Introduction. Tubulointerstitial injury is both a key feature of diabetic nephropathy and an important predictor of renal dysfunction. N-Acetyl B glucosaminidase (NAG) is derived from proximal tubular cells and is widely used to evaluate tubular renal function. Objective. The objective of this study is whether NAG can be used as an early marker of diabetic nephropathy by comparing the urinary NAG levels between healthy controls and diabetic patients and determining changes in urinary NAG excretion after treatment with low-dose combination perindopril (2 mg)/ indapamide (0.625 mg)/o.d. Materials and Methods. A total of 50 patients (29 female) with type II diabetes mellitus applying to our diabetes outpatient clinics for the first time were included in our study (Group 1). Diabetic patients were classified into three subgroups on the basis of their duration of diabetes: Group 1(A) (n = 15) <= 3 years, Group 1(B) (n = 19) 3 to 5 years, and Group 1(C) (n = 16) >5 years. The inclusion criteria were no prior use of antiltypertensive agents; blood pressure <130/85 mmHg; urinary albumin excretion <30 mg/day; and absence of renal failure, diabetietes, and hypertensive retinopathy. A total of 30 healthy individuals (16 female) (Group 2) were assessed as the control group. Systolic and diastolic blood pressures, HbA1c, body mass index, 24-h microalbuminutia (MAU), and NAG measurements in urine samples were performed by using colorimetric assay method in an analyzer (Roche Cobas Mira). The assay defined as fragmentation of 3-cresolsulfonphthaleinyl-N-acetyl-beta-D-glucosaminide molecule by NAG to 3-cresolsulphonphthalein and N-acetylglucosamine molecules and serum creatinine were measured in all groups. Type II diabetic patients were administered perindopril (2 mg)/indapamide (0.625 mg) combination once daily for 4 months, and urinary NAG levels were measured at the end of treatment. Results. Statistically significant differences were observed between the groups I and 2 with respect to the levels of NAG and HbA1c (p < 0.05). In the treatment group, NAG levels decreased significantly (p < 0.05), whereas blood pressure and HbA1c levels did not change significantly (p > 0.05). In diabetic patients, pretreatment NAG were lowest in Group 1(A) and highest in Group 1(C), although the difference between the treatment subgroups was not statistically significant (p>0.05). Conclusion. Urinary NAG excretion is elevated in type II diabetic patients as compared with the healthy individuals. Perindopril/indapamide administration is effective in reducing urinary NAG excretion in these patients, and this effect seems to be independent from blood pressure and glycemia control. Presence of tubular proteinuria may be an early indicator of diabetic renal disease in patients without microalbuminuria. Perindopril (2 mg)/ indapamide (0.625 mg)/o.d. treatment may have beneficial effect on the tubulointerstitial damage in diabetic kidney disease.
