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肾小管特异性酶（即肌醇加氧酶（MIOX））在糖尿病肾病（DN）背景下肾小管间质病理学中的作用。 DN 的特点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/信号传导事件主要在肾小球细胞中描述，而与肾小管间质细胞相关的信息有限。葡萄糖反应 MIOX 通过葡萄糖醛酸-木酮糖 (GX) 途径将肌醇分解代谢为 D-葡萄糖醛酸，如“眼睛晶状体”中所述，其代谢物进入戊糖途径。 MIOX 启动的 GX 途径导致“氧化还原失衡”，NADPH:NADP+ 和 NAD+:NADH 比率在 4 个步骤中受到干扰[图 1]。 1]，类似于多元醇途径；表明其激活会诱导氧化和缺氧应激，最终导致 DN 中 ECM 蛋白的合成增加和肾小管间质损伤[图 1]。 2]。 NAD+/NADH 比例受到干扰也会导致 NAD+ 耗尽，从而导致 NAD 依赖性脱乙酰酶 Sirutins 的活性受到损害。 Sirutins 的靶标包括 FOXO 家族转录因子和转录共激活因子 PGC-1¿，它们调节线粒体生物发生和各种抗氧化基因。由于这些扰动，肾小管细胞可能会经历能量应激和细胞凋亡。我们发表的（JBC 2011，AJP 2010）和初步数据表明，ROS 在 GX 途径中生成，这反过来又增加了 MIOX 的转录，从而建立了 ROS 的循环生成。数据还表明 GX 通路存在于肾脏中 [图 1]。 4]，并且 DN 患者的肾小管室中确实发生氧化应激[图 4]。 3]。此外，MIOX 在高葡萄糖条件下过度表达会导致 ECM 蛋白的合成增强 [图 1]。 10]。在此背景下，为了实现提案的目标，提出以下 3 个具体目标。目的 I 旨在描述在高葡萄糖存在下，肾小管细胞中 MIOX 体外过度表达导致氧化应激、线粒体功能障碍和 ECM 合成加剧的机制。将评估 NADPH:NADP+ 和 NAD+:NADH 比率、GSH、NOX4、PKC、TGF-、SIRT、转录因子、线粒体动力学以及促凋亡和抗凋亡基因的状态。特定的抑制剂/激活剂将用于测试 MIOX 效果的特异性。 AIM II 的特点是体内 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、细胞凋亡和肾小管间质纤维化。将使用患有 STZ 诱导的糖尿病的 CD1 小鼠以及与秋田小鼠杂交的过度表达 MIOX 的小鼠。目的 III 旨在确定 MIOX 基因缺失是否会导致杂合子 (+/-) 小鼠中 STZ 诱导的糖尿病以及突变型 Null (-/-) 小鼠与秋田小鼠杂交时肾功能障碍的改善和肾小管间质损伤的进展。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 的肾小管间质损伤。 公共健康相关性：糖尿病肾病（DN）是导致美国人口依赖透析的终末期肾病（ESRD）的主要原因之一，从而给国家支出增加了大量负担。当肾小球和肾小管间质室均受到影响时，DN 会持续不断地发展。事实上，DN 的肾小管间质变化与肾功能参数的紊乱相关性相对较好。本申请的前提是描述 DN 背景下肾小管间质损伤的发病机制。本申请中提出的证据表明，某些途径是肾小管室特有的，并且它们是导致肾小管间质功能障碍/纤维化的损伤的原因。通过药理学或遗传手段中断与这些途径相关的各种事件有望成为改善糖尿病肾病进展的新治疗策略。