Regulation of energy homeostasis and adiposity by a Golgi-associated PARP enzyme

项目摘要 许多退伍军人患有肥胖症，这是一种由于能量累积过剩而导致的疾病 摄入量超过能量消耗。为了解决这一健康问题，重要的是要确定新的监管机构， 能量稳态，这是经得起药物干预。我们的长期目标是 阐明如何能量稳态是由端锚聚合酶（TNKS），高尔基体相关酶， 通过聚ADP核糖基化修饰底物蛋白。本申请的目的是调查 端锚聚合酶在调节能量消耗中的作用 以及脂肪细胞分泌脂联素。为此，我们使用了基因- 在小鼠中使用捕获技术以产生端锚聚合酶缺陷（TNKS-/-）模型。 我们发现TNKS-/-小鼠的能量消耗增加，肥胖减少， 食物摄入量比野生型对照组。有趣的是，他们的血浆脂联素水平，特别是 生物活性的高分子量形式，被稳健地增加。与已知的 TNKS-/-小鼠中的脂联素、肌肉显示介导脂联素的基因上调， 甘油三酯和脂肪酸。另一方面，这些小鼠的肝脏显示出基因的上调， 促进甘油三酯释放。基于这些和其他观察，我们假设， TNKS-/-小鼠中增加的能量消耗导致甘油三酯的肝分泌增加， 其被引导至肌肉以响应于高脂联素血症而进行catalysis。本工作 模型中，从肝脏到肌肉的脂质通量是以脂肪组织中的储存为代价的， TNKS-/-小鼠的瘦表型，尽管食物摄入量代偿性增加。 为了检验我们的工作假设，目标1将确定TNKS缺陷的程度， 增加体内循环甘油三酯的产生和清除以及肌肉的活性 离体水解甘油三酯和氧化脂肪酸。目标2将评估TNKS-/- 由于增加的能量消耗，小鼠在以下情况下被保护免于肥胖和脂毒性： 挑战高脂肪饮食。目的3探讨TNKS在脂联素中的脂肪特异性作用 分泌和能量平衡。初步研究表明， TNKS-/-小鼠是一种转录后效应，可以通过敲低3T3-L1中的TNKS来重现。 脂肪细胞我们将对3T3-L1脂肪细胞应用[35S]脉冲追踪分析，以测试以下预测： TNKS敲低稳定分泌途径中的脂联素。我们还将使用条件 基因敲除方法来确定TNKS脂肪特异性消融的程度， TNKS-/-小鼠的高脂联素血症和其他代谢表现。 这些研究为TNKS在脂联素分泌中的作用提供了新的思路 和能量稳态以及燃料基质在催化剂和储存之间的分配。 这项应用的结果可能为进一步的研究提供基础，以验证TNKS作为一种 抗肥胖治疗的药理学靶点。

Project Summary Many veterans suffer from obesity, an illness that results from a cumulative excess of energy intake over energy expenditure. To combat this health issue, it is important to identify novel regulators of energy homeostasis that are amenable to pharmacological intervention. Our long-term goal is to elucidate how energy homeostasis is regulated by tankyrase (TNKS), a Golgi-associated enzyme that modifies substrate proteins through poly-ADP-ribosylation. The aim of this application is to investigate the role of tankyrase in regulating energy expenditure with an emphasis on fuel substrate partitioning between organs as well as adiponectin secretion from adipocytes. To this end, we have used the gene- trapping technique in mice to create a tankyrase deficient (TNKS -/-) model. We found that TNKS -/- mice have increased energy expenditure, reduced adiposity, and greater food intake than wild-type controls. Intriguingly, their plasma levels of adiponectin, particularly the bioactive high molecular-weight form, are robustly increased. Consistent with the known effect of adiponectin, muscle in TNKS -/- mice shows an upregulation of genes that mediate the catabolism of triglycerides and fatty acids. On the other hand, liver in these mice shows an upregulation of genes that promote triglyceride release. Based on these and other observations, we hypothesize that the heightened energy expenditure in TNKS -/- mice entails increased hepatic secretion of triglycerides, which are channeled to the muscle for catabolism in response to hyperadiponectinemia. In this working model, the lipid flux from liver to muscle is at the expense of storage in adipose tissue, resulting in the lean phenotype of TNKS -/- mice despite a compensatory increase in food intake. To test our working hypothesis, Aim 1 will determine the extent to which TNKS deficiency increases the production and clearance of circulating triglycerides in vivo as well as the activity of muscle to hydrolyze triglycerides and oxidize fatty acids ex vivo. Aim 2 will evaluate the prediction that TNKS -/- mice, owing to increased energy expenditure, are protected from obesity and lipotoxicity when challenged with a high fat diet. Aim 3 will investigate the adipose-specific roles of TNKS in adiponectin secretion and energy homeostasis. Preliminary studies have shown that the hyperadiponectinemia of TNKS -/- mice is a post-transcriptional effect and can be recapitulated by knocking down TNKS in 3T3-L1 adipocytes. We will apply [35S] pulse-chase analysis to 3T3-L1 adipocytes to test the prediction that TNKS knockdown stabilizes adiponectin in the secretory pathway. We will also use the conditional knockout approach to determine the extent to which adipose-specific ablation of TNKS recapitulates the hyperadiponectinemia and other metabolic manifestations of TNKS -/- mice. The proposed studies are expected to shed light on the roles of TNKS in adiponectin secretion and energy homeostasis as well as the partitioning of fuel substrates between catabolism and storage. Outcomes from this application may provide the foundation for additional studies that validate TNKS as a pharmacological target for anti-obesity therapy.