Regulation of Protein Synthesis in Neonatal Sepsis

描述(由申请人提供)： 新生儿在疾病期间对营养耗竭的易感性，以及与之相反的有效利用营养生长的代谢能力，为评估脓毒症期间营养与激素的相互作用提供了一个新的范例。我们的长期目标是确定调节氨基酸使用的基本机制，包括激素、营养物质和发育之间的相互作用，在炎症条件下，如败血症。在这项建议中，我们打算分析调节败血症新生儿氨基酸代谢的途径。在目标1中，我们假设增加内毒素血症新生儿的氨基酸可以提高肌肉蛋白质的合成速率。因此，将使用激素底物钳制技术和同位素示踪法在体内测量蛋白质合成，对注射内毒素(LPS)的7日龄和26日龄猪进行氨基酸剂量反应研究。在目标2中，我们希望确定氨基酸是否影响内毒素注入的肌肉蛋白质的合成。 通过影响参与与40S核糖体复合体结合的mRNA而不是Met-tRNAi的翻译起始因子的激活来影响新生儿。因此，我们将检测肌肉真核细胞起始因子(ELF)2B的活性、eIF4E、4E-BP1、p70S6和蛋白激酶B(PKB)的磷酸化、eIF4E与eIF4G和4E-BP1的关联以及NFkappaB信号的激活。在目标3中，我们希望确定败血症是否会促进新生儿肌肉的蛋白质分解，以及注射胰岛素是否可以抑制蛋白质分解的速度。因此，将使用稳定的同位素示踪/质量跨器官平衡技术来检测注射了内毒素的7日龄和26日龄的猪在不同浓度的胰岛素存在下后肢的蛋白质降解情况。了解危重疾病期间的营养-激素界面及其发育特点，有助于确定和优化医疗管理的特点，以便在婴儿和儿童患重病后恢复和重建适当的生长。

DESCRIPTION (provided by applicant): The susceptibility of the neonate for nutritional depletion during illness, and its opposed metabolic ability to utilize nutrients efficiently for growth offers a novel paradigm to evaluate nutrient-hormonal interactions during sepsis. Our long-term objectives are to identify the fundamental mechanisms that regulate amino acid use, including the interaction of hormones, nutrients, and development, in inflammatory conditions such as sepsis. In this proposal, we intend to analyze the pathways that regulate amino acid metabolism in septic neonates. In Aim 1, we hypothesize that raising amino acids in endotoxemic neonates enhances muscle protein synthesis rates. Thus, amino acid dose response studies will be performed in endotoxin (LPS) infused 7- and 26-day-old pigs by using hormone-substrate clamp techniques and in vivo measurement of protein synthesis with isotopic tracer methods. In Aim 2, we wish to determine whether amino acids influence muscle protein synthesis in LPS-infused neonates by affecting activation of translation initiation factors involved in the binding of mRNA, but not met-tRNAi, to the 40S ribosomal complex. Consequently, we will measure in muscle eukaryotic initiation factor (elF) 2B activity, the phosphorylation of eIF4E, 4E-BP1, p70S6 kinase and protein kinase B (PKB), the association of eIF4E with eIF4G and 4E-BP1, and the activation of NFkappaB signaling. In Aim 3, we wish to determine whether muscle proteolysis is enhanced by sepsis in neonates and whether the rate of proteolysis can be suppressed by administration of insulin. Therefore, LPS-infused 7- and 26-day-old pigs subjected to hormone-substrate clamps will be examined using a stable isotopic tracer/mass transorgan balance technique to quantify protein degradation in the hindlimb in the presence of different concentrations of insulin. Knowledge of the nutrient-hormone interface during a critical illness and their developmental distinctiveness can help characterize and optimize the medical management towards recovery and reestablishment of adequate growth after infants and children have been acutely ill.