Studies of plasma beta-N-acetylglucosaminidase activity in experimental and clinical diabetes mellitus.

Plasma beta-N-acetylglucosaminidase (NAG) activity was measured in streptozotocin diabetic rats, in non-diabetic rats during starvation and refeeding, and in diabetic patients and normal subjects. The enzyme activity increased significantly in the diabetic rats and in the starved non-diabetic rats. The activity decreased markedly after insulin injection in diabetic rats and after refeeding in non-diabetic rats. The plasma NAG activity (532 +/- 24 nmole/hr/ml, M +/- SE) in 21 diabetics with FBS value less than 100 mg/dl was higher than the enzyme activity (455 +/- 15) in 42 normal subjects (p < 0.01), supporting the idea that a more intensive treatment is necessary to normalize the metabolic derangement of diabetes. There was no significant difference between diabetics with and without microangiopathy. While the influence of age and abnormal liver function was noted, there was no correlation between the NAG activity and the platelet adhesiveness or between the NAG activity and the plasma triglyceride. The results suggest that the plasma NAG activity increases in diabetes mellitus, either with microangiopathy or not. The reason for the failure to demonstrate a significant correlation between the total plasma NAG activity and microangiopathy is discussed. The analysis of the subfractionation of the plasma NAG may be necessary to disclose a significant correlation with microangiopathy.