Gut microbial metabolites sulfonolipids mediate high fat diet-induced intestinal inflammation

高脂饮食（HFD）改变宿主炎症反应和肠道微生物代谢产物。虽然这些 已经假设代谢物介导宿主肠道炎症，现有的差距是如何确定 从一个极其复杂的代谢物库中提取功能性和负责任的代谢物， 未知的化学物质 我们试图发现这些功能性代谢物，并确定它们在调节HFD诱导的细胞凋亡中的作用。 肠道炎症在我们的初步研究中，我们首先建立了一个小鼠模型， 肠道炎症我们接下来对肠道微生物组进行了比较宏基因组分析， 从上述小鼠中收集，导致鉴定出一个属，Alistipes，其显著增加 在HFD诱导的炎症中。Alistipes主要从临床样品中分离， 对炎症的影响，促使我们研究Alistipes代谢物和 观察到的小鼠模型的肠道炎症。因此，我们开发了互补代谢组学， 基因组挖掘方法：直接显示小鼠粪便和血清样品的代谢组学分析 代谢变化，而基因组挖掘揭示了独特的模式的生物合成基因簇，编码 感兴趣的代谢物。事实上，这两种方法的交叉验证导致了一类罕见的 脂质、磺脂（SL），其在HFD喂养的小鼠样品中显著增加。的潜在 这些SL的生物合成基因也在HFD喂养的小鼠样品中积累。纯SL是 随后分离，通过NMR解析化学结构。然后我们测试了磺胺巴星A， RT-PCR结果显示，该菌株为分离的SL的一员，并且它确实诱导了巨噬细胞RAW264.7炎症反应 和ELISA分析。所有这些初步数据表明，肠道微生物代谢产物SL介导HFD诱导的 肠道炎症 有趣的是，SL在结构上模拟人内源性鞘脂（SP），已知后者介导 炎症此外，肠道微生物群的一个属类杆菌也产生SP，但不产生SL。类杆菌衍生的 最近研究表明，SPs可进入宿主的代谢，对维持肠道内环境稳定至关重要 和共生。综上所述，这提出了一个有趣的假设，SL可能直接诱导 炎症，而且还可以通过影响SL和SP的肠内稳态来调节炎症。 因此，我们现在建立明确的建立，在体外和体内，SL在介导HFD诱导的作用， 肠道炎症，强调SL和SP之间的潜在关系。这一目标 将通过完成以下具体目标（SA）来实现。 SA 1：表征微生物SL、微生物SP和宿主内源性SP的HFD相关表达。 SA 2：采用体外实验和免疫组化方法研究SL和SP在肠道炎症中的活性及其相互关系。 测定和体内无菌小鼠模型。在体外和体内，SL在介导HFD诱导的肠上皮细胞凋亡中的作用， 炎症，强调SL和SP之间的潜在关系。这一目标将得以实现 通过完成以下具体目标（SA）。

High fat diets (HFDs) alter both host inflammatory responses and gut microbial metabolites. While these metabolites have been hypothesized to mediate host intestinal inflammation, an existing gap is how to pinpoint the functional and responsible metabolites from an extremely complicated metabolites pool that contains numerous unknown chemicals. We seek to discover such functional metabolites and establish their role in modulating HFDs-induced intestinal inflammation. In our preliminary study, we first established a mouse model that displayed HFDsinduced intestinal inflammation. We next performed comparative metagenomic analysis of the gut microbiome collected from aforementioned mice, leading to identification of a genus, Alistipes, which was significantly increased during HFDs-induced inflammation. Alistipes is isolated primarily from clinical samples and shows emerging implications to inflammation, motivating us to investigate the potential links between Alistipes metabolites and the observed intestinal inflammation of our mouse model. Thus, we developed complementary metabolomics and genome mining approaches: metabolomic analysis of the mice fecal and serum samples directly displayed metabolic changes while genome mining revealed unique patterns of biosynthetic gene clusters that encode the metabolites of interests. Indeed, the cross-validation of these two approaches led to the discovery of a class of rare lipids, sulfonolipids (SLs) which were significantly increased in the HFDs-fed mice samples. The potential biosynthetic genes of these SLs were also accumulated in the HFDs-fed mice samples. The pure SLs were subsequently isolated, with the chemical structures elucidated by NMR. We then tested sulfobacin A, a major member of the isolated SLs, and it indeed induced macrophage RAW264.7 inflammatory responses by RT-PCR and ELISA analyses. All these preliminary data suggest that gut microbial metabolites SLs mediate HFDsinduced intestinal inflammation. Intriguingly, SLs structurally mimic human endogenous sphingolipids (SPs), with the latter known to mediate inflammation. In addition, a genus of gut microbiota, bacteroides, also produces SPs but not SLs. The bacteroidesderived SPs were recently shown to enter hosts’ metabolism and are critical for maintaining intestinal homeostasis and symbiosis. Taken together, this raises an interesting hypothesis that SLs may directly induce inflammation, but also may modulate inflammation by affecting intestinal homeostasis of SLs and SPs. Thus, we are now set up to unambiguously establish, both in vitro and in vivo, the role of SLs in mediating HFDsinduced intestinal inflammation, with an emphasis on the potential relationship between SLs and SPs. This goal will be achieved through completion of the following Specific Aims (SA). SA 1: Characterizing the HFDs-associated expression of microbial SLs, microbial SPs and host endogenous SPs. SA 2: Investigate the activities and relationship of SLs and SPs in mediating intestinal inflammation, using both invitro assays and in vivo germ-free mouse models. in vitro and in vivo, the role of SLs in mediating HFDs-induced intestinal inflammation, with an emphasis on the potential relationship between SLs and SPs. This goal will be achieved through completion of the following Specific Aims (SA).