Supplementary file 3_The effect of acute prolonged swimming on skeletal muscle metabolism in different muscle types of rats after nine days of dexamethasone treatment.xlsx

Dex treatment also affected proteins involved in synthesis and proteolysis pathways: in SOL, lowered total AKT (-22%, p<0.05) and pmTOR (-24%, p<0.05); in EDL, decreased MuRF-1 (-30%, p<0.01) and total mTOR (-24%, p<0.01), highlighting mechanisms underlying muscle loss. In saline-treated rats, acute prolonged swimming, following 4 days of preparatory exercise, did not affect SOL and EDL mass or oxidative stress markers.

However, in SOL, swimming reduced PCBP1 (-43%, p<0.001), decreased total AKT (-33%, p<0.01) and pAKT (-47%, p<0.01), increased Atrogin-1 levels (+38%, p<0.001), and decreased pmTOR (-52%, p<0.001) and p70S6K levels (-47%, p<0.05). In EDL, swimming lowered MuRF-1 levels (-23%, p<0.01), indicating specific responses to exercise across muscle types. Dex-induced muscle mass loss was lower after a 4-day preparatory exercise procedure followed by prolonged exercise (p<0.001 for both muscles).

Swimming in Dex-treated rats decreased pAKT (-52%, p<0.01) in SOL and increased pmTOR (+52%, p<0.01) in EDL. </p>Conclusion<p>Dex treatment reduces skeletal muscle mass, regardless of fiber composition. These changes relate to oxidative stress and an imbalance in iron metabolism, but differences between muscle types in the proteolysis/synthesis signaling pathway highlight contrasting responses across muscle types. Acute prolonged swimming, preceded by a 4-day preparatory procedure, attenuates the adverse effects of Dex treatment.</p>