Sphingosine-1-phosphate Signaling and the Chronic Glucocorticoid Exposure Induced Glucose Homeostasis Disorder

1-磷酸鞘氨醇信号转导和慢性糖皮质激素暴露引起的血糖稳态紊乱

• 批准号: 10345112
• 负责人: Jen-Chywan Wang
• 金额: $ 39.26万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-22 至 2026-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10345112
• 关键词: Affect; Agonist; Attenuated; Binding; Biological Assay; Cells; Cholesterol; Chronic; Disease; Enzymes; Exposure to; Extracellular Space; Functional disorder; Gene Expression; Gene Expression Profiling; Genes; Genetic Transcription; Glucocorticoid Receptor; Glucocorticoids; Gluconeogenesis; Glucose; Hepatic; Hepatocyte; Hyperglycemia; Immune; Inflammatory; Knockout Mice; Knowledge; Liver; MAPK1 gene; MAPK3 gene; Mediating; Membrane; Metabolic Diseases; Metabolism; Modeling; Mus; Non-Insulin-Dependent Diabetes Mellitus; Orphan; Pathway interactions; Patients; Pharmacotherapy; Physiological; Play; Production; Pyruvate; Rattus; Regulation; Response Elements; Role; SPHK1 enzyme; Signal Transduction; Signaling Molecule; Sphingosine; Sphingosine-1-Phosphate Receptor; Steroids; Stress; Surface; Testing; Therapeutic Intervention; base; blood glucose regulation; cholesterol biosynthesis; chromatin immunoprecipitation; comorbidity; extracellular; genome-wide; hepatic gluconeogenesis; hepatoma cell; improved; in vivo; inhibitor/antagonist; insight; knock-down; new therapeutic target; novel; overexpression; receptor; recruit; response; sphingosine 1-phosphate; sphingosine kinase; transcriptome

SUMMARY Chronic and/or excess glucocorticoid (GC) exposure, such as prolonged stress and long-term GC therapy, causes metabolic disorders including hyperglycemia. Intracellular GC receptor (GR) has been shown to directly stimulate the transcription of gluconeogenic genes, such as Pck1 and G6pc, to promote gluconeogenesis. However, chronic GC exposure can induce additional mechanisms to further enhance hepatic gluconeogenesis. Our preliminary studies found that chronic GC exposure elevated hepatic sphingosine-1-phosphate (S1P) levels. S1P is exported to the extracellular surface and binds to membrane S1P receptors (S1PRs) to exert its actions. We found that reducing S1PR2 expression in mouse liver attenuated chronic GC exposure-promoted gluconeogenesis. Activating S1PR2 in hepatoma cells enhanced GC-induced Pck1 and G6pc expression. Chromatin immunoprecipitation assay found that GC-induced GR recruitment to the GC response elements (GREs) of Pck1 and G6pc was reduced by hepatic S1PR2 knockdown. Global gene expression analysis identified that RAR-related orphan receptor C (Rorc) expression was reduced by hepatic S1PR2 knockdown. Rorc antagonist attenuated GC-induced gluconeogenic gene expression in hepatoma cells and overexpressing Rorc in the liver of hepatic S1PR2 knockout mice enhanced GC-induced GR recruitment to the Pck1 and G6pc GREs as well as their expression. Intriguingly, GC suppressed Rorc expression, which was antagonized by S1PR2 signaling. Based on these results, we hypothesize that chronic GC exposure activates S1PR2 signaling to enhance GC-induced gluconeogenesis by inhibiting GC’s suppressive effect on the expression of Rorc, which can act with GR to strongly augment gluconeogenic gene transcription. In Aim 1, we will test if altering intracellular S1P levels in hepatocytes affects chronic GC treatment-induced hyperglycemia by overexpressing or knocking down Sphk1 and Sphk2 (both convert sphingosine to S1P), Sgpl1 (hydrolyzes S1P) and Spns2 (exports S1P to extracellular space) in mouse liver. In Aim 2, we will establish Rorc’s in GC-induced hepatic gluconeogenesis by reducing hepatic Rorc expression or treating mice with Rorc antagonist. Notably, 4a- carboxy, 4b-methyl-zymosterol (4ACD8), a metabolite of cholesterol biosynthesis, has been shown to be a Rorc agonist. We will investigate whether reducing the expression of Sc4mol, an enzyme generating 4ACD8, attenuates the GC effect on hepatic gluconeogenesis. In Aim 3, we will identify signaling molecules activated by S1PR2 that participate in GC regulation of gluconeogenic genes and Rorc expression. We will also analyze the role of Rorc in GR regulated global hepatic gene transcription. Finally, how GC and S1PR2 signaling regulate Rorc expression will be investigated. Overall, the proposed studies will establish a novel S1PR2-Rorc axis induced specifically upon chronic GC exposure to enhance GC activated gluconeogenesis. Not only will this knowledge advance our understand on pathophysiology of chronic GC exposure, but it also will provide novel targets for therapeutic intervention against steroid induced hyperglycemia.

概括 慢性和/或超过糖皮质激素（GC）暴露，例如长期应激和长期GC治疗， 导致包括高血糖在内的代谢疾病。细胞内GC受体（GR）已显示直接 刺激糖原性基因（例如PCK1和G6PC）的转录，以促进糖异生。 然而，慢性GC暴露会引起其他机制，以进一步增强肝葡萄糖性。 我们的初步研究发现，慢性GC暴露升高肝鞘氨醇1-磷酸盐（S1P）水平。 S1P被导出到细胞外表面，并与膜S1P受体（S1PR）结合以发挥其作用。 我们发现减少小鼠肝脏中S1PR2的表达减弱了慢性GC暴露促进 糖异生。激活肝癌细胞中的S1PR2增强了GC诱导的PCK1和G6PC表达。 染色质免疫沉淀试验发现GC诱导的GR募集到GC响应元件 PCK1和G6PC的（GRE）通过肝S1PR2敲低降低。全球基因表达分析 识别与RAR相关的孤儿受体C（RORC）的表达通过肝S1PR2敲低降低。 RORC拮抗剂减弱了GC诱导的肝癌细胞中的糖原性基因表达和过表达 肝S1PR2敲除小鼠的肝脏中的RORC增强了GC引起的GR募集到PCK1和G6PC Gres及其表达。有趣的是，GC抑制了RORC的表达，这是由 S1PR2信号传导。基于这些结果，我们假设慢性GC暴露激活S1PR2信号传导 通过抑制GC对RORC表达的抑制作用来增强GC诱导的糖异生，该作用 可以用GR起作用以强烈增强糖原性基因转录。在AIM 1中，我们将测试是否更改 肝细胞中的细胞内S1P水平通过过表达来影响慢性GC治疗诱导的高血糖症 或击倒SPHK1和SPHK2（都将鞘氨酸转换为S1P），SGPL1（水解S1P）和SPNS2 （将S1P导出到细胞外空间）在小鼠肝脏中。在AIM 2中，我们将在GC引起的肝脏中建立RORC 通过减少肝RORC表达或用RORC拮抗剂治疗小鼠，糖异生。值得注意的是，4a- 羧酸含胆固醇生物合成的代谢产物，羧基，4b-甲基 - 齐甲蛋白酶（4ACD8）已被证明是RORC 激动剂。我们将调查是否降低SC4mol的表达，即产生4ACD8的酶， 减弱了GC对肝肝脏的影响。在AIM 3中，我们将确定由 参与糖原性基因和RORC表达的GC调节的S1PR2。我们还将分析 RORC在GR调节的全局肝基因转录中的作用。最后，GC和S1PR2信号如何调节 将研究RORC的表达。总体而言，拟议的研究将建立新的S1PR2-RORC轴 慢性GC暴露以增强GC激活的葡萄糖发生后，诱导的。不仅会 知识促进了我们对慢性GC暴露的病理生理学的理解，但它也将提供新颖 针对类固醇诱导的高血糖的治疗干预靶标。