Mechanisms of alteration of GI physiology by gut microbes

摘要 我们实验室研究的总体目标是 确定肠道微生物群及其 产品改变胃肠道（GI）腔生理学， 开发基于微生物群的治疗方法 治疗肠易激综合征（IBS）等疾病的生理学改变， 肠道菌群的改变。我们的初步研究已经确定了色氨酸脱羧酶基因， 在普通人类肠道细菌如瘤胃球菌中将膳食色氨酸转化为色胺 gavus和生孢梭菌。此外，我们的初步数据表明，色胺增加短， 在Ussing中，体外结肠上皮的回路电流（代表离子通量;分泌的替代物） 这种作用可以被5-羟色胺受体4（5 HT 4 R）拮抗剂抑制，并且在 5 HT 4 R敲除小鼠。有趣的是，带有色氨酸脱羧酶基因的基因工程细菌 当饮食中补充以下物质时，在gnotobiotic小鼠体内产生色胺并加速整个肠道运输 色氨酸我们的总体假设是，饮食色氨酸驱动的细菌色胺的产生增加， 5 HT 4 R介导的肠道分泌调节健康和疾病中的GI功能。为了确定 为了确定色胺的作用机制，我们将首先确定外源性色胺对肠上皮细胞的影响， 分泌依赖于5 HT 4 R，并确定负责分泌的特定下游途径。我们将 然后研究了色氨酸对细菌产生色胺和5-HT 4 R介导的 肠分泌和全肠转运以及其在便秘临床前模型中的应用。的 这项研究的结果将有助于开发新的工程益生菌， 产生生物活性代谢物如色胺以纠正改变的生理学如便秘， IBS等疾病。

ABSTRACT The overall goal of our laboratory's research is to determine the mechanisms by which gut microbiota and their products alter gastrointestinal (GI) tract luminal physiology and to develop microbiota-based therapeutic manipulations to correct altered physiology in diseases like irritable bowel syndrome (IBS) associated with alterations in gut microbiota. Our preliminary studies have identified the gene tryptophan decarboxylase which converts dietary tryptophan to tryptamine in common human gut commensal bacteria like Ruminococcus gnavus and Clostridium sporogenes. Furthermore our preliminary data show that tryptamine increases short circuit current (representing ionic flux; surrogate for secretion) across the colonic epithelium in vitro in Ussing chamber studies and this effect can be inhibited by serotonin receptor4 (5HT4R) antagonists and is absent in 5HT4R knock out mice. Interestingly genetically engineered bacteria with the gene tryptophan decarboxylase produce tryptamine in vivo in gnotobiotic mice and accelerate whole gut transit, when diet is supplemented with tryptophan. Our overall hypothesis is that dietary tryptophan driven production of bacterial tryptamine increases 5HT4R-mediated intestinal secretion modulating GI function in health and disease. In order to determine the mechanism of action of tryptamine we will first determine if the effect of exogenous tryptamine on intestinal secretion is dependent on 5HT4R and identify specific downstream pathways responsible for secretion. We will then investigate the effect of dietary tryptophan on bacteria produced tryptamine and 5HT4R mediated intestinal secretion and whole gut transit as well as its application in a preclinical model of constipation. The results from this study will potentially contribute to the development of novel engineered probiotics capable of producing a bioactive metabolite such as tryptamine to correct the altered physiology such as constipation in diseases like IBS.