Cross-scale genetic, molecular, and cellular triangulation prioritizes ACSL5 as a T3-responsive candidate linking hypothyroidism liability to anemia.

Abstract

Purpose: Anemia is a recognized complication of hypothyroidism, but disease-level genetic studies have not identified a clear erythroid cell-intrinsic target. We integrated genetic validation, molecular-QTL prioritization, and replicated triiodothyronine (T3)-responsive erythroid experiments to identify candidates linking hypothyroidism liability to anemia.

Materials and methods: Two-sample Mendelian randomization (MR) assessed genetically predicted hypothyroidism and anemia. Source metadata were reviewed for possible sample overlap, and two cross-biobank forward validations were performed. Strict reverse MR used the original OpenGWAS identifiers; because anemia provided no genome-wide-significant instruments, a post hoc analysis used p < 5 × 10^-6. Non-major histocompatibility complex (MHC) methylation summary-based Mendelian randomization (SMR) and whole-blood expression SMR were integrated, followed by a public fine-mapping/colocalization lookup for two acyl-CoA synthetase long-chain family member 5 (ACSL5) cytosine-phosphate-guanine (CpG) sites and the ACSL5 eQTL. ACSL5 was examined in three independent hemin-induced K562, a human chronic myelogenous leukemia cell line experiments with or without T3; Triacsin C and oleic acid-bovine serum albumin (BSA) served as pathway-level perturbations.

Results: Primary inverse-variance weighted (IVW) analysis associated hypothyroidism liability with higher anemia odds (OR = 1.0304; 95% CI, 1.0195-1.0414; p = 3.42 × 10^-8). Both primary genome-wide association studies (GWASs) were UK Biobank-derived, and their exact participant overlap could not be determined from public summary-level information. A participant-independent FinnGen hypothyroidism-to-UK Biobank anemia validation reproduced the positive direction (28 instruments; IVW beta = 0.001448, p = 4.14 × 10^-4); the complementary UK Biobank hypothyroidism-to-FinnGen anemia analysis was also positive. Strict original-ID reverse MR was not estimable; the exploratory eight-instrument analysis was null and heterogeneous. Six non-MHC CpGs passed Bonferroni correction, including two mapped to ACSL5, while whole-blood ACSL5 expression showed an inverse SMR estimate. The public lookup returned no pairwise CpG-expression colocalization. In all three K562 experiments, hemin plus T3 increased HBA1, HBA2, GYPA, and ACSL5 expression. Triacsin C suppressed erythroid-marker expression, whereas oleic acid-BSA produced a partial increase without exogenous T3.

Conclusion: Cross-scale evidence prioritizes ACSL5 as a T3-responsive candidate linking hypothyroidism liability to anemia and implicates long-chain fatty-acid handling as a research direction. However, negative CpG-expression colocalization and nongene-specific pharmacological interventions preclude a mechanistic conclusion. Direct ACSL5 perturbation and primary erythroid-cell validation are required.