Mechanisms for Fetal Hepatic Programming during Intrauterine Growth Restriction

描述（由申请人提供）：越来越多的人类和动物实验证据支持宫内生长受限（IUGR）导致晚年易患代谢性疾病的概念。根据这一概念，胎儿适应了永久改变组织和器官功能的刺激或伤害，导致对肥胖和糖尿病等成人代谢疾病的易感性增加。在许多IUGR的动物模型中，关键的致孕基因（如PEPCK）的表达在胎儿发育期间被诱导。PEPCK基因表达的增加沿着肝葡萄糖产生（HGP）的增加似乎持续到成年期，并且是糖尿病和胰岛素抵抗的标志。胎儿中这种疾病起源的分子机制在很大程度上是未知的。这项建议的长期目标是了解胎儿肝脏胰岛素抵抗的起源和未能在分子水平上调节HGP。我们打算在我们的IUGR绵羊模型中通过体内和体外研究来实现这一目标。我们发表的数据表明，HGP和PEPCK基因表达显着上调出生前IUGR胎儿。我们的初步数据还表明，SIRT 1脱乙酰基酶和其促凋亡靶点PGC 1-α在IUGR胎肝中上调。这些因素表明，一个潜在的新的分子机制，可能是负责慢性诱导PEPCK和HGP在IUGR。我们将调查的假设，上调SIRT 1和PGC 1-α发挥了重要的调节作用，在降低胰岛素和葡萄糖抑制HGP在IUGR胎儿的能力，使用体内示踪方法结合胰岛素信号转导试验。我们还将使用从IUGR胎儿制备的分离的肝细胞来确定在细胞核水平上肝葡萄糖产生和PEPCK启动子的激素控制。最后，我们将研究PEPCK基因和周围染色质的表观遗传修饰是否可以解释IUGR期间基因表达的变化。在我们完善的IUGR模型中使用这种体内和体外技术的组合，我们将更好地理解，特别是在分子水平上，早期调控途径，关键转录因子和表观遗传机制参与胎儿编程以后的生活胰岛素抵抗和HGP。这些调查的结果将产生重要的，新的概念，有关的潜在胎儿机制负责增加成人代谢疾病，特别是糖尿病的易感性。这项研究还将用于帮助制定策略，以预防经历IUGR的个体发生糖尿病和代谢疾病。

DESCRIPTION (provided by applicant): Increasing human and animal experimental evidence supports the concept that intrauterine growth restriction (IUGR) results in susceptibility to metabolic disease in later life. According to this concept, the fetus adapts to a stimulus or insult that permanently alters tissue and organ function, leading to increased susceptibility to adult metabolic diseases such as obesity and diabetes. In numerous animal models of IUGR the expression of key gluconeogenic genes, such as PEPCK, are induced during fetal development. The increase in PEPCK gene expression along with increased hepatic glucose production (HGP) appears to persist into adulthood and is a hallmark of diabetes and insulin resistance. The molecular mechanisms underlying the origin of this disorder in the fetus are largely unknown. The long-term goal of this proposal is to understand the fetal origins of hepatic insulin resistance and failure to regulate HGP at the molecular level. We intend to achieve this goal with in vivo and in vitro investigations in our sheep model of IUGR. Our published data demonstrate that HGP and PEPCK gene expression are strikingly up-regulated before birth in the IUGR fetus. Our preliminary data also show that the SIRT1 deacetylase and its gluconeogenic target PGC1-alpha are up-regulated in the IUGR fetal liver. These factors suggest a potential novel molecular mechanism that may be responsible for chronic induction of PEPCK and HGP during IUGR. We will investigate the hypothesis that up-regulation of SIRT1 and PGC1-alpha plays an important regulatory role in the reduced ability for insulin and glucose to suppress HGP in the IUGR fetus using in vivo tracer methodology combined with assays of insulin signal transduction. We also will use isolated hepatocytes prepared from the IUGR fetus to determine the hormonal control of hepatic glucose production and the PEPCK promoter at the nuclear level. Lastly, we will investigate whether epigenetic modification of the PEPCK gene and surrounding chromatin explain the changes in gene expression during IUGR. Using this combination of in vivo and in vitro techniques in our well established model of IUGR, we will better understand, particularly at the molecular level, the early regulatory pathways, key transcription factors, and epigenetic mechanisms involved in fetal programming of later life insulin resistance and HGP. The results of these investigations will generate important, novel concepts regarding the underlying fetal mechanisms responsible for increased susceptibility to adult metabolic disease, particularly diabetes. This research also will be used to help develop strategies to prevent the development of diabetes and metabolic disease in individuals that experienced IUGR.