Aqueous levels of macrophage migration inhibitory factor and monocyte chemotactic protein‐1 in patients with diabetic retinopathy

Aims  To investigate the relationship of aqueous macrophage migration inhibitory factor (MIF) and monocyte chemotactic protein-1 (MCP-1) levels with the clinical stage of diabetic retinopathy. Methods  We assayed MIF and MCP-1 levels in aqueous humour samples obtained from 40 diabetic patients (49 eyes) and 24 non-diabetic patients (31 eyes) using enzyme-linked immunosorbent assay. According to the clinical stage of diabetic retinopathy, the diabetic patients were classified into non-diabetic retinopathy (11 eyes), non-proliferative diabetic retinopathy (14 eyes) and proliferative diabetic retinopathy (24 eyes). Results  The aqueous levels of MIF (mean ± sd) were 6.34 ± 4.53 ng/ml in proliferative diabetic retinopathy, 3.22 ± 1.71 ng/ml in non proliferative diabetic retinopathy, 1.25 ± 0.96 ng/ml in non-diabetic retinopathy and 1.07 ± 0.94 ng/ml in non-diabetic patients. Significant differences were found among these four groups (P < 0.0001). Aqueous MCP-1 levels were 1668.6 ± 1442.3 pg/ml in proliferative diabetic retinopathy, 1528.6 ± 1994.6 pg/ml in non-proliferative diabetic retinopathy, 690.2 ± 402.1 pg/ml in non-diabetic retinopathy and 622.7 ± 245.3 pg/ml in non-diabetic patients. Significant differences were also found among these four groups (P < 0.0001). After correcting for total aqueous protein, the ratios of MIF and MCP-1 to total protein remained significantly correlated with the clinical stage of diabetic retinopathy (P < 0.0001, P = 0.0004, respectively). The ratios of MIF to total protein significantly correlated with the ratios of MCP-1 to total protein in diabetic patients (r = 0.680, P < 0.0001). Conclusions  Aqueous MIF levels significantly correlated with aqueous MCP-1 levels and the clinical stage of diabetic retinopathy. The results suggest that MIF has a co-operative role with MCP-1 in the progression of diabetic retinopathy.