Linkage of the cholesteryl ester transfer protein (CETP) gene to LDL particle size: use of a novel tetranucleotide repeat within the CETP promoter.

BACKGROUND A preponderance of small, dense LDL particles, elevated levels of plasma triglycerides (TG), and low levels of HDL characterize the atherogenic lipoprotein phenotype, which is associated with increased coronary artery disease (CAD) risk. Genetic and environmental factors influence LDL size, cholesteryl ester transfer protein (CETP) being one of the candidate genes. CETP mediates the transfer of cholesteryl ester from HDL to apolipoprotein (apo) B-containing lipoproteins in exchange for TG, promoting reverse cholesterol transfer and remodeling of lipoprotein particles. METHODS AND RESULTS We have identified a tetranucleotide repeat (fragment sizes from 324 to 464 bp; heterozygosity index = 0.74) within the CETP promoter and used it in quantitative sib-pair linkage analysis in 119 female dizygotic (DZ) twins. Linkage was found to LDL size (P<0.001), TG (P<0.005), and plasma apoB (P = 0.02). The distribution of the tetranucleotide repeats was bimodal, and there was strong allelic association of the "short" alleles with the B2 allele of CETP TaqIB polymorphic site (P<0.001). CONCLUSIONS This report of linkage of the CETP gene to LDL particle size adds to the list of candidate genes linked to LDL size, supporting the hypothesis of multigenic determination of LDL size heterogeneity. Whether this promoter variation is itself functional or is a marker for a functional site in the CETP gene remains to be determined.