Dear colleagues, We are pleased to announce that a new publication on fasting endocrinology in fur seals is now available in American Journal of Physiology .
Delphine Verrier, Shannon Atkinson, Christophe Guinet, René Groscolas and John P. Y. Arnould. Hormonal responses to extreme fasting in subantarctic fur seal ( Arctocephalus tropicalis ) pups. Am J Physiol Regul Integr Comp Physiol 302:R929-R940, 2012. First published 8 February 2012; doi:10.1152/ajpregu.00370.2011 Abstract 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 (T(4)) 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 (T(3)); and moderately increased T(4). 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. Best wishes, Delphine -- Dr Delphine Verrier DVM, PhD Primate Centre and Ecology of Health Research Unit International Centre of Medical Research of Franceville (CIRMF) Po Box 769, Franceville, GABON Phone: +241 07 98 56 69 Email: d.verr...@cirmf.org or ddlafou...@free.fr Skype: ddlafouine1
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