Association of LPA Variants With Risk of Coronary Disease and the Implications for Lipoprotein(a)-Lowering Therapies

Elevated lipoprotein(a) (Lp[a]) is a highly prevalent (around 20% of people) genetic risk factor for cardiovascular disease and calcific aortic valve stenosis, but no approved specific therapy exists to substantially lower Lp(a) concentrations. We aimed to assess the efficacy, safety, and tolerability of two unique antisense oligonucleotides designed to lower Lp(a) concentrations.

Elevated lipoprotein(a) levels are associated with myocardial infarction (MI) in some but not all studies. Limitations of previous studies include lack of risk estimates for extreme lipoprotein(a) levels, measurements in long-term frozen samples, no correction for regression dilution bias, and lack of absolute risk estimates in the general population. We tested the hypothesis that extreme lipoprotein(a) levels predict MI in the general population, measuring levels shortly after sampling, correcting for regression dilution bias, and calculating hazard ratios and absolute risk estimates. We examined 9330 men and women from the general population in the Copenhagen City Heart Study. During 10 years of follow-up, 498 participants developed MI. In women, multifactorially adjusted hazard ratios for MI for elevated lipoprotein(a) levels were 1.1 (95% CI, 0.6 to 1.9) for 5 to 29 mg/dL (22nd to 66th percentile), 1.7 (1.0 to 3.1) for 30 to 84 mg/dL (67th to 89th percentile), 2.6 (1.2 to 5.9) for 85 to 119 mg/dL (90th to 95th percentile), and 3.6 (1.7 to 7.7) for > or =120 mg/dL (>95th percentile) versus levels 60 years with lipoprotein(a) levels of or =120 mg/dL, respectively. Equivalent values in men were 19% and 35%. We observed a stepwise increase in risk of MI with increasing levels of lipoprotein(a), with no evidence of a threshold effect. Extreme lipoprotein(a) levels predict a 3- to 4-fold increase in risk of MI in the general population and absolute 10-year risks of 20% and 35% in high-risk women and men.

Plasma lipoprotein(a) [Lp(a)], a low density lipoprotein particle with an attached apolipoprotein(a) [apo(a)], varies widely in concentration between individuals. These concentration differences are heritable and inversely related to the number of kringle 4 repeats in the apo(a) gene. To define the genetic determinants of plasma Lp(a) levels, plasma Lp(a) concentrations and apo(a) genotypes were examined in 48 nuclear Caucasian families. Apo(a) genotypes were determined using a newly developed pulsed-field gel electrophoresis method which distinguished 19 different genotypes at the apo(a) locus. The apo(a) gene itself was found to account for virtually all the genetic variability in plasma Lp(a) levels. This conclusion was reached by analyzing plasma Lp(a) levels in siblings who shared zero, one, or two apo(a) genes that were identical by descent (ibd). Siblings with both apo(a) alleles ibd (n = 72) have strikingly similar plasma Lp(a) levels (r = 0.95), whereas those who shared no apo(a) alleles (n = 52), had dissimilar concentrations (r = -0.23). The apo(a) gene was estimated to be responsible for 91% of the variance of plasma Lp(a) concentration. The number of kringle 4 repeats in the apo(a) gene accounted for 69% of the variation, and yet to be defined cis-acting sequences at the apo(a) locus accounted for the remaining 22% of the inter-individual variation in plasma Lp(a) levels. During the course of these studies we observed the de novo generation of a new apo(a) allele, an event that occurred once in 376 meioses.