Beta2-microglobulin and cystatin C in type 2 diabetes: assessment of diabetic nephropathy.
BACKGROUND
Changes in glomerular filtration rate (GFR) provide a valuable indicator of the progression of diabetic nephropathy (DN). This study was designed to demonstrate the clinical values of serum cystatin C (Cys C) and beta2-microglobulin in the assessment of renal function in type 2 diabetics by comparing them with the GFR, estimated from the uptake phase of 99 m technetium dimetiltriamino pentaacetic acid renogram (GFR-DTPA) and creatinine clearances.


METHODS
68 type 2 diabetic patients with (urinary albumin excretions (UAE) 30 - 300 mg/24 h) (n = 39) and without (UAE < 30 mg/24 h) (n = 29) microalbuminuria and 32 controls were enrolled in the study. Serum Cys C, beta2-microglobulin, creatinine, urinary microalbumin levels, creatinine clearances and GFR-DTPA values were determined in all groups. Non-parametric ROC curves, using a cut-off GFR-DTPA of 60 mL/min/1.73 m (2), were obtained for these markers.


RESULTS
Serum Cys C, beta2-microglobulin, glucose and HbA1c concentrations were significantly higher in the group with diabetes compared to controls. In the patients with microalbuminuria, serum Cys C and glucose concentrations increased significantly in comparison to patients with normoalbuminuria, while no differences were observed for beta2-microglobulin levels. Serum creatinine concentrations, GFR-DTPA values and creatinine clearances were not different between both diabetic groups and controls. Cys C was positively correlated with beta2-microglobulin and creatinine and negatively with GFR values; beta2-microglobulin was also positively correlated with serum creatinine in microalbuminurics. A significant inverse correlation was found between beta2-microglobulin and GFR values in both microalbuminurics and normoalbuminurics.


CONCLUSIONS
Increased Cys C and beta2-microglobulin in diabetics may be early indicators of incipient DN. The diagnostic accuracies of Cys C and beta2-microglobulin are superior to that of serum creatinine in distinguishing between mild and moderately reduced GFR.
Aksun
S Apakkan
SA
Department of Clinical Biochemistry, Ege University Faculty of Medicine, Bornova, Izmir, Turkey.
Ozmen
D
D
Ozmen
B
B
Parildar
Z
Z
Mutaf
I
I
Turgan
N
N
Habif
S
S
Kumanlioğluc
K
K
Bayindir
O
O
D000328:Adult; D000368:Aged; D000419:Albuminuria / Q000097:blood / Q000175:diagnosis; D015415:Biomarkers; D003404:Creatinine / Q000097:blood; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000000981:diagnostic imaging; D003928:Diabetic Nephropathies / Q000097:blood* / Q000000981:diagnostic imaging; D042241:Early Diagnosis; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate; D001613:beta 2-Microglobulin / Q000097:blood*
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D019275:Radiopharmaceuticals; D001613:beta 2-Microglobulin; D003404:Creatinine; D016284:Technetium Tc 99m Pentetate