Retinol Binding Protein, Transferrin and Osteopontin for the Diagnosis of Type 2 Diabetic Nephropathy

Background: Diabetic nephropathy (DN) is a microvascular complication derived from diabetes mellitus (DM). The aim of this study was to explore the diagnostic value of retinol binding protein (RBP), transferrin (TRF) and osteopontin (OPN) to early detect nephropathy in T2DM (type 2 diabetes mellitus) patients. Methods: 90 T2DM patients were enrolled in the study and divided in three groups: Patients with normal albuminuria (ACR <30 mg/g creatinine), patients with micro-albuminuria (ACR = 30 similar to 300 mg/g creatinine) and patients with macro-albuminuria (ACR >300 mg/g creatinine). Thirty healthy people of the same socioeconomic status and age as the diabetic patients enrolled as controls. Glycosylated hemoglobin a1c (HbA1c), insulin, plasma glucose, homeostasis model assessment of insulin resistance (HOMA-IR), blood lipids, cystatin C, creatinine, urea, TRF, RBP, glomerular filtration rate (GFR) and OPN were determined during the study. Results: Micro-albuminuria and macro-albuminuria DM groups showed higher levels of RBP, TRF and OPN compared to control and normal albuminuria DM groups (p < 0.05). The RBP, TRF and OPN of the micro-albuminuria group were 29.1 ng/mL, 97.8 ng/mL and 48.03 ng/mL, respectively, and the RBP, TRF and OPN of the macro-albuminuria group were 42 ng/mL, 142.3 ng/mL and 61.67 ng/mL, respectively. RBP, TRF and OPN were positively associated with the course of DM, diastolic and systolic blood pressure, HbA1c, glucose, triacylglycerol and ACR, HOMA-IR. However, they were negatively associated with GFR in the DM groups. Receiver operating characteristic (ROC) curve indicated that 94.5 ng/mL was the TRF optimal cutoff to differentiate DN and non-DN groups. TRF had a specificity of 75% and a sensitivity of 84%, AUC was 0.854. RBP cut-off was 26.5 ng/mL with a sensitivity of 86% and a specificity of 92%, AUC was 0.865. OPN cut-off was 37.3 ng/mL with a specificity of 81% and a sensitivity of 75%, AUC was 0.884. Creatinine cut-off was 37.5 mg/g with a sensitivity of 89% and a specificity of 72%, AUC was 0.840. RBP was more specific than OPN, TRF and ACR. Conclusions: Compared with OPN, TRF and ACR, RBP has higher specificity, so RBP marker can be a tool to track the development and progression of DN.