Muscle strength in overwintering bears

Harlow, Henry J.; Lohuis, T.; Beck, Thomas; Iaizzo, Paul A.

doi:10.1038/35059165

Cited by 144 publications

(123 citation statements)

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“…An important adaptive consequence is that bears maintain their muscle function and conserve mobility during winter hibernation. Active protein biosynthesis during hibernation was suggested among possible mechanisms preventing muscle atrophy (16). Transcriptional changes detected in our study support the induction of translation during winter hibernation and represent a unique adaptation at the molecular level.…”

Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 49%

“…Elevated expression of multiple genes involved in protein biosynthesis is a distinctive feature of the hibernating transcriptome of black bears. Induction of protein synthesis likely represents an adaptive mechanism that contributes to a unique ability to reduce muscle atrophy over prolonged periods of immobility during winter hibernation (16). Comparing expression profiles in bears to hibernating small mammals shows a general trend during hibernation in transcriptional changes that include induction of genes involved in lipid metabolism and carbohydrate synthesis as well as depression of genes involved in the urea cycle and detoxification function in liver.…”

Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 99%

“…Bears demonstrate a unique ability to conserve muscle mass and retain strength through prolonged periods of inactivity and starvation during hibernation. In the black bear, muscle strength is reduced 23% after 130 days of inactivity, while predicted strength loss over the same period would be ϳ90% in healthy humans (16). An important adaptive consequence is that bears maintain their muscle function and conserve mobility during winter hibernation.…”

Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 99%

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Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Fedorov

Goropashnaya

Tøien

et al. 2009

Physiological Genomics

125

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We conducted a large-scale gene expression screen using the 3,200 cDNA probe microarray developed specifically for Ursus americanus to detect expression differences in liver and skeletal muscle that occur during winter hibernation compared with animals sampled during summer. The expression of 12 genes, including RNA binding protein motif 3 (Rbm3), that are mostly involved in protein biosynthesis, was induced during hibernation in both liver and muscle. The Gene Ontology and Gene Set Enrichment analysis consistently showed a highly significant enrichment of the protein biosynthesis category by overexpressed genes in both liver and skeletal muscle during hibernation. Coordinated induction in transcriptional level of genes involved in protein biosynthesis is a distinctive feature of the transcriptome in hibernating black bears. This finding implies induction of translation and suggests an adaptive mechanism that contributes to a unique ability to reduce muscle atrophy over prolonged periods of immobility during hibernation. Comparing expression profiles in bears to small mammalian hibernators shows a general trend during hibernation of transcriptional changes that include induction of genes involved in lipid metabolism and carbohydrate synthesis as well as depression of genes involved in the urea cycle and detoxification function in liver. gene expression; hibernation; translation; RNA binding protein motif 3 MAMMALIAN HIBERNATION IS a physiological and behavioral adaptation involving a coordinated suppression of heat production and body temperature wherein whole body metabolism and energy demand are significantly reduced over several days to several months. During hibernation, heart and respiration rates, blood flow, and oxygen consumption decrease dramatically to Ͻ10% of normal or basal rates (2, 4). These physiological changes do not represent a loss of homeostasis but instead are precisely controlled and spontaneously reversible, and they allow individual animals to survive highly seasonal or unpredictable environments where food availability becomes lacking (7, 12). The molecular and genetic basis of hibernation in small mammals has only recently begun to be described, and little is known about its evolutionary history. Hibernating species have been found in diverse families among seven orders of mammals (26), however, and the interspersed phylogenetic distribution of hibernating and nonhibernating species has led to the hypothesis that rather than requiring the creation of novel gene products, hibernation results from the differential expression of genes that exist widely among mammals (35).Microarray technology provides powerful means for the unbiased detection of differences in expression of thousands of genes in a single hybridization experiment (14). In contrast to single-gene expression analysis, the genome-wide approach also allows for identification of coordinated transcriptional changes in functional groups of regulatory genes within metabolic and signaling pathways. Recent studies of differential gen...

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Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 49%

Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 99%

Section: Differential Gene Expression In Hibernating Black Bearsmentioning

confidence: 99%

See 1 more Smart Citation

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Fedorov

Goropashnaya

Tøien

et al. 2009

Physiological Genomics

125

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“…Genes (with annotations in the dog genome) in the highest scoring intervals (SI Appendix, Table S8), include DAG1 (dystroglycan), which is a central component of the skeletal muscle dystrophin-associated glycoprotein complex, and is a candidate gene that in mutant form is involved with muscular dystrophy (32). Hibernating black bears lose significant muscle strength, although they retain considerably more muscle strength than humans and rodents do during the same period of inactivity (33). It is possible that DAG1 provides PBs with a mechanism to reduce muscle atrophy, perhaps in combination with urea recycling and protein conservation (34).…”

Section: Adaptation Of Pbs To Arctic Environment: Potential Signals Omentioning

confidence: 99%

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Miller

Schuster

Welch

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

328

375

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Polar bears (PBs) are superbly adapted to the extreme Arctic environment and have become emblematic of the threat to biodiversity from global climate change. Their divergence from the lower-latitude brown bear provides a textbook example of rapid evolution of distinct phenotypes. However, limited mitochondrial and nuclear DNA evidence conflicts in the timing of PB origin as well as placement of the species within versus sister to the brown bear lineage. We gathered extensive genomic sequence data from contemporary polar, brown, and American black bear samples, in addition to a 130,000-to 110,000-y old PB, to examine this problem from a genome-wide perspective. Nuclear DNA markers reflect a species tree consistent with expectation, showing polar and brown bears to be sister species. However, for the enigmatic brown bears native to Alaska's Alexander Archipelago, we estimate that not only their mitochondrial genome, but also 5-10% of their nuclear genome, is most closely related to PBs, indicating ancient admixture between the two species. Explicit admixture analyses are consistent with ancient splits among PBs, brown bears and black bears that were later followed by occasional admixture. We also provide paleodemographic estimates that suggest bear evolution has tracked key climate events, and that PB in particular experienced a prolonged and dramatic decline in its effective population size during the last ca. 500,000 years. We demonstrate that brown bears and PBs have had sufficiently independent evolutionary histories over the last 4-5 million years to leave imprints in the PB nuclear genome that likely are associated with ecological adaptation to the Arctic environment.demographic history | hybridization | mammalian genomics | phylogenetics G enome-scale studies of speciation and admixture have become essential tools in evolutionary analyses of recently diverged lineages. For example, paradigm-shifting genomic research on archaic and anatomically modern humans has identified critical gene flow events during hominin history (1, 2). However, aside from several analyses of domesticated species and their wild relatives (e.g., ref.3), studies that use whole-genome sequencing to investigate admixture in wildlife populations are only now beginning to emerge.The bear family (Ursidae, Mammalia) represents an excellent, largely untapped model for investigating complex speciation and rapid evolution of distinct phenotypes. Although polar bears (PBs; Ursus maritimus) and brown bears (Ursus arctos) are considered separate species, analyses of fossil evidence and mitochondrial sequence data have indicated a recent divergence of PBs from within brown bears (surveyed in ref. 4). For example, phylogenetic analyses of complete mitochondrial genomes, including from a unique 130,000-to 110,000-y-old PB jawbone from Svalbard, Norway, confirmed a particularly close relationship between PB and a genetically isolated population of brown bears from the Admiralty, Baranof, and Chichagof islands in Alaska's Alexander Archipelago (hereaf...

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“…A hibernating brown bear (Ursus arctos) routinely spends 5-7 mo per year in continuous dormancy with no food or water intake, no urination, and no defecation (19,36). During this time, bears appear to be resistant to loss of muscle mass, strength, or bone density (18,24,29,43,14,44). During hibernation bear body temperature is downregulated only slightly, fluctuating from ϳ37°C to a minimum of 30°C, as found in brown and in black bears (Ursus americanus) (17,26,27,36,43), whereas O 2 consumption rate is downregulated by 75% (43).…”

mentioning

confidence: 99%

Decrease in the red cell cofactor 2,3-diphosphoglycerate increases hemoglobin oxygen affinity in the hibernating brown bearUrsus arctos

Revsbech

Malte

Fröbert

et al. 2013

American Journal of Physiology-Regulatory, Integrative and Comp

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consumption rate to ϳ25% compared with the active state, while body temperature decreases moderately (to ϳ30°C), suggesting a temperature-independent component in their metabolic depression. To establish whether changes in O 2 consumption during hibernation correlate with changes in blood O2 affinity, we took blood samples from the same six individuals of hibernating and nonhibernating free-ranging brown bears during winter and summer, respectively. A single hemoglobin (Hb) component was detected in all samples, indicating no switch in Hb synthesis. O 2 binding curves measured on red blood cell lysates at 30°C and 37°C showed a less temperature-sensitive O2 affinity than in other vertebrates. Furthermore, hemolysates from hibernating bears consistently showed lower cooperativity and higher O2 affinity than their summer counterparts, regardless of the temperature. We found that this increase in O2 affinity was associated with a significant decrease in the red cell Hb-cofactor 2,3-diphosphoglycerate (DPG) during hibernation to approximately half of the summer value. Experiments performed on purified Hb, to which DPG had been added to match summer and winter levels, confirmed that the low DPG content was the cause of the left shift in the Hb-O 2 equilibrium curve during hibernation. Levels of plasma lactate indicated that glycolysis is not upregulated during hibernation and that metabolism is essentially aerobic. Calculations show that the increase in Hb-O2 affinity and decrease in cooperativity resulting from decreased red cell DPG may be crucial in maintaining a fairly constant tissue oxygen tension during hibernation in vivo. metabolic suppression; body temperature; oxygen binding curves; heat of oxygenation; hibernation A DISTINCT TRAIT OF MAMMALIAN hibernation is the highly controlled decrease in body temperature and metabolic rate. A hibernating brown bear (Ursus arctos) routinely spends 5-7 mo per year in continuous dormancy with no food or water intake, no urination, and no defecation (19,36). During this time, bears appear to be resistant to loss of muscle mass, strength, or bone density (18,24,29,43,14,44). During hibernation bear body temperature is downregulated only slightly, fluctuating from ϳ37°C to a minimum of 30°C, as found in brown and in black bears (Ursus americanus) (17,26,27,36,43), whereas O 2 consumption rate is downregulated by 75% (43). In comparison, in most smaller hibernators, such as ground squirrels and marmots, body temperature drops dramatically to values close to ambient temperatures (32, 37, 48), with a consequent strong Q 10 -induced depression of metabolic rate (where Q 10 is the rate coefficient for a 10°C change in temperature). In spite of substantial downregulation of ventilation and heart rate, most hibernators likely experience only slight or no hypoxia and in some ground squirrels arterial O 2 tension (PO 2 ) is normal during torpor (16). As opposed to smaller hibernators that exhibit periods of spontaneous arousals back to normothermic temperature and metabolic rate (33...

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Muscle strength in overwintering bears

Cited by 144 publications

References 6 publications

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Decrease in the red cell cofactor 2,3-diphosphoglycerate increases hemoglobin oxygen affinity in the hibernating brown bearUrsus arctos

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