Pioglitazone Reduces Urinary Protein and Urinary Transforming Growth Factor-βββββ Excretion in Patients with Type 2 Diabetes and Overt Nephropathy
Pisut Katavetin MD*, Somchai Eiam-Ong MD*, Sompongse Suwanwalaikorn MD**
Affiliation : * Division of Nephrology, Department of Medicine, Chulalongkorn University ** Division of Endocrinology, Department of Medicine, Chulalongkorn University
Objective : Increased urinary excretion of protein and transforming growth factor-β (TGF-β) are associated
with progression of diabetic nephropathy (DN). Thiazolidinediones (TZD) could reduce urinary protein
excretion in patients with microalbuminuric DN. There is little data of patients with macroalbuminuric DN.
Also, there are no available clinical data regarding the effect of TZD on TGF-β and type IV collagen in clinical
DN. The present study was carried out to evaluate the effect of pioglitazone (PGZ), a member of TZD, on
urinary protein, urinary TGF-β, and urinary type IV collagen excretion in type 2 diabetic patients with
macroalbuminuric DN.
Materials and Methods : Forty patients with type 2 diabetes and overt nephropathy, proteinuria more than 500
mg/day, were randomly assigned to receive PGZ (30 mg/day, n = 24) or placebo (control group, n = 16), for
12 weeks. Blood pressure, plasma glucose, glycated hemoglobin, lipid profile, 24-hour proteinuria, urinary
TGF-β, and urinary type IV collagen were determined and compared.
Results : Glycemic control and blood pressure in both groups were not significant different. At baseline, the
levels of proteinuria, urinary TGF-β, and type IV collagen were not significant different between both groups.
The geometric mean of urinary protein excretion in the PGZ group was progressively reduced from 1.64 to
0.98 gram/day (g/d), or 40.1% decrease which was significantly different (p < 0.05) from the 4.3% increase
(from 1.72 to 1.80 g/d) in the control group. Urinary TGF-β excretion in the PGZ group was decreased by
47.8% which significantly differed from the 59.7% increase in the control group (p < 0.05). Urinary type IV
collagen levels in the PGZ group were decreased by 35% which was slightly, but not significantly, different
from the 51.6% elevation in the control group (p = 0.06).
Conclusion : Besides the effectiveness in blood sugar control, pioglitazone could salutarily reduce proteinuria
and synthesis of TGF-β as well as type IV collagen. These beneficial effects of pioglitazone on diabetic
nephropathy are comparable to angiotensin converting enzyme inhibitors and angiotensin receptor blockers
Keywords : Pioglitazone, Diabetic nephropathy, Overt proteinuria, Urinary TGF-β
