rs4148102 — ABCG1 ABCG1 intronic PUFA-interaction variant

ABCG1 — When Dietary PUFAs Raise, Not Lower, Cholesterol

ABCG1 (ATP-binding cassette transporter G1¹¹ ATP-binding cassette transporter G1
a membrane-spanning pump that moves cholesterol and phospholipids from the inner leaflet of cell membranes onto maturing HDL particles, completing the second step of reverse cholesterol transport after ABCA1 initiates lipid loading onto nascent HDL) encodes one of the body's principal cholesterol efflux transporters. Located on chromosome 21q22.3, ABCG1 is expressed in macrophages, liver, and many other tissues, where it loads mature HDL particles with surplus cellular cholesterol for transport back to the liver — a central step in preventing foam cell formation and atherosclerotic plaque development.

rs4148102 is an intronic variant in ABCG1 that has no known effect on the protein sequence itself, but its location within an intron has raised the possibility of subtle effects on ABCG1 splicing, expression, or its response to dietary lipid signals. What distinguishes this variant is not its baseline effect on cholesterol but the way it conditions the body's response to high polyunsaturated fatty acid (PUFA) intake — producing a counterintuitive pattern where a seemingly heart-healthy dietary pattern raises LDL-cholesterol in AA homozygotes.

The Mechanism

The biological basis for this gene-diet interaction is not fully characterized at the molecular level. However, ABCG1 transcription is under LXR²² LXR
liver X receptor — a nuclear receptor activated by oxysterols and certain fatty acid derivatives; once activated, LXR drives expression of ABCG1, ABCA1, and other cholesterol homeostasis genes control. Polyunsaturated fatty acids and their metabolites serve as LXR ligands and can modulate its activity. An intronic variant could influence how effectively the ABCG1 gene responds to these dietary lipid signals — for example, by altering a regulatory element that fine-tunes LXR responsiveness.

When ABCG1 function is subtly impaired or mis-regulated, cholesterol efflux from cells to HDL is reduced. Under high-PUFA dietary conditions, which normally promote LDL receptor upregulation and LDL clearance, the AA variant appears to interfere with this adaptive response, resulting in paradoxically elevated LDL and total cholesterol rather than the reduction seen in GG carriers on the same diet.

The Evidence

The primary evidence comes from a study by Abellán et al.³³ study by Abellán et al.
Abellán R et al. Dietary polyunsaturated fatty acids may increase plasma LDL-cholesterol and plasma cholesterol concentrations in carriers of an ABCG1 gene single nucleotide polymorphism: study in two Spanish populations. Atherosclerosis, 2011 examining 1,941 participants across two independent Spanish cohorts (the Hortega study, n=1,178, and the Pizarra study, n=763). In the Hortega population, AA homozygotes consuming high-PUFA diets had LDL-cholesterol of 149.8 ± 37.9 mg/dL compared to 111.4 ± 32.1 mg/dL in G allele carriers (p=0.005). Total cholesterol diverged similarly (242.1 vs 198.0 mg/dL, p=0.003). Pooling both cohorts strengthened the signal: gene-diet interaction p=0.006 for total cholesterol, p=0.003 for LDL-cholesterol.

The A allele is relatively uncommon globally (~14.5%), making AA homozygosity rare (~2% of the population). This limits replication opportunities and explains why no dedicated follow-up trials exist yet. The evidence level is therefore emerging — a well-designed two-cohort study, but not yet replicated in independent populations or mechanistically confirmed in cell-based assays.

Practical Actions

For AA homozygotes, the clinical implication is specific: high-PUFA diets — which most guidelines recommend as beneficial — may actually raise LDL-cholesterol in this genotype. Rather than increasing total PUFA from vegetable oils (sunflower, corn, safflower), focus on pre-formed long-chain omega-3s (EPA and DHA from fatty fish or supplements) and monitor fasting LDL when making significant dietary changes. Saturated fat should still be limited — this is not a signal to increase saturated fat intake. The issue is specifically with high omega-6 PUFA loads from vegetable oils, not with EPA/DHA.

Carriers of one A allele (AG) represent roughly 25% of people. The gene-diet interaction was strongest in AA homozygotes; AG heterozygotes showed intermediate patterns in some analyses, but the effect was not consistent across both study populations. Standard dietary PUFA guidance applies.

Interactions

ABCG1's role in cholesterol efflux depends on the upstream ABCA1 step (rs1044317 is another ABCG1 variant in the cholesterol_lipoproteins category). If both ABCG1 steps in the efflux pathway are impaired — the initial ABCA1-mediated lipid loading onto nascent HDL, and the ABCG1-mediated maturation step — the combined cholesterol efflux deficit could be larger than either variant alone. FADS1 variants (rs174547, rs174537) also interact with this locus biologically: impaired FADS1 conversion of plant omega-3s to EPA/DHA shifts the circulating PUFA ratio toward omega-6, which may amplify the LDL-raising signal seen with rs4148102 AA on high-PUFA diets.