Akt/FoxO1/Ocn信号通路在1,25(OH)2D3调控糖尿病小鼠种植体骨整合的机制研究

Diabetes mellitus (DM) is a common metabolic disorder that results from an absolute or relative insulin deficiency and is characterized by hyperglycemia. DM is associated with multiple skeletal disorders, including osteopenia, osteoporosis, and so on. Dental implants have become a predictable treatment option for the healthy edentulous or partially edentulous patients. Considering the prevalence of DM among the world population and the severe periodontal disease and tooth loss in these patients, diabetic patients who seek rehabilitative therapies should be regarded as frequent patients in dental practice. However, the majority of studies suggested that DM could negatively interfere with the process of dental implant osseointegration. And some studies showed that the implant osseointegration in insulin-treated diabetic subjets is still lower than healthy contol. 1,25(OH)2D3, the biologically active form of Vitamin D (Vit D) is able regulate bone mineralization, and it also plays a functional role in the preservation of glucose tolerance. Our previous studies found that 1,25(OH)2D3 and insulin combined treatment had additive effects on reversing the impaired osseointegration capacity of implants in diabetic rats. And 1,25(OH)2D3 enhance the osseointegration by regulating osteocalcin and undercarboxylated osteocalcin secretion. However, the detail mechanism of the regulation is still unknown. FoxO1, which belongs to the Forkhead family of transcription factors, is a negtive regulator of insulin sensitivity and glucose tolerance. FoxO1 is expressed in many other cell types, where its functions are not known. Recently, it is found that skeleton my be a regulator of glucose metabolism in addition to the β cell and the hepotocyte, and osteoclacin could be the effector of FoxO1 in osteoblasts. So we propose that 1,25(OH)2D3 regulate the osteocalcin secretion and carboxylation through FoxO1in osteoblasts. In this suty, we are going to analyze the effect of FoxO1 acvitity on the implant osseointegration of diabetic mice by inducing diabeted mellitus in Col1α1.Cre+.FoxO1fl/fl mice. And using in vitro osteoblast cell culture, we will study the Akt/FoxO1/Ocn signaling pathway in high glucose enviroment regulated by 1,25(OH)2D3. The results of this study will add new knowledge in the mechanism of how 1,25(OH)2D3 regulate the bone metabolism and glucose metabolism, and provide novel insight in enhancing the implant osseointegration of diabetic patients.

糖尿病会影响种植体的骨整合，即使经胰岛素治疗也常不能完全恢复。课题组前期研究发现，1,25(OH)2D3治疗可通过调控骨钙素和未羧基化骨钙素的分泌，与胰岛素治疗产生叠加作用，促进糖尿病大鼠种植体骨整合至接近正常水平；但对于1,25(OH)2D3如何调控Ocn的分泌和其羧基化水平尚存在疑惑。最近研究发现FoxO1转录因子可通过作用于骨组织调控葡萄糖代谢，且骨钙素可能是FoxO1在成骨细胞的效应器，为阐明1,25(OH)2D3对骨钙素的调节机制提供了新的研究思路。本课题拟通过将成骨细胞特异性敲除FoxO1基因的小鼠诱发糖尿病，明确FoxO1活性对糖尿病小鼠种植体骨整合的影响；并结合体外成骨细胞的培养，探讨1,25(OH)2D3在高糖环境中作用于成骨细胞后，对Akt/FoxO1/Ocn信号通路的调控，为临床提高糖尿病患者骨整合提供理论依据。

糖尿病会影响种植体的骨整合，即使经胰岛素治疗也常不能完全恢复。课题组前期研究发现，1,25(OH)2D3治疗可通过调控骨钙素和未羧基化骨钙素的分泌，与胰岛素治疗产生叠加作用，促进糖尿病大鼠种植体骨整合至接近正常水平；但对于1,25(OH)2D3如何调控Ocn的分泌和其羧基化水平尚存在疑惑。最近研究发现FoxO1转录因子可通过作用于骨组织调控葡萄糖代谢，且骨钙素可能是FoxO1在成骨细胞的效应器，为阐明1,25(OH)2D3对骨钙素的调节机制提供了新的研究思路。.本课题拟通过将成骨细胞特异性敲除FoxO1基因的小鼠诱发糖尿病，明确FoxO1活性对糖尿病小鼠种植体骨整合的影响；并结合体外成骨细胞的培养，探讨1,25(OH)2D3在高糖环境中作用于成骨细胞后，对Akt/FoxO1/Ocn信号通路的调控。项目研究发现，敲除成骨细胞上的FoxO1提高了血清中OCN及ucOCN%的水平，改善糖尿病小鼠糖代谢，从而提高种植体骨结合率。1,25(OH)2D3通过激活PI3K/AKT信号通路，抑制其下游基因FoxO1活性，从而发挥其调节糖代谢和骨代谢的作用。体外实验也证实，高糖降低了WT来源成骨细胞的成骨标志物，抑制了其分化潜能。1,25(OH)2D3通过作用于VDR，激活PI3K/AKT，抑制了FoxO1的活性，从而提高了成骨细胞分化能力。.本项目明确了1,25(OH)2D3对于改善糖尿病小鼠种植体骨整合的机理，明确了FoxO1转录因子活性在这一调节过程中的重要作用。提示全身运用1,25(OH)2D3及局部使用FoxO1抑制剂可能提高糖尿病患者的种植体成功率。