ELECTRICAL CONTROL OF INSULIN SECRETION

描述（由申请方提供）：KATP通道活性降低（KATP功能丧失，LOF）的动物可过度兴奋，最初会过度分泌胰岛素，但随后会自发或响应饮食应激而进展为分泌不足和葡萄糖耐受不良。相比之下，具有过度活跃的KATP通道（KATP功能获得性，GOF）的动物是低兴奋的，并且最初分泌胰岛素不足，然后继发性地进展到胰腺胰岛素含量的严重损失，导致糖尿病，其严重到足以导致新生儿死亡。根据我们最初的研究，我们预测KATP GOF突变可能是人类新生儿糖尿病（NDM）的基础，这在过去五年中得到了戏剧性的证实：不仅KATP GOF突变被证明是人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换为口服磺酰脲类药物，其作用是阻断KATP通道，从而直接处理分子缺陷。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，从而提供了一个易于处理的NDM（xNDM）实验模型。在解释和告知对细胞兴奋不足的反应时，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影响。为了追求的影响，我们将利用我们的诱导型转基因KATP GOF动物，以确定在细胞和胰岛水平的成像和电生理技术相结合的反应？细胞低兴奋性。我们将确定实验性NDM在不同阶段的可治疗性，告知人类NDM中无法解决的问题。我们将确定环境和遗传调节剂在整个动物水平上对不兴奋性的细胞反应中的潜在参与，以及电活动在调节来自过度兴奋（Kir6.2-/-，SUR 1-/-）和欠兴奋（他莫昔芬诱导的Pdx-DTG）动物的孤立胰岛对葡萄糖毒性的敏感性中的作用。拟议的实验将测试电兴奋性在细胞刺激分泌偶联中的作用的机制假设，以及不同形式糖尿病的病因学，并将提供影响新生儿和2型糖尿病治疗方法的机制信息。 公共卫生相关性：糖尿病是一个主要的世界性健康问题，其特征在于由胰岛素分泌抑制、对循环胰岛素无反应或两者的组合引起的高血糖状态。我们已经产生了独特的糖尿病小鼠模型，由于分泌抑制，对这些动物的分析使我们正确地预测这是人类新生儿糖尿病的主要原因，也是2型糖尿病的风险因素。该项目利用这些动物以人类不可能的方式了解疾病过程，从而帮助我们开发适当的治疗方法来治疗疾病。

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.