[Clinical evaluation of N-acetyl-beta-D-glucosaminidase on prediction of diabetic nephropathy].

To assess whether urinary N-acetyl-beta-D-glucosaminidase (NAG) could be used as a predictor of diabetic nephropathy, renal tubular enzymes such as NAG and gamma-glutamyl transpeptidase (gamma GTP), albumin, total protein and beta 2-microglobulin (BMG) in urine and/or serum were measured in various stages of diabetic nephropathy. As a predictor of diabetic nephropathy, urinary NAG was the most useful indicator among of them. Urinary gamma GTP had no clinical benefit on early detection of diabetic nephropathy although in cis-platin induced nephrotoxicity both urinary gamma GTP and NAG increased in parallel. Increase of urinary NAG appeared in diabetic patients prior to clinical proteinuria. With appearance of proteinuria, urinary NAG more increased. Urinary NAG correlated significantly with HbAlc and BMG in serum (sBMG). It is therefore needed for clinical application of urinary NAG as a predictor of diabetic nephropathy that control states of blood glucose in the patients should be considered. However, the results of sequential measurements of urinary NAG, sBMG and HbAlc in 78 diabetic patients for 18-month period showed that only urinary NAG was a responsible factor for elevation of sBMG known as an indicator of deterioration of renal function. These results indicate that renal tubular damage may already exist in early-stage of diabetic nephropathy, and that increase of urinary NAG activity is a useful predictor of diabetic nephropathy.