Mitochondrial apoptosis and proteolytic changes of myofibrillar proteins in two different pork muscles during aging

This study aims to investigate the changes in mitochondrial apoptotic factors and proteolysis of two porcine muscles (psoas major - PM and longissimus dorsi - LD) during aging. Results found that during 2-168 h postmortem mitochondrial membrane permeability, mitochondrial lipid peroxidation, Ca²⁺ levels were increased, while the reduction level and abundance of cytochrome c were decreased (P < 0.05) in both muscle types. Furthermore, the activation of caspase-3 along with increases in troponin-T and desmin degradation, and μ-calpain autolysis were found (P < 0.05), regardless of muscle type. PM maintained higher mitochondrial apoptotic factors, but had more intact desmin, less troponin-T degradation and less extent of autolyzed products of μ-calpain compared to LD (P < 0.05). These results indicate that the rapid onset of mitochondrial apoptosis of PM would not lead to a subsequent impact on myofibrillar protein degradation, suggesting that the mitochondrial apoptosis mediated tenderization process could be muscle-specific.