Protein carbamylation and uremic cardiomyopathy in chronic kidney disease

项目摘要/摘要 越来越多的证据表明，尿素的蛋白质修饰(氨甲酰化)有助于尿毒症 心肌病和死亡率。我们最近开发了一种检测氨基甲酸白蛋白(C-Alb)的方法，这是一种血液测试 类似于“治疗尿毒症的血红蛋白A1c”。我们已经证明，C-Alb值可以预测心力衰竭的风险 和心脏原因导致的死亡的血液透析患者和氨基酸缺乏是关键 氨基甲酰化的决定因素和C-Alb可以通过氨基酸清除剂治疗而减少。此外， 尿素对小鼠的高氨基甲基化足以引起小鼠的心功能障碍。这项建议旨在 研究C-Alb是否也能预测慢性肾脏疾病患者在开始服用 透析治疗，以扩大这项测试的临床应用到早期阶段的患者 疾病，当治疗方法的改变有机会防止疾病进展的时候。第二，我们想要证明 尿素对慢性肾脏病和氧化损伤小鼠心脏的特异性毒性及其机制的研究 应激相关的心肌病。目标1将检验C-Alb是预后生物标志物的假设 非透析患者与死亡率、发病率、进展至透析和蛋白质能量浪费有关 慢性肾脏病2-5期患者。目标1将进一步比较与C-Alb相关的风险 尿毒症标准临床指标的比较，以探讨C-Alb是否为尿毒症更好的指征 早期开始透析，并将检验高C-Alb与特定功能缺陷相关的假设 氨基酸和其他基本营养素，代表了靶向营养疗法的候选对象。目标2 将寻求建立良好控制的尿素诱导的心肌病小鼠模型，以证明直接 尿素对心脏的毒性并研究其可能的机制。我们的假设是，诱导孤立的 给肾功能减退的小鼠或对尿毒症敏感的小鼠喂饲尿素可增加循环中的尿素 心肌线粒体氧化应激将导致心肌病和心力衰竭，类似于 患有慢性肾脏疾病的患者。目标2(A)将利用POD-ATTAC小鼠模型诱导肾脏 在饮食中给予尿素以测试高尿毒症叠加在肾脏上的影响的失败小鼠 不够用。对照组动物将接受类似的足细胞消融治疗，但喂食正常饮食。动物们会 通过超声心动图监测心功能的差异，并研究心肌功能的差异 介导尿素毒性的信号通路。目标2(B)将利用心脏特异的小鼠模型 PGC-1α辅活化子缺失。这些动物遭受心肌线粒体氧化应激的增加。 并且容易患上应激性心肌病。给这些动物喂食尿素将检验 尿素对肾功能正常的动物的心脏氧化应激和肌病的作用，进一步分离 尿素对心脏的影响。

PROJECT SUMMARY/ABSTRACT There is growing evidence that protein modification by urea (carbamylation) contributes to uremic cardiomyopathy and mortality. We recently developed an assay for carbamylated albumin (C-Alb), a blood test similar to “hemoglobin A1c for uremia.” We have shown that C-Alb values are predictive of risk of heart failure and death from cardiac causes in patients on hemodialysis and that amino acid deficiencies are critical determinants of carbamylation, and C-Alb can be reduced by amino acid scavenger therapy. Moreover, hypercarbamylation by urea in mice is sufficient to induce cardiac dysfunction in mice. This proposal seeks to investigate whether C-Alb also predicts outcomes in patients with chronic kidney disease prior to initiation of dialysis therapy in order to extend the clinical applications of this test to patients in the earlier stages of disease, when changes in treatment have a chance to prevent disease progression. Second, we want to prove the specific toxicity of urea on the heart and investigate its mechanisms in mouse models of CKD and oxidative stress-associated cardiomyopathy. AIM 1 will test the HYPOTHESIS that C-Alb is a prognostic biomarker associated with mortality, morbidity, progression to dialysis, and protein energy wasting in non-dialyzed patients with stages 2-5 chronic kidney disease. Aim 1 will further compare the risk associated with C-Alb to that of standard clinical indicators of uremia in order to probe whether C-Alb may be a superior indication of early initiation of dialysis, and will test the hypothesis that high C-Alb is associated with deficiencies of specific amino acids and other essential nutrients which represent candidates for targeted nutritional therapies. AIM 2 will seek to develop well controlled mouse models of urea-induced cardiomyopathy in order to prove the direct toxicity of urea on the heart and to study potential mechanisms. Our HYPOTHESIS is that inducing isolated increases in circulating urea by feeding urea to mice with reduced kidney function or to mice with sensitivity to cardiac mitochondrial oxidative stress will produce cardiomyopathy and heart failure similar to that seen in patients with chronic kidney disease. Aim 2(a) will utilize the POD-ATTAC mouse model of inducible kidney failure mice which will be fed urea in their diet to test the effects of hyperuremia superimposed upon renal insufficiency. Control animals will be similarly treated with podocyte ablation but fed normal diets. Animals will be monitored by echocardiography for differences in cardiac function, and studied for differences in myocardial signaling pathways which mediate urea's toxicity. Aim 2(b) will utilize a mouse model with a cardiac-specific deficiency of PGC-1α coactivator. These animals suffer from increased cardiac mitochondrial oxidative stress and are prone to stress-induced cardiomyopathy. Feeding urea to these animals will test the contribution of urea to cardiac oxidative stress and myopathy in an animal with normal kidney dysfunction, further isolating the effect of urea on the heart.