The role of ceramide in obesity-related vascular dysfunction

神经酰胺在肥胖相关血管功能障碍中的作用

• 批准号: 7364527
• 负责人: John David SYMONS
• 金额: $ 22.43万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7364527
• 关键词: Area; Atherosclerosis; Biological Availability; Blood Vessels; Bos taurus; Cardiovascular system; Cattle; Cell Line; Ceramides; Data; Defect; Development; Diet; Disruption; Endothelial Cells; Endothelin-1; Endothelium; Enzymes; Equilibrium; Event; Fatty acid glycerol esters; Functional disorder; Genetic; Hypertension; Insulin; Insulin Resistance; Knock-out; Knockout Mice; Laboratories; Mediating; Metabolic; Metabolic syndrome; Mitogen-Activated Protein Kinases; Modeling; Mus; Nitric Oxide; Nitric Oxide Synthase; Non-Insulin-Dependent Diabetes Mellitus; Obesity; Pathogenesis; Peroxonitrite; Phosphorylation; Phosphotransferases; Production; Proto-Oncogene Proteins c-akt; Rate; Reactive Oxygen Species; Role; Secondary to; Signal Transduction; Sphingolipids; Superoxides; System; Testing; Vasodilation; base; defined contribution; design; dihydroceramide desaturase; feeding; human NOS3 protein; insight; insulin signaling; novel; prevent; research study; tool; upstream kinase

DESCRIPTION (provided by applicant): Insulin resistance is a crucially important metabolic abnormality in diet-induced obesity and type 2 diabetes. Endothelial dysfunction exists in insulin-resistant states and may represent an important early event in the development of atherosclerosis. Reduced endothelium-derived nitric oxide (NO) contributes to endothelial dysfunction. The bioavailability of NO depends on a fine balance between NO production via endothelial NO synthase (eNOS) and inactivation of NO by reactive oxygen species such as superoxide anion (O2-). Endothelial production of NO requires the phosphorylation of specific eNOS residues by Akt/protein kinase B (Akt) and other upstream kinases, as well as the formation of eNOS homodimers. Based on our preliminary results and data from others, endothelial dysfunction that exists in mice with diet-induced obesity might be precipitated by impaired Akt-mediated eNOS phosphorylation in the vasculature and by the disruption of eNOS homodimers secondary to increased superoxide (O2-) production. We will test the overall hypothesis that accumulation of the sphingolipid ceramide contributes importantly to the pathogenesis of vascular dysfunction in insulin resistant states by reducing NO production via both of these mechanisms. In Aim 1 we will determine if increasing ceramide concentrations in bovine aortic endothelial cells (BAECs) impairs insulin signaling and decreases eNOS function. Two hypotheses will be tested: 1) Ceramide antagonizes insulin-mediated Akt and eNOS phosphorylation and stimulates MAPK signaling resulting in reduced NO production and increased endothelin-1 production by BAECs; and 2) Ceramide increases O2- to an extent that peroxynitrite formation disrupts eNOS homodimers and leads to reduced NO production by BAECs. In Aim 2 we will define the contribution from ceramide to impaired insulin-mediated signal transduction in the vasculature, reduced endothelium-dependent vasorelaxation, and systemic hypertension that we have observed in mice with diet- induced obesity. Two hypotheses will be tested in mice with diet-induced obesity: 1) Ceramide accumulation reduces NO bioavailability by impairing insulin-mediated Akt phosphorylation and eNOS phosphorylation in the vasculature; and 2) Ceramide accumulation reduces NO bioavailability by potentiating O2- -induced peroxynitrite formation which ultimately disrupts eNOS homodimer formation in the vasculature. Two strategies will be used to limit ceramide accumulation in mice with diet-induced obesity: pharmacological inhibition of the rate-limiting enzyme responsible for ceramide synthesis; and a novel knockout model wherein ceramide synthesis is prevented. Information generated by testing our hypotheses will provide important insight into understanding the contribution from ceramide to cardiovascular defects that exist in mice with diet-induced obesity.

描述（由申请人提供）：胰岛素抵抗是饮食引起的肥胖和 2 型糖尿病中至关重要的代谢异常。内皮功能障碍存在于胰岛素抵抗状态，并且可能代表动脉粥样硬化发展中的重要早期事件。内皮源性一氧化氮 (NO) 减少会导致内皮功能障碍。 NO 的生物利用度取决于内皮 NO 合酶 (eNOS) 产生的 NO 与超氧阴离子 (O2-) 等活性氧物质灭活 NO 之间的良好平衡。内皮细胞产生 NO 需要 Akt/蛋白激酶 B (Akt) 和其他上游激酶磷酸化特定的 eNOS 残基，以及形成 eNOS 同二聚体。根据我们的初步结果和其他人的数据，饮食诱发的肥胖小鼠中存在的内皮功能障碍可能是由于血管系统中 Akt 介导的 eNOS 磷酸化受损以及超氧化物 (O2-) 产生增加继发的 eNOS 同型二聚体破坏所致。 。我们将检验总体假设，即鞘脂神经酰胺的积累通过这两种机制减少 NO 的产生，从而对胰岛素抵抗状态下血管功能障碍的发病机制发挥重要作用。在目标 1 中，我们将确定增加牛主动脉内皮细胞 (BAEC) 中的神经酰胺浓度是否会损害胰岛素信号传导并降低 eNOS 功能。将测试两个假设：1) 神经酰胺拮抗胰岛素介导的 Akt 和 eNOS 磷酸化并刺激 MAPK 信号传导，导致 BAEC 产生 NO 产生减少和内皮素 1 产生增加； 2) 神经酰胺将 O2- 增加到过氧亚硝酸盐形成破坏 eNOS 同二聚体并导致 BAEC 产生 NO 减少的程度。在目标 2 中，我们将定义神经酰胺对脉管系统中胰岛素介导的信号转导受损、内皮依赖性血管舒张作用减少以及我们在饮食诱导肥胖小鼠中观察到的全身性高血压的贡献。将在饮食诱导肥胖的小鼠中测试两个假设：1）神经酰胺积累通过损害脉管系统中胰岛素介导的 Akt 磷酸化和 eNOS 磷酸化来降低 NO 生物利用度； 2) 神经酰胺的积累通过增强 O2 诱导的过氧亚硝酸盐的形成来降低 NO 的生物利用度，最终破坏脉管系统中 eNOS 同二聚体的形成。将使用两种策略来限制饮食引起的肥胖小鼠中的神经酰胺积累：药物抑制负责神经酰胺合成的限速酶；以及一种新的基因敲除模型，其中神经酰胺的合成被阻止。通过测试我们的假设产生的信息将为了解神经酰胺对饮食引起的肥胖小鼠中存在的心血管缺陷的影响提供重要的见解。