Gut Microbiota and Effect on Immune Suppressants in Transplantation

吗替麦酚酯（Myocphenolate mofetil，MMF）和他克莫司（tacrolimus）是目前应用于90%以上肾脏的主要免疫抑制剂 移植（德克萨斯州）。几项研究表明，低麦考酚酸（MPA，活性 通过12小时曲线下面积（AUC）和急性同种异体移植物 排斥反应然而，MMF的药代动力学（PK）存在显著的个体间差异， 在相同剂量下，AUC的变化高达10倍。MPA浓度升高与以下因素有关： 一些研究中出现毒性反应，如腹泻、白细胞减少和贫血。PK研究显示MPA的第二个峰 6-8口服MMF后24小时，由于其酚类物质的胆汁排泄，导致MPA的肠肝再循环（EHR） 葡糖苷酸（MPAG，MPA的主要非活性代谢产物）。EHR通过β-葡萄糖醛酸苷水解而发生， 葡萄糖醛酸酶产生的肠道细菌和MPA的重吸收。广泛的EHR大大提高了系统性 暴露于MPA并可能增强免疫抑制和毒性。β-葡萄糖醛酸苷酶由 肠道微生物无乳链球菌、产气荚膜梭菌和E.大肠杆菌和已知的影响药物 基板和潜在的EHR的程度。在一项对tx患者粪便的初步研究中， 腹泻患者瘤胃球菌、粪球菌和多雷球菌的检出率显著降低。具体 有一种假说认为，粪便微生物群某些模式导致EHR增加、MPA全身暴露增加 和毒性。因此，我们将确定微生物组与MPA和代谢物PK的相关性。 EHR（Aim 1）和MPA相关毒性如贫血和白细胞减少症（Aim 2）。最后，我们将 确定微生物组多样性与接受MPA治疗的患者的腹泻的相关性（目的3）。一 将开发具有连续粪便微生物组样本的新肾TX的前瞻性队列， 测量代谢物PK和EHR（目标1），随后评估白细胞减少症和贫血（目标2）。 我们将测量与治疗后腹泻相关的连续粪便微生物组（目标3）。所有受试者将 在治疗后12个月随访估计的肾小球滤过率，这与长期肾脏损害有关。 结果。微生物组将使用创新的鸟枪测序来确定所有目标，沿着 Aim 3真菌的内部转录间隔区2（ITS2）基因测序。我们将使用元转录组学 微生物β-葡萄糖醛酸苷酶，使用RNAseq，以阐明微生物组 影响MPA暴露、MPA相关的白细胞减少症和贫血以及术后腹泻。我们将收集 以患者为中心的腹泻结果使用文本消息。在研究结束时，我们将开发出 微生物群模式，可用作预测何时需要MPA PK评估的检测， 选择MPA剂量以尽量减少毒性。这项研究可能会导致未来使用选择抗生素或粪便 移植以恢复微生物组，从而确保正常的药物处置和最小的MPA相关 毒性我们将创建一个模型来研究其他经历EHR的药物， 由于微生物组的吸收或分布。

Myocphenolate mofetil (MMF) and tacrolimus are the main immune suppressants used in over 90% of kidney transplants (tx). Several studies have shown an association between low mycophenolic acid (MPA, active metabolite of MMF) exposure as measured by 12 hour area-under-the-curve (AUC) and acute allograft rejection. However, significant inter-individual variation in the pharmacokinetics (PK) of MMF exists with as much as a 10-fold variation in AUC with the same dose. Elevated MPA concentrations have been associated in some studies with toxicities such as diarrhea, leukopenia and anemia. PK studies show a second peak of MPA 6-8 hours after oral MMF from enterohepatic recycling (EHR) of MPA due to biliary excretion of its phenolic glucuronide (MPAG, major inactive metabolite of MPA). EHR occurs by hydrolysis of the glucuronide by β- glucuronidases produced by gut bacteria and reabsorption of MPA. Extensive EHR greatly increases systemic exposure to MPA and likely enhances immunosuppression and toxicity. β-glucuronidases are produced by the gut microbes Streptococcus agalactiae, Clostridium perfringens, and E. coli and are known to influence drug substrates and potentially the extent of EHR. In a pilot study of stool from tx patients, Bacteroides, Ruminococcus, Coprococcus, and Dorea were significantly lower in tx patients with diarrhea. The specific hypothesis is that certain patterns of stool microbiota lead to increased EHR, greater MPA systemic exposure and toxicities. Therefore, we will determine the association of microbiome with: MPA and metabolite PK posttx and EHR (Aim 1) and MPA associated toxicities such as anemia and leukopenia posttx (Aim 2). Lastly we will determine the association of microbiome diversity with diarrhea in tx recipients on MPA posttx (Aim 3). A prospective cohort of new kidney txs with serial stool microbiome samples will be developed and MPA and metabolite PK and EHR measured (Aim 1), and subsequent assessment of leukopenia and anemia (Aim 2). We will measure serial stool microbiome for association with diarrhea posttx (Aim 3). All subjects will be followed for 12 months posttx for estimated glomerular filtration rate which is associated with long-term kidney outcomes. The microbiome will be determined using innovative, shotgun sequencing for all aims, along with Internal Transcribed Spacer 2 (ITS2) gene sequencing for fungi for Aim 3. We will use metatranscriptomics of microbial β-glucuronidases, using RNAseq, to elucidate the mechanism through which the microbiome influences MPA exposure, and MPA associated leukopenia and anemia, and posttx diarrhea. We will collect patient centered outcomes of diarrhea using text messaging. By the end of the study, we will have developed microbiota patterns that could be utilized as a predictive test for when MPA PK assessment is needed, for selection of MPA dose to minimize toxicities. This study can lead to future use of select antibiotics or fecal transplants to restore the microbiome thereby assuring normalized drug disposition and minimal MPA related toxicities. We will have created a model to study other drugs that undergo EHR or which have perturbed absorption or distribution due to the microbiome.