Response of urinary N-acetyl-beta-D-glucosaminidase to rapid decreases in blood glucose.

Urinary N-acetyl-beta-D-glucosaminidase (NAG) has been shown to be a sensitive indicator of blood sugar control. Twelve insulin-dependent diabetics whose blood glucoses were being controlled with the artificial pancreas had concurrent urinary NAG activity measured. Blood glucose dropped markedly from 198 +/- 22 mg/dl (x +/- SEM) to 121 +/- 7 mg/dl during the 25 h on the artificial pancreas. For the entire group UNAG: UCr dropped from 14.9 +/- 4.4 to 7.25 +/- 1.68 units. In order to determine if larger decreases in blood glucoses over the course of the study resulted in larger decreases in UNAG: UCr, an arbitrary division at 180 mg/dl was made. Six patients with blood glucoses at or above this level at the start of the study showed a drop in both blood glucoses and UNAG: UCr (261 +/- 24 to 134 +/- 12 mg/dl and 21.1 +/- 6.1 to 7.29 +/- 1.53 U, respectively). Even though the other six patients had blood glucoses below the renal threshold, both blood glucoses and UNAG: UCr declined (136 +/- 4 to 110 +/- 4 mg/dl; 8.89 +/- 2.4 to 6.2 +/- 1.64 U, respectively). Thus not only may urinary NAG activity reflect long-term control and renal complications of diabetes, but this enzyme is also responsive to acute changes in blood glucose.