Mechanisms of HIF1 alpha mediated dysregulated skeletal muscle proteostasis in alcoholic liver disease

酒精使用障碍和随之而来的组织损伤的患病率，主要是酒精性肝病（ALD） 继续增加。骨骼肌丢失或肌肉减少症是ALD患者的一贯异常， 与不良临床结局相关，包括死亡率增加，肝病的其他并发症 以及肝脏移植后的不良结果。我们最近报道了更严重的肌肉损失和更大的 酒精性肝硬化患者与其他原因肝硬化患者相比的肌肉损失率。尽管 ALD中肌肉减少症的高度临床意义，没有有效的治疗选择， 根本的机制还不清楚。我们还报告说，乙醇，直接和间接通过 受损的肝氨处理和随后的高氨血症，导致肌肉减少表型， 蛋白质稳态失调（Proteostasis）。在初步研究中，我们发现线粒体 对乙醇和高氨血症的反应性功能障碍。我们还注意到，乙醇会导致细胞增殖， 三羧酸（TCA）循环中间体的损失，特别是HIF 1 α抑制剂α-酮戊二酸（αKG）。 一致的、无偏倚的方法（转座酶可及染色质测序测定）， 实验表明，肌肉缺氧诱导因子-1 α（HIF 1 α）的氧非依赖性稳定， 氨在初步研究中，我们观察到HIF 1 α的转录靶点REDD 1的表达增加， 和雷帕霉素复合物1的哺乳动物靶蛋白（mTORC 1）的负调节因子，其维持骨骼肌 肌肉蛋白质稳态与功能反应。我们还注意到， 肌肉特异性缺失HIF 1 α小鼠高氨血症这些观察形成了我们的基础。 乙醇诱导高氨血症导致αKG分解与氧非依赖假说 稳定性和蛋白质稳态受损以及肌肉减少症。我们将通过测试乙醇是否 稳定骨骼肌中的HIF 1 α，并确定肌肉HIF 1 α的稳定机制。乙醇 在肌管中的体外治疗和在具有HIF 1 α及其调节功能的丧失和获得的小鼠中的体内治疗 我们还将测试代谢扰动如何调节HIF 1 α 稳定和随后的分子和功能反应。密钥验证 将在我们生物库的人类肌肉组织中进行观察。拟议的研究将加强 为进一步了解ALD患者肌肉减少症的发病机制和靶向治疗奠定基础。 该奖项将为申请人提供支持和时间，以监督研究职业发展， 翻译研究申请人与NIAAA资助的北方俄亥俄州独立调查人员合作 酒精中心和她的导师开发了肝脏疾病中的肌肉减少症领域。制度环境 高度支持她的职业道路，成为一名独立的医生科学家， 机械方法，以解决酒精使用障碍患者未满足的临床需求。

The prevalence of alcohol use disorders and consequent tissue injury, primarily alcoholic liver disease (ALD) continue to increase. Skeletal muscle loss or sarcopenia is a consistent abnormality in patients with ALD and is associated with adverse clinical outcomes that include increased mortality, other complications of liver disease and poor post-liver transplant outcomes. We have recently reported more severe muscle loss and a greater rate of muscle loss in patients with alcoholic cirrhosis compared with those in other causes of cirrhosis. Despite the high clinical significance of sarcopenia in ALD there are no effective therapeutic options because the underlying mechanisms are not well understood. We also reported that ethanol, directly and indirectly via impaired hepatic ammonia disposal and consequent hyperammonemia, results in a sarcopenic phenotype with dysregulated protein homeostasis (proteostasis). In preliminary studies, we have shown mitochondrial dysfunction in response to ethanol and hyperammonemia. We also noted that ethanol results in cataplerosis or loss of tricarboxylic acid (TCA) cycle intermediates, specifically α-ketoglutarate (αKG) an inhibitor of HIF1α. Consistently, unbiased approaches (assay for transposase accessible chromatin sequencing), and targeted experiments showed oxygen independent stabilization of muscle hypoxia inducible factor-1α (HIF1α) with ammonia. In pilot studies, we observed an increased expression of REDD1, a transcriptional target of HIF1α and a negative regulator of the mammalian target of rapamycin complex 1 (mTORC1) that maintains skeletal muscle proteostasis with functional responses. We also noted relative preservation of muscle mass during hyperammonemia in muscle specific deletion of HIF1α mice. These observations formed the basis for our hypothesis that ethanol induced hyperammonemia causes cataplerosis of αKG with oxygen independent stabilization and impaired proteostasis and sarcopenia. We will test this hypothesis by testing if ethanol stabilizes HIF1α in skeletal muscle, and determine the mechanisms of stabilization of muscle HIF1α. Ethanol treatment in vitro in myotubes and in vivo in mice with loss and gain of function of HIF1α and its regulatory molecules will be used for these studies We will also test how metabolic perturbations regulate HIF1α stabilization and consequent molecular and functional responses in our preclinical models. Validation of key observations will be done in human muscle tissue from our biorepository. The proposed studies will enhance our understanding of the mechanisms of sarcopenia in ALD and lay the foundation for targeted therapeutics. This award will provide the support and time for the applicant for a supervised research career development in translational research. The applicant works with NIAAA funded independent investigators in the Northern Ohio Alcohol Center and her mentor developed the field of sarcopenia in liver disease. The institutional environment is highly supportive of her career path towards becoming an independent physician scientist focusing on mechanistic approaches to address unmet clinical needs in patients with alcohol use disorders.