Measurement of concentrations of whole blood levels of choline, betaine, and dimethylglycine and their relations to plasma levels

We aimed at developing a method for the measurement of choline and its metabolites in whole blood (WB). After an extraction step, quantification of choline, betaine, and dimethylglycine (DMG) was performed using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Plasma and WB metabolites were evaluated in a group of 61 elderly people. The calibration curves were linear (r(2) > 0.997) for all compounds. The inter- and intra-assay coefficients of variation for all analytes were <10%. The recoveries were >90% and the relative matrix effect were <= 4.0%. The median concentrations of choline, betaine, and DMG were 11.3, 27.8, and 5.9 mu mol/L in plasma and 66.6, 165, and 13.7 mu mol/L in WB, respectively. There were positive correlations between WB and plasma markers; for choline (r = 0.42), betaine (r = 0.61), and DMG (r = 0.56) (all p <= 0.001). The concentrations of betaine in WB and plasma were significantly higher in men than in women. The concentrations of WB choline and DMG did not differ significantly according to sex. In conclusion, we have established a reliable method for measuring choline metabolites in WB. The concentrations of WB choline, betaine, and DMG seem to reflect intracellular concentrations of these metabolites. (C) 2014 Elsevier B.V. All rights reserved.