Background: Several clinical studies have shown increased level of urinary TGF-β1 in diabetic nephropathy patients and its correlation with urine albumin-to-creatinine ratio (UACR), but other studies showed different results. Because of this contradiction, this study aims to analyze the correlation between urinary TGF-β1 concentration and UACR, and also estimated glomerular filtration rate (eGFR) in type 2 diabetes mellitus (DM) patients by controlling some confounding factors.
Methods: This was a cross-sectional study, and the samples were obtained using consecutive sampling technique. The study was performed on 99 subjects (62 DM normoalbuminuria patients, 27 DM albuminuria patients, and 10 non-DM patients as controls) at Pasar Minggu Community Health Center. Urinary TGF-β1 concentration was measured by ELISA, and UACR was measured using immunoturbidimetry and an enzymatic colorimetric method. The eGFR value was calculated based on serum creatinine using Chronic Kidney Disease Epidemiology Collaboration equation. The results were then subjected to be analyzed statistically.
Results: There was an increase of urinary TGF-β1 in albuminuria (326.49±48.98) as compared to normoalbuminuria (290.54±30.71) and non-DM subjects (229.83±31.90), but the values did not differ statistically (P=0.790). In addition, no correlation was observed between urinary TGF-β1 and UACR (r=-0.084, P=0.410) and eGFR (r=0.155, P=0.125), but a correlation was found with SBP (r=-0.224, P=0.026). Linear regression analysis showed that urinary TGF-β1 and HbA1c could predict UACR, but only HbA1c could be considered as a significant predictor of UACR.
Conclusion: There is an increase of urinary TGF-β1 concentrations in albuminuria patients clinically, but not statistically. The concentration of TGF-β1 was not correlated with UACR and eGFR, but correlated with SBP. Since TGF-β1 could be interfered by many factors, including hypertension and its medication, urinary TGF-β1 might not be independently associated with renal function in diabetes.
Keywords: TGF-β1; UACR; albuminuria; diabetes mellitus; diabetic nephropathy.