内质网自噬介导孕期咖啡因暴露所致肝脂质氧化编程改变

Autophagy plays an important role in liver lipid metabolism. The biological significance and underlying mechanisms of autophagy on fetal hepatic development which is poorly clarified. We have previously demonstrated that prenatal caffeine exposure (PCE) in rodents could induce intrauterine growth retardation (IUGR) and the susceptibility of fatty liver diseases. The underlying mechanism might be associated with fetal over-exposure to maternal glucocorticoids (GC) and metabolic programming alteration of fetal hepatic lipid synthesis. Recently, based on an established IUGR model by PCE, we focused on PCE-induced autophagy and excessive accumulation of lipid of fetal liver. Meanwhile, GC could induce autophagy in fetal hepatic cells in vitro. According to the relevant literatures, we hypothesize that GC could up-regulate glucocorticoid receptor/CEBP homologous protein (GR/CHOP) and recruit CBP, and then enhanced histone acetylation and expression levels of ATG14L (reticulophagy marker proteins), which could enhance lysosome related lipid oxidation and suppress fetal hepatic steatosis. This project plan to explore the internal connection of “GC—induced expression of GR/CHOP and recruited CBP—enhanced histone acetylation levels and expression levels of ATG14L—activated reticulophagy—enhanced lipid metabolism”, and to clarify the molecular mechanisms and physiological significance of reticulophagy in PCE-induced the abnormality of hepatic lipid metabolism. This study would provide a valuable experimental and theoretical basis for the prevention strategies of the fetal originated fatty liver diseases.

自噬参与肝脏脂代谢功能，然而其在胎肝发育中的发生机制及意义尚未阐明。我们前期证实，孕期咖啡因暴露（PCE）可引起子代大鼠宫内发育迟缓及成年脂肪肝易感，其机制与宫内母源性糖皮质激素（GC）过暴露编程胎肝脂质合成功能增强有关。近期我们发现PCE胎鼠肝脏自噬和脂质氧化增加；细胞水平证实GC可诱导胎肝自噬。综合文献提示：宫内高GC通过活化糖皮质激素受体/CCAAT增强子结合蛋白同源蛋白（GR/CHOP）并招募CREB结合蛋白(CBP)，引起内质网自噬活化标志蛋白ATG14L组蛋白乙酰化及表达增加，促进脂质氧化，抑制胎肝脂肪变。本项目拟探讨“宫内高GC—胎肝细胞GR/CHOP活化—入核结合至ATG14L启动子并招募CBP—ATG14L组蛋白乙酰化及表达增加—内质网自噬增强—脂质氧化增加，脂质蓄积减少”之间内在联系，阐明GC所致胎肝自噬增强的分子机制及意义，为探寻胎源性脂肪肝早期防治策略提供实验依据。

非酒精性脂肪肝病（non-alcoholic fatty liver disease, NAFLD）是指除酒精外，由多种病因引起的弥漫性肝实质细胞脂肪变性，以甘油三酯（triglyceride, TG）蓄积为主要特征的临床病理综合征。自噬不仅参与肝脏细胞分化和衰老等生理过程，而且与肝脏多种疾病（包括NAFLD）的病理改变密切相关。本项目发现孕期咖啡因暴露（prenatal caffeine exposure, PCE）致雄、雌性子代大鼠NAFLD易感且具有宫内起源，其发生机制与CTSD调控的自噬相关并具有性别差异。即在雄性子代中，PCE通过宫内高GC暴露激活GR入核，上调miR-665表达，使CTSD表达抑制，从而损坏自噬溶酶体降解，进而减弱细胞脂质β-氧化功能，导致肝细胞内脂质蓄积。这种GC依赖性miR-665高表达所致的CTSD表达抑制可延续至出生后，最终介导了肝细胞脂质蓄积及NAFLD易感，在子代出生后“二次打击”（高脂饮食或慢性应激）下诱导NAFLD发生；而在雌性子代中，PCE所致子代大鼠NAFLD易感主要由于肝脏脂质合成功能增强，自噬在其中不发挥明显调控作用。本研究提出PCE所致子代肝脏自噬在胎源性NAFLD中的作用及机制，证实高GC通过GR-miR-665-CTSD调控自噬溶酶体降解损坏，减弱细胞脂质β-氧化功能，导致肝细胞内脂质蓄积。为解析国际前沿问题——“健康与疾病的发育起源”（DOHaD学说）提供了理论与实验依据。基于此项目我们获得了一些原创性研究成果，包括发表SCI论文2篇，中文核心论文4篇（均标注）。