challenging winters by entering torpor, which lowers body temperature (Tb) to ∼5 °C for 12-14 days, followed by spontaneous arousals where Tb increases to ∼37 °C for 10-12 h before entering another torpor bout. This Tb cycle is accompanied by significant fluctuations in metabolic rate. Little is known about the role of the liver in lipid metabolism during hibernation. In this study we measured the effect of ambient temperature on liver volume and lipid content in 13-lined ground squirrels (Ictidomys tridecemlineatus). We housed animals at thermoneutral (25 °C) or cold (5 °C) ambient temperatures, with the same photoperiod (12 h light:12 h dark) for an entire year. We determined volume and water-fat ratio of the liver using magnetic resonance imaging (MRI). Ambient temperature significantly affected both liver volume and fat content. From October to August squirrels housed at 25 °C had 25% smaller livers compared to the squirrels housed at 5 °C, but their average lipid content (13.3%) was 37% higher. Because the squirrels housed at 25 °C appeared to continue feeding throughout the winter but did not enter extended torpor, more carbohydrates may have been diverted to lipid stores. By contrast, animals housed at 5 °C did not appear to feed, and carbohydrates would likely be preferentially stored in the liver as glycogen to supply glucose for brain metabolism. These results suggest that the fat burden caused by hibernators preparing for winter can lead to symptoms of metabolic syndrome, but that these symptoms are reversible in the spring.
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Affiliation(s)
- Xingyi Wang
- Dept. of Biology, University of Western Ontario, London ON, N6A5B8, Canada; Dept. of Medical Biophysics, University of Western Ontario, London ON, N6A5B7, Canada
| | - Christine F Watt
- Dept. of Biology, University of Western Ontario, London ON, N6A5B8, Canada
| | - Kevin J Sinclair
- Dept. of Medical Biophysics, University of Western Ontario, London ON, N6A5B7, Canada
| | - Charles A McKenzie
- Dept. of Medical Biophysics, University of Western Ontario, London ON, N6A5B7, Canada
| | - James F Staples
- Dept. of Biology, University of Western Ontario, London ON, N6A5B8, Canada
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24
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Chayama Y, Ando L, Sato Y, Shigenobu S, Anegawa D, Fujimoto T, Taii H, Tamura Y, Miura M, Yamaguchi Y. Molecular Basis of White Adipose Tissue Remodeling That Precedes and Coincides With Hibernation in the Syrian Hamster, a Food-Storing Hibernator. Front Physiol 2019; 9:1973. [PMID: 30745884 PMCID: PMC6360343 DOI: 10.3389/fphys.2018.01973] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 12/31/2018] [Indexed: 12/31/2022] Open
Abstract
Mammalian hibernators store fat extensively in white adipose tissues (WATs) during pre-hibernation period (Pre-HIB) to prepare for hibernation. However, the molecular mechanisms underlying the pre-hibernation remodeling of WAT have not been fully elucidated. Syrian hamsters, a food-storing hibernator, can hibernate when exposed to a winter-like short day photoperiod and cold ambient temperature (SD-Cold). Animals subjected to prolonged SD-Cold had smaller white adipocytes and beige-like cells within subcutaneous inguinal WAT (iWAT). Time-course analysis of gene expression with RNA-sequencing and quantitative PCR demonstrated that the mRNA expression of not only genes involved in lipid catabolism (lipolysis and beta-oxidation) but also lipid anabolism (lipogenesis and lipid desaturation) was simultaneously up-regulated prior to hibernation onset in the animals. The enhanced capacity of both lipid catabolism and lipid anabolism during hibernation period (HIB) is striking contrast to previous observations in fat-storing hibernators that only enhance catabolism during HIB. The mRNA expression of mTORC1 and PPAR signaling molecules increased, and pharmacological activation of PPARs indeed up-regulated lipid metabolism genes in iWAT explants from Syrian hamsters. These results suggest that the Syrian hamster rewires lipid metabolisms while preparing for hibernation to effectively utilize body fat and synthesize it from food intake during HIB.
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Affiliation(s)
- Yuichi Chayama
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Lisa Ando
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuya Sato
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Shuji Shigenobu
- Functional Genomics Facility, National Institute for Basic Biology, Okazaki, Japan
| | - Daisuke Anegawa
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Takayuki Fujimoto
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Hiroki Taii
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Yutaka Tamura
- Department of Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Japan
| | - Masayuki Miura
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Yoshifumi Yamaguchi
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.,Hibernation Metabolism, Physiology and Development Group, Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
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Frare C, Jenkins ME, Soldin SJ, Drew KL. The Raphe Pallidus and the Hypothalamic-Pituitary-Thyroid Axis Gate Seasonal Changes in Thermoregulation in the Hibernating Arctic Ground Squirrel ( Urocitellus parryii). Front Physiol 2018; 9:1747. [PMID: 30618783 PMCID: PMC6299024 DOI: 10.3389/fphys.2018.01747] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/20/2018] [Indexed: 01/17/2023] Open
Abstract
Thermoregulation is necessary to maintain energy homeostasis. The novel discovery of brown adipose tissue (BAT) in humans has increased research interests in better understanding BAT thermogenesis to restore energy balance in metabolic disorders. The hibernating Arctic ground squirrel (AGS) offers a novel approach to investigate BAT thermogenesis. AGS seasonally increase their BAT mass to increase the ability to generate heat during interbout arousals. The mechanisms promoting the seasonal changes in BAT thermogenesis are not well understood. BAT thermogenesis is regulated by the raphe pallidus (rPA) and by thyroid hormones produced by the hypothalamic–pituitary–thyroid (HPT) axis. Here, we investigate if the HPT axis and the rPA undergo seasonal changes to modulate BAT thermogenesis in hibernation. We used histological analysis and tandem mass spectrometry to assess activation of the HPT axis and immunohistochemistry to measure neuronal activation. We found an increase in HPT axis activation in fall and in response to pharmacologically induced torpor when adenosine A1 receptor agonist was administered in winter. By contrast, the rPA neuronal activation was lower in winter in response to pharmacologically induced torpor. Activation of the rPA was also lower in winter compared to the other seasons. Our results suggest that thermogenic capacity develops during fall as the HPT axis is activated to reach maximum capacity in winter seen by increased free thyroid hormones in response to cooling. However, thermogenesis is inhibited during torpor as sympathetic premotor neuronal activation is lower in winter, until arousal when inhibition of thermogenesis is relieved. These findings describe seasonal modulation of thermoregulation that conserves energy through attenuated sympathetic drive, but retains heat generating capacity through activation of the HPT axis.
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Affiliation(s)
- Carla Frare
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Mackenzie E Jenkins
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Steven J Soldin
- National Institutes of Health Clinical Center, Bethesda, MD, United States.,Division of Endocrinology and Metabolism, Department of Medicine, Georgetown University, Washington, DC, United States
| | - Kelly L Drew
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, United States
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26
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Siutz C, Valent M, Ammann V, Niebauer A, Millesi E. Sex-specific effects of food supplementation on hibernation performance and reproductive timing in free-ranging common hamsters. Sci Rep 2018; 8:13082. [PMID: 30166598 PMCID: PMC6117252 DOI: 10.1038/s41598-018-31520-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 08/20/2018] [Indexed: 02/03/2023] Open
Abstract
Hibernation is characterized by reduced metabolism and body temperature during torpor bouts. Energy reserves available during winter play an important role for hibernation and some species respond to high energy reserves with reduced torpor expression. Common hamsters are food-storing hibernators and females hibernate for shorter periods than males, probably related to larger food stores. In this study, we provided free-ranging common hamsters with sunflower seeds shortly before winter and recorded body temperature using subcutaneously implanted data loggers. We compared hibernation patterns and body mass changes between individuals with and without food supplements and analysed reproductive onset in females. Supplemented males delayed hibernation onset, hibernated for much shorter periods, and emerged in spring with higher body mass than unsupplemented ones. Additional food did not affect hibernation performance in females, but supplemented females emerged earlier and preceded those without food supplements in reproductive onset. Thus, males and females differently responded to food supplementation: access to energy-rich food stores enabled males to shorten the hibernation period and emerge in better body condition, probably enhancing mating opportunities and reproductive success. Females did not alter hibernation patterns, but started to reproduce earlier than unsupplemented individuals, enabling reproductive benefits by an extended breeding period.
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Affiliation(s)
- Carina Siutz
- Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
| | - Margit Valent
- Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Viktoria Ammann
- Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Ariane Niebauer
- Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Eva Millesi
- Department of Behavioural Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
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27
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Logan SM, Storey KB. Pro-inflammatory AGE-RAGE signaling is activated during arousal from hibernation in ground squirrel adipose. PeerJ 2018; 6:e4911. [PMID: 29888131 PMCID: PMC5991297 DOI: 10.7717/peerj.4911] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/15/2018] [Indexed: 12/26/2022] Open
Abstract
Background Inflammation is generally suppressed during hibernation, but select tissues (e.g. lung) have been shown to activate both antioxidant and pro-inflammatory pathways, particularly during arousal from torpor when breathing rates increase and oxidative metabolism fueling the rewarming process produces more reactive oxygen species. Brown and white adipose tissues are now understood to be major hubs for the regulation of immune and inflammatory responses, yet how these potentially damaging processes are regulated by fat tissues during hibernation has hardly been studied. The advanced glycation end-product receptor (RAGE) can induce pro-inflammatory responses when bound by AGEs (which are glycated and oxidized proteins, lipids, or nucleic acids) or damage associated molecular pattern molecules (DAMPs, which are released from dying cells). Methods Since gene expression and protein synthesis are largely suppressed during torpor, increases in AGE-RAGE pathway proteins relative to a euthermic control could suggest some role for these pro-inflammatory mediators during hibernation. This study determined how the pro-inflammatory AGE-RAGE signaling pathway is regulated at six major time points of the torpor-arousal cycle in brown and white adipose from a model hibernator, Ictidomys tridecemlineatus. Immunoblotting, RT-qPCR, and a competitive ELISA were used to assess the relative gene expression and protein levels of key regulators of the AGE-RAGE pathway during a hibernation bout. Results The results of this study revealed that RAGE is upregulated as animals arouse from torpor in both types of fat, but AGE and DAMP levels either remain unchanged or decrease. Downstream of the AGE-RAGE cascade, nfat5 was more highly expressed during arousal in brown adipose. Discussion An increase in RAGE protein levels and elevated mRNA levels of the downstream transcription factor nfat5 during arousal suggest the pro-inflammatory response is upregulated in adipose tissue of the hibernating ground squirrel. It is unlikely that this cascade is activated by AGEs or DAMPs. This research sheds light on how a fat-but-fit organism with highly regulated metabolism may control the pro-inflammatory AGE-RAGE pathway, a signaling cascade that is often dysregulated in other obese organisms.
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Affiliation(s)
- Samantha M Logan
- Institute of Biochemistry, Departments of Biology and Chemistry, Carleton University, Ottawa, Ontario, Canada
| | - Kenneth B Storey
- Institute of Biochemistry, Departments of Biology and Chemistry, Carleton University, Ottawa, Ontario, Canada
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28
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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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29
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Abstract
Dormice born late in the year start to prepare for winter sooner than mice born earlier in the year.
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Affiliation(s)
- C Loren Buck
- Center for Bioengineering InnovationNorthern Arizona UniversityFlagstaffUnited States
- Department of Biological SciencesNorthern Arizona UniversityFlagstaffUnited States
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30
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Qasim A, Turcotte M, de Souza RJ, Samaan MC, Champredon D, Dushoff J, Speakman JR, Meyre D. On the origin of obesity: identifying the biological, environmental and cultural drivers of genetic risk among human populations. Obes Rev 2018; 19:121-149. [PMID: 29144594 DOI: 10.1111/obr.12625] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/28/2017] [Accepted: 09/08/2017] [Indexed: 12/12/2022]
Abstract
Genetic predisposition to obesity presents a paradox: how do genetic variants with a detrimental impact on human health persist through evolutionary time? Numerous hypotheses, such as the thrifty genotype hypothesis, attempt to explain this phenomenon yet fail to provide a justification for the modern obesity epidemic. In this critical review, we appraise existing theories explaining the evolutionary origins of obesity and explore novel biological and sociocultural agents of evolutionary change to help explain the modern-day distribution of obesity-predisposing variants. Genetic drift, acting as a form of 'blind justice,' may randomly affect allele frequencies across generations while gene pleiotropy and adaptations to diverse environments may explain the rise and subsequent selection of obesity risk alleles. As an adaptive response, epigenetic regulation of gene expression may impact the manifestation of genetic predisposition to obesity. Finally, exposure to malnutrition and disease epidemics in the wake of oppressive social systems, culturally mediated notions of attractiveness and desirability, and diverse mating systems may play a role in shaping the human genome. As an important first step towards the identification of important drivers of obesity gene evolution, this review may inform empirical research focused on testing evolutionary theories by way of population genetics and mathematical modelling.
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Affiliation(s)
- A Qasim
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada
| | - M Turcotte
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada
| | - R J de Souza
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada
| | - M C Samaan
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada.,Department of Pediatrics, McMaster University, Hamilton, ON, Canada.,Division of Pediatric Endocrinology, McMaster Children's Hospital, Hamilton, ON, Canada
| | - D Champredon
- Department of Biology, McMaster University, Hamilton, ON, Canada.,Agent-Based Modelling Laboratory, York University, Toronto, ON, Canada
| | - J Dushoff
- Department of Biology, McMaster University, Hamilton, ON, Canada
| | - J R Speakman
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK.,State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - D Meyre
- Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
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31
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Flexibility is the key: metabolic and thermoregulatory behaviour in a small endotherm. J Comp Physiol B 2018; 188:553-563. [DOI: 10.1007/s00360-017-1140-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 11/30/2017] [Accepted: 12/12/2017] [Indexed: 10/18/2022]
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32
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MacCannell ADV, Sinclair KJ, McKenzie CA, Staples JF. Environmental temperature effects on adipose tissue growth in a hibernator. J Exp Biol 2018; 222:jeb.194548. [DOI: 10.1242/jeb.194548] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 12/12/2018] [Indexed: 12/21/2022]
Abstract
Obligate hibernators express circannual patterns of body mass and hibernation, which persist under constant laboratory conditions. Brown Adipose Tissue (BAT) is important for thermogenesis during arousals from hibernation, whereas White Adipose Tissue (WAT) serves as energy storage and thermal insulation. The goal of this study was to investigate the effects of environmental temperature on BAT and WAT. We hypothesized that changes to environmental temperature would not influence the pattern of mass gain or BAT and WAT volume in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus). To test this, we housed animals thermoneutral 25°C (warm-housed) or 5°C (cold-housed), with the same photoperiod (12 h light:12 h dark) over an entire year. Throughout the year we measured the volume and water-fat ratio of WAT and BAT using magnetic resonance imaging (MRI). We found no evidence of torpor in the warm-housed animals, indicating that this species might not be an obligate hibernator, as previously assumed. Regardless of ambient temperature BAT volume increased prior to winter, then decreased in late winter with no change in water-fat ratio. By contrast both body mass and WAT volume of cold-housed animals declined throughout the winter and recovered after hibernation, but thermoneutral housing produced no circannual pattern in body mass, even though WAT volume declined in late winter. Cold exposure appears to be a primary regulator for WAT but BAT may exhibit an endogenous circannual rhythm in terms of depot volume.
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Affiliation(s)
- Amanda D. V. MacCannell
- Dept. of Biology, University of Western Ontario, London ON, N6A5B8, Canada
- Current address: Discovery and Translational Science Dept., University of Leeds, Leeds, LS29JT, UK
| | - Kevin J. Sinclair
- Dept. of Medical Biophysics, University of Western Ontario, London ON, N6A5B7, Canada
| | - Charles A. McKenzie
- Dept. of Medical Biophysics, University of Western Ontario, London ON, N6A5B7, Canada
| | - James F. Staples
- Dept. of Biology, University of Western Ontario, London ON, N6A5B8, Canada
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33
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Richardson CS, Heeren T, Kunz TH. Seasonal and Sexual Variation in Metabolism, Thermoregulation, and Hormones in the Big Brown Bat (Eptesicus fuscus). Physiol Biochem Zool 2018; 91:705-715. [DOI: 10.1086/695424] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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34
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Siutz C, Nemeth M, Wagner KH, Quint R, Ruf T, Millesi E. Effects of food store quality on hibernation performance in common hamsters. PLoS One 2017; 12:e0185913. [PMID: 29045417 PMCID: PMC5646777 DOI: 10.1371/journal.pone.0185913] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 09/21/2017] [Indexed: 11/18/2022] Open
Abstract
Hibernating animals can adjust torpor expression according to available energy reserves. Besides the quantity, the quality of energy reserves could play an important role for overwintering strategies. Common hamsters are food-storing hibernators and show high individual variation in hibernation performance, which might be related to the quality of food hoards in the hibernacula. In this study, we tested the effects of food stores high in fat content, particularly polyunsaturated fatty acids (PUFAs), on hibernation patterns under laboratory conditions. Control animals received standard rodent pellets only, while in the other group pellets were supplemented with sunflower seeds. We recorded body temperature during winter using subcutaneously implanted data loggers, documented total food consumption during winter, and analysed PUFA proportions in white adipose tissue (WAT) before and after the winter period. About half of the individuals in both groups hibernated and torpor expression did not differ between these animals. Among the high-fat group, however, individuals with high sunflower seeds intake strongly reduced the time spent in deep torpor. PUFA proportions in WAT decreased during winter in both groups and this decline was positively related to the time an individual spent in deep torpor. Sunflower seeds intake dampened the PUFA decline resulting in higher PUFA levels in animals of the high-fat group after winter. In conclusion, our results showed that common hamsters adjusted torpor expression and food intake in relation to the total energy of food reserves, underlining the importance of food hoard quality on hibernation performance.
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Affiliation(s)
- Carina Siutz
- Department of Behavioural Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
- * E-mail:
| | - Matthias Nemeth
- Department of Behavioural Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Karl-Heinz Wagner
- Department of Nutritional Sciences, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Ruth Quint
- Department of Nutritional Sciences, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Thomas Ruf
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Eva Millesi
- Department of Behavioural Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
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35
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Genoud M, Isler K, Martin RD. Comparative analyses of basal rate of metabolism in mammals: data selection does matter. Biol Rev Camb Philos Soc 2017; 93:404-438. [PMID: 28752629 DOI: 10.1111/brv.12350] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 05/29/2017] [Accepted: 06/05/2017] [Indexed: 12/21/2022]
Abstract
Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non-reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a 'subsampling procedure' was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less-reliable estimates of BMR were generally about 12-20% larger than more-reliable ones. Larger effects were found with more-limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more-limited, order-level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non-linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes.
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Affiliation(s)
- Michel Genoud
- Department of Ecology and Evolution, University of Lausanne, CH-1015, Lausanne, Switzerland.,Division of Conservation Biology, Institute of Ecology and Evolution, Department of Biology, University of Bern, CH-3012, Bern, Switzerland
| | - Karin Isler
- Department of Anthropology, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
| | - Robert D Martin
- Integrative Research Center, The Field Museum, Chicago, IL, 60605-2496, U.S.A.,Institute of Evolutionary Medicine, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
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36
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Bhowmick S, Moore JT, Kirschner DL, Drew KL. Arctic ground squirrel hippocampus tolerates oxygen glucose deprivation independent of hibernation season even when not hibernating and after ATP depletion, acidosis, and glutamate efflux. J Neurochem 2017; 142:160-170. [PMID: 28222226 DOI: 10.1111/jnc.13996] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 01/16/2017] [Accepted: 02/08/2017] [Indexed: 12/20/2022]
Abstract
Cerebral ischemia/reperfusion (I/R) triggers a cascade of uncontrolled cellular processes that perturb cell homeostasis. The arctic ground squirrel (AGS), a seasonal hibernator resists brain damage following cerebral I/R caused by cardiac arrest and resuscitation. However, it remains unclear if tolerance to I/R injury in AGS depends on the hibernation season. Moreover, it is also not clear if events such as depletion of ATP, acidosis, and glutamate efflux that are associated with anoxic depolarization are attenuated in AGS. Here, we employ a novel microperfusion technique to test the hypothesis that tolerance to I/R injury modeled in an acute hippocampal slice preparation in AGS is independent of the hibernation season and persists even after glutamate efflux. Acute hippocampal slices were harvested from summer euthermic AGS, hibernating AGS, and interbout euthermic AGS. Slices were subjected to oxygen glucose deprivation (OGD), an in vitro model of I/R injury to determine cell death marked by lactate dehydrogenase (LDH) release. ATP was assayed using ENLITEN ATP assay. Glutamate and aspartate efflux was measured using capillary electrophoresis. For acidosis, slices were subjected to pH 6.4 or ischemic shift solution (ISS). Acute hippocampal slices from rats were used as a positive control, susceptible to I/R injury. Our results indicate that when tissue temperature is maintained at 36°C, hibernation season has no influence on OGD-induced cell death in AGS hippocampal slices. Our data also show that tolerance to OGD in AGS hippocampal slices occurs despite loss of ATP and glutamate release, and persists during conditions that mimic acidosis and ionic shifts, characteristic of cerebral I/R. Read the Editorial Comment for this article on page 10.
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Affiliation(s)
- Saurav Bhowmick
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Jeanette T Moore
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Daniel L Kirschner
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Kelly L Drew
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, USA
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37
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Torpor patterns in common hamsters with and without access to food stores. J Comp Physiol B 2017; 187:881-888. [PMID: 28417150 PMCID: PMC5486536 DOI: 10.1007/s00360-017-1093-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 03/14/2017] [Accepted: 04/06/2017] [Indexed: 01/15/2023]
Abstract
Hibernating species significantly reduce energy expenditure during winter by entering torpor. Nevertheless, the various benefits of hibernation might be counteracted by negative effects of torpor such as immune depression, oxidative stress, or neuronal impairment. Considering these trade-offs, adequate energy reserves could allow animals to reduce the time spent in torpor or the extent of metabolic depression. Common hamsters use food stores during hibernation and previously documented high individual variations in body temperature patterns during winter could, therefore, be related to differences in external energy reserves. In this study, we manipulated the availability of food stores under laboratory conditions to investigate potential effects on hibernation patterns. Female hamsters were kept in artificial burrows in climate chambers and subcutaneous temperature was recorded using implanted data loggers. One group had access to large food stores, whereas another group received daily food portions which were removed on the next day if not consumed. Almost all hamsters without access to food stores hibernated, while less than half of the individuals with food stores entered deep torpor. Individuals without food hoards additionally expressed more short torpor bouts and exhibited lower minimum subcutaneous temperatures during torpor than those with food stores. Thus, individuals confronted with lacking food reserves were more likely to hibernate and additionally saved energy by entering short torpor bouts more frequently and remaining at lower subcutaneous temperature both during torpor and euthermic periods. In conclusion, our results demonstrate that food store availability affects torpor expression and also highlight variation in torpor patterns and energy-saving strategies in common hamsters.
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38
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Lee TN, Richter MM, Williams CT, Tøien Ø, Barnes BM, O'Brien DM, Buck CL. Stable isotope analysis of CO 2 in breath indicates metabolic fuel shifts in torpid arctic ground squirrels. Comp Biochem Physiol A Mol Integr Physiol 2017; 209:10-15. [PMID: 28396263 DOI: 10.1016/j.cbpa.2017.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 04/04/2017] [Accepted: 04/05/2017] [Indexed: 11/19/2022]
Abstract
Stable carbon isotope ratios (δ13C) in breath show promise as an indicator of immediate metabolic fuel utilization in animals because tissue lipids have a lower δ13C value than carbohydrates and proteins. Metabolic fuel consumption is often estimated using the respiratory exchange ratio (RER), which has lipid and carbohydrate boundaries, but does not differentiate between protein and mixed fuel catabolism at intermediate values. Because lipids have relatively low δ13C values, measurements of stable carbon isotopes in breath may help distinguish between catabolism of protein and mixed fuel that includes lipid. We measured breath δ13C and RER concurrently in arctic ground squirrels (Urocitellus parryii) during steady-state torpor at ambient temperatures from -2 to -26°C. As predicted, we found a correlation between RER and breath δ13C values; however, the range of RER in this study did not reach intermediate levels to allow further resolution of metabolic substrate use with the addition of breath δ13C measurements. These data suggest that breath δ13C values are 1.1‰ lower than lipid tissue during pure lipid metabolism. From RER, we determined that arctic ground squirrels rely on nonlipid fuel sources for a significant portion of energy during torpor (up to 37%). The shift toward nonlipid fuel sources may be influenced by adiposity of the animals in addition to thermal challenge.
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Affiliation(s)
- Trixie N Lee
- Institute of Arctic Biology, 311 Irving I, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
| | - Melanie M Richter
- Department of Biological Sciences, University of Alaska Anchorage, 3101 Science Circle, Anchorage, AK 99508, USA
| | - Cory T Williams
- Institute of Arctic Biology, 311 Irving I, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Øivind Tøien
- Institute of Arctic Biology, 311 Irving I, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Brian M Barnes
- Institute of Arctic Biology, 311 Irving I, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Diane M O'Brien
- Institute of Arctic Biology, 311 Irving I, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - C Loren Buck
- Department of Biological Sciences, University of Alaska Anchorage, 3101 Science Circle, Anchorage, AK 99508, USA
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39
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Hatton JJ, Stevenson TJ, Buck CL, Duddleston KN. Diet affects arctic ground squirrel gut microbial metatranscriptome independent of community structure. Environ Microbiol 2017; 19:1518-1535. [PMID: 28251799 PMCID: PMC5417852 DOI: 10.1111/1462-2920.13712] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 02/24/2017] [Accepted: 02/24/2017] [Indexed: 12/24/2022]
Abstract
We examined the effect of diet on pre-hibernation fattening and the gut microbiota of captive arctic ground squirrels (Urocitellus parryii). We measured body composition across time and gut microbiota density, diversity and function prior to and after five-weeks on control, high-fat, low-fat (18%, 40% and 10% energy from fat, respectively), or restricted calorie (50% of control) diets. Squirrels fattened at the same rate and to the same degree on all diets. Additionally, we found no differences in gut microbiota diversity or short chain fatty acid production across time or with diet. Analysis of the gut microbial transcriptome indicated differences in community function among diet groups, but not across time, and revealed shifts in the relative contribution of function at a taxonomic level. Our results demonstrate that pre-hibernation fattening of arctic ground squirrels is robust to changes in diet and is accomplished by more than increased food intake. Although our analyses did not uncover a definitive link between host fattening and the gut microbiota, and suggest the squirrels may possess a gut microbial community structure that is unresponsive to dietary changes, studies manipulating diet earlier in the active season may yet uncover a relationship between host diet, fattening and gut microbiota.
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Affiliation(s)
| | | | - C. Loren Buck
- Northern Arizona University, Flagstaff, Arizona, 86011
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40
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MacCannell A, Sinclair K, Friesen-Waldner L, McKenzie CA, Staples JF. Water-fat MRI in a hibernator reveals seasonal growth of white and brown adipose tissue without cold exposure. J Comp Physiol B 2017; 187:759-767. [PMID: 28324157 DOI: 10.1007/s00360-017-1075-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 12/13/2016] [Accepted: 02/26/2017] [Indexed: 11/24/2022]
Abstract
Obligate hibernators, such as ground squirrels, display circannual patterns which persist even under constant laboratory conditions, suggesting that they are regulated by endogenous rhythms. Brown adipose tissue (BAT) is important for thermogenesis during periodic arousals from hibernation when core body temperature rises spontaneously from 5 to 37 °C. In most small eutherians BAT growth requires several weeks of cold exposure. We hypothesized that in the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), a hibernator, BAT growth is regulated, in part, by an endogenous rhythm and we predicted that this growth would precede the hibernation season without cold exposure. We tested this prediction using repeated water-fat magnetic resonance imaging over a year, including the hibernation season. Thoracic BAT depots increased in volume from spring through autumn even though animals were housed at ~22 °C. Subsequent cold exposure (5 °C) enlarged the thoracic BAT further. The fat fraction of this tissue fell significantly during the period of peak growth, indicating relative increases in non-triglyceride components, perhaps mitochondria or vasculature. We also found that the proportion of the body consisting of white adipose tissue (WAT) increased steadily from spring through autumn, and fell throughout hibernation, mirroring changes in body mass. Unlike BAT, WAT fat fractions remained constant (near 90%) throughout the year. Future studies will evaluate the significance of photoperiod and cold exposure on the growth of these tissues. We also found tissue with a fat fraction characteristic of BAT in the head near the eyes, a potentially novel discovery that requires further confirmation.
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Affiliation(s)
- Amanda MacCannell
- Department of Biology, University of Western Ontario, London, ON, N6A 5B8, Canada
| | - Kevin Sinclair
- Medical Biophysics, University of Western Ontario, London, ON, N6A 5B8, Canada
| | | | - Charles A McKenzie
- Medical Biophysics, University of Western Ontario, London, ON, N6A 5B8, Canada
| | - James F Staples
- Department of Biology, University of Western Ontario, London, ON, N6A 5B8, Canada.
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41
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Richter MM, Barnes BM, O'Reilly KM, Fenn AM, Buck CL. The influence of androgens on hibernation phenology of free-living male arctic ground squirrels. Horm Behav 2017; 89:92-97. [PMID: 27986541 PMCID: PMC5359051 DOI: 10.1016/j.yhbeh.2016.12.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 12/12/2016] [Indexed: 11/25/2022]
Abstract
Free-living ground squirrel species are sexually dimorphic in hibernation phenology. The underlying causes of these differences are not yet known. Androgens, testosterone (T) in particular, inhibit hibernation. To determine the influence of endogenous androgens on annual timing of hibernation we first measured circulating levels of T and dehydroepiandrosterone (DHEA), an adrenal androgen implicated in non-mating season aggression in other species, in free-living male arctic ground squirrels (Urocitellus parryii, AGS). We also manipulated endogenous androgen levels by surgical castration, and consequently compared body temperature records from intact (n=24) and castrated (n=9) males to elucidate the influence of endogenous androgens on annual body temperature cycles. The highest T levels (0.53±0.10ng/mL) were in reproductively mature male AGS in spring; whereas, both immature males in spring and all males in late summer had T levels an order of magnitude lower (0.07±0.01 and 0.06±0.00ng/mL, respectively). DHEA levels were higher in males during the late summer compared to reproductively mature males in spring (120.6±18.9 and 35.9±2.3pg/mL, respectively). Eliminating gonadal androgens via castration resulted in males delaying euthermy by extending heterothermy significantly in spring (Apr 22 ±2.9) than reproductive males (Mar 28 ±3.9) but did not change the timing of hibernation onset (castrate: Oct 12 ±1.0 vs. intact: Oct 3 ±3.1). We conclude that while androgens play a significant role in spring hibernation phenology of males, their role in fall hibernation onset is unclear.
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Affiliation(s)
- M M Richter
- Western Kentucky University, 1906 College Heights Blvd, Bowling Green, KY 42101, USA.
| | - B M Barnes
- Institute of Arctic Biology, University of Alaska Fairbanks, Alaska 99775, United States.
| | - K M O'Reilly
- Department of Biology, University of Portland, Oregon 97203, United States.
| | - A M Fenn
- Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114-2506, United States.
| | - C L Buck
- Department of Biological Sciences and Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, 86001 Arizona.
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42
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Drew KL, Frare C, Rice SA. Neural Signaling Metabolites May Modulate Energy Use in Hibernation. Neurochem Res 2017; 42:141-150. [PMID: 27878659 PMCID: PMC5284051 DOI: 10.1007/s11064-016-2109-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 10/05/2016] [Accepted: 11/11/2016] [Indexed: 12/23/2022]
Abstract
Despite an epidemic in obesity and metabolic syndrome limited means exist to effect adiposity or metabolic rate other than life style changes. Here we review evidence that neural signaling metabolites may modulate thermoregulatory pathways and offer novel means to fine tune energy use. We extend prior reviews on mechanisms that regulate thermogenesis and energy use in hibernation by focusing primarily on the neural signaling metabolites adenosine, AMP and glutamate.
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Affiliation(s)
- Kelly L Drew
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA.
| | - Carla Frare
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Sarah A Rice
- Department of Chemistry and Biochemistry, Institute of Arctic Biology, University of Alaska Fairbanks, 902 N. Koyukuk Drive, Fairbanks, AK, 99775, USA
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43
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Towards a mechanistic understanding of the responses of large terrestrial mammals to heat and aridity associated with climate change. ACTA ACUST UNITED AC 2016. [DOI: 10.1186/s40665-016-0024-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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44
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Jastroch M, Giroud S, Barrett P, Geiser F, Heldmaier G, Herwig A. Seasonal Control of Mammalian Energy Balance: Recent Advances in the Understanding of Daily Torpor and Hibernation. J Neuroendocrinol 2016; 28. [PMID: 27755687 DOI: 10.1111/jne.12437] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 10/07/2016] [Accepted: 10/15/2016] [Indexed: 12/20/2022]
Abstract
Endothermic mammals and birds require intensive energy turnover to sustain high body temperatures and metabolic rates. To cope with the energetic bottlenecks associated with the change of seasons, and to minimise energy expenditure, complex mechanisms and strategies are used, such as daily torpor and hibernation. During torpor, metabolic depression and low body temperatures save energy. However, these bouts of torpor, lasting for hours to weeks, are interrupted by active 'euthermic' phases with high body temperatures. These dynamic transitions require precise communication between the brain and peripheral tissues to defend rheostasis in energetics, body mass and body temperature. The hypothalamus appears to be the major control centre in the brain, coordinating energy metabolism and body temperature. The sympathetic nervous system controls body temperature by adjustments of shivering and nonshivering thermogenesis, with the latter being primarily executed by brown adipose tissue. Over the last decade, comparative physiologists have put forward integrative studies on the ecophysiology, biochemistry and molecular regulation of energy balance in response to seasonal challenges, food availability and ambient temperature. Mammals coping with such environments comprise excellent model organisms for studying the dynamic regulation of energy metabolism. Beyond the understanding of how animals survive in nature, these studies also uncover general mechanisms of mammalian energy homeostasis. This research will benefit efforts of translational medicine aiming to combat emerging human metabolic disorders. The present review focuses on recent advances in the understanding of energy balance and its neuronal and endocrine control during the most extreme metabolic fluctuations in nature: daily torpor and hibernation.
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Affiliation(s)
- M Jastroch
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center & German Diabetes Center (DZD), Helmholtz Zentrum München, Neuherberg, Germany
| | - S Giroud
- Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - P Barrett
- Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, UK
| | - F Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - G Heldmaier
- Animal Physiology, Philipps-Universität Marburg, Marburg, Germany
| | - A Herwig
- Zoological Institute, University of Hamburg, Hamburg, Germany
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Luu BE, Biggar KK, Wu CW, Storey KB. Torpor-responsive expression of novel microRNA regulating metabolism and other cellular pathways in the thirteen-lined ground squirrel,Ictidomys tridecemlineatus. FEBS Lett 2016; 590:3574-3582. [DOI: 10.1002/1873-3468.12435] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 09/07/2016] [Accepted: 09/08/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Bryan E. Luu
- Institute of Biochemistry and Department of Biology; Carleton University; Ottawa Canada
| | - Kyle K. Biggar
- Institute of Biochemistry and Department of Biology; Carleton University; Ottawa Canada
| | - Cheng-Wei Wu
- Institute of Biochemistry and Department of Biology; Carleton University; Ottawa Canada
| | - Kenneth B. Storey
- Institute of Biochemistry and Department of Biology; Carleton University; Ottawa Canada
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46
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Bogren LK, Johnston EL, Barati Z, Martin PA, Wojda SJ, Van Tets IG, LeBlanc AD, Donahue SW, Drew KL. The effects of hibernation and forced disuse (neurectomy) on bone properties in arctic ground squirrels. Physiol Rep 2016; 4:4/10/e12771. [PMID: 27225624 PMCID: PMC4886160 DOI: 10.14814/phy2.12771] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 03/22/2016] [Indexed: 12/11/2022] Open
Abstract
Bone loss is a well‐known medical consequence of disuse such as in long‐term space flight. Immobilization in many animals mimics the effects of space flight on bone mineral density. Decreases in metabolism are also thought to contribute to a loss of skeletal mass. Hibernating mammals provide a natural model of disuse and metabolic suppression. Hibernating ground squirrels have been shown to maintain bone strength despite long periods of disuse and decreased metabolism during torpor. This study examined if the lack of bone loss during torpor was a result of the decrease in metabolic rate during torpor or an evolutionary change in these animals affording protection against disuse. We delineated changes in bone density during natural disuse (torpor) and forced disuse (sciatic neurectomy) in the hind limbs of the arctic ground squirrel (AGS) over an entire year. We hypothesized that the animals would be resistant to bone loss due to immobilization and disuse during the winter hibernation season when metabolism is depressed but not the summer active season. This hypothesis was not supported. The animals maintained bone density (dual‐energy X‐ray absorptiometry) and most bone structural and mechanical properties in both seasons. This was observed in both natural and forced disuse, regardless of the known metabolic rate increase during the summer. However, trabecular bone volume fraction (microcomputed tomography) in the distal femur was lower in neurectomized AGS at the study endpoint. These results demonstrate a need to better understand the relationship between skeletal load (use) and bone density that may lead to therapeutics or strategies to maintain bone density in disuse conditions.
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Affiliation(s)
- Lori K Bogren
- Chemistry and Biochemistry Department, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
| | - Erin L Johnston
- Chemistry and Biochemistry Department, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
| | - Zeinab Barati
- Chemistry and Biochemistry Department, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
| | - Paula A Martin
- Chemistry and Biochemistry Department, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
| | - Samantha J Wojda
- Mechanical Engineering Department, Colorado State University, Fort Collins, Colorado
| | - Ian G Van Tets
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska
| | | | - Seth W Donahue
- Mechanical Engineering Department, Colorado State University, Fort Collins, Colorado
| | - Kelly L Drew
- Chemistry and Biochemistry Department, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
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47
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Werner JR, Gillis EA, Boonstra R, Krebs CJ. You can hide but you can't run: apparent competition, predator responses and the decline of Arctic ground squirrels in boreal forests of the southwest Yukon. PeerJ 2016; 4:e2303. [PMID: 27635312 PMCID: PMC5012268 DOI: 10.7717/peerj.2303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/07/2016] [Indexed: 11/20/2022] Open
Abstract
Throughout much of North America's boreal forest, the cyclical fluctuations of snowshoe hare populations (Lepus americanus) may cause other herbivores to become entrained in similar cycles. Alternating apparent competition via prey switching followed by positive indirect effects are the mechanisms behind this interaction. Our purpose is to document a change in the role of indirect interactions between sympatric populations of hares and arctic ground squirrels (Urocitellus parryii plesius), and to emphasize the influence of predation for controlling ground squirrel numbers. We used mark-recapture to estimate the population densities of both species over a 25-year period that covered two snowshoe hare cycles. We analysed the strength of association between snowshoe hare and ground squirrel numbers, and the changes to the seasonal and annual population growth rates of ground squirrels over time. A hyperbolic curve best describes the per capita rate of increase of ground squirrels relative to their population size, with a single stable equilibrium and a lower critical threshold below which populations drift to extinction. The crossing of this unstable boundary resulted in the subsequent uncoupling of ground squirrel and hare populations following the decline phase of their cycles in 1998. The implications are that this sustained Type II predator response led to the local extinction of ground squirrels. When few individuals are left in a colony, arctic ground squirrels may also have exhibited an Allee effect caused by the disruption of social signalling of approaching predators.
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Affiliation(s)
- Jeffery R Werner
- Biodiversity Research Centre, Department of Zoology, University of British Columbia , Vancouver , British Columbia , Canada
| | - Elizabeth A Gillis
- Department of Resource Management and Protection, Vancouver Island University , Nanaimo , British Columbia , Canada
| | - Rudy Boonstra
- Department of Biological Sciences, University of Toronto, Scarborough , Toronto , Ontario , Canada
| | - Charles J Krebs
- Department of Zoology, University of British Columbia , Vancouver , British Columbia , Canada
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48
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Logan SM, Storey KB. Tissue-specific response of carbohydrate-responsive element binding protein (ChREBP) to mammalian hibernation in 13-lined ground squirrels. Cryobiology 2016; 73:103-11. [PMID: 27614289 DOI: 10.1016/j.cryobiol.2016.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 08/31/2016] [Accepted: 09/06/2016] [Indexed: 11/18/2022]
Abstract
Mammalian hibernation is characterized by a general suppression of energy expensive processes and a switch to lipid oxidation as the primary fuel source. Glucose-responsive carbohydrate responsive element binding protein (ChREBP) has yet to be studied in hibernating organisms, which prepare for the cold winter months by feeding until they exhibit an obesity-like state that is accompanied by naturally-induced and completely reversible insulin resistance. Studying ChREBP expression and activity in the hibernating 13-lined ground squirrel is important to better understand the molecular mechanisms that regulate energy metabolism under cellular stress. Immunoblotting was used to determine the relative expression level and subcellular localization of ChREBP, as well as serine phosphorylation at 95 kDa, comparing euthermic and late torpid ground squirrel liver, kidney, heart and muscle. DNA-binding ELISAs and RT-PCR were used to explore ChREBP transcriptional activity during cold stress. ChREBP activity seemed generally suppressed in liver and kidney. During torpor, ChREBP total protein levels decreased to 44% of EC in liver, phosphoserine levels increased 2.1-fold of EC in kidney, and downstream Fasn/Pkl transcript levels decreased to <60% of EC in liver. By contrast, ChREBP activity generally increased during torpor in cardiac and skeletal muscle, where ChREBP total protein levels increased over 1.5-fold and 5-fold of EC in muscle and heart, respectively; where DNA-binding increased by ∼2-fold of EC in muscle; and where Fasn transcript levels increased over 3-fold and 7-fold in both muscle and heart, respectively. In summary, ChREBP has a tissue-specific role in regulating energy metabolism during hibernation.
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Affiliation(s)
- Samantha M Logan
- Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada
| | - Kenneth B Storey
- Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
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49
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Pilfold NW, Hedman D, Stirling I, Derocher AE, Lunn NJ, Richardson E. Mass Loss Rates of Fasting Polar Bears. Physiol Biochem Zool 2016; 89:377-88. [DOI: 10.1086/687988] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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50
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Williams CT, Wilsterman K, Zhang V, Moore J, Barnes BM, Buck CL. The secret life of ground squirrels: accelerometry reveals sex-dependent plasticity in above-ground activity. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160404. [PMID: 27703706 PMCID: PMC5043325 DOI: 10.1098/rsos.160404] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/28/2016] [Indexed: 06/06/2023]
Abstract
The sexes differ in how and when they allocate energy towards reproduction, but how this influences phenotypic plasticity in daily activity patterns is unclear. Here, we use collar-mounted light loggers and triaxial accelerometers to examine factors that affect time spent above ground and overall dynamic body acceleration (ODBA), an index of activity-specific energy expenditure, across the active season of free-living, semi-fossorial arctic ground squirrels (Urocitellus parryii). We found high day-to-day variability in time spent above ground and ODBA with most of the variance explained by environmental conditions known to affect thermal exchange. In both years, females spent more time below ground compared with males during parturition and early lactation; however, this difference was fourfold larger in the second year, possibly, because females were in better body condition. Daily ODBA positively correlated with time spent above ground in both sexes, but females were more active per unit time above ground. Consequently, daily ODBA did not differ between the sexes when females were early in lactation, even though females were above ground three to six fewer hours each day. Further, on top of having the additional burden of milk production, ODBA data indicate females also had fragmented rest patterns and were more active during late lactation. Our results indicate that sex differences in reproductive requirements can have a substantial influence on activity patterns, but the size of this effect may be dependent on capital resources accrued during gestation.
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Affiliation(s)
- Cory T. Williams
- Center for Bioengineering Innovation and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Kathryn Wilsterman
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Victor Zhang
- Center for Bioengineering Innovation and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Jeanette Moore
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Brian M. Barnes
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - C. Loren Buck
- Center for Bioengineering Innovation and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
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