Understanding the role of vagal FFAR3 in regulating glucose homeostasis

项目概要/摘要 本F31应用的目标是阐明迷走神经中FFAR 3信号传导在调节细胞凋亡中的作用和机制。 葡萄糖稳态能量代谢的适当调节需要对营养和激素线索的感知来协调 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 已经证明激素调节食物摄取、葡萄糖体内平衡和肠道运动。肠道微生物组 发酵可溶性非消化性纤维，释放短链脂肪酸（SCFA），可作为信号分子 通过G蛋白偶联受体SCFA包括乙酸盐、丙酸盐和丁酸盐，可结合游离脂肪酸 受体2（FFAR 2）和3（FFAR 3）。增加膳食纤维摄入量或直接补充SCFA已被证明 改善宿主葡萄糖稳态，但介导这些作用的分子机制尚不清楚。直接迷走神经感觉 通过FFAR 3产生SCFA的肠道微生物组的增加可以有助于调节葡萄糖代谢。我们发现 与正常食物（NC）喂养的对照相比，在西方饮食（WD）喂养的小鼠的血浆中丙酸盐减少。当 肥胖小鼠接受来自瘦NC喂养供体的粪便微生物组移植物（FMT）的口服管饲，它们的血浆 丙酸水平增加，空腹血糖降低。直接在WD-1000水溶液中补充丙酸盐， 喂食的小鼠降低了空腹血糖并改善了葡萄糖耐量。丙酸盐是已知最有效的内源性配体 对于FFAR 3，FFAR 3 KO小鼠表现出破坏的葡萄糖耐量，因此我们假设FFAR 3表达在 迷走神经连接微生物群系产生的丙酸和葡萄糖稳态的中枢神经系统控制。的确， 我们发现Ffar 3在迷走神经感觉神经元中被主动翻译。用FFAR 3配体处理迷走神经培养物， 丙酸，激活神经元，增加神经元翻译的Glp 1 r。迷走神经GLP 1 R的功能和表达 在啮齿类动物肥胖模型中，这种基因表达失调，但分子机制还不清楚。我们假设 丙酸通过迷走神经中的FFAR 3信号来增加Glp 1 r表达并改善葡萄糖稳态。我们 我们将通过以下目标来检验这一假设。目的1将评估丙酸盐是否激活迷走神经元并增加 迷走神经器官型培养物中通过FFAR 3的Glp 1 r翻译。我们将通过利用核糖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细胞特异性评估。我们将评估糖调节基因的翻译 在表达FFAR 3的迷走神经节和来自FFAR 3 KO小鼠的神经节中丙酸盐刺激后。目标2将评估 在WD喂养的雄性和雌性小鼠中，丙酸盐是否需要迷走FFAR 3来改善体内葡萄糖耐受不良。 为了实现这一点，我们将利用一种新的FFAR 3 floxed小鼠模型，并仅从迷走神经基因组中去除FFAR 3。 神经元我们将用西方饮食攻击对照和迷走FFAR 3 KO小鼠，所述西方饮食补充有盐水或生理盐水。 丙酸盐，以确定丙酸盐是否通过FFAR 3改善WD诱导的葡萄糖耐受不良。总的来说，我们希望这项研究 提高对丙酸盐和FFAR 3如何有助于葡萄糖稳态的自主控制的理解， 能量平衡这项研究将阐明治疗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.