DIETARY PROTEIN INTAKE & HUMAN PROTEIN METABOLISM

这项拨款申请将继续探索量化方面的问题 特定的、有条件地不可或缺或可有可无的新陈代谢 完整、健康的成人体内的氨基酸。早期氮素平衡 研究表明，九种氨基酸是营养不可缺少的 酸，与组织蛋白的其他常见氨基酸一起归类 都是可有可无的。分类不再令人满意，因为 营养和新陈代谢知识已经进步。据推测， 营养必需氨基酸的细胞可利用性 以满足生理需要由氮和氨基决定 饮食中的酸组成，进而受动态状态的影响 组织和器官蛋白质的周转率。独特的稳定同位素示踪剂 将利用方法来量化体内某些方面的 这些氨基酸在明确的营养条件下。 具体来说，我们将(A)继续建立稳定的同位素示踪剂 研究新陈代谢的定量方面的模型 特定的可有可无的或有条件不可缺少的氨基酸- 它们是(I)脯氨酸、精氨酸和鸟氨酸“三联体”；(Ii)酪氨酸 (三)胱氨酸(四)甘氨酸和(五)谷氨酰胺；。(二)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 目的；(C)探讨相互关系的动力学 精选的必需氨基酸(亮氨酸和苏氨酸)和 膳食供应；(D)确定是否 在可有可无的反应中，提高成年年龄是重要的 氨基酸代谢的一些饮食处理和(E)检查 它们对肌肉蛋白质和氨基酸代谢的影响。建议数 将在体内确定导致变化的生理机制 在特定的非必需氨基酸的新陈代谢中。更长期的 本研究的目的是为了更全面地了解 关于“非必需”氨基酸在体内的调节和整合 代谢及其对氮素的数量贡献 完好无损的人类宿主的经济。根据这一理解，它将是 有可能改进用于评估蛋白质和 氨基酸的营养状况，一方面，和营养 另一方面，在不同的条件下，对人类主体的要求 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.