Characterisation of the role of NPAT in metformin regulation of body weight and glycaemic control; moving GWAS data to biological function

糖尿病是没有治愈方法的。世界各地数百万人服用的治疗糖尿病的主要药物是二甲双胍，它可以改善胰岛素的作用，降低血糖水平。然而，二甲双胍并不能降低所有患者的血糖，可能需要3-6个月的治疗才能确定该药物是否有效，其有效性随着时间的推移而降低。我们之前的工作确定了糖尿病患者的基因变异，这些变异与二甲双胍改善血糖控制的能力有关。这意味着这些基因序列直接影响糖尿病人群中药物作用的一个方面。最显著的遗传多态集中在基因组的一个区域，该区域编码7个基因，包括细胞生长调节基因ATM和NPAT。在医学研究中心的资助下，进一步的工作证实了ATM和NPAT是导致人类患者二甲双胍作用变化的基因。进行这些非常昂贵的基因研究的最终目的是找出可以帮助预测哪个患者对哪种药物有反应的“标记”，而不必等待数月的治疗。现实情况是，这些标记物中很少有足够强大或足够常见的，可以以这种方式使用。然而，第二个很大的希望是，了解我们识别的“热门”(如ATM和NPAT)如何影响药物作用，可能会阐明药物是如何起作用的，以及为什么它在某些人身上不起作用。这将有助于提高我们治疗或预防这种疾病的能力。我们的数据表明，改变NPAT的量会改变身体对二甲双胍的反应。我们现在建议获得关于NPAT如何影响二甲双胍作用的详细的生物学和分子方面的见解。我们将进行研究，以阐明二甲双胍作用和NPAT基因之间的生理、细胞和分子联系：首先，我们将研究缺乏NPAT的小鼠和只在肝脏缺乏NPAT的小鼠的葡萄糖代谢和激素作用(这是因为二甲双胍被认为主要作用于肝脏)。我们将使用最先进的技术来比较肝脏、肌肉、脂肪组织、胰腺和大脑如何共同控制体重和血糖，以及在这些NPAT缺陷的模型中对激素和二甲双胍的反应。这将告诉我们NPAT是否对葡萄糖生理的基本调节是必要的(如果肝脏NPAT是特别必要的)，以及在临床对二甲双胍的反应中。第二，我们将对缺乏NPAT的分离肝细胞进行研究，以了解NPAT如何对细胞内的生物学做出贡献。类似地，我们将使用分子方法来增加或减少代表不同组织的永生细胞系中的NPAT。这使我们能够比较NPAT蛋白产量增加或减少对肝脏、胰腺和大脑特定功能的影响。我们还将制造在人类患者中发现的NPAT中产生遗传变异的细胞，并研究这如何影响NPAT生物学和二甲双胍的作用。我们的首要目标是确定为什么NPAT基因序列影响糖尿病患者的治疗反应。这些信息将帮助临床医生决定糖尿病患者的最佳早期治疗方案，并帮助科学家为这种常见疾病开发更有效的治疗方法。

There is no cure for diabetes. The main drug prescribed for diabetes (taken by millions world-wide) is metformin, which improves insulin action to reduce blood glucose levels. However metformin does not reduce blood glucose in all patients, it can take 3-6 months of treatment to establish whether the drug is effective and its efficacy reduces with time. Our previous work identified genetic variations in people with diabetes, which were linked to the ability of metformin to improve glucose control. This implies that these gene sequences directly influence an aspect of the drug action in the diabetes population. The most significant genetic polymorphism focused to a region of the genome, which encodes 7 genes including the cell growth regulating genes ATM and NPAT. Further work, funded by the MRC, confirmed ATM and NPAT as the genes responsible for the variation in metformin action in human patients. The ultimate purpose of doing these very expensive genetic studies is to identify 'markers' that could help predict which patient will respond to which drug, without having to wait for months of treatment. The reality is that very few of these markers are strong or common enough to be used in this way. However the second big hope is that understanding how the 'hits' we identify (like ATM and NPAT) influence drug action may illuminate how the drug works and why it doesn't work in some people. This will help improve our ability to treat or prevent the disease. Our data argues that changing NPAT amount modifies the body response to metformin. We now propose to gain detailed biological and molecular insight into how NPAT influences metformin action. We will perform investigations to elucidate the physiological, cellular and molecular connections between metformin action and the NPAT gene: Firstly we will characterize glucose metabolism and hormone action in a mouse lacking NPAT and in a mouse lacking NPAT only in the liver (this is because metformin is thought to work mostly on the liver). We will use state of the art techniques to compare how the liver, muscle, fat tissue, pancreas and brain work together to control body weight and blood glucose and the response to hormones and metformin in these models with defective NPAT. This will tell us if NPAT is necessary (and if liver NPAT specifically is necessary) for basic regulation of glucose physiology, and in the clinical response to metformin.Secondly we will perform studies on isolated liver cells lacking NPAT to learn how NPAT contributes to biology inside the cells. Similarly we will use molecular approaches to increase or decrease NPAT in immortal cell lines representative of different tissues. This allows us to compare effects of increased or decreased production of NPAT proteins on specific functions of liver, pancreas and brain. We will also make cells that produce the genetic variants in NPAT found in the human patients and study how this effects NPAT biology and metformin action. Our overarching aim is to establish why NPAT gene sequences influence the response to therapy in people with diabetes. This information will help clinicians decide on the best early treatment options for people with diabetes and help scientists develop more effective therapies for this common disease.