A bioactive sphingolipid; the primary short-chain ceramide found in brain tissue; synthesis is regulated by Lass1 in mice; positively correlated to body mass index and inversely related to insulin sensitivity; reduces cell growth in UM-SCC-22A squamous cell carcinoma cells; selectively downregulated in 32 squamous cell carcinoma tumor tissues; positively correlated to body mass index and inversely related to insulin sensitivity in type 2 diabetic patients