rs2241766 — ADIPOQ T45G

Adiponectin's Silent Variant — When a Synonymous Change Isn't Silent

Adiponectin is the most abundant hormone secreted by fat cells, and despite being produced in adipose tissue it works against the pathological consequences of excess fat: it sensitizes muscle and liver to insulin, suppresses the inflammatory cytokines that drive adipose tissue fibrosis, and inhibits the TGF-β signaling that converts healthy fat lobules into fibrotic tissue. The rs2241766 variant — also known as +45T>G or T45G — sits in exon 2 of the ADIPOQ gene and encodes a synonymous change¹¹ synonymous change
the codon change from ACC to GCC still encodes glycine at position 15; no amino acid change occurs. Yet decades of research have linked this "silent" variant to measurable differences in adiponectin levels, fat distribution, metabolic syndrome risk, and cardiovascular outcomes.

The reason a synonymous SNP matters here is twofold: first, it may alter mRNA stability or ribosomal codon usage²² mRNA stability or ribosomal codon usage
synonymous mutations can change how quickly the mRNA is degraded or translated without changing the protein sequence; different codons are read at different speeds by the ribosome, subtly changing how much adiponectin protein is made. Second, and more intriguingly, rs2241766 sits within the third exon of ADIPOQ-AS³³ ADIPOQ-AS
a long non-coding RNA transcribed from the antisense strand of the ADIPOQ gene; it inhibits adipogenesis by forming a duplex with ADIPOQ mRNA that suppresses translation — the antisense lncRNA that regulates adiponectin translation itself. A single nucleotide change affecting both molecules simultaneously helps explain why this variant's effects are real but sometimes inconsistent across populations.

The Mechanism

Adiponectin is secreted exclusively by adipocytes and circulates in three oligomeric forms: low molecular weight trimers, medium molecular weight hexamers, and high molecular weight (HMW) multimers⁴⁴ high molecular weight (HMW) multimers
the HMW form is the most insulin-sensitizing and anti-inflammatory; its ratio to total adiponectin is a stronger predictor of metabolic health than total adiponectin alone. The protein acts primarily through two receptors: AdipoR1 in skeletal muscle, which activates AMPK and increases fatty acid oxidation and glucose uptake, and AdipoR2 in liver, which activates PPARα and reduces hepatic glucose output. Both pathways converge on reduced insulin resistance.

The anti-fibrotic role of adiponectin is increasingly recognized as central to adipose tissue health. Adiponectin suppresses TGF-β/Smad signaling⁵⁵ suppresses TGF-β/Smad signaling
the TGF-β pathway drives fibroblast activation and collagen deposition; adiponectin blocks this by activating AMPK, which phosphorylates and inactivates Smad proteins, reduces myofibroblast differentiation, and limits collagen type I deposition. In adipose tissue, this anti-fibrotic function helps maintain the structural integrity of fat lobules and limits the pathological remodeling seen in conditions of chronic adipose tissue inflammation.

The rs2241766 G allele, while not altering the adiponectin protein sequence, appears to modestly reduce adiponectin secretion through mRNA-level mechanisms. In a study of metabolic syndrome patients, GG homozygotes had adiponectin levels of 14.5 ± 4.3 mg/mL compared to 18.4 ± 4.7 mg/mL in TT homozygotes⁶⁶ GG homozygotes had adiponectin levels of 14.5 ± 4.3 mg/mL compared to 18.4 ± 4.7 mg/mL in TT homozygotes
serum adiponectin measured in Jordanian metabolic syndrome patients and controls; units are mg/mL = μg/mL in some papers — a 21% reduction. Results vary by population, with some studies showing the opposite direction in certain ethnic groups, consistent with the variant acting as a tag for different haplotypes in different ancestries.

The Evidence

The most consistent evidence links rs2241766 G allele carriage to elevated metabolic risk across multiple conditions:

Metabolic syndrome: The TG and GG genotypes of rs2241766 were associated with significantly elevated metabolic syndrome risk compared to TT (OR = 1.32 and OR = 2.31, respectively) in a case-control analysis. The GG genotype was 40.1% among metabolic syndrome patients versus 16.1% among controls⁷⁷ The GG genotype was 40.1% among metabolic syndrome patients versus 16.1% among controls
study of Jordanian adults; MetS defined by IDF criteria.

Obesity: A meta-analysis of 18 case-control studies encompassing 5,843 participants⁸⁸ meta-analysis of 18 case-control studies encompassing 5,843 participants
PLOS One, 2014; included studies from China, Europe, Latin America, and the Middle East found the GG genotype significantly associated with obesity (OR = 1.39, 95% CI: 1.11–1.73). The effect was driven by Chinese populations (OR = 1.54) and not significant in non-Chinese studies, suggesting population-specific linkage disequilibrium patterns.

Cardiovascular disease: A 2018 meta-analysis of 65 studies (19,106 CVD cases, 31,629 controls)⁹⁹ 2018 meta-analysis of 65 studies (19,106 CVD cases, 31,629 controls)
Lipids in Health and Disease; searched through July 2017 found rs2241766 significantly associated with cardiovascular disease in allelic, dominant, recessive, heterozygote, and homozygote models. This was in contrast to rs1501299, which was not associated with CVD in this same analysis. A 2012 meta-analysis of 37 studies¹⁰¹⁰ 2012 meta-analysis of 37 studies
BMC Medical Genetics; association between adiponectin gene polymorphisms and CVD similarly implicated rs2241766 and rs266729 as the ADIPOQ SNPs most consistently associated with cardiovascular risk.

Fat distribution: A cross-sectional study in 242 Mexican-Mestizo subjects found that the rs2241766 +45G allele could be associated with distribution of body fat storage in obesity¹¹¹¹ rs2241766 +45G allele could be associated with distribution of body fat storage in obesity
the SNP showed significant correlations with fat distribution patterns independent of overall BMI, even though it was not associated with BMI per se. This fat-distribution rather than fat-quantity effect aligns with adiponectin's known role in regulating the quality and inflammatory state of adipose tissue rather than simply its mass.

Gene-diet interaction: The MARINA study¹²¹² MARINA study
Modulation of Atherosclerosis Risk by Increasing Doses of n3 Fatty Acids; RCT of 142 men and 225 women ages 45–70 assigned to varying EPA+DHA doses found that rs2241766 TT homozygotes over age 58 had significantly increased serum adiponectin after omega-3 supplementation at 1.8 g/day EPA+DHA (22% increase; P = 0.008). The interaction between genotype, treatment, and age was nominally significant (P = 0.029), and the researchers specifically recommended omega-3 supplementation for older TT carriers who face higher risk of hypoadiponectinemia.

Practical Actions

The key takeaway from the evidence base for rs2241766 is that the G allele, when present in two copies, associates with lower adiponectin and elevated metabolic and cardiovascular risk. Since adiponectin cannot be directly supplemented, strategies must focus on factors that modulate its secretion and signaling. Omega-3 fatty acids (EPA and DHA) activate PPARγ, which upregulates ADIPOQ transcription, and the MARINA trial data specifically supports this approach for individuals at risk of hypoadiponectinemia. For heterozygotes, the effect is intermediate and monitoring adiponectin levels provides a personalized baseline from which to assess the need for intervention. Monitoring fasting insulin and HOMA-IR tracks the downstream consequence of reduced adiponectin signaling.

Interactions

rs2241766 is one of four extensively studied ADIPOQ variants that collectively define the haplotypic architecture of this locus: rs17300539 (−11391G>A, promoter), rs266729 (−11377C>G, promoter), rs2241766 (+45T>G, exon 2), and rs1501299 (+276G>T, intron 2). These variants are in partial linkage disequilibrium and are often studied as haplotypes. The 2018 cardiovascular meta-analysis found that rs2241766 and rs266729 — but not rs1501299 — were independently associated with CVD risk, suggesting these two SNPs capture independent risk signals.

An important note for interpretation: rs2241766 sits within the third exon of the ADIPOQ-AS antisense lncRNA, which forms an mRNA duplex with ADIPOQ mRNA and suppresses its translation. The variant may therefore affect adiponectin regulation through two convergent mechanisms — altered mRNA stability of the sense strand, and altered function of the antisense regulatory transcript. This dual mechanism may contribute to the population-specific inconsistency of association results across studies.

In individuals carrying G-allele variants at multiple ADIPOQ loci (rs266729 and rs2241766), the combined reduction in adiponectin signaling may be greater than either variant alone. Such combined carriage would warrant more aggressive monitoring of metabolic biomarkers and stronger emphasis on omega-3 supplementation as the primary evidence-backed intervention for raising adiponectin.