Aerobic plus resistance exercise attenuates skeletal muscle atrophy induced by dexamethasone through the HDAC4/FoxO3a pathway

This study aimed to investigate the underlying mechanisms by which physical exercise mitigates muscle atrophy induced by Dexamethasone (Dex). A muscle atrophy model was established in the mouse C2C12 cell line and 8-week-old mice treated with Dex, with subsequent verification of phenotype and atrogene expression. The potential benefits of combined aerobic and resistance exercise in mitigating muscle atrophy were then examined. To elucidate the involvement of Histone deacetylase 4 (HDAC4) in the protective effects of exercise against muscle loss, a combination of RT-PCR, Western blotting, immunoprecipitation, and immunofluorescence staining techniques were employed. The upregulation of HDAC4 was observed following Dex-induced muscle atrophy in vitro and in vivo. Inhibition of HDAC4 in C2C12 cells resulted in an increase in myotube diameter and fusion index, along with a decrease in the expression of Atrogin-1 and MuRF1. Treatment with Tasquinimod, an HDAC4 inhibitor, effectively prevented muscle wasting and dysfunction in mice induced by Dex. After a 6-week exercise intervention, the Dex-Exercise group exhibited significant improvements in body fat level, hyperinsulinemia, muscle mass and function in comparison to the Dex-Sedentary group. Mechanistically, we discovered that HDAC4 bound to and deacetylated Forkhead box protein O 3a (FoxO3a) within the nucleus, leading to decreased phosphorylation of FoxO3a at Ser 253. This interaction subsequently facilitated the expression of downstream atrogene Atrogin-1 and MuRF1, resulting in muscle atrophy. Conversely, exercise was found to potentially mitigate muscle atrophy by inhibiting the HDAC4/FoxO3a pathway. These findings suggest that HDAC4 may be a potential therapeutic target for exercise to combat Dex-induced muscle atrophy.