APOLIPOPROTEIN-B AND APOLIPOPROTEIN-E GENETIC POLYMORPHISMS IN THE CAYAPA INDIANS OF ECUADOR

Three DNA polymorphisms (XbaI, EcoRI, and Ins/Del) of the apolipoprote in B (APOB) gene and the CfoI polymorphism of the APOE gene were inves tigated in a sample of 96 Cayapa Indians from Ecuador. The frequencies of the X + (0.182), R + (1.000), and Del alleles (0.432) at the three APOB sites were found to be higher than and to differ significantly f rom those reported for East Asians. No comparisons could be made betwe en the Cayapa and other native Americans because of the lack of data o n these sites. We observed in our sample that, like native American po pulations but unlike East Asians, the APOE allele frequencies were cha racterized by the absence of the APOE2 allele and by a high frequency of the APOE4 allele (0.280). Besides a probable drift effect, the hi gh APOE4 value was tentatively attributed to an effect of selection. Because this allele enhances the absorption of cholesterol by the inte stine, it could confer an advantage to carriers in an unfavorable envi ronment (i.e., diet poor in cholesterol).