Abstract
Fatty acids (FAs) are carboxylic acid with carbon chain and classified according to the length of carbon chain and the number of double bonds. The source of FAs in a human body is the absorption from intake foods, the release from several lipid classes by hydrolysis and the de novo lipogenesis including the condensation of acetyl-CoA. They have multiple roles including energy sources, precursor compounds for the synthesis of cellular lipids, regulators of gene expression and signal mediators. In recent years, the functions of FAs have attracted a great deal of attention, and it is important to analyze them accurately by FA species. To quantify levels of FA species accurately without derivatization and also to develop the method of simultaneous analysis of FA and several lipid classes, in this study, authors carried out the optimization of MS conditions of 10 FA species including the combination of a precursor ion and a product ion systematically. We clarified that both carbon chain length and the number of double bonds affect the ionization efficiency of FA species, resulting in the difference of slope values obtained from calibration curves. These differences are useful as correction parameters, which enable to quantify FA species in the internal standardized method accurately without the use of deuterium-labeled internal standards. Furthermore, the developed method was applied to FA profiling of 8 mammalian sera. Total FA levels of mouse serum was the highest compared with other mammalians, suggesting higher activity of FA synthesis and/or lipolysis of mouse.
