A2aR/Egr-1/Pdx-1信号介导咖啡因所致的胎胰腺发育异常

Developmental origin of diabetes is associated with impaired fetal pancreatic development which is characterized by insufficient mass and malfunction of β cells. We have previously found that prenatal caffeine exposure induced impaired pancreatic development in intrauterine growth retarded fetal rats, which could be persisted to adulthood and caused glucose intolerance and increased susceptibility to diabetes, but the mechanism remained unknown. As a master regulator of differentiation and function during fetal pancreatic development, pancreatic and duodenal homeobox 1 (Pdx-1) is positively regulated by early growth response 1 (Egr-1). Meanwhile, Egr-1 can recruit histone acetyltransferase to epigenetically regulate target genes while it is also modulated by upstream cAMP/PKA signaling. Caffeine could inhibit cAMP/PKA signaling by antagonizing adenosine receptor 2a (A2aR). The preliminary experimental results showed that prenatal caffeine exposure decreased the mRNA expressions of pancreatic A2aR Egr-1 and Pdx-1. Basing on the above, we hypothesize that caffeine may suppress A2aR/cAMP/PKA/Egr-1 signaling, which results in lowered histone acetylation and decreased expressions of Pdx-1 and finally impairs fetal pancreatic development. The aim of the present project is to demonstrate the epigenetic mechanism of A2aR/Egr-1/Pdx-1 signaling mediated impaired fetal pancreatic development induced by caffeine in vivo and in vitro. This project would provide theoretical and experimental basis for addressing developmental toxicity of caffeine and exploring the early prevention strategy of fetal originated diabetes.

糖尿病的发育起源与胎胰腺发育异常有关，后者表现为β细胞数量不足和功能低下。我们前期发现，孕期咖啡因暴露所致宫内生长迟缓胎鼠胰腺发育异常可延续至成年，引起糖耐量减低和糖尿病易感，但机制不明。文献提示，胰腺发育分化和功能主控基因Pdx-1表达受早期生长反应因子-1（Egr-1）正向调节，后者可招募组蛋白乙酰化酶影响靶基因表遗传修饰并且自身受cAMP/PKA通路调控。咖啡因可通过拮抗腺苷受体2a（A2aR），抑制cAMP/PKA通路。预实验发现，咖啡因可致胎鼠胰腺A2aR、Egr-1和Pdx-1表达降低。推测：咖啡因可抑制A2aR/cAMP/PKA/Egr-1信号，引起Pdx-1组蛋白乙酰化及表达降低，导致胎胰腺发育异常。本项目拟从整体和细胞水平，阐明A2aR/Egr-1/Pdx-1信号介导咖啡因所致胎胰腺发育异常的表遗传调控机制，为认识咖啡因发育毒性和寻找胎源性糖尿病早期防治策略提供相关依据。

糖尿病的发育起源与胎胰腺发育异常有关，后者表现为β细胞数量不足和功能低下。我们前期发现，孕期咖啡因暴露所致宫内生长迟缓胎鼠胰腺发育异常可延续至成年，引起糖耐量减低和糖尿病易感，但机制不明。本项目通过整体和细胞水平证实，孕期咖啡因暴露可以导致胎鼠胰腺发育异常和胰岛素合成功能抑制。其发生机制主要与孕期咖啡因暴露引起的胎鼠母源性糖皮质激素（GC）过暴露有关，而非咖啡因直接作用所致。GC与糖皮质激素受体（GR）结合,通过下调胰岛素样生长因子1（IGF1）表达从而抑制胰岛素基因的表达并导致胰岛素合成功能受损。在此基础上，我们将原研究内容进行了拓展：首先，证实了GC-IGF1轴参与编程孕期咖啡因暴露所致子代大鼠胰腺发育不良和胰岛素合成功能改变以及糖耐量异常。其次，通过选择出生后不同时间点进行研究，发现孕期咖啡因暴露子代大鼠出生后糖代谢功能存在代偿性变化，其机制可能与肝脏胰岛素信号通路增强有关。同时，在高脂饮食诱导下呈现出“高血糖，低血胰岛素”为特征的糖尿病样反应。同时，结合孕期乙醇暴露大鼠模型探讨了孕期外源物暴露对胰腺发育和糖代谢影响的共性特征，发现孕期乙醇暴露所致雄性子代年龄进程性糖代谢异常和胰腺功能紊乱，其机制可能亦与出生前后胰腺“GC-IGF1”轴编程改变有关。最后，通过与其他团队合作，以人工合成类GC——地塞米松作为阳性对照，证实了血管紧张素II型受体-2（AT2R）表遗传抑制是介导孕期地塞米松暴露所致子代β细胞功能和糖耐量异常的分子机制。。此外，孕期乙醇暴露所致子代神经内分泌代谢编程改变还具有可遗传性。本项目已发表SCI论文4篇、北大中文核心期刊论文1篇、统计源期刊论文1篇，相关科研成果为认识咖啡因发育毒性和寻找胎源性糖尿病早期防治策略提供了重要参考。