Contribution of sweet taste receptors (STRs) to saccharin-induced alterations of gut microbiota

项目摘要 甜味受体（STR）在包括胃肠道在内的多种组织中表达。肠 STR在调节糖和无热量人工甜味剂摄入的代谢反应中发挥作用 （NCAS）。奇怪的是，NCAS的消费与代谢失调和肥胖有关， 组织不代谢这些营养物。导致这些疾病的潜在病理生理机制 这些观察结果在很大程度上是未知的，但有人认为，NCAS的摄入会改变肠道微生物群 导致葡萄糖耐受不良考虑到肠道中STR介导的化学感觉可能与胃肠道的化学感觉有关， NCAS的代谢效应，我们假设肠道STR提供了NCAS- 导致代谢功能障碍和肠道微生物群。为此，我们证明了STR信号的消除 在小鼠中，通过基因切除T1 R2蛋白（T1 R2敲除; KO）， 由于过量摄入糖精而引起的精神错乱。值得注意的是，基础（普通饮食）T1 R2-KO肠道微生物群 与T1 R2-野生型（WT）相比，组合物显示出显著的改变，随后是升高的浓度 粪便短链脂肪酸（SCFAs）。这些变化在属（梭菌属、拟杆菌属）中最为显著 和Blautia），其已知影响宿主代谢并且与人类肠道微生物群有关。最后为 开始解决肠道STR在人类中的直接作用，我们测试了急性药理学作用， 抑制（lactisole）的STR在肠道，并发现它改变了血糖和胰岛素的反应，以口服 葡萄糖负荷总之，这些数据强调了我们研究的转化影响，并表明， 涉及STR的化学感觉输入可能与营养代谢和代谢性疾病的发展有关。 疾病因此，我们提出了全面的研究，调查在NCAS诱导的STR的贡献， 葡萄糖耐受不良我们将探索与肠道微生物群和葡萄糖相关的潜在致病机制 肠细胞中的转运/代谢。我们将进行a）定性系统发育（16 S rDNA）和元基因组分析 B）体内代谢谱和能量谱的评估 平衡，c）评估肠上皮和粪便SCFA的靶向代谢物，和d）离体 肠葡萄糖转运的评估（Ussing Chamber）。我们预期STR介导的化学感受性 信号传导与肠道微生物群相互作用以改变肠道的吸收能力， NCAS诱导的葡萄糖调节异常的发展。最后，为了建立宿主微生物群之间的因果关系， 途径，我们将常规无菌小鼠与微生物群从T1 R2-KO小鼠经历NCAS 喂食拟议的研究将a）探索新的宿主化学感受机制与肠道的相互作用 微生物群，B）确定肠道中STR的作用，以及c）确定将NCAS联系起来的致病机制 消耗和代谢性疾病的发展。了解这些监管的性质 这些机制可能导致用于治疗代谢疾病的肠道限制性治疗干预。

PROJECT SUMMARY Sweet taste receptors (STRs) are expressed in a variety of tissues including the gastrointestinal tract. Intestinal STRs play a role regulating metabolic responses to the ingestion of sugars and non-caloric artificial sweeteners (NCASs). Paradoxically, consumption of NCASs is associated with metabolic dysregulation and obesity although the tissues do not metabolize these nutrients. The underlying pathophysiological mechanisms responsible for these observations are largely unknown, but it has been suggested that NCAS consumption alters gut microbiota to cause glucose intolerance. Considering that STR-mediated chemosensation in the gut is likely relevant to the metabolic effects of NCASs, we hypothesize that intestinal STRs provide a mechanistic link between NCAS- induced metabolic dysfunction and gut microbiota. Towards this end, we show that elimination of STR signaling in mice, through genetic ablation of the T1R2 protein (T1R2-knock out; KO), protects against metabolic derangements induced by the overconsumption of saccharin. Notably, basal (chow diet) T1R2-KO gut microbiota composition displays marked alterations compared to T1R2-wild type (WT), followed by elevated concentrations of fecal short-chain fatty acids (SCFAs). These changes are most notable in genera (Clostridium, Bacteroides and Blautia) that are known to influence host metabolism and are pertinent to human gut microbiota. Finally, to begin addressing the direct role of intestinal STRs in humans, we tested the effects of acute pharmacological inhibition (lactisole) of STRs in the gut and found that it alters the glycemic and insulin response to an oral glucose load. Taken together, these data emphasize the translational impact of our studies and suggest that chemosensory input involving STRs is likely relevant to nutrient metabolism and the development of metabolic diseases. Thus, we propose comprehensive studies that investigate the contribution of STRs in NCAS-induced glucose intolerance. We will explore potential causative mechanisms associated with gut microbiota and glucose transport/metabolism in enterocytes. We will perform a) qualitative phylogenetic (16S rDNA) and meta-genomic sequencing (RNA-Seq) analyses of gut microbiota, b) assessment of in vivo metabolic profiling and energy balance, c) assessment of targeted metabolites of intestinal epithelium and fecal SCFAs, and d) ex vivo assessment of intestinal glucose transport (Ussing Chamber). We expect that STR-mediated chemosensory signaling interacts with gut microbiota to alter the absorptive capacity of the gut and it is required for the development of glucose dysregulation induced by NCASs. Finally, to establish causality between host-microbiota pathways, we will conventionalize germ-free mice with microbiota from T1R2-KO mice subjected to NCAS feeding. The proposed studies will a) explore interactions of novel host chemosensory mechanisms with gut microbiota, b) define the role of STRs in the gut, and c) identify causative mechanisms that link NCAS consumption and the development of metabolic diseases. Understanding the nature of these regulatory mechanisms could lead to gut-restricted therapeutic interventions for the treatment of metabolic diseases.