Dynamic regulation of hepatic SIK1 during fasting and feeding

禁食和进食期间肝脏SIK1的动态调节

• 批准号: 8162022
• 负责人: Rebecca L Berdeaux
• 金额: $ 37万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-27 至 2016-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8162022
• 关键词: Activator Appliances; Address; Affect; American; Back; Blood Glucose; Chronic; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclic AMP-Responsive DNA-Binding Protein; Diabetes Mellitus; Diabetic mouse; Diet; Disease; Environment; Enzymes; Equilibrium; Excision; Family; Fasting; Fatty acid glycerol esters; Feedback; Feeds; Figs - dietary; Genes; Genetic Techniques; Genetic Transcription; Glucagon; Goals; Hepatic; Hepatocyte; Hormones; Hyperglycemia; Insulin; Knock-out; Knockout Mice; Lead; Liver; Luciferases; Maintenance; Mammals; Messenger RNA; Metabolic; Metabolism; Molecular; Molecular Genetics; Mus; Nature; Non-Insulin-Dependent Diabetes Mellitus; Normal tissue morphology; Nutritional; Obesity; Organ; Pathway interactions; Patients; Pattern; Peripheral; Phenotype; Phosphotransferases; Physiological; Play; Postprandial Period; Prevention; Proteins; Public Health; Regulation; Reporter; Rodent; Role; Signal Transduction; Skeletal Muscle; Stimulus; Testing; Time; Tissues; Transgenic Animals; Transgenic Organisms; Ubiquitin; United States; Work; base; blood glucose regulation; diabetic; diabetic patient; feeding; glucose output; glucose production; glucose uptake; hepatic gluconeogenesis; in vivo; inhibitor/antagonist; insight; lipid biosynthesis; mouse model; multicatalytic endopeptidase complex; new therapeutic target; novel therapeutics; protein expression; research study; response; salt-inducible kinase; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): Elevated hepatic glucose output during fasting is a major contributor to type 2 diabetes, which affects 10-25% of Americans. The cAMP response element binding protein CREB and its co-activator CRTC2 regulate hepatic glucose output by transcriptional induction of rate-limiting gluconeogenic enzymes during fasting. Given that CREB activity becomes aberrantly activated in diabetic rodents, we aim to identify molecular mechanisms by which this pathway can be inhibited. Recent studies in mouse models and cultured hepatocytes implicated a family of AMPK-related kinases called Salt-Inducible Kinases (SIK1-3), in the control of CRTC co-activator function during fasting and re-feeding. Among these, SIK1 is unique in that fasting stimuli induce hepatic SIK1 mRNA transcription. SIK1 protein then feeds back to inhibit CREB/CRTC2 and glucose output after a meal. This cycle is reset during the postprandial period, during which SIK1 protein levels decline, thus allowing re- activation of CREB at the onset of the next fast. Based on the temporal nature of SIK1 expression and its potent inhibitory effects on hepatic glucose output, we hypothesize that the timing of SIK1 activity is limited by regulated degradation during the fasting to feeding transition. We propose to test this hypothesis using a variety of molecular and genetic techniques. We will investigate the dynamics of SIK1 activity in hepatocytes and liver tissue and explore the structural determinants of SIK1 that regulate its degradation. We will also test the role of a candidate E3 ubiquitin ligase in limiting SIK1 activity during the postprandial period. Finally, we will characterize metabolic phenotypes resulting from liver-specific deletion of the Sik1 gene in mice. We have generated several transgenic animal strains for these studies, including transgenic luciferase reporter mice to visualize CREB-dependent transcription in vivo. The goal of this work is to determine how dynamic regulation of SIK1 contributes to maintenance of glucose homeostasis and identify new molecular mechanisms by which SIK1 activity is regulated. Molecular insight into this pathway will reveal new therapeutic strategies for inhibition of hepatic glucose output in diabetic patients. PUBLIC HEALTH RELEVANCE: Inappropriate regulation of blood glucose is the hallmark of diabetes mellitus, which is a growing public health problem in the United States. The liver is a major organ in which glucose regulation occurs. This project addresses the molecular regulation of an enzyme that normally functions in the liver to turn off glucose production. This study aims to identify novel therapeutic targets for treatment of diabetes.

描述（由申请人提供）：禁食期间肝葡萄糖产量升高是2型糖尿病的主要因素，这影响了10-25％的美国人。 cAMP响应元件结合蛋白CREB及其共激活因子CRTC2通过在禁食过程中的转录限制糖生成酶来调节肝葡萄糖输出。鉴于CREB活性在糖尿病啮齿动物中异常激活，我们旨在鉴定可以抑制该途径的分子机制。在小鼠模型和培养的肝细胞中的最新研究暗示了一种称为盐诱导激酶（SIK1-3）的与AMPK相关的激酶家族，在禁食和重新喂养过程中CRTC共激活器功能的控制。其中，SIK1是独一无二的，因为禁食刺激诱导肝SIK1 mRNA转录。然后，SIK1蛋白会反馈以抑制餐后CREB/CRTC2和葡萄糖输出。该周期是在餐后重置的，在此期间，SIK1蛋白水平下降，从而使CREB在下一个快速开始时允许CREB激活。基于SIK1表达的时间性质及其对肝葡萄糖输出的有效抑制作用，我们假设SIK1活性的时机受到禁食期间对喂养过渡的调节降解的限制。我们建议使用各种分子和遗传技术检验这一假设。我们将研究肝细胞和肝组织中SIK1活性的动力学，并探索调节其降解的SIK1的结构决定因素。我们还将测试候选E3泛素连接酶在餐后限制SIK1活性中的作用。最后，我们将表征由小鼠SIK1基因的肝脏特异性缺失引起的代谢表型。我们已经为这些研究产生了几种转基因动物菌株，包括转基因荧光素酶报道小鼠，以可视化体内CREB依赖性转录。这项工作的目的是确定SIK1的动态调节如何有助于维持葡萄糖稳态，并确定调节SIK1活性的新分子机制。对该途径的分子洞察力将揭示糖尿病患者抑制肝葡萄糖输出的新治疗策略。 公共卫生相关性：不适当的血糖调节是糖尿病的标志，这是美国日益增长的公共卫生问题。肝脏是发生葡萄糖调节的主要器官。该项目解决了通常在肝脏中起作用以关闭葡萄糖产生的酶的分子调节。这项研究旨在确定用于治疗糖尿病的新型治疗靶标。