Further evidence for an association between the XbaI polymorphism at the apolipoprotein B locus and lipoprotein level.

Subjects with non-familial hypercholesterolemia who were homozygous for absence of an XbaI restriction site in the apolipoprotein B gene (genotype X2X2) had significantly lower values of apolipoprotein B than those possessing the site. Our data are in agreement with those of Berg (1986) and Law et al. (1986) indicating that X2X2 homozygotes have lower levels of apolipoprotein B, total serum cholesterol, triglycerides and LDL cholesterol. The mechanism underlying this effect is unknown, but could reflect different LDL metabolism between subjects with different genotypes.