ObjectiveTo investigate the role of apelin, glycosylated hemoglobin (HbA1c), cholesterol (TC), triglyceride (TG), High density lipoprotein cholesterol (HDLC), low density lipoprotein cholesterol (LDLC) in the development and progress of diabetic retinopathy (DR). MethodsThe serum concentration of apelin, HbA1c, TC, TG, HDLC and LDLC were measured in 30 normal control subjects and 90 patients with type 2 diabetic mellitus, including 30 cases without DR (NDR), 30 with non-proliferative DR (NPDR), 30 with proliferative DR (PDR). These data were analyzed by SPSS for windows 13.0. ResultsThe serum concentration of apelin, HbA1c, TC, HDLC, LDLC were significantly higher in NDR, NPDR, PDR group than those in control group (F=403.06, 5.45, 4.27, 201.56, 4.90;P < 0.05). The serum concentration of TG has no significantly difference (F=2.19, P > 0.05). The serum concentration of apelin, HbA1c, TC, LDLC were significantly higher in NDR, NPDR, PDR group than those in control group (t=0.30, 0.58, 0.79;P < 0.05), the serum concentration of HDLC were significantly lower than those in control group(t=0.79, P < 0.01). There were significantly positive correlation between the progression of DR and the serum concentration of apelin, HbA1c, TC, LDLC(r=0.962, 0.562, 0.935;P < 0.05). There were significantly negative correlation between the progression of DR and the serum concentration of HDLC(r=-0.753, P < 0.01). There were correlation between apelin and HbA1c, LDLC and HDLC(r=0.956, 0.741, -0.691;P < 0.01). ConclusionOur data demonstrated that serum apelin levels increased significantly in patients with diabetic retinopathy, and are closely related to blood sugar, blood lipid metabolic abnormalities.