慢性间断性缺氧对雄仔鼠肝胰岛素样生长因子-1基因组蛋白修饰的作用

Effects of chronic intermittent hypoxia on the histone modification of insulin-like growth factor-1 gene in male offspring rats

目的:研究慢性间断性缺氧(CIH)时新生雄仔鼠肝形态学改变及胰岛素样生长因子-l(IGF-1)基因表达,探讨其表观遗传学分子机制。方法:将怀孕SD大鼠分为正常呼吸组(对照组)和间断缺氧组(缺氧组),建立CIH大鼠模型。分娩后取对照组和缺氧组1d雄仔鼠肝组织,用电子显微镜观察肝组织的超微结构,免疫蛋白印迹和免疫组织化学显色检测肝组织IGF-1蛋白表达;real-time PCR检测IGF-1 mRNA表达水平,染色质免疫共沉淀(ChIP)技术检测IGF-1组蛋白修饰情况。结果:电镜下见缺氧组肝细胞有微量脂肪滴。缺氧组IGF-1 mRNA及蛋白表达水平较对照组显著下降。ChIP结果显示,缺氧组IGF-1基因Proximal 3'UTR、Exon 5、Distal 3'UTR片段的H3k9ac位点的组蛋白乙酰化修饰水平较对照组显著降低。结论:CIH可致缺氧组新生仔鼠肝IGF-1基因组蛋白乙酰化修饰水平改变,可能参与雄仔鼠非酒精性脂肪肝的发生和发展。

Objective:To study the morphological changes of the liver and the expression of insulin-like growth factor-1(IGF-1)gene in the newborn male rats during chronic intermittent hypoxia(CIH),and study the possible epigenetic molecular mechanism.Methods:The clean pregnant SD rats were divided into normal breathing group(control group)and intermittent hypoxia group(hypoxia group).The model of CIH rats was established.Two groups of 1-day-old male offspring rats were randomly selected,anesthetized and killed,and liver tissues were taken.The ultrastructures of the liver were observed by electron microscopy,the expression of IGF-1 protein was detected by Western blotting and immunohistochemistry,the expression of IGF-1 mRNA was detected by real-time PCR,and the modification of IGF-1 histone was detected by chromatin immunoprecipitation(ChIP).Results:Under electron microscope,there were a few fat droplets in liver cells of hypoxia group.The expression of IGF-1 mRNA and protein in hypoxia group was significantly lower than that in control group.ChIP results showed that the acetylation modification level of histone at the H3 k9 ac site Proximal 3’UTR,Exon 5 and Distal 3’UTR fragments of IGF-1 gene in hypoxia group were significantly lower than those in control group.Conclusion:CIH can change the level of histone acetylation of IGF-1 gene in the liver of hypoxia group,and participate in the development of nonalcoholic fatty liver in male rats.