Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2011
Publication Date: 10/13/2011
Citation: Kemp, C.M., Wheeler, T.L. 2012. Effects of manipulation of the caspase system on myofibrillar protein degradation in vitro. Journal of Animal Science. 89(10)3262-3271. Interpretive Summary: Degradation of key proteins improves meat tenderness during postmortem refrigerated storage. The degradation has been shown to be caused primarily by the calpain enzyme system. Recent evidence indicates the caspase enzyme system also may have a role in the tenderization process. This experiment utilized normal and callipyge lamb to evaluate whether postmortem degradation could be manipulated through activation and inhibition of the caspase system. Results showed that activation of caspases increased degradation of meat proteins, while inhibition of caspases decreased degradation. These data provide additional evidence that caspases could be involved in meat tenderization.
Technical Abstract: Apoptosis via the intrinsic caspase 9 pathway can be induced by oxidative stressors hydrogen peroxide (H2O2) and N-(4 hydroxyphenol) rentinamide (fenretinide), a synthetic retinoid. Accelerated muscle atrophy and proteolysis in muscle wasting conditions has been linked to oxidative stress and activated protease systems. Therefore, the hypothesis of this study was that proteolysis of myofibrillar proteins could be manipulated through the induction or inhibition of the caspase system. After slaughter, LM and supraspinatus muscles from callipyge (n = 5) and normal (n = 3) lambs were excised, finely diced, and incubated with treatment buffers containing oxidative stressors fenretinide or H2O2, recombinant caspase 3 (rC3), caspase specific inhibitor N-acetyl–Asp–Glu–Val–Asp–CHO (DEVD), or control solution. Muscle samples were incubated for 1, 2, 7, and 21 d at 4°C. Activation of the initiator caspase, caspase 9, and myofibrillar protein degradation was determined by SDS-PAGE and Western blotting. Results showed that fenretinide, H2O2, and rC3 increased (P < 0.05) proteolysis of myofibril proteins, whilst DEVD inhibited degradation (P < 0.05). Proteolysis of myofibrillar proteins increased with incubation time (P < 0.0001) and incubation time x treatment interactions (P < 0.05) indicated that the treatment effects did not all occur at the same rate. This study has shown that manipulation of the caspase system through either induction or inhibition of activity can affect degradation of myofibrillar proteins. However, these stimulated changes were not sufficient to overcome the lack of proteolysis and tenderization that is characteristic of muscle from callipyge lambs.