beta-N-acetylglucosaminidase and beta-glucuronidase activities in insulin-dependent diabetic subjects with retinopathy.

The serum activities of two lysosomal enzymes, beta-N-acetylglucosaminidase (EC 3.2.1.30, NAG) and beta-glucuronidase (EC 3.2.1.31, GLU), were determined in 41 insulin-dependent diabetics, 27 age-matched non-diabetic first-degree relatives of the diabetics and 103 age-matched non-diabetic blood-donors. The diabetics were divided into three groups on the basis of ophthalmoscopy: (1) no retinal abnormalities; (2) non-proliferative retinopathy; and (3) proliferative retinopathy. The activities of both serum enzymes were higher in diabetics (NAG 21.39 +/- 5.99; GLU 2.19 +/- 1.01) than in their relatives (NAG 17.22 +/- 3.99; GLU 1.62 +/-0.61). The diabetics with non-proliferative retinopathy had higher serum enzyme levels (NAG 24.05 +/- 6.26; GLU 2.60 +/- 1.06) than diabetics without retinopathy (NAG 17.88 +/- 3.00; GLU 1.69 +/ 0.64), whereas no statistically significant difference was found in patients with the proliferative form of retinopathy (NAG 18.67 +/- 6.28; GLU 1.99 +/- 1.04). In diabetics a positive correlation was found between serum beta-N-acetylglucosaminidase activity and blood glucose (p < 0.01), but not between beta-glucuronidase and blood glucose. Furthermore, the activities of both enzymes in diabetics correlated with the plasma triglyceride level (p < 0.05 for both correlations). No correlation was found between the enzyme levels and signs of other diabetic late complications.