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

项目总结/摘要 肥胖症是一种全球性流行病，发病率、死亡率和医疗支出呈加速趋势。 治疗的有效性有限，或存在安全性问题。瘦素是一种有效的促胰岛素分泌因子， 激素和治疗饮食诱导肥胖症（DIO）令人信服候选药物。然而，DIO诱导瘦素抵抗， 部分通过下调下丘脑神经元表面的瘦素受体（LepRs）， 治疗无效。克服瘦素抵抗已经成为肥胖治疗的一个有希望的目标。最近， 我们发现鸟苷酸环化酶C（GUCY 2C）受体特异性表达于下丘脑LepR（+） 神经元像LepR一样，下丘脑GUCY 2C通过结合其激素尿鸟苷素诱导饱腹感， 在肠道中产生。在DIO中，尿鸟苷素表达丢失，使下丘脑GUCY 2C沉默。重要的是， GUCY 2C信号传导的重建恢复了DIO小鼠中的瘦素敏感性并产生体重减轻。这些数据 表明肥胖症中肠道尿鸟苷素缺失通过沉默GUCY 2C信号传导产生瘦素抗性 在下丘脑，降低细胞表面LepR。这个项目的最终长期目标是阐明 下丘脑中GUCY 2C信号传导调节饱腹感和抵抗体重增加的机制， GUCY 2C配体疗法在治疗和预防肥胖症中的效用。为了实现这一目标，三 提出了具体目标。目的1，病理生理学目的，将证明尿鸟苷酸-GUCY 2C 轴调节瘦素敏感性。利用独特的组织特异性条件小鼠模型， 我们实验室，我们将测量小鼠在消除尿鸟苷酸-GUCY 2C前后的瘦素敏感性 信号轴将通过表型分析评估具有改变的GUCY 2C信号传导的小鼠中的瘦素敏感性。 饱腹感和代谢的分析，以及LepR信号传导的生化分析。目标2，机械目标，将 确定GUCY 2C信号传导控制神经元表面LepRs的可用性。初步数据 表明在GUCY 2C-/-小鼠中LepR信号传导减少。我们将使用从LepR富集的LepR（+）神经元 报告基因小鼠中的细胞，以定量GUCY 2C信号传导对LepR易位至细胞表面和信号传导的影响。 最后，目标3，治疗目标，将定义GUCY 2C配体克服瘦素抵抗的能力 在DIO小鼠中。在这里，我们将使用临床上可用的GUCY 2C配体，以及具有条件性尿鸟苷肽的小鼠。 转基因，以重建DIO小鼠中的下丘脑GUCY 2C信号传导。使用目标1中描述的方法，我们 将探索外源性或转基因GUCY 2C配体补充对下丘脑瘦素的影响 DIO动物的信号。这些研究将揭示导致肥胖的新机制和新的解决方案 以克服典型的瘦素抵抗并减轻肥胖症中食欲和饱腹感的失调。的 通过批准GUCY 2C配体治疗慢性炎症， 便秘综合征，提供了令人兴奋的机会，使用这些配体治疗肥胖。

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.