Dissecting the Nutritional Regulation of Feeding Circuits

项目摘要/摘要 研究策略：肠道和大脑之间的沟通对能量平衡至关重要， 但这种交流是如何在下丘脑馈入回路的动力学中表现出来的，目前尚不清楚。早些时候 对肠道-脑轴的研究依赖于对营养调节影响的间接测量 馈电电路上的外围信号。这些研究导致了一个模型，在该模型中，关键下丘脑的活动 饥饿神经元--AgRP神经元--随着动物营养状态的变化而逐渐波动。与 记录清醒动物中基因定义的神经元群体活动的技术的发展， 最近首次在活体内观察到AgRP神经元的动态变化。这些研究表明， 与流行的模型相反，当动物看到或闻到食物时，AgRP神经元会迅速受到抑制， 在它咬一口之前；然而，食物摄取是维持这种抑制的必要条件。我们有 开发了一种结合体内AgRP神经元动态监测和胃内营养输注的工具 首次表明，在没有通常相关的感觉刺激的情况下，营养物质输送到肠道 通过进食，足以在几分钟的时间尺度上抑制AgRP神经元。这种抑制独立于 食物的常量营养素组成，但取决于摄入的卡路里数量。这样做的目的是 建议确定每种常量营养素抑制的分子和基于电路的机制 AgRP神经元。这将通过三个目标来实现：确定负责的荷尔蒙介质， 确定涉及的营养感受器，并剖析这些信号到达AgRP神经元的途径。 候选人/环境：Lisa Beutler博士是加州大学旧金山分校内分泌科的高级研究员。 她最近在加州大学旧金山分校完成了内科实习，并在华盛顿大学获得了医学博士学位。 在那里她在理查德·帕米特博士的实验室获得了博士学位。她正在完成她的研究员研究，这是 是加州大学旧金山分校扎卡里·奈特博士的实验室中发表在《神经元》杂志上的第一作者论文的主题。 在获得了体内神经记录和先进的啮齿动物手术方面的专业知识后，她现在寻求扩大 她在实验室的专业知识包括光路解剖、单细胞分辨率钙成像和数据 在获得独立的学术内科医生-科学家职位之前，具备分析和编程技能。 职业发展：这个奖项将确保比特勒博士能够作为一名 独立调查员配备了一系列实验工具，既可以定位她在切割时的位置 她的领域的边缘(钙基成像技术，光遗传学)，并使她在该领域的其他人中脱颖而出 (先进的啮齿动物外科技术)。再加上她在内分泌学方面的临床训练，这将使她 独一无二地准备解决需要详细了解神经电路和外周知识的问题 新陈代谢。这一奖项还将促进Beutler博士获得 独立性，包括科学写作、领导力和管理方面的正式培训。

PROJECT SUMMARY/ABSTRACT RESEARCH STRATEGY: Communication between the gut and the brain is essential for energy homeostasis, but how this communication is represented in the dynamics of hypothalamic feeding circuitry is unknown. Early studies of the gut-brain axis relied upon indirect measurements of the effects of nutritionally regulated peripheral signals on feeding circuitry. These studies led to a model in which the activity of key hypothalamic hunger neurons – AgRP neurons – fluctuates gradually as the animal's nutritional state changes. With the development of techniques to record the activity of genetically-defined neuronal populations in awake animals, the dynamics of AgRP neurons were recently observed in vivo for the first time. These studies revealed, contrary to the prevailing model, that AgRP neurons are inhibited rapidly when an animal sees or smells food, before it takes a single bite; however, food ingestion is required for maintenance of this inhibition. We have developed a tool combining in vivo monitoring of AgRP neuron dynamics with intragastric nutrient infusion to show for the first time that nutrient delivery to the gut, in the absence of the sensory stimuli normally associated with eating, is sufficient to inhibit AgRP neurons over a time-scale of minutes. This inhibition is independent of the macronutrient composition of the food but depends upon the number of calories ingested. The goal of this proposal is to determine the molecular and circuit-based mechanisms by which each macronutrient inhibits AgRP neurons. This will be accomplished across three aims: to identify the hormonal mediators responsible, to identify the nutrient sensors involved, and to dissect the pathway by which these signals reach AgRP neurons. CANDIDATE/ENVIRONMENT: Dr. Lisa Beutler is a senior fellow in the Division of Endocrinology at UCSF. She recently completed internal medicine residency at UCSF and an MD/PhD at the University of Washington, where she earned her PhD in Dr. Richard Palmiter's laboratory. She is finishing her fellowship research, which is the subject of a first-author publication in the journal Neuron, in Dr. Zachary Knight's laboratory at UCSF. Having gained expertise in in vivo neural recording and advanced rodent surgery, she now seeks to expand her expertise in the lab to include optical circuit dissection, single-cell resolution calcium imaging, and data analysis and programming skills prior to obtaining an independent position as an academic physician-scientist. CAREER DEVELOPMENT: This award will ensure that Dr. Beutler is able to launch her career as an independent investigator armed with a combination of experimental tools that both position her at the cutting edge of her field (calcium-based imaging techniques, optogenetics) and set her apart from others in the field (advanced rodent surgical techniques). Combined with her clinical training in endocrinology, this will make her uniquely poised to address questions that require detailed knowledge of both neural circuitry and peripheral metabolism. This award will also facilitate Dr. Beutler's acquisition of other professional skills required for independence including formal training in scientific writing, leadership, and management.