rs2524299 — FADS2

FADS2 rs2524299 — An Independent Regulatory Signal for Delta-6 Desaturase

The FADS gene cluster on chromosome 11 contains dozens of variants that affect how efficiently your body converts short-chain dietary fats into long-chain polyunsaturated fatty acids (LC-PUFAs) such as arachidonic acid, EPA, and DHA. Most of these variants travel together in a single large block of linkage disequilibrium¹¹ linkage disequilibrium
A genomic region where specific allele combinations are inherited together more often than expected by chance; variants in one LD block are effectively surrogates for each other. rs2524299 is notable because it does not belong to that primary block. It sits within a distinct regulatory region of FADS2 intron 1 — what researchers call Block 2 — and captures an independent regulatory signal that is not covered by the other FADS2 variants already on the platform (rs174568 and rs174575).

The Mechanism

rs2524299 is one of ten SNPs defining the Block 2 haplotype in FADS2 intron 1, a conserved locus containing predicted binding sites for SREBP and PPARγ²² SREBP and PPARγ
Sterol regulatory element binding protein and peroxisome proliferator-activated receptor gamma — two transcription factors that regulate lipid and fatty acid metabolism. Carriers of the minor haplotype (tagged by the T allele at rs2524299) show lower basal expression of both FADS1 and FADS2 in liver tissue. Because FADS2 encodes delta-6 desaturase (D6D) — the rate-limiting enzyme that initiates conversion of linoleic acid (LA) to gamma-linolenic acid (GLA), and alpha-linolenic acid (ALA) to stearidonic acid (SDA) — reduced expression compresses both the omega-6 and omega-3 elongation pathways simultaneously.

The result is the same substrate-product inversion seen across the FADS cluster: T allele carriers accumulate short-chain precursors (LA, ALA) while producing less of the long-chain end-products (arachidonic acid, EPA, DHA) for a given dietary intake.

Importantly, this Block 2 haplotype is not in linkage disequilibrium with the primary FADS cluster haplotype³³ this Block 2 haplotype is not in linkage disequilibrium with the primary FADS cluster haplotype
Meaning that rs2524299 and rs174568 or rs174575 can be inherited independently; a person can carry both risk haplotypes simultaneously, or the Block 2 risk allele without the primary FADS risk allele. This independence means rs2524299 provides additive information about FADS2 regulation beyond what the other FADS2 variants in the database capture.

The Evidence

rs2524299 was examined alongside five other common FADS polymorphisms in the Costa Rica Study of fatty acid desaturase gene variants and myocardial infarction⁴⁴ Costa Rica Study of fatty acid desaturase gene variants and myocardial infarction
Aslibekyan et al. 2012, Front Genet — 1,756 Costa Rican adults in a matched case-control design, with replication in the Nurses' Health Study and Health Professionals Follow-Up Study. Genetic variation across the FADS cluster — including rs2524299 — was associated with a robust linear decrease in adipose gamma-linolenic acid, arachidonic acid, and eicosapentaenoic acid. The minor allele consistently predicted lower concentrations of these long-chain products in adipose tissue fatty acid profiles.

An earlier Costa Rica Study analysis by Baylin et al. 2007⁵⁵ Baylin et al. 2007
alpha-Linolenic acid, Delta6-desaturase gene polymorphism, and the risk of nonfatal myocardial infarction; Am J Clin Nutr examined 1,694 case-control pairs and found that FADS2 intron/promoter variants in this region were associated with lower adipose EPA and arachidonic acid, consistent with impaired ALA-to-EPA conversion. The intron 1 regulatory locus was specifically associated with variation in delta-6 desaturase activity.

The functional architecture of this regulatory locus was characterized by Reardon et al. 2012⁶⁶ Reardon et al. 2012
Insertion-Deletions in a FADS2 Intron 1 Conserved Regulatory Locus Control Expression of Fatty Acid Desaturases 1 and 2 and Modulate Response to Simvastatin; Prostaglandins Leukot Essent Fatty Acids, which showed that the Block 2 haplotype (containing rs2524299) controls basal expression of both FADS1 and FADS2 in liver cells. Minor haplotype homozygotes showed significantly lower basal FADS1 expression and, paradoxically, 20–40% greater upregulation of FADS1 and FADS2 in response to simvastatin — suggesting this locus participates in statin-mediated lipid regulation.

The broader evidence base for FADS cluster variants affecting LC-PUFA synthesis was confirmed in a systematic review of 132 studies including ~500,000 participants⁷⁷ systematic review of 132 studies including ~500,000 participants
Visioli et al. 2026, Food Funct, showing that minor allele carriers across the FADS cluster show approximately 40–60% lower LC-PUFA conversion efficiency, with 14 studies demonstrating significant gene-by-diet interactions.

Practical Actions

For T allele carriers at rs2524299, the practical implication mirrors the other FADS2 impaired-conversion genotypes: plant-based omega-3 sources (flaxseed, chia, walnuts) supply ALA, but the first conversion step — ALA to stearidonic acid via FADS2 — is reduced by this haplotype. Preformed EPA and DHA from marine or algae-based sources bypass the impaired step entirely. TT homozygotes (the most impaired group, ~3% globally but ~17% in East Asian populations) should prioritize 2–4 g combined EPA+DHA daily; AT heterozygotes benefit from 1–2 g daily.

One clinically relevant interaction with medications: carriers of the Block 2 minor haplotype show enhanced FADS1 and FADS2 upregulation in response to statins and LXR agonists. This suggests that statin therapy may partially compensate for the reduced basal desaturase expression in this genotype — though this finding is preliminary and does not change the core supplementation strategy.

Interactions

rs2524299 is in linkage disequilibrium with rs2727270 and rs2727271 (Block 2 haplotype partners) but is independent of rs174568 and rs174575 (the primary FADS2 LD block). A person carrying T alleles at both rs2524299 and T alleles at rs174568 or rs174575 faces additive impairment of FADS2 expression from two independent regulatory mechanisms — a situation that would produce more severe LC-PUFA deficiency than either variant alone. Check related SNPs rs174568 and rs174575 for a full picture of your FADS2 regulatory status.