Urinary N-acetyl-beta-D-glucosaminidase Levels Research Articles

Role of urinary NAG enzyme in early detection of renal impairment in cystic fibrosis patients

BackgroundCystic fibrosis (CF) is the most common life-limiting autosomal recessive disease among people in the USA and Europe with increased prevalence in Egypt. Affected children are in danger of acute kidney injury and the development of chronic renal disease through exposure to multiple nephrotoxic agents. N-acetyl beta-D-glucosaminidase (NAG) is a lysosomal enzyme present in high concentrations in the proximal tubular cells, thus raising urinary NAG levels to reflect tubular dysfunction. The aim of our study is to detect the role of the urinary NAG enzyme in the early detection of renal impairment in CF patients. This cross-sectional study enrolled 40 CF patients diagnosed in the CF Clinic in Children’s Hospital of Cairo University. They were age- and sex-matched to 40 healthy controls. All patients had glomerular filtration rate (GFR), serum creatinine, blood urea nitrogen (BUN), albumin/creatinine (A/C) ratio measured, urine analysis, urinary NAG enzyme using enzyme-linked immunosorbent assay (ELISA), and renal ultrasound (U/S) were done.ResultsOur study showed high levels of urinary NAG in cases with a significant difference between cases and controls (P value < 0.001). There was a significant correlation between urinary NAG enzyme elevation and A/C ratio in urine, nephrotoxic drugs administration, and duration of disease (P value = 0.002, 0.005, 0.019), respectively.ConclusionOur study suggested that the NAG enzyme is a good early detector of renal impairment in CF patients before the conventional laboratory assays become deranged.

Urinary N-acetyl-beta-d-glucosaminidase (NAG) with neutrophil gelatinase-associated lipocalin (NGAL) improves the diagnostic value for proximal tubule damage in diabetic kidney disease.

Screening for diabetic kidney disease (DKD) remains a challenge; however, there has been an ongoing research to investigate the diagnostic value of different biomarkers to identify DKD. The aim of this study was to assess the diagnostic value of both N-acetyl-beta-d-glucosaminidase (NAG) and neutrophil gelatinase-associated lipocalin (NGAL) in the progression of DKD. This cross-sectional case-control study included 92 type 2 diabetic patients with or without DKD. Urinary NAG and NGAL were measured to evaluate their diagnostic values as biochemical markers related to DKD. Both urinary NAG and NGAL levels were significantly higher among patients with DKD. In multiple linear regression analysis, NAG showed a positive significant association with NGAL in the three different adjusted models, while no significant correlation with fasting blood glucose, glycated hemoglobin, serum creatinine, estimated glomerular filtration rate, and albumin creatinine ratio were observed. The area under the curve for NGAL was 0.659 (p = 0.01) and 0.564 (p = 0.297) for NAG in DKD patients. This study demonstrates the association between urinary NAG and NGAL as a tubular damage marker for DKD although longitudinal studies are needed to evaluate its diagnostic value.

Acute Renal Graft-Versus-Host Disease in a Murine Model of Allogeneic Bone Marrow Transplantation

Acute kidney injury (AKI) is a very common complication after allogeneic bone marrow transplantation (BMT) and is associated with a poor prognosis. Generally, the kidneys are assumed to not be no direct targets of graft-versus-host disease (GvHD), and renal impairment is often attributed to several other factors occurring in the early phase after BMT. Our study aimed to prove the existence of renal GvHD in a fully major histocompatibility complex (MHC)-mismatched model of BALB/c mice conditioned and transplanted according to 2 different intensity protocols. Syngeneically transplanted and untreated animals served as controls. Four weeks after transplantation, allogeneic animals developed acute GvHD that was more pronounced in the high-intensity protocol (HIP) group than in the low-intensity protocol (LIP) group. Urea and creatinine as classic serum markers of renal function could not verify renal impairment 4 weeks after BMT. Creatinine levels were even reduced as a result of catabolic metabolism and loss of muscle mass due to acute GvHD. Proteinuria, albuminuria, and urinary N-acetyl-beta-d-glucosaminidase (NAG) levels were measured as additional renal markers before and after transplantation. Albuminuria and NAG were only significantly increased after allogeneic transplantation, correlating with disease severity between HIP and LIP animals. Histological investigations of the kidneys showed renal infiltration of T cells and macrophages with endarteriitis, interstitial nephritis, tubulitis, and glomerulitis. T cells consisted of CD4+, CD8+, and FoxP3+ cells. Renal expression analysis of allogeneic animals showed increases in indoleamine-2,3 dioxygenase (IDO), different cytokines (tumor necrosis factor α, interferon-γ, interleukin 1 α [IL-1α], IL-2, IL-6, and IL-10), and adhesion molecules (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1), resembling findings from other tissues in acute GvHD. In summary, our study supports the entity of renal GvHD with histological features suggestive of cell-mediated renal injury. Albuminuria and urinary NAG levels may serve as early markers of renal impairment.

Predictive ability of urinary biomarkers for outcome in children with acute kidney injury.

Urinary neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-beta-D-glucosaminidase (NAG), and interleukin 18 (IL-18) were found to be useful for early detection of acute kidney injury (AKI). The objective of this study was to determine the predictive ability of biomarkers for mortality and variation in levels in relation to different stages of AKI, need for dialysis, etiologies, and with duration of hospital stay. Urinary NGAL, NAG, and IL-18 levels were measured in 50 children with AKI and 30 age- and gender-matched healthy controls. AKI was classified as per pediatric Risk, Injury, Failure, Loss, and End-stage (RIFLE) criteria. Median NGAL, NAG, and IL-18 values were significantly increased in AKI patients compared with controls (p < 0.001), with significant increase among risk, injury, and failure stages. Nonsurvivors had significantly higher median levels of NGAL (p = 0.008) and NAG (p = 0.018) than survivors. NGAL had highest area under the curve (AUC) at 0.750 [confidence interval (CI) 0.580-0.920], followed by NAG at 0.724 (CI 0.541-0.907), with sensitivity and specificity of 75% each; and IL-18 (AUC 0.688, CI 0.511-0.864), with sensitivity 62.5% and specificity 70.8%, for predicting mortality. Values were significantly higher in patients who required peritoneal dialysis (PD) than in those in whom it was not indicated. Levels were comparable among different etiologies. Only NGAL level was found to be a significant risk factor associated with longer duration of hospital stay. Urinary NGAL and NAG had modest predictive ability for mortality. Children requiring dialysis had significantly raised levels, and the NGAL level had significant association with duration of hospital stay.

Evaluation of urinary N-acetyl-beta-D-glucosaminidase as a marker of early renal damage in patients with type 2 diabetes mellitus

To evaluate the clinical usefulness of urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion for the detection of early tubular damage in type 2 diabetes mellitus (T2DM). Thirty six patients with T2DM were divided into two groups based on urinary albumin to creatinine ratio (ACR): normoalbuminuria (ACR <30 mg/g; n=19) and microalbuminuria (ACR =30-300 mg/g; n=17). The following parameters were determined in both groups: urinary NAG and albumin, serum and urine creatinine, fasting plasma glucose and glycated hemoglobin (HbA1c). Urinary NAG levels [Units/g creatinine; median (range)] were significantly increased in microalbuminuria group [17.0 (5.9 - 23.3)] compared to normoalbuminuria group [4.4 (1.5 - 9.2)] (P<0.001). No differences between groups were observed in fasting glucose, HbA1c, serum creatinine levels and estimated glomerular filtration rates (eGFR). Urinary NAG positively correlated with ACR (r=0.628; p<0.0001), while no significant association was observed between NAG and glycemia, HbA1c, serum creatinine and eGFR. The increase of urinary NAG at the microalbuminuria stage of diabetic nephropathy (DN) suggests that tubular dysfunction is already present in this period. The significant positive association between urinary NAG excretion and ACR indicates the possible clinical application of urinary NAG as a complementary marker for early detection of DN in T2DM.

Early markers of obesity-related renal injury in childhood.

Childhood obesity has become a global epidemic. Recent epidemiological data suggest that obesity is associated with increased risk of renal injury in children. The onset of obesity-associated renal disease is insidious and asymptomatic, so early markers will be extremely useful in its prevention and treatment. Biomarker discovery can be focused on unbiased or biased (candidate) approaches. Unbiased approaches using innovative technologies, such as proteomics and metabolomics, have uncovered candidates that are emerging as plausible biomarkers for such renal disorders as obstructive uropathy and diabetic nephropathy. Biased approaches are based on hypotheses related to glomerular or tubular injury pathophysiology in obesity. Goknar et al. (Pediatric Nephrology 2014; doi: 10.1007/s00467-014-2829-0 ) recently evaluated early urine renal injury markers, namely, microalbuminuria, N-acetyl-beta-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin, and kidney injury molecule (KIM)-1, in obese children. They reported that obese children had higher urinary NAG and KIM-1 levels than healthy controls. Longitudinal observation studies are needed to evaluate whether these tubular damage markers are useful as early markers of renal injury in obese children.

Early and quantitative detection of cisplatin-induced nephrotoxicity by measurement of plasma PSP (phenolsulfonphthalein) half-life in rats.

Renal function following cisplatin injection in rats was assessed by measuring the half-life of plasma PSP. Changes in BUN, creatinine, plasma PSP half-life and urinary N-acetyl-beta-D-glucosaminidase (NAG) levels were determined in rats treated with 6.5 mg/kg i.v. of cisplatin. The highest values of BUN and creatinine were both observed on day 5. Half-life of plasma PSP was significantly prolonged on days 2 through 5 and reached a peak value on day 3. A significant increase in urinary NAG levels appeared on day 2 and the peak value was demonstrated on day 3. BUN, creatinine and plasma PSP half-life were also determined on days 3 and 5 following several doses of i.v. cisplatin. A dose-related increase in plasma PSP half-life was observed on day 3, while dose-related increases in BUN and creatinine levels were found on day 5. The evaluation of cisplatin-induced nephrotoxicity by the plasma PSP test was clearly superior for early detection compared with conventional renal function tests using BUN and creatinine.

Urinary Biomarkers for Sensitive and Specific Detection of Acute Kidney Injury in Humans

Acute kidney injury (AKI) is associated with high morbidity and mortality. The lack of sensitive and specific injury biomarkers has greatly impeded the development of therapeutic strategies to improve outcomes of AKI.The unique objective of this study was to evaluate the diagnostic performance of nine urinary biomarkers of AKI-kidney injury molecule-1 (KIM-1), neutrophil gelatinase associated lipocalin (NGAL), interleukin-18 (IL-18), hepatocyte growth factor (HGF), cystatin C (Cys), N-acetyl-beta-D-glucosaminidase (NAG), vascular endothelial growth factor (VEGF), chemokine interferon-inducible protein 10 (IP-10; CXCL10), and total protein-in a cross-sectional comparison of 204 patients with or without AKI.Median urinary concentrations of each biomarker were significantly higher in patients with AKI than in those without AKI (p < 0.001). The area under the receiver operating characteristics curve (AUC-ROC) for the combination of biomarkers using a logic regression model [risk score of 2.93*(NGAL > 5.72 and HGF > 0.17) + 2.93*(PROTEIN > 0.22) -2*(KIM < 0.58)] was greater (0.94) than individual biomarker AUC-ROCs. Age-adjusted levels of urinary KIM-1, NAG, HGF, VEGF, and total protein were significantly higher in patients who died or required renal replacement therapy (RRT) when compared to those who survived and did not require RRT.Our results demonstrate the comparative value of multiple biomarkers in the diagnosis and prognosis of AKI.

Effect of Renin-Angiotensin-Aldosterone System Inhibition, Dietary Sodium Restriction, and/or Diuretics on Urinary Kidney Injury Molecule 1 Excretion in Nondiabetic Proteinuric Kidney Disease: A Post Hoc Analysis of a Randomized Controlled Trial

Tubulointerstitial damage plays an important role in chronic kidney disease (CKD) with proteinuria. Urinary kidney injury molecule 1 (KIM-1) reflects tubular KIM-1 and is considered a sensitive biomarker for early tubular damage. We hypothesized that a decrease in proteinuria by using therapeutic interventions is associated with decreased urinary KIM-1 levels. Post hoc analysis of a randomized, double-blind, placebo-controlled, crossover trial. 34 proteinuric patients without diabetes from our outpatient renal clinic. Stepwise 6-week interventions of losartan, sodium restriction (low-sodium [LS] diet), their combination, losartan plus hydrochlorothiazide (HCT), and the latter plus an LS diet. Urinary excretion of KIM-1, total protein, and N-acetyl-beta-d-glucosaminidase (NAG) as a positive control for tubular injury. Mean baseline urine protein level was 3.8 +/- 0.4 (SE) g/d, and KIM-1 level was 1,706 +/- 498 ng/d (increased compared with healthy controls; 74 ng/d). KIM-1 level was decreased by using placebo/LS (1,201 +/- 388 ng/d; P = 0.04), losartan/high sodium (1,184 +/- 296 ng/d; P = 0.09), losartan/LS (921 +/- 176 ng/d; P = 0.008), losartan/high sodium plus HCT (862 +/- 151 ng/d; P = 0.008) and losartan/LS plus HCT (743 +/- 170 ng/d; P = 0.001). The decrease in urinary KIM-1 levels paralleled the decrease in proteinuria (R = 0.523; P < 0.001), but not blood pressure or creatinine clearance. 16 patients reached target proteinuria with protein less than 1 g/d, whereas KIM-1 levels normalized in only 2 patients. Urinary NAG level was increased at baseline and significantly decreased during the treatment periods of combined losartan plus HCT only. The decrease in urinary NAG levels was not closely related to proteinuria. Post hoc analysis. Urinary KIM-1 level was increased in patients with nondiabetic CKD with proteinuria and decreased in parallel with proteinuria by using losartan, sodium restriction, their combination, losartan plus HCT, and the latter plus sodium restriction. These results are consistent with the hypothesis of amelioration of proteinuria-induced tubular damage. Long-term studies are warranted to evaluate whether targeting treatment on KIM-1 can improve outcomes in patients with CKD with proteinuria.

Early markers of renal dysfunction in patients with beta-thalassemia major

Studies of renal involvement in thalassemia syndromes have been varied and few. The most important cause of mortality and morbidity in these patients is organ failure due to iron deposition. We report here a cross-sectional study carried out between February 2005 and February 2006 on all beta-thalassemia major patients being treated in Mofid Children's hospital, Tehran. The aim of the study was to detect renal dysfunction in these patients. The patient cohort consisted of 103 patients with various disease severities. Fresh first morning urine samples were collected and analyzed for sodium (Na), potassium (K), calcium (Ca), creatinine (Cr), phosphate, uric acid (UA), N-acetyl beta-D-glucosaminidase (NAG) and amino acids. We also carried out a complete blood count evaluation and assayed fasting blood sugar and serum ferritin, sodium, potassium, creatinine, uric acid and amino acids in all patients. The mean age of our patient cohort was 12.5+/-5.53 years and 53.4% were female. Abnormal levels of urinary NAG were detected in 35.9% of patients (confidence interval 26-45%). Abnormal levels of fractional excretion (FE)-Na, FE-K and FE-UA and abnormal urine protein Pr/Cr and urine Ca/Cr ratios were present in 29.1, 7.8, 52.4, 0.3 and 22.3% of the patients, respectively. There was a significant relationship between urinary NAG and the age of the patient (R=0.35), duration of deferoxamine therapy (R= 0.31), duration of receiving blood transfusions (R=0.34) and level of fasting blood sugar (R=0.2). We concluded that renal disorders are not rare in patients with beta-thalassemia major and that they may increase in terms of frequency with age, increased duration of transfusion and deferoxamine usage and high levels of blood sugar.

Urinary N-Acetyl-β-D-Glucosaminidase Levels in Patients with Laryngeal Squamous Cell Carcinoma

Tumour markers play an important role in the diagnosis of cancer and the early detection of recurrences during follow-up. This study aimed to assess the clinical value of measuring urinary N-acetyl-beta-d-glucosaminidase (U-NAG) levels in patients with laryngeal squamous cell carcinoma. Prospective, controlled study. Tertiary university hospital. Our study included 21 patients with primary laryngeal squamous cell carcinoma and 17 cases with recurrent laryngeal squamous cell carcinoma. U-NAG levels of patients with tumours at different stages were compared with a control group of 19 healthy individuals with no known cancer. Patients' age, TNM stage, blood urea, glucose, alanine aminotransferase (ALT), and U-NAG. A statistically significant difference was found between U-NAG levels of patients with a primary tumour (preoperative period) and the control group (one-way analysis of variance, p = .00; Dunnett's t-test, p = .00). In the postoperative period, the observed trend was that of a significant decrease among primary cases (paired t-test, p = .00). U-NAG levels of patients with a recurrent tumour and patients with a primary tumour (preoperative period) were not significantly different (Tukey honest significant difference test, p = .841). There was no statistically significant difference for blood urea (t = -1.95, p = .064), glucose (t = -1.84, p = .074), or ALT (t = -1.79, p = .080). No significant relationship was found between the TNM stage and preoperative U-NAG levels (p > .05). These results suggest that U-NAG might be used in the diagnosis of laryngeal carcinoma and the early detection of recurrences during follow-up. Further investigations are warranted to clarify the prognostic significance of U-NAG levels.

MELATONIN REDUCES URINARY EXCRETION OF N‐ACETYL‐β‐d‐GLUCOSAMINIDASE, ALBUMIN AND RENAL OXIDATIVE MARKERS IN DIABETIC RATS

1. Increased oxidative stress has an important role in the pathogenesis of diabetic nephropathy. The aim of the present study was to evaluate diabetic nephropathy by determining markers of oxidative stress and the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), albumin and to investigate the possible protective effects of in vivo melatonin on renal tubular oxidative damage in diabetic rats. 2. Twenty-six rats were randomly divided into three groups: (i) group I, control, non-diabetic rats (n = 9); (ii) group II, untreated diabetic rats (n = 8); and (iii) group III, melatonin-treated diabetic rats (n = 9). In groups II and III, diabetes developed 3 days after administration of a single dose of streptozotocin (35 mg/kg, i.p.). Thereafter, whereas the rats in group II received no treatment, rats in group III began to receive 10 mg/kg per day, i.p., melatonin for 8 weeks. Malondialdehyde (MDA), an index of lipid peroxidation, NAG and microalbumin in the urine, markers of renal tubular damage, were the parameters used for oxidative stress-induced renal injury. Superoxide dismutase (SOD), xanthine oxidase (XO) and glutathione peroxidase (GSH-Px) activities were determined to evaluate changes in the anti-oxidant status of kidney tissue. 3. In untreated diabetic rats, urinary NAG, albumin and renal MDA levels were markedly increased compared with control rats (P < 0.0001). However, these parameters were reduced in diabetic rats by melatonin treatment (P < 0.0001). Urinary excretion of NAG was positively correlated with the microalbuminuria and renal MDA levels (r = 0.8; P < 0.0001). The SOD and XO activities in the untreated diabetic group were found to be significantly higher than those of the control group (P < 0.0001). Superoxide dismutase and XO activities decreased in melatonin-treated rats compared with untreated diabetic rats (P < 0.002 and P < 0.023, respectively). However, the decrease did reach levels seen in control rats. There were no significant differences in GSH-Px activity between the three groups. 4. Therefore, on the basis of these data, we suggest that urinary NAG, albumin excretion, XO activity and MDA levels are more valuable parameters showing the degree of renal tubular injury than classical markers of oxidative stress, including SOD and GSH-Px, in diabetic rat kidneys. Melatonin has an ameliorating effect on oxidative stress-induced renal tubular damage via its anti-oxidant properties. Thus, it may be suggested that urinary NAG excretion and microalbuminuria may be important markers showing the degree of renal changes and the success of long-term treatment of renal impairment with melatonin.

Effects of exposure to low levels of environmental cadmium on renal biomarkers.

We conducted a study among residents of a small community contaminated with heavy metals from a defunct zinc smelter and residents from a comparison community to determine whether biologic measures of cadmium exposure were associated with biomarkers of early kidney damage. Creatinine-adjusted urinary cadmium levels did not differ between the smelter and comparison communities; thus we combined individuals from both communities (n = 361) for further analyses. The overall mean urinary cadmium level was low, 0.26 microg/g creatinine, similar to reference values observed in the U.S. general population. For children ages 6-17 years, urinary concentration of N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), and albumin were positively associated with urinary cadmium, but these associations did not remain statistically significant after adjusting for urinary creatinine and other potential confounders. For adults ages 18 or older, urinary concentration of NAG, AAP, and albumin were positively associated with urinary cadmium. The associations with NAG and AAP but not with albumin remained statistically significant after adjusting for creatinine and other potential confounders. We found a positive dose-effect relationship between levels of creatinine-adjusted urinary cadmium and NAG and AAP activity, and statistically significant differences in mean activity for these two enzymes between the highest (> or =1.0 microg cadmium/g creatinine) and the lowest (< or =0.25 microg cadmium/g creatinine) exposure groups. The findings of this study indicate that biologic measures of cadmium exposure at levels below 2.0 microg/g creatinine may produce measurable changes in kidney biomarkers.

Urinary N-acetyl-beta- d-glucosaminidase concentration in patients with spinal cord injury: relationship with urodynamic parameters

Objectives. To investigate the relationships between urinary N-acetyl-beta- d-glucosaminidase (NAG) concentrations and urodynamic parameters in patients with spinal cord injury (SCI). NAG has been proposed as a marker of renal damage. Methods. Twenty-three patients with SCI were evaluated with urodynamic studies. Urine samples were collected from the 23 patients and 10 healthy volunteers, the NAG levels were evaluated, and the urodynamic parameters were compared with the urinary NAG levels. The patients were divided into two groups according to the amplitude of the hyperreflexic detrusor contractions (HDCs): group A, patients with an HDC amplitude of 40 cm H 2O or greater, and group B, patients with an HDC amplitude of less than 40 cm H 2O; group C was composed of healthy volunteers. The urinary NAG concentrations in the three groups were compared. Results. A positive correlation was found between the urinary NAG levels and the HDC amplitude and detrusor leak point pressure ( P = 0.015 and 0.007, respectively). The urinary NAG concentration was 3.38 U/g in group A, 2.14 U/g in group B, and 2.12 U/g in group C. The differences in the urinary NAG concentrations between groups A and B and between groups A and C were statistically significant ( P = 0.03 and P <0.001, respectively). The concentrations between groups B and C were comparable. Conclusions. In our experience, the only urodynamic parameters that clearly and positively correlated with the urinary NAG levels were those expressing the amplitude of intravesical pressure. This result stresses the importance of reducing the intravesical pressure in patients with SCI using alternative treatments or surgical procedures if the usual conservative therapies are not effective.

Significant elevation of urinary 28-kD calbindin-D and N-acetyl-beta-D-glucosaminidase levels in patients undergoing extracorporeal shock wave lithotripsy.

Calbindin-D, a vitamin D-dependent calcium binding protein with a molecular mass of 28 kD, is found predominantly in distal renal tubules and central nervous system tissues in man. We have developed a highly sensitive enzyme immunoassay for human 28-kD calbindin-D and demonstrated its advantages as a new marker for damage to distal renal tubules. Urinary N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme of the proximal renal tubules, is another segment-specific indicator of renal damage. To clarify whether both proximal and distal renal tubules are similarly affected by extracorporeal shock wave lithotripsy (SWL) treatment, urinary 28-kD calbindin-D and NAG were measured before, then immediately, 2 and 24 hours after SWL in 17 renal lithiasis patients. Levels of urinary calbindin-D were markedly elevated immediately and 2 hours after SWL and then decreased. In sera, levels of calbindin-D also increased, closely correlated with the changes in urinary values. Levels of urinary NAG were also significantly elevated immediately after SWL and then decreased. The results indicate that damage to both proximal and distal renal tubules occurs simultaneously with SWL and that the two markers can be applied as sensitive indicators of such side effects and their alleviation with protective agents.

Urinary N-acetyl-beta-D-glucosaminidase activity in children with insulin-dependent diabetes mellitus.

Urinary N-acetyl-beta-D-glucosaminidase (NAG) is a sensitive indicator of renal tubular injury. The aim of the study is to determine the status of urinary NAG excretion in Chinese children with insulin-dependent diabetes mellitus (IDDM) but without any clinical evidence of nephropathy, and to try to find the possible associated factors of such tubular injury if any. Thirty-one children (8 males and 23 females) with IDDM who have normal serum creatinine, 24-hour urinary creatinine clearance and urinary total protein excretion were enrolled in the study. The mean age of the patients was 11.6 +/- 3.7 years. The random urinary NAG levels of the patients and the normal controls were 10.76 +/- 6.32 and 3.65 +/- 1.84 U/g Cr, respectively (p < 0.001). The diabetic patients were divided into 4 groups according to their duration of disease ( < 3, 3-5, 5-10 and 10-16 years). The random urinary NAG level of each group was significantly higher than that of the control group, but there was no statistically significant difference among any 2 of these 4 groups. No good correlation was noted in our study between urinary NAG and patients' age (r = -0.23, p = 0.21), serum cholesterol (r = 0.04, p = 0.84), insulin dosage (r = 0.13, p = 0.49), 24 hour urinary creatinine clearance (r= -0.41, p - 0.085) or urinary total protein excretion (r = -0.28, p = 0.26). However, the plasma HbAlc level correlated significantly with urinary NAG (r = 0.50, p < 0.01). We concluded that urinary NAG is increased in Chinese IDDM children without any clinical evidence of nephropathy. Such increased excretion is correlated with the plasma HbAlc level. Our results suggests that there is tubular dysfunction in the early stage of IDDM children even before there is any clinical evidence of nephropathy, and urinary NAG may reflect glycemic control in such patients.

Urinary angiotensin-converting enzyme activity in type 2 diabetes mellitus: its relationship to diabetic nephropathy.

Urinary angiotensin-converting enzyme (ACE) and urinary N-acetyl-beta-D-glucosaminidase (NAG) were measured after a 5-year interval in 38 non-azotemic type 2 diabetic patients. Of these patients at baseline, 16 had nil nephropathy, 15 had incipient nephropathy, and 7 had overt nephropathy. During the follow-up, 6 and 1 of the 16 patients with nil nephropathy developed incipient and overt nephropathy, respectively. Four of the 15 patients with incipient nephropathy progressed to overt nephropathy. The 7 patients with overt nephropathy continued to have overt nephropathy, with slight azotemia in one. Urinary ACE and NAG levels were normal at baseline and showed no significant elevations at follow-up in the patients with nil nephropathy, no significant changes in baseline and modest elevations at follow-up in the patients with incipient nephropathy, and high at baseline and marked elevations at follow-up in the patients with overt nephropathy. In all patients, urinary ACE during the follow-up was positively correlated with urinary albumin or NAG, but not with glomerular filtration rate. Urinary ACE may be of poor prognostic value for the follow-up of diabetic patients, which is at variance with urinary albumin.

Urinary enzyme excretion as a parameter for detection of acute renal damage mediated by N-(3,5-dichlorophenyl)succinimide (NDPS) in Fischer 344 rats.

The kidney has been identified as the specific target organ for in vivo exposure to an agricultural fungicide, N-(3,5-dichlorophenyl)succinimide (NDPS). The goal of this study was to determine if urinary protein and enzyme excretion were sensitive, non-invasive markers for NDPS-induced renal damage. The proximal tubular enzymes that were monitored were the brush-border enzyme alkaline phosphatase (ALP) and the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAG). Male Fischer 344 (F344) rats were injected intraperitoneally (i.p.) with 0.2 or 1.0 mmol kg-1 NDPS. Control animals were injected i.p. with sesame oil (2.5 ml kg-1). Urine was collected on ice 0-3, 3-6 and 6-24 h after NDPS or vehicle injection. Urinary protein and urinary NAG excretion levels were elevated (P < 0.05) above the control levels 0-3 h after treatment with 0.2 mmol kg-1 NDPS. Urinary protein and enzyme excretion was comparable between 0.2 mmol kg-1 NDPS-treated and control groups for all other time periods. Administration of a marked nephrotoxicant dose (1.0 mmol kg-1) was associated with elevated levels of urinary protein, NAG and ALP beginning 0-3 h after treatment when compared to the control group or to respective baseline values. It was concluded from these studies that measurement of urinary protein as well as the release of ALP and NAG were sensitive markers of renal damage produced by NDPS.

Differential excretion of urinary proteins in children with vesicoureteric reflux and reflux nephropathy.

We studied 40 children with a history of vesicoureteric reflux (VUR) without evidence of renal scarring, 93 children with a history of VUR and renal scarring and 10 children with previous urinary tract infections in whom the urinary tract was radiologically normal. Urine retinol-binding protein (RBP), albumin and N-acetyl-beta-D-glucosaminidase (NAG) were measured in each child. All were free from infection at the time of the analysis. Urinary RBP and NAG levels were significantly elevated (P < 0.001) in the group of children with renal scarring. Elevated RBP levels were detected in 51% of children with bilateral renal scarring compared with 7% of children with unilateral scarring. Urine RBP excretion increased progressively according to the type of scarring, best determined by the type of scarring of the less affected kidney. In children with renal scarring, elevated NAG levels were seen mostly in the 65 children with bilateral scarring and severe reflux. Urine albumin excretion was elevated in 10 children, 9 with bilateral scarring, all of whom had elevated RBP excretion. Urine protein excretion was unaffected by the presence or absence of persisting VUR. There was a strong negative correlation between glomerular filtration rate and RBP excretion (r = -0.69). We conclude that evidence of tubular dysfunction is common in children with bilateral renal scarring and usually precedes any glomerular protein leak. Tubular dysfunction may be the consequence of relative nephron hyperperfusion in the presence of bilateral scarring.

Urinary Levels of Renal Tubular Enzyme N-Acetyl-β-D-Glucosaminidase in Relation to Grade of Vesicoureteral Reflux

Elevated urinary levels of the renal tubular enzyme N-acetyl-beta-D-glucosaminidase (NAG) have been shown to be associated with tubular damage. To determine whether urinary levels of NAG would be abnormal and/or vary with the severity of vesicoureteral reflux, bladder urine was obtained from 31 children without reflux and 32 children with various grades of reflux. Nonrefluxing controls were obtained from children undergoing evaluation for a history of infection, hematuria or voiding abnormality. Patients with evidence of obstruction, neuropathic bladder dysfunction, urinary tract infection or renal failure were excluded. Bladder (32 cases) and ureteral (5 cases) urine from children with reflux was obtained at cystography or at antireflux surgery. Control and reflux patients were not significantly different with regard to sex or age. The mean urinary NAG level in nonrefluxing control patients was 10.63 IU/mg. (range 0.94 to 26.61, standard error of mean 0.43). Mean urinary NAG for all patients with reflux was 16.47 IU/mg. (range 2.85 to 52.02, standard error of mean 0.9). Two children with intrarenal reflux had urinary NAG levels of 52 and 48 IU/mg. Urinary NAG levels are elevated with higher grades of reflux and this relatively simple assay may have clinical usefulness in the assessment of tubular dysfunction associated with reflux.