van der Wielen Nikkie, de Vries Sonja, Gerrits Walter J, Lammers-Jannink Kim, Moughan Paul J, Mensink Marco, Hendriks Wouter
Animal Nutrition Group, Wageningen University and Research, Wageningen, the Netherlands; Division of Human Nutrition, Wageningen University and Research, Wageningen, the Netherlands.
Animal Nutrition Group, Wageningen University and Research, Wageningen, the Netherlands.
J Nutr. 2023 Mar;153(3):673-682. doi: 10.1016/j.tjnut.2023.01.038. Epub 2023 Feb 9.
Unabsorbed free amino acids (AAs) at the end of the small intestine result in a potential preventable nutritional loss.
This study aimed to quantify free AAs in terminal ileal digesta of both humans and pigs to investigate its relevance for the nutritional value of food proteins.
Two studies with three diets were performed: a human study-ileal digesta from eight adult ileostomates were collected over 9 h after ingestion of a single meal unsupplemented or supplemented with 30 g zein or whey; pig study-12 cannulated pigs were fed for 7 d with a diet containing whey or zein or no-protein diet, and ileal digesta were collected on the last 2 d. Digesta were analyzed for total and 13 free AAs. True ileal digestibility (TID) of AAs was compared with and without free AAs.
All terminal ileal digesta samples contained free AAs. The TID of AAs in whey was 97% ± 2.4% (mean ± SD) in human ileostomates and 97% ± 1.9% in growing pigs. If the analyzed free AAs would have been absorbed, TID of whey would increase by 0.4%-units in humans and 0.1%-units in pigs. The TID of AAs in zein was 70% ± 16.4% in humans and 77% ± 20.6% in pigs and would increase by 2.3%-units and 3.5%-units, respectively, if the analyzed free AAs would have been fully absorbed. The largest difference was observed for threonine from zein: if free threonine was absorbed, the TID would increase by 6.6%-units in both species (P < 0.05).
Free AAs are present at the end of the small intestine and can potentially have a nutritionally relevant effect for poorly digestible protein sources, whereas the effect is negligible for highly digestible protein sources. This result provides insight into the room for improvement of a protein's nutritional value if all free AAs are to be absorbed. J Nutr 2023;xx:xx-xx. This trial was registered at clinicaltrials.gov as NCT04207372.
小肠末端未被吸收的游离氨基酸（AAs）会导致潜在的可预防的营养损失。
本研究旨在量化人类和猪的回肠末端食糜中的游离氨基酸，以研究其与食物蛋白质营养价值的相关性。
进行了两项研究，采用三种饮食：一项人体研究——在8名成年回肠造口者摄入一顿未补充或补充30 g玉米醇溶蛋白或乳清的单餐后9小时内收集回肠食糜；猪研究——12头插管猪分别饲喂含乳清或玉米醇溶蛋白的日粮或无蛋白日粮7天，并在最后2天收集回肠食糜。分析食糜中的总氨基酸和13种游离氨基酸。比较了有和没有游离氨基酸时氨基酸的真回肠消化率（TID）。
所有回肠末端食糜样本均含有游离氨基酸。在人体回肠造口者中，乳清中氨基酸的TID为97%±2.4%（平均值±标准差），在生长猪中为97%±1.9%。如果分析的游离氨基酸被吸收，乳清的TID在人类中会增加0.4个百分点，在猪中会增加0.1个百分点。玉米醇溶蛋白中氨基酸的TID在人类中为70%±16.4%，在猪中为77%±20.6%，如果分析的游离氨基酸被完全吸收，TID将分别增加2.3个百分点和3.5个百分点。玉米醇溶蛋白中的苏氨酸差异最大：如果游离苏氨酸被吸收，两种动物的TID将增加6.6个百分点（P<0.05）。
游离氨基酸存在于小肠末端，对难消化的蛋白质来源可能具有营养相关作用，而对易消化的蛋白质来源影响可忽略不计。该结果为如果所有游离氨基酸都被吸收时蛋白质营养价值的改善空间提供了见解。《营养学杂志》2023年；xx:xx - xx。本试验在clinicaltrials.gov上注册为NCT04207372。
