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

项目总结/摘要 肥胖症，由脂肪细胞（脂肪细胞）的大小和数量的增加引起，正在成为一个世界性的问题。 大流行，由于与发展其他疾病相关的风险，产生了巨大的公共卫生问题。 在哺乳动物中，脂肪/脂肪组织由典型的白色脂肪组织（WAT）和棕色脂肪组织组成 (BAT)WAT用于能量存储，BAT用于能量耗散以产生热量。第三类型的 脂肪细胞存在，称为米色脂肪细胞，其在WAT贮库中响应于 环境刺激。BAT/米色脂肪是已确立的产热组织，在以下方面发挥重要作用： 人体能量平衡，因此保护肥胖相关的代谢紊乱。虽然白色 脂肪细胞和棕色脂肪细胞从不同来源的前体细胞分化，Wnt/β- 连环蛋白信号传导通过抑制脂肪形成分化而对脂肪形成产生负面影响。虽然 一些研究已经暗示了Wnt信号及其组分在脂肪形成中的需要， 脂肪组织的功能，缺乏直接的证据，留下了一个关键的知识空白，如果Wnt信号发挥作用， 在脂肪形成中起着直接而关键的作用。在我们的初步研究中，我们惊奇地发现 Wnt/β-catenin信号驱动的脂肪细胞群，称为Wnt+脂肪细胞，在各种脂肪库中， 包括小鼠从胚胎期到成年期的骨髓。使用由SVF诱导的Wnt+脂肪细胞 细胞在体外，我们进一步显示了配体和受体非依赖性Wnt/β-连环蛋白信号传导的需要， 其似乎依赖于脂肪细胞成熟中的活性Akt/mTOR信号传导。我们的scRNA-seq和scATAC- seq分析已经在分子水平上将这种新型脂肪细胞群体与经典脂肪细胞区分开来， 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， 特性，能够响应于冷应激而转化/转分化为米色脂肪细胞，并且 与系统能量平衡有关基于这些初步结果，我们假设一种新的 Wnt/β-catenin信号驱动的脂肪细胞群广泛存在于各种脂肪库中， 调节全身代谢平衡的功能。在这个建议中，提出了两个具体的目标，以测试 这一假设严格：1）表征内源性Wnt+脂肪细胞，并研究其功能， 细胞内Wnt/β-catenin信号传导在脂肪形成中的机制; 2）确定Wnt/β-catenin信号传导在脂肪形成中的体内功能。 Wnt+脂肪细胞在胎儿/新生儿和成人阶段调节全身代谢中的作用。总的来说，我们将定义 Wnt/β-catenin驱动的脂肪细胞新群体在细胞、分子和基因组水平上的身份 其存在于各种脂肪库中并表现出潜在的高代谢和产热特性。我们还将 评估该脂肪细胞群体对脂肪组织功能、全身代谢、 体内平衡和肥胖的保护。该提案还将涉及职能机制， 脂肪形成过程中Akt/mTOR信号传导依赖的细胞内Wnt/β-catenin信号传导的直接靶点 这群脂肪细胞从拟议的研究中获得的结果将揭示起源，招募， 激活，分子调控和功能的独特群体的产热脂肪细胞，提供了新的 脂肪细胞的生物学知识，以及这一群体的未来应用的坚实基础， 脂肪细胞在肥胖症治疗中的应用。

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.