Profile of intraocular tumour necrosis factor‐α and interleukin‐6 in diabetic subjects with different degrees of diabetic retinopathy

Purpose: To assess and correlate the levels of inflammatory mediators in the eyes from non‐diabetic and diabetic subjects without retinopathy (NDR), with non‐proliferative diabetic retinopathy (NPDR) or with proliferative diabetic retinopathy (PDR) to corresponding erum levels. Methods: The levels of interleukin 1β, interleukin‐6 (IL‐6) and tumour necrosis factor‐α (TNF‐α) were analysed by an ELISA‐mimicking technique in the vitreous from 26 diabetic subjects with active PDR and 27 non‐diabetic subjects, or by a multiplex bead assay in the aqueous humour from 35 diabetic subjects with NDR/NPDR and 40 non‐diabetic subjects. Intraocular protein production was estimated in vitreous specimens by calculating a vitreous/serum ratio. Results: In the vitreous, IL‐6 was higher in diabetic 157.5 (25.0–1401.0) pg/ml; median (min–max)] than in non‐diabetic subjects 44.0 (5.0–4425) pg/ml; p = 0.021]. The vitreous/serum ratio was high (55.5:1 and 16:1, respectively), suggesting intraocular production. TNF‐α was lower in diabetic 18.0 (8.0–46.0) pg/ml] than in non‐diabetic subjects 22.0 (13.0–47.0) pg/ml; p = 0.034], but the vitreous/serum ratio was elevated in both groups (2:1 and 3.4:1, respectively). TNF‐α levels were higher in serum from diabetic subjects 9.0 (5.0–53.0) pg/ml versus 6.7 (3.0–11.0) pg/ml; p < 0.001]. Aqueous levels of inflammatory mediators did not differ between diabetic subjects with NDR/NPDR and non‐diabetic subjects despite elevated TNF‐α in serum 27.8 (6.8–153.7) pg/ml versus 16.4 (4.1–42.4) pg/ml; p = 0.021]. Conclusion: Intraocular inflammation seems to be involved in PDR but does not seem to be prominent in early retinopathy stages, i.e. NDR or NPDR. Diabetic subjects have an overall increased inflammatory activity compared to non‐diabetic subjects, as demonstrated by increased serum levels of TNF‐α.