The effect of metabolic fuel availability on thermoregulation and torpor in a marsupial hibernator

Title
The effect of metabolic fuel availability on thermoregulation and torpor in a marsupial hibernator
Publication Date
2004
Author(s)
Westman, Wendy
Geiser, Fritz
( author )
OrcID: https://orcid.org/0000-0001-7621-5049
Email: fgeiser@une.edu.au
UNE Id une-id:fgeiser
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Springer
Place of publication
Germany
DOI
10.1007/s00360-003-0388-y
UNE publication id
une:3160
Abstract
The physiological signal for torpor initiation appears to be related to fuel availability. Studies on metabolic fuel inhibition in placental heterotherms show that glucose deprivation via the inhibitor 2-deoxy-D-glucose (2DG) initiates a torpor-like state, whereas fatty acid deprivation via mercaptoacetate (MA) does not. As previous studies using inhibitors were limited to quantifying body temperature in placentals, we investigated whether inhibition of glucose or fatty acids for cellular oxidation induces torpor in the marsupial hibernator 'Cercartetus nanus', and how the response of metabolic rate is related to body temperature. Glucoprivation initiated a torpor-like state in 'C. nanus', but animals had much higher minimum body temperatures and metabolic rates than those of torpid food-deprived animals and arousal rates were slower. Moreover, 2DG-treated animals were thermoregulating at ambient temperatures of 20 and 12°C, whereas food-deprived torpid animals were thermo-conforming. We suggest that glucoprivation reduces the hypothalamic body temperature set point, but only by about 8°C rather than the approximately 28°C during natural torpor. Reduced fatty acid availability via MA also induced a torpor-like state in some 'C. nanus', with physiological variables that did not differ from those of torpid food-deprived animals. We conclude that reduced glucose availability forms only part of the physiological trigger for torpor initiation in 'C. nanus'. Reduced fatty acid availability, unlike for placental heterotherms, may be an important cue for torpor initiation in 'C. nanus', perhaps because marsupials lack functional brown adipose tissue
Link
Citation
Journal of Comparative Physiology B, 174(1), p. 49-57
ISSN
1432-136X
0174-1578
Start page
49
End page
57

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