Effects of sphingomyelin derivatives on innervated and denervated rat soleus muscle

Present work is aimed at studying the effects of natural bioactive sphingomyelin derivatives, on normal and denervated slow-twitch skeletal muscle. The effects on fibre cross sectional area and myosin heavy chains composition of sphingosine (SPH), sphingosine 1-phosphate (S1P) and sphingosylphosphorylcholine (SPC) were studied. Denervation was bilaterally performed cutting the sciatic nerve at the level of trochanter in adult rats. A group of animals was used as controls. Sphingolipids were continuously released by a mini-osmotic pumps implanted subcutaneously in the scapular region and connected by a catheter to the left (control or denervated) soleus muscles. Supplementation of SPC to adult control soleus muscle, produced significant atrophy of fibres and small changes to fibre type composition. No significant effects of SPH and S1P were found. In contrast, SPH and, to a smaller extent, S1P reduced the atrophy and the slow-to-fast transformation produced by 7-14 days of denervation. Preliminary results indicate that these sphingolipids may exert their action by reducing the overall muscle apoptosis and by activating satellite cells.