Simultaneous quantitative LC-MS/MS analysis of 13 apolipoproteins and lipoprotein (a) in human plasma†

Numerous studies have revealed a close correlation between the levels of apolipoproteins (Apos) (including lipoprotein(a) [Lp(a)]) and an increased risk of cardiovascular disease in recent decades. However, clinically, lipid profiling remains limited to the conventional plasma levels of cholesterol, triglyceride, ApoA1, and ApoB, which brings the necessity to quantify more apolipoproteins in human plasma. In this study, we simultaneously quantified 13 apolipoproteins and Lp(a) in 5 μL of human plasma using the LC-MS/MS platform. A method was developed for the precise detection of Lp(a), ApoA1, A2, A5, B, C1, C2, C3, D, E, H, L1, M, and J. Suitable peptides were selected and optimized to achieve clear separation of each peak. Method validation consisting of linearity, sensitivity, accuracy and precision, recovery, and matrix effects was evaluated. The intra-day CV ranged from 0.58% to 14.2% and the inter-day CV ranged from 0.51% to 13.3%. The recovery rates ranged from 89.8% to 113.7%, while matrix effects ranged from 85.4% to 113.9% for all apolipoproteins and Lp(a). Stability tests demonstrated that these apolipoproteins remained stable for 3 days at 4 °C and 7 days at −20 °C. This validated method was successfully applied to human plasma samples obtained from 45 volunteers. The quantitative results of ApoA1, ApoB, and Lp(a) exhibited a close correlation with the results from the immunity transmission turbidity assay. Collectively, we developed a robust assay that can be used for high-throughput quantification of apolipoproteins and Lp(a) simultaneously for investigating related risk factors in patients with dyslipidemia.