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  • Title: Differential cell death regulation between adult-unloaded and aged rat soleus muscle.
    Author: Ogata T, Machida S, Oishi Y, Higuchi M, Muraoka I.
    Journal: Mech Ageing Dev; 2009 May; 130(5):328-36. PubMed ID: 19428451.
    Abstract:
    Sarcopenia is characterized by increased regenerating myofibres and decreased myofibre size. Sarcopenia progression might be partially regulated by ageing-related signals associated with necrotic fibre disruption and nuclear apoptosis. This study sought to identify ageing-related signals in aged atrophying skeletal muscle by comparison with unloaded muscle atrophy in adults. Adult (6-month) and old (32-month) rats were used. Some adult rats were subjected to 2 weeks of hindlimb unloading (6-month-HU). Histological analysis found that regenerating fibres increased by about 30-fold only in 32-month aged soleus muscle compared with 6-month rats. The number of apoptotic DNA fragmented nuclei was increased by 3.9-fold in 6-month-HU and 2.8-fold in 32-month rats. Cleaved caspase-3 was observed at high levels on basal membranes and in nuclei in 32-month rats. By Western blot analysis additional ageing-related signals could be identified since (1) phosphorylated Bcl-2 content was increased in both cytosolic and mitochondrial fractions; (2) ER stress signal proteins caspase-12, CHOP/GADD153, and GRP78 were increased; and (3) stress-inducible chaperone HSP70 was decreased in soleus muscle from 32-month but not changed in 6-month-HU rats. We conclude that activation of ageing-related signals may mediate necrotic myofibre disruption and nuclear apoptosis induction that contribute to progression of sarcopenia.
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