Wolf Nathan, Newsome Seth D, Peters Jacob, Fogel Marilyn L
Fairweather Science LLC, Anchorage, AK, 99515, USA.
University of New Mexico, Department of Biology, Albuquerque, NM, 87131, USA.
Rapid Commun Mass Spectrom. 2015 Aug 15;29(15):1448-56. doi: 10.1002/rcm.7239.
The eco-physiological mechanisms that govern the incorporation and routing of macronutrients from dietary sources into consumer tissues determine the efficacy of stable isotope analysis (SIA) for studying animal foraging ecology. We document how changes in the relative amounts of dietary proteins and lipids affect the metabolic routing of these macronutrients and the consequent effects on tissue-specific discrimination factors in domestic mice using SIA. We also examine the effects of dietary macromolecular content on a commonly used methodological approach: lipid extraction of potential food sources.
We used carbon ((13) C) and nitrogen ((15) N) isotopes to examine the routing of carbon from dietary proteins and lipids that were used by mice to biosynthesize hair, blood, muscle, and liver. Growing mice were fed one of four diet treatments in which the total dietary content of C4 -based lipids (δ(13) C = -14.5‰) and C(3) -based proteins (δ(13) C = -27‰) varied inversely between 5% and 40%.
The δ(13) C values of mouse tissues increased by approximately 2-6‰ with increasing dietary lipid content. The difference in δ(13) C values between mouse tissues and bulk diet ranged from 0.1 ± 1.5‰ to 2.3 ± 0.6‰ for all diet treatments. The mean (±SD) difference between the δ(13) C values of mouse tissues and dietary protein varied systematically among tissues and ranged from 3.1 ± 0.1‰ to 4.5 ± 0.6‰ for low fat diets and from 5.4 ± 0.4‰ to 10.5 ± 7.3‰ for high fat diets.
Mice used some fraction of their dietary lipid carbon to synthesize tissue proteins, suggesting flexibility in the routing of dietary macromolecules to consumer tissues based on dietary macromolecular availability. Consequently, all constituent dietary macromolecules, not just protein, should be considered when determining the relationship between diets and consumer tissues using SIA. In addition, in cases where animals consume diets with high lipid contents, non lipid-extracted prey samples should be analyzed to estimate diets using SIA.
控制从饮食来源摄入的大量营养素进入消费者组织并在其中分配的生态生理机制，决定了稳定同位素分析（SIA）用于研究动物觅食生态学的有效性。我们记录了饮食中蛋白质和脂质相对含量的变化如何影响这些大量营养素的代谢分配，以及使用SIA对家鼠组织特异性歧视因子的后续影响。我们还研究了饮食大分子含量对一种常用方法的影响：潜在食物来源的脂质提取。
我们使用碳（¹³C）和氮（¹⁵N）同位素来研究小鼠用于生物合成毛发、血液、肌肉和肝脏的饮食蛋白质和脂质中的碳的分配情况。给生长中的小鼠喂食四种饮食处理之一，其中基于C4的脂质（δ¹³C = -14.5‰）和基于C3的蛋白质（δ¹³C = -27‰）的总饮食含量在5%至40%之间呈反比变化。
随着饮食脂质含量的增加，小鼠组织的δ¹³C值增加了约2 - 6‰。在所有饮食处理中，小鼠组织与整体饮食的δ¹³C值差异范围为0.1±1.5‰至2.3±0.6‰。小鼠组织与饮食蛋白质的δ¹³C值的平均（±标准差）差异在不同组织之间有系统变化，低脂饮食时范围为3.1±0.1‰至4.5±0.6‰，高脂饮食时范围为5.4±0.4‰至10.5±7.3‰。
小鼠利用其饮食脂质碳的一部分来合成组织蛋白质，这表明基于饮食大分子的可利用性，饮食大分子向消费者组织的分配具有灵活性。因此，在使用SIA确定饮食与消费者组织之间的关系时，应考虑所有组成饮食大分子，而不仅仅是蛋白质。此外，在动物食用高脂饮食的情况下，应分析未进行脂质提取的猎物样本以使用SIA估计饮食情况。
