Serum glial fibrillary acidic protein and neurofilament light chain as biomarkers of retinal neurodysfunction in early diabetic retinopathy: results of the EUROCONDOR study.

AIMS: Neurodegeneration and glial activation are primary events in the pathogenesis of diabetic retinopathy. Serum glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) are biomarkers of underlying neuroinflammatory and neurodegenerative disease processes. The aim of the present study was to assess the usefulness of these serum biomarkers for the identification and monitoring of retinal neurodysfunction in subjects with type 2 diabetes. METHODS: A case-control study was designed including 38 patients from the placebo arm of the EUROCONDOR clinical trial: 19 with and 19 without retinal neurodysfunction assessed by multifocal electroretinography. GFAP and NfL were measured by Simoa. RESULTS: Serum levels of GFAP and NfL directly correlated with age (r = 0.37, p = 0.023 and r = 0.54, p < 0.001, respectively). In addition, a direct correlation between GFAP and NfL was observed (r = 0.495, p = 0.002). Serum levels of GFAP were significantly higher at baseline in those subjects in whom neurodysfunction progressed after the 2 years of follow-up (139.1 ± 52.5 pg/mL vs. 100.2 ± 54.6 pg/mL; p = 0.04). CONCLUSIONS: GFAP could be a useful serum biomarker for retinal neurodysfunction. Monitoring retinal neurodysfunction using blood samples would be of benefit in clinical decision-making. However, further research is needed to validate this result as well as to establish the best cutoff values.