Role of Bile Acids and Gut Bacteria in GI Diseases

胆汁酸和肠道细菌在胃肠道疾病中的作用

• 批准号: 8698288
• 负责人: PHILLIP B HYLEMON
• 金额: --
• 依托单位: VA VETERANS ADMINISTRATION HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8698288
• 关键词: Acids; Active Sites; Amino Acids; Androgens; Applications Grants; Bacteria; Bile Acids; Bile fluid; Binding; Biochemical Pathway; Biological Assay; Blood; Chemicals; Chenodeoxycholic Acid; Cholelithiasis; Cholesterol; Cholic Acids; Clinical Research; Clostridium; Colon; Colon Carcinoma; DNA; Data; Deoxycholic Acid; Detection; Development; Diet; Disease; Ecosystem; Enterohepatic Circulation; Enzyme Kinetics; Enzymes; Feces; Future; Gene Expression Profile; Genes; Glucocorticoids; Goals; Growth; Health; Hospitals; Human; Human Microbiome; Hydro-Lyases; Incidence; Individual; Intestines; Laboratories; Lithocholic Acid; Liver; Mammalian Cell; Metabolic Biotransformation; Metabolism; Molecular; Monitor; Oxidoreductase; Pathway interactions; Patients; Physiological; Play; Population; Prostate; Proteins; RNA; Reverse Transcriptase Polymerase Chain Reaction; Risk; Role; Sampling; Secondary to; Site-Directed Mutagenesis; Steroid 17-alpha-monooxygenase; Steroids; Sterols; Substrate Specificity; Techniques; Time; Tissues; Virginia; arm; dehydroxylation; disorder risk; in vivo; inhibitor/antagonist; men; millimeter; mutant; novel; patient population; steroid hormone; three dimensional structure; tool; transcriptome sequencing; tumor growth

DESCRIPTION (provided by applicant): The human colon harbors one of the most densely populated bacterial ecosystems known (>1011 bacteria/g feces). Cholic acid (CA) and chenodeoxycholic acid (CDCA) are primary bile acids synthesized from cholesterol in the liver. Bile acids undergo enterohepatic circulation several times each day. Primary bile acids entering the colon are deconjugated and free bile acids are biotransformed to more than 20 different metabolites by gut bacteria. The major biotransformation is 7¿-dehydroxylation (7¿- DeOH) of CA and CDCA yielding the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA), respectively. Hydrophobic secondary bile acids are highly toxic to mammalian cells and can accumulate to high levels (>70%) in the bile acid pool of some individuals as the human liver cannot 7¿-hydroxylate secondary bile acids. High levels of DCA in blood, bile, and feces have been correlated with an increase risk of colon cancer and cholesterol gallstone disease, in some patients. The formation of secondary bile acids is carried out by a few species of the genus Clostridium and the level of these bacteria in feces is correlated with DCA levels in bile. The biochemical pathway of bile acid 7¿-DeOH has been elucidated by our group. However, many of the genes encoding enzymes in this pathway have not been isolated and characterized nor have the 3D structure of key enzymes in this pathway determined. Some strains of 7¿- dehydroxylating bacteria can convert glucocorticoids into C-19 androgenic compounds and the genes encoding these enzymes have not been isolated. Isolation of these genes is crucial for the development of molecular techniques (RT-PCR) to easily monitor intestinal bile acid and glucocorticoid metabolism and pharmacological or dietary ways to decrease formation of secondary bile acids and C-19 androgenic compounds. Subaim 1A. Identify CA, allo-CA, and glucocorticoid inducible genes from the human bile acid 7¿-dehydroxylating bacterium, Clostridium scindens ATCC 35704, via a wholetranscriptome approach (RNAseq). Subaim 1B. Develop quantitative PCR assays for key genes involved in allo-DCA and C-19 androgen formation. Aim 2. Characterize the allo-CA and glucocorticoid inducible enzymes from Clostridium scindens ATCC 35704 catalyzing the formation of allo-DCA acid and C-19 androgens, respectively. Aim 3: Determine the 3D structure of bile acid 7¿ and 7¿-dehydratases, the rate limiting enzymes in bile acid 7¿/7¿-DeOH, from Clostridium scindens. The results of these studies will give us the tools to carry out clinical studies to determine the most effective ways to decrease DCA in the bile acid pool with the aim of decreasing the risk of colon cancer and cholesterol gallstones, in some patients.

描述（由申请人提供）： 人类结肠是已知细菌最密集的生态系统之一（> 1011 个细菌/克粪便） 胆酸 (CA) 和鹅去氧胆酸 (CDCA) 是由肝脏中的胆固醇合成的初级胆汁酸。每天多次进入结肠的初级胆汁酸被肠道细菌生物转化为 20 多种不同的代谢物。 7° CA 和 CDCA 的脱羟基化 (7´- DeOH) 分别产生次级胆汁酸脱氧胆酸 (DCA) 和石胆酸 (LCA) 疏水性次级胆汁酸对哺乳动物细胞具有剧毒，并且可以积累到高水平 (>70)。 %) 存在于某些个体的胆汁酸库中，因为人类肝脏不能 7¿在一些患者中，血液、胆汁和粪便中高含量的 DCA 与结肠癌和胆固醇胆结石疾病的风险增加相关。梭菌属和粪便中这些细菌的水平与胆汁中 DCA 的水平相关 胆汁酸 7¿ -DeOH 已被我们的小组阐明，但是，该途径中的许多编码酶的基因尚未被分离和表征，也没有确定该途径中的一些关键酶的 3D 结构。 - 脱羟基细菌可以将糖皮质激素转化为 C-19 雄激素化合物，而编码这些酶的基因尚未分离出来，这些基因的分离对于分子技术 (RT-PCR) 的发展至关重要，以轻松监测肠道胆汁酸和糖皮质激素的代谢。减少次级胆汁酸和 C-19 雄激素化合物形成的药物或饮食方法。来自人类胆汁酸7的诱导基因-脱羟基细菌，Clostridium scindens ATCC 35704，通过全转录组方法 (Subaim 1B) 对参与异源 DCA 和 C-19 雄激素形成的关键基因进行定量 PCR 检测。 目标 2. 表征异源 CA 和糖皮质激素。来自 Clostridium scindens ATCC 35704 催化的诱导酶分别形成异源 DCA 酸和 C-19 雄激素 目标 3：确定胆汁酸 7¿ 的 3D 结构。和 7¿ -脱水酶，胆汁酸中的限速酶 7¿ /7¿ -DeOH，来自梭状芽孢杆菌，这些研究的结果将为我们提供进行临床研究的工具，以确定减少胆汁酸库中 DCA 的最有效方法，从而降低结肠癌和胆固醇胆结石的风险，在一些患者中。