基于AMPK/mTOR/p70S6K信号通路的二甲双胍对大剂量地塞米松作用下成骨细胞自噬和凋亡的影响

Glucocorticoid-induced osteoporosis (GIOP) is a most common types of secondary osteoporosis. Our previous study showed that dexmethasone could induce osteoblast autophagy and apoptosis, that was involved in the pathogenesis of GIOP. So far, there are great limitations such as strong side effects in treatment of GIOP using bisphosphonates, although dose it represent main medication of GIOP currently. Thus, it is much necessary to develop novel strategies for GIOP with more effective and lower side effect medications. Recent studies have shown that metformin could promote bone formation by activation of AMPK. However, whether metformin can be used to prevent GIOP has not been investigated. AMPK/mTOR/p70S6K pathway is found involved in the regulation of cell autophagy and apoptosis. Here, we propose that metformin could regulate osteoblast via AMPK/mTOR/p70S6K pathway. We will detect osteoblast apoptosis and autophagy both in vivo and vitro under the combined treatment of dexmethasone with large dose and metformin simultaneously. We will observe under the conditions with different dosage and time course. Furthermore, we will evaluate the role of AMPK/mTOR/p70S6K pathway in the metfomin regulation of osteoblast, using different tools including pharmacological inhibitors, gene sliencing or overexpressing. This work will shed light on the novel function of metformin and provide new effective treatment strategy against GIOP.

糖皮质激素性骨质疏松(GIOP)危害巨大。我们前期研究发现地塞米松可能通过调节成骨细胞自噬和凋亡，导致GIOP发生，大剂量更明显。目前治疗GIOP药物副作用大，迫切需要寻找副作用小的有效药。研究表明，二甲双胍通过激活AMPK促进骨形成，后者还通过mTOR/p70S6K通路参与调节细胞自噬和凋亡。但目前二甲双胍与GIOP关系的研究甚少。我们推测二甲双胍可能通过AMPK/mTOR/p70S6K通路作用于成骨细胞调节骨代谢，拟先从整体动物水平研究不同剂量和不同作用时间的二甲双胍和大剂量地塞米松共同作用对大鼠成骨细胞功能及自噬、凋亡的影响；用离体成骨细胞研究二甲双胍和地塞米松共用下，成骨细胞骨代谢调节的细胞机制；并结合药物抑制剂、基因沉默或过表达等手段探讨二甲双胍对地塞米松作用下成骨细胞自噬和凋亡调节的具体分子机制。这为开拓二甲双胍的新作用和寻找GIOP防治新方法提供理论依据。

糖皮质激素性骨质疏松(GIOP)是最常见的继发性骨质疏松，危害巨大。我们前期研究发现地塞米松可能通过调节成骨细胞自噬和凋亡，导致GIOP发生，大剂量更明显。目前治疗GIOP药物副作用大，迫切需要寻找安全且有效的药物。研究表明，二甲双胍通过激活AMPK促进骨形成，通过mTOR/p70S6K通路参与调节细胞自噬和凋亡。但目前二甲双胍与GIOP关系的研究甚少。我们推测二甲双胍可能通过AMPK/mTOR/p70S6K通路作用于成骨细胞来调节骨代谢。.本研究先用不同剂量和不同作用时间的二甲双胍单独作用于SD大鼠在体和离体成骨细胞，研究二甲双胍对成骨细胞功能、凋亡和自噬的影响。然后用不同剂量和不同作用时间的二甲双胍和大剂量地塞米松共同作用于SD大鼠在体成骨细胞，观察大鼠成骨细胞功能及自噬、凋亡的变化；再提取SD大鼠原代的离体成骨细胞，研究二甲双胍和地塞米松共同作用对大鼠离体成骨细胞自噬、凋亡的影响以及具体的调节机制；采用药物抑制剂、基因沉默和过表达等手段探讨AMPK/mTOR/p70S6K信号通路是否参与二甲双胍减轻地塞米松对成骨细胞的不良影响。研究结果表明，二甲双胍可能通过增加地塞米松作用下成骨细胞自噬、抑制成骨细胞凋亡，进而促进骨形成，抑制骨吸收，从而发挥其骨保护作用；AMPK/mTOR/p70S6K 信号通路参与了二甲双胍减轻地塞米松对成骨细胞的不良影响。研究表明二甲双胍可改善糖皮质激素导致的骨密度降低，二甲双胍可能可以用于治疗糖皮质激素性骨质疏松。.本研究为二甲双胍治疗糖皮质激素骨质疏松提供了实验证据，表明二甲双胍不仅可以降糖，对于代谢性骨病可能有治疗潜能。今后仍需要更多的体内外实验，以及临床试验进一步证实二甲双胍是否可以用于治疗糖皮质激素骨质疏松症。