SERUM DISTRIBUTION OF LIPOPROTEIN(A) IN AFRICAN-AMERICANS AND NIGERIANS - POTENTIAL EVIDENCE FOR A GENOTYPE-ENVIRONMENTAL EFFECT

Differences in lipoprotein(a) [Lp(a)] levels across populations have b een described and blacks are known to have higher Lp(a) values compare d to whites. However, environmental factors which influence Lp(a) leve ls have been difficult to identify. We took advantage of the large env ironmental contrast which exists against a common genetic background b etween U.S. and Nigerian blacks to examine the relationship between Lp (a) and apolipoprotein(a) [apo(a)] isoforms. Although the distribution of Lp(a) and apo(a) isoforms was nearly Gaussian in both populations, mean serum Lp(a) values were significantly higher in the United State s than in Nigeria (20.5 vs. 12.7 mg/dl; P = 0.0001) and U.S. blacks ha d a higher frequency of the large molecular weight isoforms compared t o Nigerians. Similar trends in the relationship between apo(a) isoform and Lp(a) concentration were seen in both populations; however, the m agnitude of the effect was different. Compared to the Nigerians, U.S. blacks had significantly higher mean Lp(a) values for the same apo(a) isoform. The association of Lp(a) with low density lipoprotein-cholest erol (LDL-C) level was not significant after correcting for the contri bution of Lp(a) cholesterol to LDL-C in both populations. surprisingly , the association between Lp(a) and total-C remained significant (r = 0.20, P = 0.04) after similar correction for the contribution of Lp(a) cholesterol in the U.S. sample. Understanding the relationship betwee n other factors including lifestyle characteristics capable of influen cing total-C may help explain the unusually high Lp(a) level observed in this U.S. population. (C) 1997 Wiley-Liss, Inc.