METABOLIC HOMEOSTASIS IN LIVER REGENERATION

肝部分切除后的肝再生是为数不多的模型之一 其中可以在完整的组织中研究细胞增殖， 动物 再生是从有毒， 代谢和免疫损伤的肝脏，是重要的 肝移植尽管失去了三分之二的肝脏， 维持代谢和合成的体内平衡。 葡萄糖稳态是 通过诱导肝脏特异性即刻早期基因介导 包括那些编码促细胞生成酶如葡萄糖-6- 磷酸酶和PEPCK。这种诱导肝再生的基础 然而，这一点还没有得到很好的理解，很可能涉及到参与 包括NF-κ B和Stat 3的生长诱导转录因子。 我们 假设这些因素通过合作发挥作用， 与组成型肝脏特异性转录因子的相互作用。 C/EBP蛋白，其在整个肝再生过程中表达， 其它肝因子如HNF-1是逻辑候选转录因子 这种类型的复杂监管的因素。 C/EBPalpha 对于调节必需的立即早期基因是重要的， 葡萄糖稳态，包括葡萄糖-6-磷酸酶和PEPCK， C/EBPalpha缺陷小鼠在出生时严重低血糖， 证明了这些mRNA的正常诱导。 我们会研究 基因激活的基础，这些基因对维持 代谢稳态使用两种方法。(l)潜在靶基因 在再生过程中被C/EBPalpha激活 在C/EBPalpha缺陷杂合子小鼠中，我们假设 在C/EBPalpha的表达水平上表现出微妙的变化， 部分肝切除术后的基因变化 在确定了 作为潜在的C/EBPalpha激活靶的基因，启动子 将在组织培养系统中检测这些基因的区域， 鉴定特异性C/EBPalpha启动子元件和调节元件， 其它肝因子和生长诱导转录因子 有助于激活这些基因。 (2)康贝特人将以 C/EBP蛋白、HNF-1和生长诱导因子对肿瘤生长的影响 葡萄糖-6-磷酸酶的激活我们假设被激活的基因 在再生过程中被C/EBPalpha破坏。我们会分离并排序 启动子区，并确定重要的调控元件， 在组织培养系统中激活该基因的转录因子。 确定肝脏特异性立即早期基因激活的基础 重要的代谢稳态将提高我们的理解如何 肝脏在再生过程中保持其分化状态。 本提案中概述的研究将在 Rebecca Taub博士的赞助，他是公认的专家， 肝再生领域，其实验室将提供 为候选人的继续培训提供良好的环境， 发展成为肝病学的独立研究者。

Liver regeneration following partial hepatectomy is one of the few models in which it is possible to study cellular proliferation in the intact animal. Regeneration is an important component of recovery from toxic, metabolic, and immunologic injury to the liver and is important following liver transplantation. Despite the loss of two-thirds of the liver mass, metabolic and synthetic homeostasis is maintained. Glucose homeostasis is mediated by the induction of liver-specific immediate-early genes including those which encode gluconeogenic enzymes such as glucose-6- phosphatase and PEPCK. The basis for this induction in liver regeneration is not well understood, however, it is likely to involve the participation of growth-induced transcription factors including NF-kappaB and Stat3. We hypothesize that these factors exert their effects through cooperative interactions with constitutive liver-specific transcription factors. C/EBP proteins, which are expressed throughout liver regeneration and other hepatic factors such as HNF-l are logical candidate transcription factors for this type of complex regulation. It is likely that C/EBPalpha is important for the regulation of immediate-early genes necessary for glucose homeostasis including glucose-6-phosphatase and PEPCK since C/EBPalpha deficient mice are profoundly hypoglycemic at birth and do not demonstrate the normal induction of these mRNAs. We will examine the basis of activation of genes which are important for the maintenance of metabolic homeostasis using two approaches. (l) Potential target genes which are activated by C/EBPalpha during regeneration will be identified in C/EBPalpha deficient heterozygote mice which we hypothesize will manifest subtle changes in the level of expression of C/EBPalpha regulated genes in response to partial hepatectomy. Following identification of genes which are potential C/EBPalpha targets of activation, promoter regions of these genes will be examined in tissue culture systems to identify specific C/EBPalpha promoter elements and regulatory elements for other hepatic factors and growth-induced transcription factors which contribute to the activation of these genes. (2) We will determine the contribution of C/EBP proteins, HNF-1, and growth-induced factors to the activation of glucose-6-phosphatase a gene which we postulate is activated by C/EBPalpha during regeneration. We will isolate and sequence the promoter region and identify important regulatory elements for transcription factors which activate this gene in tissue culture systems. Defining the basis for activation of liver-specific immediate-early genes important for metabolic homeostasis will enhance our understanding of how the liver maintains its differentiated state during regeneration. The studies outlined in this proposal will be performed under the sponsorship of Dr. Rebecca Taub, who is an acknowledged expert in the field of liver regeneration and whose laboratory will provide an outstanding environment for the candidate's continued training and development as an independent investigator in hepatology.