Lachnospiraceae in the gut microbiome and their role in disease

尽管肠道微生物群与许多疾病有关，但关于它如何影响哺乳动物生理的基本问题仍然存在。许多研究表明肠道细菌与特定疾病之间存在相关性，但很少有迹象表明它们可能影响疾病发生或进展的机制。应用BBSRC的综合微生物组研究方法，我们通过开展结合生物科学内外一系列学科的技能、方法和专业知识的研究，获得了出色的初步数据。这使我们开始了解肠道微生物群直接影响哺乳动物健康的独特机制。我们最近的工作显示了哺乳动物肠道内的一种独特的细菌家族，毛螺旋科，如何产生两种分子（3M-4-TMAB和4-TMAP），直到我们最近发现。这些分子存在于小鼠的每个器官中，甚至会进入白质。然而，它们的意义在于它们的结构模仿肉碱，肉碱是一种对哺乳动物能量产生至关重要的分子。肉毒碱作为一种载体分子，将脂肪酸运送到线粒体中，在那里它们被燃烧为能量。然而，我们发现的细菌分子抑制了这一过程，减少了细胞存在时产生的能量。这是非常重要的，因为线粒体的能量产生过程在包括2型糖尿病和退行性/非综合征性自闭症在内的许多人类疾病中都受到影响。虽然我们提出了肠道微生物组对哺乳动物疾病的前所未有的投入，但我们最近的突破性工作（发表在《科学进展》杂志上）和我们在这里提出的初步数据，为这些分子的系统存在和抑制潜力提供了坚实的证据。此外，众所周知，在2型糖尿病患者和退行性自闭症患者中，产生这些分子的毛螺杆菌科细菌的水平都显著增加。我们甚至确定，其他人在先前的2型糖尿病和自闭症研究中已经确定了3M-4-TMAB和4-TMAP的存在，尽管当时他们不知道这些分子是什么或它们的意义。鉴于我们的发现，我们相信了解这些分子在哺乳动物生理学中的作用是必要的。我们打算在本提案中；首先，阐明这些分子干扰线粒体能量产生的途径。这将需要详细研究它们与与这一过程相关的酶的相互作用，以及这些分子可能对哺乳动物生理产生的更广泛影响。我们还将检查，当它们在肠道中产生时，它们是否会导致肉毒碱水平的降低，因为它可能是制造3M-4-TMAB和4-TMAP的前体分子。这种肉碱水平的降低（如在T2D和ASD中所见）将进一步导致哺乳动物细胞能量产生的下降。我们还将测试针对细菌的抑制剂，看看我们是否可以阻止3M-4-TMAB和4-TMAP的产生，这种方法可能会导致未来对这些疾病的治疗干预。-其次，我们将确定这些分子对哺乳动物细胞和动物模型的健康和疾病的影响。我们将使用特定的细胞来观察这些分子的存在是否会引起特定的疾病迹象。对于2型糖尿病来说，这可能是细胞不再对胰岛素产生反应的迹象，导致血液中的葡萄糖积聚。在肥胖中，我们会看到脂肪在细胞中堆积，因为能量产生被阻断，而在退行性ASD中，大脑中需要脂肪酸分解来产生能量的干细胞现在开始迅速增殖。然后，我们的工作将使用一些缺乏肠道微生物组的动物，来测试这些分子改变哺乳动物对每种疾病的生理机能的能力。

Despite the gut microbiome being linked to numerous diseases, fundamental questions remain regarding how it influences mammalian physiology. Many studies show correlation between gut bacteria and specific diseases, but with little indication of the mechanism by which they may affect disease initiation or progression. Applying the BBSRC approach of Integrative Microbiome Research we have generated exceptional preliminary data by carrying out research that combines the skills, methodologies and expertise from a range of disciplines from within the biosciences and beyond. This has enabled us to begin to understand a unique mechanism by which the gut microbiome can directly influence mammalian health. Our recent work shows how a unique family of bacteria within the mammalian gut, the Lachnospiraceae, produce two molecules (3M-4-TMAB and 4-TMAP) that were unknown until our recent discovery. These molecules were found in every organ in a mouse, even crossing into white matter. Their significance however lies in their structural mimicry of carnitine, a molecule critical to mammalian energy production. Carnitine acts as a carrier molecule, transporting fatty acids into mitochondria where they are burned for energy. However the bacterial molecules we discovered inhibit this process, reducing the amount of energy cells can produce when they are present. This is incredibly significant as the process of energy production in the mitochondria is known to be affected in a number of human diseases including type 2 diabetes and regressive/non-syndromic autism. While we propose an unprecedented input for the gut microbiome into mammalian disease, our recent breakthrough work (in press at Science Advances) and the preliminary data we present here, provide solid evidence for both the systemic presence and inhibitory potential of these molecules. Also the presence of the Lachnospiraceae bacteria that produce these molecules at significantly increased levels in both type 2 diabetes patients and those with regressive autism is well known. We even determined that others have identified the presence of 3M-4-TMAB and 4-TMAP in prior studies of type 2 diabetes and autism, although at the time they were unaware of what these molecules were or their significance. Given our findings we believe that understanding the role of these molecules in mammalian physiology is imperative. We intend in this proposal to;- Firstly, elucidate the means by which these molecules interfere with energy production in the mitochondriaThis will entail detailed studies of their interactions with enzymes linked to this process as well as wider effects these molecules may have on mammalian physiology. We will also check to see if, when they are produced in the intestine, they lead to a reduction in carnitine levels as it may act as a precursor molecule for making 3M-4-TMAB and 4-TMAP. Such a reduction in carnitine levels (as seen in T2D and ASD) would further contribute to a drop in energy production by mammalian cells. We will also test inhibitors against the bacteria to see if we can stop production of 3M-4-TMAB and 4-TMAP, an approach that could lead to future therapeutic interventions in these diseases. - Secondly,we will determine the effects of these molecules on health and disease in mammalian cells and animal modelsWe will use specific cells to see if presence of these molecules induces specific signs of disease. For type 2 diabetes this would be any indication cells are no longer responding to insulin, leading to glucose build up in the blood. In obesity, we would see fat build up in cells as energy generation is blocked, while in regressive ASD stem cells in the brain that require fatty acid breakdown to generate energy would now begin to proliferate rapidly. Our work will then use animals, some lacking a gut microbiome, to test the ability of these molecules to alter mammalian physiology with respect to each disease.