Measurement of plasma choline in acute coronary syndrome: importance of suitable sampling conditions for this assay

Ryunosuke Ohkawa,Hiroyuki Daida,Yutaka Yatomi,Junken Aoki,Minoru Tozuka,Koji Igarashi,Takahiro Nojiri,Tatsuya Kishimoto,Makoto Kurano,Shigemi Hosogaya,Shigeo Okubo,Hitoshi Ikeda,Yukio Ozaki,Noboru Sakai,Katsumi Miyauchi,Tomotaka Dohi

doi:10.1038/s41598-018-23009-x

Abstract

Blood choline has been proposed as a predictor of acute coronary syndrome (ACS), however different testing procedures might affect the choline concentration because the lysophospholipase D activity of autotaxin (ATX) can convert lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline in human blood. Although the influences of ATX on LPA levels are well known in vivo and in vitro, those on choline have not been elucidated. Therefore, we established suitable sampling conditions and evaluated the usefulness of plasma choline concentrations as a biomarker for ACS. Serum LPA and choline concentrations dramatically increased after incubation depending on the presence of ATX, while their concentrations in plasma under several conditions were differently modulated. Plasma choline levels in genetically modified mice and healthy human subjects, however, were not influenced by the ATX level in vivo, while the plasma LPA concentrations were associated with ATX. With strict sample preparation, the plasma choline levels did not increase, but actually decreased in ACS patients. Our study revealed that ATX increased the choline concentrations after blood sampling but was not correlated with the choline concentrations in vivo; therefore, strict sample preparation will be necessary to investigate the possible use of choline as a biomarker.

Highlights

Blood choline has been proposed as a predictor of acute coronary syndrome (ACS), different testing procedures might affect the choline concentration because the lysophospholipase D activity of autotaxin (ATX) can convert lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline in human blood
Under the condition where whole blood was incubated, these two substances showed different kinetics; the present study showed that the serum LPA and choline concentrations dramatically increased after incubation depending on the presence of ATX (Fig. 1), while the plasma LPA and choline concentrations were differently modulated when the samples were incubated under several conditions; in whole blood plus EDTA-2K, the increase in the plasma LPA level was suppressed by the inactivation of ATX with a chelating agent, while no remarkable modulation of the plasma choline levels was observed
In relation to the variations in the plasma choline level, the degree of increase in plasma obtained from whole blood prepared with heparin was higher than that in samples prepared with EDTA

Summary

Introduction

Blood choline has been proposed as a predictor of acute coronary syndrome (ACS), different testing procedures might affect the choline concentration because the lysophospholipase D activity of autotaxin (ATX) can convert lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline in human blood. Using the suitable sample handling established in the present study, we measured the plasma choline levels in both healthy subjects and patients who had undergone coronary angiography to investigate the possibility of its use as a biomarker.

Results

Conclusion