A complication of type 1 diabetes mellitus (T1DM) is diabetic myopathy which includes reduced regenerative capacity of skeletal muscle. Sphingolipids are a diverse family of lipids with roles in skeletal muscle regeneration. Some studies have found changes in sphingolipid species levels in T1DM, however, the effect of T1DM on a sphingolipid panel in regenerating skeletal muscle has not been examined. Wild type (WT) and diabetic Ins2Akita+/- (Akita) mice received cardiotoxin-induced muscle injury in their left quadriceps, gastrocnemius-plantaris-soleus, and tibialis anterior muscles with the contralateral muscles serving as uninjured controls. Muscles were collected at 1, 3, 5, or 7 days post-injury. In regenerating muscle from Akita mice, lipid staining with Bodipy 493/503 revealed increased intramyocellular and total lipids as well as perilipin-1-positive cell numbers as compared with WT. Liquid chromatography-mass spectrometry of quadriceps was used to identify sphingolipid levels in skeletal muscle. The C22:0 and C24:0 ceramides were significantly elevated in uninjured Akita, while ceramide C24:1 was decreased in injured Akita compared to WT. Ceramide-1-phosphate was increased in Akita compared to WT regardless of injury, while sphingosine 1-phosphate (S1P) was elevated with injury in WT but this response was muted in Akita mice. Western blotting of key enzymes involved in sphingolipid metabolism revealed S1P lyase, the enzyme which degrades S1P irreversibly, was significantly elevated in the injured muscle in Akita mice during regeneration, in accordance with lower S1P levels. This mouse model of T1DM demonstrates sphingolipidomic changes that may contribute to delayed muscle regeneration.
Keywords: Diabetic Myopathy; Skeletal Muscle Regeneration; Sphingolipids; Sphingosine-1-phosphate; Type 1 Diabetes Mellitus.