Urinary glycosaminoglycans, sialic acid and lysosomal enzymes increase in nonalbuminuric diabetic patients.

Urinary excretion of glycosaminoglycans (GAGS) and sialic acid (SA), as well as the activity of two renal enzymes related to glycoprotein metabolism, N-acetyl-beta-D-glucosaminidase (NAG) and beta-galactosidase (GAL), and two others unrelated to glycosaminoglycans and glycoprotein metabolism, gamma-glutamyltranspeptidase (gamma-Gt) and angiotensin-I-converting enzyme (ACE), were evaluated in 40 insulin-dependent diabetic patients with normal range albuminuria, 21 patients with mesangial glomerulonephritis, and 30 control subjects. Diabetic and glomerulonephritic patients excreted a significantly higher amount of GAGS and SA, and showed greater NAG and GAL activities; gamma-Gt and ACE levels were within normal ranges. No correlation could be demonstrated between diabetes duration and GAGS, SA, NAG and GAL findings. Moreover, no correspondence between degree of metabolic control, as reflected by glycosylated hemoglobin (HbA1a-c) and GAGS, SA, NAG and GAL emerged.