Stimulus secretion coupling in pancreatic beta-cells

胰腺β细胞的刺激分泌耦合

• 批准号: 9356042
• 负责人: Arthur Sherman
• 金额: $ 18.06万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9356042
• 关键词: Accounting; Action Potentials; Adult; Alpha Cell; Area; Behavior; Beta Cell; Binding; Biophysical Process; Ca(2+)-Transporting ATPase; Calcium; Cells; Characteristics; Chemicals; Child; Citric Acid; Citric Acid Cycle; Consumption; Coupled; Coupling; Cyclic AMP; D Cells; Defect; Development; Diabetes Mellitus; Differential Equation; Disease; Employee Strikes; Endocrine; Feedback; Fluorescence Resonance Energy Transfer; Fructose; Glucagon; Glucose; Glyburide; Glycolysis; Health; Hereditary Disease; Hormones; Human; Hyperinsulinism; Hypoglycemia; Image; Individual; Insulin; Ion Channel; Islets of Langerhans; Lead; Life; Link; Membrane Potentials; Metabolic; Metabolism; Mitochondria; Modeling; Non-Insulin-Dependent Diabetes Mellitus; Organ; Pancreas; Paper; Pattern; Pharmaceutical Preparations; Phase; Physiologic pulse; Physiological; Plasma; Potassium; Potassium Channel; Production; Protein Kinase C; Publishing; Pyruvate; Pyruvate Kinase; Regulation; Reporter; Reporting; Rodent; Signal Pathway; Somatostatin; Stimulus; Structure of alpha Cell of islet; Structure of beta Cell of islet; Sulfonylurea Compounds; System; Testing; Time; Tolbutamide; Work; base; cell type; clinically significant; gain of function mutation; genome wide association study; glucose metabolism; insulin secretion; interest; islet; loss of function mutation; mathematical model; millisecond; model building; neglect; paracrine; research study; response; sensor; stem; tool

Beta Cells: One of our main activities over the last few years has been the development of a comprehensive model for oscillations of membrane potential and calcium on time scales ranging from seconds to minutes. These lead to corresponding oscillations of insulin secretion. The basic hypothesis of the model is that the faster oscillations (tens of seconds) stem from feedback of calcium onto ion channels, likely calcium-activated potassium (K(Ca)) channels and ATP-dependent potassium (K(ATP)) channels, whereas the slower oscillations (five minutes) stem from oscillations in metabolism. The metabolic oscillations are transduced into electrical oscillations via the K(ATP) channels. The model thus consists of an electrical oscillator (EO) and a metabolic oscillator (MO) and is referred to as the Dual Oscillator Model (DOM). In our model, the MO is a glycolytic oscillator, but many of the features of the system would still hold if the metabolic oscillation arose elsewhere, such as the mitochondria. K(ATP) channels are of clinical significance as they are a first-line target of insulin-stimulating drugs, such as the sulfonylureas tolbutamide and glyburide, used in the treatment of Type 2 Diabetes. Severe gain-of-function mutations of K(ATP) are a major cause of neo-natal diabetes mellitus, whereas moderate gain-of-function mutations have been linked in genome-wide association studies (GWAS) to the milder but more common disease, adult-onset type 2 diabetes. Conversely, loss-of-function mutations of K(ATP) are a major cause of familial hyperinsulinism, a hereditary disease found in children in which beta cells are persistently electrically active and secrete insulin in the face of normal or low glucose, causing life-threatening hypoglycemia. For a review of the importance of oscillations of insulin secretion for health and disease see Reference # 3 in the 2015 report. Over a period of years we have accumulated a good deal of indirect evidence supporting the model, but we felt it important to devise a direct test of the central feature, namely that glycolysis oscillates. Our experimental collaborators developed a FRET-based sensor by modifiying pyruvate kinase (PK). PK binds fructose-1,6-bisphosphate (FBP), a key glycolytic metabolite, which was predicted to oscillate by the DOM. A previous paper confirmed that the sensor (PKAR, for pyruvate kinase activity reporter) does oscillate. In the current period the characteristics of the oscillations were probed more stringently by recording them simultaneously with membrane potential in order to ascertain the phase relationship between them. The experiments (Ref. # 1) again confirmed that PKAR oscillates and that it can do so even when calcium does not oscillate, as also predicted by the model. However, the phase relationship did not agree with the model prediction: PKAR declined during the active phase of the oscillation, whereas it was predicted to be high throughout the active phase because of a pulse of glycolytic activity. Two other metabolites, NAD(P)H and ATP, were also imaged and revealed a similar pattern. The discrepancy between prediction and experiment was striking but required only one major revision to the model to resolve. A previously known but neglected effect of calcium to accelerate the citric acid was added. This increases mitochondrial consumption of pyruvate, drawing down cytosolic FBP rapidly enough to overcome the surge in FBP production in glycolysis. In order to match the observation that ATP also declined during the active phase, it was necessary to assume in addition that the consumption of ATP by calcium pumps during the active phase was great enough to overcome the increased ATP production due to the stimulation of the citric acid cycle. This potent consumption of ATP serves to hasten the termination of the active phase because it allows K(ATP) channels to reopen. Further work will be needed to test the new predictions generated by the revised model and to fully understand the benefits of this more complicated arrangement. Alpha Cells: The regulation of glucagon secretion in the pancreatic -cell is not well understood. It has been proposed that glucose suppresses glucagon secretion either directly through an intrinsic mechanism, within the -cell, or indirectly through an extrinsic mechanism. We previously described a mathematical model for isolated pancreatic alpha-cells and used it to investigate possible intrinsic mechanisms of regulating glucagon secretion. We demonstrated that glucose can suppress glucagon secretion through both ATP-dependent potassium channels (K(ATP)) and a store-operated current (SOC). We now develop an islet model that combines previously published mathematical models of alpha- and beta-cells with a new model of delta-cells and use it to explore the effects of insulin and somatostatin on glucagon secretion. We show that the model can reproduce experimental observations that the inhibitory effect of glucose remains even when paracrine modulators are no longer acting on the -cell. We demonstrate how paracrine interactions can either synchronize - and -cells to produce pulsatile oscillations in glucagon and somatostatin secretion or fail to do so. The model can also account for the paradoxical observation that glucagon can be out of phase with insulin while alpha-cell calcium is in phase with insulin. We conclude that both paracrine interactions and the alpha-cell's intrinsic mechanisms are needed to explain the response of glucagon secretion to glucose.

β细胞： 在过去几年中，我们的主要活动之一是开发了一个综合模型，用于振荡膜电位和钙的时间尺度范围从秒到几分钟。 这些导致胰岛素分泌的相应振荡。 该模型的基本假设是，更快的振荡（数十个秒）源于钙在离子通道上的反馈，可能是钙激活的钾（K（CA））通道（K（CA））通道和ATP依赖性钾（K（ATP））通道，而振动（五分钟）则来自振动（五分钟），源于振动效果。 代谢振荡通过K（ATP）通道转导为电振荡。 因此，该模型由电振荡器（EO）和代谢振荡器（MO）组成，被称为双振荡器模型（DOM）。 在我们的模型中，MO是糖酵解振荡器，但是如果代谢振荡在其他地方（例如线粒体）中出现，则系统的许多特征仍然可以保持。 K（ATP）通道具有临床意义，因为它们是胰岛素刺激药物的一线靶标，例如用于治疗2型糖尿病的磺酰氟二氨基胺和格列本胺。 K（ATP）的严重功能收益突变是新原质糖尿病的主要原因，而在全基因组关联研究（GWAS）中，适度的功能性突变已与更温和的疾病联系起来，但更常见的疾病，更常见的疾病，成人 - 成人癌2型糖尿病。 相反，K（ATP）的功能丧失突变是家族性超胰岛素主义的主要原因，这是一种在儿童中发现的遗传性疾病，在儿童中，β细胞持续具有电活性并在正常葡萄糖面前分泌胰岛素，从而导致生命威胁生命的低血糖症。 有关胰岛素分泌对健康和疾病的振荡的重要性，请参见2015年报告中的参考文献3。 在几年的时间里，我们积累了大量支持该模型的间接证据，但是我们认为直接测试中心特征很重要，即糖酵解振荡。 我们的实验合作者通过修饰丙酮酸激酶（PK）开发了基于FRET的传感器。 PK结合果糖-1,6-磷酸（FBP），一种关键的糖酵解代谢物，该糖溶作代谢产物被DOM振荡。 先前的一篇论文证实了传感器（PKAR，用于丙酮酸激酶活性报告基因）确实振荡。 在当前时期，振荡的特性通过同时记录膜电位来更严格地探测它们，以确定它们之间的相位关系。 实验（参考＃1）再次证实了PKAR振荡，即使钙不振荡，也可以这样做，这也是该模型所预测的。 但是，相位关系与模型预测不一致：PKAR在振荡的活跃阶段下降，而由于糖酵解活性的脉冲，在整个活性阶段中预测它会很高。还成像了另外两个代谢物NAD（P）H和ATP，并显示出类似的模式。 预测和实验之间的差异令人震惊，但仅需要对模型进行一次重大修订才能解决。 加入了先前已知但被忽略的钙加速柠檬酸的作用。这增加了丙酮酸的线粒体消耗，使胞质FBP迅速地吸收了足以克服糖酵解中FBP产生的激增。 为了使ATP在活动阶段也下降的观察结果匹配，还必须假设在活性阶段钙泵消耗ATP足以克服由于刺激柠檬酸周期而增加的ATP产生的ATP。 这种有效的ATP消耗可加快主动阶段的终止，因为它允许K（ATP）通道重新打开。 将需要进一步的工作来测试修订后的模型产生的新预测，并充分了解这种更复杂的安排的好处。 α细胞： 胰腺细胞中胰高血糖素分泌的调节尚不清楚。已经提出，葡萄糖可以直接通过固有机制，细胞内或间接地通过外在机制抑制胰高血糖素的分泌。我们先前描述了一个用于分离的胰腺α细胞的数学模型，并将其用于研究调节胰高血糖素分泌的可能内在机制。我们证明葡萄糖可以通过ATP依赖性钾通道（K（ATP））和储存的电流（SOC）抑制胰高血糖素的分泌。现在，我们开发了一个胰岛模型，该模型将先前发布的α-和β细胞的数学模型与新的三角洲细胞模型结合在一起，并使用它来探索胰岛素和生长抑素对胰高血糖素分泌的影响。我们表明，该模型可以再现实验观察结果，即即使旁分泌调节剂不再作用于细胞，葡萄糖的抑制作用仍然存在。我们证明了旁分泌相互作用如何同步 - - 细胞在胰高血糖素和生长抑素分泌中产生脉动振荡，或者无法做到。该模型还可以解释矛盾的观察结果，即胰高血糖素可以与胰岛素过时，而α-细胞钙与胰岛素相相。我们得出的结论是，旁分泌相互作用和α细胞的内在机制都需要解释胰高血糖素分泌对葡萄糖的反应。