Heritability of apolipoprotein (a) traits in two-generational African-American and Caucasian families.

Heritability of allele, apo(a) isoform sizes, and isoform-associated lipoprotein(a) [Lp(a)] levels was studied in 82 Caucasian and African-American families with two parents and two children (age: 6-74 years). We determined: ) Lp(a) levels; ) allele sizes; ) apo(a) isoform sizes; and ) isoform-specific apo(a) levels (ISLs), the amount of Lp(a) carried by an individual apo(a) isoform. Trait heritability was estimated by mid-parent-offspring analysis. The ethnicity-adjusted heritability estimate for Lp(a) level was 0.95. Heritability for ISLs corresponding to the smaller allele in a given allele-pair was higher than that corresponding to the larger allele (0.91 vs. 0.59, = 0.017). Although not statistically different, heritability for both apo(a) isoforms (0.90 vs. 0.70) and alleles (0.98 vs. 0.82) was higher for the smaller versus larger sizes. Heritability was generally lower in African-Americans versus Caucasians with a 4-fold difference for the larger allele (0.25 vs. 0.94, = 0.001). In Caucasians, an overall higher heritability pattern was noted for the older (≥47 years) versus younger (<47 years) families. In conclusion, Lp(a) level and traits associated with the smaller alleles were strongly determined by genetics, although with a varying ethnic influence. Ethnic differences in heritability of the larger allele warrant further investigations.