Genetic and nutritional control of pancreatic beta cell identity.

糖尿病影响着超过2000万欧洲人和全世界4亿人。该病的并发症，包括失明、肾衰竭、心血管疾病和癌症，大大降低了生活质量，并消耗了大多数西方国家近10%的医疗费用。预计这些数字在未来几年将进一步增加。最常见的形式是2型糖尿病（T2D），有遗传和环境原因，在营养过度和肥胖的人群中尤为普遍。过去，t2dm的治疗方法依赖于提高负责降低血糖水平的胰岛素的作用，以及刺激胰岛素分泌。然而，没有一种现有的治疗方法可以逆转正常β细胞身份和功能的逐渐丧失，从而使疾病症状逐渐恶化。T2D的“全基因组关联研究”（GWAS）现在已经确定了许多遗传变异，其遗传与糖尿病风险增加有关。这些基因中的大多数影响胰岛素的产生，它们的识别不仅提高了预测的能力，而且令人兴奋的是，它们还为药物治疗提供了潜在的新分子靶点。现在已经确定了超过100个基因位点，总共包含了近500个基因。我们的工作首先寻求确定选定基因座中的哪些基因负责增加疾病风险。这既包括对人类的遗传研究，也包括基于研究从疾病相关组织（通常是胰腺细胞）中删除特定基因的影响的功能分析。我们已经证明，一种名为STARD10的基因表达的变化是导致11号染色体上一组特定遗传变异的携带者患糖尿病风险增加的原因。STARD10基因能够结合细胞内的脂肪分子（脂质），并在细胞内的离散位置之间携带它们。然而，目前我们对这种基因是如何影响细胞的代谢从而损害胰岛素的释放知之甚少。了解这个问题是很重要的，因为它可能提供新的方法来改善那些由于携带该基因的风险变体而患糖尿病风险增加的个体（超过人口的80%）的激素分泌。因此，我们将使用人类胰岛、人类衍生的β细胞和β样细胞（后者在试管中从胚胎干细胞中产生）进行细胞分析，以确定删除STARD10的影响，并了解与疾病风险相关的变异如何改变该基因的表达。我们研究的第二个目的是了解两个基因产物LKB1和AMPK是如何调节胰腺β细胞功能的。我们知道，删除小鼠β细胞中的任何一个基因都会导致细胞特性的改变，导致其他基因的上调，这些基因通常在胰岛中不表达，但在神经和肝细胞中含量很高。AMPK本身受LKB1调节，由于这种酶受包括葡萄糖在内的营养物质的控制，因此我们对此特别感兴趣。我们将确定这两种酶的活性变化是否通过促使核DNA结构的变化（打开或关闭）来影响基因表达。我们还将确定小分子AMPK激活剂对β细胞功能的影响，它在糖尿病中具有治疗前景。我们的最终目的是确定在缺乏LKB1的情况下，STARD10在控制β细胞功能中的作用是否会改变，我们最近在另一个GWAS基因TCF7L2中描述了这种现象，或者通过营养状况的改变。我们将使用新颖而强大的技术，包括基因组编辑、人类胚胎干细胞定向分化、小鼠遗传学、光药理学和植入小鼠眼睛后的胰岛成像，来回答我们的问题。

Diabetes mellitus affects more than 20 m Europeans and 400 m individuals worldwide. The complications of the disease, including blindness, kidney failure, cardiovascular disease and cancer, drastically reduce quality of life, and consume almost 10 % of health care costs in most westernised nations. These figures are expected to increase further in coming years. The most common form, Type 2 diabetes (T2D), has both genetic and environmental causes, and is particularly prevalent in those affected by over-nutrition and obesity. Therapeutic approaches towards T2D have relied in the past on enhancing the actions of insulin, responsible for lowering blood glucose levels, and on stimulating insulin secretion. However, none of the existing therapies reverse the progressive loss of normal beta cell identity and function and hence the gradual worsening of disease symptoms. "Genome wide association studies" (GWAS) for T2D have now identified numerous genetic variants whose inheritance is associated with an increased risk of diabetes. The identification of these genes, most of which influence insulin production, provides both improved powers of prediction and, just as excitingly, potential new molecular targets for drug treatment. More than 100 hundred genetic loci have now been identified which collectively harbour almost 500 genes. Our work seeks firstly to determine which of the genes in selected loci are responsible for increased disease risk. This involves both genetic studies in man, and functional analyses based on studying the impact of deleting a particular gene from the disease relevant tissue - usually the pancreatic beta cell. We have shown that a changes in the expression of a gene termed STARD10, which is able to bind fat molecules (lipids) within the cell and carry them between discrete intracellular locations, is responsible for the increased diabetes risk observed in carriers with a specific set of genetic variants on chromosome 11. At present, however, we have very little idea how this gene affects the cell's metabolism to impair the release of insulin. Understanding this question is important since it may provide new ways in which to improve the production of the hormone in those individuals (more than 80 % of the population) who are at increased risk of diabetes thanks to carrying the risk variant of this gene.We will therefore perform cellular analyses using human islets, human-derived beta and beta-like cells, the latter produced in the test tube from embryonic stem cells, to determine the impact of deleting STARD10, and to understand how the variants associated with disease risk alter the expression of this gene.The second Aim of our studies is to understand how two gene products, LKB1 and AMPK, are able to regulate pancreatic beta cell function. We know that deleting either gene in the mouse beta cell leads to a change in cellular identity, leading to the up-regulation of other genes which are not normally expressed in the islet but present at high levels in nerve and liver cells. AMPK, which is itself regulated by LKB1, is of particular interest since this enzyme is controlled by nutrients including glucose. We will determine whether changes in the activity of either enzyme affect gene expression by prompting changes in the structure (opening or closing) of nuclear DNA. We will also determine the impact of small molecule AMPK activators, which hold therapeutic promise in diabetes, on beta cell function.Our final Aim is to determine whether the role of STARD10 in controlling beta cell function may be altered in the absence of LKB1, a phenomenon we have recently described for another GWAS gene, TCF7L2, or by changes in nutritional status. We will use novel and powerful technologies including genome editing, directed differentiation of human embryonic stem cells, mouse genetics, photopharmacology and imaging of the islet after engraftment within the mouse eye, to answer our questions.