Nitrated unsaturated fatty acids, such as 10- and 12-nitrolinoleate (LNO2), cholesteryl nitrolinoleate, and nitrohydroxylinoleate, represent a new class of endogenous lipid-derived signalling molecules. LNO2 isomers serve as potent endogenous ligands for PPARγ and can also decompose or be metabolized to release nitric oxide.^1,2,3,4 10-Nitrooleate is one of two regioisomers of nitrooleate, the other being 9-nitrooleate (OA-NO2; used for the mixture of isomers), which are formed by nitration of oleic acid in approximately equal proportions in vivo.⁵ Peroxynitrite, acidified nitrite, and myeloperoxidase in the presence of H2O2 and nitrite, all mediate the nitration of oleic acid. OA-NO2 is found in human plasma as the free acid and esterified in phospholipids at concentrations of 619 ± 52 nM and 302 ± 369 nM, respectively. OA-NO2 activates PPARγ approximately 7-fold at a concentration of 1 µM and effectively promotes differentiation 3T3-L1 preadipocytes to adipocytes at 3 µM.⁵