APOLIPOPROTEIN A-IV POLYMORPHISM IN SAAMI AND FINNS - FREQUENCY AND EFFECT ON SERUM-LIPID LEVELS

Apolipoprotein A-TV (apoA-IV) is a glycoprotein constituent of triglyc eride-rich and high-density lipoproteins (HDL) and may thus play an im portant role in lipid metabolism. In Finland two common isoforms (A-IV -1 and A-IV-2) of apoA-IV have been found. The isoforms are the result of the G to T substitution in the third base of the codon 360 in the apoA-IV-2 allele of the apoA-IV gene. The purpose of the study was to determine the apoA-IV allele frequencies in the Saami and the Finns, a nd to relate the apoA-IV phenotypes to serum lipids. The sample was dr awn in connection with a Reindeer Herders' Health Survey performed in northern Finland in 1989. The study group included 248 men with known ethnic origin, Saami and Finns, who lived in the area of the nine nort hernmost municipalities of Finland. ApoA-IV phenotypes from 71 Saami ( both parents Saami) and 177 Finns (both parents Finns) were determined by isoelectric focusing and Western blotting. Serum lipids were deter mined enzymatically. ApoA-IV allele frequencies in the Saami and the F inns were for A-IV-1 0.894 vs 0.944 and for A-IV-2 0.106 vs 0.056, res pectively (chi(2)-test, P < 0.05). The effect of the apoA-IV phenotype on serum HDL-cholesterol levels differed significantly between the Sa ami and the Finns (two-way ANCOVA, interaction between ethnicity and a poA-IV phenotype, P < 0.02). In the Saami, HDL-cholesterol levels were significantly higher in the apoA-IV-2/1 than in the apoA-IV-1/1 pheno types (ANCOVA, P < 0.05). Mean total cholesterol, low-density lipoprot ein (LDL)-cholesterol, apolipoprotein B, HDL-cholesterol and triglycer ide levels did not differ statistically significantly between the Saam i and the Finns. Yet, there was a trend in the Saami of having higher mean total cholesterol, LDL-cholesterol and apolipoprotein B levels th an the Finns among the apoA-IV-2/1 phenotypes, while there was only a small difference in these parameters between the Saami and the Finns a mong the apoA-IV-1/1 phenotypes. In conclusion, the Saami have a highe r frequency of the apoA-IV-2 allele than the Finns and most of the oth er studied populations.