Integrative Proteogenomic Analysis Identifies Genetically Supported Plasma Proteins, Metabolites, and Pathways in...

Glaucoma is a leading cause of irreversible blindness, yet the circulating proteins and metabolic pathways that causally contribute to different glaucoma subtypes remain poorly defined.

We analyzed baseline plasma proteomics in 1485 glaucoma cases (447 primary open‑angle glaucoma [POAG], 177 primary angle-closure glaucoma [PACG], 120 normal-tension glaucoma [NTG]) in the UK Biobank using Cox models with graded adjustment. We then integrated five independent protein quantitative trait loci resources with FINLAND R12 genome-wide association study data to perform two‑sample Mendelian randomization (MR) and cross‑cohort meta‑analysis for overall glaucoma and each subtype. To prioritize effector genes and pathways, we conducted summary-data-based Mendelian randomization (SMR) using eQTLGen and two‑step mediation MR using metabolite quantitative trait loci data for ∼1400 plasma metabolites from the Canadian Longitudinal Study on Aging cohort.

In fully adjusted Cox models, 484 proteins were associated with incident glaucoma, 135 with NTG, 59 with POAG, and 1 with PACG (false discovery rate <0.05). Multicohort MR and meta‑analysis identified eight proteins with robust causal effects: NRP2, TSPAN1, and HAVCR2 for overall glaucoma; NRXN3 for PACG; MANSC4 for NTG; and LTBP2, CD69, and SMAD1 for POAG. SMR supported NRP2 (overall glaucoma) and SMAD1 (POAG) as causal genes. Mediation MR revealed that sphingomyelins, acylcarnitines, and bile acid-related metabolites partially mediated the effects of several proteins, defining shared (e.g., sphingolipid) and subtype‑specific metabolic pathways.

By integrating epidemiologic, proteomic, genetic, and metabolomic data, we identify convergent systemic protein and metabolic signatures associated with glaucoma susceptibility and its clinical subtypes. These findings nominate NRP2, SMAD1, and related pathways as promising biomarkers and therapeutic targets and support a systems‑level view of glaucoma pathogenesis beyond intraocular pressure alone.