In mice that have survived sepsis, mitochondria (round structures) embedded in muscles tissue show signs of damage. Image credit: Owen et al. (CC BY 4.0)
Sepsis is a life-threatening condition that occurs when a local infection spreads to the bloodstream and the body responds in such an exaggerated way that organs become damaged. Patients often require longs stays in intensive care units, and upon discharge experience chronic physical weakness and fatigue for several years. However, it was difficult to understand how sepsis can create these long-term problems because there was no way to study these issues in animals.
To fill this knowledge gap, Owen et al. developed a protocol where they triggered sepsis in adult mice and then used therapeutic treatments similar to the ones found in intensive care units; as a result, most of the animals survived, with many then exhibiting chronic muscle weakness. Further observations in surviving mice revealed that muscle mass recovered after sepsis, so this weakness was not due to a drop in muscle mass: instead, the quality of the muscle fibers had worsened. More specifically, there were striking abnormalities in mitochondria, structures whose role is to power cells. The muscles also showed signs of persistent oxidative damage, a process in which toxic molecules produced by life processes accumulate and end up harming cells.
Overall, these data suggest that reduced muscle quality contributes to chronic weakness after sepsis. While current programs for sepsis survivors aim to increase muscle quantity, the results by Owen et al. suggest that improving muscle quality, for example using antioxidant therapies, could be a new avenue of treatment.
