van Vliet Stephan, Beals Joseph W, Parel Justin T, Hanna Christina D, Utterback Pamela L, Dilger Anna C, Ulanov Alexander V, Li Zhong, Paluska Scott A, Moore Daniel R, Parsons Carl M, Burd Nicholas A
Department of Kinesiology and Community Health.
Division of Nutritional Sciences.
J Nutr. 2016 Jul;146(7):1428-33. doi: 10.3945/jn.115.228338. Epub 2016 Jun 8.
Stable isotope amino acids are regularly used as tracers to examine whole-body and muscle protein metabolism in humans. To accurately assess in vivo dietary protein digestion and absorption kinetics, the amino acid tracer is required to be incorporated within the dietary protein food source (i.e., intrinsically labeled protein).
We assessed the practicality of producing eggs and poultry meat intrinsically labeled with l-[5,5,5-(2)H3]leucine through noninvasive oral tracer administration.
A specifically formulated diet containing 0.52% leucine was supplemented with 0.3% l-[5,5,5-(2)H3]leucine and subsequently fed to 3 laying hens (Lohmann LSL Whites) for 55 d. On day 55, the hens were slaughtered and their meat, bones, and organs were harvested to determine tissue labeling. In Expt. 1, 2 healthy young men [mean ± SEM age: 22 ± 1.5 y; mean ± SEM body mass index (BMI; in kg/m(2)): 23.7 ± 0.5] ingested 18 g l-[5,5,5-(2)H3]leucine-labeled egg protein. In Expt. 2, 2 healthy young men (mean ± SEM age: 20.0 ± 0.0 y; mean ± SEM BMI: 26.4 ± 3.1) ingested 28 g l-[5,5,5-(2)H3]leucine-labeled poultry meat protein. Plasma samples (Expts. 1 and 2) and muscle biopsies (Expt. 1) were collected before and after labeled-food ingestion.
High tracer labeling [>20 mole percent excess (MPE)] in the eggs was obtained after 7 d and maintained throughout the feeding protocol (P < 0.05). Over a 55-d period, ∼850 g egg protein (145 eggs) was produced, with a mean ± SEM tracer enrichment of 22.0 ± 0.8 MPE. Mean ± SEM l-[5,5,5-(2)H3]leucine enrichment in the meat was 9.6 ± 0.1 MPE. In Expts. 1 and 2, the consumption of labeled eggs and poultry meat protein increased plasma l-[5,5,5-(2)H3]leucine enrichment, with mean ± SEM peak values of 6.7 ± 0.1 MPE and 4.0 ± 0.9 MPE, respectively. The mean ± SEM 5-h postprandial increase in myofibrillar l-[5,5,5-(2)H3]leucine enrichment after egg ingestion in healthy young men was 0.051 ± 0.008 MPE (Expt. 1).
We demonstrated the feasibility of producing intrinsically labeled eggs and poultry meat for use in human metabolic research.
稳定同位素氨基酸常被用作示踪剂，以研究人体全身和肌肉蛋白质代谢。为准确评估体内膳食蛋白质的消化和吸收动力学，氨基酸示踪剂需掺入膳食蛋白质食物来源中（即内源性标记蛋白质）。
我们评估了通过非侵入性口服示踪剂给药生产内源性标记有l-[5,5,5-(2)H3]亮氨酸的鸡蛋和禽肉的可行性。
一种特别配制的含0.52%亮氨酸的日粮补充了0.3%的l-[5,5,5-(2)H3]亮氨酸，随后喂给3只产蛋母鸡（罗曼LSL白羽鸡）55天。在第55天，宰杀母鸡并采集其肉、骨骼和器官以测定组织标记情况。在实验1中，2名健康年轻男性[平均±标准误年龄：22±1.5岁；平均±标准误体重指数（BMI；单位：kg/m²）：23.7±0.5]摄入了18克l-[5,5,5-(2)H3]亮氨酸标记的鸡蛋蛋白。在实验2中，2名健康年轻男性（平均±标准误年龄：20.0±0.0岁；平均±标准误BMI：26.4±3.1）摄入了28克l-[5,5,5-(2)H3]亮氨酸标记的禽肉蛋白。在摄入标记食物前后采集血浆样本（实验1和2）和肌肉活检样本（实验1）。
7天后鸡蛋中获得了高示踪剂标记[>20摩尔百分比过量（MPE）]，并在整个喂养方案期间保持（P<0.05）。在55天的时间里，生产了约850克鸡蛋蛋白（145个鸡蛋），示踪剂富集的平均值±标准误为22.0±0.8 MPE。肉中l-[5,5,5-(2)H3]亮氨酸富集的平均值±标准误为9.6±0.1 MPE。在实验1和2中，摄入标记鸡蛋和禽肉蛋白后血浆中l-[5,5,5-(2)H3]亮氨酸富集增加，平均值±标准误的峰值分别为6.7±0.1 MPE和4.0±0.9 MPE。健康年轻男性摄入鸡蛋后，餐后5小时肌原纤维中l-[5,5,5-(2)H3]亮氨酸富集的平均值±标准误增加0.051±0.008 MPE（实验1）。
我们证明了生产用于人体代谢研究的内源性标记鸡蛋和禽肉的可行性。
