The Production of Uremic Solutes by Colon Microbes

描述(申请人提供)：传统的透析提供有限的有机溶质清除，当肾脏衰竭时积聚。因此，许多研究都在研究增加透析频率和持续时间的影响。另一种方法是减少溶质的产生。这种方法一直被忽视，因为我们对尿毒症溶质产生的了解是如此有限。目前的提案将专注于由结肠中的微生物制造的尿毒症溶质。直到最近，对结肠微生物的研究一直很困难，因为它们中的大多数都不容易培养。但是，新的独立于培养的基因组技术使描绘整个结肠微生物种群或“微生物组”，并识别与特定溶质产生相关的微生物成为可能。代谢组学技术使我们有可能扩大对微生物产生的溶质的了解。这项探索性的建议将把这些新技术应用于微生物衍生的尿毒症溶质的研究。第一个目标是确定与众所周知的尿毒症溶质生产相关的结肠微生物种群的特征。研究人员发现，在食用素食的受试者中，微生物衍生的硫代吲哚(吲哚)和对甲酚硫酸盐的产量大大减少。拟议中的研究将利用这一发现，使用最近开发的PhyloChip微阵列技术来比较素食受试者和饮食不受限制的受试者的微生物群。对阵列数据的分析将使我们能够确定与生产目前未知的吲哚和对甲酚硫酸盐相关的微生物亚族。第二个目的是确定透析患者结肠微生物种群的变化。研究人员发现，在腹膜透析患者和血液透析患者中，吲哚青硫酸酯和对甲酚硫酸盐的产生存在很大差异。植物芯片技术的应用将使我们能够识别与溶质生产中的这些主要差异相关的微生物组的差异。第三个目标是确定由结肠微生物产生的其他尿毒症溶质。使用FTICR-MS对来自结肠完整的透析患者和结肠切除的透析患者的样本进行比较，将提供比现在可用的更全面的这些溶质的图像。总体目标是更好地了解尿毒症溶质的产生。这样的认识最终可以让我们改进终末期肾功能衰竭的治疗，而不需要繁琐的强化透析。在结肠中产生的尿毒症溶质提供了一个特别吸引人的研究目标。因为它们是在一个孤立的隔间里由微生物产生的，所以它们的产生可能比其他溶质的产生更容易被抑制。拟议的研究是朝着测试减少微生物衍生尿毒症溶质产生的治疗方法的最终目标迈出的第一步。与公共卫生相关：透析患者遭受的大部分残留疾病是由于残留的废化学物质，这些化学物质没有通过当代治疗得到充分去除。目前的提案将专注于由结肠中的微生物制造的尿毒症溶质。基于DNA的技术将被应用于识别参与这些溶质生产的微生物。最终，我们希望操纵结肠微生物可以为改善透析患者的健康提供一种手段，而不会增加他们在透析机上花费的时间。

DESCRIPTION (provided by applicant): Conventional dialysis provides limited clearance of organic solutes that accumulate when the kidneys fail. Numerous studies are therefore examining the effects of increasing dialysis frequency and duration. An alternate approach would be to reduce solute production. This approach has been neglected because our knowledge of uremic solute production is so limited. The current proposal will focus on uremic solutes made by microbes in the colon. The colon microbes have until recently been difficult to study because most of them are not easily cultured. But new culture-independent, genomic techniques have made it possible to profile the entire colon microbial population, or "microbiome," and to identify microbes associated with the production of specific solutes. Metabolomic techniques have made it possible to expand our knowledge of the solutes that the microbes produce. This exploratory proposal will apply these new techniques to the study of microbially-derived uremic solutes. The first aim is to identify features of the colon microbial population associated with the production of well known uremic solutes. The investigators have found that production of the microbially-derived solutes indoxyl sulfate (indican) and p-cresol sulfate is much reduced in subjects consuming a vegetarian diet. The proposed studies will exploit this finding by using recently developed PhyloChip microarray technology to compare the microbiome in vegetarian subjects and subjects eating an unrestricted diet. Analysis of the array data will allow us to identify the microbial subfamilies associated with production of indican and p-cresol sulfate, which are at present unknown. The second aim is to identify alterations in the colon microbial population in dialysis patients. The investigators have identified large differences in indican and p-cresol sulfate production in patients on peritoneal dialysis and patients on hemodialysis. Application of PhyloChip technology will allow us to identify differences in the microbiome associated with these major differences in solute production. The third aim is to identify additional uremic solutes made by colon microbes. Use of FTICR-MS to compare samples from dialysis patients who have intact colons and dialysis patients with colectomies will provide a much more comprehensive picture of these solutes than is now available. The overall aim is to better understand the production of uremic solutes. Such understanding could eventually allow us to improve our treatment for end stage renal failure without burdensome intensifications of dialysis. Uremic solutes that are made in the colon provide a particularly attractive target for study. Because they are made in an isolated compartment by microbes, their production may prove simpler to suppress than that of other solutes. The proposed studies represent an initial step toward the eventual goal of testing treatments which reduce the production of microbially-derived uremic solutes. PUBLIC HEALTH RELEVANCE: Much of the residual illness suffered by dialysis patients is due to retained waste chemicals that are not adequately removed by contemporary treatment. The current proposal will focus on uremic solutes made by microbes in the colon. DNA based techniques will be applied to identify microbes involved in the production of these solutes. Ultimately, we hope that manipulating the colon microbes could provide a means for improving the health of dialysis patients without increasing the time they spend on the dialysis machine.