ELECTRICAL CONTROL OF INSULIN SECRETION

描述（由申请人提供）：KATP通道活性降低（KATP功能丧失，LOF）的动物过度兴奋，最初分泌胰岛素过多，但继发性进展，自发或对饮食应激的反应，分泌不足和葡萄糖耐受不良。相比之下，KATP通道过度活跃的动物（KATP功能获得，GOF）是不可兴奋的，最初分泌胰岛素不足，然后继发性进展为胰腺胰岛素含量的严重丧失，导致糖尿病，严重到足以导致新生儿死亡。基于我们最初的研究，我们预测KATP GOF突变可能是人类新生儿糖尿病（NDM）的基础，这在过去的五年中得到了极大的证实：不仅KATP GOF突变被证明是人类NDM的主要原因，而且许多患者已经成功地从注射胰岛素治疗转向口服磺脲类药物，这种药物可以阻断KATP通道，从而直接治疗分子缺陷。我们的第二代KATP GOF转基因小鼠提供了转基因表达的时间和组织特异性控制，从而提供了一个可处理的NDM （xNDM）实验模型。在解释和告知对细胞低兴奋性的反应时，我们对这些小鼠的初步发现对人类NDM和2型糖尿病的基本机制具有潜在的广泛意义。为了进一步研究，我们将利用可诱导的转基因KATP GOF动物，结合成像和电生理技术，在细胞和胰岛水平上确定对细胞低兴奋性的反应。我们将确定实验性NDM在不同阶段的可治疗性，告知人类NDM中其他无法解决的问题。我们将在整个动物水平上确定环境和遗传调节剂在细胞对不可兴奋性的反应中的潜在参与，以及在高兴奋性（Kir6.2-/-, SUR1-/-）和低兴奋性（他莫昔芬诱导的Pdx-DTG）动物的分离胰岛中，电活动在调节胰岛对糖毒性敏感性中的作用。拟议的实验将测试电兴奋性在细胞刺激-分泌耦合和不同形式糖尿病病因中的作用的机制假设，并将提供影响新生儿和2型糖尿病治疗方法的机制信息。

DESCRIPTION (provided by applicant): Animals with reduced KATP channel activity (KATP loss-of-function, LOF) are hyperexcitable and initially hypersecrete insulin, but secondarily progress, either spontaneously or in response to dietary stress, to undersecretion and glucose- intolerance. In contrast, animals with overactive KATP channels (KATP gain-of-function, GOF) are underexcitable and initially undersecrete insulin, and then secondarily progress to profound loss of pancreatic insulin content, resulting in diabetes that can be severe enough to cause neonatal lethality. Based on our initial studies we predicted that KATP GOF mutations could underlie human neonatal diabetes (NDM) and this has been dramatically confirmed over the last five years: not only have KATP GOF mutations been shown to be the major cause of human NDM, but many patients have since successfully switched from injected insulin treatments to oral sulfonylureas, which act to block the KATP channel, thereby treating the molecular defect directly. Our second generation KATP GOF transgenic mice provide temporal and tissue-specific control of transgene expression and thereby provide a tractable experimental model of NDM (xNDM). In explaining and informing the response to ¿-cell underexcitability, our preliminary findings with these mice have potentially broad implications for fundamental mechanisms in both human NDM and type 2 diabetes. To pursue the implications, we will utilise our inducible transgenic KATP GOF animals to determine the response to ¿-cell underexcitability at the cellular and islet level using a combination of imaging and electrophysiological techniques. We will determine the treatability of experimental NDM at different stages, informing otherwise unaddressable issues in human NDM. We will determine the potential involvement of environmental and genetic modulators in the ¿-cell response to inexcitability at the whole animal level, and the role of electrical activity in modulating islet sensitivity to glucotoxicity in isolated islets from hyperexcitable (Kir6.2-/-, SUR1-/-) and underexcitable (tamoxifen-induced Pdx-DTG) animals. The proposed experiments will test mechanistic hypotheses of the role of electrical excitability in stimulus-secretion coupling in ¿-cells and in the etiology of different forms of diabetes and will provide mechanistic information that will impact treatment approaches to both neonatal and type 2 diabetes. PUBLIC HEALTH RELEVANCE: Diabetes is a major world health problem, characterized by a hyperglycemic state caused by depressed secretion of insulin, unresponsivity to circulating insulin, or a combination of both. We have generated unique mouse models of diabetes due to depressed secretion and the analysis of these animals led us to correctly predict that this is a major cause of neonatal diabetes in humans, as well as a risk factor for type 2 diabetes. The project makes use of these animals to understand the disease process in a way that is impossible in humans, and thereby helps us to develop appropriate therapies to treat the disease.