Protection against renal ischemic injury by short term dietary restriction

描述(申请人提供)：饮食限制(DR)的定义是在不营养不良的情况下减少食物消耗，并延长酵母、蛔虫、果蝇和哺乳动物等各种生物的寿命。DR的一个特征不是很好但可能更切实的好处是提高了对应激的抵抗力，包括对哺乳动物各种器官的缺血再灌注损伤。目前还不存在DR的临床应用，因为难以坚持限制饮食，而且人们认为需要长时间的DR才能获得切实的好处。我们最近已经证明，短期的DR对小鼠肾脏缺血再灌注损伤具有显著的保护作用[8]。急性肾缺血损伤是临床上发病率和死亡率的主要原因。针对缺血损伤的预适应的概念已经确立，但通过短暂的饮食干预来做到这一点的能力是新的。我们将对缺血再灌注损伤有效的短期营养干预统称为“饮食预适应”。小鼠的有效方案包括2-4周减少30%的食物摄入量，3天只禁食水，1-2周在没有能量限制的情况下进行分离蛋白或必需氨基酸缺乏。在这里，我们建议阐明小鼠饮食预适应的营养触发因素、营养感应器和下游效应因子。鉴于我们发现，即使移除单一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的GCN2基因敲除小鼠来测试主要氨基酸传感器GCN2的需求。我们还将测试通过转录图谱确定的细胞保护基因上调的要求。最后，我们将检验这一假设，即在代谢转变为脂肪氧化过程中产生的过量ROS是上调细胞保护基因表达所必需的。我们期望确定这种新形式的预适应对小鼠肾脏缺血再灌注损伤的营养需求和下游效应。我们还希望鉴定出第一个哺乳动物基因，用于抵抗急性应激。我们的长期目标是开发简单的营养干预措施，在临床上使身体不受急性应激的影响。这样的临床应用包括在器官移植和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.