Urinary transforming growth factor-β1 and α1-microglobulin in children and adolescents with type 1 diabetes

Abstract

OBJECTIVE - Transforming growth factor (TGF)-β1 is an important mediator in the pathogenesis of diabetic nephropathy. Urinary TGF-β1 reflects TGF-β1 production in the kidney, and α1-microglobulin tubular dysfunction. These 2 markers were studied in the early phases of type 1 diabetes. RESEARCH DESIGN AND METHODS - There were 113 type 1 diabetic children and adolescents (mean ± SD: age 14.1 ± 2.9 years, and diabetes duration 7.4 ± 2.9 years, HbA(1c) 9.3 ± 1.5%) and 39 healthy subjects (age 13.8 ± 2.8 years) who participated in the study. Of the diabetic patients, 105 were normoalbuminuric (2-3 consecutive overnight urinary albumin excretion rates [AERs] <20 μg/min) and 8 had microalbuminuria (at least 2 AERs 20-200 μg/min). Overnight urinary TGF-β1 and α1-microglobulin levels were measured and the results expressed as the ratio to urinary creatinine concentration. RESULTS - Data are medians (range). Diabetic patients had higher urinary TGF-β1 levels than those of control subjects: 0.9 ng/mg (0.05-122.3) vs. 0.3 ng/mg (0.05-2.2) creatinine, respectively (P = 0.003). Urinary TGF-β1 levels correlated with urinary glucose (r = 0.2, P = 0.03) and α1-microglobulin (r = 0.2, P = 0.02) levels, but not with HbA(1c), AER, age, or duration of diabetes. In 43 patients with urinary TGF-β1 above the control levels, urinary TGF-β1 levels correlated with urinary glucose (r = 0.6, P < 0,001) and α1-microglobulin (r = 0.6, P < 0.001) levels. Diabetic patients had higher urinary α1-microglobulin levels than those of control subjects: 4.8 μg/mg (0.6-48.8) vs. 2.7 μg/mg (0.8-11.6) creatinine, respectively (P < 0.001). α1-Microglobulin levels correlated with AER (r = 0.2, P = 0.02), HbA(1c) (r = 0.3, P = 0.001), urinary glucose (r = 0.5, P < 0.001), and urinary TGF-β1 levels. CONCLUSIONS - An early rise in urinary TGF-β1 levels was observed in young type 1 diabetic patients. Urinary TGF- β1 is associated with 2 interrelated tubular markers, α1-microglobulin and urinary glucose.