Urinary beta 2-microglobulin levels and urinary N-acetyl-beta-D-glucosaminidase enzyme activities in early diagnosis of non-insulin-dependent diabetes mellitus nephropathy.

To assess whether urinary N-acetyl-beta-D-glucosaminidase (NAG) and beta 2-microglobulin (beta 2-MG) levels could be used as predictors of diabetic nephropathy or not, 59 non-insulin-dependent diabetes mellitus (NIDDM) patients were included in our study (31 females, 29 males; mean age 54 +/- 10.1). The control group consisted of 20 healthy non-diabetic subjects (12 males and 8 females; mean age 47 +/- 13.9). The patients in the study group were classified according to the duration of diabetes. In all cases, urinary beta 2-MG levels were measured by specific enzyme immunoassays and urinary NAG enzyme activities were determined by colorimetric methods. The mean urinary NAG level in study group was higher than that of the control group (p < 0.01). It was observed that NAG activity begins to rise in the third year of NIDDM, makes a plateau between 3-10 years, and rapidly increases after the 10th year. No significant difference in NAG activity was found between chemical NIDDM and control groups. No significant difference in beta 2-MG levels was found between study and control groups. The mean NAG activity in patients with early glomerular hyperfiltration was significantly higher than those without early hyperfiltration and control group (p < 0.05), whereas the mean beta 2-MG level was not. As a result, urinary NAG enzyme activity significantly increases, while urinary beta 2-MG level remains unchanged in patients with NIDDM. It was concluded that measurement of urinary NAG enzyme activity may be a good indicator in early diagnosis of diabetic nephropathy.