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Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups : metabolic rates, energy reserve utilization, and water fluxes
journal contribution
posted on 2009-11-01, 00:00 authored by D Verrier, R Groscolas, C Guinet, John ArnouldJohn ArnouldPhysiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups: metabolic rates, energy reserve utilization, and water fluxes. Am J Physiol Regul Integr Comp Physiol 297: R1582–R1592, 2009. First published September 23, 2009; doi:10.1152/ajpregu.90857.2008.— Surviving prolonged fasting requires various metabolic adaptations, such as energy and protein sparing, notably when animals are simultaneously engaged in energy-demanding processes such as growth. Due to the intermittent pattern of maternal attendance, subantarctic fur seal pups have to repeatedly endure exceptionally long fasting episodes throughout the 10-mo rearing period while preparing for nutritional independence. Their metabolic responses to natural prolonged fasting (33.4 ± 3.3 days) were investigated at 7 mo of age. Within 4–6 fasting days, pups shifted into a stage of metabolic economy characterized by a minimal rate of body mass loss (0.7%/day) and decreased resting metabolic rate (5.9 ± 0.1 ml O2 ·kg-1·day-1) that was only 10% above the level predicted for adult terrestrial mammals. Field metabolic rate (289 ± 10 kJ·kg-1 ·day-1) and water influx (7.9 ± 0.9 ml·kg-1 ·day-1) were also among the lowest reported for any young otariid, suggesting minimized energy allocation to behavioral activity and thermoregulation. Furthermore, lean tissue degradation was dramatically reduced. High initial adiposity (>48%) and predominant reliance on lipid catabolism likely contributed to the exceptional degree of protein sparing attained. Blood chemistry supported these findings and suggested utilization of alternative fuels, such as β-hydroxybutyrate and de novo synthesized glucose from fat-released glycerol. Regardless of sex and body condition, pups tended to adopt a convergent strategy of extreme energy and lean body mass conservation that appears highly adaptive for it allows some tissue growth during the repeated episodes of prolonged fasting they experience throughout their development.
History
Journal
The American journal of physiology - regulatory, integrative and comparative physiologyVolume
297Issue
5Pagination
1582 - 1592Publisher
American Physiological SocietyLocation
Bethesda, MDPublisher DOI
ISSN
0363-6119eISSN
1522-1490Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2005, American Physiological SocietyUsage metrics
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starvationmetabolic rate reductionprotein sparinglipid metabolismβ-hydroxybutyrateScience & TechnologyLife Sciences & BiomedicinePhysiologybeta-hydroxybutyrateNORTHERN ELEPHANT SEALBODY-COMPOSITION CHANGESAMSTERDAM ISLANDPROTEIN CATABOLISMPOSTWEANING FASTMIROUNGA-ANGUSTIROSTRISPROLONGED STARVATIONDEPRESSED METABOLISMCALLORHINUS-URSINUSMILK CONSUMPTION
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