To evaluate the clinical significance of nephrin and podocin urinary excretion for early diagnosis of diabetic nephropathy in patients with type 1 and type 2 diabetes.
Material and methods
We studied 74 diabetic patients (type 1 in 30 patients and type 2 in 44 patients). They were distributed into three groups: 41 patients with albuminuria <30 mg/g Cr (AU1), 13 patients with albuminuria 30-300 mg/g Cr (AU2) and 20 patients with proteinuria. Estimated glomerular filtration rate (GFR) was reduced to 60-90 and <60 ml/min/1.73 m2 in 25 and 8 patients, respectively. Arterial hypertension was found in 52 patients (70%), mainly with type 2 diabetes. Ten healthy subjects were studied as a control group. Urinary levels of nephrin and podocin were measured by ELISA.
High nephrinuria (>5.84 ng/ml/g) was found in 63%, 77% and 80% of patients with AU1, AU2, and proteinuria, respectively. The median urinary nephrin levels in patients with AU1 and AU2 did not differ in type 1 and type 2 diabetes. In patients with proteinuria, the median urinary nephrin level was significantly higher compared with that in patients with AU1 and AU2 (p<0.05). Podocinuria was increased (>1,73 ng/ml/g) in 78%, 54% and 83% patients with AU1, AU2, and proteinuria, respectively. There was a direct correlation between nephrinuria and albuminuria, particularly in patients with AU2 (r=0.947, p<0.05). In type 1 diabetes, nephrinuria and podocinuria correlated directly with serum creatinine (r=0.489, p<0,05, and r=0.468, p<0.05) and indirectly with GFR (r=-0.461, p<0.05). In patients with GFR<60 ml/min/1.73 m2, there was a direct relationship between nephrinuria and diabetes duration, that was independent on diabetes type. In patients with diabetes of a shorter duration (<5 years), nephrinuria correlated directly with НbА1с level (r=0.84, р<0,01), and in type 2 diabetes it correlated with systolic blood pressure (r=0.73, р<0.05).
Nephrinuria and podocinuria can be useful markers for early diagnosis and monitoring of DN.
Diabetes mellitus, diabetic nephropathy, albuminuria, proteinuria, podocytes damage, nephrinuria, podocinuria.