Effect of Thiazolidinedione Treatment on Proteinuria and Renal Hemodynamic in Type 2 Diabetic Patients with Overt Nephropathy

Proteinuria in diabetic nephropathy predicts the progressive loss of glomerular filtration rate (GFR) and serves as independent predictor for mortality. We performed the present study (ClinicalTrials. gov identifier: NCT 00324675) to clarify whether the activation of PPAR. receptor by thiazolidinediones was able to improve proteinuria and preserve renal function in advanced diabetic nephropathy. A total of 28 type 2 diabetic patients (4 women and 24 men, mean age 66.1 +/- 9.1 years) with urinary albumin excretion > 300 mg/24h and an estimated GFR < 60 ml/min were included into this prospective double blind trial to receive either rosiglitazone (RSG) 4 mg b.i.d or matching placebo (PLC) for 52 weeks in addition to their concomitant antidiabetic background therapy. At baseline and after 26 and 52 weeks, renal plasma flow (RPF) and GFR were determined before and after blockade of nitric oxide (NO) by intravenous administration of N-monomethyl-L-arginine acetate. RSG treatment resulted in a significant reduction of proteinuria (2.4 +/- 1.1; 1.2 +/- 0.6; 1.5 +/- 0.7 g/d at baseline, 26 weeks and 52 weeks; respectively, p < 0.05) whereas PLC did not influence proteinuria (1.6 +/- 0.6; 1.6 +/- 0.8; 1.7 +/- 0.8 g/d). GFR and RPF did not change significantly during the study, however, RSG improved the intrarenal NO bioavailability. RSG treatment was generally well tolerated and the major adverse event - development of edema - could be controlled by dose adjustment of the study drug and diuretic agents. In conclusion, we demonstrated a possible renoprotective effect of RSG in patients with advanced diabetic nephropathy.