Urine and serum leucine aminopeptidase, N-acetyl-β-glucosaminidase and γ-glutamyl transpeptidase activities in diabetics with and without nephropathy

Urinary and serum activities of leucine aminopeptidase (LAP), N-acetyl-β-glucosaminidase (ABG) and γ-glutamyl transpeptidase (GGTP) were determined in four groups: 1) control subjects with normal oral glucose tolerance test and normal renal function; 2) latent diabetics with elevated oral glucose tolerance test and diabetic parents; 3) overt diabetics; 4) diabetics with slight nephropathy, exemplified by elevated serum creatinine levels and decreased creatinine clearance. No clear differences were found in the urinary GGTP and serum enzyme activities. Urinary LAP activity was significantly increased in Groups 2, 3 and 4, and urinary ABG activity in Groups 3 and 4. However, since the rise in urinary LAP activity was less consistent than that in ABG, it seems that the appearance of the latter enzyme in urine most likely results from tubular damage and may serve as a sensitive indicator of early diabetic kidney disease.