TISSUE SPECIFIC NUTRITIONAL ADAPTATIONS IN RENAL FAILURE

肾衰竭时的组织特异性营养适应

• 批准号: 6193595
• 负责人: S. Russ Price
• 金额: $ 31.05万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2004-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6193595
• 关键词: acidosis; aldehyde /ketone oxidoreductase; aminoacid metabolism; branched chain aminoacid; cell line; chronic renal failure; diabetes mellitus; enzyme activity; gel mobility shift assay; genetic promoter element; glucocorticoids; high performance liquid chromatography; hormone regulation /control mechanism; insulin; kidney metabolism; laboratory rat; liver metabolism; muscle metabolism; northern blottings; nuclear runoff assay; nutrition related tag; phosphatidylinositol 3 kinase; protein kinase; transfection; western blottings

The essential branched-chain amino acids (BCAA) play critical roles in maintaining normal protein homeostasis and they influence critical intracellular signaling pathways that regulate metabolic functions. In normal individuals, nutritional adaptations to a reduced dietary protein intake (e.g., fasting, a low protein diet prescription) decrease the irreversible degradation of BCAA. Catabolic conditions like chronic renal failure (CRF) or acute diabetes impair these adaptive responses that preserve protein mass, thus contributing to the loss of lean body mass. The goals of Dr. Price and colleagues are to understand the mechanisms that regulate the activity of branched-chain alpha-ketoacid dehydrogenase (BCKAD), the rate-limiting enzyme in BCAA degradation, in the major tissues where BCAA are catabolized, and to determine if there are common signals in different catabolic states that regulate BCKAD activity, and hence, BCAA levels. To address these goals, the investigators will evaluate three hypotheses: 1) Acidification and glucocorticoids influence transcription of BCKAD subunit genes through specific cis-acting response elements. The investigators will identify specific DNA promoter elements in the BCKAD E2 gene that confer responses to acidification and glucocorticoids. 2) Abnormalities in BCAA utilization in rats with CRF result from tissue-specific alterations in BCKAD activity at both genetic and biochemical levels. The investigators will define how CRF influences the activities of BCKAD and BCKAD kinase, a unique kinase that inhibits BCKAD activity, in muscle, liver and kidney in a well-established rat model. They will measure BCKAD activity, BCKAD subunit and kinase proteins and amounts of subunit and kinase mRNAs 3) Insulin modulates BCKAD and/or BCKAD activities in different tissues by a mechanism requiring the critical signaling enzyme phosphatidylinositol 3-kinase. The investigators will determine the biochemical mechanism(s) that increase BCKAD activity in rat muscle, liver and kidney in response to acute diabetes mellitus (i.e., insulin insufficiency) and then examine the signaling mechanisms by which insulin regulates BCKAD and BCKAD kinase in cultured L6 muscle cells. The investigators findings will define cellular mechanisms regulating BCAA degradation in uremia, acute diabetes and other catabolic conditions.

必需的支链氨基酸 (BCAA) 至关重要 维持正常蛋白质稳态的作用，它们影响关键 调节代谢功能的细胞内信号通路。正常情况下 个人对减少饮食蛋白质摄入量进行营养调整（例如， 禁食、低蛋白饮食处方）减少不可逆的降解 支链氨基酸。分解代谢疾病，如慢性肾衰竭 (CRF) 或急性肾衰竭 糖尿病会损害这些保留蛋白质质量的适应性反应，因此 导致去脂体重的损失。普莱斯博士的目标和 同事们将了解调节活动的机制 支链 α-酮酸脱氢酶 (BCKAD)，限速酶 在 BCAA 降解的过程中，在 BCAA 分解代谢的主要组织中， 确定不同分解代谢状态中是否存在共同信号 调节 BCKAD 活性，从而调节 BCAA 水平。为了实现这些目标， 研究人员将评估三个假设：1）酸化和 糖皮质激素通过特定的途径影响 BCKAD 亚基基因的转录 顺式作用反应元件。研究人员将鉴定特定的DNA BCKAD E2 基因中赋予酸化反应的启动子元件 和糖皮质激素。 2) CRF大鼠BCAA利用异常 是由于 BCKAD 活性在遗传和 生化水平。研究人员将定义 CRF 如何影响 BCKAD 和 BCKAD 激酶（一种抑制 BCKAD 的独特激酶）的活性 在成熟的大鼠模型中，肌肉、肝脏和肾脏的活性。他们 将测量 BCKAD 活性、BCKAD 亚基和激酶蛋白以及 BCKAD 的量 亚基和激酶 mRNA 3) 胰岛素调节 BCKAD 和/或 BCKAD 活性 不同的组织通过需要关键信号酶的机制 磷脂酰肌醇3-激酶。研究人员将确定生化指标 增加大鼠肌肉、肝脏和肾脏中 BCKAD 活性的机制 对急性糖尿病（即胰岛素不足）的反应，然后 检查胰岛素调节 BCKAD 和 BCKAD 的信号传导机制 培养的 L6 肌细胞中的激酶。研究人员的调查结果将定义 调节尿毒症、急性糖尿病和 BCAA 降解的细胞机制 其他分解代谢状况。