Differences in apolipoprotein (a) polymorphism in west Greenland Eskimos and Caucasian Danes

Previous studies in Greenland suggest that death rates from ischemic heart disease [IHD] are lower in Eskimos than in Danes and other Caucasian populations. This has been explained by a high intake of n-3 polyunsaturated fatty acids with beneficial effects on blood lipids and hemostasis. In other populations, lipoprotein(a) [Lp(a)] is associated with IHD, plasma concentrations of Lp(a) being genetically determined to a major extent. We have compared Lp(a) concentrations and apo(a) phenotypes in 120 Greenlandic Eskimos with those in 466 Danish men. The median Lp(a) concentration in Eskimos (8.7 mg/dl;[95% CI 6.5-10.7]) was not significantly different from that in Danes (6.3 mg/dl; [95% CI 5.2-7.0]), whereas the 90th percentile was significantly higher among Danes: 46.36 mg/dl; [95% CI 43.0-54.3] vs. 27.6 mg/dl [95% CI 20.7-36.9]. In 20% of the Danes, but in only 8% of the Eskimos (P = 0.009), the concentration of Lp(a) exceeded 30 mg/dl. The difference is probably explained by a low frequency of the low molecular weight apo(a) phenotypes among Eskimos, since the apo(a) isoforms F and B were absent, and the S1 and S2 types were present in only 3.3% of Eskimos. In contrast, these apo(a) isoforms were present in 26.6% of the Danes in either single-band or double-band phenotypes. The pattern of apo(a) polymorphism found in this study could provide part of a genetic explanation for the putative low rates of IHD in Eskimo populations.