血管紧张素II受体在孕期肥胖影响子代心功能中的作用及机制

Obesity is the significant risk factor for developing cardiovascular diseases. The prevalence of obesity during pregnancy in China is rapidly increasing. Previous studies have shown association between intrauterine environment and cardiovascular diseases later in life. However, the relationship between maternal obesity and increased risk of cardiovascular diseases in offspring remains unclear. Angiotensin II plays a fundamental role in the regulation of cardiovascular homeostasis and has been implicated in fetal programming of adult heart diseases. Our previous studies have shown that angiotensin II receptor (ATR) plays an important role in maternal hypoxia-induced cardiovascular dysfunction in adult offspring. In addition, our preliminary results suggest that maternal obesity alters protein abundance of ATR in the fetal heart. Therefore, our project will utilize fetal and adult (male and female) offspring from pregnant control and obese rat to test the effect of maternal obesity on cardiac ATR expression and delineate the underlying regulatory mechanisms using a molecular base approach (i.e. Quantitative methylation-specific PCR, EMSA, ChIP). Moreover, we will examine the effect of maternal obesity on cardiac function in offspring and the role of ATR using Langendorff assay (functional test of heart susceptibility to ischemia-reperfusion injury), echocardiography and molecular approach. The project will provide new insight as to the role of maternal obesity in the development of cardiovascular diseases by elucidating novel pathways that may represent therapeutic targets to prevent and treat cardiac dysfunction. Finally, our study will provide a theoretical basis for a balanced diet during pregnancy and its benefits in reducing the risk of chronic diseases later in life.

肥胖是心血管疾病的重要危险因素，肥胖问题在育龄妇女中也日渐突出。目前认为母体子宫内环境与其子代的心血管疾病发生有重要关系。然而孕期肥胖与子代心血管疾病的内在联系尚不明确。申请者在前期研究中发现血管紧张素II受体（ATR）与孕期缺氧导致子代心血管功能异常有重要关系；预实验也显示孕期肥胖改变胎鼠心脏ATR的表达。故本项目采用肥胖孕鼠的胎儿、子代成年雄性及雌性大鼠为研究对象，运用Langendorff、超声心动图、定量甲基化特异性PCR、EMSA、ChIP等实验方法研究孕期肥胖对子代心脏ATR表达的影响及调控机制；对子代心功能的直接影响；对子代在心肌缺血再灌注损伤中心功能的影响；及ATR所起的作用。本研究将为孕期肥胖引起的心功能异常的防治提供新的机制及依据，也为指导孕期合理饮食、预防子代慢性病的发生提供理论依据。

肥胖是心血管疾病的重要危险因素，与糖尿病、高血脂、高血压、冠心病等疾病的发病密切相关，目前已成为当今的医学难题。肥胖问题在育龄妇女中也日渐突出。流行病学及动物研究均显示子宫内不良环境导致子代心血管疾病患病率增加。孕期肥胖就是其中的一项重要因素。该研究检测孕期肥胖对子代心功能影响及机制。Sprague-Dawley孕鼠随机分为肥胖组和对照组, 对照组在孕期给予正常饮食，肥胖组雌鼠在孕期的第1天到第20 天持续予以高脂肪含量的饮食（国际配方D12492）。孕期肥胖增加胎鼠心脏体重的比值、子代成年雄性大鼠心脏及心脏体重比值。 肥胖组胎鼠心脏血管紧张素II受体类型1（AT1aR） mRNA水平明显降低，AT1bR则没有改变；血管紧张素II受体类型2 （AT2R）mRNA水平显著升高。孕期肥胖减少AT1R蛋白水平，却增加 AT2R蛋白水平。与对照组相比，肥胖组胎鼠心脏糖皮质激素受体（GR）总蛋白、核蛋白均显著降低，GR mRNA水平也明显减少。另外， ChIP结果显示孕期肥胖降低AT1R和AT2R启动子上糖皮质激素受体反应元件（GRE）与GR的结合力，从而导致AT1R蛋白的表达减少，而AT2R蛋白的表达增多。电镜显示肥胖组胎鼠肌原纤维排列紊乱，线粒体肿胀，线粒体嵴部分消失，线粒体呈空泡化，胞浆糖原颗粒急剧减少，呈胞质空泡化。孕期肥胖减少子代胎鼠心肌细胞增殖。孕期肥胖增加子代雄性非雌性成年大鼠血清中血管紧张素II的含量。孕期肥胖增加子代成年雄性而非雌性大鼠心肌AT2R表达，对AT1R没有影响。与对照组相比，肥胖组雄性子代大鼠心脏GR总蛋白和核蛋白均显著降低。ChIP结果显示孕期肥胖明显降低子代雄性大鼠心脏AT2R启动子上 GRE与GR的结合，从而导致AT2R蛋白表达减少。孕期肥胖导致子代雄性而非雌性大鼠心肌肥大，但未影响心脏的收缩及舒张功能。孕期肥胖增加子代雄性而非雌性大鼠心脏对缺血再灌损伤敏感性，其机制与肥胖组雄性大鼠心肌AT2R表达增加有关。因此，我们的研究为血管紧张素II受体在心血管疾病的胎儿程序化中的重要性提供了重要的依据，并显示其潜在的治疗意义。该研究有助于寻求较合理的早期干预措施，也有利于指导高危人群控制心血管疾病的其他危险因素，减少和预防心肌缺血、心肌重构及相关疾病的发生。