Effect of exercise duration on the key pathways of ceramide metabolism in rat skeletal muscles.

Ceramide is the key compound on crossroads of sphingolipid metabolism. The content and composition of ceramides in skeletal muscles have been shown to be affected by prolonged exercise. The aim of this study was to examine the effect of exercise on the activity of key enzymes of ceramide metabolism in skeletal muscles. The experiments were carried out on male Wistar rats (200-250 g) divided into four groups: sedentary, exercised for 30 min, 90 min, and until exhaustion. The activity of serine palmitoyltransferase (SPT), neutral and acid sphingomyelinase (nSMase and aSMase), neutral and alkaline ceramidases (nCDase and alCDase) and the content of ceramide, sphingosine, sphinganine and sphingosine-1-phosphate were determined in three types of muscle. We have found that the activity and expression of SPT increase gradually in each muscle with duration of exercise. These changes were followed by elevation in the content of sphinganine. These data indicate that exercise increases de novo synthesis of ceramide. The aSMase activity gradually decreased with duration of exercise in each type of muscle. After exhaustive exercise the activity of both isoforms of ceramidase were reduced in each muscle. The ceramide level depends both on duration of exercise and muscle type. The ceramide level in the soleus and white gastrocnemius decreased after 30 min of running. After exhaustive exercise it was elevated in the soleus and red gastrocnemius. It is concluded that exercise strongly affects the activity of key enzymes involved in ceramide metabolism and in consequence the level of sphingolipid intermediates in skeletal muscles.