Peter J. Ferrandi

Electrically evoked muscle contractions conducted every other day after muscle injury caused additional damage and slowed recovery of muscle regeneration; however, mitochondria transplantation attenuated the negative regenerative effects of rehabilitative contractions on muscle fiber regeneration. This suggests that optimizing mitochondrially regulated repair may improve muscle regeneration. Furthermore, injured muscles treated by mitochondrial transplantation had lower collagen content/fibrosis than those treated with PBS after injury. Mitochondrial transplantation blunts fibrosis and improves muscle fiber repair after injury.

Recent studies have indicated a role for circulating extracellular vesicles (EVs) in the pathogenesis of multiple diseases. However, most in vitro studies have used variable and arbitrary doses of EVs rather than interpreting EVs as an existing component of standard skeletal muscle cell culture media. The current study provides an initial investigation into the effects of circulating EVs on the metabolic phenotype of C2C12 myotubes by replacing EVs from fetal bovine serum with circulating EVs from control mice or mice with obesity and type 2 diabetes (OT2D). We report that EVs associated with OT2D decrease 2‐NBDG uptake (a proxy measure of glucose uptake) in the insulin‐stimulated state compared to controls. OT2D associated EV treatment also significantly decreased myosin heavy chain type 1 (MHCI) mRNA abundance in myotubes but had no effect on mRNA expression of any other myosin heavy chain isoforms. OT2D‐associated circulating EVs also significantly increased lipid accumulation within myotubes without altering the expression of a selection of genes important for lipid entry, synthesis, or catabolism. The data indicate that, in a severely diabetic state, circulating EVs may contribute to insulin resistance and alter gene expression in myotubes in a manner consistent with the skeletal muscle phenotype observed in OT2D.