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，这是一种由于累积的能量过剩而导致的疾病。 摄入量大于能量消耗。要解决这一健康问题，重要的是确定新的监管机构 适合药物干预的能量动态平衡。我们的长期目标是 阐明Tankyrase(TNKS)是如何调节能量稳态的，TnKS是一种高尔基体相关酶，它可以 通过多聚ADP核糖化修饰底物蛋白质。此应用程序的目的是调查 Tankyrase在调节能量消耗中的作用，重点是燃料底物的分配 器官之间以及脂肪细胞的脂联素分泌。为此，我们使用了基因- 用诱捕技术在小鼠中建立Tnkyrase缺陷(TNKS-/-)模型。 我们发现，TNKS-/-小鼠增加了能量消耗，减少了肥胖，并 食物摄入量高于野生型对照。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，正在强劲增加。与已知的影响相一致 在TNKS-/-小鼠的肌肉中，脂联素显示介导分解代谢的基因上调 甘油三酯和脂肪酸。另一方面，这些小鼠的肝脏显示出上调的基因 促进甘油三酯的释放。基于这些和其他观察结果，我们假设 TNKS-/-小鼠能量消耗增加导致肝脏甘油三酯分泌增加， 它们被引导到肌肉中进行分解代谢，以响应高脂联素血症。在这份工作中 模型中，从肝脏到肌肉的脂质流量是以脂肪组织的储存为代价的，导致 尽管食物摄入量代偿性增加，TNKS-/-小鼠的瘦肉表型。 为了检验我们的工作假设，目标1将确定TNKS缺乏的程度 增加体内循环甘油三酯的生成和清除，以及肌肉的活动 体外水解甘油三酯和氧化脂肪酸。目标2将评估TNKS-/-的预测 由于能量消耗的增加，小鼠在以下情况下可以免受肥胖和脂肪毒性的影响 挑战高脂肪饮食。目标3将研究TnKS在脂联素中的脂肪特异性作用 分泌和能量动态平衡。初步研究表明，高脂联素血症 Tnks-/-小鼠是一种转录后效应，可以通过敲除3T3-L1中的TNKs来重现 脂肪细胞。我们将对3T3-L1脂肪细胞进行[35S]脉冲追逐分析，以测试预测 Tnks基因敲除可以稳定脂联素在分泌途径中的作用。我们还将使用条件 基因敲除方法确定脂肪特异性消融TNKS的程度 TNKS-/-小鼠的高脂联素血症及其他代谢表现。 这项拟议的研究有望阐明TNKS在脂联素分泌中的作用 能量动态平衡以及燃料底物在分解代谢和储存之间的分配。 这项申请的结果可能为进一步的研究提供基础，以验证TNKS是一种 抗肥胖治疗的药理靶点。

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.