Sarcopenia in cirrhosis is mediated by a hyperammonemic stress response

肝硬化中的肌肉减少症是由高氨血症应激反应介导的

基本信息

批准号：
9976523
负责人：
Srinivasan Dasarathy
金额：
$ 57.95万
依托单位：
CLEVELAND CLINIC LERNER COM-CWRU
依托单位国家：
美国
项目类别：
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-01 至 2022-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9976523
关键词：
ATF6 gene Abbreviations Acids Amino Acid Transporter Amino Acids Amino Acyl-tRNA Synthetases Ammonia Autophagocytosis Binding Proteins Biochemical Branched-Chain Amino Acids CCL21 gene Caliber Catabolism Cell model Cellular Stress Cellular Stress Response Characteristics Cirrhosis Clinical Complex Complication DNA Damage Data Diamines Edetic Acid Embryo Endoplasmic Reticulum Endoplasmic Reticulum Degradation Pathway Enzymes Equilibrium Ethylenes Eukaryotic Initiation Factor-2 Event Experimental Models Exposure to FRAP1 gene Feedback Fibroblasts Foundations Genetic Transcription Glutamate-Ammonia Ligase Glutamine Green Fluorescent Proteins Growth Homologous Gene Human Hyperammonemia Impairment Inositol Intervention Leucine Limb structure Link Liver diseases MAPK8 gene Magnetic Resonance Imaging Mass Fragmentography Mediating Mediator of activation protein Molecular Mus Muscle Muscle Fibers Muscular Atrophy Outcome Pathway interactions Patients Phase Phenylalanine Phosphorylation Phosphotransferases Physiological Plasma Polymerase Chain Reaction Prevalence Protein Biosynthesis Protein Kinase Protein Synthesis Inhibition Protein phosphatase Proteins Proteolysis Publishing RNA RNA Splicing Recovery Rodent Model Signal Pathway Signal Transduction Skeletal Muscle Supplementation Surgical Portacaval Shunt Surgical Portosystemic Shunt Testing Thapsigargin Therapeutic Therapeutic Intervention Time Tissues Transfer RNA Translation Initiation Tunicamycin Variant activating transcription factor activating transcription factor 4 adaptive intervention ammonium acetate biological adaptation to stress clinical translation effective therapy endoplasmic reticulum stress experimental study extracellular gain of function hepatic ureagenesis in vivo inhibitor/antagonist mRNA Transcript Degradation mouse model muscle form new therapeutic target novel prevent proteostasis purine metabolism response sarcopenia sensor skeletal muscle wasting small molecule inhibitor solute stressor targeted treatment therapeutic target transcription factor CHOP uptake

项目摘要

ABSTRACT In cirrhosis, hyperammonemia is a consistent abnormality due to impaired hepatic ureagenesis and portosystemic shunting. Sarcopenia or loss of skeletal muscle mass is a major complication of hyperammonemia in cirrhosis and portosystemic shunting. Despite nearly universal recognition of the prevalence and adverse clinical consequences of sarcopenia, there are no effective therapies because the mechanisms of muscle loss in cirrhosis are not well understood. Loss of muscle mass occurs due to dysregulated protein homeostasis or proteostasis with impaired protein synthesis and increased proteolysis by autophagy. Protein homeostasis during cellular stress is achieved by activating an integrated stress response (ISR) in response to eIF2α phosphorylation via the activating transcription factor 4. Ammonia is a cellular stressor that is generated during amino acid catabolism, purine metabolism and synthesis in the gut. We identified a unique cellular stress response in the skeletal muscle that we have termed the hyperammonemic stress response (HASR). During HASR, we observed an increased phosphorylation and activation of the eIF2α kinase and amino acid deficiency sensor, general control nonderepressed 2 (GCN2) that is reversed by L- leucine supplementation. These perturbations resemble an amino acid deficiency response despite increased cellular L-leucine concentrations during hyperammonemia. Interestingly, we also observed that only one of the 3 components of the unfolded protein response (UPR), IRE1α, is activated during HASR. Interestingly, the other 2 limbs of the UPR: PERK, the classical mediator of Endoplasmic Reticulum (ER) stress and ATF6 were not activated during HASR. Unlike the cellular stress responses with eIF2α phosphorylation, the integrated stress response with induction of ATF4 and its targets that support translational recovery were also not observed during HASR. These observations show that HASR shares some characteristics of amino acid deficiency response (without deficiency) and some features of the UPR. Our preliminary and published data suggest a concentration and time dependent initial adaptive that progresses to a maladaptive phase in the skeletal muscle results in sarcopenia. We hypothesized that HASR is activated in response to hyperammonemia and involves a GCN2/mTORC1 axis that represses protein synthesis and induces an adaptive response of increased amino acid uptake and proteostasis control via the amino acid transporter SLC7A5. We also hypothesize that during HASR, only the IRE1α/XBP1s is activated with increased autophagy and mRNA degradation via RIDD (Regulated IRE1α dependent decay). The mechanisms of HASR and interventions that can increase protective adaptations to hyperammonemia in myotubes will be studied in a comprehensive array of cellular and rodent models of hyperammonemia and in the skeletal muscle of human cirrhotics in 3 specific aims. In each aim, a specific molecular therapeutic intervention will be tested with the potential for rapid clinical translation to reverse and potentially prevent sarcopenia in liver disease.

抽象的在肝硬化中，高氨血症是由于肝脏尿素生成受损而导致的持续异常。门体分流是肌肉减少症或骨骼肌质量损失的主要并发症。尽管几乎普遍认识到肝硬化和门体分流中的高氨血症。肌肉减少症的患病率和不良临床后果，目前尚无有效的治疗方法，因为肝硬化中肌肉损失的机制尚不清楚。蛋白质稳态失调或蛋白质稳态失调，蛋白质合成受损，蛋白质水解增加细胞应激期间的蛋白质稳态是通过激活整合的应激反应来实现的。 (ISR) 通过激活转录因子 4 响应 eIF2α 磷酸化。氨是一种细胞因子肠道内氨基酸分解代谢、嘌呤代谢和合成过程中产生的应激源。确定了骨骼肌中独特的细胞应激反应，我们称之为高氨血症应激反应 (HASR) 在 HASR 期间，我们观察到 eIF2α 的磷酸化和激活增加。激酶和氨基酸缺乏传感器，一般控制非去抑制 2 (GCN2)，可被 L- 逆转尽管亮氨酸补充增加，但这些扰动类似于氨基酸缺乏反应。高氨血症期间细胞L-亮氨酸浓度。未折叠蛋白反应 (UPR) 的 3 个组成部分 IRE1α 在 HASR 期间被激活。 UPR 的其他 2 个分支：PERK，内质网 (ER) 应激的经典介质和 ATF6 与 eIF2α 磷酸化的细胞应激反应不同，整合的诱导 ATF4 及其支持转化恢复的靶标的应激反应也没有 HASR 期间观察到的这些观察结果表明 HASR 具有氨基酸的一些特征。缺陷反应（无缺陷）以及普遍定期审议的一些特征。表明浓度和时间依赖的初始适应，进展到适应不良阶段我们发现 HASR 会因骨骼肌减少而被激活。高氨血症涉及 GCN2/mTORC1 轴，抑制蛋白质合成并诱导通过氨基酸转运蛋白增加氨基酸摄取和蛋白质稳态控制的适应性反应我们还发现，在 HASR 过程中，只有 IRE1α/XBP1s 被激活，自噬增加。以及通过 RIDD（受调节的 IRE1α 依赖性衰减）进行的 mRNA 降解 HASR 和的机制。将在一个项目中研究可以增强肌管对高氨血症的保护性适应的干预措施全面的高氨血症细胞和啮齿动物模型以及人类骨骼肌模型肝硬化的 3 个具体目标在每个目标中，将测试特定的分子治疗干预措施。具有快速临床转化逆转并可能预防肝脏疾病中肌肉减少症的潜力。