Elevation of urinary βig-h3, transforming growth factor-β-induced protein in patients with type 2 diabetes and nephropathy

Transforming growth factor-β (TGF-β) is a pro-sclerotic growth factor implicated in the pathogenesis of diabetic nephropathy. βig-h3 is an extracellular matrix protein which is induced in many cells by TGF-β. This study examined urinary βig-h3 excretion in diabetic patients with elevated urinary albumin excretion and the clinical application of urinary βig-h3 as a marker of diabetic nephropathy. Urinary and serum βig-h3 levels were determined by enzyme-linked immunosorbent assay in 163 type 2 diabetic patients and 101 healthy control subjects of comparable age and weight. The ratio of urinary βig-h3 and TGF-β to creatinine was analyzed in patients with different degree of nephropathy. The βig-h3 to creatinine ratio in urine was elevated in all groups of type 2 diabetics with normoalbuminuria (101.6±9.27), microalbuminuria (120.2±14.48), and overt proteinuria (146.3±16.34), when compared with control subjects (64.8±7.14) (P<0.01). There was a positive correlation between urinary βig-h3 and TGF-β excretion rate and a positive correlation between urinary βig-h3 and albumin excretion rate (AER). These data show that urinary levels of βig-h3 are elevated in type 2 diabetic patients with nephropathy and may be used as a marker of diabetic nephropathy.