Effect of hypoxia on glucose metabolism in IUGR fetal liver

描述(由申请人提供)：胎盘功能不全引起的宫内发育受限妊娠(PI-IUGR)的胎儿肝脏对低氧和胎盘向胎儿的营养转移减少的代谢适应。这些适应包括糖异生的早期激活和抵抗胰岛素抑制肝脏葡萄糖的产生。这一点很重要，因为虽然这些代谢适应可能是确保胎儿存活所必需的，但它们也可能导致日后生活中的病理状况，包括2型糖尿病(T2 DM)。重要的是，PI-IUGR胎肝中代谢重编程适应的早期机制在很大程度上是未知的。我们的工作假设是，胎盘功能不全引起的低氧通过HIF和FOXO1机制诱导代谢重编程，其定义是糖酵解增加和葡萄糖氧化减少，这也导致胰岛素抑制PI-IUGR胎肝中葡萄糖的产生。这项建议的目的是通过HIF-FOXO1途径在胎羊肝细胞中产生代谢重编程和胰岛素抵抗的发展来确定缺氧的影响。为了测试这个被提出的途径，从正常和PI-IUGR胎羊分离的肝细胞将暴露在常氧和低氧条件下。将通过检测糖异生、糖酵解和葡萄糖氧化等靶基因的表达来评估低氧对代谢重编程诱导的影响。将测量有无胰岛素的葡萄糖产生率，以评估胰岛素敏感性。检测Foxo1的活化和定位，以确定低氧和胰岛素敏感性的影响。基因沉默将被用来测试FOXO1的作用。总之，这些结果将证明HIF和FOXO1之间的一种新的机制是否有助于PI-IUGR期间慢性缺氧引起的胎儿肝脏葡萄糖代谢和胰岛素抵抗的变化。这些结果将具有重大的科学和潜在的临床影响，因为IUGR影响多达6%-10%的怀孕，但尚不清楚IUGR后代如何在以后的生活中增加患代谢性疾病的风险。早期暴露于低氧之间的联系，以及 在其他营养素缺乏的情况下，PI-IUGR期间和胎儿时期肝细胞核FOXO1活性升高可能是了解PI-IUGR如何促进肝脏胰岛素抵抗和肝脏葡萄糖产生异常的发展的关键，这是T2 DM后期生活发展的基础。总体而言，这些新的R03研究结合我们的K01结果将提供一个详细的框架，描述PI-IUGR期间在子宫内发展的肝脏代谢的协调变化，并使肝脏在出生后易受代谢问题的影响。

DESCRIPTION (provided by applicant): The fetal liver in intrauterine growth restricted pregnancies caused by placental insufficiency (PI-IUGR) develops metabolic adaptations to hypoxia and decreased placenta-to-fetus nutrient transfer. These adaptations include an early activation of gluconeogenesis and resistance to insulin's suppression of hepatic glucose production. This is important because while these metabolic adaptations may be necessary to ensure fetal survival, they also can lead to pathological conditions later in life, including type diabetes (T2DM). Importantly, the early mechanisms responsible for these metabolic reprogramming adaptations in the PI-IUGR fetal liver are largely unknown. Our working hypothesis is that hypoxia from placental insufficiency induces metabolic reprogramming, defined by increased glycolysis and decreased glucose oxidation, via a HIF and FOXO1 mechanism that also results in impaired insulin suppression of glucose production in the PI-IUGR fetal liver. The goal of this proposal is to determine the effect of hypoxia via a HIF-FOXO1 pathway that produces metabolic reprogramming and development of insulin resistance in fetal sheep hepatocytes. To test this proposed pathway, isolated hepatocytes from normal and PI-IUGR fetal sheep will be exposed to normoxic and hypoxic conditions. The expression of genes in gluconeogenesis, glycolysis, and glucose oxidation and other HIF and FOXO1 target genes will be measured to assess the effect of hypoxia on the induction of metabolic reprogramming. Glucose production rates with and without insulin will be measured to assess insulin sensitivity. FOXO1 activation and localization will be measured to determine the effect of hypoxia and insulin sensitivity. Gene silencing will be used to test the role of FOXO1. Overall, these results will demonstrate whether a novel mechanism between HIF and FOXO1 contributes to changes in fetal hepatic glucose metabolism and insulin resistance resulting from chronic hypoxia during PI-IUGR. These results will have significant scientific and potential clinical impact because IUGR affects up to 6-10% of pregnancies, yet it remains unclear how IUGR offspring develop increased risk for metabolic disease in later life. A link between early exposure to hypoxia, along with other nutrient deficiencies, during PI-IUGR and increased hepatocellular nuclear FOXO1 activity during fetal life may hold the key to understanding how PI-IUGR promotes the development of hepatic insulin resistance and dysregulated hepatic glucose production, which underlie later life development of T2DM. Overall, these new R03 studies combined with our K01 results will provide a detailed framework describing the coordinated changes in hepatic metabolism that develop in utero during PI- IUGR and predispose the liver to metabolic problems after birth.