Urinary N-acetyl-beta-D-glucosaminidase activity in type I diabetes mellitus.

We measured urinary albumin excretion rate (AER) and N-acetyl-beta-D-glucosaminidase (NAG) activity in relation to disease duration, acetylated hemoglobin (HbA1c), hypertension and puberty in 44 children and adolescents with type 1 diabetes mellitus. AER and Urinary NAG activity were significantly higher in the patients compared to controls (AER 19.4 +/-; 35.8 vs 4.7 +/- 4.4, NAG activity 5.6 +/- 0.6U vs. 1.6 +/- 0.2U). Microalbuminuria was present in seven patients (15.9%), all of whom were pubertal. There was no correlation between AER and urinary NAG activity. There was a significant direct correlation between AER and disease duration (P <0.05), HbA1c (P < 0.05), diastolic blood pressure (P <0.05) and puberty (P <0.05). None of the microalbuminuria related variables was significantly correlated with urinary NAG activity. Puberty was an independent factor for elevated urinary NAG activity. This study shows that urinary NAG is elevated in children and adolescents with type 1 diabetes mellitus, but is not associated with AER related factors except for puberty. Urinary NAG activity does not appear to be a useful marker for early detection of diabetic nephropathy in children and adolescents with type 1 diabetes mellitus.