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）： 人类结肠是已知的最垂直的细菌生态系统之一（> 1011细菌/g粪便）。胆酸（Ca）和氯氧化胆酸（CDCA）是肝脏中胆固醇合成的原代胆汁酸。胆汁酸每天几次经历肠肝循环。进入结肠的原发性胆汁酸是脱缀合的，肠道细菌将游离胆汁酸生物转化为20多种不同的代谢产物。 CA和CDCA的主要生物转化分别为7 - 二羟基化（7¿-deOH），得出二胆酸脱氧胆酸（DCA）和岩性酸（LCA）。疏水次级胆汁酸对哺乳动物细胞有剧毒，并且可以在某些个体的胆汁酸库中积聚到高水平（> 70％），因为人肝不能7-羟基二胆酸。某些患者的血液，胆汁和粪便中高水平的DCA与结肠癌和胆固醇胆结石疾病的风险增加有关。次生胆汁酸的形成是由几种梭状芽胞杆菌的几种物种进行的，粪便中这些细菌的水平与胆汁中的DCA水平相关。胆汁酸7 - deOH的生化途径已被我们的组阐明。但是，在该途径中编码酶的许多基因尚未分离和表征，也没有确定键酶的3D结构。 7-的某些菌株 - 脱氢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。这些基因的分离对于开发分子技术（RT-PCR）至关重要，以轻松监测肠道胆汁酸和糖皮质激素的代谢以及药物或饮食方法，以减少次级胆汁酸和C-19雄激素化合物的形成。 Subaim 1A。通过holetrantriptome方法（RNASEQ），从人胆汁酸7 - 二羟基化细菌，梭状芽孢杆菌35704的CA，Allo -Ca和糖皮质激素诱导基因，替代细菌，梭状芽胞杆菌的ATCC 35704。 Subaim 1B。开发针对Allo-DCA和C-19雄激素形成的关键基因的定量PCR分析。 AIM 2。表征来自梭状芽胞杆菌ATCC梭状芽胞杆菌ATCC 35704的Allo-Ca和糖皮质激素诱导酶，分别催化了Allo-DCA酸和C-19的形成。 AIM 3：确定胆汁酸7和7-脱水酶的3D结构，从梭状芽胞杆菌综合征中限制胆汁酸7？ /7 - deOH的速率。这些研究的结果将为我们提供临床研究的工具，以确定降低胆汁酸库中DCA的最有效方法，以降低某些患者的结肠癌和胆固醇胆结石的风险。