Increased melatonin levels in aqueous humor of patients with proliferative retinopathy in type 2 diabetes mellitus.
OBJECTIVE
To report the association between melatonin levels in aqueous humor and serum, and diabetic retinopathy (DR) grade in type 2 diabetic patients.


METHODS
Aqueous humor and plasma samples from 26 patients with DR (in nonproliferative and proliferative stages) and 14 control subjects were collected during cataract surgery after 6 p.m. Melatonin concentrations were determined using an enzyme-linked immunosorbent assay (ELISA).


RESULTS
Melatonin levels were significantly higher in the aqueous humor of patients with proliferative diabetic retinopathy (PDR) [18.57±2.67 pg/mL (range 15.20-23.06) vs 13.63±2.71 pg/mL (range 10.20-20.20), P=0.0001], but not in those with nonproliferative retinopathy (NPDR) [13.79±2.56 pg/mL (range 9.80-20.10) vs 13.63±2.71 pg/mL (range 10.20-20.20), P=0.961] compared to controls. There was decrement in the plasma melatonin level of patients with PDR, but no significant differences between the plasma melatonin levels of the study groups [5.37±1.74 pg/mL (range 2.85-8.65) vs 6.11±1.90 pg/mL (range 3.13-9.41), P=0.293], or between control and DR groups [NPDR 6.11±1.90 pg/mL (range 3.13-9.41) vs control 6.15±1.91 pg/mL (range 2.18-9.86); PDR (5.37±1.74 pg/mL (range 2.85-8.65) vs control 6.15±1.91 pg/mL (range 2.18-9.86), P=0.808, P=0.264].


CONCLUSIONS
Elevated melatonin levels in aqueous humor in PDR may indicate the level to be associated with DR severity.
Izmir Katip Celebi University, Faculty of Medicine, Ophthalmology, Izmir 35620, Turkey.
Erdinc
E
Aydin
Gaziosmanpasa University Faculty of Medicine, Biochemistry, Tokat 60250, Turkey.
Semsettin
S
Sahin
aqueous humor; diabetes mellitus; diabetic retinopathy; melatonin