rs1800775 — CETP -629C>A

CETP -629C>A — The HDL Promoter Switch

Every day your liver makes a protein called CETP¹¹ CETP
Cholesteryl Ester Transfer Protein — an enzyme that shuttles cholesteryl esters from protective HDL particles to LDL and VLDL, effectively draining your HDL of its cargo. The more CETP your liver produces, the lower your HDL cholesterol tends to be. A single nucleotide change in the CETP gene's promoter region — 629 bases upstream of the transcription start site — determines how much CETP your liver produces, and therefore shapes your HDL cholesterol set point from birth.

The Mechanism

The -629 position sits within a Sp1/Sp3 transcription factor binding site²² Sp1/Sp3 transcription factor binding site
Sp1 and Sp3 are zinc-finger proteins that bind GC-rich DNA sequences and regulate transcription — Sp3 commonly acts as a repressor when it outcompetes Sp1 at the same site. The C allele creates a sequence that Sp1 and Sp3 bind poorly. The A allele creates a high-affinity Sp1/Sp3 binding site — and Sp3 at this position acts as a transcriptional repressor, suppressing CETP gene expression by approximately 25%.

Carriers of the A allele therefore have lower circulating CETP protein. Because CETP transfers cholesteryl esters from HDL to LDL and VLDL, less CETP activity means cholesteryl esters accumulate inside HDL particles — raising measured HDL cholesterol. The original mechanistic study by Dachet et al.³³ original mechanistic study by Dachet et al. showed that CC homozygotes had 0.45 μg/mL higher circulating CETP mass than AA homozygotes, and correspondingly lower HDL-C levels, in 536 subjects from the ECTIM study.

The Evidence

The largest and most rigorous study of this variant is the Women's Genome Health Study (WGHS)⁴⁴ Women's Genome Health Study (WGHS)
Ridker et al. 2009; 18,245 initially healthy American women of European ancestry, followed prospectively for ~10 years for cardiovascular events. In this genome-wide analysis, rs1800775 was identified as the single most strongly associated SNP in the entire CETP region for HDL-C. HDL-C was approximately 52 mg/dL in CC carriers, 52 mg/dL in CA carriers, and 54 mg/dL in AA homozygotes. The age-adjusted hazard ratio for myocardial infarction was 0.82 per A allele (P=0.048), though this association was attenuated when HDL-C was included in the model (HR 0.90, P=0.31) — suggesting the cardiovascular effect operates largely through HDL.

A 2015 resequencing study⁵⁵ 2015 resequencing study
Pirim et al. Metabolism 2015; 602 non-Hispanic whites and 353 African blacks confirmed that rs1800775 independently associates with HDL-C in both European and African populations. Importantly, in Europeans this variant is in strong LD with TaqIB (rs708272, r²=0.75), but in African Americans LD is much weaker (r²=0.19) — meaning rs1800775 and TaqIB may capture largely overlapping signals in Europeans but distinct functional variation in Africans.

A meta-analytic evaluation⁶⁶ meta-analytic evaluation of 17 studies (5,441 CHD cases, 7,967 controls, 22,488 subjects in lipid analyses) found that the C allele associates with 3.65–4.36 mg/dL lower HDL-C and 0.45 μg/mL higher CETP mass. Among Caucasian populations, CC carriers had significantly higher CHD odds (OR 1.41–1.43 under dominant/homozygous models), while overall association in mixed populations was not significant — consistent with population heterogeneity in LD structure.

The HDL-C Paradox

A critical nuance: CETP variants that raise HDL by reducing cholesteryl ester transfer do not always translate into the same cardiovascular protection as HDL raised by other means. The HDL-raising effect of the -629A allele is partly attenuated by elevated triglycerides⁷⁷ partly attenuated by elevated triglycerides
When TG-rich lipoproteins are high, CETP transfer activity from HDL becomes dominated by mass-action effects of the TG substrate; CETP genotype effects on HDL diminish in high-TG states. The interaction between CETP genotype and plasma triglycerides means that the -629A benefit on HDL is largest at low triglyceride levels.

Practical Actions

For CC homozygotes, CETP expression is at its highest reference level, and HDL-C tends to run 3–6 mg/dL lower than in AA homozygotes. This is a modest but consistent effect operating as a background risk factor for low HDL. Lifestyle-level intervention can offset the genotype: aerobic exercise is one of the most robust HDL-raising stimuli and works regardless of CETP genotype. Dietary fat quality (replacing saturated fat with unsaturated fat) also supports HDL levels. The clinical priority for CC individuals is ensuring HDL-C is monitored regularly and that other lipid risk factors (LDL, triglycerides) are well managed, since the genotype alone does not cause disease.

For CA heterozygotes, HDL-C is in the population range but slightly elevated relative to CC individuals. No specific intervention is required.

For AA homozygotes, lower CETP activity raises HDL-C. Monitoring the full lipid panel rather than HDL alone is worthwhile: if HDL is elevated alongside high triglycerides, the cardiovascular benefit is reduced.

Interactions

rs1800775 is in strong LD with the CETP TaqIB variant rs708272 in European populations (r²=0.75). Tests that report TaqIB are largely capturing the same signal in Europeans, though rs1800775 is considered the functional variant given its direct transcriptional effect. In African ancestry populations, the two SNPs are only weakly correlated (r²=0.19), and both should be assessed independently.

CETP variants interact additively with LIPC variants (rs1532085) in raising HDL-C, but studies suggest the CETP-side interaction is what primarily translates to cardiovascular benefit. For individuals carrying CETP CC and LIPC GG genotypes, HDL may be at its lowest for both loci and monitoring is most important.