Silencing the uroguanylin-GUCY2C gut-brain axis mediates leptin resistance in obesity

项目摘要/摘要 肥胖症是一种全球性流行病，发病率、死亡率和医疗费用呈加速上升趋势。 治疗方法要么疗效有限，要么存在安全问题。瘦素是一种有效的厌食症 荷尔蒙和治疗饮食诱导肥胖症(DIO)的有力候选者。然而，DIO诱导瘦素抵抗， 在一定程度上，通过下调下丘脑神经元表面的瘦素受体(LepRs)，使瘦素 治疗无效。克服瘦素抵抗已成为肥胖症治疗的一个有希望的目标。最近， 我们发现鸟苷酸环化酶C(GUCY2C)受体在下丘脑Lepr(+)中特异表达。 神经元。与Lepr一样，下丘脑GUCY2C通过结合其激素尿鸟苷来诱导饱足感， 在肠道中产生的。在DIO中，尿鸟苷失去表达，使下丘脑GUCY2C沉默。重要的是 GUCY2C信号的重建恢复了DIO小鼠对瘦素的敏感性，并产生了体重减轻。这些数据 提示肥胖时肠道尿鸟苷缺失可通过沉默GUCY2C信号产生瘦素抵抗 在下丘脑，细胞表面Lepr减少。这个项目的最终长期目标是阐明 下丘脑GUCY2C信号调节饱腹感和抵抗体重增加的机制，以告知 GUCY2C配体疗法在肥胖治疗和预防中的应用为了实现这一目标，三个 提出了具体的目标。目的1，病理生理目的，将证明尿鸟苷-GUCY2C AXIS调节瘦素的敏感性。利用由开发的独特的组织特定条件小鼠模型 我们的实验室，我们将测定消除尿鸟苷-GUCY2C前后小鼠的瘦素敏感性 信号轴。GUCY2C信号改变小鼠的瘦素敏感性将通过表型进行评估 饱腹感和代谢的分析，以及LEPR信号的生化分析。目标2，机械目标，意志 确定GUCY2C信号控制神经元表面LepRs的可用性。初步数据 提示在GUCY2C-/-小鼠中Lepr信号转导减少。我们将使用由Lepr丰富的Lepr(+)神经元 报告小鼠量化GUCY2C信号对Lepr转位到细胞表面和信号的影响。 最后，目标3，治疗目标，将定义GUCY2C配体克服瘦素抵抗的能力 在DIO小鼠体内。在这里，我们将使用临床上可用的GUCY2C配体，以及条件尿鸟苷小鼠 转基因，以重建DIO小鼠下丘脑GUCY2C信号。使用目标1中描述的方法，我们 将探讨外源性或转基因GUCY2C配体补充对下丘脑瘦素的影响 DIO动物体内的信号。这些研究将揭示导致肥胖的新机制和新的解决方案 克服典型的瘦素抵抗，缓解肥胖患者的食欲和饱腹感失调。这个 GUCY2C配体被批准用于治疗慢性疾病，突显了将这些结果转化为患者的可能性 便秘综合征，提供了使用这些配体治疗肥胖症的令人兴奋的机会。

PROJECT SUMMARY/ABSTRACT Obesity is a global pandemic with accelerating trends in morbidity, mortality, and medical expenditures. Treatments have been limited in efficacy or burdened with safety concerns. Leptin is a potent anorexigenic hormone and compelling candidate to treat diet-induced obesity (DIO). However, DIO induces leptin resistance, in part, by downregulating leptin receptors (LepRs) on the surface of hypothalamic neurons, rendering leptin therapy ineffective. Overcoming leptin resistance has emerged as a promising goal for obesity therapy. Recently, we discovered that the guanylyl cyclase C (GUCY2C) receptor is specifically expressed in hypothalamic LepR(+) neurons. Like LepR, hypothalamic GUCY2C induces satiety through binding of its hormone, uroguanylin, produced in intestine. In DIO, uroguanylin expression is lost, silencing hypothalamic GUCY2C. Importantly, reconstitution of GUCY2C signaling restores leptin sensitivity and produces weight loss in DIO mice. These data suggest that loss of intestinal uroguanylin in obesity produces leptin resistance by silencing GUCY2C signaling in hypothalamus, decreasing cell-surface LepR. The ultimate long-term goal of this project is to elucidate mechanisms by which GUCY2C signaling in hypothalamus regulates satiety and resists weight gain, to inform the utility of GUCY2C ligand therapy in the treatment and prevention of obesity. To achieve this goal, three specific aims are proposed. Aim 1, the pathophysiologic aim, will demonstrate that the uroguanylin-GUCY2C axis regulates leptin sensitivity. Leveraging unique tissue-specific conditional mouse models developed by our laboratory, we will measure leptin sensitivity of mice before and after eliminating the uroguanylin-GUCY2C signaling axis. Leptin sensitivity in mice with altered GUCY2C signaling will be assessed through phenotypic analysis of satiety and metabolism, and biochemical analysis of LepR signaling. Aim 2, the mechanistic aim, will establish that GUCY2C signaling controls the availability of neuronal surface LepRs. Preliminary data suggest that LepR signaling is reduced in GUCY2C-/- mice. We will use LepR(+) neurons enriched from LepR reporter mice to quantify the effect of GUCY2C signaling on LepR translocation to the cell surface and signaling. Finally, Aim 3, the therapeutic aim, will define the ability of GUCY2C ligands to overcome leptin resistance in DIO mice. Here, we will use clinically available GUCY2C ligands, and mice with a conditional uroguanylin transgene, to reconstitute hypothalamic GUCY2C signaling in DIO mice. Using methods described in Aim 1, we will explore the effects of exogenous or transgenic GUCY2C ligand supplementation on hypothalamic leptin signaling in DIO animals. These studies will reveal new mechanisms contributing to obesity, and novel solutions to overcome canonical leptin resistance and alleviate dysregulation of appetite and satiety in obesity. The potential to translate these results into patients is underscored by approval of GUCY2C ligands to treat chronic constipation syndromes, offering the exciting opportunity of using these ligands to treat obesity.