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

项目概要/摘要 由脂肪细胞（脂肪细胞）尺寸和数量增加引起的肥胖正在成为世界范围内的一个问题 由于与其他疾病的相关风险，大流行造成了巨大的公共卫生问题。 在哺乳动物中，脂肪/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），其中WAT用于能量存储，BAT用于能量耗散以产生热量。第三种类型 存在脂肪细胞，称为米色脂肪细胞，在 WA T 库中瞬时产生，以响应 环境刺激。 BAT/米色脂肪是已建立的产热组织，在 人体能量稳态，从而保护与肥胖相关的代谢紊乱。虽然白色 脂肪细胞和棕色脂肪细胞由具有不同起源的前体细胞分化而来，Wnt/β-是共识 连环蛋白信号传导通过抑制脂肪形成分化对脂肪形成产生负面影响。虽然 一些研究表明 Wnt 信号传导及其成分在脂肪生成和适当的过程中的需要 脂肪组织的功能，缺乏直接证据，留下了关键的知识空白，就像 Wnt 信号传导一样 在脂肪生成中发挥直接而关键的作用。在我们的初步研究中，我们惊奇地发现了存在 各种脂肪库中 Wnt/β-连环蛋白信号驱动的脂肪细胞群体（称为 Wnt 脂肪细胞） 包括小鼠从胚胎期到成年期的骨髓。使用 SVF 诱导的 Wnt 脂肪细胞 在体外细胞中，我们进一步证明了配体和受体独立的 Wnt/β-catenin 信号传导的需要， 这似乎依赖于脂肪细胞成熟过程中活跃的 Akt/mTOR 信号传导。我们的 scRNA-seq 和 scATAC- seq 分析从分子和功能上将这种新型脂肪细胞群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生热作用 特性，能够响应冷应激而转化/转分化为米色脂肪细胞，并且 涉及全身能量稳态。根据这些初步结果，我们假设一部小说 Wnt/β-连环蛋白信号驱动的脂肪细胞广泛存在于各种脂肪库中，发挥着至关重要的作用 具有调节全身代谢稳态的功能。在该提案中，提出了两个具体目标来测试 该假设严格：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。总的来说，我们将定义 新型 Wnt/β-连环蛋白驱动的脂肪细胞群体在细胞、分子和基因组水平上的身份 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 评估该脂肪细胞群对脂肪组织功能、全身代谢的总体影响 体内平衡和保护肥胖。该提案还将讨论功能机制并确定 脂肪生成过程中 Akt/mTOR 信号依赖的细胞内 Wnt/β-catenin 信号传导的直接靶标 这个脂肪细胞群。从拟议的研究中获得的结果将揭示起源、招募、 独特的产热脂肪细胞群的激活、分子调节和功能，提供了新的 脂肪细胞生物学知识以及该群体未来应用的坚实基础 脂肪细胞在肥胖治疗中的应用。

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.