Alterations in sphingolipid synthesis during training, detraining, and retraining may alter myogenesis in skeletal muscle

The benefits of exercise on metabolic health and its effectiveness at reducing morbidity risk are well established. Exercise training enhances skeletal muscle metabolism and function, but whether such adaptations persist through detraining and how they are potentiated with retraining are not well understood. Recent evidence has highlighted the role sphingolipids play on skeletal muscle size and function, but how exercise affects sphingolipid metabolism is not yet known. We hypothesize that alterations in skeletal muscle sphingolipid metabolism with exercise training are necessary to enhance muscle mass with further exercise retraining. Here, mice were SEDentary (SED; static cages) or exercise-TRAINed (TRAIN; voluntary wheel running) and chow-fed. We performed body composition analysis (using EchoMRI) and skeletal muscle collection tibialis anterior ( TA), extensor digitorum longus ( EDL), gastrocnemius ( Gas), Soleus ( Sol), plantaris ( Plant), and levator ani ( LA) following training (4wks), detraining (8wk), and retraining (12wk) in three independent cohorts. Sphingolipid and myogenic gene expression was measured in TA muscle by qPCR. Exercise training concomitantly increased lean and decreased fat percentage ( p<0.05), while increasing Sol muscle mass in TRAIN mice ( p<0.05), compared to SED. This was accompanied by higher sphingolipid metabolism ( Acer1, p<0.05; and Cers1, p=0.058) and myogenic gene expression ( MyoD, Myf5; p<0.05). Following detraining, TRAIN mice had an overall increase in lean-to-fat mass ( p<0.05) while maintaining all individual muscle masses ( p<0.05), compared to SED. This was accompanied by a reduction in gene expression of the sphingolipid receptor S1pr1 and myogenic factor Myf5 ( p<0.05), but no differences in sphingolipid metabolism ( Acer1, Cers1). Lastly, retraining increased lean and decreased fat percentage ( p<0.05) and enhanced the masses of TA, Gas, Sol, and Plant muscles in TRAIN mice ( p<0.05), compared to SED. This was accompanied by a reduced expression of rate limiting sphingolipid synthesis genes Sptlc1 and Sptlc2 and the kinase Sphk1 ( p<0.05), but no differences in Cers1 or myogenic gene expression in TRAIN mice, compared to SED. Overall, our data shows that exercise training and retraining potentiate muscle mass accretion and dynamically regulates sphingolipid metabolism adaptations. These data suggest a potential role for sphingolipids to modulate long-lasting improvements to skeletal muscle. Funding was provided by the University of Illinois Urbana-Champaign. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.