[Urinary enzymes in insulin-dependent diabetes mellitus]

In patients suffering from insulin-dependent diabetes mellitus (IDDM) with or without preclinical and clinical signs of diabetic nephropathy, the degree of epithelial cell lesions in the renal tubules was assessed from the urinary activities of enzymes at various sites, such as lysosomal (N-acetyl-beta-D-glucosaminidase (NAG) and beta-galactosidase (beta-GA)), brush edge membranous (alanine aminopeptidase (AAP), and cytosolic (alpha-glucosidase (alpha-GL)). Patients from Groups 1 and 2 had no preclinical and clinical signs of nephropathy. In Group 1 patients, the magnitude of enzymuria was not different from that in normalcy. However, Group 2 patients exhibited significant increases in urinary NAG and beta-GA activities as compared to Group 1 patients and healthy individuals. In Group 3 patients with microproteinuria from 0.05 to 0.5 mg protein per ml urine, displayed a further enhancement of NAG and beta-GA activities as compared to Group 2 patients and significantly higher activity than did Groups 1 and 2 patients and healthy individuals. In Group 4 patients with macroproteinuria of > 0.5 mg/ml), greater increases in the activities of NAG, beta-GA, and AAP were not found, however, there was a significant increase in alpha-G1 activity. The findings suggest the varying degrees of epithelial cell damage in the renal tubules in patients of different groups and the possibility of early detection of lesion in the proximal portion of nephronic tubules in IDDM patients as assessed from urinary enzyme levels.