A novel role for endogenous fructose in ischemic acute kidney injury

描述（由申请人提供）：急性肾损伤是住院的常见原因，影响30%入住重症监护室的患者的高死亡率。经过几十年的重要发现，其病理生理学，没有临床适用的治疗，以加速肾脏恢复急性肾损伤已经出现。多元醇途径是由醛糖还原酶和山梨醇脱氢酶两种酶组成的代谢途径。醛糖还原酶将葡萄糖转化为山梨糖醇，而山梨糖醇脱氢酶将山梨糖醇代谢为果糖。我们在患有缺血性急性肾损伤的小鼠中的初步数据表明，如通过高水平的醛糖还原酶和果糖积累（内源性果糖）所指出的，在肾皮质中存在多元醇途径的显著激活。我们发表的数据表明，在肾脏中，果糖激酶代谢果糖导致ATP耗竭，尿酸和氧化剂的产生，引起急性肾小管间质损伤。这些观察结果导致本申请的总体假设，即缺血性急性肾损伤激活多元醇途径和果糖激酶，这有助于近端小管细胞死亡。这一建议的意义在于，由于抑制剂（依帕司他、雷尼司他）的可用性，在急性肾损伤患者中抑制多元醇途径是可行的。该建议的创新之处在于，内源性果糖和肾果糖激酶在缺血性急性肾损伤中的作用从未被考虑过。研究多元醇途径和内源性果糖产生和代谢的有害作用的研究设计将涉及以下表征：1）多元醇途径的活化及其在以下方面的有害作用： 通过使用野生型和醛糖还原酶缺陷小鼠的缺血性急性肾损伤，2）通过使用野生型和果糖激酶全局和近端小管缺陷小鼠的果糖激酶和内源性果糖代谢的活化及其在缺血性急性肾损伤中的有害作用，和3）通过使用人近端小管细胞的导致近端小管功能障碍、损伤和细胞死亡的果糖下游机制，（HK-2）。申请人将依靠一个优秀的导师计划与博士理查德约翰逊作为他的主要导师。约翰逊博士是果糖、尿酸及其在内皮功能障碍、代谢综合征和肾脏疾病中所起作用的主要研究人员之一。他目前是科罗拉多丹佛大学肾脏疾病和高血压系主任和医学教授。此外，科罗拉多丹佛大学医学副教授Sarah Faubel博士是他的二级导师，也是缺血性急性肾损伤的主要研究者，在动物模型、肾损伤和多器官功能障碍的表征方面具有专长。申请人还将依靠肾脏部门以外的几位顾问的专业知识和技术，眼科系教授兼研究副主席Mark Petrash博士是醛糖还原酶的世界专家，Scott Lucia博士是合作者（肾脏和泌尿生殖病理学主任）也将作为评估肾损伤和布鲁斯莫利托里斯博士的合作者，印第安纳州大学医学教授将协助Lanaspa博士开发近端小管果糖激酶缺陷小鼠。该奖项将使申请人能够发展成为独立科学家所需的技能，并将通过教学计划和讲座以及促进与不同部门的各种研究人员的互动来促进智力发展，机构职能体系 公共卫生相关性：急性肾损伤是一种常见的临床并发症，占重症监护室入院人数的30- 50%，无可用治疗。已发表的数据表明，膳食果糖可导致急性肾损伤。这项研究计划将集中在内源性产生的果糖的有害作用，通过多元醇途径（目标1）和果糖激酶代谢（目标2和3）。多元醇途径和果糖激酶的刺激诱导ATP消耗、尿酸和氧化剂产生，因此是促成与缺血性急性肾损伤相关的近端小管细胞死亡的放大力。如果我们的假设是正确的，那么阻断该通路不仅可以作为预防缺血性急性肾损伤（如心血管前手术）的手段，而且可以作为肾损伤发生后加速肾恢复的靶点，具有临床意义。

DESCRIPTION (provided by applicant): Acute kidney injury is a common cause of hospitalization with high mortality affecting 30% of patients admitted to the intensive care unit. After decades of important discoveries regarding its pathophysiology, no clinically applicable treatment to accelerate kidney recovery in acute kidney injury has emerged. The polyol pathway is a metabolic route constituted by two enzymes, aldose reductase and sorbitol dehydrogenase. Aldose reductase converts glucose to sorbitol while sorbitol dehydrogenase metabolizes sorbitol to fructose. Our preliminary data in mice with ischemic acute kidney injury demonstrate that there is a significant activation of the polyol pathway in the kidney cortex as noted by high level of aldose reductase, and fructose accumulation (endogenous fructose). Our published data demonstrate that in the kidney the metabolism of fructose by the enzyme fructokinase results in ATP depletion and the generation of uric acid and oxidants causing acute tubulointerstitial injury. These observations lead to the overall hypothesis of this application that ischemic acute kidney injury activates the polyol pathway and fructokinase which contributes to proximal tubule cell death. The significance of this proposal is that inhibition of the polyol pathway is feasible n patients with acute kidney injury due to the availability of inhibitors (epalrestat, ranirestat). Te innovation of this proposal is that a role for endogenous fructose and renal fructokinase has never been considered in ischemic acute kidney injury. The research design to study the deleterious role of the polyol pathway and endogenous fructose production and metabolism will involve the characterization of 1) the activation of the polyol pathway and its deleterious role in ischemic acute kidney injury by using wild type and aldose reductase deficient mice, 2) the activation of fructokinase and endogenous fructose metabolism and its deleterious role in ischemic acute kidney injury by utilizing wild type and fructokinase global and proximal tubule deficient mice and 3) the fructose downstream mechanisms that leads to proximal tubule dysfunction, injury and cell death by employing human proximal tubular cells, (HK-2). The applicant will rely on an excellent mentorship program with Dr. Richard Johnson as his primary Mentor. Dr Johnson is one of the leading researchers in fructose, uric acid and the role they play in endothelial dysfunction, metabolic syndrome and kidney disease. He is currently the Division Head and Professor of Medicine at the University of Colorado Denver, Division of Renal Diseases and Hypertension. In addition, Dr. Sarah Faubel, Associate Professor of Medicine, at University of Colorado Denver, is his secondary Mentor and a leading investigator in ischemic acute kidney injury with expertise in animal models, characterization of kidney injury and multiorgan dysfunction. The applicant will also rely on the expertise and technology from several consultants outside the Renal Division, Dr Mark Petrash, Professor and Vice Chair for Research, Department of Ophthalmology, who is a world expert on aldose reductase is serving as a collaborator, Dr Scott Lucia (Chief of Renal and genitourinary pathology) awill also act as collaborator in the assessment of kidney injury and Dr Bruce Molitoris, Professor of Medicine at Indiana University will assist Dr Lanaspa in the development of proximal tubule fructokinase deficient mice This award will allow the applicant to develop the skills necessary to become an independent scientist and will provide for intellectual development through both didactic programs and lectures and by facilitating interactions with a variety of researchers in different departments and institutions. PUBLIC HEALTH RELEVANCE: Acute kidney Injury is a common clinical complication accounting for 30-50 % admissions to the intensive care unit with no available treatment. Published data demonstrate that dietary fructose can cause acute kidney injury. This research proposal will focus in the deleterious role of endogenously produced fructose by the polyol pathway (Aim 1) and its metabolism by fructokinase (Aims 2 and 3). Stimulation of the polyol pathway and fructokinase induces ATP depletion, uric acid and oxidant generation thus being an amplifying force that contributes to proximal tubule cell death associated to ischemic acute kidney injury. If our hypothesis is correct, blockade of this pathway could be clinically relevant not only as means to prevent ischemic acute kidney injury (such as precardiovascular surgery), but as a target to accelerate renal recovery after the onset of renal injury.