Protection against renal ischemic injury by short term dietary restriction

描述（由申请人提供）：饮食限制（DR）被定义为在没有营养不良的情况下减少食物消耗，并延长酵母菌、蛔虫、果蝇和哺乳动物等多种生物的寿命。DR的一个不太明确但可能更明显的益处是增强对应激的抵抗力，包括对哺乳动物各种器官的缺血再灌注损伤。目前没有DR的临床应用，因为很难坚持限制性饮食，再加上人们认为需要长时间的DR才能获得切实的好处。我们最近的研究表明，短时间的DR对小鼠肾缺血再灌注损伤具有显著的保护作用。急性肾缺血损伤是临床上发病率和死亡率的主要原因。预适应对抗缺血性损伤的概念已经确立，但通过简短的饮食干预来做到这一点的能力是新颖的。我们将对缺血再灌注损伤有疗效的短期营养干预统称为“饮食预处理”。小鼠的有效方案包括2-4周减少30%的食物，3天只禁食水，1-2周在没有能量限制的情况下缺乏分离蛋白质或必需氨基酸。在这里，我们建议阐明小鼠饮食预处理的营养触发因素、营养传感器和下游效应。鉴于我们的发现，即使去除单个必需氨基酸也能激活强大的保护，我们将使用全身和肾脏特异性GCN2敲除小鼠来测试对主要氨基酸传感器GCN2的需求。我们还将测试通过转录谱鉴定的细胞保护基因上调的需求。最后，我们将验证在向脂肪氧化的代谢转变过程中产生的过量ROS是细胞保护基因表达上调所必需的假设。我们期望确定营养需求和下游效应的这种新形式的预处理对抗肾缺血再灌注损伤的小鼠。我们也希望通过博士鉴定出第一个哺乳动物急性应激抵抗所需的基因。我们的长期目标是开发出简短的营养干预措施，使身体在临床中抵抗急性应激。这些临床应用包括器官移植、心血管手术等许多外科手术中不可避免的缺血再灌注损伤。

DESCRIPTION (provided by applicant): Dietary restriction (DR) is defined as reduced food consumption without malnutrition and extends lifespan in organisms as diverse as yeast, roundworms, fruit flies and mammals. A less-well characterized but potentially more tangible benefit of DR is increased resistance to stress, including ischemia reperfusion injury to various organs in mammals. Currently no clinical applications of DR exist due to difficulty in adherence to restricted diets combined with the perception that long periods of DR are required for tangible benefits. We have recently shown that brief periods of DR lend significant protection against renal ischemia reperfusion injury in mice [8]. Acute renal injury due to ischemia is a major cause of morbidity and mortality in the clinic. The concept of preconditioning against ischemic damage is well-established, but the ability to do so by brief dietary intervention is novel. We refer collectively to short-term nutritional interventions with efficacy against ischemia reperfusion injury as "dietary preconditioning". Effective regimens in mice include 2-4 weeks of 30% food reduction, 3 days of water-only fasting, and 1-2 weeks of isolated protein or essential amino acid deficiency in the absence of energy restriction. Here we propose to elucidate the nutritional triggers, nutrient sensors, and downstream effectors of dietary preconditioning in mice. In light of our finding that removal of even a single essential amino acid activated robust protection, we will test the requirement for the major amino acid sensor GCN2 using whole-body and kidney-specific GCN2 knockout mice. We will also test the requirement for upregulation of cytoprotective genes identified by transcriptional profiling. Finally, we will test the hypothesis that excess ROS generated during the metabolic shift to fat oxidation are required for upregulation of cytoprotective gene expression. We expect to identify nutritional requirements and downstream effectors of this novel form of preconditioning against renal ischemia reperfusion injury in mice. We also hope to identify the first mammalian gene required for acute stress resistance by DR. Our long-term goal is to develop brief nutritional interventions to precondition the body against acute stress in the clinic. Such clinical applications include ischemia reperfusion injury unavoidably incurred in a number of surgical procedures such as organ transplantation and cardiovascular surgery. PUBLIC HEALTH RELEVANCE: Dietary restriction (DR) has beneficial effects on metabolism and physiology in humans but is absent from clinical medicine because of notoriously low voluntary compliance rates. Our preliminary data demonstrate that the onset of benefits in mammals actually occurs quite rapidly - within days. Here we test the ability of short-term DR regimens to increase resistance to acute surgical stress in mice with the goal of moving rapid DR benefits to the clinic.