Abstract 16783: Possible Usefulness of the Assay of Choline and Choline-containing Phospholipids in Clinical Laboratory Medicine in the Fields of Dyslipidemia and Atherosclerosis

Abstract

Background:Plasma lipid parameters, such as LDL cholesterol, are established biomarkers for atherosclerotic diseases and utilized for the diagnosis and treatment of dyslipidemia. However, seeking for novel biomarkers for atherosclerosis is a still challenging issue because of a problem of the residual risk. Sphingomyeline (SM) is a precursor of ceramide, sphingosine and sphingosine 1-phosphate, while choline is produced from lysophosphatidylcholine (LPC) when LPC is hydrolyzed to lysophosphatidic acid. Hence, choline, SM and LPC might be related with these bioactive lipids in vivo. In this study, we developed enzymatic methods to measure serum SM, plasma choline and LPC, and assay the samples from healthy subjects and coronary heart disease(CHD)-related patients.

Methods and Results: We developed enzymatic methods to assay choline, SM and LPC with choline oxidase, sphingomyelinase and lysophospholipase in automated performance. First, we measured choline, SM and LPC and analyzed their correlation with conventional lipid parameters in healthy subjects (n=146). As for cholesterol and TG, SM was correlated with LDL-C (r=0.633) and HDL-C (r=0.376) and LPC was correlated with LDL-C (r=0.656) and TG (r=0.276), while choline had no significant correlation. As for apolipoproteins, SM was significantly correlated with Apo B (r=0.472), while LPC with Apo Cs (CIII r=0.373, CII r=0.326). These results suggest the possibility that SM and LPC might have a different role in lipoprotein metabolism. Next, we analyzed 141 CHD patients consisting of angiographically normal coronary arteries (NCA; n=31), stable angina pectoris (SAP; n=72), and acute coronary syndrome (ACS; n=38). We found that SM was significantly elevated in ACS groups (NCA 565.7 μ mol/L, SAP 531.6 μ mol/L, ACS 590.4 μ mol/L, p<0.01), while LPC and choline was not different among three groups. Logistic regression analysis revealed that choline was the second independent factor predicting ACS, following LDL-C (odds ratio 0.615 per tertile, p=0.016).

Conclusion: We developed automated enzymatic methods for measuring choline, SM, and LPC. We found that SM and LPC had distinct correlations with several lipid parameters and that choline might be a candidate as a protective biomarker for ACS.