Creating a toolkit to measure in vivo bile acid transport

描述(申请人提供)：肠道功能障碍可能损害BA的摄取和对肝脏胆汁酸(BA)合成的反馈抑制，从而导致BA吸收不良(BAM)。粪便中BAS增多会促进结肠病理；霍乱腹泻，可能还会出现肿瘤。肠道BA摄取主要由回肠顶端钠依赖的胆汁酸转运蛋白(ASBT；SLC10A2)介导。ASBT功能降低会减少BA的吸收；Asbt基因缺失的小鼠粪便中BA含量增加。在原代BAM中，肠成纤维细胞生长因子19(FGF19)抑制的反馈抑制增加了BA的合成，并且肠道BA水平超过了BA转运蛋白的能力。Fgf15基因缺失的小鼠类似于原发的BAM；它们的粪便Ba也增加了。我们最近发表的体外和电子计算机数据表明，常用药物，包括他汀类药物，抑制ASBT功能。如果药物在体内损害了ASBT的功能，BA转运的改变可能会导致意想不到的副作用，包括结肠病理。目前用来测量BA在体内转运和分布的工具有限。为了弥补这一局限性，我们设想了一种在活体动物中使用质子(1H)-氟(19F)磁共振成像(MRI)的创新方法；这是一种具有临床应用潜力的新方法。R21资金将支持一个唯一有资格使用生化方法和活体动物核磁共振来创造和测试(体外和体内)多氟、非放射性(19F)BA(MFBA)的研究团队：研究BA对结肠上皮影响的专家Raufman博士；测量BA体外转运的专家Polli博士；测量BA在体内转运的专家Dawson博士；开发19F成像示踪剂(19FIT)的专家化学家Yu博士；以及小型动物MRI专家徐博士。我们将设计、创建和测试两类19F标记的试剂：(1)由ASBT结合和运输的MFBA[例如，具有三个19F原子/分子的19F标记鹅去氧胆酸(19F3-CDCA)]和(2)既不结合也不运输的非活性控制剂(例如19FIT)。为了实现这些目标，我们提出了两个具体的目标：1.创建多氟化BA并测试其体外稳定性和与肠溶BA的相互作用 传送者。&gt；2.WT，Slc10a2-/-中多氟BA的体内稳定性和转运试验 和Fgf15-/-小鼠使用生化方法和活体动物磁共振成像。我们的多学科团队包括在测量胆汁酸转运方面拥有无可置疑的专业知识的资深研究人员。这个团队是唯一有资格开发这项创新技术的人，该技术基于对新创建的非放射性氟标记胆汁酸的磁共振成像，可以用来获得关于活体动物和人类胆汁酸运输的时间和空间信息。 与公共健康相关：除了作为促进脂肪吸收的洗涤剂的传统角色外，胆汁酸还是影响多个器官的强有力的信号分子；它们调节肠道运动和激素产生、结肠生理和癌症易感性，并改变血管张力、葡萄糖代谢、脂肪代谢和能量利用。为了了解胆汁酸的这些复杂作用，需要一种新的技术来同时监测胃肠道和代谢组织中的胆汁酸水平。在这项R21应用中，我们建议开发一种创新技术，该技术基于新创建的非放射性氟标记胆汁酸的磁共振成像，可用于获取活体动物和人类的时间和空间信息。

DESCRIPTION (provided by applicant): Intestinal dysfunction may impair BA uptake and feedback inhibition of hepatic bile acid (BA) synthesis, thereby resulting in BA malabsorption (BAM). Increased fecal BAs promote colon pathology; cholerrheic diarrhea and possibly neoplasia. Intestinal BA uptake is mediated primarily by the ileal Apical Sodium-dependent Bile Acid Transporter (ASBT; SLC10A2). Reduced ASBT function decreases BA absorption; Asbt-null mice have increased fecal BAs. In primary BAM impaired feedback inhibition by intestinal fibroblast growth factor-19 (FGF19) increases BA synthesis and intestinal BA levels overwhelm BA transporter capacity. Fgf15-null mice mimic primary BAM; they also have increased fecal BAs. Our recently published in vitro and in silico data indicate that commonly-used drugs, including statins, inhibit ASBT function. If drugs impair ASBT function in vivo, altered BA transport may result in unanticipated side-effects, including colon pathology. Current tools to measure BA transport and distribution in vivo are limited. To remedy this limitation, we conceived an innovative approach in live animals that utilizes combined proton (1H)-fluorine (19F) magnetic resonance imaging (MRI); a novel methodology with translational potential for clinical practice. R21 funding will support a research team uniquely qualified to create and test (in vitro and in vivo) multi-fluorinated, non-radioactive (19F) BAs (MFBA) using biochemical methods and live animal MRI: Dr. Raufman, an expert in BA effects on colon epithelium; Dr. Polli, an expert in measuring BA transport in vitro; Dr. Dawson, an expert in measuring BA transport in vivo; Dr. Yu, an expert chemist who developed 19F-imaging tracer (19FIT); and Dr. Xu, an expert in small animal MRI. We will design, create and test two classes of 19F-labeled agents: (1) MFBA that are bound and transported by ASBT [e.g. 19F-labeled chenodeoxycholic acid (19F3-CDCA) with three 19F atoms/molecule] and (2) Inactive control agents neither bound nor transported by ASBT (e.g. 19FIT). To accomplish these goals, we propose two Specific Aims: > 1. Create multi-fluorinated BAs and test in vitro stability and interaction with enteric BA transporters. > 2. Test in vivo stability and transport of multi-fluorinated BAs in WT, Slc10a2- /- and Fgf15-/- mice using biochemical methods and live-animal magnetic resonance imaging. Our multidisciplinary team includes established investigators with unquestioned expertise in measuring bile acid transport. This team is uniquely qualified to develop this innovative technology based on magnetic resonance imaging of newly-created non-radioactive, fluorine-labeled bile acids that can be used to obtain both temporal and spatial information on bile acid transport in live animals and humans. PUBLIC HEALTH RELEVANCE: In addition to their traditional role as detergents that facilitate fat absorption, bile acids are potent signaling molecules that affect multiple organs; they modulate gut motility and hormone production, colon physiology and cancer susceptibility, and alter vascular tone, glucose metabolism, lipid metabolism and energy utilization. To understand these complex actions of bile acids new technology is required that permits simultaneous monitoring of bile acid levels in the gastrointestinal tract and metabolic tissues. In this R21 application, we propose to develop an innovative technology based on magnetic resonance imaging of newly-created non- radioactive fluorine-labeled bile acids that can be used to obtain both temporal and spatial information in live animals and humans.