Multiplexed apolipoprotein profiling advances the assessment of residual lipid-related cardiovascular risk

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Background and Purpose Low-density lipoprotein cholesterol (LDL-C) is among the conventional lipid parameters used to predict risk of cardiovascular disease (CVD). Statins lower blood levels of pro-atherogenic LDL-C, but a residual cardiovascular risk remains in some individuals with therapeutically optimised LDL-C levels. Although the metabolism of LDL-C and other lipoprotein particles is governed by a range of different apolipoproteins, only apolipoproteins A-I and B are measured in clinical assays. Using a more comprehensive apolipoprotein panel in a large epidemiological cohort, this study aimed to determine the association of individual apolipoprotein levels with risk of coronary heart disease (CHD). Methods Bottom-up multiple reaction monitoring–mass spectrometry (MRM–MS) was used in conjunction with stable isotope-labelled peptide standards to quantify plasma levels of 13 apolipoproteins in participants of the Precocious Coronary Artery Disease (PROCARDIS) study (N = 1916; 941 cases of CHD, 975 controls). The relationship between apolipoprotein levels and CHD was assessed after adjusting for established risk factors for CVD and correcting for statin use. Results The strongest positive associations with CHD in the PROCARDIS study were seen for triglyceride-related apolipoproteins C-I (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.63–3.46), C-III (OR 2.95, 95% CI 1.85–4.71) and E (OR 2.35, 95% CI 1.54–3.58), as well as for apolipoprotein (a) (kringle IV type 2 repeat, OR 2.84, 95% CI 2.04–3.95). Comparing these with associations of apolipoproteins with CVD in the Bruneck study (N = 688) revealed consistency across the two cohorts. Robust inverse associations with CHD were observed for apolipoproteins A-IV (OR 0.45, 95% CI 0.31–0.65) and M (OR 0.29, 95% CI 0.19–0.44). Conclusion Analysing two large epidemiological cohorts, Bruneck and PROCARDIS, demonstrated that multiplexed apolipoprotein profiling improves the understanding of cardiovascular risk independent of conventional lipid parameters. Most prominently, triglyceride-related apolipoproteins were shown to positively associate with residual cardiovascular risk. The findings of this study support the need for development and implementation of standardised, MRM–MS-based apolipoprotein profiling assays to guide novel lipid-modifying therapies beyond statins.