Using a 'Designer Receptor Exclusively Activated by Designer Drug' to define the role of short chain fatty acids in metabolic disease and inflammation

食物通常被认为仅仅是身体的一种燃料。然而，最近有一点变得很清楚，我们饮食中的成分要么直接起到调节细胞和组织功能的作用，要么被转化为实现这一功能的分子。健康饮食的概念以及肠道中大量细菌如何协调和定义健康饮食的概念并不新鲜，但近年来，关于饮食、健康和人类疾病之间的关系的知识和公众兴趣大幅增长。例如，人们普遍认为“纤维”是健康饮食的重要组成部分。肠道中的微生物将“纤维”转化为短链脂肪酸(SCFA)，其中高水平的短链脂肪酸存在于肠道中，并被输送到体内。在这两个位置，这类单链脂肪酸被认为通过与称为游离脂肪酸受体(FFAR)2和FFAR3的跨膜受体结合并激活来发挥其许多重要作用。FFAR2和FFAR3都是G蛋白偶联受体(GPCR)家族的成员，开发能够激活或阻断其他GPCRs的药物已被证明是治疗多种人类疾病的非常有效的方法。由于这些受体存在于许多组织上，包括控制炎症和免疫的各种白细胞、储存脂肪的脂肪细胞，以及释放激素的下部肠道细胞，这些激素反过来调节胰腺胰岛素的释放，并对食欲产生影响，因此它们被认为是可能的受体，用于治疗从炎症性肠病到糖尿病的各种疾病。然而，在做出以任何受体为靶点的长期决定可能是一种有效的方法之前，制药公司会寻求“验证”，以尽可能多地产生对该想法的信心。与FFAR2或FFAR3的验证有关的问题有许多。首先，这两种受体被相同的单链脂肪酸激活。这意味着，在两者都存在的细胞和组织中，很难确定哪一个是最重要的。之前克服这一问题的努力包括制造缺乏FFAR2或FFAR3的小鼠。虽然有用，但缺少其中一个会导致另一个的数量发生变化。其次，许多关键影响可能要求两者都存在。为了克服这一点，我们制造了一种FFAR2版本，它不是由SCFA激活，而是由一种名为山梨酸的分子激活。建议的一个关键计划是培育出FFAR2的正常拷贝被这种工程变体取代的小鼠。在这些动物中，FFAR2和FFAR3都会存在，但现在它们可以被不同的分子激活，这将使我们能够梳理出它们各自对功能的贡献。这将为FFAR2或FFAR3在不同治疗适应症中的应用提供验证。当然，这是达到目的的一种手段，长期计划是开发针对FFAR2和FFAR3的选择性药物。申请者已经开始开发分析方法和方法来做到这一点，并产生了一些药理‘工具’化合物，以帮助进一步确定FFAR2和FFAR3的功能。然而，制药公司能够更好地将所需的技能转化为具有类似药物特性的分子，从而可以用来测试在简单细胞系统中开发的想法，以及在老鼠身上开发的想法在人类身上。因此，申请者已经同意在这个项目上与制药公司阿斯利康的科学家合作。在这些研究中，我们将为FFAR2和FFAR3提供一系列新颖的“工具”化合物，以提供进一步的见解，其结果将帮助公司做出关键决策，即FFAR2和/或FFAR3是否成为开发有效药物的现实目标。

Food is often considered simply as a source of fuel for the body. However, in recent times it has become clear that components of what we eat either also act directly to regulate cellular and tissue functions or are converted into molecules that do so. The concept of a 'healthy diet' and how this might be orchestrated and defined by the vast number of bacteria that populate the intestine is not new but, in recent times, knowledge about and public interest in the relationship between diet, well-being and human disease has grown substantially. For example, it is widely recognised that 'fibre' is an important component of a healthy diet. Microbes in the gut convert 'fibre' into short chain fatty acids (SCFAs) and high levels of these are present in the gut and are transported into the body. In both of those locations such SCFAs are believed to produce many of their important roles by binding to and activating transmembrane receptors called free fatty acid receptor (FFAR)2 and FFAR3. Both FFAR2 and FFAR3 are members of the G protein-coupled receptor (GPCR) family and developing drugs that either activate or block other GPCRs has proved to be a very effective approach to tackling a wide range of human diseases. As these receptors are present on a number of tissues including various white blood cells that control inflammation and immunity, adipocytes that store fat, and various cells of the lower gut that release hormones that in turn modify release of insulin from the pancreas and have effects on the desire to eat, they are being considered as possible receptors to target in diseases that range from inflammatory bowel disease to diabetes. However, prior to making long term decisions that targeting any receptor is likely to be a productive approach, pharmaceutical companies seek 'validation', to generate as much confidence in the idea as possible. There are a number of issues in relation to validation of either FFAR2 or FFAR3. Firstly these two receptors are activated by the same SCFAs. This means that in cells and tissues in which both are present it is difficult to be certain which is most important. Previous efforts to overcome this have involved making mice that lack either FFAR2 or FFAR3. Although useful, the absence of one of the two results in change in amount of the other. Secondly, a number of key effects may require both to be present. To overcome this we have made a version of FFAR2 that instead of being activated by SCFAs is instead activated by a molecule called sorbic acid. A key plan proposed is to generate mice in which the normal copy of FFAR2 is replaced with this engineered variant. In these animals both FFAR2 and FFAR3 will be present but now they can be activated by different molecules and this will allow us to tease out their individual contributions to function. This will provide validation of either FFAR2 or FFAR3 in different therapeutic indications. Of course this is a means to an end and the long term plan is to develop selective medicines that target FFAR2 and FFAR3. The applicants have begun to develop assays and approaches to do this and have generated a number of pharmacological 'tool' compounds to help further define the function of FFAR2 and FFAR3. However, pharmaceutical companies are better able to bring the skills required to convert such 'tool' compounds into molecules that have 'drug-like' properties and, therefore, might be used to test ideas developed in either simple cell systems and in mice into humans. As such, the applicants have agreed to collaborate in this project with scientists from the pharmaceutical company AstraZeneca. In these studies we will be provided with a range of novel 'tool' compounds for FFAR2 and FFAR3 to provide further insight and the outcomes will assist the company in making key decisions on whether FFAR2 and/or FFAR3 become 'validated' as realistic targets to develop effective medicines against.