Editorial: putting more muscle into treating our chronic hepatitis B patients-the importance of assessing sarcopenia

Editorial: Hepatitis C virus eradication improves skeletal muscle mass-Authors' reply

This article is linked to Coelho et al papers. To view these articles, visit https://doi.org/10.1111/apt.17950 and https://doi.org/10.1111/apt.17978

Sarcopenia in chronic liver diseases: a translational overview

INTRODUCTION

Sarcopenia refers to a progressive and generalized muscle mass and strength loss. In liver diseases, it has been related to worse outcomes and high risk of decompensations.

AREAS COVERED

Sarcopenia is caused by a set of cellular processes in the muscle such as denervation, mitochondrial dysfunction, endotoxemia and inflammation; which are manifested through the alteration of several proteolytic pathways such as lysosomal, proteasomal and caspase systems. In autophagy, myostatin and oxidative stress; such as hyperammonemia, contributes importantly to liver sarcopenia through loss of muscle mass already demonstrated in in vitro and in vivo models. In addition, hormones and the regulation of the intestinal microbiota, influence in a not less important magnitude. In the clinical setting, early identification of sarcopenia has been established as a mandatory item to prevent progression of muscle mass loss; however, diagnostic methods have extreme variation according to methodology, population, etiology and severity of liver disease. Reversing sarcopenia should be an integral therapeutic strategy.

EXPERT OPINION

Clinical and nutritional interventions should be adapted to liver injury etiology and stage of disease, each of them shares a similar sarcopenia development pathway. There are specific biomarkers that condition or exacerbate loss of skeletal muscle.

Influence of Methods Used to Establish Sarcopenia Cutoff Values for Skeletal Muscle Measures Using Unenhanced and Contrast-Enhanced Computed Tomography Images

BACKGROUND

Multiple cutoff values of computed tomography (CT)-based skeletal muscle measures have been proposed, but there is currently no consensus used to identify sarcopenia. We aimed to evaluate the influence of statistical methods used to establish sarcopenia cutoff values and to examine the impact of contrast enhancement on the skeletal muscle measures.

METHODS

The skeletal muscle area (SMA) and muscle radiation attenuation (MRA) of 316 healthy individuals were measured on unenhanced CT images at the third lumbar vertebra level, and the skeletal muscle index (SMI) was SMA divided by height squared. Possible cutoff values were established using 2 methods: 5^th percentile of individuals aged 20-60 years or mean - 2 × SD of individuals aged 20-50 years. The concordance was assessed using Cohen's κ coefficients and McNemar test. The skeletal muscle parameters on 3 phases from 30 CT examinations were compared.

RESULTS

The concordance between the 2 methods was almost perfect (κ coefficients: 0.830-0.849) for low MRA but slight to moderate (κ coefficients: 0.189-0.591) for low SMI, especially in the men (P < 0.01). Compared with the unenhanced images, the mean SMA, SMI, and MRA on the contrast-enhanced images increased by 0.8%-1.7%, 0.8%-1.8%, and 14.8%-21.6% (all P < 0.001), respectively, and only the changes in MRA were clinically significant.

CONCLUSIONS

The methods for establishing cutoff values and contrast enhancement influence the identification of low SMI and low MRA, respectively. Thus, the definition of sarcopenia should include the standardized method for establishing cutoff values and the phase of CT for analysis.