Role of endogenous lipids in the regulation of biphasic insulin secretion.

游离脂肪酸(FFA)有三个来源：1)外源性的FFA，2)内源性合成的FFA(从头脂肪生成(DNL))和3)从内部的甘油三酯储存中释放出来。DNL主要发生在肝细胞，然而，许多组织类型能够产生有限数量的脂类。这种少量的DNL在这些细胞类型中的作用尚不完全清楚。例如，胰腺的胰岛素分泌细胞表达的酶与葡萄糖暴露的量成比例地导致DNL。这种由葡萄糖驱动的DNL被认为是产生代谢信号分子的重要途径，而代谢信号分子对于调节胰岛素的胞吐作用非常重要。也有研究表明，甘油三酯(GL)/游离脂肪酸(FFA)从体内甘油三酯储存库循环也可能在调节胰岛素释放中发挥作用。抑制这一循环可抑制FFA对葡萄糖刺激的胰岛素释放的增强作用。我们已经发表的结果表明，操纵参与DNL的四种关键酶(PC、CL、ACC和Fas)和三种代谢载体(丙酮酸载体、柠檬酸盐载体和二羧酸盐载体)的效果会导致DNL在调节胰岛素分泌方面的正反两方面的结果相互矛盾。我们将继续使用实验室中新开发的工具来研究DNL在调节葡萄糖刺激的胰岛素释放中的作用。我们还鉴定了几种葡萄糖衍生的内源性脂质物种，它们可能是使用代谢组学方法调节双相胰岛素分泌的关键。这些代谢组学研究提出了许多问题，例如，这些葡萄糖衍生的内源性脂肪的来源是什么(例如，从甘油三酯(TG)储存或从DNL释放)，以及这些脂肪如何参与调节两相胰岛素的释放。我们将在这些研究的基础上进一步研究内源性脂质在调节双相胰岛素释放中的作用。*假设：内源性脂类产生信号分子，对双相胰岛素分泌的代谢调节至关重要。*实验方法：我们利用代谢组学方法鉴定了几种内源性脂类，它们可能对调节双相胰岛素分泌至关重要。我们将使用分子克隆技术、siRNAs和siRNA腺病毒、代谢分析、酶分析、分泌分析、荧光成像和代谢组学来测量燃料调节分泌的关键内分泌模型中的代谢物分布和代谢通量。这些方法的结合将使我们能够研究DNL对双相胰岛素分泌的代谢调节的方方面面。*新颖性和意义：众所周知，外源性脂类调节胰岛素的分泌，但内源性的作用尚不清楚。这些研究将为理解脂类在胞吐调节中的独特作用提供宝贵的见解。

There are three sources of free fatty acids (FFA) 1) exogenously-derived FFAs, 2) endogenously-synthesized FFAs (de novo lipogenesis (DNL)) and 3) release from internal triglyceride stores. DNL occurs primarily in liver cells, however, many tissue types are able to produce limited amounts of lipid. The role of this small amount of DNL in these cell types is not completely understood. For example, insulin secreting cells of the pancreas express enzymes that lead to DNL in proportion to the amount of glucose exposure. This glucose driven DNL has been proposed to be important in generating metabolic signaling molecules important for regulating insulin exocytosis. It has also been suggested that glycerolipid (GL)/ FFA cycling from internal triglyceride stores may also play a role in the regulation of insulin release. Inhibition of this cycling suppresses FFA augmentation of glucose-stimulated insulin release. We have published results showing that the effects of manipulating four key enzymes (PC, CL, ACC and FAS) and three metabolic carriers (pyruvate carrier, citrate carrier and dicarboxylate carrier) that are involved in DNL lead to conflicting results for and against a role of DNL in regulating insulin exocytosis. We will continue to investigate the role of DNL in the regulation of glucose-stimulated insulin release using newly developed tools in the lab. We have also identified several glucose derived endogenous lipid species that may be critical for regulating biphasic insulin secretion using a metabolomics approach. A number of questions arise from these metabolomics studies for example what is the source of these glucose derived endogenous lipids (e.g. release from triglyceride (TG) stores or from DNL) and how might these lipids be involved in regulating biphasic insulin release. We will expand on these studies to further investigate the role of endogenous lipids in the regulation of biphasic insulin release. ***Hypothesis: Endogenous lipids generate signaling molecules that are critical to the metabolic regulation of biphasic insulin secretion.***Experimental approach: We have identified several endogenous lipid species that may be critical for regulating biphasic insulin secretion using a metabolomics approach. We will use molecule cloning techniques, siRNAs and siRNA adenoviruses, metabolic assays, enzymatic assays, secretion assays, fluorescent imaging and metabolomics to measure metabolite profiles and metabolic fluxes in key endocrine models of fuel regulated secretion. The combination of these approaches will allow us to study all aspects of the metabolic regulation of biphasic insulin secretion by DNL.***Novelty and significance: It is well known that exogenous lipids regulate insulin secretion but the role of endogenous is less well defined. These studies will provide invaluable insights towards understanding the unique role of lipids play in the regulation of exocytosis.