Meeting Abstract

P3.84  Monday, Jan. 6 15:30  Thermal acclimation affects the postprandial oxidation of exogenous nutrients in Siberian hamsters WOJCIECHOWSKI, M.S.*; VOIGT, C.C.; JEFIMOW, M.; MCCUE, M.D.; Nicolaus Copernicus Univ., Torun, Poland; Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany; Nicolaus Copernicus Univ., Torun, Poland; St. Mary’s University, San Antonio, Texas mwojc@umk.pl

During acclimatization to winter, changes in morphology and physiology combined with changes in diet may affect how animals use the nutrients they ingest. To experimentally verify this possibility, we studied how thermal acclimation affects the rates at which Siberian hamsters (Phodopus sungorus) oxidize different types of dietary nutrients. We conducted ¹³CO₂ breath-testing experiments on hamsters ¹³C-labeled glucose, leucine or palmitic acid tracers gavaged orally. We predicted that under cold stress (2 °C) hamsters previously acclimated to cold temperatures (10 °C) would have higher resting metabolic rate (RMR) and would oxidize a greater proportion of dietary fatty acids than animals acclimated to 21 °C. Both groups of hamsters were kept under long photoperiod. Hamsters acclimated for 3 weeks to cold and subjected to near-freezing temperatures for 3 hours exhibited thermal conductance and RMR higher by ~10% than control animals, and oxidized dietary palmitic acid more extensively during the postprandial phase than animals acclimated to 21 °C. This indicates that 14d acclimation to cold leads to the upregulation of the mechanisms of heat production, but it is not enough for the increase in the insulation. We conclude that cold acclimated hamsters were able to direct more exogenous resources toward thermoregulation than those acclimated to 21 °C and that indeed, the thermal history results in significant changes in the extent to which animals oxidize dietary nutrients during the postprandial period.