Seasonal variation in haematological and biochemical variables in free-ranging subadult brown bears (Ursus arctos) in Sweden

Græsli, Anne Randi; Evans, Alina L.; Fahlman, Åsa; Bertelsen, Mads F.; Blanc, Stéphane; Arnemo, Jon M.

doi:10.1186/s12917-015-0615-2

Cited by 44 publications

(38 citation statements)

References 31 publications

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“…Hibernators experience extended periods of food shortage during hibernation and primarily rely on mobilization of fat stores from white adipose tissue [1]. Accordingly, we found that the concentration of total circulating fatty acids was elevated in hibernating bears, a nding in line with previous studies [5,44]. Considering both the amount and relative proportions of circulating lipids, our results are consistent with changes in serum and plasma lipid pro les during hibernation that have been previously published [5,9,10], notably an enrichment in DHA C22:6 n-3 and depletions in ALA C18:3 n-3 and EPA C20:5 n-3, during winter compared to summer.…”

Section: Discussionsupporting

confidence: 91%

Specific shifts in the endocannabinoid system in hibernating brown bears

Boyer

Cussonneau

Brun

et al. 2020

Preprint

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In small hibernators, global downregulation of the endocannabinoid system (ECS), which is involved in modulating neuronal signaling, feeding behavior, energy metabolism, and circannual rhythms, has been reported to possibly drive physiological adaptation to the hibernating state. In hibernating brown bears ( Ursus arctos ), we hypothesized that beyond an overall suppression of the ECS, seasonal shift in endocannabinoids compounds could be linked to bear’s peculiar features that include hibernation without arousal episodes and capacity to react to external disturbance. We explored circulating lipids in serum and the ECS in plasma and metabolically active tissues in free-ranging subadult Scandinavian brown bears when both active and hibernating. In winter bear serum, in addition to a 2-fold increase in total fatty acid concentration, we found significant changes in relative proportions of circulating fatty acids, such as a 2-fold increase in docosahexaenoic acid C22:6 n-3 and a decrease in arachidonic acid C20:4 n-6. In adipose and muscle tissues of hibernating bears, we found significant lower concentrations of 2-arachidonoylglycerol (2-AG), a major ligand of cannabinoid receptors 1 (CB1) and 2 (CB2). Lower mRNA level for genes encoding CB1 and CB2 were also found in winter muscle and adipose tissue, respectively. The observed reduction in ECS tone may promote fatty acid mobilization from body fat stores, and favor carbohydrate metabolism in skeletal muscle of hibernating bears. Additionally, high circulating level of the endocannabinoid-like compound N-oleoylethanolamide (OEA) in winter could favor lipolysis and fatty acid oxidation in peripheral tissues. We also speculated on a role of OEA in the conservation of an anorexigenic signal and in the maintenance of torpor during hibernation, while sustaining the capacity of bears to sense stimuli from the environment.

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Section: Discussionsupporting

confidence: 91%

Specific shifts in the endocannabinoid system in hibernating brown bears

Boyer

Cussonneau

Brun

et al. 2020

Preprint

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“…In general, an increased GGT level indicates that the liver is damaged but does not specifically point to a condition that may be causing the injury. However, we could not find any clinical evidence of liver disease, and the GGT values in our study are similar to those of other bear species (Storm et al 1988;Graesli et al 2015). There were no differences the level of GLU by season and age in this study, although it is generally influenced by stress or metabolic rate.…”

Section: Discussionmentioning

confidence: 38%

“…This may be due to the shift from carbohydrate and protein metabolism to fat metabolism. These physiological changes result in decreased urea production and reduced demand for the enzymes important for protein breakdown (Graesli et al 2015).…”

Section: Discussionmentioning

confidence: 99%

“…Veterinarni Medicina, 62, 2017(10): 533-540 doi: 10.17221/166/2016 ed for American black bears (Ursus americanus; Matula et al 1980;Nelson et al 1984;Schroeder 1987;Hellgren et al 1993), brown bears (Ursus arctos; Nelson et al 1983;Brannon 1985;Hissa et al 1994;Huber et al 1997;Graesli et al 2014;Graesli et al 2015) and polar bears (Ursus maritimus; Nelson et al 1983;Derocher et al 1990;Ramsay et al 1991;Tryland et al 2002). These studies described blood chemistry or haematology values in these species and discussed several physiological factors that could affect them.…”

Section: Original Papermentioning

confidence: 99%

“…Bears undergo notable metabolic changes during hibernation, although many of the mechanisms regulating hibernation remain to be elucidated. Hibernating bears mainly metabolise stored fat reserves because they ingest no food or water for months, and their urea production decreases partly owing to the shift from protein to fat metabolism during hibernation (Graesli et al 2015).…”

Section: Animalsmentioning

confidence: 99%

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Blood chemistry reference intervals of captive Asiatic black bears (Ursus thibetanus)

Jeong¹,

Um²,

Lee³

et al. 2017

Vet. Med. - Czech

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Data on blood chemistry values can make fundamental contributions to our understanding of physiological changes. However, there is a lack of information regarding blood chemistry in Asiatic black bears (Ursus thibetanus). Thus, the objects of this study were to determine reference ranges for 29 blood chemistry variables, and to evaluate differences between age groups and between seasons. Blood samples (n = 138) were collected from 44 (20 males, 24 females; age range, 1-15 years) clinically healthy, captive Asiatic black bears (Ursus thibetanus) in the Republic of Korea. Young and adult bears showed significantly higher levels of creatinine and total cholesterol, and lower levels of blood urea nitrogen, blood urea nitrogen/creatinine ratio, lactate dehydrogenase and creatine kinase MB during hibernation compared to during non-hibernation. Adults also showed significantly higher levels of triglyceride, but lower levels of inorganic phosphorus, aspartate transaminase, alkaline phosphatase, high density lipoprotein cholesterol and creatine phosphokinase during hibernation than during non-hibernation. During hibernation, the urea nitrogen/creatinine ratio and levels of alkaline phosphatase, lactate dehydrogenase, and creatine phosphokinase in young bears were significantly higher than in adults, whereas creatinine levels were lower than in adults. During non-hibernation, the urea nitrogen/creatinine ratio and levels of calcium, alkaline phosphatase, lactate dehydrogenase, creatine phosphokinase and creatine kinase MB in young bears were significantly higher, whereas creatinine, total protein, albumin, gamma-glutamyl transferase and haemoglobin levels were lower than in adults. The results of this study provide reference values that will aid in understanding the physiology of Asiatic black bears and in assessing the health of these animals in captive environments.Keywords: Asiatic black bear; reference ranges; hibernation; blood chemistry; captivity; health assessment List of abbreviations ALB = albumin, ALP = alkaline phosphatase, ALT = alanine aminotransferase, AMY = amylase, AST = aspartate aminotransferase, BUN = blood urea nitrogen, CKMB = creatine kinase MB, CPK = creatine phosphokinase, CRE = creatinine, CRP = C-reactive protein, DBIL = direct bilirubin, GGT = gamma-glutamyl transferase, GLU = glucose, Hb = haemoglobin, HDLC = high density lipoprotein cholesterol, IP = inorganic phosphorus, LDH = lactate dehydrogenase, TBIL = total bilirubin, TCHO = total cholesterol, TG = triglyceride, TP = total protein, U/C = blood urea nitrogen to creatinine ratio, UA = uric acidBlood chemistry values can play a fundamental role in facilitating an understanding of physiological changes and in assessing potential health problems at both individual and population levels (Geffre et al. 2009;Friedrichs et al. 2012). Previously, blood chemistry data have been report-

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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 variation in haematological and biochemical variables in free-ranging subadult brown bears (Ursus arctos) in Sweden

Cited by 44 publications

References 31 publications

Specific shifts in the endocannabinoid system in hibernating brown bears

Specific shifts in the endocannabinoid system in hibernating brown bears

Blood chemistry reference intervals of captive Asiatic black bears (Ursus thibetanus)

Denning in brown bears

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