Effect of high fat diet enriched with unsaturated and diet rich in saturated fatty acids on sphingolipid metabolism in rat skeletal muscle.

Consumption of high fat diet leads to muscle lipid accumulation which is an important factor involved in induction of insulin resistance. Ceramide is likely to partially inhibit insulin signaling cascade. The aim of this study was to examine the effect of different high fat diets on ceramide metabolism in rat skeletal muscles. The experiments were carried out on rats fed for 5 weeks: (1) a standard chow and (2) high fat diet rich in polyunsaturated fatty acids (PUFA) and (3) diet enriched with saturated fatty acids (SAT). Assays were performed on three types of muscles: slow-twitch oxidative (soleus), fast-twitch oxidative-glycolytic, and fast-twitch glycolytic (red and white section of the gastrocnemius, respectively). The activity of serine palmitoyltransferase (SPT), neutral and acid sphingomyelinase (n- and aSMase), and neutral and alkaline ceramidase (n- and alCDase) was examined. The content of ceramide, sphinganine, sphingosine, and sphingosine-1-phosphate was also measured. The ceramide content did not change in any muscle from PUFA diet group but increased in the SAT diet group by 46% and 52% in the soleus and red section of the gastrocnemius, respectively. Elevated ceramide content in the SAT diet group could be a result of increased SPT activity and simultaneously decreased activity of nCDase. Unchanged ceramide content in the PUFA diet group might be a result of increased activity of SPT and alCDase and simultaneously decreased activity of SMases. We conclude that regulation of muscle ceramide level depends on the diet and type of skeletal muscle.