SIRT1调控CLOCK/BMAL1介导的生物钟信号在追赶生长胰岛beta细胞功能损伤中的作用

Catch-up growth is tightly related to type 2 diabetes in China. Our previous work revealed that islet beta cell dysfunction appeared in the early stage of catch-up growth animal model and SIRT1 might play the a vital role of in catch-up growth induced beta cell dysfunction. Accumulating evidences show abnormal circadian clock system controlled by CLOCK/BMAL1 can induce beta cell dysfunction, and SIRT1 is a key factor in modulating circadian rhythm. Our further experiment showed the expressions of CLOCK and BMAL1 protein were decreased in islets of catch-up growth group compared with those in normal group. We hypothesized that SIRT1 could sense the change of nutrition transition and promote the gene expressions and post-transcriptional modification, so it might play an essential role in the relationship among nutrition transition, circadian rhythm and beta cell function. In order to verify the assumption, we intend to compare the levels and rhythm of insulin secretion, the expressions of circadian clock gene and the levels of their acetylation, and the expressions and activity of SIRT1 in the different stages of catch-up growth. To further explore the mechanism of SIRT1 on beta cell function, we will detect the changes of circadian signaling and beta cell function with or without intervention aiming at sirt1 or clock. We believe these studies may open new directions for understanding the mechanism of beta cell dysfunction induced by environment.

追赶生长与我国2型糖尿病高发有关。我们前期研究发现，追赶生长模型较早出现了胰岛功能损伤，SIRT1可能在其中发挥了重要作用。现有研究证实CLOCK/BMAL1调控的生物钟信号紊乱可显著影响胰岛功能，SIRT1是生物节律的关键性调节因子。我们进一步研究证实，追赶生长模型胰岛CLOCK和BMAL1蛋白表达水平下降。因此我们推测， SIRT1感知营养变化，促进CLOCK/BMAL1介导的基因转录及转录后修饰，实现营养变化－生物钟节律－beta细胞功能调控间的紧密联系。本研究拟观察追赶生长大鼠不同阶段胰岛分泌功能，胰岛素分泌和生物钟相关基因表达及乙酰化水平及SIRT1表达和活性变化；通过体内外调控SIRT1及CLOCK的表达，在不同层面探讨SIRT1调控胰岛功能的靶点和信号通路。本研究可望为胰岛beta细胞功能保护提供新的干预靶点。

追赶生长与我国2型糖尿病高发有关。追赶生长营养提升过程中胰岛功能变化如何研究较少。本研究发现，追赶生长动物模型较早出现胰岛beta细胞形态和胰岛素分泌功能异常，伴有胰岛SIRT1、 PDX-1基因表达水平下降，UCP2表达上升。同时对胰岛时钟基因的表达水平进行了分析，结果发现胰岛CLOCK和BMAL1 mRNA和蛋白表达在追赶生长4周和8周时较正常组有不同程度的下降。为阐明CLOCK/BMAL1介导的生物钟信号通路在追赶生长所致胰岛beta细胞功能障碍中的作用，在体内外双向干预SIRT1或CLOCK表达探讨对生物钟信号通路和beta细胞功能的影响。结果显示，上调胰岛SIRT1表达可改善胰岛分泌功能，提升CLOCK和周期蛋白(PER2)表达，上调CLOCK表达有相似的结果，同时SIRT1 mRNA和蛋白表达提升。下调SIRT1或CLOCK表达可观察到与之相反的结果。上述动物实验结果说明SIRT1 和CLOCK存在相互促进作用，共同影响下游靶基因PER2的表达，发挥对胰岛分泌功能的影响。本研究以追赶生长动物模型为基础，探讨了营养变化－生物钟节律－beta细胞功能调控－糖尿病之间的作用通路，证明SIRT1/CLOCK介导的生物钟信号作用异常参与了追赶生长中的胰岛beta细胞的损伤。上述研究进一步拓展和深入研究营养变化致胰岛功能障碍的机制,为临床实现beta细胞保护甚至糖尿病逆转寻找新的思路与治疗靶点。