(一)利用LC-MS/MS探索線蟲捕捉真菌具殺線蟲活性代謝物 (二)腸道微生物衍生代謝物對肝細胞脂肪積累的抑制作用

Abstract

代謝組學是涉及代謝物、小分子中間體和新陳代謝產物於化學過程的研究。而代謝組學所提供的訊息與表型較有直接相關。其分類和量化生物體中發現的無數小分子，以研究複雜生物系統中的代謝特徵變化。為了理解未知代謝物與生物體之間的相互作用，我們使用液相層析結合串聯質譜(LC-MS / MS)方法為基礎以利用MS/MS圖譜結果與數據庫進行比較，通過非靶向代謝組學分析鑑定調節變化的代謝物。 在我的研究論文中的其中一個主題是與中研院分子生物所薛雁冰博士合作的項目：探索線蟲捕獲真菌(NTF)的代謝產物。我們發現捕獲線蟲的真菌可以感知線蟲的存在並發展出一套專門的菌絲體捕獲裝置，其可通過形成粘附性網絡來捕獲並消耗線蟲。然而，該粘附性網絡的化學成分以及對線蟲的致病機制仍然未知，因此我們探討所分離的100株野生型線蟲捕獲真菌其由線蟲所誘導的粘附網絡，其中包括64株Arthrobotrys oligospora，18株 Arthrobotrys thaumasia和18株Arthrobotrys musiformis。將NTF與秀麗隱桿線蟲(C. elegans)共培養後所形成的粘附網絡以探測捕食者-獵物關係中代謝特徵的變化，從而表徵由NTF產生負責殺死線蟲的次級代謝物。我們發現了一些顯著改變的代謝物，未來可能是寄生線蟲感染的治療方法。 另一個主題是與本實驗室呂強博士合作的項目：研究腸道微生物群衍生的代謝物對宿主脂肪積累的抑製作用。眾所周知，人體腸道具有多種共生的微生物菌群，可以產生無數的特殊代謝物。這些代謝物可能參與宿主的生理代謝過程。此外，飲食可以調節與人類健康有關的腸道微生物群，故飲食習慣可能導致肥胖，並可能對疾病產生間接或直接影響。為了解腸道微生物衍生的特殊代謝物與人類健康的相關性，我們採用了C57BL/6小鼠建立的酚類-抗肥胖模型，並利用gnotobiotic小鼠評估特殊的腸道微生物群對糞便中代謝物組成的影響。在體外同時培養腸道微生物，透過其代謝物來確定糞便代謝物的組成是由微生物本身所衍生的。進一步利用HepG2肝細胞建立肝臟脂肪積累模型，以驗證腸道微生物群衍生的代謝物具有脂質積累抑制活性。並且發現一系列腸道微生物群衍生的代謝物能夠介導肝細胞對脂質積累的抗性。 在我的研究論文中，我們在不同的生物系統上應用了非靶向代謝組學來探究生物活性代謝物：線蟲誘捕真菌的殺線蟲毒素和腸道微生物群衍生的代謝物對肝細胞的脂質積累具有抑制作用。

Metabolomics is the study of chemical processes involving metabolites, the small molecule intermediates, and products of metabolism. And the information metabolomics provides is related to phenotype. That catalog and quantify the countless small molecules found in the organism to study how the metabolic features change of a complex biological system. In order to understand the interaction between unknown metabolites and organism, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) based method to utilize MS/MS results comparison with databases to identify regulated metabolites by untargeted metabolomics analysis. One of the projects in my research thesis was exploring the metabolites from nematode-trapping fungi, that was a collaboration with Dr. Yen-Ping Hsueh at Institute of Molecular Biology, Academia Sinica. We found that the nematode-trapping fungi can sense the presence of nematodes and develop specialized mycelial trap devices to catch and consume nematodes by forming an adhesion network. However, chemical compositions of the adhesion networks as well as the pathogenic mechanism to nematodes remain unknown, so that we explore the metabolomics features of nematode-induced adhesion networks in 100 isolated NTF strains of the genus Arthrobotrys, including 64 Arthrobotrys oligospora strains, 18 Arthrobotrys thaumasia strains, and 18 Arthrobotrys musiformis strains. NTF cultures were co-cultured with Caenorhabditis elegans overnight to form adhesive networks to probe changes of metabolomic features in a predator-prey (NTF-nematode) relationship so as to characterize NTF secondary metabolites responsible for killing nematodes. And we’ve found some metabolites which were significantly changed and could be the treatment of parasitic nematode infections. Another one of the projects was investigating the inhibition effect of gut microbiota-derived metabolites on fat accumulation in the host, that was a collaboration with Dr. Qiang Lyu. Well known that the human intestinal tract has a diverse of mutualistic microbial flora which could produce countless of specialized metabolites. These metabolites may be involved in the physiological metabolic processes in the host. In addition, the diet can modulate the gut microbiome that is related to human health, that dietary habits may cause obesity and may have an indirect or direct impact with the disease. In order to understand which and how the gut microbe-derived specialized metabolites affect human health, that we used phenolic anti-obesity model established by C57BL/6 mice, and gnotobiotic mice were used to evaluate the effect of special gut microbiota on metabolite composition of feces. The simultaneous culture of intestinal microbes in vitro, we can determine the composition of fecal metabolites by derived metabolites from gut microbiota themselves. The HepG2 hepatocytes were used to establish a model of liver fat accumulation, to verify the gut microbiota-derived metabolites have the lipid accumulation inhibitory activity. And that a series of gut microbiota-derived metabolites were found to be able to mediate hepatocytes resistance to lipid accumulation. In my research thesis, we applied untargeted metabolomics on different biological systems to discover bioactivity metabolites: a nematicidal toxin from nematode-trapping fungi and the gut microbiota-derived metabolites which inhibit lipid accumulation on hepatocytes.