PPARG regulates osteocyte bioenergetics and function during aging

随着年龄的增长，骨丢失和能量代谢障碍会普遍导致骨折和糖尿病。作为一种 骨骼是骨骼重塑和维护所需能量的最大消耗之一。 骨骼动态平衡。骨重建受到骨细胞的控制，骨细胞占骨细胞的90%-95%， 哪个生物能量项目在很大程度上是未知的。新证据表明，核受体PPARG，即 是全球能量代谢的调节者，也是治疗高血糖的药理靶点，调节 骨细胞能量代谢及其功能，包括WNT途径的抑制因子--硬化素的产生 活性和调节骨骼重塑的关键蛋白质。本申请中提出的研究将提供 骨细胞生物能量学及其在骨代谢中的作用与全身的关系 能量代谢，以及骨骼是否通过骨细胞内分泌活动充当身体的“能量调节器”。这个 主要假设是PPARG活性随年龄的变化会改变骨细胞的功能和生物能量学 从而同时减少骨形成和能量代谢。这一假说将 在三个具体目标上进行测试。目标1将确定燃料选择和老化如何影响骨细胞功能和 这些进程是否依赖于PPARG。用老龄C57BL/6和γOTKO小鼠，骨器官 培养，以及PPARG下调的成骨细胞样MLO-Y4细胞，结合转录本， 定量蛋白质组学和共培养实验，PPARG对骨细胞老化的贡献将被定义。 目的2将骨细胞的PPARG蛋白相互作用组与脂肪细胞的相互作用组进行对比 对完全激动剂罗格列酮或反向激动剂SR10171的反应，以确定最佳 PPARG调节剂对骨骼和新陈代谢的有益影响。分析将在骨细胞上进行- 像MLO-Y4细胞一样使用定量串联质量标签蛋白质组学。目标3将定义PPARG的动态 SOST启动子中存在的PPRE序列上的相互作用组作为衰老的函数和对 PPARG活性的药理调节。这一应用的前提是为精准 骨细胞PPARG活性的药物治疗同时改善骨骼和 老年人代谢功能障碍。

Bone loss and impairment in energy metabolism with aging prevalently lead to fractures and diabetes. As an organ, the skeleton is one of the largest consumers of energy needed for bone remodeling and maintenance of bone homeostasis. Bone remodeling is under control of osteocytes, which constitute 90-95% of bone cells, and which bioenergetic program is largely unknown. New evidence indicates that nuclear receptor PPARG, which is a global regulator of energy metabolism and pharmacological target to treat hyperglycemia, regulates osteocyte energy metabolism and their function including production of sclerostin, an inhibitor of WNT pathway activity and a key protein regulating bone remodeling. Research proposed in this application will provide an insight into the connection between osteocyte bioenergetics, its function in bone metabolism and systemic energy metabolism, and whether bone acts as the body “energostat” via osteocyte endocrine activities. The leading hypothesis is that changes in PPARG activity with aging alter osteocyte function and bioenergetics resulting in simultaneous decrease in bone formation and decrease in energy metabolism. This hypothesis will be tested in three specific aims. Aim 1 will determine how fuel choice and aging affect osteocyte function and whether these processes are PPARG dependent. With the use of aged C57BL/6 and γOTKO mice, bone organ cultures, and osteocyte-like MLO-Y4 cells with down-regulated PPARG, in combination with transcriptomics, quantitative proteomics, and coculture experiments, PPARG contribution to osteocyte aging will be defined. Aim 2 will contrast the PPARG protein interactome of osteocytes with the interactome of adipocytes, in response to either full agonist rosiglitazone or the inverse agonist SR10171, in order to define an optimal PPARG modulator for its beneficial effects on bone and metabolism. The analysis will be done on osteocyte- like MLO-Y4 cells using quantitative Tandem Mass Tag Proteomics. Aim 3 will define dynamics of PPARG interactome on PPRE sequences present in Sost promoter as a function of aging and in response to pharmacological modulation of PPARG activity. The premise of this application is to set a stage for precise pharmacologic manipulation with PPARG activities in osteocytes to simultaneously improve skeletal and metabolic dysfunction in elderly.