POLYMORPHISMS OF APOLIPOPROTEIN-A-IV AND APOLIPOPROTEIN-E IN A TURKISH POPULATION LIVING IN GERMANY

Human apolipoproteins (apo) E and apo A-IV are polymorphic with signif icantly different allele frequencies among different ethnic groups. Wh ereas the variation at the apo E gene locus affects plasma cholesterol levels in all populations studied so far and is associated with longe vity in Caucasians, the influence of the common apo A-IV polymorphism on plasma lipoproteins has not been unanimously accepted. We have ther efore determined the common apo E and apo A-IV polymorphisms by isoele ctric focusing, calculated the respective allele frequencies and studi ed their effects on plasma lipoproteins in a random sample of 240 nonr elated Turkish subjects (141 males, 99 females) living in Germany and originating from central and eastern Anatolia. When compared with the German population and other Caucasians in Europe a prominence of the a po epsilon 3 allele frequency (0.885) was accompanied by a decrease in the frequencies of both the apo epsilon 2 allele (0.048) and the apo epsilon 4 allele (0.067). Thus, the Turkish population studied here cl ustered with populations mainly from southern Europe and Japan, which have low epsilon 2 and epsilon 4 allele frequencies. Also, the frequen cy of the A-IV-1 allele was higher (0.967) and that of the A-IV-2 alle le lower (0.033) in the Turkish subjects studied than in other populat ions. At an average level of total cholesterol of 194.5 +/- 45 mg/dl, no significant influence of the A-IV alleles on plasma lipoproteins wa s seen. However, apo E and apo B differed significantly between apo E phenotypes, with high levels of apo E and low levels of cholesterol an d apo B in carriers of the epsilon 2 allele, and vice versa for the E4 allele. The average cholesterol excess for the epsilon 2 allele was - 7.95 mg/dl, for the epsilon 3 allele, -1.34, and for the epsilon 4 all ele, +14.15 mg/dl. Thus, despite the unusual frequency distribution of the apo E alleles, their effects on plasma lipoproteins are within th e range reported for other populations in Europe.