Suppressing postcollection lysophosphatidic acid metabolism improves the precision of plasma LPA quantification.

Abstract Lysophosphatidic acid (LPA) is a potent signaling lipid, and state-dependent alterations in LPA make it a promising diagnostic marker for various diseases. However, plasma LPA concentrations vary widely among reports, even under normal conditions. These variations can be attributed, at least in part, to the artificial metabolism of LPA after blood collection, thus complicating the use of plasma LPA as a clinical biomarker. Previous studies focused on suppressing LPA production by the LPA-producing enzyme autotaxin (ATX) but did not take the artificial LPA degradation into account. Here, we aimed to develop an optimized plasma preparation method that reflects the concentration of LPA in the circulating blood by finding conditions to suppress both the production and degradation of LPA after blood collection. The main features of the devised method were suppression of LPA production and degradation after blood collection by keeping whole blood samples at low temperature and followed by adding an ATX inhibitor to plasma samples. Using this devised method, the LPA level did not change for 30 minutes after blood collection, and mouse plasma LPA concentrations showed minimal variation across individual animals, as determined by LC-MS/MS. Additionally, human and mouse LPA levels were found to be much lower than those previously reported, ranging from 40 to 50 nM. Finally, the increased accuracy made it possible to detect circadian rhythms in the levels of certain LPA species in mouse plasma. These results demonstrate the usefulness of the devised plasma preparation method to determine accurate plasma LPA concentrations.