Urinary transforming growth factor-β₁, collagen IV and the effect of insulin in children at diagnosis of diabetes mellitus

Abstract

Objective. This study investigated whether metabolic derangement at diagnosis of diabetes mellitus affects the function of the basement membrane and the excretion of several components and whether insulin treatment can normalize this. It was designed to evaluate urinary excretion rates of transforming growth factor-β₁ (TGF-β₁), the carboxy-terminal domain of collagen IV (NC1) and albumin in children during the first 20 days of treatment after diagnosis of type 1 diabetes. Material and methods. Thirty-four newly diagnosed diabetic children between 4 and 16 years of age and 26 healthy children of matching age were studied with timed overnight urine collections. Urine was collected during the first 20 days of treatment. Results. Urinary excretion of albumin and TGF-β₁ in diabetic children were significantly increased at entry but normalized during 20 days of treatment with insulin compared with control children. In contrast, the non-significant high NC1 excretion at diagnosis did not change but became significantly increased after 20 days of insulin treatment. Overall, the kidney size was within normal limits and unaffected by treatment. The largest kidneys had less NC1 excretion (R= − 0.67, p<0.05, n=13) and a lower glomerular filtration rate (R= − 0.77, p<0.01, n=10) than the smallest kidneys. After 20 days of treatment TGF-β₁ excretion had decreased in children with kidney size > 8.5 cm. Conclusion. Correction of the metabolic derangement with insulin decreased excretion of albumin and TGF-β₁, but had no effect on kidney size and urine NC1 excretion, presumably because the observation period was too short.

• Albuminuria
• children
• collagen IV
• type 1 diabetes
• transforming growth factor-β