Objective: Low molecular weight proteins serum Cystatin C (sSC), β-2 Microglobulin (sβMg), Retinol Binding Protein (sRBP) have been proposed for estimation of Glomerular Filtration Rate (GFR). This study is designed to see how these proteins change with alterations of GFR in type2 diabetic patients.

Methods: 116 type 2 diabetic patients, 62 females (%53) and 54 males (%47), with a mean age of 57.7±10.6 years, age and gender matched 31 healthy controls, 17 females (%55) and 14 males (%45), mean age 55.8±8.6 years were included in the study. sSC, sβMg, sRBP, serum creatinine (sCre) and urine creatinine levels were determined.

Results: sSC, sβMg, sRBP and sCre levels were found as 0.84±0.16 mg/L, 1.74±0.28 mg/L 0.038±0.012 g/L, 0.77±0.12mg/dL respectively. Diabetic groups' values for these proteins were 1.15±0.42 mg/L for sSC (p<0.001), 2.07±0.98 mg/L for sβMg (p=0.003), 0.044±0.013 g/L for sRBP (p=0.015) and 0.89±0.34 mg/dL for sCre (p=0.003) and were significantly higher. Creatinine clearances (CCr) of controls (106.5±27.1, mean±SD, mL/min/1.73 m2) and diabetics (94.9±37.3, mean±SD, mL/min/1.73 m2) did not show statistically significant difference (p=0.11). When diabetic group was subdivided according to their CCr's (1. group CCr>80, n=71; 2. group 79>CCr>50, n=31; and 3. group CCr<49 mL/ min/1.73 m2, n=14) we found significant differences in mean concentrations of sSC (p=0.002), sβMg (p<0.001), and sCre (p<0.001), but not in sRBP (p=0.643). Only sSC differed significantly between Groups 1 and 2 (post-hoc p=0.036).

Conclusion: sSC, sβMg ve sRBP were markedly increased in diabetics. Serum levels of sSC and sβMg increased gradually, as GFRs declined. Only sSC levels showed significant difference between diabetics with normal and slightly reduced clearances.