Cardiac adaptation in hibernating, free-ranging Scandinavian Brown Bears (Ursus arctos)

Jørgensen, Peter Godsk; Evans, Alina L.; Kindberg, Jonas; Olsen, Lisbeth H.; Galatius, Søren; Fröbert, Ole

doi:10.1038/s41598-019-57126-y

Cited by 12 publications

(15 citation statements)

References 40 publications

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“…Changes in serum proteins during hibernation may also be protective during the vulnerable hibernation period including increased capacity for bone maintenance and wound healing 38 . Other cardiac adaptions during hibernation, such as decreased functional measures of myocardial velocities 39 may also be operative. Finally, a metabolic switch that shunts choline to generate betaine instead of the pro-atherogenic toxin Trimetylamine N-oxide (TMAO) during hibernation could hold clues for novel treatment options in burden of lifestyle diseases 40 .…”

Section: Discussionmentioning

confidence: 99%

Potential natural immunization against atherosclerosis in hibernating bears

Samal

Fröbert

Kindberg

et al. 2021

Sci Rep

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Brown bears (Ursus arctos) hibernate for 5–6 months during winter, but despite kidney insufficiency, dyslipidemia and inactivity they do not seem to develop atherosclerosis or cardiovascular disease (CVD). IgM antibodies against phosphorylcholine (anti-PC) and malondialdehyde (anti-MDA) are associated with less atherosclerosis, CVD and mortality in uremia in humans and have anti-inflammatory and other potentially protective properties. PC but not MDA is exposed on different types of microorganisms. We determine anti-PC and anti-MDA in brown bears in summer and winter. Paired serum samples from 12 free ranging Swedish brown bears were collected during hibernation in winter and during active state in summer and analyzed for IgM, IgG, IgG1/2 and IgA anti-PC and anti-MDA by enzyme linked immunosorbent assay (ELISA). When determined as arbitrary units (median set at 100 for summer samples), significantly raised levels were observed in winter for anti-PC subclasses and isotypes, and for IgA anti-PC the difference was striking; 100 IQR (85.9–107.9) vs 782.3, IQR (422.8–1586.0; p < 0.001). In contrast, subclasses and isotypes of anti-MDA were significantly lower in winter except IgA anti-MDA, which was not detectable. Anti-PCs are significantly raised during hibernation in brown bears; especially IgA anti-PC was strikingly high. In contrast, anti-MDA titers was decreased during hibernation. Our observation may represent natural immunization with microorganisms during a vulnerable period and could have therapeutic implications for prevention of atherosclerosis.

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Section: Discussionmentioning

confidence: 99%

Potential natural immunization against atherosclerosis in hibernating bears

Samal

Fröbert

Kindberg

et al. 2021

Sci Rep

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“…In black and brown bears, a significant decline in the average heart rate from 50 to 80 beats per minute during the summer-active period to 10–30 beats per minute during winter months has been reported (Folk et al, 1980 ; Nelson et al, 2008 ; Nelson and Robbins, 2010 , 2015 ; Laske et al, 2011 ; Toien et al, 2011 ; Evans et al, 2012 ; Jorgensen et al, 2014 , 2020 ). Also in bears, the respiratory rate drops from 10 to 12 breaths per minute during summer to 5–7 breaths per minute in bears during the winter (Laske et al, 2011 ; Evans et al, 2012 ).…”

Section: Maintenance Of Lean Body Mass In Hibernators During Wintermentioning

confidence: 99%

Body Protein Sparing in Hibernators: A Source for Biomedical Innovation

et al. 2021

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Proteins are not only the major structural components of living cells but also ensure essential physiological functions within the organism. Any change in protein abundance and/or structure is at risk for the proper body functioning and/or survival of organisms. Death following starvation is attributed to a loss of about half of total body proteins, and body protein loss induced by muscle disuse is responsible for major metabolic disorders in immobilized patients, and sedentary or elderly people. Basic knowledge of the molecular and cellular mechanisms that control proteostasis is continuously growing. Yet, finding and developing efficient treatments to limit body/muscle protein loss in humans remain a medical challenge, physical exercise and nutritional programs managing to only partially compensate for it. This is notably a major challenge for the treatment of obesity, where therapies should promote fat loss while preserving body proteins. In this context, hibernating species preserve their lean body mass, including muscles, despite total physical inactivity and low energy consumption during torpor, a state of drastic reduction in metabolic rate associated with a more or less pronounced hypothermia. The present review introduces metabolic, physiological, and behavioral adaptations, e.g., energetics, body temperature, and nutrition, of the torpor or hibernation phenotype from small to large mammals. Hibernating strategies could be linked to allometry aspects, the need for periodic rewarming from torpor, and/or the ability of animals to fast for more or less time, thus determining the capacity of individuals to save proteins. Both fat- and food-storing hibernators rely mostly on their body fat reserves during the torpid state, while minimizing body protein utilization. A number of them may also replenish lost proteins during arousals by consuming food. The review takes stock of the physiological, molecular, and cellular mechanisms that promote body protein and muscle sparing during the inactive state of hibernation. Finally, the review outlines how the detailed understanding of these mechanisms at play in various hibernators is expected to provide innovative solutions to fight human muscle atrophy, to better help the management of obese patients, or to improve the ex vivo preservation of organs.

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“…As a result of a decrease in metabolic rate and activity, hibernating brown bears exhibit marked bradycardia in which the heart rate decreases between 63% and 80% (unanesthetized bears: (Evans et al, 2016); anesthetized bears: (Folk et al, 1972;Jørgensen et al, 2014Jørgensen et al, , 2020Nelson & Robbins, 2010)). However, blood pressure does not seem to change during hibernation (Nelson, McEwen, Robbins, Felicetti, & Christensen, 2003).…”

Section: Response Of the Circulatory System To Hibernationmentioning

confidence: 99%

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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Cardiac adaptation in hibernating, free-ranging Scandinavian Brown Bears (Ursus arctos)

Cited by 12 publications

References 40 publications

Potential natural immunization against atherosclerosis in hibernating bears

Potential natural immunization against atherosclerosis in hibernating bears

Body Protein Sparing in Hibernators: A Source for Biomedical Innovation

Denning in brown bears

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