Multivariable Mendelian Randomization Prioritizes ApoB as Key Lipid Risk Factor for Coronary Artery Disease

This multivariable Mendelian randomization (MVMR) study applied a novel high-throughput statistical framework to disentangle the causal effects of highly correlated lipid fractions — ApoB, LDL-C, and triglycerides — on coronary artery disease risk in 453,595 participants from large GWAS consortia, using genetic instruments to isolate each lipid’s independent causal contribution.

The top-ranked causal model contained ApoB as the sole lipid driver of CAD risk (Model Posterior Probability = 0.464). ApoB had the highest Marginal Inclusion Probability (MIP = 0.868) among all lipid traits. When ApoB was included in the model, LDL-C and triglycerides did not provide additional independent causal information — their associations with CAD were mediated through ApoB.

This MVMR result directly addresses a long-standing ambiguity: when LDL-C, ApoB, and triglycerides are correlated, standard analyses cannot determine which is causally responsible for CAD. The multivariable genetic approach — using pleiotropic genetic instruments that naturally move each lipid fraction somewhat independently — provides a genetic quasi-experiment for isolating which measure carries the causal signal.

The answer: ApoB is the primary causal lipid determinant of CAD, mediating LDL-C’s and triglycerides’ effects. Once ApoB is accounted for, other lipid measures contribute no independent causal information. This is consistent with the biological model that all atherogenic ApoB-containing lipoproteins (LDL, VLDL, IDL, Lp(a)) drive atherosclerosis through a common mechanism — arterial wall retention of ApoB-containing particles — and that ApoB is the comprehensive measure capturing this unified mechanism.

We rate the evidence strong. A large-scale multivariable Mendelian randomization study in 453,595 participants establishing ApoB as the primary causal lipid risk factor for coronary artery disease, with LDL-C and triglycerides mediated through ApoB — the most methodologically rigorous genetic evidence for the ApoB-centric lipid risk framework.