Effect of losartan and amlodipine on proteinuria and transforming growth factor-β1 in patients with IgA nephropathy

Background. Transforming growth factor-β1 (TGF-β1) is the major profibrotic cytokine involved in many renal diseases, and urinary TGF-β1 reflects intrarenal TGF-β1 production. Urinary TGF-β1 excretion is reported to be significantly increased in patients with immunoglobulin A (IgA) nephropathy. The aim of the present study was to compare the effects of losartan and amlodipine on proteinuria, as well as on serum and urine TGF-β1 levels in IgA nephropathy patients with hypertension and proteinuria. Methods. The initial 4 week washout period was followed by 12 weeks of active treatment, in which patients were randomized to once-daily treatment with losartan 50 mg (group 1, n = 20) or amlodipine 5 mg (group 2, n = 16). Urinary protein and TGF-β1 excretion, serum TGF-β1 and other clinical parameters were determined at baseline and during 12 weeks of active treatment. Results. Both treatments controlled blood pressure (BP) to a similar degree, and renal function and other biochemical parameters did not change during the study period. Urinary protein and TGF-β1 excretions were significantly elevated in IgA nephropathy patients. Losartan significantly reduced urinary protein (from 2.3 ± 1.5 g/day at baseline to 1.2 ± 1.5 g/day at 12 weeks, P < 0.05) and urinary TGF-β1 excretion (from 31.2 ± 14.0 pg/mg creatinine at baseline to 22.1 ± 13.5 pg/mg creatinine at 12 weeks, P < 0.05). In contrast, amlodipine had no affect on urinary protein and TGF-β1 excretion. Both losartan and amlodipine failed to reduce serum TGF-β1 levels. Conclusion. Losartan and amlodipine, with similar control of BP, showed different effects on urine protein or TGF-β1 excretion. Whereas losartan improved both urinary parameters, amlodipine did not. These differences might be important for the management of IgA nephropathy.