Probiotic-Induced Elimination of Oxalate to treat Hyperoxaluria

描述（由申请人提供）：在本申请中，我们建议研究益生菌促进草酸的肠道主动消除和肠道降解，作为一种管理两种不同临床实体的方法，这些实体具有共同的草酸尿排泄增加导致肾结石形成。1)原发性高草酸尿1型（PH1）遗传性疾病中，由于肝酶丙氨酸-乙醛酸氨基转移酶（AGT）缺乏，内源性草酸生成增加，除了草酸盐组织沉积（草酸中毒）外，还会导致高草酸尿和草酸钙肾结石形成，肾功能衰竭和死亡，除非及早进行积极的临床治疗。不幸的是，唯一已知的治疗PH1的方法是肝脏或肝肾移植。2)新的高血氧症患者通过减肥手术治疗肥胖，这一人群中肾结石发生率的增加是显著的。除了PH1和减肥手术患者外，这种治疗方法的潜在影响，如果有效，将扩展到更大的特发性草酸钙结石患者群体，这些患者约占美国人的12%，并与大量医疗保健费用相关。从我们对大鼠和小鼠肠道草酸转运的研究中得出的几个关键信息为本文提出的研究提供了方向。首先，在草酸缺乏大鼠和慢性肾衰竭大鼠中，大肠是草酸代偿性肠内排泄的主要部位。其次，我们已经证明，底物/草酸盐特异性微生物，草酸杆菌sp.，只存在于大肠中，可以通过改变结肠草酸盐从吸收到主动分泌/排泄的方向，显著降低尿草酸盐的排泄。第三，我们从一项使用PH1小鼠模型（AGT敲除小鼠）的初步研究中获得结果，显示草酸杆菌定殖AGT敲除小鼠的整个大肠在草酸分泌模式下功能，这与草酸盐排泄正常化相关，否则高血氧动物。其他细菌，包括乳酸杆菌和双歧杆菌，在草酸降解活性方面是“通才”，已被证明可以显著减少人类和大鼠尿液中草酸的排泄；然而，尚不清楚这些细菌是否能与肠黏膜相互作用，促进草酸盐转运的变化，类似于草酸杆菌。不管确切的机制是什么，也许有可能利用这些肠道细菌的活动，无论是单独的还是共同的，以减少PH1中的草酸负荷。现在我们有了PH1的动物模型和减肥手术的大鼠模型，我们有了一个独特的机会来直接解决这些问题，并获得关于高草酸尿治疗的新信息。因此，在目标1和目标2中，我们将验证这样的假设：在AGT KO小鼠和大鼠减肥手术模型中，由于在施用纯培养物或相关纯培养物（包括草酸杆菌、乳酸杆菌和双歧杆菌）后，肠道草酸盐消除的诱导，尿草酸盐排泄可以发生正常化。我们将测试肠道草酸转运蛋白表达模式的代偿适应可以解释功能变化的假设。这些研究的结果将揭示一个新的方向，导致基于细菌/细菌产物的益生菌系统的发展，促进肠道草酸排泄和降解，从而使尿草酸排泄正常化。

DESCRIPTION (provided by applicant): In this application we are proposing to examine the promotion of active intestinal elimination and luminal degradation of oxalate by probiotics as a way of managing two different clinical entities having in common an increased urinary excretion of oxalate leading to kidney stone formation. 1) In the genetic disease of Primary Hyperoxaluria Type 1 (PH1), an increased endogenous production of oxalate, due to a deficiency of the liver enzyme alanine-glyoxylate aminotransferase (AGT), results in hyperoxaluria and calcium oxalate kidney stone formation in addition to tissue deposition of oxalate (oxalosis), renal failure and death unless early aggressive clinical management is instigated. Unfortunately, the only known cure for PH1 is a liver or liver-kidney transplant. 2) A new population of hyperoxaluric patients who have undergone bariatric surgery for obesity has been steadily emerging and the increased incidence of kidney stone formation in this group is significant. In addition to the population of patients with PH1 and bariatric surgery, the potential impact of this therapeutic approach, if effective, will extend to a much larger population of idiopathic calcium oxalate stone formers who comprise ~12% of Americans and is associated with a substantial health care cost. Several key pieces of information have emerged from our studies of intestinal oxalate transport in rats and mice have provided the direction for the studies proposed here. First, the large intestine is the primary site for compensatory enteric excretion of oxalate in oxalate-challenged rats and in rats with chronic renal failure. Second, we have shown that the substrate/oxalate-specific microorganism, Oxalobacter sp., which resides exclusively in the large intestine, can significantly lower urinary oxalate excretion by altering the direction of colonic oxalate transport from absorption to active secretion/excretion. Third, we have acquired results from a pilot study using a mouse model of PH1 (AGT knockout mouse) showing the entire large intestine of the Oxalobacter-colonized AGT knockout mouse functions in an oxalate secretory mode that is correlated with a normalization of oxalate excretion in otherwise hyperoxaluric animals. Other bacteria including Lactobacillus sp. and Bifidobacterium sp. that are "generalists" in terms of their oxalate-degrading activity have been demonstrated to significantly reduce urinary oxalate excretion in humans and in rats; however, it is not known whether these bacteria can interact with the intestinal mucosa to promote changes in oxalate transport similar to Oxalobacter. Regardless of the precise mechanism, perhaps it is possible to exploit the activities of these intestinal bacteria, either individually or together, in order to reduce the oxalate burden in PH1. Now that we have an animal model of PH1 as well as a rat model for bariatric surgery, we have a unique opportunity to directly address these questions and obtain novel information regarding a treatment for hyperoxaluria. Thus in Aims 1 and 2 we will test the hypothesis that normalization of urinary oxalate excretion can occur in AGT KO mice and in the rat bariatric surgical model due to an induction of enteric oxalate elimination following the administration of either a pure culture or a combination of pure cultures of interest, including Oxalobacter sp., Lactobacillus sp., and Bifidobacterium sp. In Aim 3, we will test the hypothesis that compensatory adaptations in the expression patterns of intestinal oxalate transport proteins can explain changes in function. The results from these studies should reveal a novel direction leading to the development of a probiotic system based upon bacteria/bacterial products that promote both enteric oxalate excretion and degradation thereby normalizing urinary oxalate excretion. PUBLIC HEALTH RELEVANCE: The studies proposed will examine the activity and effectiveness of several non-pathogenic bacteria, either individually or combined, to promote intestinal oxalate excretion and degradation in the setting of Primary Hyperoxaluria, Type 1 (PH1) and following bariatric surgery which is associate with hyperoxaluria and kidney stone disease. Especially important and relevant to the present application is the availability of a knockout mouse model that mimics PH1, namely the AGT (alanine-glyoxylate aminotransferase) null mouse as well as an obese rat bariatric surgical model which affords us a unique opportunity to evaluate the interaction between these bacteria and the oxalate-transporting mucosa of the large intestine.