To the Editor.—
In a previous study we found a higher than normal glycosaminoglycan (GAG) excretion in patients with insulin-dependent diabetes (IDD), who have daily albumin excretion levels less than 25 mg (17 μg/min),1 a value that borders on the normal range for albuminuria. This abnormality was paralleled by a higher urinary activity of lysosomal glycohydrolases involved in GAG metabolism, as well as a normal excretion of brush border enzymes not related to GAG turnover. We therefore proposed a renal origin for GAG, perhaps due to a derangement in GAG turnover in the renal basement membrane.2 Since GAG is the major determinant of the anion layer of the glomerular basement membrane,3,4 this finding might mirror an early decrease in membrane selectivity, which could underlie the appearance of microalbuminuria.
Report of a Study.—
To test this hypothesis, we evaluated urinary GAG excretion during a 24-hour period in 25