2018 Volume 64 Issue Suppl.1 Pages 93-99
Objective: The aim of this study was to determine the relationship between the mRNA expression of muscle-specific ubiquitin ligases (E3) and the degree of muscle atrophy in both slow-twitch and fast-twitch muscles, following immobilization.
Methods: Male C57BL/6 mice were subjected to cast immobilization for 0 (Control), 3, 7, 14, and 21 days. Based on the observed trends in the mRNA expression of muscle-specific E3s in our previous study, we analyzed the correlation between muscle mass (the percentage change from the control group per day) and muscle-specific E3 mRNA expression levels in the two types of muscles.
Results: In soleus muscles, MAFbx/Atrogin-1 mRNA levels correlated negatively with muscle mass in the late stage of immobilization (14 and 21 days of immobilization)(r=-0.80, p=0.03). However, this relationship was not observed in the early stage of immobilization (3 and 7 days of immobilization). MuRF1 mRNA expression levels also correlated negatively with muscle mass, but only in the late stage of immobilization (r=-0.82, p=0.02). In the plantaris muscles, these correlations were not found in both the early and late stages of immobilization.
Conclusions: These data suggest that protein degradation resulting from the effects of muscle-specific E3s may not be involved in the early stage of immobilization-induced atrophy in both muscle types, and that other proteolytic pathways are possibly responsible for the atrophy during this period.
