RAGE在糖尿病性骨质疏松症发病中的调控作用及其机制研究

Osteoporosis caused by diabetic mellitus is characterized by reduced bone quanlity and increased facture incidence. However, the mechanism for pathological process is still under investigation. And it has become the hot topic in the field of bone metabolism research. The thorough understanding of the disorder status is crititcal for human health and medical economies. It is important for the developement of gene regulation and its pathway in elucidating the novel treatment target. Our previous works on primary cultured osteoblasts showed the upregulation of RAGE expression and the down-regulation of Wnt/β-catenin pathway by the effect of AGE. The inhibited role of RAGE in osteoblastic proliferation and mineralization may be the cause of the occurrence of diabetic osteoporosis. Further, this study will point to the research of RAGE gene function with the utilization of animal models, adenoviruses and transfection techniques etc. which is demonstrated as followings: (1) Obeservation of the osteoporosis and β-catenin gene expression changing by using shRNA-RAGE in the bone of diabetic mice; (2) Regulation between RAGE and β-catenin by using β-catenin gene knockout mice, and the rescue by over-expression of β-catenin in bone; (3) Mechanism of the regulation between RAGE and β-catenin in vitro; (4) Genetic interaction of RAGE gene and diabetic osteoporosis in cohort study. This project may help clarifying comprehensively the pathogenesis in the bone defects of diabetes within the scope of animal models, molecular level and epidemiological study. And it will definitely provide solid evidence and rational to develop therapeutic agents for diabetic osteoporosis.

糖尿病性骨质疏松的特征为糖尿病患者骨质量下降和骨折发生率的增加。该症关键调控基因和信号通路的体外成骨细胞实验发现RAGE通过抑制β-catenin参与成骨增殖和矿化损伤。本项目将运用分子生物学方法、基因敲除小鼠培育、尾静脉注射、腺病毒构建和转染等技术开展以下工作:（1）shRNA病毒沉默糖尿病小鼠骨组织RAGE表达，观察骨质疏松改善情况及β-catenin基因表达变化;（2）利用β-catenin基因敲除小鼠明确RAGE与β-catenin的调控关系；糖尿病小鼠骨组织过表达β-catenin观察能否逆转RAGE的作用;（3）体外细胞和分子水平研究RAGE调控β-catenin的机制;（4）人群队列中检测RAGE基因与糖尿病性骨质疏松症发生的遗传关联性。从而在动物、分子和人群三个层面上阐释RAGE基因对糖尿病骨质量的调控及其机制，有望为糖尿病性骨质疏松的防治提供创新的理论依据和治疗靶点。

建立人群队列，共收集934例人群样本（621例2型糖尿病（T2DM）男性，313例健康女性）。横断面研究分析骨量与各代谢物的关联测定血尿酸、糖代谢和脂代谢指标、骨转换指标、骨密度（BMD）检测等。发现以尿酸为代表的抗氧化因子，是决定糖尿病患者骨量的决定性关联。同时发现反映破骨细胞活性的标志物血清I型胶原羧基末端肽（CTX）在正常血糖女性中随HbA1c改变而变化的特征，提示破骨细胞可能参与糖尿病和糖尿病性骨质疏松症的发生。首次提出骨骼作为重要的内分泌器官以保护性的骨吸收增强主动防御血糖进一步升高的假设。随后通过对该女性队列人群4年前瞻性随访，首次验证了破骨细胞以代偿-耗竭双相模式主动参与糖稳态调控的理论。该发现丰富了糖尿病发病机制的内涵及其继发骨质疏松症的内在关联。在临床治疗中避免过度骨吸收抑制剂，维持糖尿病性骨质量缺陷患者适度骨吸收，以期达到糖稳态提供了重要警示意义。. 糖代谢紊乱和骨代谢的关联研究表明降糖药物GLP-1类似物除降糖作用以外有改善骨质量的作用，但已有的证据在探索药物干预2型糖尿病骨质量缺陷的治疗上是远远不够的。在动物及细胞水平上发现成骨细胞表达GLP-1受体提示GLP-1类似物对糖尿病患者骨质量和骨折风险影响存在理论基础。因此为规范糖尿病骨质疏松症合理药物治疗寻找依据，本研究旨在大鼠上验证GLP-1类似物是否影响骨质量，并初步探讨影响产生的机制。对非糖尿病大鼠注射两种最常用的降糖药物GLP-1类似物，即利拉鲁肽和艾塞那肽，均证实对骨质量和骨髓基质干细胞成骨成脂分化方向有影响。提示GLP-1类似物即便在血糖正常个体中也有潜在益处。更为糖尿病性骨质疏松症患者使用该类药物降糖治疗时，除血糖获益的目标外，同时达到改善骨质量的目的提供了十分重要的理论基础。