Pathogenesis of Diabetic Nephropathy

糖尿病肾病的发病机制

• 批准号: 8546328
• 负责人: Yashpal S. Kanwar
• 金额: $ 32.43万
• 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/8546328
• 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.

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的作用，即，肌肌醇加氧酶（MIOX）在糖尿病肾病（DN）背景下的肾小管间质病理生物学中的作用。DN的特征在于肾细胞中各种代谢/细胞信号传导途径的扰动，导致活性氧（ROS）的产生。后者已成为DN发病机制的核心。代谢/信号事件主要在肾小球细胞中描述，与肾小管间质细胞相关的信息有限。葡萄糖响应性MIOX通过葡糖醛酸-木酮糖（GX）途径将肌醇分解代谢为D-葡糖醛酸，如“眼透镜”中所述，并且其代谢物进入戊糖途径。由MIOX引发的GX途径导致“氧化还原失衡”，NADPH：NADP+和NAD+：NADH比率在4个步骤受到干扰[图1]，类似于多元醇途径;表明其活化将诱导氧化剂和缺氧应激，最终导致ECM蛋白合成增加和DN中的小管间质损伤[图2]。干扰的NAD+/NADH比率也会导致NAD+的消耗，结果NAD依赖性脱乙酰酶（Sirutins）的活性受损。Sirutins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。随着这些扰动，肾小管细胞可能经历能量应激和凋亡。我们发表的（JBC 2011，AJP 2010）和初步数据表明，ROS在GX通路中产生，这反过来又增加了MIOX的转录，从而建立了ROS的循环产生。数据还表明，GX通路存在于肾脏中[图4]，并且氧化应激确实发生在DN患者的肾小管隔室中[图3]。此外，MIOX在高葡萄糖中的过表达导致ECM蛋白的合成增强[图10]。在这一背景下，为了实现提案的目标，提出了以下3个具体目标。目的：阐明高糖环境下体外培养肾小管细胞中MIOX过表达导致氧化应激、线粒体功能障碍和ECM合成加重的机制。将评估NADPH：NADP+和NAD+：NADH比率、GSH、N 0X 4、PKC、TGF-、SIRT、转录因子、线粒体动力学以及促凋亡基因和抗凋亡基因的状态。将使用特异性抑制剂/激活剂检测MIOX效应的特异性。目的II是在体内表征MIOX诱导的GX通路、氧化还原失衡和下游信号传导事件导致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CD 1小鼠和与秋田小鼠杂交的过表达MIOX的小鼠。目的III是确定MIOX基因缺失是否导致STZ诱导的糖尿病杂合子（+/-）小鼠中肾功能障碍的改善和肾小管-间质损伤的进展，以及突变型MIOX（-/-）小鼠与秋田小鼠杂交时。GX-SIRT通路的研究将有助于设计新的治疗策略以减缓DN中肾小管间质损伤。