Characterization and functional assessment of a novel population of Wnt/beta-catenin driven adopocytes.

项目摘要/摘要 肥胖是由脂肪细胞(脂肪细胞)的大小和数量增加引起的，正成为世界性的 大流行，由于与发展其他疾病相关的风险，造成巨大的公共卫生问题。 在哺乳动物中，脂肪组织由经典的白色脂肪组织(WAT)和棕色脂肪组织组成 (BAT)，WAT用于储能，BAT用于能量耗散产生热量。第三种类型的 脂肪细胞是存在的，称为米色脂肪细胞，它们是在华盛顿特区的仓库中短暂产生的 环境刺激。蝙蝠/米色脂肪是公认的产热组织，在 人体能量动态平衡，从而保护肥胖相关的代谢紊乱。虽然是白色的 脂肪细胞和棕色脂肪细胞不同于起源不同的前体细胞，Wnt/β- 连环蛋白信号通过抑制成脂分化而对成脂产生负面影响。虽然 一些研究已经暗示了Wnt信号及其成分在脂肪形成和正常发育中的需要 关于脂肪组织的功能，缺乏直接证据，留下了一个关键的知识缺口，就像Wnt信号发挥作用一样 在脂肪生成中起着直接而关键的作用。在我们的初步研究中，我们意外地发现了 在不同的脂肪库中，WNT/β-连环蛋白信号驱动的脂肪细胞群体被称为WNT+脂肪细胞 包括小鼠从胚胎阶段到成年的骨髓。利用SVF诱导的Wnt+脂肪细胞 在体外培养的细胞中，我们进一步证明了Wnt/β-catenin信号转导途径对配体和受体非依赖性的需求。 这似乎依赖于活跃的Akt/mTOR信号，在脂肪细胞成熟过程中。我们的scRNA-seq和scatac- SEQ分析在分子和分子水平上将这种新的脂肪细胞群体与经典的脂肪细胞区分开来 基因组水平。我们还发现，这些脂肪细胞表现出潜在的高代谢和产热能力。 特性，能够转化/转分化为米色脂肪细胞以响应冷应激，以及 牵涉到全身能量动态平衡。基于这些初步结果，我们假设一部小说 Wnt/β-Catenin信号驱动的脂肪细胞群广泛存在于各种脂肪库中，并发挥着至关重要的作用 调节全身代谢动态平衡功能。在这项提案中，提出了两个具体的目标来测试 这一假设严格：1)鉴定内源性Wnt+脂肪细胞，并研究其功能 细胞内Wnt/β-连环蛋白信号转导在脂肪形成中的作用机制2)体内功能的测定 WNT+脂肪细胞对胎儿/新生儿和成人期全身代谢的调节作用总体而言，我们将定义 Wnt/β-Catenin驱动的新脂肪细胞群体在细胞、分子和基因组水平的同源性 存在于各种脂肪储存库中，并显示出潜在的高代谢和产热特性。我们还将 评估这组脂肪细胞对脂肪组织功能、全身代谢的整体影响 动态平衡和肥胖保护。该提案还将涉及运作机制，并确定 AKT/MTOR信号依赖的细胞内Wnt/β-catenin信号在成脂过程中的直接靶点 这群脂肪细胞。从拟议的研究中获得的结果将揭示来源，招募， 一组独特的生热脂肪细胞的激活、分子调控和功能，提供了新的 对脂肪细胞生物学的认识，以及为未来这一群体的应用奠定坚实的基础 脂肪细胞在肥胖治疗中的作用。

Project Summary/Abstract Obesity, caused by the increase in size and the amount of fat cells (adipocytes), is becoming a worldwide pandemic, producing a huge public health problem due to the associated risk with developing other diseases. In mammals, the adipose/fat tissue is composed of classic white adipose tissue (WAT) and brown adipose tissue (BAT), with WAT serving for energy storage and BAT for energy dissipation to produce heat. A third type of adipocytes exists, known as beige adipocytes that are transiently generated in WA T depots in response to environmental stimulations. BAT/beige fats are the established thermogenic tissues that play an essential role in human energy homeostasis and therefore in protection of obesity-related metabolic disorders. While white adipocytes and brown adipocytes differentiate from precursors with distinct origins, it is the consensus that Wnt/β- catenin signaling imposes negative effects on adipogenesis by inhibiting adipogenic differentiation. Although some studies have implicated the requirement of Wnt signaling and its components in adipogenesis and proper functions of adipose tissues, direct evidence is lacking, leaving a critical knowledge gap as if Wnt signaling plays a direct and crucial role in adipogenesis. In our preliminary studies, we have surprisingly discovered the existence of a population of Wnt/β-catenin signaling driven adipocytes, named as Wnt+ adipocytes, in various fat depots including bone marrow in mice from embryonic stage to adulthood. Using Wnt+ adipocytes induced from SVF cells in vitro, we further showed the requirement of the ligand- and receptor-independent Wnt/β-catenin signaling, which appeared to depend on active Akt/mTOR signaling, in adipocyte maturation. Our scRNA-seq and scATAC- seq analyses have distinguished this novel population of adipocytes from the classic adipocytes at molecular and genomic levels. We also found that these adipocytes exhibit potentially high metabolic and thermogenic properties, being able to convert/transdifferentiate into beige adipocytes in response to cold stress, and being implicated in systemic energy homeostasis. Based on these preliminary results, we hypothesize that a novel population of Wnt/β-catenin signaling driven adipocytes is widely present in various fat depots and plays crucial function in regulating whole body metabolic homeostasis. In this proposal, two specific aims are proposed to test this hypothesis rigorously: 1) to characterize endogenous Wnt+ adipocytes and to investigate the functional mechanism of the intracellular Wnt/β-catenin signaling in adipogenesis; 2) To determine the in vivo function of Wnt+ adipocytes in regulating whole-body metabolism in fetal/neonatal and adult stage. Overall, we will define the identity at cellular, molecular, and genomic levels of a novel population of Wnt/β-catenin driven adipocytes that exist in various fat depots and exhibit potentially high metabolic and thermogenic properties. We will also assess overall impacts of this population of adipocytes on adipose tissue function, whole-body metabolic homeostasis, and protection of obesity. The proposal will also address the functional mechanism and identify direct targets of the Akt/mTOR signaling dependent intracellular Wnt/β-catenin signaling during adipogenesis in this population of adipocytes. Results obtained from proposed studies will reveal the origin, recruitment, activation, molecular regulation, and function of a unique population of thermogenic adipocytes, providing novel knowledge to the biology of adipocytes as well as solid foundation for future application of this population of adipocytes in the therapy of obesity.