Roles of Sphingolipids in the Pathophysiology of Obesity and Diabetes

描述(由申请人提供)： 肥胖会引发多种相关疾病，包括2型糖尿病、代谢综合征、心血管疾病、肝脏疾病等。这些疾病在退伍军人群体中的发病率高于总人群，因此，对这些疾病的预防和治疗研究仍然是退伍军人管理局研究的优先事项。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(肥胖者血浆中的脂肪酸升高)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，这是一种与炎症、迁移、趋化和其他关键细胞过程有关的脂质介质。我们假设SK1可能介导肥胖的病理生理学后果。为了在活体中测试这一点，我们在野生型和SK1-/-动物中实施了饮食诱导的肥胖模型。我们发现，SK1的消融可以减轻肥胖的许多病理后果。具体地说，我们观察到肥胖导致的促炎细胞因子水平降低，包括IL-6和MCP-1，这可能将肥胖与其下游病理联系起来。此外，我们还发现，消融SK1可以减弱高脂饮食诱导的免疫细胞在脂肪组织中的渗透。因此，我们假设SK1介导了肥胖症炎症的很大一部分，而炎症被认为是介导全身胰岛素抵抗的，因此，靶向SK1可能保护胰岛素抵抗。因此，我们建议1-通过检测野生型或SK1-/-小鼠中与肥胖相关的血浆细胞因子，并确定SK1-/-小鼠是否受到肥胖依赖的胰岛素抵抗的保护，来确定SK1和S1P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SK1-/-小鼠，并在这些动物及其对照组中实施高脂肪饮食，来测试脂肪细胞和免疫细胞SK1的贡献，并评估炎症和胰岛素抵抗。我们还将通过确定介导这些促炎事件的S1P受体及其信号效应器来确定脂肪中S1P的下游信号。然后我们提出了3-来确定HFF诱导SK1的机制。我们的数据表明，高脂肪喂养可能产生特定的磷脂酰胆碱(PC)物种，这些物种被认为是PPAR的新内源性配体。实现这些目标将揭示SK1在肥胖引起的炎症和IR中的作用，为我们理解生物活性脂类在肥胖症的病理生理中的作用提供重大进展，并有可能确定疾病治疗的新靶点。

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.