Duchenne muscular dystrophy progression induced by downhill running is accompanied by increased endomysial fibrosis and oxidative damage DNA in muscle of mdx mice

Running improves muscle mass by activating autophagic flux and inhibiting ubiquitination degradation in mdx mice

BACKGROUND

Exercise therapy can improve muscle mass, strengthen muscle and cardiorespiratory function, and may be an excellent adjunctive treatment option for Duchenne muscular dystrophy.

METHODS

This article investigates the effects of 10 weeks of treadmill training on skeletal muscle in control and mdx mice. Hematoxylin and eosin (H&E) staining was used to detect the morphometry of skeletal muscle; the grip strength test, suspension test, and rotarod test were used to detect limb muscle strength of mice, and Aurora Scientific Instruments were used to detect in vivo Muscle Stimulation Measuring Maximum Force of pre-fatigue and post-fatigue. The expression levels of myogenic proteins, ubiquitination markers, autophagy pathway proteins, and the proportion of different muscle fiber types were detected.

RESULTS

The experimental results show that running exercise can significantly improve the muscle mass of mdx mice, promote muscle strength, endurance, and anti-fatigue ability, reverse the pathological state of skeletal muscle destruction in mdx mice, and promote muscle regeneration. WB experiments showed that running inhibited the ubiquitination and degradation of muscle protein in mdx mice, inhibited AKT activation, decreased phosphorylated FoxO1 and FoxO3a, and restored the suppressed autophagic flux. Running enhances muscle strength and endurance by comprehensively promoting the expression of Myh1/2/4/7 fast and slow muscle fibers in mdx mice.

CONCLUSIONS

Running can inhibit the degradation of muscle protein in mdx mice, and promote the reuse and accumulation of proteins, thereby slowing down muscle loss. Running improves skeletal muscle mass by activating autophagic flux and inhibiting ubiquitination degradation in mdx mice.

Extracellular Matrix Proteomics: The mdx-4cv Mouse Diaphragm as a Surrogate for Studying Myofibrosis in Dystrophinopathy

The progressive degeneration of the skeletal musculature in Duchenne muscular dystrophy is accompanied by reactive myofibrosis, fat substitution, and chronic inflammation. Fibrotic changes and reduced tissue elasticity correlate with the loss in motor function in this X-chromosomal disorder. Thus, although dystrophinopathies are due to primary abnormalities in the DMD gene causing the almost-complete absence of the cytoskeletal Dp427-M isoform of dystrophin in voluntary muscles, the excessive accumulation of extracellular matrix proteins presents a key histopathological hallmark of muscular dystrophy. Animal model research has been instrumental in the characterization of dystrophic muscles and has contributed to a better understanding of the complex pathogenesis of dystrophinopathies, the discovery of new disease biomarkers, and the testing of novel therapeutic strategies. In this article, we review how mass-spectrometry-based proteomics can be used to study changes in key components of the endomysium, perimysium, and epimysium, such as collagens, proteoglycans, matricellular proteins, and adhesion receptors. The mdx-4cv mouse diaphragm displays severe myofibrosis, making it an ideal model system for large-scale surveys of systematic alterations in the matrisome of dystrophic fibers. Novel biomarkers of myofibrosis can now be tested for their appropriateness in the preclinical and clinical setting as diagnostic, pharmacodynamic, prognostic, and/or therapeutic monitoring indicators.