NUTRITIONAL IMPLICATIONS OF SITE OF FEEDING ON LEUCINE

从胃肠道（GI）吸收后， 在门循环中，营养物质首先受到 肝脏和胃肠道的代谢过程。 取决于 这些过程的速度和程度， 肠内施用营养物可以被吸收和利用 只在这些器官中。 这被称为第一遍 代谢（FP）。 除了代谢过程中， 内脏床，FP可能受混合率的影响 体循环和门静脉室 由于FP 代谢、肠内喂养和静脉营养 给药可能导致不同的代谢结果， 内脏和外周组织。 最近的证据表明，FP代谢的外源性 亮氨酸在进食过程中增加。 我们假设， 代表在肠内喂养期间亮氨酸的更高可用性 与肠胃外喂养相比。 拟议的工作将 关注这一现象，强调不同水平的饮食 亮氨酸摄入量 大鼠模型，采用多个13-C和14-C 示踪剂输注也将用于定量总FP 作为FP氧化和转氨作用形成α-酮异己酸 （KIC）. 肠内亮氨酸的选择性利用 还将测量胃肠道和肝脏蛋白质合成 在不同的摄入水平。 标签之间的关系 与血浆相比，呼出气中的CO2出现 亮氨酸和KIC富集，随后同时示踪 输注至系统循环、胃肠道和门静脉 将研究流通。 这些研究将扩展到烧伤大鼠模型， 高代谢状态下FP亮氨酸代谢的评价 条件 血液流速的测量将允许 计算全身亮氨酸在组织中的分布。 同时，蛋白质合成和降解速率，以及 肠内给药亮氨酸示踪剂的分布速率 将被衡量。 通过将FP亮氨酸代谢与 外源性亮氨酸的可用性（肠内和胃肠外）， 随着内脏蛋白质的合成和分解，我们将测试 假设营养管理途径影响 在压力增加的需求下的营养需求。

Following absorption from the gastrointestinal (GI) tract and transport in the protal circulation, nutrients are firs influenced by metabolic processes in the liver and GI tract. Depending upon the rate and extent of these processes, a certain fraction of the enterally administered nutrient may be taken up and utilized exclusively in these organs. This is referred to as first-pass metabolism (FP). In addition to metabolic processes in the splanchnic bed, FP may be influenced by the rate of intermixing of the systemic and portal compartments. As a result of FP metabolism, enteral feeding and intravenous nutrition administration may lead to different metabolic consequences in visceral and peripheral tissues. Recent evidence indicates that FP metabolism of exogenous leucine increases during feeding. We postulate that this represents a higher availability of leucine during enteral feeding in comparison to parenteral feeding. The proposed work will focus on this phenomenon, emphasizing varying levels of dietary leucine intake. A rat model, employing multiple 13-C and 14-C tracer infusions, will be used for quantification of total FP as well as FP oxidation and transamination into alpha-ketoisocaproate (KIC). The selective utilization of enteral leucine in gastrointestinal and liver protein synthesis will also be measured at different levels of intake. The relationship between labelled CO2 appearance in expired breath in comparison to plasma leucine and KIC enrichment, following simultaneous tracer infusions into the system circulation, the GI tract, and the portal circulation will be studied. These studies will be extended into a burned rat model for evaluation of FP leucine metabolism under hypermetabolic conditions. Measurement of blood flow rates will allow calculation of distribution of systemic leucine to tissues. Simultaneously, protein synthesis and degradation rates, as well as the rate of distribution of enterally administered leucine tracer will be measured. By correlating FP leucine metabolism and availability of exogenous leucine (both enteral and parenteral), with splanchnic protein synthesis and breakdown, we will test the hypothesis that the route of nutritional administration affects nutrient requirements under the increased demands of stress.