Urinary excretion of glycated albumin in insulin-dependent diabetic patients with micro- and macroalbuminuria.

Non-enzymatic glycosylation (glycation) involves both circulating proteins, such as albumin and structural proteins, such as the components of the glomerular basement membrane. Glycated albumin is more anionic than unmodified plasma albumin at physiologic pH. Preferential urinary excretion of glycated proteins has occasionally been reported in diabetes. We therefore investigated the selectivity index (renal clearance of non-glycated/glycated albumin) in 25 insulin-dependent diabetic patients (17 with microalbuminuria and 8 with macroalbuminuria), and 19 healthy subjects. The selectivity index was significantly higher (p less than 0.01) in the microalbuminuric patients than in the macroalbuminuric patients and the control subjects: 1.11 +/- 0.03 SEM vs 0.94 +/- 0.08 vs 0.98 +/- 0.02. These results are not consistent with preferential urinary excretion of glycated albumin in insulin-dependent diabetic patients with increased urinary albumin excretion.

The increase in albuminuria induced by exercise is not associated with preferential excretion of glycated albumin in type 1 (insulin-dependent) diabetic patients.

The increase in urinary albumin excretion induced by acute exercise in Type 1 (insulin-dependent) diabetic patients is associated with the urinary excretion of cationic proteins. To test whether the renal excretion of glycated albumin (more anionic than non-glycated albumin) is affected by exercise, we submitted seven normoalbuminuric (albumin excretion rate less than 30 mg/24 h) Type 1 diabetic patients and six well-matched healthy subjects to an exercise test (600 kpm/min for 20 min) on a bicycle ergometer, preceded and followed by a 1-h resting period. The selectivity index (renal clearance of non-glycated/glycated albumin) was not significantly different among the pre-exercise, exercise and post-exercise periods, either in the normal subjects (1.01 +/- 0.03 vs 1.08 +/- 0.06 vs 1.08 +/- 0.05) or in the diabetic patients (1.25 +/- 0.09 vs 1.20 +/- 0.07 vs 1.20 +/- 0.06), whereas it was significantly higher (p less than 0.05) in diabetic patients compared to healthy subjects during pre-exercise. These results are not consistent with the hypothesis that acute exercise may induce a preferential excretion of glycated albumin.

Urinary excretion of glycated albumin in insulin-dependent diabetic patients with normal urinary albumin excretion.

Glycation involves both circulating proteins, such as albumin, and structural proteins, such as the components of the glomerular basement membrane. A preferential excretion of glycated albumin (more anionic at physiological pH compared with unmodified plasma albumin) has been reported by some authors, but not by others. We therefore investigated the selectivity index (renal clearance of non-glycated albumin/clearance of glycated albumin) in 25 insulin-dependent diabetic patients with normal urinary albumin excretion and in 19 well-matched control subjects. The selectivity index was significantly higher in diabetic patients than in control subjects: 1.38 +/- 0.05 SEM vs 0.98 +/- 0.02, p less than 0.0001. This result is not consistent with a preferential urinary excretion of glycated albumin, at least in normoalbuminuric uncomplicated insulin-dependent diabetic patients.