Publications (11)10.25 Total impact
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Dataset: Printable Data Tables from Champagne et al 2012
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Dataset: Phocid & Otarrid Lactation Strategies
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Dataset: Flux Method Figures
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Dataset: Phocid & Otariid Lactation Strategies
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Dataset: Rates of Glucose Production and Hypothesized Recycling Pathway
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Article: A profile of carbohydrate metabolites in the fasting northern elephant seal.
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ABSTRACT: Northern elephant seals endure prolonged periods of food deprivation at multiple life-history stages and simultaneous with energetically costly activities-including reproduction and development. Most mammals decrease their energy expenditure while fasting, with simultaneous reductions in gluconeogenesis and circulating glucose concentration. Paradoxically, elephant seals maintain high rates of both energy expenditure and gluconeogenesis, and high blood glucose concentrations throughout fasting. We therefore characterized the suite of changes that occur in carbohydrate metabolites during fasting in northern elephant seals. Using a broad-based metabolomics platform we investigated fasting during two states-lactation in adult females and the post-weaning developmental period in pups. A total of 227 metabolites were detected in seal plasma; 31 associated with carbohydrate metabolism were analyzed in the present study. Several compounds showed similar responses during lactation and the post-weaning fast (e.g. glycerol and mesaconate) whereas other compounds displayed quite different abundances between groups (e.g. citrate and pyruvate). This work found that, while the changes that occur with fasting were frequently similar in lactating females and developing pups, the relative abundance of compounds often varied markedly. These differences suggest that the metabolic strategies used to endure prolonged fasts are influenced by life-history or nutrient constraints.Comparative Biochemistry and Physiology Part D Genomics and Proteomics 03/2013; 8(2):141-151. · 1.72 Impact Factor -
Article: Gluconeogenesis is associated with high rates of tricarboxylic acid and pyruvate cycling in fasting northern elephant seals.
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ABSTRACT: Animals that endure prolonged periods of food deprivation preserve vital organ function by sparing protein from catabolism. Much of this protein sparing is achieved by reducing metabolic rate and suppressing gluconeogenesis while fasting. Northern elephant seals (Mirounga angustirostris) endure prolonged fasts of up to 3 mo at multiple life stages. During these fasts, elephant seals maintain high levels of activity and energy expenditure associated with breeding, reproduction, lactation, and development while maintaining rates of glucose production typical of a postabsorptive mammal. Therefore, we investigated how fasting elephant seals meet the requirements of glucose-dependent tissues while suppressing protein catabolism by measuring the contribution of glycogenolysis, glycerol, and phosphoenolpyruvate (PEP) to endogenous glucose production (EGP) during their natural 2-mo postweaning fast. Additionally, pathway flux rates associated with the tricarboxylic acid (TCA) cycle were measured specifically, flux through phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate cycling. The rate of glucose production decreased during the fast (F(1,13) = 5.7, P = 0.04) but remained similar to that of postabsorptive mammals. The fractional contributions of glycogen, glycerol, and PEP did not change with fasting; PEP was the primary gluconeogenic precursor and accounted for ∼95% of EGP. This large contribution of PEP to glucose production occurred without substantial protein loss. Fluxes through the TCA cycle, PEPCK, and pyruvate cycling were higher than reported in other species and were the most energetically costly component of hepatic carbohydrate metabolism. The active pyruvate recycling fluxes detected in elephant seals may serve to rectify gluconeogeneic PEP production during restricted anaplerotic inflow in these fasting-adapted animals.AJP Regulatory Integrative and Comparative Physiology 06/2012; 303(3):R340-52. · 3.34 Impact Factor -
Chapter: Fasting Physiology of the Pinnipeds
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ABSTRACT: 19.1 Introduction to Pinniped Foraging and Fasting Periods Pinnipeds forgo feeding opportunities when they voluntarily haul-out to breed or grow new pelage. The timing of haul-outs does not necessarily coincide with reduced prey availability in foraging areas; rather, haul-out patterns are dictated by endogenous rhythms or environmental factors. Thus, the fasting periods in pinnipeds are regular and predictable for individuals and tied to important life history events. Therefore, we usually refer to pinnipeds as ''fasting'' rather than ''starving'' (Castellini and Rea 1992; McCue 2010). Although environmental changes (e.g. El Niño events) can influence prey availability and periodically impose nutritional stress on pinnipeds (Crocker et al. 2006; Le Boeuf and Crocker 2005; Trillmich and Limberger 1985; Trites and Donnelly 2003). The rare com-bination of marine feeding with terrestrial breeding and pelage synthesis regularly requires that fasting occur simultaneously with energetically costly activities. This review describes the current understanding of the metabolic adjustments that occur in fasting pinnipeds under the constraint of competing nutrient demands.05/2012: pages 309 - 336; -
Article: Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods.
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ABSTRACT: Despite the importance of water-soluble vitamins to metabolism, there is limited knowledge of their serum availability in fasting wildlife. We evaluated changes in water-soluble vitamins in northern elephant seals, a species with an exceptional ability to withstand nutrient deprivation. We used a metabolomics approach to measure vitamins and associated metabolites under extended natural fasts for up to 7 weeks in free-ranging lactating or developing seals. Water-soluble vitamins were not detected with this metabolomics platform, but could be measured with standard assays. Concentrations of measured vitamins varied independently, but all were maintained at detectable levels over extended fasts, suggesting that defense of vitamin levels is a component of fasting adaptation in the seals. Metabolomics was not ideal for generating complete vitamin profiles in this species, but gave novel insights into vitamin metabolism by detecting key related metabolites. For example, niacin level reductions in lactating females were associated with significant reductions in precursors suggesting downregulation of the niacin synthetic pathway. The ability to detect individual vitamins using metabolomics may be impacted by the large number of novel compounds detected. Modifications to the analysis platforms and compound detection algorithms used in this study may be required for improving water-soluble vitamin detection in this and other novel wildlife systems.Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 02/2012; 161(2):114-21. · 2.20 Impact Factor -
Article: Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris).
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ABSTRACT: Northern elephant seals exhibit the rare strategy of fasting and lactating concomitantly. We investigated hormonal regulation of glucose clearance in northern elephant seals using glucose tolerance tests (GTT) performed early in lactation and again just prior to weaning. For comparison, identical measurements were made on separate females late in the molt fast. Serial blood samples were used to assess glucose clearance and hormone responses for 3 h post glucose injection. Plasma glucose remained elevated at the end of the sampling period in all groups. Glucose clearance rates were not significantly different among test groups. A significant insulin response was observed in early lactation, no significant response was observed late in lactation and an intermediate response was observed late in the molt fast. The insulin response to a glucose load decreased with adipose tissue proportions. Plasma glucagon decreased significantly following GTT in early and late lactation, although the magnitude of the depression was small in comparison to other species. Hypoinsulemia may be critical to facilitate net lipolysis late in lactation. Consistently low glucose clearance among test groups suggests insulin insensitivity within peripheral tissues. Glucagon suppression independent of insulin release suggests modification of the typical insulin-glucagon counter-regulation. These findings suggest that metabolic features of diabetic-like conditions may be adaptive in the context of long-term fasting.Journal of Experimental Biology 10/2008; 211(Pt 18):2943-9. · 3.00 Impact Factor -
Article: Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris) /
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ABSTRACT: Thesis (M.A.)--Sonoma State University, 2006. Includes bibliographical references (leaves 19-27)
Top co-authors
Top Journals
Institutions
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2013
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CSU Mentor
Long Beach, CA, USA
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2012
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University of California, Santa Cruz
- Department of Ecology & Evolutionary Biology
California, MD, USA
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2008–2012
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Sonoma State University
- Department of Biology
Rohnert Park, CA, USA
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