Department of Geriatrics, Center for Translational Research in Aging & Longevity, Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
Department of Molecular Medicine, College of Medicine, Gachon University, Incheon, Korea.
Exp Mol Med. 2022 Sep;54(9):1323-1331. doi: 10.1038/s12276-022-00817-w. Epub 2022 Sep 8.
There is a general consensus that a dietary protein intake of 0.8 g protein/kg/day will prevent symptoms of protein deficiency in young, healthy individuals. However, individuals in many physiological circumstances may benefit from higher rates of dietary protein intake. Stable isotope tracer methodology enables a variety of approaches to assessing the optimal dietary protein intake in humans. In this paper, we present an overview of a variety of tracer methods, with a discussion of necessary assumptions, as well as the clinical circumstances in which different methods may be preferable. Although we discuss the nontracer method of nitrogen balance, which has historically been used to estimate dietary protein requirements, this paper primarily focuses on tracer methods for estimating dietary protein and essential amino acid requirements under different physiological conditions. We will explain the following approaches: isotopic measurement of urea production; the arterial-venous tracer balance method; measurement of the fractional synthetic and breakdown rates of muscle protein; the indicator and the direct amino acid oxidation methods; and different approaches to measuring whole-body protein synthesis and breakdown. The advantages and limitations of each method are discussed in the context of the optimal approaches for use under different circumstances.
人们普遍认为，每天每公斤体重摄入 0.8 克蛋白质可预防年轻健康个体出现蛋白质缺乏症状。然而，许多生理情况下的个体可能受益于更高的膳食蛋白质摄入量。稳定同位素示踪剂方法可用于评估人类最佳膳食蛋白质摄入量的各种方法。在本文中，我们介绍了各种示踪剂方法的概述，并讨论了必要的假设，以及不同方法可能更适用的临床情况。虽然我们讨论了氮平衡的非示踪剂方法，该方法历史上曾用于估计膳食蛋白质需求，但本文主要侧重于在不同生理条件下估计膳食蛋白质和必需氨基酸需求的示踪剂方法。我们将解释以下方法：尿素生成的同位素测量；动静脉示踪剂平衡法；肌肉蛋白质合成和分解率的测定；指示剂和直接氨基酸氧化法；以及测量全身蛋白质合成和分解的不同方法。在不同情况下使用的最佳方法的背景下，讨论了每种方法的优缺点。
