EN
Ceramide (Cer) and sphingomyelin (SM) are members of sphingolipid (SL) family. Their concentrationsin the brain undergo substantial changes in many pathologies. They are also important players in diabetes-linked brain dysfunctions, in which increased content of ceramides can be toxic to neurons. The aim of the study was to evaluate selected parameters of sphingolipids and insulin pathways in prefrontal cortex (PC) and hippocampus (H) of rats with experimentally induced hyperglycemia. STZ-rat model of type 1 diabetes and high fat diet model of insulin resistance were used. Analyses of studied parameters were performed by GLC, IHC and Elisa. We found the augmented levels of ceramides in H and PC and only minor in striatum and cerebellum of rats with STZ-induced diabetes. Similar expressions of Cer were confirmed by IHC. Myriocin, an inhibitor of an enzyme of ceramide de novo synthesis pathway, reduced ceramide generation in hyperglycemic brains, particularly in PC, which was reflected in altered Cer synthase activities. In addition, we reported the fluctuations in sphingomyelin levels in investigated structures. The level of insulin did not change in H and PC of STZ-treated rats. An expression of insulin receptor and its phosphorylated form decreased in both structures, but was restored after myriocin administration. Similarly, Akt and phosphorylated Akt changed in these structures suggesting important role of de novo Cer synthesis in intracellular pathways of insulin. In the rat model of high fat diet, which leads to insulin resistance, the sphingolipid pattern (Cer and SM) was altered in H and PC as well. Metformin, the drug of choice in diabetes type 2, influenced the content of the above SLs in these structures, suggesting the additional central activity of antidiabetic treatment. We conclude that ceramide and SM may be important mediators of diabetes- accompanied brain dysfunction.