【作者】 张雄飞；

【导师】 韩晓；

【作者基本信息】 南京医科大学 ， 生物化学与分子生物学， 2007， 博士

【摘要】 糖皮质激素类药物，在临床上广泛应用于治疗多种疾病，但长期、大量地使用会产生一些严重的副作用，其中包括类固醇性糖尿病(steroid diabetes mellitus，SDM)。类固醇性糖尿病发生的分子机制仍不十分清楚。FoxO蛋白家族作为胰岛素／胰岛素样生长因子(INS／IGF)信号通路中的关键调节因子，在胰岛β细胞功能障碍中可能发挥着重要作用。在本研究中我们探讨了糖皮质激素类药物地塞米松对胰岛β细胞系RINm5F内FoxO家族成员Foxol表达及活性的影响。结果发现地塞米松能够诱导RINm5F细胞内Foxol的表达，且该作用是糖皮质激素受体(GR)依赖性的。此外，地塞米松可以下调Foxol的磷酸化水平及其上游的磷酸化AKT水平，并且PI3-K／Akt信号通路的激动剂IGF-1能够逆转该作用。然而，糖皮质激素受体竞争性拮抗剂不但不能拮抗地塞米松下调p-AKT及p-Foxol蛋白水平的作用，而且还发挥了与地塞米松类似的作用。PDX-1作为Foxol在胰岛β细胞内重要的靶基因，其表达水平下降与胰岛β细胞功能障碍相关。萤光素酶报告基因方法显示地塞米松可以促进RINm5F细胞内Foxol的转录活性。通过RNA干扰实验，我们发现地塞米松部分通过增加活性Foxol抑制PDX-1基因表达。另外，我们的研究初步表明地塞米松通过增加活性形式的Foxol即核内Foxol引起PDX-1核输出。总之，我们的研究表明地塞米松能够部分通过增加活性Foxol抑制PDX-1基因表达，并且地塞米松可能通过增加活性形式的Foxol即核内Foxol引起PDX-1核输出。本研究结果为理解地塞米松引起类固醇性糖尿病和胰岛β细胞功能障碍的分子机制提供了新视点。更多还原

【Abstract】 Glucocorticoids are widely used in clinical therapy and steroiddiabetes is one of the side effects of glucocorticoid treatment. Themolecular mechanisms involved in the process of steroid diabetes are notfully understood. The Foxo proteins, key transcriptional effectors ofinsulin and IGF signaling pathways could play an important role inβ-celldysfunction. In this study, we investigated the role of syntheticglucocorticoid, dexamethasone in the expression and activity of Foxofamily member Foxol inβ-cells. The results showed that dexamethasoneinduced Foxol expression in pancreaticβ(RINm5F) cells and this effectwas glucocorticoid receptor (GR)-dependent. Additionally,dexamethasone decreased the phosphorylation of Foxol and thephosphorylation of AKT, upstream of Foxol, and stimulant ofPI-3kinase/Akt signaling pathway reverted this effect. However, GRcompetitive antagonist couldn’t block this effect and played a same roleas dexamethasone. The decrease of PDX-1, an important target gene ofFoxol in [3-cells, is involved inβ-cell dysfunction. Luciferase reporterstudies proofed that dexamethasone could increase Foxol transcriptional activity. Through RNA interference, we indicated that dexamethasonereduces PDX-1 expression partially by the increase of active Foxol.Besides, our research indicated that dexamethasone could induce PDX-1nuclear export by the increase of nuclear Foxo 1.In conclusion, the present study suggest that dexamethasone reducesPDX-1 expression partially by the increase of active Foxol and couldinduce PDX-1 nuclear export by the increase of nuclear Foxol. Thisnovel viewpoint will replenish the molecular mechanism of steroiddiabetes andβ-cell dysfunction induced by dexamethasone.更多还原