Exploration of the role of CART/GPR160 in metabolism in the setting of Magel2 deficiency: Implications for Prader Willi Syndrome

项目总结 严重吞噬是Prader Willi综合征(PWS)的特征。多个神经元回路已经被 与PWS相关的吞噬过多有关；然而，食欲神经调节的复杂性 混淆了PWS环境下馈电回路失调的精确机制。这个 神经肽可卡因和苯丙胺调节转录本(CART)是食欲和体重的关键调节因子。 中枢输注CART可减少肥胖大鼠的摄食量和体重增加，并在 小鼠容易肥胖，并增加了对高脂饮食引起的代谢功能障碍的易感性。 同样，CART基因的突变也与人类肥胖有关。有趣的是，下丘脑水平 在PWS的动物模型中，CART多肽的含量降低。尽管有大量证据表明 CART在新陈代谢中的重要作用，在PWS模型中CART减少摄食量的能力尚未得到 据报道。这种知识的缺乏是PWS领域的一大空白。重要的是，我们最近确定了 CART的同源受体作为G蛋白偶联受体，GPR160，从而使化学生物学方法成为可能 设计CART激动剂用于治疗PWS相关的吞噬功能亢进。我们假设中央 在父性遗传性Magel2缺乏症的情况下，注射CART会减少食物的摄入量，而Magel2 缺乏CART将导致中央喂养中心，特别是下丘脑的CART表达减少。我们 将在两个具体目标中解决我们的假设。在目标1中，我们将向Magel2缺陷大鼠注射CART icv，并 食物和水的摄入量以及膳食模式将使用我们的BioDaq系统进行测量。然后老鼠将被放置在 在野外行为测试中，以确保任何观察到的CART对食物摄入量的影响都是由于主要的 手推车对食欲的影响，而不是对运动行为的次要影响。尽管ProCART mRNA 在PWS中，水平可能没有被调节，PWS是负责产生成熟激素的前激素转换酶 研究表明，PSCK1的CART在PWS患者中减少，这导致了PSCK1的减少。 生产成熟的卡特多肽。因此，在目标2中，我们将测量CART、GPR160和PSCK1水平 Magel2缺陷大鼠与WT大鼠的脑、脑脊液和血浆的比较。因为CART的多肽水平会波动 对于代谢状态(即禁食期间减少，重新喂养后恢复正常)，我们将确定是否有功能 利用全球蛋白质组学分析，CART多肽水平的变化发生在Magel2缺乏症的背景下。 最后，我们将确定CART和GPR160在小鼠脑内的表达模式是否发生变化 Magel2缺陷型大鼠与WT大鼠比较。如果我们的假设是正确的，那么用CART激动剂替代 至少应该部分控制PWS患者的食欲。这种以系统为目标的策略 与其他供血回路平行且不依赖于其他供血回路可以彻底改变PWS相关疾病的治疗 吞噬过多，并为PWS患者经历的严重肥胖提供了创新的解决方案。

PROJECT SUMMARY Severe hyperphagia is a hallmark of Prader Willi Syndrome (PWS). Multiple neuronal circuits have been implicated in PWS-associated hyperphagia; however the complexity of the neural regulation of appetite has obfuscated the precise mechanisms underlying the dysregulation of feeding circuits in the setting of PWS. The neuropeptide cocaine and amphetamine regulated transcript (CART) is a key regulator of appetite and weight. Central infusion of CART decreased food intake and weight gain in obese rats, and global deletion of CART in mice led to predisposition to obesity and enhanced susceptibility to high fat diet-induced metabolic dysfunction. Likewise, mutations in the CART gene have been linked to obesity in humans. Interestingly, hypothalamic levels of CART peptide were reduced in an animal model of PWS. In spite of a wealth of evidence indicating an important role of CART in metabolism, the ability of CART to reduce food intake in models of PWS has not been reported. This lack of knowledge represents a major gap in the PWS field. Importantly, we recently identified the cognate receptor of CART as the G protein coupled receptor, GPR160, thus enabling chemical biology methods to design CART agonists for the treatment of PWS-associated hyperphagia. We hypothesize that central injection of CART will reduce food intake in the setting of paternally-inherited Magel2 deficiency, and that Magel2 deficiency will lead to reduced expression of CART in central feeding centers, particularly the hypothalamus. We will address our hypothesis in two Specific Aims. In Aim 1, we will inject CART icv into Magel2-deficient rats, and food and water intakes and meal patterning will be measured using our BioDAQ system. Rats will then be placed in an open field behavioral test to ensure that any observed effect of CART on food intake is due to a primary effect of CART on appetite, rather than a secondary effect on locomotor behavior. Although proCART mRNA levels likely are not modulated in PWS, the prohormone convertase responsible for the production of mature CART, PSCK1, has been shown to be reduced in individuals with PWS, which leads to reductions in the production of mature CART peptide. In Aim 2, we therefore will measure CART, GPR160, and PSCK1 levels in brains, CSF, and plasma of Magel2-deficient rats compared to WT rats. Because CART peptide levels fluctuate with metabolic state (i.e. reduced during fasting, normalized after re-feeding), we will determine if functional changes in CART peptide levels occur in the setting of Magel2 deficiency using global proteomic analyses. Lastly, we will determine if there are changes in the expression patterns of CART and GPR160 in the brains of Magel2-deficient rats compared to WT rats. If our hypotheses are correct, then replacement with CART agonists should at least partially control appetite in individuals with PWS. This strategy of targeting a system that is parallel to, and not dependent upon, other feeding circuits could revolutionize treatment of PWS-associated hyperphagia and offer an innovative solution to the severe obesity experienced by patients with PWS.