Résumé
The conversion of skeletal muscle into meat, i.e. maturation, is a complex process where muscle undergoes an energetic stress leading to different biochemical and physiological changes. In agronomic field, the study of these alterations is of particular interest, in order to improve the quality of meat.It is well established that the proteolytic events generated by the enzymes such as cathepsins, calpains and ubiquitin proteasome system are involved in skeletal muscle maturation. Recent data suggest that autophagy may also contribute to the post-mortem maturation, but how this process is regulated remains currently unknown.To evaluate the autophagic process during skeletal muscle post-mortem maturation, we designed a pilot study using 6 month-old mice within a 48h post-mortem time frame. We measured the expression of proteins involved in autophagic pathway, and the autophagic flux using the colchicine (an inhibitor of autophagy). The interaction between autophagy and myostatin, a negative regulator of skeletal muscle mass, was also analyzed during this post-mortem interval. In addition, the respective contribution of proteolysis mechanisms during skeletal muscle post-mortem maturation was assessed by following the degradation of targeted myofibrillar proteins (Desmin, Troponin T) in the context of autophagic flux inhibition in wild-type (WT) and myostatin knocked-out (Mstn KO) mice.Our data showed attenuation in AMPK and ULK (inducer of autophagy) activation associated to a reduced basal autophagic flux that remained low within the postmortem time frame in Mstn KO muscle. Futhermore, post-mortem myofibrillar proteolysis was more pronounced in Mstn KO muscle and is not altered with autophagic flux inhibition compared to WT muscle.In conclusion, our results showed a difference in the proteolytic profile between the two genotypes, with the absence of myostatin promoting a reduced level of autophagy during the post-mortem maturation of skeletal muscle. Previous studies described a positive relationship between autophagy and oxidative stress. Further studies are needed in order to demonstrate how the oxidative stress regulates autophagy in the context of myostatin inhibition.