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Lewis CTA, Melhedegaard EG, Ognjanovic MM, Olsen MS, Laitila J, Seaborne RAE, Gronset M, Zhang C, Iwamoto H, Hessel AL, Kuehn MN, Merino C, Amigo N, Frobert O, Giroud S, Staples JF, Goropashnaya AV, Fedorov VB, Barnes B, Toien O, Drew K, Sprenger RJ, Ochala J. Remodeling of skeletal muscle myosin metabolic states in hibernating mammals. eLife 2024; 13:RP94616. [PMID: 38752835 PMCID: PMC11098559 DOI: 10.7554/elife.94616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024] Open
Abstract
Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.
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Affiliation(s)
| | | | - Marija M Ognjanovic
- Department of Biomedical Sciences, University of CopenhagenCopenhagenDenmark
| | - Mathilde S Olsen
- Department of Biomedical Sciences, University of CopenhagenCopenhagenDenmark
| | - Jenni Laitila
- Department of Biomedical Sciences, University of CopenhagenCopenhagenDenmark
| | - Robert AE Seaborne
- Department of Biomedical Sciences, University of CopenhagenCopenhagenDenmark
- Centre for Human and Applied Physiological Sciences, Faculty of Life Sciences & Medicine, King’s College LondonLondonUnited Kingdom
| | - Magnus Gronset
- Department of Cellular and Molecular Medicine, University of CopenhagenCopenhagenDenmark
| | - Changxin Zhang
- Department of Computational Medicine and Bioinformatics, University of MichiganAnn ArborUnited States
| | - Hiroyuki Iwamoto
- Spring-8, Japan Synchrotron Radiation Research InstituteHyogoJapan
| | - Anthony L Hessel
- Institute of Physiology II, University of MuensterMuensterGermany
- Accelerated Muscle Biotechnologies ConsultantsBostonUnited States
| | - Michel N Kuehn
- Institute of Physiology II, University of MuensterMuensterGermany
- Accelerated Muscle Biotechnologies ConsultantsBostonUnited States
| | | | | | - Ole Frobert
- Department of Clinical Medicine, Faculty of Health, Aarhus UniversityAarhusDenmark
- Faculty of Health, Department of Cardiology, Örebro UniversityÖrebroSweden
| | - Sylvain Giroud
- Energetics Lab, Department of Biology, Northern Michigan UniversityMarquetteUnited States
- Research Institute of Wildlife Ecology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine ViennaViennaAustria
| | - James F Staples
- Department of Biology, University of Western OntarioLondonCanada
| | - Anna V Goropashnaya
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
| | - Vadim B Fedorov
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
| | - Brian Barnes
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
| | - Oivind Toien
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
| | - Kelly Drew
- Center for Transformative Research in Metabolism, Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
| | - Ryan J Sprenger
- Department of Zoology, University of British ColumbiaVancouverCanada
| | - Julien Ochala
- Department of Biomedical Sciences, University of CopenhagenCopenhagenDenmark
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Lewis CTA, Melhedegaard EG, Ognjanovic MM, Olsen MS, Laitila J, Seaborne RAE, Gronset MN, Zhang C, Iwamoto H, Hessel AL, Kuehn MN, Merino C, Amigo N, Frobert O, Giroud S, Staples JF, Goropashnaya AV, Fedorov VB, Barnes BM, Toien O, Drew KL, Sprenger RJ, Ochala J. Remodelling of Skeletal Muscle Myosin Metabolic States in Hibernating Mammals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.14.566992. [PMID: 38014200 PMCID: PMC10680686 DOI: 10.1101/2023.11.14.566992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20°C). Upon repeating loaded Mant-ATP chase experiments at 8°C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.
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Hunstiger M, Johannsen MM, Oliver SR. Non-shivering thermogenesis is differentially regulated during the hibernation season in Arctic ground squirrels. Front Physiol 2023; 14:1207529. [PMID: 37520836 PMCID: PMC10372343 DOI: 10.3389/fphys.2023.1207529] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 06/22/2023] [Indexed: 08/01/2023] Open
Abstract
Arctic ground squirrels are small mammals that experience physiological extremes during the hibernation season. Body temperature rises from 1°C to 40°C during interbout arousal and requires tight thermoregulation to maintain rheostasis. Tissues from wild-caught Arctic ground squirrels were sampled over 9 months to assess the expression of proteins key to thermogenic regulation. Animals were sacrificed while aroused, and the extensor digitorum longus, diaphragm, brown adipose tissue, and white adipose tissue were probed using Western blots to assess protein expression and blood was sampled for metabolite analysis. Significant seasonal expression patterns emerged showing differential regulation. Contrary to our prediction, white adipose tissue showed no expression of uncoupling protein 1, but utilization of uncoupling protein 1 peaked in brown adipose tissue during the winter months and began to taper after terminal arousal in the spring. The opposite was true for muscular non-shivering thermogenesis. Sarco/endoplasmic reticulum calcium ATPase 1a and 2a expressions were depressed during the late hibernation season and rebounded after terminal arousal in diaphragm tissues, but only SERCA2a was differentially expressed in the extensor digitorum longus. The uncoupler, sarcolipin, was only detected in diaphragm samples and had a decreased expression during hibernation. The differential timing of these non-shivering pathways indicated distinct functions in maintaining thermogenesis which may depend on burrow temperature, availability of endogenous resources, and other seasonal activity demands on these tissues. These results could be impacted by fiber type makeup of the muscles collected, the body weight of the animal, and the date of entrance or exit from hibernation.
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Affiliation(s)
- Moriah Hunstiger
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Michelle Marie Johannsen
- 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
| | - S. Ryan Oliver
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
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Sajdak BS, Salmon AE, Litts KM, Wells C, Allen KP, Dubra A, Merriman DK, Carroll J. Evaluating seasonal changes of cone photoreceptor structure in the 13-lined ground squirrel. Vision Res 2019; 158:90-99. [PMID: 30826354 PMCID: PMC6538439 DOI: 10.1016/j.visres.2019.02.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/21/2019] [Accepted: 02/24/2019] [Indexed: 12/15/2022]
Abstract
Cone photoreceptors of the 13-lined ground squirrel (13-LGS) undergo reversible structural changes during hibernation, including cone outer segment disc degeneration and inner segment mitochondria depletion. Here, we evaluated cone structure with adaptive optics scanning light ophthalmoscopy (AOSLO) before, during, and after hibernation. Also, intra-animal comparisons of cone structure were made at distinct physiological states (pre-hibernation, torpor, interbout euthermia, and post-hibernation) with AOSLO and transmission electron microscopy. Our results indicate that the 13-LGS cone mosaic is only transiently affected by structural remodeling during hibernation. Outer segment remodeling starts during torpid states during a period of fall transition in room temperature, with more severe structural changes during bouts of torpor in cold temperature. Cones return to euthermic-like structure during brief periods of interbout euthermia and recover normal waveguiding properties as soon as 24 h post-hibernation. Cone structure is visible with split-detector AOSLO throughout hibernation, providing evidence that intact outer segments are not necessary to visualize cones with this technique. Despite the changes to cone structure during hibernation, cone density and packing remained unchanged throughout the seasonal cycle. Pairing non-invasive imaging with ultrastructural assessment may provide insight to the biological origins of cone photoreceptor signals observed with AOSLO.
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Affiliation(s)
- Benjamin S Sajdak
- Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Alexander E Salmon
- Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Katie M Litts
- Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Clive Wells
- Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Kenneth P Allen
- Biomedical Resource Center, Medical College of Wisconsin, Milwaukee, WI, USA; Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Alfredo Dubra
- Ophthalmology, Stanford University, Stanford, CA, USA
| | | | - Joseph Carroll
- Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA; Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI, USA; Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.
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Seasonal and post-trauma remodeling in cone-dominant ground squirrel retina. Exp Eye Res 2016; 150:90-105. [PMID: 26808487 DOI: 10.1016/j.exer.2016.01.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 12/14/2015] [Accepted: 01/14/2016] [Indexed: 02/02/2023]
Abstract
With a photoreceptor mosaic containing ∼85% cones, the ground squirrel is one of the richest known mammalian sources of these important retinal cells. It also has a visual ecology much like the human's. While the ground squirrel retina is understandably prominent in the cone biochemistry, physiology, and circuitry literature, far less is known about the remodeling potential of its retinal pigment epithelium, neurons, macroglia, or microglia. This review aims to summarize the data from ground squirrel retina to this point in time, and to relate them to data from other brain areas where appropriate. We begin with a survey of the ground squirrel visual system, making comparisons with traditional rodent models and with human. Because this animal's status as a hibernator often goes unnoticed in the vision literature, we then present a brief primer on hibernation biology. Next we review what is known about ground squirrel retinal remodeling concurrent with deep torpor and with rapid recovery upon re-warming. Notable here is rapidly-reversible, temperature-dependent structural plasticity of cone ribbon synapses, as well as pre- and post-synaptic plasticity throughout diverse brain regions. It is not yet clear if retinal cell types other than cones engage in torpor-associated synaptic remodeling. We end with the small but intriguing literature on the ground squirrel retina's remodeling responses to insult by retinal detachment. Notable for widespread loss of (cone) photoreceptors, there is surprisingly little remodeling of the RPE or Müller cells. Microglial activation appears minimal, and remodeling of surviving second- and third-order neurons seems absent, but both require further study. In contrast, traumatic brain injury in the ground squirrel elicits typical macroglial and microglial responses. Overall, the data to date strongly suggest a heretofore unrecognized, natural checkpoint between retinal deafferentiation and RPE and Müller cell remodeling events. As we continue to discover them, the unique ways by which ground squirrel retina responds to hibernation or injury may be adaptable to therapeutic use.
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