DIETARY PROTEIN INTAKE AND PROTEIN METABOLISM

这项拨款申请将继续探索定量方面的 特定的、有条件的或必需的代谢 完整的健康成人的氨基酸。早期氮平衡 研究表明，九种氨基酸的营养不可或缺， 氨基酸，与其他常见的组织蛋白质氨基酸分类 作为一个分类不再令人满意，因为 营养和代谢知识的进步。它是假设 营养丰富的氨基酸的细胞利用率 满足生理需要的能力是由氮和氨基决定的 酸组成的饮食，并反过来影响的动态状态 组织和器官的蛋白质周转。独特的稳定同位素示踪剂 方法将被利用来量化体内方面的一些 这些氨基酸在明确定义的营养条件下。 具体而言，我们将（a）继续建立稳定的同位素示踪剂 研究代谢的定量方面的模型 特定的氨基酸，或条件必需氨基酸， 它们是（i）脯氨酸、精氨酸和鸟氨酸“三联体”;（ii）酪氨酸 (iii)胱氨酸（iv）甘氨酸和（v）谷氨酰胺;（B）探索 膳食总氮摄入量改变的后果 和/或特定氨基酸对上述氨基酸代谢的影响 酸，使用改进的稳定同位素探针和方法， （c）探讨各方面之间相互关系的动力学 选择的必需氨基酸（亮氨酸和苏氨酸）和 （d）确定是否 成年年龄的提前在应对艾滋病方面具有重要意义。 氨基酸代谢的一些饮食治疗和（e）检查 对肌肉蛋白质和氨基酸代谢的影响。拟议 将确定体内生理机制负责的变化 在特定氨基酸的代谢中起作用。较长期 本研究的目的是为了更全面地了解 关于“β”氨基酸的体内调节和整合 代谢和对氮的定量贡献 完整人类宿主的经济。从这一理解， 可以改进用于评估蛋白质的诊断工具， 氨基酸营养状况，一方面，营养 另一方面，人类主体在不同情况下的要求 病理生理条件。

This grant application is to continue exploring quantitative aspects of the metabolism of specific, conditionally indispensable or dispensable amino acids in the intact, health human adult. Earlier nitrogen balance studies demonstrated the nutritional indispensability of nine amino acids, with the other common amino acids of tissue proteins classified as being dispensable. The classification is no longer satisfactory as nutrition and metabolic knowledge has advanced. It is hypothesized that the cellular availability of the nutritionally dispensable amino acids for meeting physiologic needs is determined by the nitrogen and amino acid composition of the diet and in turn affected by the dynamic status of tissue and organ protein turnover. Unique stable isotope tracer approaches will be exploited to quantify in vivo aspects of some of these amino acids under well-defined nutritional conditions. Specifically we will (a) continue to establish stable isotope tracer models for investigating quantitative aspects of the metabolism of specific dispensable, or conditionally indispensable, amino acids - these are (i) the proline, arginine and ornithine "triad"; (ii) tyrosine (iii) cystine (iv) glycine and (v) glutamine; (b) explore the consequences of alterations in the dietary intake of total nitrogen and/or specific amino acids on the metabolism of the foregoing amino acids, using the improved stable isotope probes and approaches for this purpose; (c) explore the kinetics of the interrelationships between selected indispensable amino acids (leucine and threonine) and the dietary supply of dispensable amino acids; (d) determine whether advancing adult age is of importance in the responses of dispensable amino acid metabolism to some of the dietary treatments and (e) examine their effects on muscle protein and amino acid metabolism. The proposed will identify in vivo physiological mechanisms responsible for changes in the metabolism of specific dispensable amino acids. The longer-term objective of this research is to achieve a more complete understanding about the in vivo regulation and integration of "dispensable" amino acid metabolism and the quantitative contribution made to the nitrogen economy of the intact human host. From this understanding it will be possible to improve upon diagnostic tools taken to assess protein and amino acid nutritional status, on the one hand, and the nutritional requirements, on the other, of the human subject under differing pathophysiological conditions.