Sphingosine (d16:1) is an atypical sphingolipid formed by a series of enzymatic steps beginning with the condensation of myristoyl-CoA and serine via serine palmitoyltransferase long-chain base subunit 3 (SPTLC3), an SPT subunit that prefers myristoyl-CoA over palmitoyl-CoA.^1,2 Sphingosine d16:1 is present in its free form at low levels in human plasma and as the sphingoid base in a variety of plasma sphingolipid species, including sphingosine-1-phosphate, ceramides, and sphingomyelins, as well as brain cerebrosides, at lower levels compared with the typical d18:1 sphingoid base.^3,4,5,6 Sphingosine (d16:1) inhibits PKC in a mixed micelle activity assay.⁷ It reduces the production of superoxide induced by phorbol 12-myristate 13-acetate (PMA) in isolated human neutrophils and reduces the growth of CHO cells (IC50s = 1 and 3.2 µM, respectively). Plasma levels of sphingolipids containing sphingosine (d16:1) are associated with dietary intake of saturated fatty acids and protein in ethnic Chinese individuals.³ Plasma levels of sphingolipids containing sphingosine (d16:1) are decreased in patients with type 2 diabetes.⁸