Prospective study of the enzymatic activities in urine of n-acetyl-β-d-glucosaminidase, α-d-mannosidase, α- and β-d-glucosidases, α-l- and β-d-fucosidases, and β-d-galactosidase in type I diabetes mellitus with early nephropathy

Abstract Different surveys have been carried out on the plasma activities of different glycosidases in patients with insulin-dependent diabetes mellitus, but research on urinary glycosidases in this disease is scanty and incomplete. To elucidate the behavior of these lysosomal enzymes in the metabolic alterations ocurring in the glomerular basal membrane during the initial stages of diabetic nephropathy, we conducted a prospective study to examine the urinary activities of n -acetyl-β- d -glucosaminidase (NAG), α- d -mannosidase, α- and β- d -glucosidase, α- l - and β- d -fucosidase, and β- d -galactosidase in patients with type I insulin-dependent diabetes mellitus, surveyed over 18 months, whose early diabetic nephropathy was detected by the presence of microalbuminuria. The simultaneous determination of β 2 -microglobulin in urine confirmed the glomerular origin of the albuminuria. No statistically significant correlation was found between the levels of albuminuria and the activities of any of the glycosidases analyzed. In the diabetic patients, a significant decrease was observed in the activities of all the enzymes ( p d -mannosidase, although the decrease in the latter was very close to statistical significance ( p = 0.028, unilateral; p = 0.057 bilateral). Similarly, in the patients, there was a significant negative correlation ( p d -galactosidase, which showed a positive correlation ( p 1c . According to the results obtained, the urinary activities of the glycosidases cannot be said to be of value for marking the progressive glomerular alterations appearing in early nephropathy. We are unaware of the reason for most of the enzymes being decreased in urine. This could be due to a decrease in them in renal tissue. In any case, the urinary enzymatic activities are related to the recent blood glucose environment of the diabetic patient.