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 透析疗法为了将这一测试的临床应用扩展到疾病早期阶段的患者， 当治疗方法的改变有机会防止疾病进展时。第二，我们要证明具体的 尿素对慢性肾脏病和氧化应激小鼠心脏毒性及其机制的研究 伴发心肌病。目标1将检验C-Alb是一种预后相关生物标志物的假设 分期非透析患者的死亡率、发病率、进展到透析和蛋白质能量浪费 慢性肾脏病2-5例。目标1将进一步比较C-Alb与标准临床的风险 尿毒症的指标为了探讨C-Alb是否可能是早期开始透析的更好的指征， 并将检验这一假设，即高C-Alb与特定氨基酸和其他 代表靶向营养疗法候选对象的基本营养素。目标2将寻求良好的发展 尿素致心肌病小鼠模型的建立及其对心脏直接毒性的研究 并研究可能的机制。我们的假设是通过以下方式导致循环中尿素的单独增加 给肾功能减退小鼠或对心肌线粒体氧化敏感的小鼠喂饲尿素 压力会导致心肌病和心力衰竭，类似于慢性肾脏疾病患者的情况。 目标2(A)将利用5/6肾切除和足细胞特异性Cosmc缺陷小鼠肾功能衰竭模型 将在饮食中喂入尿素的小鼠，以测试高尿毒症叠加肾功能不全的影响。 将通过超声心动图监测动物心脏功能的差异，并研究动物心脏功能的差异 介导尿素毒性的心肌信号通路。目标2(B)将利用小鼠心脏模型- PGC-1α辅活化子的特异性缺陷。这些动物患有心肌线粒体氧化增加。 应激，容易引起应激引起的心肌病。给这些动物喂食尿素会检验它们的贡献 尿素对肾功能正常动物心脏氧化应激和肌病的影响，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 5/6 nephrectomy and podocyte-specific COSMC-deficient mouse models of kidney failure mice which will be fed urea in their diet to test the effects of hyperuremia superimposed upon renal insufficiency. 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.