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：
9751852
负责人：
Srinivasan Dasarathy
金额：
$ 57.59万
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/9751852
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，由于肝尿素发生受损和 Portosystemic分类。肌肉减少症或骨骼肌质量的损失是肝硬化和门移植中的高症血症。尽管几乎普遍地认识肌肉减少症的患病率和不良临床后果，没有有效的疗法，因为肝硬化中肌肉丧失的机制尚不清楚。由于蛋白质稳态或蛋白结构的失调，蛋白质合成受损并通过蛋白质水解增加自噬。通过激活综合应力反应来实现细胞应激期间蛋白质稳态（ISR）通过激活转录因子4响应EIF2α磷酸化4。氨是细胞在氨基酸分解代谢，纯代谢和肠道合成过程中产生的应激源。我们在骨骼肌中确定了独特的细胞应力反应，我们称为高肌压力反应（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，通用对照不压压2（GCN2），该2（GCN2）被L-逆转亮氨酸补充。这些扰动类似于氨基酸缺乏响应目的地增加高氨血症期间细胞L-达氨酸浓度。有趣的是，我们还观察到只有一个在HOSR期间激活了未折叠蛋白反应（UPR）的3个成分IRE1α。有趣的是， UPR的其他两个四肢：PERK，是赤班网（ER）应力和ATF6的经典介体在hasr期间未激活。与EIF2α磷酸化的细胞应激反应不同，该综合压力反应与诱导ATF4及其支持翻译恢复的目标也不是在hasr期间观察到。这些观察结果表明，HASR具有氨基酸的某些特征缺陷响应（无缺乏）和UPR的某些功能。我们的初步和发布的数据建议浓度和时间依赖于时间的初始自适应，该自适应发展为不良适应阶段骨骼肌会导致肌肉减少症。我们假设HASR响应于高氨血症，涉及反映蛋白质合成并诱导A的GCN2/MTORC1轴通过氨基酸转运蛋白的氨基酸摄取和蛋白质癌变症的增加的自适应反应 SLC7A5。我们还假设在HASR期间，仅自噬增加了IRE1α/XBP1S 和通过RIDD（调节IRE1α依赖性衰减）的mRNA降解。 Hasr和可以在肌管中增加受保护适应高症的干预措施将在A中研究多余血症的细胞和啮齿动物模型以及人类骨骼肌肉的全面阵列三个特定目的的cirhotics。在每个目标中，都将测试特定的分子热干预快速临床翻译的潜力逆转并有可能预防肝病中的肌肉减少症。