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

探索 Magel2 缺陷情况下 CART/GPR160 在代谢中的作用：对普瑞德威利综合征的影响

基本信息

批准号：
10642678
负责人：
Gina L.C. Yosten
金额：
$ 18.94万
依托单位：
SAINT LOUIS UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-06-10 至 2024-05-31
项目状态：
已结题

项目摘要

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.

项目概要严重的食欲过盛是普瑞德·威利综合症 (PWS) 的一个标志。多个神经元回路与 PWS 相关的食欲过盛有关；然而，食欲神经调节的复杂性混淆了 PWS 情况下喂养回路失调的精确机制。这神经肽可卡因和安非他明调节转录本（CART）是食欲和体重的关键调节剂。 CART 的中央输注减少了肥胖大鼠的食物摄入量和体重增加，并且 CART 的整体删除小鼠会导致肥胖倾向，并增加对高脂肪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 PWS 动物模型中 CART 肽的含量减少。尽管有大量证据表明 CART 在新陈代谢中的重要作用，但 CART 减少 PWS 模型食物摄入的能力尚未得到证实报道称。这种知识的缺乏代表了 PWS 领域的一个主要差距。重要的是，我们最近确定了 CART 的同源受体为 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 激动剂来治疗 PWS 相关的食欲过盛。我们假设中央在父系遗传的 Magel2 缺陷的情况下，注射 CART 会减少食物摄入量，并且 Magel2 缺乏将导致中央喂养中心，特别是下丘脑中 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 CART icv 注射到 Magel2 缺陷大鼠中，并且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。然后将老鼠放置在在旷场行为测试中，以确保观察到的 CART 对食物摄入的任何影响都是由于主要因素 CART 对食欲的影响，而不是对运动行为的二次影响。虽然 proCART mRNA PWS 中的水平可能不受调节，PWS 是负责产生成熟激素的激素原转化酶。 CART、PSCK1 已被证明在 PWS 患者中减少，从而导致生产成熟的CART肽。因此，在目标 2 中，我们将测量 CART、GPR160 和 PSCK1 水平 Magel2 缺陷大鼠的大脑、脑脊液和血浆与 WT 大鼠相比。因为 CART 肽水平波动根据代谢状态（即禁食期间减少，重新进食后恢复正常），我们将确定功能是否正常使用整体蛋白质组学分析发现 Magel2 缺陷时 CART 肽水平发生变化。最后，我们将确定 CART 和 GPR160 在大脑中的表达模式是否发生变化。 Magel2 缺陷大鼠与 WT 大鼠的比较。如果我们的假设正确，则替换为 CART 激动剂应该至少部分控制 PWS 患者的食欲。这种针对系统的策略是与其他喂养回路平行但不依赖于其他喂养回路可能会彻底改变 PWS 相关的治疗食欲亢进，并为 PWS 患者的严重肥胖症提供创新的解决方案。