Relation between skeletal muscle strength and ubiquitin ligase expression in muscle atrophy models in zebrafish larvae (Danio Rerio)
Abstract Background Skeletal muscle atrophy is often seen in patients with chronic diseases or muscle disuse. Upregulated expression of ubiquitin ligases such as Muscle Ring Finger 1 (MuRF-1) and Muscle Atrophy F-box (MAFbx) has been shown in different immobilization-induced atrophy models, which is believed to be responsible for the enhanced muscle protein proteolysis and thereafter results in muscle weakness. However, currently used immobilization animal models can include artefacts due to difficulty of food intake and stress. Zebrafish larvae 5-6 days after hatching do not require active movement for food intake, and it is possible to assess the muscle function of their trunk muscle. Therefore, we established two muscle atrophy models using zebrafish larvae and aimed to investigate the role of the MuRFs and MAFbx in relation with muscle function.Methods An actin-myosin interaction blocker (BTS) was used to immobilize zebrafish larvae from 3-6 days after hatching; in another series, dexamethasone was fed to larvae from 3-5 days after hatching. Maximal active force of trunk muscles was examined and the distance between adjacent filaments in sarcomeric structure was measured using small angle x-ray diffraction. MuRF and MAFbx expression was determined using real time PCR. Two-way ANOVA was used to analyze the difference between groups.Results We found a significant up-regulation of MuRF-1 and a lower active force generation in dexamethasone treated larvae. However, although the BTS immobilization induced muscle weakness, it was associated with decreased of MuRF-1 to 3 and MAFbx. After 3 days of immobilization, sarcomere became more compressed compared to the controls.Conclusions Two kinds of muscle atrophy models were successfully established in zebrafish larvae. MuRFs and MAFbx was lowered in BTS treated model whereas MuRF-1 was up-regulated in dexamethasone treated model implicating the complex role of ubiquitin ligase in different muscle atrophy models.
