Correlations of Serum Retinol-Binding Protein and Stromal Cell-Derived Factor-1 with Renal Function in Patients with Diabetic Kidney Disease.

Background: The aim is to investigate the correlations of serum retinol-binding protein (RBP) and stromal cell-derived factor-1 (SDF-1) with renal function in patients with diabetic kidney disease (DKD).

Methods: A total of 438 patients with type 2 diabetes mellitus (T2DM) treated from October 2017 to October 2020 were enrolled in this prospective study and divided into simple T2DM and DKD groups. According to urinary albumin-to-creatinine ratio (UACR), DKD patients were divided into moderate, severe, and nephrotic groups. They were assigned to one of the following categories of estimated glomerular filtration rate (eGFR): G1, G2, G3a, G3b, G4, and G5 stages. The correlations of RBP and SDF-1 with renal function were analyzed.

Results: The DKD group had a longer T2DM course and higher RBP, uric acid (UA), blood urea nitrogen (BUN), β2-microglobulin (β2-MG), serum creatinine (Scr) levels and UACR, and lower SDF-1 level and eGFR than those of simple T2DM group (p < 0.05). The areas under the receiver operating characteristic curves of RBP and SDF-1 for identifying DKD were 0.903 and 0.868, and the optimal cutoff values were 70.71 mg/L and 5.69 ng/mL, respectively. With increasing urinary albumin and clinical stage, RBP, UA, BUN, β2-MG and Scr levels and UACR significantly rose, while SDF-1 level and eGFR declined (p < 0.05). In patients with DKD, RBP was correlated positively with UACR, UA, BUN, β2-MG, and Scr (r = 0.764/0.787/0.693/0.577/0.801, p < 0.0001), and negatively with eGFR (r = -0.782, p < 0.0001). SDF-1 was correlated negatively with UACR, UA, BUN, β2-MG and Scr (r = -0.744/-0.794/-0.666/-0.605/-0.820, p < 0.0001), and positively with eGFR (r = 0.767, p < 0.0001). The multiple linear regression equation was RBP = 29.852 + 0.007 x UACR + 0.101 x UA + 0.497 x BUN + 0.034 x Scr-0.083 x eGFR (p < 0.001).

Conclusions: RBP and SDF-1 can identify DKD in patients with T2DM, and the degree of renal function damage is correlated positively with RBP and negatively with SDF-1. Elevated levels of UA, BUN, Scr and UACR as well as reduced eGFR are risk factors for evaluating RBP.