Serum activity of beta-N-acetylglucosaminidase in obese hyperinsulinemic subjects.

We have measured serum activity of beta-N-acetylglucosaminidase (NAG, fluorimetric method) in some groups of obese subjects with similar degrees of overweight but with different insulin secretion and glucose tolerance (GT) during OGTT. In the control group (35 normal subjects, mean body weight 102% of ideal body weight, normal GT) NAG was 282 +/- 77 nmol S/h/ml; in group I (11 subjects, body weight 149%, normal GT and insulin levels) NAG was 304 +/- 55; in group II (19 subjects, body weight 142%, normal GT and high insulin levels) NAG was 453 +/- 90 (p less than 0.001 vs group I and controls); in group III (14 subjects, body weight 154%, impaired GT and high insulin levels) NAG was 481 +/- 108 (p less than 0.005 vs group I and controls); in group IV (16 subjects, body weight 153%, diabetic GT and high insulin levels) NAG was 657 +/- 109 (p less than 0.001 vs other groups). Moreover in the whole series NAG levels and insulin areas, but not NAG levels and degree of overweight, were significantly correlated (r=0.46, p less than 0.001). These data show that hyperinsulinism (especially when there is also pathological glucose tolerance) can positively affect NAG levels, probably through altered glycoprotein turnover, of which NAG serum levels are a sensitive indicator.