Role of the mitochondrial calcium uniporter in brown fat physiology

 描述（由申请人提供）：胰岛素抵抗和2型糖尿病（T2 D）代表了潜在灾难性经济影响的全球健康危机。仅在美国，就有超过一亿人患有肥胖症，这是糖尿病前期和糖尿病综合征的主要危险因素。最近，人们对通过增强棕色脂肪的活性来治疗肥胖、T2 D和相关的代谢紊乱产生了广泛的兴趣，棕色脂肪是一种能够经由解偶联β-氧化燃烧过量脂质储存的组织。然而，目前对棕色脂肪代谢的调控还不完全清楚，也不清楚该组织如何对全身能量稳态发挥其有治疗前景的作用。该提案旨在通过询问线粒体钙单向转运体的作用来促进对基础棕色脂肪生理学的理解，线粒体钙单向转运体是一种最近由申请人的实验室阐明其分子身份的通道。单向转运蛋白将ATP的产生与细胞的能量需求相结合，并可能通过其调节TCA循环通量和回补的能力在燃料转换中发挥关键作用。单向转运蛋白与多种组织中的肾上腺素能信号传导相关，并支持骨骼肌中的峰值生物能量学，骨骼肌是棕色脂肪的密切发育和代谢相关物;此外，棕色脂肪线粒体中的单向转运蛋白电流密度是任何组织中测量的最高电流密度之一。因此，单向转运蛋白是一个很有前途的候选人，以调节棕色脂肪代谢的激素刺激。申请人将追求这样的核心假设，即单向转运蛋白在棕色脂肪生理学中以两个互补但不相互依赖的特定目的发挥核心作用。在目的1中，将在永生化的棕色脂肪细胞中消除单向转运蛋白的成孔亚基（MCU），并分析所得细胞系的生物能量学、代谢、应激信号传导和钙动力学缺陷。令人兴奋的初步数据表明，缺乏MCU的棕色脂肪细胞表现出钝的儿茶酚胺刺激呼吸;这些结果将得到严格的验证和解剖机制。在目标2中，MCU将在小鼠的棕色脂肪中被删除，并且将测定所得动物的改变的能量消耗和棕色脂肪活性、冷耐受性、对饮食诱导的肥胖的增加的易感性和胰岛素抵抗。申请人的实验室已经产生了携带条件MCU等位基因的小鼠，其可以用于以组织特异性方式消除单向转运体活性。通过建立棕色脂肪中单向转运蛋白的作用，这项工作将对该组织的生理学产生基础性的见解，为其临床开发以改善T2 D和肥胖奠定基础。这项工作还将补充拟议的培训计划，使申请人能够发展成为一个成熟，严谨的科学家，能够跨各种主题学科进行交流。

 DESCRIPTION (provided by applicant): Insulin resistance and type 2 diabetes (T2D) represent a global health crisis of potentially disastrous economic impact. In the United States alone, over one hundred million individuals suffer from obesity, the leading risk factor for pre-diabetic and diabetic syndromes. Recently, there has been widespread interest in treating obesity, T2D, and associated metabolic disorders by enhancing the activity of brown fat, a tissue capable of burning excess lipid stores via uncoupled ß-oxidation. At present, however, the regulation of brown fat metabolism is incompletely understood, and it is unclear how this tissue exerts its therapeutically promising effects on systemic energy homeostasis. This proposal aims to advance the understanding of fundamental brown fat physiology by interrogating the role of the mitochondrial calcium uniporter, a channel whose molecular identity was recently elucidated by the applicant's laboratory. The uniporter couples ATP production to cellular energy demand, and may play a key role in fuel switching through its ability to regulate TCA cycle flux and anaplerosis. The uniporter is linked to adrenergic signaling in multiple tissues and supports peak bioenergetics in skeletal muscle, a close developmental and metabolic relative of brown fat; in addition, uniporter current density in brown fat mitochondria i among the highest measured in any tissue. The uniporter is therefore a promising candidate to regulate brown fat metabolism in response to hormonal stimuli. The applicant will pursue the core hypothesis that the uniporter plays a central role in brown fat physiology in two complementary but not codependent specific aims. In Aim 1, the uniporter's pore- forming subunit (MCU) will be ablated in immortalized brown adipocytes, and the resulting cell lines will be analyzed for defects in bioenergetics, metabolism, stress signaling, and calcium dynamics. Exciting preliminary data indicate that brown adipocytes lacking MCU exhibit blunted catecholamine-stimulated respiration; these results will be rigorously validated and dissected mechanistically. In Aim 2, MCU will be deleted in brown fat in mice, and the resulting animals will be assayed for altered energy expenditure and brown fat activity, cold intolerance, increased susceptibility to diet-induced obesity, and insulin resistance. The applicant's laboratory has already generated mice harboring a conditional MCU allele that can be used to ablate uniporter activity in a tissue-specific manner. By establishing a role for the uniporter in brown fat, this wrk will yield foundational insights into the physiology of this tissue, laying the groundwork for its clinical exploitation to ameliorate T2D and obesity. The work will also complement the proposed training plan, enabling the applicant to develop into a mature, rigorous scientist with the abilityto communicate across a variety of topical disciplines.