Serum Urate and Renal Dysfunction: Bidirectional Genetic Associations, External Validation, and Exploratory Multi-Omics Characterization of Antithrombin (SERPINC1) in Hyperuricemic Nephropathy

Background: Hyperuricemic nephropathy (UAN) involves a systemic thromboinflammatory axis, yet the role of antithrombin (AT, SERPINC1) remains incompletely defined. While AT has anticoagulant and anti-inflammatory properties, whether it contributes to UAN as a disease-responsive molecular node remains uncertain. Methods: We integrated two-sample MR of serum urate and renal traits with complementary sensitivity analyses, cis-eQTL and pQTL analyses of SERPINC1, and exploratory transcriptomic, proteomic, metabolomic, and coexpression analyses. The available data were used to assess genetic associations and to distinguish genetic evidence from cross-dataset molecular patterns. Results: Genetically predicted serum urate showed positive or negative associations with BUN and eGFR, respectively, but the primary analyses showed substantial heterogeneity. Reverse-direction estimates were also associated with serum urate, representing reciprocal genetic relationships between related renal traits and urate rather than proof of a temporal feedback cycle. Available data did not demonstrate mediation through genetically predicted whole-blood SERPINC1 expression. Three deCODE cis-pQTL instruments gave inconsistent renal estimates: nominally lower BUN (β = −0.0290, p = 0.047), null eGFR (β = −0.0036, p = 0.472), and higher CKD risk (β = +0.3361, p = 0.020) with directional pleiotropy evidence. Exploratory multi-omics analyses showed higher PBMC SERPINC1 expression during acute gout and a nominal urinary proteomic difference that did not survive multiple-testing correction (FDR = 0.998). Conclusions: SERPINC1 is best interpreted as a responsive molecular feature requiring further validation, rather than as a demonstrated genetic mediator or renal-protective therapeutic target. The transcriptomic and urinary findings represent cross-dataset, stage-associated observations and should not be interpreted as proven sequential phases.