The Effect of Ex Vivo Human Serum from Liver Disease Patients on Cellular Protein Synthesis and Growth.

Sarcopenia is a common complication affecting liver disease patients, yet the underlying mechanisms remain unclear. We aimed to elucidate the cellular mechanisms that drive sarcopenia progression using an in vitro model of liver disease. C2C12 myotubes were serum and amino acid starved for 1-h and subsequently conditioned with fasted ex vivo serum from four non-cirrhotic non-alcoholic fatty liver disease patients (NAFLD), four decompensated end-stage liver disease patients (ESLD) and four age-matched healthy controls (CON) for 4- or 24-h. After 4-h C2C12 myotubes were treated with an anabolic stimulus (5 mM leucine) for 30-min. Myotube diameter was reduced following treatment with serum from ESLD compared with CON (-45%) and NAFLD (-35%; p < 0.001 for both). A reduction in maximal mitochondrial respiration (24% and 29%, respectively), coupling efficiency (~12%) and mitophagy (~13%) was identified in myotubes conditioned with NAFLD and ESLD serum compared with CON (p < 0.05 for both). Myostatin (43%, p = 0.04) and MuRF-1 (41%, p = 0.03) protein content was elevated in myotubes treated with ESLD serum compared with CON. Here we highlight a novel, experimental platform to further probe changes in circulating markers associated with liver disease that may drive sarcopenia and develop targeted therapeutic interventions.

Evaluation of the mechanisms of sarcopenia in chronic inflammatory disease: protocol for a prospective cohort study.

BACKGROUND: Several chronic inflammatory diseases co-exist with and accelerate sarcopenia (reduction in muscle strength, function and mass) and negatively impact on both morbidity and mortality. There is currently limited research on the extent of sarcopenia in such conditions, how to accurately assess it and whether there are generic or disease-specific mechanisms driving sarcopenia. Therefore, this study aims to identify potential mechanisms driving sarcopenia within chronic inflammatory disease via a multi-modal approach; in an attempt to help define potential interventions for future use. METHODS: This prospective cohort study will consist of a multi-modal assessment of sarcopenia and its underlying mechanisms. Recruitment will target three chronic inflammatory diseases: chronic liver disease (CLD) (n=50), with a subset of NAFLD (n=20), inflammatory bowel disease (IBD) (n=50) and rheumatoid arthritis (RA) (n=50) both before and after therapeutic intervention. In addition, 20 age and sex matched healthy individuals will be recruited for comparison. Participants will undergo 4 assessment visits at weeks 0, 2, 12 and 24. Visits will consist of the following assessments: blood tests, anthropometrics, functional assessment, quadriceps muscle imaging, actigraphy, quality of life questionnaires, food diary collection and muscle biopsy of the vastus lateralis (at weeks 2 and 24 only). In addition, stool and urine samples will be collected for future microbiome and metabolomics analysis. DISCUSSION: This is the first study to use a multi-modal assessment model to phenotype sarcopenia in these chronic inflammatory diseases. We hope to identify generic as well as disease-specific mechanisms driving sarcopenia. We appreciate that these cohorts do require separate standards of care treatments which limit comparison between groups. ETHICS AND DISSEMINATION: The study is approved by the Health Research Authority - West Midlands Solihull Research Ethics Service Committee Authority (REC reference: 18/WM/0167). Recruitment commenced in January 2019 and will continue until July 2021. The study was halted in March 2020 and again in January 2021 with the COVID-19 pandemic. The findings will be disseminated through peer-reviewed publications and conference presentations. All data will be stored on a secure server. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04734496.