雌激素相关受体alpha调控脂肪因子介导脂肪-骨组织间对话的机制研究

Bone metabolism is subjected to the complex influences of multiple factors. Our previous work illustrated that nuclear hormone receptor ERRa governs the expression of a novel target gene glutaminase (Gls), affecting mitochondrial glutamine metabolism and enhancing energy; thus, promoting the osteogenic differentiation of mesenchymal stem cells (MSCs). Paradoxically, high-fat-diet induced obese mice treated with an ERRa inverse agonist were found to have increased bone density and reduced bone loss. On the other hand, we recently discovered that ERRa can induce the expression of several adipokines including leptin. Based on these new evidences, we propose a novel hypothesis: ERRa regulates adipokines such as leptin mediating the tissue crosstalk between fat and bone. We aim to test this hypothesis by generating fat tissue specific ERRa knockout mice, challenging with high-fat-diet, replacing with wild type fat tissue by transplantation, and supplementing with recombinant leptin to assess the role of ERRa in the tissue cross talk between fat and bone. In addition, we will employ techniques such as enhancer/promoter mutation, chromatin immunoprecipitation, adenovirus-mediated overexpression to illustrate how ERRa additionally fine tunes bone metabolism through governing the expression of adipokines such as leptin, highlighting how obesity and metabolic dysregulation affects ERRa function and thus bone metabolism.

骨代谢平衡受到多重复杂因素影响，我们前期发现核受体ERRα调控新靶基因Gls，影响线粒体谷氨酰胺回补代谢，促进间充质干细胞成骨分化。然而在高脂饮食诱导的肥胖小鼠模型中，却发现ERRα抑制剂增加骨密度、防止骨丢失，进而发现ERRα可能调控脂肪因子leptin启动子的表达，据此我们提出新的假说：ERRα通过调控脂肪因子介导脂肪与骨组织间对话。本项目拟构建ERRα脂肪组织特异性敲除小鼠，结合高脂饮食、脂肪组织移植、leptin替代等动物实验方法，采用启动子点突变、染色质免疫共沉淀、慢病毒表达等分子技术，阐明ERRα转录调控leptin等脂肪因子的新分子机制，揭示核受体ERRα调控骨代谢的新作用方式。明确ERRα通过调控脂肪因子介导脂肪与骨组织间对话的作用机制，对研究骨代谢紊乱与肥胖等代谢性疾病的关联机制具有重要的科学创新意义和临床参考价值。

骨稳态平衡受到多重复杂因素影响，骨稳态失衡与肥胖等其他代谢性疾病密切相关。孤核受体雌激素相关受体 alpha（ERRα）是细胞代谢的重要调控因子，本项目主要研究发现了ERRα调控脂肪细胞leptin（正调控）和osteopontin(负调控)基因的转录表达，影响其分泌到血液中，从而介导了脂肪与骨组织间交互影响。通过构建脂肪细胞特异敲除ERRα小鼠（ERRαAKO），发现ERRα表达缺失在Sham小鼠和OVX雌激素缺乏的骨质疏松小鼠模型中未影响体重、脂重及血脂等表型，而ERRαAKO小鼠leptin等因子在脂肪组织表达和血清含量有明显差异，并证实ERRαAKO小鼠骨吸收未改变而骨形成增加，因此显著改善OVX诱导的骨质疏松。采用启动子点突变、染色质免疫共沉淀等方法，首次揭示ERRα结合leptin启动子ERRE位点，证实其直接调控leptin转录表达的新分子机制。通过ERRα拮抗剂C29、腺病毒过表达等处理分化的脂肪细胞3T3-L1，进一步证实ERRα影响成熟脂肪细胞表达及分泌leptin和osteopontin，同时，ERRα拮抗剂C29处理高脂饮食诱导的肥胖骨质疏松雄鼠模型，也显著降低了血清leptin和骨丢失，再次证实了脂肪组织ERRα通过调控leptin和osteopontin分泌影响骨稳态。此外，我们还发现天然小分子穿心莲内酯是ERRα的新型拮抗剂，在OVX和高脂饮食肥胖两种骨质疏松模型中显著改善骨量丢失。因此，我们研究明确了脂肪组织中ERRα调控leptin和osteopontin转录表达和分泌，介导脂肪与骨两种组织间互作的机制，对研究骨稳态失衡与肥胖等代谢性疾病的关联机制具有重要的科学意义和临床参考价值。