Vitreous and plasma changes of endothelin-1, adrenomedullin and vascular endothelium growth factor in patients with proliferative diabetic retinopathy

To assess vitreous and plasma changes of vascular endothelial growth factor A (VEGF-A), adrenomedullin (ADM) and endothelin-1 (ET-1) in proliferative diabetic retinopathy (PDR).9 patients with PDR in type 2 diabetes (T2DM) and 11 age-matched non-diabetic patients were enrolled. The levels of VEGF-A, ADM and ET-1 were measured using an enzyme (ELISA) and a radioimmunoassay (RIA) both in vitreous and plasma samples.Vitreous ADM and VEGF-A levels were significantly higher in PDR patients (p=0.04 and p=0.02), whereas no differences were found in ET-1 levels (p=0.29). Plasma ADM levels were significantly higher in the PDR group (p0.01), whereas no significant differences were found in the plasma ET-1 and VEGF-A levels (p=0.30 and p=0.37). The ADM vitreous/plasma ratio was significantly reduced in PDR group.The role of ET-1 in advanced PDR is still controversial; it has been supposed a role limited to induce hypoxic state and promote angiogenesis in the early phases. Once the neo-angiogenic process starts, other mediators are mainly involved as VEGF and ADM. Our findings suggest that ADM is an important marker of advanced PDR as well as VEGF. Conversely, ET-1 is not significantly involved in the advanced stage of PDR.