通过调节成骨细胞的重要Wnt信号通路探索2型糖尿病增加骨折风险的机制及治疗新策略

Along with the intensification of aging in our country population, the prevalence of type 2 diabetes mellitus (T2DM) and osteoporotic fracture is dramatically increasing. Moreover, compared to non-diabetic patients, fracture risks associated with T2DM are greatly increased and have already become very serious public health issues. However, the underlying mechanisms caused the increased fracture risks in T2DM are still unclear, and there is lack of specific therapy for osteoporotic fractures in patients with T2DM. Recent studies have shown that increased expression of Wnt antagonists is closely associated with increased fracture risks in T2DM, but no studies have investigated Secreted frizzled-related protein (SFRP) and Dickkopf-1 (DKK-1), which are very important Wnt antagonists, in T2DM animal models with fracture. Therefore, we put forward a hypothesis that increased expression of DKK-1 and SFRP will suppress the bone formation, impair the bone strength and increased the fracture risks in T2DM, and DKK-1 antibody will be very effective in alleviating those abnormalities. In order to prove our hypothesis, we will construct a T2DM rat model with femoral closed fracture and treat the rat with DKK-1 antibody for the first time. We will investigate the influence of DKK-1 and SFRP on the bone metabolism, bone strength and fracture healing abilities of rats, and on the differentiation and proliferation abilities of osteoblasts, before and after DKK-1 antibody treatment. This study will probably reveal the underlying mechanisms causing the increased fracture risks in T2DM, and will provide a very promising therapy strategy.

随着我国人口老龄化的加剧，2型糖尿病（T2DM）和骨质疏松性骨折的患病率迅猛增加，T2DM更是导致骨折风险增加的重要原因之一，这无疑将对我国公共健康造成巨大威胁。但是，T2DM增加骨折风险的机制目前仍不清楚，且针对T2DM骨折患者的特异性治疗极为缺乏。近年来，研究发现Wnt通路抑制因子的高表达与T2DM骨折风险密切关联。但目前尚无DKK1和SFRP等抑制因子在T2DM骨折模型中的相关研究。因此，我们通过构建T2DM骨折大鼠模型，并首次应用DKK1抗体进行治疗，分析治疗前后上述抑制因子表达水平对大鼠骨形成和骨骼生物力学的影响，以及促进骨髓间充质干细胞成骨分化和增殖的作用，从细胞、组织和动物水平验证我们的假说：DKK1、SFRP高表达是导致T2DM骨形成抑制、骨强度下降和骨折风险增加的重要机制，而DKK1抗体可有效改善上述异常。本研究有助于揭示T2DM骨折风险增加的具体机制，并探索治疗新策略。

2型糖尿病（T2DM）和骨质疏松症是两种严重影响公众健康的慢性疾病，防治形势极为严峻。T2DM是导致骨折风险增加的重要原因之一，但致病机制尚不清楚，针对T2DM骨折患者的特异性治疗极为缺乏。近年来，研究发现成骨信号通路Wnt/β-catenin抑制因子的高表达与T2DM骨折风险密切关联。但目前尚无DKK1等抑制因子在T2DM模型中的相关研究。因此，我们通过构建T2DM小鼠模型，首次应用DKK1-Cre腺病毒进行干预，分析干预前后小鼠骨形成和骨骼生物力学的变化，验证Wnt/β-catenin成骨信号通路抑制是导致T2DM骨形成抑制、骨强度下降和骨折风险增加的重要机制，而DKK1-Cre腺病毒可有效改善上述异常，探索DKK1作为T2DM骨代谢异常相关治疗靶点的潜在价值。1. 本课题首次在中国人群中证实，T2DM可增加新发非椎体骨折风险，首次校正可用于评估T2DM人群骨折风险的骨密度参数。2. 本课题先后利用去卵巢手术、高糖高脂饲料喂养和链脲霉素注射成功构建绝经后T2DM小鼠模型。通过血清学和骨组织免疫组化测定骨转化指标，证实骨形成抑制可能为T2DM主要骨代谢异常和致病机制。通过MicroCT测定体积骨密度和骨微结构，证实T2DM小鼠同时存在皮质骨和松质骨骨微结构损害，揭示T2DM骨折高风险的潜在原因。3. 本课题利用DKK1-Cre腺病毒干预，首次构建DKK1敲除T2DM小鼠模型。研究证实DKK1-Cre腺病毒干预可显著改善T2DM小鼠皮质骨微结构、增加皮质骨密度。揭示DKK1有潜力成为T2DM相关骨质疏松、骨微结构异常和骨折风险增加的新型干预靶点。