MECHANISMS OF ALTERATION OF GASTROINTESTINAL MOTILITY BY GUT MICROBIOTA

描述（由申请人提供）：人体肠道中有数万亿微生物，通过从我们饮食中其他不可消化的成分中获取营养/能量，从而使宿主受益。值得注意的是，微生物和人类宿主之间的复杂信号，以及由此产生的对正常生理功能的影响，仍然知之甚少。胃肠道（GI）运动与肠道微生物群之间存在明显的相关性，包括饮食在内的环境因素可以改变胃肠道运动与肠道微生物群之间的关系。肠染色质（EC）细胞释放的5-羟色胺（5-羟色胺；5- HT）是一种重要的旁分泌信使，参与调节胃肠道运动的运动和感觉转导。我的初步研究强烈表明肠道血清素能途径是肠道微生物群的目标。我的总体假设是，肠道微生物群通过释放特定代谢物（包括影响肠道血清素能途径的色胺），以饮食依赖的方式改变胃肠道运动。我将在小鼠模型中使用无菌（GF）、非微生物（定义/简化的微生物群）和人源化（由人类来源的微生物定植的前GF）小鼠来研究人类肠道微生物对宿主的生理影响。由于GF小鼠完全缺乏微生物群，它们可以被确定的细菌群落定植，以创造不同的定植状态。在具体目标1中，我将探讨微生物群对GF和人源化小鼠肠道血清素能通路的影响。在具体目标2中，我将确定降低膳食多糖的复杂性对胃肠道运动的不同影响，从而导致肠道微生物群的改变。最后，在具体目标3中，我将研究微生物代谢物（如色胺）在调节5-羟色胺生物合成和调节胃肠道运动中的作用。我开发了离体（器官浴）和体内（结肠测压）生理技术，以及一种筛选策略，使用ec样细胞系测试代谢物对5-羟色胺合成和释放的影响，使用超高效液相色谱和质谱联用。我之前在胃肠道生理学方面的研究训练描述了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培训，因为它与宿主功能有关，以及我在胃肠病学方面的临床培训，特别关注胃肠道运动障碍，使我有能力解决这些生物学上健全和临床相关的问题。这个职业发展奖将使我能够结合我在两个非常不同的研究领域的技能，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。我的指导团队由梅奥诊所的吉安里科·法鲁吉亚博士和斯坦福大学的贾斯汀·索南伯格博士组成；两所大学都在各自的研究领域享有国际声誉，并在培养年轻教师方面有着成功的记录。Gianrico Farrugia博士是国际神经胃肠病学的领导者，在阐明Cajal间质细胞在胃肠道运动障碍中的作用方面做出了开创性的贡献。他长期成功的指导记录是由31名研究员的指导证明。Sonnenburg博士是一位具有进化思想的糖生物学家，因其在肠道微生物对碳水化合物利用的开创性工作以及应用非生物小鼠模型来理解肠道微生物相互作用而享誉国际。他们两人的专业知识对这个跨学科项目都是非常宝贵的。

DESCRIPTION (provided by applicant): 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 gu microbiota. Finally, in specific aim 3, I will investigate the role of microbial metabolites such a 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 succesful 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.