THE EFFECT OF DOSE AND COMPOSITION OF DIETARY BEEF ON MUSCLE PROTEIN ANABOLISM

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 背景资料： 许多人失去肌肉质量和力量，因为他们变老。可能导致这种损失的因素之一是饮食的变化。具体来说，老年人可能没有摄入足够的膳食蛋白质，或者他们摄入的蛋白质可能无法有效地被肌肉组织吸收。以前的研究已经检查了蛋白质补充剂和氨基酸对蛋白质合成和肌肉生长的影响，但是缺乏检查膳食蛋白质的常见来源（即，牛肉）对肌肉蛋白质合成的影响。 假设： 需要研究的具体假设是： 1. 在年轻人中，肌肉蛋白质合成对摄入的牛肉量有剂量反应。 2. 在老年人中，肌肉蛋白质合成对牛肉摄入的最大反应与年轻人相同，但次最大反应减弱。 3. 尽管蛋白质含量相似，但高脂肪（25%）牛肉的能量含量更高，比低脂肪（10%）牛肉更有效地刺激肌肉蛋白质合成。 4. 在年轻人和老年人摄入牛肉后，先前的运动会增强肌肉蛋白质的合成。 具体目标和程序（摘要）： 本研究的目的是测量摄入不同份量和脂肪含量的牛肉后，年轻人和老年人血浆氨基酸浓度和肌肉蛋白质合成的变化。 实验设计（总结）： 我们将研究总共90名健康男性和女性志愿者，年龄在20至50岁（年轻人）和60至85岁（老年人）之间。我们将使用已建立的技术，包括稳定同位素示踪方法，血液采样和肌肉活检，以测量血浆激素和氨基酸浓度和骨骼肌合成的变化。 意义（总结）： 我们建议调查代谢反应的一个实际的营养干预，将解决一些机制，有助于肌肉蛋白质合成和肌肉损失在衰老过程中。 该项目将直接影响到关于作为日常饮食一部分摄入的蛋白质的质量和数量的建议，并将提供关于年轻人和老年人运动与蛋白质摄入之间关系的新信息。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: Many individuals lose muscle mass and strength as they get older. One of the factors that may contribute to this loss is changes in the diet. Specifically, elderly individuals may not eat sufficient dietary protein or the protein they do eat may not be as efficiently assimilated into muscle tissue. Previous studies have examined the effect of protein supplements and amino acids on protein synthesis and muscle growth, but there is a lack of data examining the effect of common sources of dietary protein (i.e., beef) on muscle protein synthesis. Hypothesis: Specific hypotheses to be investigated are: 1. In the young, there is a dose response of muscle protein synthesis to the amount of beef ingested. 2. In the elderly, the maximal response of muscle protein synthesis to beef intake is the same as in young, but the submaximal response is diminished. 3. The greater energy content of high fat (25 %) beef will stimulate muscle protein synthesis more effectively than low fat (10 %) beef despite a similar protein content. 4. Prior exercise amplifies muscle protein synthesis following beef ingestion in both young and elderly. Specific Aims and Procedures (summary): The goal of this study is to measure changes in plasma concentrations of amino acids and muscle protein synthesis in young and elderly individuals following ingestion of beef differing in portion size and fat content. Experimental Design (summary): We will study a total of 90 healthy male and female volunteers between the ages of 20 and 50 (young) and 60 and 85 (elderly). We will use established techniques including stable isotope tracer methodology, blood sampling and muscle biopsies to measure changes in plasma hormone and amino acid concentrations and skeletal muscle synthesis. Significance (summary): We propose to investigate the metabolic response to a practical nutritional intervention that will address a number of the mechanisms contributing to muscle protein synthesis and muscle loss during aging. This project will have direct implications for recommendations concerning both the quality and quantity of protein ingested as part of a daily diet and will also provide new information on the relationship between exercise and protein ingestion in the young and elderly.