Meeting Abstract

P2.25  Sunday, Jan. 5 15:30  Targeted ¹³C enrichment of lipid and protein pools in the body reveals circadian changes in oxidative fuel mixture during prolonged fasting: a case study using Japanese quail AMAYA, J; YANG, A*; WOLF, B/O; MCCUE, M/D; St. Mary’s University; St. Mary’s University; University of New Mexico; St. Mary’s University mmccue1@stmarytx.edu

Many animals undergo extended periods of fasting during their annual cycle. During these fasts, animals use a mix of macronutrients related to the nutritional, energetic, or hydric requirements of the fasting period. The use of specific macronutrients can vary widely with the time course and duration of the fast. In this study, we use Japanese quail, a bird with natural intermediate fasting periods, to examine macronutrient use during a six day fast. We raised quail on isotopically labeled materials (¹³C-1-leucine, ¹³C-U-glucose, or ¹³C-1-palmitic acid) with the intent of labeling specific macronutrient/tissue pools in each treatment, and then traced their use as a fuel by measuring the δ¹³C values breath CO₂. Based on changes in δ¹³C values during the fast, it appears that the carbohydrate label, ¹³C-U-glucose, was largely incorporated into the lipid pool and thus breath samples ultimately reflected lipid use rather then carbohydrate use in this treatment. In the lipid treatment, ¹³C-1-palmitic acid, faithfully labeled the lipid pool and was reflected in the kinetics δ¹³C values in breath CO₂ during the fast. The protein label, ¹³C-1-leucine, showed apparent diurnal periods of protein sparing and use, with the use occurring, we hypothesize, during periods of relatively high metabolic demand. This labeling/breath tracer method provides a relatively noninvasive approach to studying the nutrient dynamics of fasting animals and should provide new insights into how different taxa use specific nutrient pools during short and long-term fasts.