[Clinical evaluation of urinary alanine aminopeptidase in the patients with diabetes mellitus-comparison among AAP microalbumin and N-acetyl-beta-D-glucosaminidase].

To determine whether or not urinary Alanine aminopeptidase (AAP) could be used as an early marker for diabetic nephropathy, urinary AAP, microalbumin and N-acetyl-beta-D-glucosaminidase (NAG) were measured in 132 diabetic patients and 59 normal subjects. Urinary AAP, microalbumin and NAG in the diabetic patients and the normal subjects were 15.5 +/- 11.7 U/g. Cr and 9.1 +/- 6.9 (P less than 0.01), 27.4 +/- 35.5 mg/g. Cr and 8.4 +/- 4.4 (P = 0.0001), 10. 3 +/- 9.5 U/g. Cr and 3.9 +/- 2.1 (P = 0.0001), respectively. AAP had a moderate correlation with NAG (r = 0.58, P = 0.0001). AAP, microalbumin and NAG showed a slight positive correlation with age (AAP: r = 0.25, P less than 0.01, microalbumin: r = 0.32, P less than 0.01, NAG: r = 0.21, P less than 0.05), although it is significant, and AAP had a positive correlation with urinary protein concentration (r = 0.45, P = 0.0001) in diabetic patients. However, AAP in diabetic patients without proteinuria was higher than that in age-matched normal subjects. Urinary AAP was correlated with the indices of renal tubular damage like NAG, alpha 1-microglobulin and beta 2-microglobulin, so it seemed to be tubular origin but in the patients with clinical proteinuria, it might be partially glomerular origin. Since urine AAP increased in some patients without microalbuminuria and was not influenced by control of blood sugar, AAP could be used as an early marker of diabetic nephropath y in addition to microalbumin and NAG, but the effect of age should be considered in its estimation as in the case of NAG.