MAP KINASE IN ISLET FUNCTION

描述(申请人提供)：由于生活质量下降和治疗费用上升，糖尿病是一个巨大的健康负担。仅在美国，约8%的人口患有糖尿病，据估计，近三分之一的成年人现在有患糖尿病的风险。肥胖、胰岛素抵抗和肝脏、脂肪和肌肉的代谢异常是疾病的重要因素。然而，最近发现的大多数与2型糖尿病相关的基因位点编码的蛋白质使胰腺细胞产生胰岛素。营养素和激素不仅调节胰岛素的分泌，还调节细胞持续产生胰岛素的能力。在这项建议中，我们将重点放在营养物质和促进细胞内胰岛素产生的试剂的作用机制上。首要目标是阐明可被操纵以改善细胞功能和克服在长期高血糖期间发生的细胞生理变化的机制，这些变化是导致胰岛素释放不足的原因。在目标1中，我们将确定味觉受体复合体(T1R1/T1R3)在胰腺细胞中的功能。这种二聚体G蛋白偶联受体(GPR)参与氨基酸传感。这种受体在味觉神经元中被发现，可以与多种氨基酸结合，但尚未在细胞上进行研究。我们发现稳定的T1R3基因敲除减少了胰岛素的分泌和胰岛素的含量，并导致了与自噬相关的事件。我们将探索这些表型变化的基础，并研究潜在的信号机制。在第二个目标中，我们将研究增强β细胞功能的小分子的分子作用机制。这些分子刺激细胞产生胰岛素，改善db/db小鼠的口服葡萄糖耐量，并在长期培养中恢复人类胰岛的胰岛素产生。我们已经确定了在用这些药物处理的细胞中发生的一些变化，包括表观遗传学变化和关键转录因子浓度的变化。我们将评估可能通过药物亲和层析确定的可能调节这些药物作用的候选药物。最后，我们将继续研究ERK1/2依赖的信号事件，通过重点研究辅助激活因子p300的招募机制来控制胰岛素基因的转录。这些研究将为氨基酸如何调节胰岛素的产生、稳定性和释放提供新的理解，并将开发一种新的药理学工具来确定在正常和衰竭胰岛中增强胰岛素产生和胰岛素转录的机制。 公共卫生相关性：在美国，2型糖尿病现在不仅存在于成人中，也存在于儿童中。这些研究将探索提高糖尿病患者胰岛素产生的新机制，重点放在营养感应受体和一种新的小分子上，这种小分子可以增强功能不良的胰岛的胰岛素产生。

DESCRIPTION (provided by applicant): Diabetes mellitus is a huge health burden due to decreased quality of life and the escalating cost of treatment. In the United States alone, ~8% of the population is diabetic and nearly one-third of adults are now estimated to be at risk to develop the disease. Obesity, insulin resistance and metabolic abnormalities in liver, adipose, and muscle are important factors in disease. Yet, most of the gene loci recently found associated with type 2 diabetes encode proteins that enable insulin production from pancreatic cells. Nutrients and hormones regulate not only insulin secretion but also the capacity of cells to continue to produce insulin. In this proposal we focus on mechanisms of action of nutrients and agents that enhance insulin production in cells. The overarching goals are to elucidate mechanisms that can be manipulated to improve -cell function and overcome the physiological changes in cells that occur during prolonged hyperglycemia, contributing to inadequate insulin release. In aim 1 we will determine the functions of the taste receptor complex (T1R1/T1R3) in pancreatic cells. This dimeric G protein-coupled receptor (GPR) is involved in amino acid-sensing. This receptor, identified in gustatory neurons, binds to a variety of amino acids, but has not been studied on cells. We find that stable knockdown of T1R3 reduces insulin secretion, and insulin content, and causes events associated with autophagy. We will explore the bases for these phenotypic changes and we will also examine the underlying signaling mechanisms. In the second aim we will examine molecular mechanisms of action of small molecules that enhance beta-cell function. These molecules stimulate insulin production by cells, improve oral glucose tolerance of db/db mice, and restore insulin production by human islets in long term culture. We have identified a number of changes that take place in cells treated with these drugs, including epigenetic alterations, and changes in concentrations of key transcription factors. We will evaluate candidates that may mediate the actions of these drugs identified by drug-affinity chromatography. Finally, we will continue to investigate ERK1/2-dependent signaling events that control insulin gene transcription by focusing on mechanisms of recruitment of the coactivator p300. These studies should provide new understanding of how amino acids regulate insulin production, stability and release and will exploit a new pharmacological tool to identify mechanisms to enhance insulin production and insulin transcription in normal and failing islets. PUBLIC HEALTH RELEVANCE: Type 2 diabetes mellitus is now found not only in adults but also in children in the United States. These studies will explore new mechanisms to enhance insulin production in diabetes focusing on a nutrient sensing receptor and a novel small molecule that enhances insulin production from poorly functioning islets.