A preliminary multivariate analysis in patients with diabetes mellitus (n=109) between urinary excretion of N-acetyl-β-D-glucosaminidase (u-NAG) and nine parameters including age, duration, HbA₁c, concentrations of plasma glucose, BUN, creatinine, β₂-microglobulin in a fasting state, degree of proteinuria and degree of retinopathy was performed, and changes of u-NAG levels showed a close correlation with the changes of HbA₁c, as well as with age and the degree of proteinuria.
From this data, further study on patients with diabetes mellitus (n=84) was undertaken to investigate changes of u-NAG levels in relation to changes of HbAic during the course of treatment. Levels of u-NAG in 10 patients with uncontrolled hyperglycemia were 14.9±7.0 U/g. creat (mean±SD), and decreased in all to 8.0±3.9 U/g. creat two months after hyperglycemia was corrected by the administration of insulin or an oral hypoglycemic agent. U-NAG levels significantly increased from 7.1 ± 2.6 U/g. creat to 12.1 ±4.9 U/g. creat in another group of 10 diabetic patients whose glycemic control worsened in two months, as seen by the increase in HbA₁c from 7.3 ± 0.8% to 9.1 ±0.9%. On the contrary, in 64 patients whose HbA1c did not show a remarkable change, u-NAG levels also had no changes.
To examine when u-NAG levels start to the affected by the change of plasma glucose levels, u-NAG was serially measured, in 15 patients who were admitted to our hospital. In 10 of them, hyperglycemia improved within a week, and their levels of u-NAG decreased significantly at four weeks after euglycemia was achieved. In the remaining five patients whose hyperglycemia did not improve within a week, u-NAG levels did not show a significant decrease.
Transient hyperglycemia induced by the 75 g oral glucose load test brought about no increases in u-NAG levels.
These results suggest that urinary excretion of NAG is closely related to the glycemic control in patients with diabetes mellitus.