Controlled Tetradeuteration of Straight-Chain Fatty Acids: Synthesis, Application, and Insight into the Metabolism of Oxidized Linoleic Acid.

We describe a concise and reliable protocol for the precisely controlled tetradeuteration of straight-chain fatty acids (FAs) at the α- and β-positions that is generally applicable to a variety of FAs, including trans-FAs, polyunsaturated FAs (PUFAs), and their oxidized derivatives. The precisely controlled introduction of four deuterium atoms into the FAs enables their persistent and quantitative tracking by LC-MS/MS analysis based on their molecular structures. In addition, the phosphatidylcholine (PC) species prepared from the tetradeuterated FAs thus obtained give a diagnostic peak, namely, a phosphocholine fragment that contains deuterium, in the LC-MS/MS analysis. With these features, the metabolism of a representative oxidized linoleic acid, that is, hydroxyoctadecadienoic acid (HODE), was investigated, leading to the identification of acyltransferases that transfer the acyl moiety derived from HODE to lysophosphatidylcholine.