Absence of adaptive nonshivering thermogenesis in a marsupial,the fat-tailed dunnart (<Emphasis Type="Italic">Sminthopsis crassicaudata</Emphasis>) |
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Authors: | E T Polymeropoulos M Jastroch P B Frappell |
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Institution: | (1) School of Zoology, University of Tasmania, Hobart, 7001, Australia;(2) Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA 94945, USA |
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Abstract: | The presence of nonshivering thermogenesis in marsupials is controversially debated. Survival of small eutherian species in
cold environments is crucially dependent on uncoupling protein 1 (UCP1)-mediated, adaptive nonshivering thermogenesis that
is executed in brown adipose tissue. In a small dasyurid marsupial species, the fat-tailed dunnart (Sminthopsis crassicaudata), an orthologue of UCP1 has been recently identified which is upregulated during cold exposure resembling adaptive molecular
adjustments of eutherian brown adipose tissue. Here, we tested for a thermogenic function of marsupial brown adipose tissue
and UCP1 by evaluating the capacity of nonshivering thermogenesis in cold-acclimated dunnarts. In response to an optimal dosage
of noradrenaline, cold-acclimated dunnarts (12°C) showed no additional recruitment of noradrenaline-induced maximal thermogenic
capacity in comparison to warm-acclimated dunnarts (24°C). While no differences in body temperature were observed between
the acclimation groups, basal metabolic rate was significantly elevated after cold acclimation. Therefore, we suggest that
adaptive nonshivering thermogenesis does not occur in this marsupial species despite the cold recruitment of oxidative capacity
and UCP1 in the interscapular fat deposit. In conclusion, the ancient UCP orthologue in marsupials does not contribute to
the classical nonshivering thermogenesis, and may exhibit a different physiological role. |
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