[Urinary enzymes as a marker of the preclinical stage of diabetic nephropathy]

To identify early markers of the preclinical stage of diabetic nephropathy, a study was made of the activity of the specific canalicular enzymes in urine: N-acetyl-beta-D-glucosaminidase (NAG), beta-glucuronidase (beta-G1), gamma-glutamyl transferase (GGT), alkaline phosphatase (AP) and lactate dehydrogenase (LDH) in patients with diabetes mellitus without (26) and with (15) proteinuria. Patients without the clinical signs of diabetic nephropathy manifested a significant rise of excretion of lysosomal enzymes of the proximal canaliculi (NAG and beta-G1). Concomitant elevation of the excretion of several enzymes (NAG, beta-Gl, GGT and AP) was observed in 50% of cases. Patients with diabetic nephropathy demonstrated an increase of the excretion of all enzymes under study. Puncture biopsy of the kidneys was made in 4 patients without proteinuria with insignificant duration of diabetes mellitus and concomitant elevation of the excretion of a number of enzymes. Light microscopy revealed minimal changes in the glomeruli, whereas electron microscopy changes both in the glomeruli and in the canaliculi. The morphological changes in renal tissue confirm the diagnostic importance of high concomitant excretion of canalicular enzymes (NAG, beta-Gl, AP) as a marker of the preclinical stage of diabetic nephropathy.