Meeting Abstract
S9.1-3 Tuesday, Jan. 7 08:40 Bulk tissue and amino acid δ13C analysis shows that mice can use dietary lipids to build proteinaceous tissues NEWSOME, Seth D.*; WOLF, Nathan; FOGEL, Marilyn L.; University of New Mexico; University of Alaska–Anchorage; University of California–Merced newsome@unm.edu
Understanding the mechanisms that govern the incorporation and routing of macronutrients from dietary sources into consumer tissues is a fundamental question in animal eco-physiology. Not only do these mechanisms play a potential role in influencing the selection and use of dietary items by consumers, but, in addition, these processes also determine the efficacy of techniques such as stable isotope analysis for studying animal ecology. By feeding growing mice (Mus musculus) one of four diet treatments in which the total dietary content of C4-based lipids and C3-based proteins varied inversely between 5% and 40%, we were able to examine the relationship between dietary proteins and lipids and mouse hair, blood, muscle, and liver. The difference in δ13C between mouse tissues and dietary protein, or trophic discrimination factor, varied systematically among tissues and ranged from 3.1±0.1‰ to 4.5±0.6‰ (mean±SD) for low fat diets and 5.4±0.4‰ to 10.5±7.3‰ for high fat diets. In contrast, the difference in δ13C between mouse tissues and bulk diet that had not been lipid extracted prior to isotope analysis ranged from 0.1±1.5‰ to 2.3±0.6‰ for all diet treatments. This pattern suggests flexibility in the routing of dietary macromolecules to consumer tissues based on dietary availability. We also analyzed the δ13C composition of individual amino acids in mice muscle to determine the ultimate source of carbon in both essential and non-essential amino acids. Amino acid analysis shows that dietary lipid carbon is being used to synthesize non-essential amino acids. The δ13C of essential amino acids did not change among dietary treatments showing that they are routed directly from dietary protein.
