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

描述（由申请人提供）： 许多退伍军人患有肥胖症，这是一种由于能量摄入累积超过能量消耗而导致的疾病。为了解决这一健康问题，重要的是要确定新的调节剂的能量稳态，是经得起药物干预。我们的长期目标是阐明如何调节能量稳态的端锚聚合酶（TNKS），高尔基体相关的酶，通过多聚ADP核糖基化修饰底物蛋白。本申请的目的是研究端锚聚合酶在调节能量消耗中的作用，重点是器官之间的燃料底物分配以及脂肪细胞的脂联素分泌。为此，我们在小鼠中使用基因捕获技术来创建端锚聚合酶缺陷（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更多。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，强劲增加。与脂联素的已知作用一致，TNKS -/-小鼠的肌肉显示介导甘油三酯和脂肪酸分解的基因上调。另一方面，这些小鼠的肝脏显示促进甘油三酯释放的基因上调。基于这些和其他观察结果，我们假设TNKS -/-小鼠的能量消耗增加导致甘油三酯的肝脏分泌增加，甘油三酯被引导到肌肉中，以响应高脂联素血症。在该工作模型中，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，导致TNKS -/-小鼠的瘦表型，尽管食物摄入量补偿性增加。 为了检验我们的工作假设，目标1将确定TNKS缺乏增加体内循环甘油三酯的产生和清除以及肌肉水解甘油三酯和氧化脂肪酸的活性的程度。目标2将评估TNKS -/-小鼠，由于增加的能量消耗，被保护免受肥胖和脂毒性时，用高脂肪饮食挑战的预测。目的3探讨TNKS在脂联素分泌和能量平衡中的作用。初步研究表明，TNKS -/-小鼠的高脂联素血症是一种转录后效应，可以通过敲低3 T3-L1脂肪细胞中的TNKS来重现。我们将对3 T3-L1脂肪细胞应用[35 S]脉冲追踪分析来测试TNKS敲低稳定分泌途径中的脂联素的预测。我们还将使用条件性基因敲除方法来确定TNKS脂肪特异性消融在多大程度上重现TNKS -/-小鼠的高脂联素血症和其他代谢表现。 这些研究有望揭示TNKS在脂联素分泌和能量稳态中的作用，以及燃料底物在催化剂和储存之间的分配。该应用的结果可能为验证TNKS作为抗肥胖治疗的药理学靶点的其他研究提供基础。 公共卫生相关性： 饮食中摄入的热量超过能量消耗的热量会以脂肪的形式储存在脂肪组织中。热量摄入过多的长期后果是肥胖，这是2型糖尿病、心脏病发作和其他严重并发症的主要风险因素。根据最近的一项调查，在退伍军人事务部医疗设施服务的人口中，肥胖影响了多达37%的妇女和33%的男子。因此，改善肥胖对许多退伍军人的健康很重要。使用小鼠模型来探索肥胖的调节，我们已经观察到当一种称为端锚聚合酶的细胞蛋白失活时的瘦表型。我们的数据表明，这些端锚聚合酶缺陷的小鼠是瘦的，因为增加的能量消耗。我们建议研究缺乏端锚聚合酶功能导致能量消耗增加的分子机制。我们的长期目标是建立端锚聚合酶作为治疗肥胖症的药理学靶点。

DESCRIPTION (provided by applicant): 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. PUBLIC HEALTH RELEVANCE: Project Narrative Dietary calorie intake that exceeds energy expenditure is stored in the adipose tissue as fat. A long-term consequence of excessive caloric intake is obesity, which is a major risk factor for type 2 diabetes, heart attack and other serious complications. According to a recent survey, obesity affects as many as 37% of women and 33% of men among the population served by VA medical facilities. Therefore, amelioration of obesity is important to the health of many veterans. Using a mouse model to explore the regulation of adiposity, we have observed a lean phenotype when a cellular protein called tankyrase is inactivated. Our data indicate that these tankyrase-deficient mice are lean because of heightened energy expenditure. We propose to investigate the molecular mechanisms whereby lack of tankyrase function leads to heightened energy expenditure. Our long-term goal is to establish tankyrase as a pharmacological target in the treatment of obesity.