The contributory role of microbial metabolite in the pathogenesis of CKD-dependent vascular calcification

这项研究计划的长期目标是确定血管的分子机制。 钙化--寻找治疗慢性肾脏疾病依赖性疾病的新靶点(S) 血管钙化。血管钙化与心血管病患者的死亡率密切相关 CKD。事实上，CKD患者一半以上的死亡可归因于心血管疾病。我们的 先前的研究表明，胆汁酸核受体FXR的激活强烈地减弱了CKD- 动物模型中的依赖性血管钙化，尽管机制未知。最近，我们的新陈代谢 一种微生物胆汁酸代谢物脱氧胆酸(Dca)的水平很高。 与冠状动脉钙化(CAC)容量和腰椎较低的风险增加相关 慢性肾脏病患者和小鼠的骨密度。我们假设DCA是由 革兰氏阳性细菌会导致CKD依赖的血管钙化。我们的假设也得到了 以下证据来自我们实验室的一系列初步结果：1)慢性肾脏病增加了 循环中的DCA。2)FXR激动剂可优先降低DCA和DCA前体的水平， 胆酸。3)血管钙化的FXR基因敲除小鼠的DCA水平显著升高。4)CKD 改变肠道细菌种群，增加产生DCA的细菌水平。5)激活FXR 使CKD引起的肠道细菌种群变化正常化。6)DCA，而不是其他胆汁酸 TGR5-PKA--连环蛋白信号通路参与VSMC的矿化。确定微生物的关键作用 DCA在血管钙化的发病机制中，我们提出了3个特异性目标：特异性目标1：检测 DCA体外诱导血管钙化的分子机制。具体目标2：a)审查 循环DCA水平和肠道细菌数量的变化是否影响CKD依赖的血管 体内钙化。B)检查肠道细菌的调节是否影响CKD依赖的血管 体内钙化。具体目标3：研究TGR5-PKA--连环蛋白信号转导通路是否参与慢性肾脏病 体内依赖性血管钙化。

The long term objective of this research proposal is to determine the molecular mechanisms of vascular calcification in order to identify novel target(s) for the treatment of chronic kidney disease (CKD)-dependent vascular calcification. Vascular calcification is closely associated with cardiovascular mortality in patients with CKD. In fact, more than half of all deaths in CKD patients can be attributed to cardiovascular diseases. Our previous study revealed that activation of a bile acid nuclear receptor, FXR, strongly attenuates CKD- dependent vascular calcification in animal models though an unknown mechanism. Recently, our metabolomic approach has identified that levels of a microbial bile acid metabolite, deoxycholic acid (DCA), are highly associated with an increased risk for higher coronary artery calcification (CAC) volumes and lower lumbar bone mineral density (BMD) in human patients and mice with CKD. We hypothesized that DCA generated by gram-positive bacteria causes CKD-dependent vascular calcification. Our hypothesis is also supported by the following evidence derived from a series of preliminary results from our lab: 1) CKD increases levels of circulating DCA. 2) FXR activation by its agonists preferentially reduces levels of DCA and a precursor of DCA, cholic acid. 3) FXR knockout mice with vascular calcification have significantly higher levels of DCA. 4) CKD alters gut bacteria populations and increases levels of the DCA-producing bacteria. 5) Activation of FXR normalizes the alteration of gut bacteria populations by CKD. 6) DCA but not other bile acids induces mineralization of VSMCs through TGR5-PKA--catenin signaling. To determine the pivotal role of microbial DCA in the pathogenesis of vascular calcification, we propose 3 specific aims: Specific Aim 1: Examine the molecular mechanism by which DCA induces vascular calcification in vitro. Specific Aim 2: A) Examine whether alterations of circulating DCA levels and gut bacteria populations influence CKD-dependent vascular calcification in vivo. B) Examine whether modulation of intestinal bacteria affects CKD-dependent vascular calcification in vivo. Specific Aim 3: Examine whether TGR5-PKA--catenin signaling contributes to CKD- dependent vascular calcification in vivo.