COMPARISON OF TWO METHODS FOR STUDYING PROTEIN METABOLISM IN HEALTHY ADULTS

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。体内全身蛋白质周转和氧化通常通过在羧基位置用13 C标记的氨基酸（例如，1- 13 C-亮氨酸）和呼吸13 CO2后静脉输注标记的氨基酸。虽然这种方法对成人和年龄较大的儿童足够无创，但通常认为这种方法对小早产儿的侵入性太大。因此，其用于研究该人群的蛋白质代谢受到限制。理论上，应该可以通过口服给予标记的氨基酸，并测量其在尿液中的富集和呼吸中13 CO2的富集。一些研究，一些在婴儿和成人中进行，表明这两种方法在血浆和尿液中的富集效果相似，但这两种技术的所有方面从未在同一个体中进行过比较。为了实现这一点，将对健康男性和非妊娠女性（年龄，18-40岁）进行两次研究。在第一种情况下，他们将接受1- 13 C-亮氨酸的初始恒定静脉输注或13 C-亮氨酸的初始间歇摄入。一周后，他们将通过替代途径接受相同剂量的1- 13 C-亮氨酸。将在两种情况下测定血浆和尿液中亮氨酸的富集和呼气13 CO2富集。这将允许比较常规方法（持续静脉给药和血浆采样）与微创方法（预充间歇肠内给药和尿液采样）以及两者的任何组合（静脉给药和尿液采样）。通量，蛋白质合成和蛋白质分解计算与两种方法获得的数据也将进行比较。所获得的数据将为研究全身蛋白质代谢提供这两种方法的第一次全面评估，以及是否可以用侵入性较小的方法取代侵入性常规方法。

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. In vivo whole body protein turnover and oxidation are usually measured by the plasma enrichment of an amino acid labeled in the carboxyl position with 13C (e.g., 1-13C-leucine) and breath 13CO2 following intravenous infusion of the labeled amino acid. While sufficiently non-invasive in adults and older children, this method is often considered too invasive for use in small preterm infants. Hence, its use to study protein metabolism of this population has been limited. In theory, it should be possible to administer the labeled amino acid by mouth and measure its enrichment in urine and the enrichment of 13CO2 in breath. A few studies, some in infants and some in adults, suggest that the two approaches result in similar enrichment in plasma and urine but all aspects of the two techniques have never been compared in the same individuals. To accomplish this, healthy men and non-pregnant women (age, 18-40 years) will be studied on two occasions. On the first, they will receive a primed constant intravenous infusion of 1-13C-leucine or a primed intermittent ingestion of 13C-leucine. A week later, they will receive the same dose of 1-13C-leucine by the alternative route. Plasma and urinary enrichments of leucine and breath 13CO2 enrichment will be determined on both occasions. This will permit comparison of the conventional method (constant intravenous administration and plasma sampling) with the less invasive method (primed intermittent enteral administration and urine sampling) as well as any combination of the two (intravenous administration and urine sampling). Flux, protein synthesis and protein breakdown calculated with data obtained by both approaches also will be compared. The data to be obtained will provide the first thorough evaluation of these two methods for studying whole body protein metabolism and whether the invasive conventional method can be replaced by the less invasive method.