rs6947337 — INHBA

Activin A: The Adipose Tissue Signal Linking Fat Storage to Inflammation

INHBA encodes the beta-A subunit of activin A¹¹ activin A
Activin A is a homodimer of beta-A subunits belonging to the TGF-beta superfamily. It regulates cell proliferation, differentiation, and immune responses across multiple tissues, a TGF-beta superfamily member that plays a central role in adipocyte biology. The rs6947337 variant lies in an intergenic region approximately 110 kb downstream of INHBA on chromosome 7p14.1 and was identified as a novel shared risk locus between migraine and type 2 diabetes.

The Mechanism

Activin A controls the fate of adipose tissue precursor cells. It is highly expressed in adipocyte progenitors but drops sharply as cells differentiate into mature fat cells. By inhibiting differentiation through the C/EBP-beta-LAP and SMAD2 pathway, activin A keeps precursors in a proliferative state rather than allowing them to become functional adipocytes. ²² This autocrine/paracrine mechanism means activin A from existing precursors inhibits neighboring cells from differentiating, creating a self-regulating feedback loop

In obesity, this system goes awry. Macrophages infiltrating adipose tissue secrete factors that dramatically increase activin A production, creating a pro-fibrogenic, pro-inflammatory environment. This prevents healthy adipose tissue expansion (hyperplasia) and instead promotes unhealthy fat cell enlargement (hypertrophy), leading to insulin resistance and systemic inflammation. The inflammatory cascade also affects vascular endothelium and neuroinflammation pathways implicated in migraine.

The Evidence

The cross-trait GWAS³³ cross-trait GWAS
Siewert-Rocks et al. Genetic Overlap Analysis Identifies a Shared Etiology between Migraine and Headache with Type 2 Diabetes. Genes, 2022 identified rs6947337 near INHBA as one of 23 novel shared loci between migraine and T2D (P = 3.90 x 10^-8), with concordant protective effects for the G allele (migraine OR 0.98, T2D OR 0.98).

Laboratory evidence strongly supports the activin-adipose connection. Zaragosi et al.⁴⁴ Zaragosi et al.
Activin A plays a critical role in proliferation and differentiation of human adipose progenitors. Diabetes, 2010 demonstrated that activin A autocrine signaling is essential for adipose progenitor biology. Subsequent work showed that activin receptor ALK4⁵⁵ activin receptor ALK4
Zamani and Brown. Activin receptor ALK4 promotes adipose tissue hyperplasia by suppressing differentiation of adipocyte precursors. Stem Cell Reports, 2022 promotes adipose tissue hyperplasia by suppressing precursor differentiation. Supporting the pathway's clinical relevance, rare loss-of-function variants in the related gene INHBE were shown to protect from abdominal obesity⁶⁶ protect from abdominal obesity
Deuchler et al. Nat Commun, 2022.

The A allele is notably common across populations (40% in Europeans, 67% in East Asians), meaning a large proportion of the population carries at least one copy.

Practical Actions

The INHBA locus variant affects how adipose tissue responds to metabolic stress. Carriers of the A allele may benefit from interventions that reduce adipose tissue inflammation and support healthy adipocyte function, particularly EPA omega-3 which has direct anti-inflammatory effects on adipose tissue macrophages.

Interactions

Activin A signaling interacts with the broader TGF-beta pathway, which includes the SKI gene (rs11590235). Carriers with risk alleles at both loci may have compounding dysregulation of TGF-beta superfamily signaling affecting both adipose tissue function and vascular inflammation. The activin pathway also intersects with PPARG-mediated adipocyte differentiation, linking to rs1801282 (PPARG Pro12Ala).