Seasonal changes in eicosanoid metabolism in the brown bear

Giroud, Sylvain; Evans, Alina L.; Chery, Isabelle; Bertile, Fabrice; Tascher, Georg; Bertrand‐Michel, Justine; Gauquelin‐Koch, Guillemette; Arnemo, Jon M.; Swenson, Jon E.; Lefai, Étienne; Blanc, Stéphane; Simon, Chantal

doi:10.1007/s00114-018-1583-8

Cited by 17 publications

(17 citation statements)

References 76 publications

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“…Gene enrichment analysis of CN-differentiated genes also revealed an enrichment of genes involved in the categories of arachidonic acid and eicosanoid metabolism (SI Appendix, Tables S6-S9). Eicosanoids derive from arachidonic acid and play important roles in inflammation, thermoregulation, and cardiovascular function (56). Interestingly, most of the differentiated CN-variable genes involved in fatty acid metabolism are present at lower CN in polar bears and are perhaps related to the unique polar bear metabolic rates (57)(58)(59).…”

Section: Discussionmentioning

confidence: 99%

Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift

Rinker

Specian

Zhao

et al. 2019

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

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Polar bear (Ursus maritimus) and brown bear (Ursus arctos) are recently diverged species that inhabit vastly differing habitats. Thus, analysis of the polar bear and brown bear genomes represents a unique opportunity to investigate the evolutionary mechanisms and genetic underpinnings of rapid ecological adaptation in mammals. Copy number (CN) differences in genomic regions between closely related species can underlie adaptive phenotypes and this form of genetic variation has not been explored in the context of polar bear evolution. Here, we analyzed the CN profiles of 17 polar bears, 9 brown bears, and 2 black bears (Ursus americanus). We identified an average of 318 genes per individual that showed evidence of CN variation (CNV). Nearly 200 genes displayed species-specific CN differences between polar bear and brown bear species. Principal component analysis of gene CN provides strong evidence that CNV evolved rapidly in the polar bear lineage and mainly resulted in CN loss. Olfactory receptors composed 47% of CN differentiated genes, with the majority of these genes being at lower CN in the polar bear. Additionally, we found significantly fewer copies of several genes involved in fatty acid metabolism as well as AMY1B, the salivary amylase-encoding gene in the polar bear. These results suggest that natural selection shaped patterns of CNV in response to the transition from an omnivorous to primarily carnivorous diet during polar bear evolution. Our analyses of CNV shed light on the genomic underpinnings of ecological adaptation during polar bear evolution.

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Section: Discussionmentioning

confidence: 99%

Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift

Rinker

Specian

Zhao

et al. 2019

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

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“…The availability of sufficient omega-6 PUFA, i.e., C20:4ω6, precursors for PG synthesis was apparently important in spring, when the animals become reproductively active (Arnold et al, 2012). In brown bears, levels of major eicosanoids, irrespective of their anti- and pro-inflammatory properties, are significantly reduced during winter hibernation compared to the summer active state (Giroud et al, 2018a). In particular, plasma and muscle concentrations of specific epoxyeicosatrienoic acids (EET), namely 5,6-EET and 8,9-EET, were lower in hibernating bears than in summer active individuals.…”

Section: Discussionmentioning

confidence: 99%

Lipidomics Reveals Seasonal Shifts in a Large-Bodied Hibernator, the Brown Bear

et al. 2019

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Prior to winter, heterotherms retain polyunsaturated fatty acids (“PUFA”), resulting in enhanced energy savings during hibernation, through deeper and longer torpor bouts. Hibernating bears exhibit a less dramatic reduction (2–5°C) in body temperature, but lower their metabolism to a degree close to that of small hibernators. We determined the lipid composition, via lipidomics, in skeletal muscle and white adipose tissues (“WAT”), to assess lipid retention, and in blood plasma, to reflect lipid trafficking, of winter hibernating and summer active wild Scandinavian brown bears ( Ursus arctos ). We found that the proportion of monounsaturated fatty acids in muscle of bears was significantly higher during winter. During hibernation, omega-3 PUFAs were retained in WAT and short-length fatty acids were released into the plasma. The analysis of individual lipid moieties indicated significant changes of specific fatty acids, which are in line with the observed seasonal shift in the major lipid categories and can be involved in specific regulations of metabolisms. These results strongly suggest that the shift in lipid composition is well conserved among hibernators, independent of body mass and of the animals’ body temperature.

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“…The high concentrations of free fatty acids (FA) and glycerol might be the result of their release from adipose tissue during hibernation (Welinder et al, 2016), with short chain (easier oxidation) of FAs being released and retained in muscle and tissue adipose than long FA chains, as it occurs in other hibernating mammals (Giroud et al, 2019). Long chain of FAs, such as Omega 3 and Omega 6, some of which are responsible for carbohydrate metabolism and protein sparing in bear muscles (Chazarin, Storey, et al, 2019), vary their concentration in muscles and plasma differently between the active and hibernating states (Giroud et al, 2018).…”

Section: Lipid Metabolismmentioning

confidence: 99%

“…However, metabolites as eicosanoids decrease or do not vary their concentration during hibernation (regardless of their pro or antiinflammatory properties), suggesting that the hibernation period is associated with a depressed state of the eicosanoid cascade (Giroud et al, 2018). Adiponectin is secreted exclusively in adipose tissue and is responsible for inducing insulin resistance to regulate the oxidation of fatty acids (Havel, 2002;You, Considine, Leone, Kelly, & Crabb, 2005), which may help maintain lipogenesis during the hyperphagia when bears need to store fat, whereas the decrease during…”

Section: Lipid Metabolismmentioning

confidence: 99%

“…During hibernation brown bears experience shivering , with periods that can exceed an hour in duration where activations lasting less than 0.2 s and occur every 3-10 s. Shivering may stimulate skeletal muscles enough to maintain muscular fitness (captive brown bears, Lin, Hershey, Mattoon, & Robbins, 2012). It has also been suggested that the plasma of hibernating bears has antiproteolytic properties, thus inhibiting muscle loss (Chanon et al, 2018;Fuster, Busquets, Almendro, López-Soriano, & Argilés, 2007;Salmov et al, 2015) and that constant levels of prostaglandins in muscle could contribute to muscle sparing in bears (Giroud et al, 2018).…”

Section: Skeletal Response To Hibernation Bone Turnover and Changementioning

confidence: 99%

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Denning in brown bears

González-Bernardo

Russo

Valderrábano

et al. 2020

Ecology and Evolution

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Hibernation represents an adaptation for coping with unfavorable environmental conditions. For brown bears Ursus arctos, hibernation is a critical period as pronounced temporal reductions in several physiological functions occur. Here, we review the three main aspects of brown bear denning: (1) den chronology, (2) den characteristics, and (3) hibernation physiology in order to identify (a) proximate and ultimate factors of hibernation as well as (b) research gaps and conservation priorities. Den chronology, which varies by sex and reproductive status, depends on environmental factors, such as snow, temperature, food availability, and den altitude. Significant variation in hibernation across latitudes occurs for both den entry and exit. The choice of a den and its surroundings may affect individual fitness, for example, loss of offspring and excessive energy consumption. Den selection is the result of broad‐ and fine‐scale habitat selection, mainly linked to den insulation, remoteness, and availability of food in the surroundings of the den location. Hibernation is a metabolic challenge for the brown bears, in which a series of physiological adaptations in tissues and organs enable survival under nutritional deprivation, maintain high levels of lipids, preserve muscle, and bone and prevent cardiovascular pathologies such as atherosclerosis. It is important to understand: (a) proximate and ultimate factors in denning behavior and the difference between actual drivers of hibernation (i.e., factors to which bears directly respond) and their correlates; (b) how changes in climatic factors might affect the ability of bears to face global climate change and the human‐mediated changes in food availability; (c) hyperphagia (period in which brown bears accumulate fat reserves), predenning and denning periods, including for those populations in which bears do not hibernate every year; and (d) how to approach the study of bear denning merging insights from different perspectives, that is, physiology, ecology, and behavior.

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Seasonal changes in eicosanoid metabolism in the brown bear

Cited by 17 publications

References 76 publications

Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift

Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift

Lipidomics Reveals Seasonal Shifts in a Large-Bodied Hibernator, the Brown Bear

Denning in brown bears

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