Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups

Verrier, Delphine, Atkinson, Shannon, Guinet, Christophe, Groscolas, Rene and Arnould, John P. Y. 2012, Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups, American journal of physiology : regulatory, integrative and comparative physiology, vol. 302, no. 8, pp. R929-R940.

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Title Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups
Author(s) Verrier, Delphine
Atkinson, Shannon
Guinet, Christophe
Groscolas, Rene
Arnould, John P. Y.ORCID iD for Arnould, John P. Y. orcid.org/0000-0003-1124-9330
Journal name American journal of physiology : regulatory, integrative and comparative physiology
Volume number 302
Issue number 8
Start page R929
End page R940
Total pages 12
Publisher American Physiological Society
Place of publication Bethesda, Md.
Publication date 2012-04-15
ISSN 0363-6119
Keyword(s) starvation
thyroid hormones
Summary Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1–3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total L-thyroxine (T4) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T3); and moderately increased T4. The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.
Language eng
Field of Research 050211 Wildlife and Habitat Management
060201 Behavioural Ecology
060205 Marine and Estuarine Ecology (incl Marine Ichthyology)
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1 Refereed article in a scholarly journal
Copyright notice ©2012, American Physiological Society
Persistent URL http://hdl.handle.net/10536/DRO/DU:30049635

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