New Functional Promoter Polymorphism, CETP/−629, in Cholesteryl Ester Transfer Protein (CETP) Gene Related to CETP Mass and High Density Lipoprotein Cholesterol Levels

Abstract

Abstract-A new polymorphism located at position Ϫ629 (CETP/Ϫ629A/C) in the promoter of the cholesteryl ester transfer protein (CETP) gene is described. The Ϫ629A allele was associated with lower CETP mass (PϽ0.0001) and higher high density lipoprotein cholesterol (PϽ0.001) than the C allele in a sample of 536 control subjects from the ECTIM study. Transfection studies in HepG2 cells with a luciferase expression vector incorporating a 777-bp fragment of the CETP promoter and containing either A or C at position Ϫ629 showed significantly lower luciferase activity with the promoter fragment of the A allele (Ϫ25%, PϽ0.05). By gel-shift assay, DNA-protein interactions were evaluated in nuclear extracts of HepG2 cells with the use of 2 probes (A or C probe) composed of 20 bp of the promoter sequence surrounding the polymorphic site. Two specific complexes of distinct migration rate were identified with the A and the C probe. Competition with an excess of oligonucleotide containing the Sp1 consensus binding site showed that a protein(s) of the Sp transcription factor family was implicated in complex formation with the A probe but not with the C probe. Incubation with specific antibodies indicated that Sp1 and Sp3 bound specifically to the A probe. We introduced mutations in the Ϫ629-Sp1 binding site to test its functionality and to define the characteristics of transcription factor binding. We showed, by gel-shift assay, that no nuclear proteins bound to the mutated sequence. Transient transfection of HepG2 cells revealed that the expression of the mutated fragment was significantly increased compared with that of the A promoter fragment (25%, PϽ0.05). The mutated fragment displayed the same activity as that of the C promoter. These results indicate that Sp1 and/or Sp3 repress CETP promoter activity, whereas nuclear factors binding the C allele are without effect on promoter expression. Key Words: cholesteryl ester transfer protein Ⅲ gene polymorphisms Ⅲ transcription factors Ⅲ ECTIM Ⅲ cardiovascular disease S everal prospective epidemiological studies have shown that elevated levels of HDL cholesterol (HDL-C) constitute an independent negative risk factor for coronary heart disease. 1 Cholesteryl ester transfer protein (CETP) plays a central role in the reverse transport of cholesterol from peripheral tissues to the liver and in the remodeling of plasma lipoproteins by promoting the transfer of cholesteryl esters from HDL to LDL and VLDL lipoproteins. 2,3 The critical role of CETP in lipoprotein metabolism is illustrated by the high levels of HDL-C observed in patients with genetic CETP deficiency. 4 In addition, elevated levels of CETP activity may contribute to an increased risk of coronary artery disease by reducing the cholesterol content of HDL relative to LDL and VLDL 5 and by promoting the formation of atherogenic, small, dense LDL in hyperlipidemic patients. 6 Several common polymorphisms have been described in the CETP gene, 7-10 most of which are associated with plasma CETP mass and HDL-C levels. 9,11,12 How...

Are common disease susceptibility alleles the same in outbred and founder populations?

“…In addition, the C allele at -629 in the promoter has been associated with high-CETP and low-HDL concentrations. 41,42 Here, we report significant associations between the -631C/ -629A haplotype and high HDL by the GTAM and between the -631C/ -629C haplotype and low HDL in the CC test. LPA encodes apolipoprotein(a), a protein component of Lp(a), and variation in this gene is known to affect the concentration of Lp(a) in the blood.…”

Cholesteryl Ester Transfer Protein Variants Have Differential Stability but Uniform Inhibition by Torcetrapib

“…Results were similar with the two subsets (data not shown). Because none of these missense SNPs is in the 5Ј-haploblock previously shown to affect CETP transcription (9,17), the differences in mass among the variants suggest a post-transcriptional effect. To test this, each of the nine individual variants shown in Table II and the double variant P373/Q451 was cloned and expressed in mammalian cells.…”

“…When the studies are sufficiently large, the SNPs associated with lower transcription and lower CETP mass are also associated with higher HDL-C. There may be more than one causal polymorphism in the promoter region with at least two likely candidates (9,10).…”

Genotypes associated with lipid metabolism contribute to differences in serum lipid profile of GH-deficient adults before and after GH replacement therapy

“…Genetic CETP deficiency is associated with very high HDL-C levels. CETP SNP rs1800775 has been shown to regulate CETP transcriptional activity in vitro (39). The SNPs rs708272 and rs1800775 in CETP are closely linked and they have been associated with increased HDL-C and decreased TG concentrations, but with negligible impact on LDL-C and APOB (40).…”