Plasma apelin and asymmetric dimethylarginine levels in type 2 diabetic patients with diabetic retinopathy

Oxidative stress is thought to be one of the underlying mechanisms of diabetic microvascular complications such as diabetic nephropathy and diabetic retinopathy (DRP). Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) synthase inhibitor and increased by oxidative stress. Apelin is an endogenous ligand for human orphan G-protein-coupled receptor, APJ and increases NO generation. In this study, our aim was to evaluate ADMA and apelin levels in diabetic patients with or without retinopathy and their relationships between retinopathy stages and metabolic parameters. Seventy-nine diabetic patients were included into the study and classified into three groups. Group 1 consisted of 41 patients with no DRP (NDRP), group 2 consisted of 23 patients with nonproliferative DRP (NPDRP), and group 3 consisted of 15 patients with proliferative DRP (PDRP). Plasma ADMA and apelin levels were found to be similar in all groups. But, there was a positive correlation between apelin levels and urinary albumin/creatinine ratio.Further studies involving larger patients populations and healthy controls should be done to clarify the pathogenetic significance of ADMA and apelin in diabetic microvascular complications.