Parkin overexpression attenuates muscle atrophy and rescues mitochondrial morphology in sepsis‐induced skeletal muscle dysfunction
Authors: Leduc‐Gaudet Jean‐Philippe , Broering Felipe Eduardo , Mayaki Dominique , Hussain Sabah NA , Gouspillou Gilles 
Published: June 2021

RationaleThe accumulation of mitochondrial dysfunction is believed to contribute to skeletal muscle weakness and loss in severe sepsis. Changes in mitochondrial mitophagy, dynamics and morphology can greatly impact mitochondrial function, and vice versa. However, whether mitochondrial mitophagy, dynamics and morphology in skeletal muscle are altered in sepsis remain largely unexplored. Here, we aimed to (1) investigate the effects of sepsis on mitochondrial dynamics and morphology in skeletal muscle; and (2) evaluate the impact of parkin overexpression, a protein in charge of the removal of dysfunctional mitochondria, on muscle fiber size and mitochondrial morphology using a quantitative 2‐dimensional transmission electron microscopy approach.MethodsParkin was overexpressed for 4 weeks in the gastrocnemius (GAS) muscles of 4 week‐old mice using intramuscular injections of Adeno‐Associated Viruses (AAV). A control AAV, containing a sequence coding for the green fluorescent protein (GFP), was injected in the contralateral leg. Sepsis was induced by cecal ligation and perforation (CLP). Control (Sham) mice were subjected to the same surgery, but the cecum was neither ligated nor punctured. The impact of sepsis and Parkin overexpression on muscle myofiber size, mitochondrial morphology and gene expression were investigated.ResultsAs expected, CLP resulted in a significant decrease in body weight 48 hours after surgery. Sepsis increased the expression of MuRF1 and Atrogen‐1, suggesting increased protein degradation. In line with these findings, CLP mice displayed an increased abundance of small fibers, a clear sign of atrophy. Parkin overexpression attenuated myofiber atrophy in CLP mice and resulted in myofiber hypertrophy in Sham mice. Septic muscle displayed enlarged and more complex InterMyoFribriallar (IMF) mitochondria. Interestingly, Parkin overexpression reduced the morphological complexity of IMF mitochondria in both Sham and CLP mice. Sepsis decreased the expression of TFAM, complex II and complex IV, while Parkin‐overexpressing muscles were protected. Sepsis increased the expression and content of LC3‐II, SQSTM1 and BNIP3. Parkin overexpression did not affect the expression and content of these proteins.ConclusionsThe present study shows that sepsis alters mitochondrial morphology in skeletal muscles, an effect attenuated by Parkin overexpression. Our results also indicate that Parkin overexpression attenuates sepsis‐induced myofiber atrophy. Although further studies are required, our findings place Parkin as a potential therapeutic target to counter sepsis‐induced muscle dysfunction.Support or Funding InformationThis study is funded by CIHR grants. GG salary support is provided by a FQRS Chercheur Boursier Junior 1 Award. JPLG is supported by a CIHR Vanier Doctoral Scholarship.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.