The Influence of the Glucoamylase Inhibitor Acarbose on Bacteroidetes Starch Utilization and Fitness in the Human Gut

摘要 阿卡波糖是FDA批准的一种给2型糖尿病患者开出的药物，可以抑制宿主葡萄糖淀粉酶， 上胃肠道中负责将淀粉分解成葡萄糖的酶。因此，它 缓解餐后高血糖，有助于改善血糖控制。然而，阿卡波糖显示 由于其免疫调节和促进作用，有望改善许多其他疾病的症状。 对心血管的影响。尽管阿卡波糖有可能被重新用于治疗各种疾病，但几乎没有 知道它是如何引起这些宿主效应的。一种解释在于观察到阿卡波糖改变了 小鼠和人类的肠道微生物群落。尽管如此，还没有发表的报告提供机械式的见解 这些变化。由于阿卡波糖处理后较少的淀粉在上消化道中被消化，因此它通过 到大肠，在那里通过共生将其加工和发酵成短链脂肪酸(SCFA) 细菌。由于阿卡波糖被寄主最小限度地吸收，它很可能随淀粉一起转移到大的 在肠道中，它可能会影响用于处理这种多糖的细菌糖淀粉酶。最新数据 提示普通人类肠道定植细胞对阿卡波糖的体外生长敏感性显著不同 当利用淀粉作为碳源时。一种优势的和研究得很好的肠道门，拟杆菌，部署 一种淀粉利用系统，或称SU，用于识别、加工和进口淀粉，其原型系统来自 拟杆菌Tetaiotaomicron为模型。该提案的初步工作调用了完全不同的表型 在两个重要的拟杆菌种之间：B.thetaiotaomicron对阿卡波糖敏感，而 卵形拟杆菌属耐药菌株。这一提议将确定这些不同反应的分子基础 并验证SUS的离散分子特征对不同的类杆菌生长有贡献的假设 在ACA存在的情况下抑制和全面适应。目标1将系统地测试 阿卡波糖不同程度地影响苏氨酸酶抑制和寡糖识别和/或转运。目标2 将确定阿卡波糖敏感性在拟杆菌中的分布情况。阿卡波糖体外试验 表型将通过挖掘元基因组数据集与体内适应度和相对丰度进行比较 人类。这两种方法的结合将检验这样一种概念，即在体外对阿卡波糖的敏感性转化为 肠道细菌适合性降低。鉴于最近的工作表明，拟议的研究是及时的 阿卡波糖可能会由于微生物区系介导的胆酸池改变而影响小鼠全身信号转导。 最近的数据还表明，阿卡波糖可能是一种有用的工具来控制肠道中类杆菌的数量，一种 与多种疾病的病因有关的门。由于阿卡波糖对宿主健康有积极影响，因此 从机理上理解阿卡波糖如何影响胃肠道细菌的生长是有必要的，也将会 为设计其他具有比阿卡波糖更强或更定制效果的外源物质奠定了基础。

ABSTRACT Acarbose is an FDA approved medication prescribed to type 2 diabetics and inhibits host glucoamylases, enzymes along the upper gastrointestinal tract responsible for breaking down starch into glucose. As such, it mitigates hyperglycemia after meals and contributes to improved glycemic control. However, acarbose shows promise for ameliorating symptoms in a number of other diseases because of its immunomodulatory and pro- cardiovascular effects. Despite the prospect of re-purposing acarbose to treat a variety of conditions, little is known about how it elicits these host effects. One explanation lies in the observation that acarbose alters the gut microbial community in mice and humans. Still, there are no published reports offering mechanistic insight into these changes. Because less starch is digested in the upper GI tract upon acarbose treatment, it transits to the large intestine where it is processed and fermented into short-chain fatty acids (SCFA) by commensal bacteria. Since acarbose is minimally absorbed by the host, it likely transits with the starch to the large intestine where it might impact bacterial glucoamylases utilized to process this polysaccharide. Recent data suggest that common human gut colonizers exhibit remarkably different growth sensitivities to acarbose in vitro when utilizing starch as a carbon source. A dominant and well-studied gut phylum, the Bacteroidetes, deploys a starch utilization system, or Sus, to recognize, process, and import starch, with the prototypical system from Bacteroides thetaiotaomicron serving as a model. Initial work for this proposal invokes disparate phenotypes between two prominent species of Bacteroidetes: B. thetaiotaomicron is sensitive to acarbose while Bacteroides ovatus is resistant. This proposal will determine the molecular basis for these distinct responses and test the hypothesis that discrete molecular features of Sus contribute to differential Bacteroidetes growth inhibition and overall fitness in the presence of ACA. Aim 1 will systematically test the possibilities that acarbose differentially affects Sus enzyme inhibition and oligosaccharide recognition and/or transport. Aim 2 will determine how widespread acarbose sensitivity is amongst the Bacteroidetes. In vitro acarbose phenotypes will be compared to in vivo fitness and relative abundances by mining metagenomic data-sets from humans. The combination of approaches will test the notion that in vitro sensitivity to acarbose translates to reduced bacterial fitness in the gut. The proposed research is timely in light of recent work suggesting that acarbose may influence whole body signaling in mice due to microbiota mediated alterations in bile acid pools. Recent data also suggests that acarbose may be a useful tool to control Bacteroidetes abundance in the gut, a phylum implicated in the etiology of numerous diseases. Because acarbose positively impacts host health, a mechanistic understanding of how acarbose influences bacterial growth in the GI tract is warranted and will lay a foundation for the design of other xenobiotics with even stronger, or more tailored effects, than acarbose.