Figure 5: Applications of muscle atrophy models: pathogenesis and treatments (IMAGE)
Caption
Muscle atrophy models are crucial for understanding disease mechanisms and developing treatments. These models are used to study various interventions, such as exercise and nutrition, drug development, and novel therapies like stem cell therapy, gut microbiota manipulation, and muscle electrical stimulation (A). Additionally, Muscle atrophy models have significantly advanced our understanding of the underlying mechanisms of muscle atrophy. During muscle atrophy, several key processes occur: i)Protein synthesis and degradation imbalance: There is an imbalance between protein synthesis and degradation. The ubiquitin-proteasome system and NF-κB activity are enhanced, leading to increased expression of proteins that promote protein degradation. ii) Inflammatory responses: Inflammatory cell infiltration and cytokine storms contribute to muscle atrophy. Myokines are disrupted, further exacerbating the inflammatory response. iii) Mitochondrial dysfunction: Oxidative stress and mitochondrial damage occur, resulting in reduced ATP synthesis. This energy deficit exacerbates muscle atrophy. iv) Impaired muscle regeneration: Muscle satellite cells and fibers exhibit functional blockages, leading to decreased CSA and reduced markers of differentiation. The neuromuscular junction loses its function, and hormonal changes inhibit protein synthesis pathways, collectively reducing muscle protein synthesis. These mechanisms collectively contribute to the progressive loss of muscle mass and function, highlighting the importance of muscle atrophy models in elucidating the complex pathophysiology of this condition (B).
ROS: reactive oxygen species. ATP: adenosine triphosphate. IL-6: interleukin-6. IL-1β: interleukin-1 beta. MuRF1: muscle RING finger protein 1. Atrogin-1: atrophy-related gene 1. NF-kB: nuclear factor kappa B. IGF-1: insulin-like growth factor 1. mTOR: mammalian target of rapamycin. IL-15: interleukin-15. HGF: hepatocyte growth factor. FGF-2: fibroblast growth factor 2. Wnt: wingless-int. Notch: notch signaling pathway. MyoD1: myogenic differentiation 1. Myf-5: myogenic factor 5. MRF4: myogenic regulatory factor 4. Myf6: myogenic factor 6. CSA: cross-sectional area.
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Chenying Fu
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