Effect of troglitazone on urinary albumin excretion and serum type IV collagen concentrations in Type 2 diabetic patients with microalbuminuria or macroalbuminuria

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Abstract
Aims Troglitazone, a newly developed thiazolidinedione derivative, has been shown to ameliorate microalbuminuria in diabetic animal model and in human diabetic nephropathy in short‐term studies. The aim of the present study was to determine whether troglitazone or sulphonylurea affect micro‐ albuminuria, macroalbuminuria, or serum type IV collagen concentrations in patients with diabetic nephropathy. Methods We studied 32 normotensive patients with type 2 diabetes mellitus associated with microalbuminuria (n = 16) or macroalbuminuria (n = 16) and 20 healthy controls. The patients were randomly assigned to one of two groups: those treated with glibenclamide (5.0 mg/day) (n = 8) and those treated with troglitazone (400 mg/day) (n = 8). They received the drug regimen for 12 months. Serum type IV collagen was measured with sandwich enzyme immunoassay. Results Type IV collagen concentrations in macroalbuminuric patients were higher than those in microalbuminuric patients (P < 0.05) and healthy controls (P < 0.01). Troglitazone reduced urinary albumin excretion (UAE) in micro‐ albuminuric patients from 126 μg/min (range 58–180 μg/min) to 42 μg/min (range 14–80 μg/min) (P < 0.01) and also reduced serum type IV collagen levels gradually at 3, 6 and 12 months after treatment (P < 0.05). However, glibenclamide did not affect UAE and type IV collagen levels in micro‐ albuminuric diabetes patients. In addition, neither troglitazone nor gliben‐ clamide changed UAE and type IV collagen levels in macroalbuminuric patients. Conclusions These data suggest that troglitazone is an effective treatment for renal injury in patients with early diabetic nephropathy.