Roles of Sphingolipids in the Pathophysiology of Obesity and Diabetes

描述（由申请人提供）： 肥胖会诱发多种相关疾病，包括2型糖尿病、代谢综合征、心血管疾病、肝病和许多其他疾病。这些条件有更多的发生在退伍军人人口比总人口，因此，研究这些条件的预防和治疗仍然是VA研究的高度优先事项。该奖项的前一个资助期使我们能够做出新的发现，即脂肪酸（在肥胖个体的血浆中升高）增加了培养的骨骼肌细胞中鞘氨醇激酶1的表达。这一事件增加了肌肉中鞘氨醇-1-磷酸的含量，鞘氨醇-1-磷酸是一种与炎症、迁移、趋化性和其他关键细胞过程有关的脂质介质。我们推测SK 1可能介导肥胖的病理生理后果。为了在体内测试这一点，我们在野生型和SK 1-/-动物中实施了饮食诱导的肥胖模型。我们发现，许多肥胖的病理后果被削弱的SK 1消融。具体来说，我们观察到肥胖诱导的促炎细胞因子（包括IL-6和MCP-1）水平降低，这可能将肥胖与其下游病理学联系起来。此外，我们发现SK 1的消融减弱了脂肪组织中高脂饮食诱导的免疫细胞浸润。因此，我们假设SK 1介导了肥胖症中被认为介导全身性胰岛素抵抗的炎症的重要部分，因此，靶向SK 1可以保护免受胰岛素抵抗。因此，我们提出1-通过测量野生型或SK 1-/-小鼠中与肥胖相关的血浆细胞因子，并确定SK 1-/-小鼠是否受到肥胖依赖性胰岛素抵抗的保护，来确定SK 1和S1 P在体内肥胖诱导的炎症和随后的胰岛素抵抗中的作用。我们将通过产生脂肪细胞特异性和免疫细胞特异性SK 1-/-小鼠并在这些动物及其对照中实施高脂肪饮食来测试脂肪细胞与免疫细胞SK 1的贡献，并评估炎症和胰岛素抵抗。我们还将通过确定S1 P受体及其介导这些促炎事件的信号效应物来确定脂肪中S1 P的下游信号传导。然后，我们提出3-确定HFF诱导SK 1的机制。我们的数据表明，高脂肪喂养可能会产生特定的磷脂酰胆碱（PC）种类，这些种类被认为是PPAR？的新型内源性配体。实现这些目标将揭示SK 1在肥胖诱导的炎症和IR中的作用，为我们理解生物活性脂质在肥胖病理生理学中的作用提供重大进展，并可能确定疾病治疗的新治疗靶点。

DESCRIPTION (provided by applicant): Obesity precipitates a variety of associated disease including Type 2 Diabetes, the Metabolic Syndrome, Cardiovascular Disease, Liver Disease, and many others. These conditions have greater occurrence in the Veteran population than in the total population, and thus, research into prevention and treatment of these conditions remains a high priority of VA research. The previous funding period of this award enabled us to make the novel discovery that fatty acids (which are elevated in plasma in obese individuals) increase the expression of sphingosine kinase 1 in cultured skeletal muscle cells. This event elevated muscle content of sphingosine-1-phosphate, a lipid mediator implicated in inflammation, migration, chemotaxis, and other key cell processes. We hypothesized that SK1 may mediate the pathophysiolgical consequences of obesity. To test this in vivo, we implemented a diet-induced obesity model in wild type and SK1-/- animals. We found that many pathological consequences of obesity were attenuated by ablation of SK1. Specifically, we observed decreased levels of obesity-indcued proinflammatory cytokines including IL-6 and MCP-1, which may link obesity to its downstream pathology. Moreover, we found that ablation of SK1 attenuated high-fat diet-induced immune cell infiltrate in adipose tissue. We thus hypothesize that SK1 mediates a significant portion of the inflammation in obesity that is thought to mediate systemic insulin resistance, and, thus, targeting SK1 may protect from insulin resistance. Thus, we propose 1-To determine the role of SK1 and S1P in obesity-induced inflammation and subsequent insulin resistance in vivo by measuring plasma cytokines associated with obesity in wild type or SK1-/- mice, and determining whether SK1-/- mice are protected from obesity-dependent insulin resistance. We will test the contribution of adipocyte vs. immune cell SK1 by generating adipocyte-specific and immune cell-specific SK1-/- mice and implementing the high fat diet in these animals and their controls and evaluate inflammation and insulin resistance. We will also 2-determine the downstream signaling of S1P in adipose by determining the S1P receptors and their signaling effectors that mediate these pro-inflammatory events. We then propose 3-to determine the mechanism by which HFF induces SK1. Our data indicate that high fat feeding may generate specific phosphatidylcholine (PC) species that have been implicated as novel endogenous ligands for PPAR¿. Accomplishing these aims will reveal the role of SK1 in obesity induced inflammation and IR, providing a significant advance in our understanding of the roles of bioactive lipids in the pathophysiology of obesity, and potentially identifying novel therapeutic targets for disease treatment.