MECHANISMS OF ALTERATION OF GASTROINTESTINAL MOTILITY BY GUT MICROBIOTA

摘要 人类肠道中含有数万亿的微生物，这些微生物通过收获营养/能量而使宿主受益 我们饮食中不易消化的成分。值得注意的是，微生物和 它们的人类宿主以及对正常生理功能的影响仍然知之甚少。 胃肠道（GI）运动和肠道微生物群明显相关，环境因素包括 饮食，可以改变胃肠道运动和肠道微生物群之间的关系。血清素（5-羟色胺; 5-羟色胺） 肠嗜铬细胞（EC）释放的HT作为一种重要的旁分泌信使，参与 运动和感觉转导调节GI运动。我的初步研究表明 作为肠道微生物群靶点的β-胡萝卜素能途径。我的总体假设是肠道微生物群改变了GI 通过释放影响肠道的特定代谢物（包括色胺）以饮食依赖性方式进行运动 肾上腺素能途径。我将使用无菌（GF），gnotobiotic（定义/简化的微生物群）和人源化 （由人源微生物定殖的ex-GF）小鼠，以解决人肠道微生物对小鼠的生理作用。 小鼠模型中的宿主。由于GF小鼠完全缺乏微生物群，因此它们可以被特定的微生物群定植 细菌群落来创造不同的殖民状态。在具体目标1中，我将探讨 在GF和人源化小鼠中，微生物群对肠道益生菌能途径的影响。在具体目标2中，我将确定 降低膳食多糖的复杂性对GI运动的不同影响， 在肠道菌群中。最后，在具体目标3中，我将研究微生物代谢物如色胺的作用 调节5-HT生物合成和调节GI运动。我已经开发了体外（器官浴）和体内 体内（结肠测压）生理技术以及使用EC样细胞系的筛选策略， 用超高效液相色谱法检测代谢产物对5-HT合成和释放的影响 色谱法与质谱联用。我以前的研究训练是在胃肠道生理学描绘 调节胃肠道运动的复杂机制，以及我最近在微生物生态学方面的训练，因为它涉及到 宿主功能，沿着我在胃肠病学的临床训练，特别关注GI动力障碍， 让我有能力解决这些生物学上合理的和临床上相关的问题。这个职业 发展奖将使我联合收割机结合我的技能在两个非常不同的研究领域， 神经胃肠病学和微生物生态学，以解决人类生物学的重要方面。我的导师 团队由马约诊所的Gianrico Farrugia博士和斯坦福大学的Justin Sonnenburg博士组成; 这两所大学在研究领域都享有国际声誉，在培训方面也有成功的记录。 年轻的教师Gianrico Farrugia博士是神经胃肠病学的国际领导者， 在阐明Cajal间质细胞在胃肠动力障碍中的作用方面的贡献。他的长期记录 31名研究员的辅导证明辅导工作取得了成功。索南伯格博士有进化论的思想 他是一位糖生物学家，因其在肠道碳水化合物利用方面的开创性工作而享誉国际 微生物和gnotobiotic小鼠模型的应用，以了解肠道微生物的相互作用。 他们的专业知识对这个跨学科项目将是无价的。

Abstract The human gut harbors trillions of microorganisms that benefit the host by enabling harvest of nutrients/energy from otherwise indigestible components of our diet. Remarkably, the complex signaling between microbes and their human host, and the resulting impact on normal physiological functions, are still poorly understood. Gastrointestinal (GI) motility and the gut microbiota are clearly associated and environmental factors, including diet, can modify the relationship between GI motility and the gut microbiota. Serotonin (5-hydroxytryptamine; 5- HT) released from the enterochromaffin (EC) cells serves as an important paracrine messenger involved in motor and sensory transduction modulating GI motility. My preliminary studies strongly suggest the gut serotonergic pathway as a target for gut microbiota. My overall hypothesis is that gut microbiota alters GI motility in diet-dependent manner by release of specific metabolites, including tryptamine, which affect the gut serotonergic pathway. I will use germ-free (GF), gnotobiotic (defined/simplified microbiota), and humanized (ex-GF colonized by human-derived microbes) mice to address physiological effects of human gut microbes on the host in a mouse model. As GF mice completely lack microbiota they can be colonized with defined communities of bacteria to create distinct states of colonization. In specific aim 1, I will explore the effect of microbiota on the gut serotonergic pathway in GF and humanized mice. In specific aim 2, I will determine the differential effect on GI motility of decreasing the complexity of dietary polysaccharides with resulting alteration in gut microbiota. Finally, in specific aim 3, I will investigate the role of microbial metabolites such as tryptamine in modulating 5-HT biosynthesis and modulating GI motility. I have developed both ex vivo (organ bath) and in vivo (colonic manometry) physiological techniques as well as a screening strategy to use EC-like cell lines to test metabolites for their effect on synthesis and release of 5-HT using ultra performance liquid chromatography coupled with mass spectrometry. My previous research training in GI physiology delineating complex mechanisms regulating GI motility, as well as my recent training in microbial ecology as it relates to host function, along with my clinical training in Gastroenterology with a specific focus on GI motility disorders, gives me the ability to address these biologically sound and clinically relevant questions. This career development award will allow me to combine my skills in two very distinct areas of research, Neurogastroenterology and Microbial Ecology, to address important aspects of human biology. My mentorship team is comprised of Dr. Gianrico Farrugia at Mayo Clinic and Dr. Justin Sonnenburg at Stanford University; both are internationally renowned in their areas of research and have a successful track record in training young faculty. Dr. Gianrico Farrugia is an international leader in Neurogastroenterology, having made seminal contributions in elucidating roles of interstitial cells of Cajal in GI motility disorders. His long record of successful mentorship is evidenced by mentorship of 31 fellows. Dr. Sonnenburg is an evolutionary minded glycobiologist who is internationally renowned for his ground-breaking work on carbohydrate utilization by gut microbes and the application of gnotobiotic mouse models to understanding microbial interactions in the gut. Both of their expertise will be invaluable for this cross-disciplinary project.