The effect of acute prolonged swimming on skeletal muscle metabolism in different muscle types of rats after nine days of dexamethasone treatment
Damian Józef Flis, Bartosz Cedro, Alicja Piekarska, Andżelika Borkowska, Małgorzata Hałoń, Ewa Aleksandra Rodziewicz-Flis et al. · Frontiers in Physiology · 2026
Objectives: The study investigated the effec of dexamethasone (Dex) treatment, acute prolonged swimming, and their combination on skeletal muscle mass, oxidative stress, iron metabolism, and AKT-mediated signaling in two muscle types.
Methods: Rats were divided into four groups (n=8 per group): intraperitoneal saline or Dex (1mg/kg/day) treatment for 9 days (non-exercised and exercised). Animals in exercise groups underwent a 4-day preparatory swimming procedure followed by a single 3h swimming session. The soleus (SOL) and extensor digitorum longus (EDL) muscles were collected, weighed, and used for analysis. We assessed lipid and protein peroxidation markers, catalase activity, iron-metabolism proteins, and AKT-dependent proteolysis and synthesis pathways.
Results: Nine days of Dex treatment significantly reduced SOL (-12%, p<0.01) and EDL (-15%, p<0.001) mass, accompanied by oxidative stress (increased protein peroxidation, p<0.001) and alterations in iron metabolism: increased FH (SOL: +88%, p<0.01, EDL: +80%, p<0.01) and decreased PCBP1 (SOL: -59%, p<0.001, EDL: -33%, p<0.05). 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.
Conclusion: 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.