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Trixie Pittman, Ph.D.
Article
Lee et al. 2017- Stable isotope analysis of CO2 in breath indicates metabolic fuel shifts in torpid arctic ground squirrels.pdf
Comparative Biochemistry and Physiology, Part A (2017)
  • Trixie N Lee, Harding University
  • Melanie M Richter, University of Alaska, Anchorage
  • Cory T Williams, University of Alaska, Fairbanks
  • Oivind Toien, University of Alaska, Fairbanks
  • Brian M Barnes, University of Alaska, Fairbanks
  • Diane M O'Brien, University of Alaska, Fairbanks
  • C. Loren Buck, University of Alaska, Anchorage
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Abstract
Stable carbon isotope ratios (δ13C) in breath show promise as an indicator of immediate metabolic fuel
utilization in animals because tissue lipids have a lower δ13C value than carbohydrates and proteins. Metabolic
fuel consumption is often estimated using the respiratory exchange ratio (RER), which has lipid and
carbohydrate boundaries, but does not differentiate between protein and mixed fuel catabolism at intermediate
values. Because lipids have relatively low δ13C values, measurements of stable carbon isotopes in breath may
help distinguish between catabolism of protein and mixed fuel that includes lipid. We measured breath δ13C and
RER concurrently in arctic ground squirrels (Urocitellus parryii) during steady-state torpor at ambient
temperatures from −2 to −26 °C. As predicted, we found a correlation between RER and breath δ13C values;
however, the range of RER in this study did not reach intermediate levels to allow further resolution of metabolic
substrate use with the addition of breath δ13C measurements. These data suggest that breath δ13C values are
1.1‰ lower than lipid tissue during pure lipid metabolism. From RER, we determined that arctic ground
squirrels rely on nonlipid fuel sources for a significant portion of energy during torpor (up to 37%). The shift
toward nonlipid fuel sources may be influenced by adiposity of the animals in addition to thermal challenge.
Keywords
  • Arctic ground squirrel,
  • Breath carbon isotope,
  • hibernation,
  • metabolic fuel,
  • stable isotopes
Disciplines
Publication Date
2017
DOI
10.1016/j.cbpa.2017.04.004
Citation Information
Trixie N Lee, Melanie M Richter, Cory T Williams, Oivind Toien, et al.. "Lee et al. 2017- Stable isotope analysis of CO2 in breath indicates metabolic fuel shifts in torpid arctic ground squirrels.pdf" Comparative Biochemistry and Physiology, Part A Vol. 209 (2017) p. 10 - 15
Available at: http://works.bepress.com/tnlee/1/