Integrated intraocular–plasma proteomics reveals conserved biomarkers for diabetic retinopathy progression: a multi-fluid biopsy study

Aims/hypothesis: The aim of this study was to identify conserved biomarkers for diabetic retinopathy progression, addressing the lack of minimally invasive biomarkers to track the entire continuum of diabetic retinopathy. Methods: We conducted high-throughput proteomics (SomaScan v4.1) on aqueous humour from the Guangdong DR Multiple-Omics Study (n=32). Temporal protein clusters were identified using soft clustering of temporal trajectories. Candidates were validated in a US dataset and localised via single-cell RNA-seq in an oxygen-induced retinopathy mouse model. The clinical relevance of plasma-detectable markers was assessed cross-sectionally and prospectively in individuals with diabetes from the UK Biobank (n=2495). Results: In the discovery dataset (mean age 68.5±9.0 years; 56.3% men, 43.8% women), temporal proteomic profiling identified 40 candidate biomarkers whose concentration showed monotonic changes during diabetic retinopathy progression. Of these, 25 showed conserved directional patterns in the validation dataset (17 increasing and eight decreasing, all p<0.05). Single-cell mapping further localised 15 candidates, including neurofilament light chain (NFL), to retinal neurons and glia. In the UK Biobank individuals, baseline plasma NFL distinguished those with diabetic retinopathy from control individuals (OR 1.98 [95% CI 1.61, 2.42]) and predicted incident diabetic retinopathy (HR 2.01 [95% CI 1.48, 2.73]) and vascular complications (microvascular, HR 2.28 [95% CI 1.94, 2.69]; macrovascular, HR 1.49 [95% CI 1.26, 1.77]) over a median follow-up of 12 years. Plasma NFL enhanced the predictability of a conventional risk factor model for diabetic retinopathy (net reclassification improvement [NRI] 0.194 [95% CI 0.042, 0.297]; integrated discrimination improvement [IDI] 0.015 [95% CI 0.003, 0.047]) and enabled risk stratification of vascular complications. Conclusions/interpretation: NFL represents a pan-stage biomarker for diabetic retinopathy progression, detectable through minimally invasive plasma testing, and is associated with risks of diabetic vascular complications.