Alterations in FoxO3a, NF-κB, and MuRF1 Expression in the Soleus Muscle of Male Rats Following High-Intensity Interval Training and Detraining.

Activation of the transcription factors FoxO3a and NF-κB is necessary for muscle atrophy, which occurs during cancer cachexia and detraining. It is not known how high-intensity interval training (HIIT) and detraining affect activation of these pathways. Two-month-old male Sprague-Dawley rats were assigned to sedentary control (SC) (n = 6) and HIIT (HIIT) (n = 18) groups. The HIIT group was divided into three subgroups: HIIT (n = 6), HIIT + 7-day detraining (n = 6), and HIIT + 14-day detraining (n = 6). The expression of FoxO3a, NF-κB, MuRF1, and PGC-1α in the soleus muscle was examined by RT-PCR using CYBR Green. The 2-Ct, Livak method was used to calculate the changes in data expression. The soleus muscle mass increased after HIIT (35.10%) and decreased after 7- and 14-day of detraining (15 and 21%, respectively). The mRNA expression levels of NF-κB, MuRF1, and PGC1α in the soleus muscle were upregulated, and FoxO3a levels were significantly lower in the HIIT group compare to the SC group (p = 0.001). Taken together, the activity of the FoxO3a/MuRF1 pathway, but not NF-κB /MuRF1, can promote atrophy due to detraining, and MuRF1 is not always a good marker of atrophy.