Abstract
The aim of this study was to clarify the clinical significance of urinary enzyme activity in patients with diabetes mellitus. Patients were divided into two groups: group A - 102 outpatients, group B-23 inpatients. Spot urine samples before breakfast from group A and aliquots of 24-hours urine collections at 4℃ from group B were used. Urinary enzyme activities (N-acetyl- β-D-glucosaminidase: NAG, alkaline phosphatase: ALP, Ieucine aminopeptidase: LAP, γ-glutamyl transpeptidase: γ-GTP) were determined by spectrophotometric assay, rate assay, Tuppy method and Orlowski method, respectively. 1) In group A, the percentage of the cases which showed higher than the normal range (NAG: 1.3-8.7, ALP: 4.2- 17.7, LAP: 0- 22.9 U/g. cer.) was 42.2% in NAG, 21.6% in ALP, and 8.8% in LAP. In a multiple regression analysis, the predictor variables which contributed to NAG were HbA1c, age, urinary protein and the one that contributed to ALP, LAP, y-GTP was urinary β2-microglobulin. 2) In group B, 87% of NAG was above the normal range (Mean ± 2 SD; 4.8 ± 3.9 U/day). There was no difference in the NAG activity between patients with and without nephropathy. The percent of high activities of ALP, LAP and y-GTP were 17%, 17%, 4%, respectively. Most of them were patients with nephropathy. There were correlations among ALP, LAP and γ-GTP, though no correlation existed between NAG and the other three enzymes. These results suggested: 1) NAG reflects lysosomal dysfunction of both glomerular and proximal tubular epithelial cells which may be caused by poor glycemic control 2) ALP, LAP, and γ-GTP reflect brush border damage of proximal tubules which may be caused by diabetic nephropathy.
