两种稳定同位素标记氨基酸测量人体蛋白质需要量的比较

目的探讨同时口服给予两种示踪剂1-13C-亮氨酸和α-15N-赖氨酸测量人体蛋白质需要量,结果是否一致。方法选取20名健康青年女性作为研究对象,预设6个膳食蛋白质水平,3个连续的实验周期,在每个实验周期给予日常膳食6d,在D7持续口服13C-亮氨酸和15N-赖氨酸4h,收集给予同位素过程中的静脉血、呼出气和尿液样本。测定血浆、呼出气和尿液中的13C、15N的丰度,计算13C-亮氨酸和15N-赖氨酸的氧化率,建立二项回归曲线计算蛋白质的需要量。结果通过13C-亮氨酸计算的蛋白质需要量是0.92 g/kg/d,无法通过15N-赖氨酸的氧化率建立二项回归曲线求得蛋白质需要量。结论口服途径以15N-赖氨酸作为示踪剂,不能较好的反映蛋白质摄入量的变化情况。

COMPARISON OF THE STUDY ABOUT HUMAN PROTEIN REQUIREMENT THROUGH TWO STABLE ISOTOPE LABELLED AMINO ACIDS

Objective To compare the study of human protein requirement using oral route with two stable isotope labelled amino acids 1-13C-leucine and α-15N-lysine at the same time.Method Twenty healthy Chinese young women participated in the experiment.There were six dietary protein levels and three consecutive periods.In each period,subjects consumed the experimental diets on D1 to D6,and were given 13C-leucine and 15N-lysine oral dose on D7 for 4h to trace the metabolism of the amino acids in body.Blood,breath and urine samples were collected and enrichments of 13C and 15N in samples were detected.Oxidation rates of 13C and 15N were calculated and breakpoint analysis using a two-phase linear crossover model was used to calculate protein requirement.Results The protein requirement was 0.92 g/kg/d from the oxidation of 13C-leucine,but could not be obtained from the oxidation rate of 15N-lysine.Conclusion As an indicator amino acid,the protein requirement was 0.92 g/kg/d from 13C-Leu study,but lysine couldn't respond to the changes of protein intake levels.