Effect of control of blood glucose on urinary excretion of N-acetyl-beta-D-glucosaminidase in elderly type 2 diabetes mellitus.

diabetes mellitus. Once diabetic nephropathy is well established , attempts to modify the relentless progression of the disease have been essentially unsuccessful . Thus, indicators are needed to identify the early structural and functional changes of diabetic nephropathy which may be reversed by strict blood glucose control. A growing body of evidence reveals that a persistent elevation of urinary albumin excretion(microalbuminuria)in diabetic patients without clinical proteinuria predicts future development of overt diabetic nephropathy. N-acetyl-β-D-glucosaminidase(NAG)is a widely distributed lysosomal enzyme, located predominantly in the renal proximal tubules and is normally not filtered at the glomerulus . NAG has been shown to be increased in the urine of patients with various renal diseases including diabetic nephropathy. Some studies in diabetic patients have also shown that the elevation of urinary NAG is an early predictor of the development of diabetic nephropathy. In addition, ratios of urinary NAG to urinary creatinine(NAG index)for random specimens provides a useful , convenient measurement of daily NAG excretion and avoids many of the problems of 24-hour collections . However, some cross-sectional studies have demonstrated that urinary NAG activity may reflect metabolic control for patients with diabetes mellitus. The aim of the present study was to examine whether any correlation exists between the concentrations of urinary NAG and control of long-term blood glucose in elderly type 2 diabetes mellitus. The present study included 31 type 2 diabetic patients without retinopathy and 29 with retinopathy, aged from 60 to 88 years(mean age; 71.7±5.9, 70.3± 7.4 years , respectively). Twenty-three of these patients had a decrease in mean HbA1C of more than 2% and 37 patients had an increase of more than 2% during the 5 year follow-up period . Urinary NAG and HbA1C were measured from random samples collected on three or more separate occasions over six months. The mean NAG index and HbA1C were calculated every six months throughout the study. Urinary NAG activity was measured spectrophotometrically with sodio m-cresolsulfonphthleinyl Nacetyl-β-D-glucosaminide as substrate ( NAG test Shionogi). HbA1C was measured by the HPLC method . Statistical analysis was carried out using the paired t test. Data in the text and figures were expressed as mean±SD. Fig. 1 shows the change in mean NAG index in the patients who had a decrease in mean HbA1C of more than 2% during the follow-up period. The mean HbA1C decreased from 11.1±1.4 to 7.4±0.7% in patients without retinopathy and from 10.4±1.0 to 7.3±1.0% in those with retinopathy(both p<0.001). A signifi―Short Communications―