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

高脂饮食会改变宿主的炎症反应和肠道微生物代谢产物。而这些 代谢物已被假设为介导宿主肠道炎症，现有的差距是如何准确定位 来自极其复杂的代谢物池的功能性和负责任的代谢物，其中包含许多 未知的化学物质。 我们试图发现这种功能代谢物，并确定它们在调节HFDs诱导中的作用。 肠道发炎。在我们的初步研究中，我们首先建立了一个显示HFD诱导的小鼠模型 肠道发炎。接下来，我们对肠道微生物组进行了比较元基因组分析。 从上述小鼠中收集的，导致鉴定出一个属，泽泻属，显著增加 在HFDs诱导的炎症过程中。泽泻属主要是从临床样本中分离出来的，并显示出 对炎症的影响，促使我们研究泽泻代谢产物与炎症的潜在联系 我们所观察到的小鼠模型的肠道炎症。因此，我们发展了互补代谢组学和 基因组挖掘方法：直接展示小鼠粪便和血清样本的代谢组学分析 代谢变化的同时，基因组挖掘揭示了生物合成基因簇的独特模式，这些基因簇编码 利益的代谢物。事实上，这两种方法的交叉验证导致了一类罕见的 脂类、磺脂(SLS)，在喂食HFDs的小鼠样本中显著增加。潜力 这些SLS的生物合成基因也在喂食HFDS的小鼠样本中积累。纯SLS是 随后进行了分离，其化学结构经核磁共振确证。然后我们测试了硫杆菌A，一种主要的 分离的SLS的成员，并通过RT-PCR确实诱导巨噬细胞RAW264.7炎症反应 和酶联免疫吸附分析。所有这些初步数据表明，肠道微生物代谢产物SLS介导了HFD的诱导 肠道发炎。 有趣的是，SLS在结构上模仿人类内源性鞘脂(SPS)，后者是已知的中介 发炎。此外，肠道微生物群的一个属--类杆菌--也产生SPS，但不产生SLS。衍生的类细菌 最近发现SP可以进入宿主的新陈代谢，对维持肠道内环境的稳定至关重要 和共生。综上所述，这提出了一个有趣的假设，即SLS可能直接导致 炎症，但也可能通过影响SLS和SPS的肠道内稳态来调节炎症。 因此，我们现在在体外和体内都明确地建立了SLS在介导HFD诱导的作用中的作用 肠道炎症，重点是SLS和SPS之间的潜在关系。这个目标 将通过完成以下具体目标(SA)来实现。 SA 1：表征微生物SLS、微生物SPS和宿主内源SPS的HFDs相关表达。 SA 2：体外研究SLS和SPS在介导肠道炎症中的活性及其相互关系 检测和体内无菌小鼠模型。体内外SLS在HFDs诱导的肠道损伤中的作用 炎症，重点是SLS和SPS之间的潜在关系。这个目标一定会实现的 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).