Adipose stem cells' niche in obesity

肥胖症作为一个重大的公共卫生问题和主要的可预防的原因， 死亡来自COVID-19大流行的斯塔克数据显示，肥胖是严重程度的独立风险因素，33% 死亡率肥胖本身并不致命，但却是导致严重疾病的主要健康风险因素， 心血管疾病、2型糖尿病和某些癌症。美国42%的成年人肥胖 (CDC NCHS报告2020）。与肥胖相关的医疗保健费用占美国总费用的10%以上 医疗支出，并已上升到每年2540亿美元（1）。令人震惊的是，78%的退伍军人是 肥胖，与平民人口相比，比例明显较高（2）。 脂肪组织是能量平衡和代谢的重要内分泌调节器。期间 在脂肪形成中，脂肪干细胞（ASC）分化成脂肪细胞并补充身体对脂肪的需要。 新的脂肪细胞正常肥胖在肥胖中被夸大，并伴有脂肪细胞增生 和肥大。此前，该实验室证明，肥胖改变了人类脂肪干细胞的生态位 从而促进有利于发展肥胖相关合并症的微环境。一 一个重要的发现是长链非编码RNA（lncRNA）的表达在肥胖ASC中不同， 与导致异常代谢过程、胰岛素抵抗和 在肥胖症中观察到的慢性低度炎症。使用无偏的转录组学筛选，该实验室 将lncRNAGAS5鉴定为在人类肥胖脂肪组织中耗尽的重要调节基因， ASC和成熟脂肪细胞相比，瘦。先前的研究表明，GAS 5调节胰岛素 受体和糖皮质激素受体介导的途径。然而，低GAS的重要性和影响5 水平对肥胖脂肪细胞中代谢途径的影响尚未得到彻底研究。因此， 假设低水平的GAS 5实质上有助于合并症的表现 与肥胖有关。为了确定GAS 5是否支持健康的脂肪细胞， 该提案将评估GAS5在人类肥胖ASC和脂肪细胞中的潜在机制和作用 使用多学科方法，包括临床前，生理，细胞和生化实验。 具体目的1：确定GAS 5在ASC和脂肪细胞中的作用：假设操纵GAS 5表达， GAS5水平将影响ASC和脂肪细胞的代谢健康。GAS5 siRNA或过表达质粒 将用于评估与脂肪细胞健康和功能相关的遗传和代谢参数。 具体目标2：阐明GAS 5在肥胖脂肪细胞中调节的分子机制： 在肥胖症中ASC和脂肪组织含量低。最近开发了一种稳定GAS 5的小分子。 假设稳定GAS5水平可以缓解代谢应激，该项目将利用这一点 化合物作为分子工具，以确定功能读数的潜在分子机制。 具体目的3：研究GAS 5在肥胖小鼠模型中体内稳定化的影响： 数据显示，靶向GAS 5的小分子增加IR水平，恢复胰岛素信号传导， 调节GR靶基因。这一目标将系统地阐明稳定GAS 5的生理效应 在饮食诱导的肥胖小鼠模型中使用新的治疗剂。 总的来说，该项目填补了知识的重大空白，以了解lncRNA在肿瘤中的作用。 影响人类肥胖症中脂肪组织的代谢过程。鉴定GAS 5为可药用的 代谢疾病中的RNA靶点已经成功开发出一种小分子治疗剂， GAS5（基因组医学的前沿）具有促进ASC代谢健康的高潜力， 肥胖症的脂肪细胞该项目将对预防或治疗代谢功能障碍产生相当大的影响 与肥胖相关的疾病，从而阻碍了肥胖作为最可预防的死亡原因的上升。

Obesity continues to escalate as a significant public health problem and as the leading preventable cause of death. Stark data from COVID19 pandemic shows obesity is an independent risk factor of severity with 33% mortality rate. Obesity per se is not fatal but is the major health risk factor promoting severe diseases including cardiovascular diseases, type 2 diabetes mellitus, and certain cancers. 42% of adult population in US is obese (CDC NCHS report 2020). Healthcare costs related to obesity account for greater than 10% of total US medical expenditures and has risen to $254 billion per year (1). Alarmingly 78% of the Veteran population is obese, a notably higher percent compared to civilian population(2). Adipose tissue is an important endocrine regulator of energy homeostasis and metabolism. During adipogenesis, the adipose stem cells (ASC) differentiate into adipocytes and replenish the body’s need for new adipocytes. Normal adiposity is exaggerated in obesity and is accompanied by adipocyte hyperplasia and hypertrophy. Previously this lab demonstrated that obesity changes the human adipose stem cells’ niche such that it promotes a microenvironment conducive to developing obesity-associated comorbidities. A significant finding was that the expression of long noncoding RNAs (lncRNAs) differed in the obese ASC compared to lean subjects which contributed to the aberrant metabolic processes, insulin resistance and chronic low-grade inflammation observed in obesity. Using an unbiased transcriptomic screening, this lab identified lncRNA GAS5 as an important regulatory gene that is depleted in human obese adipose tissue, ASC and mature adipocytes compared to lean. Prior research has demonstrated that GAS5 regulates insulin receptor and glucocorticoid receptor mediated pathways. However, the importance and impact of low GAS5 levels on the metabolic pathways in obese adipocytes has not yet been thoroughly investigated. Hence, it is hypothesized that low levels of GAS5 substantially contributes to the manifestation of comorbidities associated with obesity. Towards the overarching goal to determine if GAS5 supports healthy adipocytes, the proposal will evaluate the underlying mechanisms and role of GAS5 in human obese ASC and adipocytes using a multi-disciplinary approach including pre-clinical, physiological, cellular and biochemical experiments. Specific Aim 1: Determine the role of GAS5 in ASC and adipocytes: It is hypothesized that manipulating GAS5 levels will affect the metabolic health of ASC and adipocytes. GAS5 siRNA or over-expression plasmid will be used to evaluate the genetic and metabolic parameters pertaining to adipocyte health and function. Specific Aim 2: Elucidate molecular mechanisms regulated by GAS5 in obese adipocytes: GAS5 levels are low in ASC and adipose tissue in obesity. A small molecule that stabilizes GAS5 has been recently developed. It is hypothesized that stabilizing GAS5 levels could alleviate the metabolic stress and the project will use this compound as a molecular tool to determine the underlying molecular mechanisms with functional readouts. Specific Aim 3: Investigate the impact of GAS5 stabilization in vivo in an obese mouse model: The in vitro data shows that the small molecule targeting GAS5 increases IR levels, restores insulin signaling and regulates GR-target genes. This aim will systematically elucidate the physiological effects of stabilizing GAS5 with the novel therapeutic in a diet-induced obese mouse model. Overall, this project fills significant gaps in knowledge to understand the role of lncRNAs in the metabolic processes affecting adipose tissue in obesity in humans. Identification of GAS5 as a druggable RNA target in a metabolic disease has led to successfully develop a small molecule therapeutic that stabilizes GAS5 (a frontier in genomic medicine) with a high potential of promoting the metabolic health of ASC and adipocytes in obesity. This project will have a considerable impact to prevent or treat metabolic dysfunction associated with obesity, thus impeding the ascent of obesity as the most preventable cause of death.