To assess the influence of pro-inflammatory IL-1 genotype status on the risk of CAD, defined as >50% diameter stenosis, and cardiovascular events mediated by OxPL and Lp(a).
Oxidized phospholipids (OxPL) are pro-inflammatory, circulate on lipoprotein (a) [Lp(a)] and mediate coronary artery disease (CAD). Genetic variations in the interleukin-1 (IL-1) region are associated with increased inflammatory mediators.
IL-1 genotypes, OxPL on apolipoprotein B-100 (OxPL/apoB) and Lp(a) levels were measured in 499 patients undergoing coronary angiography. The composite genotype termed IL-1(+) was defined by three single nucleotide polymorphisms (SNPs) in the IL-1 gene cluster associated with higher levels of pro-inflammatory cytokines. All other IL-1 genotypes were termed IL-1(−).
Among IL-1(+) patients, the highest quartile of OxPL/apoB was significantly associated with a higher risk of CAD compared to the lowest quartile (OR 2.84, P=0.001). This effect was accentuated in patients ≤60 years old (OR 7.03, P<0.001). In IL-1(−) patients, OxPL/apoB levels showed no association with CAD. The interaction was significant for OxPL/apoB (OR 1.99, P=0.004) and Lp(a) (OR 1.96, P<0.001) in IL-1(+) versus IL-1(−) groups for patients ≤60 years old but not for patients >60 years old. In IL-1(+) patients ≤60 years old, after adjusting for established risk factors, high sensitivity C-reactive protein and Lp(a), OxPL/apoB remained an independent predictor of CAD. IL-1(+) patients above the median OxPL/apoB presented to the cardiac catheterization laboratory a mean of 3.9 years earlier (P=0.002) and had worse 4-year event-free survival (death, MI, stroke, and revascularization) compared to other groups (P=0.006).
Our study suggests that IL-1 genotype status can stratify population risk for CAD and cardiovascular events mediated by OxPL. These data suggest a clinically-relevant biological link between pro-inflammatory IL-1 genotypes, oxidation of phospholipids, Lp(a) and genetic predisposition to CAD and cardiovascular events.