Understanding the role of vagal FFAR3 in regulating glucose homeostasis

项目摘要/ABSRACT F31应用的目的是阐明FFAR3信号在迷走神经调节中的作用和机制 葡萄糖动态平衡。能量代谢的适当调节需要感觉到营养和激素信号的协调 适当的行为和生理反应。迷走神经对膳食营养素或营养素刺激的感觉 荷尔蒙已被证明可以调节食物摄入量、葡萄糖稳态和肠道运动。肠道微生物群 发酵可溶的不可消化纤维释放可作为信号分子的短链脂肪酸(SCFA) 通过G蛋白偶联受体。SCFA，包括醋酸盐、丙酸和丁酸盐，可以结合游离脂肪酸 受体2(FFAR2)和受体3(FFAR3)。增加膳食纤维摄入量或直接补充SCFA已被证明是 改善宿主葡萄糖动态平衡，但调节这些作用的分子机制尚不清楚。直接迷走神经感觉 通过FFAR3产生的肠道微生物群中的SCFA‘s可能有助于调节糖代谢。我们发现 与正常饮食(NC)喂养的对照组相比，西方饮食(WD)喂养的小鼠血浆中丙酸含量降低。什么时候 肥胖小鼠接受了来自瘦肉NC喂养者的粪便微生物组移植(FMT)的口服，它们的血浆 丙酸水平升高，空腹血糖下降。在WD的水中直接添加丙酸- 喂食小鼠可降低空腹血糖，改善糖耐量。丙酸是已知的最有效的内源性配体 对于FFAR3，和FFAR3 KO小鼠表现出糖耐量紊乱，所以我们假设FFAR3在 迷走神经连接微生物组产生的丙酸和中枢神经系统控制葡萄糖的稳态。的确， 我们发现Ffar3在迷走神经感觉神经元中被主动翻译。用FFAR3配体处理迷走神经培养物， 丙酸可激活神经元，增加GLP1R的神经元翻译。迷走神经GLP1R的功能和表达 在肥胖的啮齿动物模型中存在调控失调，但其分子机制尚不清楚。我们假设 丙酸信号通过迷走神经中的FFAR3增加GLP1R的表达，改善血糖稳态。我们 我将通过以下目标来检验这一假设。目标1将评估丙酸是否激活迷走神经细胞并增加 迷走神经器官培养中GLP1R通过FFAR3的翻译。我们将通过利用核标签遗传小鼠来实现这一点 该模型允许对翻译中的基因进行特定于细胞的评估。我们将评估糖调节基因的翻译 丙酸刺激迷走神经节和FFAR3KO小鼠迷走神经节表达FFAR3。目标2将评估 丙酸是否需要迷走神经FFAR3来改善喂食WD的雄性和雌性小鼠体内的葡萄糖耐量。 为了做到这一点，我们将利用一种新的FFAR3小鼠模型，并从基因上仅从迷走神经中去除FFAR3 神经元。我们将挑战对照组和迷走神经FFAR3KO小鼠，用西式饮食补充生理盐水或 丙酸，以确定丙酸盐是否通过FFAR3改善WD诱导的葡萄糖耐量。总体而言，我们预计这项研究 为了提高对丙酸和FFAR3如何有助于自主控制血糖动态平衡和 能量平衡。这项拟议的研究将阐明治疗2型糖尿病的新信号通路。

PROJECT SUMMARY/ABSRACT The goal of this F31 application is to elucidate the roles and mechanisms of FFAR3 signaling in the vagus nerve in regulating glucose homeostasis. Proper regulation of energy metabolism requires sensing of nutrient and hormonal cues to coordinate an appropriate behavioral and physiological response. Vagus nerve sensing of dietary nutrients or nutrient-stimulated hormones has been demonstrated to regulate food intake, glucose homeostasis, and gut motility. The gut microbiome ferments soluble non-digestible fiber to release short-chain fatty acids (SCFA’s) which can serve as signaling molecules through G-protein coupled receptors. The SCFA’s, including acetate, propionate, and butyrate can bind free fatty acid receptor 2 (FFAR2) and 3 (FFAR3). Increasing dietary fiber intake or directly supplementing SCFA’s has been shown to improve host glucose homeostasis, but the molecular mechanisms mediating these effects are unclear. Direct vagal sensing of gut microbiome produced SCFA’s via FFAR3 could contribute to regulation of glucose metabolism. We found that propionate was decreased in the plasma of western diet (WD)-fed mice compared to normal chow (NC)-fed controls. When obese mice received oral gavages of fecal microbiome transplantations (FMT) from lean NC-fed donors, their plasma propionate levels increased, and fasting blood glucose decreased. Directly supplementing propionate in the water of WD- fed mice lowered fasting glucose and improved glucose tolerance. Propionate is the most potent known endogenous ligand for FFAR3, and FFAR3 KO mice exhibit disrupted glucose tolerance, so we hypothesized that FFAR3 expressed on the vagus nerve connects microbiome-produced propionate and central nervous system control of glucose homeostasis. Indeed, we found Ffar3 to be actively translated in vagal sensory neurons. Treatment of vagal cultures with the FFAR3 ligand, propionate, activated the neurons and increased neuronal translation of Glp1r. Vagal GLP1R function and expression is dysregulated in rodent models of obesity, but the molecular mechanisms are not well understood. We hypothesize that propionate signals through FFAR3 in the vagus nerve to increase Glp1r expression and improve glucose homeostasis. We will test this hypothesis through the following aims. Aim 1 will assess if propionate activates vagal neurons and increases Glp1r translation via FFAR3 in vagal organotypic cultures. We will accomplish this by utilizing the ribotag genetic mouse model which allows for cell-specific assessment of genes in translation. We will assess translation of glucoregulatory genes after propionate stimulation in vagal ganglia expressing FFAR3, and ganglia from FFAR3KO mice. Aim 2 will assess whether vagal FFAR3 is required for propionate to improve glucose intolerance in vivo in WD-fed male and female mice. To accomplish this, we will utilize a novel FFAR3 floxed mouse model and genetically ablate FFAR3 only from vagal neurons. We will challenge control and vagal FFAR3KO mice with a western diet, supplemented with either saline or propionate, to determine if propionate improves WD-induced glucose intolerance via FFAR3. Overall, we expect this study to improve the understanding of how propionate and FFAR3 contribute to autonomic control of glucose homeostasis and energy balance. The proposed study will elucidate new signaling pathways for the treatment of type 2 diabetes.