[N-acetyl-beta-glucosaminidase (beta-NAG) in urine: a parameter for early detection of diabetogenic nephropathy in childhood].

N-Acetyl-beta-D-glucosaminidase (NAG) can be found in kidney in high activity. By determination of this enzyme activity in urine nephropathies can be recognized reliably. We have measured this lysosomal enzyme in the urine (Colorimetric method by Noto) of 206 children suffering from diabetes mellitus to find out whether diabetic nephropathy can be detected as soon as possible. Additional beta 2-microglobulin (ELISA) was measured in urine, which is reabsorbed nearly complete in the tubulus. The several proteins in urine were identified by SDS-PAGE. A high excretion of beta-NAG was found in children and adolescents with a poor metabolic control (elevated HbA1c). There was no correlation between NAG activity, duration of the diabetes and the age of the children. An elevated excretion of beta-2-microglobuline could be found only in seven children with a duration of the diabetes about six years; their HbA1c levels were high. The SDS-PAGE showed a pattern of glomerular protein excretion according to the duration of the diabetes. However there was no significant correlation to the metabolic control. Only in four children we ascertained mixed proteinuria. The increasing levels of urinary NAG may represent the increasing severity of nephrotic damage by diabetes. The estimation of NAG levels in urine would seem to be reliable in the early detection of diabetic angiopathy also and may serve as an index of diabetic control independent of blood sugar levels.