The relationship between different stages of diabetic retinopathy and levels of YKL-40 in aqueous humour and serum.

Clinical relevance: Since inflammation plays an important role in the pathogenesis of diabetic retinopathy, serum biomarkers and retinal imaging aimed at evaluating the presence of inflammation have emerged as useful tools to monitor the appearance and progression of diabetic retinopathy.

Background: This study aims to investigate the value of YKL-40 levels in patients with diabetes mellitus with different stages of diabetic retinopathy and without diabetic retinopathy, and to compare those findings with results from healthy individuals without diabetes mellitus.

Methods: This prospective cross-sectional study included 67 diabetic patients with or without diabetic retinopathy who underwent cataract surgery and 23 patients (control group) having no ocular and systemic disease other than senile cataract. Participants with diabetes mellitus were separated into three subgroups: the first group consisted of 26 patients without diabetic retinopathy, the second group included 21 patients with non-proliferative diabetic retinopathy and the third group included 20 patients with proliferative diabetic retinopathy. Serum and aqueous humour YKL-40 levels were analysed and compared between the groups.

Results: The mean serum (p < 0.001) and aqueous humour (p < 0.001) YKL-40 levels were statistically significantly lower in control subjects compared to patients with diabetes mellitus. The aqueous humour YKL-40 levels showed statistically significant elevations with the progression of diabetic retinopathy. Duration of diabetes mellitus was significantly correlated with aqueous humour YKL-40 levels (p = 0.001, r = 0.384).

Conclusion: Both serum and aqueous humour YKL-40 levels are higher in patients with diabetes mellitus compared to healthy subjects. Levels of YKL-40 in aqueous humour increase with the progression of diabetic retinopathy.