Pathogenesis of Diabetic Nephropathy

糖尿病肾病的发病机制

• 批准号: 8435266
• 负责人: Yashpal S. Kanwar
• 金额: $ 33.6万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-15 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8435266
• 关键词: Affect; Aldehyde Reductase; Antioxidants; Apoptosis; Apoptotic; Attention; Biochemical; Biogenesis; Biology; Breeding; Carboxy-Lyases; Cell Cycle Proteins; Cells; Cicatrix; Complex; Crystalline Lens; D-Xylulose reductase; Data; Deacetylation; Dependency; Diabetes Mellitus; Diabetic Nephropathy; Dialysis procedure; Diet; End stage renal failure; Energy Metabolism; Enzymes; Epithelial; Event; Expenditure; Extracellular Matrix; Extracellular Matrix Proteins; Family; Fatty acid glycerol esters; Fibrosis; Functional disorder; GTP Binding; Gene Deletion; Generations; Genes; Genetic; Genetic Transcription; Glucose; Glucuronates; Glucuronic Acids; Heterozygote; Hypoxia; In Vitro; Injury; Inositol; Insulin; Insulin Resistance; Interruption; Kidney; Knockout Mice; MEKs; Metabolic; Metabolic syndrome; Metabolism; Methods; Mitochondria; Molecular; Mus; Mutation; NADH; NADP; Nonesterified Fatty Acids; Obesity; Oxidants; Oxidation-Reduction; Oxidoreductase; Pathogenesis; Pathway interactions; Patients; Pentoses; Physiological; Play; Population; Production; Progress Reports; Protein Kinase C; Proteins; Publishing; Reactive Oxygen Species; Role; Signal Pathway; Signal Transduction; Smad Proteins; Smad protein; Specificity; Streptozocin; Stress; Testing; Transcription Coactivator; Tubular formation; Xylitol; Xylulokinase; Xylulose; catalase; enzyme pathway; feeding; gulonic acid; in vivo; inhibitor/antagonist; inositol oxygenase; interstitial; interstitial cell; kidney cell; mitochondrial dysfunction; mutant; novel therapeutics; overexpression; oxidant stress; polyol; research study; transcription factor

DESCRIPTION (provided by applicant): Overall objective of the proposal is to delineate the role of a proximal tubular specific enzyme, i.e., myo- inositol oxygenase (MIOX), in tubulo-interstitial pathobiology in the context of diabetic nephropathy (DN). The DN is characterized by perturbation in various metabolic/cellular signaling pathways in renal cells resulting in the generation of reactive oxygen species (ROS). The latter have emerged as central to the pathogenesis of DN. The metabolic/signaling events have been delineated largely in renal glomerular cells, and information relating to tubulointerstitial cells is limited. Glucose responsie MIOX catabolizes myo-inositol to D-glucuronate via Glucuronate-Xylulose (GX) pathway, as described in "eye lens", and its metabolites enter pentose pathway. The GX pathway initiated by MIOX leads to "redox imbalance" with perturbed NADPH:NADP+ and NAD+:NADH ratios at 4 steps [Fig. 1], akin to polyol pathway; suggesting that its activation would induce oxidant and hypoxic stress culminating into an increased synthesis of ECM proteins and tubulo-interstitial injury in DN [Fig. 2]. Perturbed NAD+/NADH ratio would also cause depletion of NAD+, as a result the activity of NAD-dependent deacetylases, Sirutins, are compromised. Targets of Sirutins include FOXO family transcription factors and transcriptional coactivator PGC-1¿, which modulate mitochondrial biogenesis and various antioxidant genes. With these perturbations the tubular cells are likely to undergo energy stress and apoptosis. Our published (JBC 2011, AJP 2010) and preliminary data suggest that ROS are generated in the GX pathway, which in turn increases the transcription of MIOX, thus setting up cyclic generation of ROS. Data also suggest that GX pathway exist in the kidney [Fig. 4], and oxidant stress does occur in the tubular compartment in patients with DN [Fig. 3]. Also, MIOX over-expression in high glucose leads to accentuated synthesis of ECM proteins [Fig. 10]. With this background and to achieve objectives of the proposal the following 3 specific aims are proposed. AIM I is to delineate mechanisms by which MIOX overexpression in vitro in tubular cells leads to accentuation of the oxidant stress, mitochondrial dysfunctions and ECM synthesis in the presence of high glucose. Status of NADPH:NADP+ & NAD+:NADH ratios, GSH, NOX4, PKC, TGF-, SIRTs, transcription factors, mitochondrial dynamics, and pro- and anti-apoptotic genes will be assessed. Specific inhibitors/activators will be used to test the specificity of MIOX effects. AIM II is to characterie in vivo MIOX-induced GX pathway, redox imbalance and downstream signaling events leading to dysfunctions of SIRTs and mitochondria, apoptosis and tubulo- interstitial fibrosis. CD1 mice with STZ-induced diabetes and mice over-expressing MIOX cross bred with Akita mice will be used. AIM III is to determine if MIOX gene deletion leads to amelioration in renal dysfunctions and progression to tubulo-interstitial injury in STZ-induced diabetes in heterozygote (+/-) mice and when the mutant Null (-/-) mice are cross bred with Akita mice. It is anticipated that the characterization of GX-SIRT pathway would aid in devising novel therapeutic strategies to decelerate tubulo-interstitial injury in DN. PUBLIC HEALTH RELEVANCE: Diabetic nephropathy (DN) is one of the principal causes of end-stage renal disease (ESRD) leading to dialysis dependency in the US population, thus adding substantial amount of burden to the national expenditure. DN has a relentless course when both the glomerular and tubulo-interstitial compartments are affected. In fact, tubulo-interstitial changes in DN correlate relatively better with the derangements in renal functional parameters. The premise of this application is to delineate pathogenesis of tubulo-interstitial injury in the context of DN. Evidence is presented in this application that certain pathways are specific to the tubular compartment, and they are responsible for such an injury leading to tubulo-interstitial dysfunctions/fibrosis. Interruption of various events relevant to these pathway by pharmacologic or genetic means hold promise as novel therapeutic strategies to ameliorate the progression of diabetic nephropathy.

描述（由申请人提供）：该提案的总体目标是描述近端小管特异性酶，即肌醇加氧酶（MIOX）在糖尿病肾病（DN）背景下的小管间质病理生物学中的作用。DN的特征是肾细胞中各种代谢/细胞信号通路的扰动导致活性氧（ROS）的产生。后者已成为DN发病机制的核心。代谢/信号事件主要发生在肾小球细胞中，而与小管间质细胞相关的信息有限。葡萄糖反应性MIOX通过葡萄糖醛酸-木糖糖（GX）途径将肌醇分解为d -葡萄糖醛酸盐，如“eye lens”所述，其代谢产物进入戊糖途径。由MIOX启动的GX途径与多元醇途径类似，在4个步骤中导致NADPH:NADP+和NAD+:NADH比例受到干扰，导致“氧化还原失衡”[图1]；这表明它的激活会诱导氧化和缺氧应激，最终导致DN中ECM蛋白合成增加和小管间质损伤[图2]。受干扰的NAD+/NADH比值也会导致NAD+的耗竭，导致NAD依赖的去乙酰化酶sirutin的活性受损。sirutin的靶点包括FOXO家族转录因子和转录辅激活因子PGC-1¿，它们调节线粒体生物发生和各种抗氧化基因。在这些扰动下，小管细胞很可能发生能量应激和凋亡。我们发表的（JBC 2011, AJP 2010）和初步数据表明，ROS是在GX途径中产生的，而GX途径又增加了MIOX的转录，从而建立了ROS的循环生成。数据也表明肾脏中存在GX通路[图4]，DN患者的肾小管间室确实发生氧化应激[图3]。此外，在高糖条件下，MIOX过表达会导致ECM蛋白的合成增强[图10]。在此背景下，为实现提案的目标，提出了以下三个具体目标。目的1是描述在体外小管细胞中MIOX过表达导致高糖存在下氧化应激、线粒体功能障碍和ECM合成加剧的机制。将评估NADPH:NADP+ & NAD+:NADH比率、GSH、NOX4、PKC、TGF-、SIRTs、转录因子、线粒体动力学以及促凋亡和抗凋亡基因的状态。将使用特异性抑制剂/活化剂来测试MIOX效应的特异性。AIM II是表征体内miox诱导的GX通路、氧化还原失衡和下游信号事件，导致sirt和线粒体功能障碍、细胞凋亡和小管间质纤维化。使用stz诱导的CD1糖尿病小鼠和与秋田小鼠杂交过表达MIOX的小鼠。AIM III是为了确定MIOX基因缺失是否会改善stz诱导的糖尿病杂合子（+/-）小鼠的肾功能和进展到小管间质损伤，以及当突变的Null（-/-）小鼠与秋田小鼠杂交时。预计GX-SIRT通路的表征将有助于设计新的治疗策略来减缓DN的小管间质损伤。