AMP-activated protein kinase contributes to myofibrillar protein hydrolysis in bovine skeletal muscle through postmortem mitochondrial dysfunction-induced apoptosis.

This study aimed to verify the role of AMP-activated protein kinase (AMPK) in mitochondrial dysfunction-induced apoptosis and postmortem bovine muscle tenderization. AMPK phosphorylation levels, mitochondrial dysfunction, mitochondrial apoptotic factors, and myofibrillar protein hydrolysis were assessed in the control group and Compound C (AMPK inhibitor) group over a 168 hr aging period. Compared with the Compound C group, the control group had an extremely significantly increased AMPK activity at 6-120 hr (p < .01) and a 62.3% and 42.1% higher mitochondrial Bax/Bcl-2 ratio at 6 and 12 hr, respectively (p < .05). Moreover, the control group had a significantly or extremely significantly higher mitochondrial dysfunction and cytoplasmic cytochrome c content at 6-72 and 12-72 hr, respectively (p < .05, p < .01); a 23.2%, 26.5%, and 26.1% increased caspase-3 expression levels at 12, 24, and 72 hr, respectively (p < .05); a significantly higher proportion of apoptotic nuclei at 24-168 hr (p < .05); and a 30.8%, 35.8%, 43.9%, and 39.5% increased production of 45-, 38-, 36-, 30-, and 28-kDa proteins at 168 hr, respectively (p < .05). Taken together, these results suggested that activated AMPK promoted mitochondrial apoptosis and bovine muscle tenderization during postmortem aging by increasing the Bax/Bcl-2 ratio on the mitochondrial membrane. PRACTICAL APPLICATIONS: Based on consumer preference, chilled fresh meat is gradually becoming the future trend of the meat industry. Poorly tenderized beef often affects consumers' desire to make secondary purchases and leads to large losses to the meat industry. Therefore, AMP-activated protein kinase, which regulates postmortem mitochondrial apoptosis and bovine muscle tenderization, is a valid research target.