Increased urinary excretion of N-acetylglucosaminidase in subjects with impaired glucose tolerance

Pulicaria crispa mitigates nephrotoxicity induced by carbon tetrachloride in rats via regulation oxidative, inflammatory, tubular and glomerular indices

CONTEXT

Carbon tetrachloride (CCl₄) induces oxidative stress in various tissues by altering antioxidants defense system. Recently, there has been a substantial use of phytotherapy to treat different diseases.

OBJECTIVE

This study was designed to evaluate the curative effect of Pulicaria crispa (Forssk.) Benth et Hook (Family Asteraceae) aerial parts ethanol extract against CCl₄ induced toxicity in rats kidneys.

MATERIALS AND METHODS

Nephrotoxicity was induced by intraperitoneal injection with CCl₄ in a dose of 0.5 mL/kg b.wt./twice a week for six consecutive weeks. Serum kidney function tests, oxidative stress markers, inflammatory cytokines, nephrotoxicity biomarkers and histopathological observation were evaluated.

RESULTS

CCl₄ increased serum kidney function parameters, malondialdehyde level, inflammatory cytokines, and nephrotoxicity markers, while decreased certain oxidative stress indices as superoxide dismutase and glutathione refereeing to the control group (p < 0.0001). Administration of P. crispa ethanol extract to CCl₄ injured rats attenuated these changes with variable degrees. The results were confirmed through the observed amelioration of the renal histological architectures.

CONCLUSION

P. crispa ethanol extract possesses potent curative effect against CCl₄-induced nephropathy through improvement of kidney function, oxidative stress, inflammatory and nephrotoxicity index and the renal histopathological features. To establish the therapeutic and pharmacological applications of the plant, additional researches are required.

Tubular and Glomerular Biomarkers of Acute Kidney Injury in Newborns

BACKGROUND

Acute Kidney Injury (AKI) is a sudden decrease in kidney function. In the early period, the highest percentage of AKI occurs among newborns hospitalized in the neonatal intensive care units, especially premature neonates. The prognosis of AKI depends on the type and severity of the cause of an injury, the accuracy and the time of diagnosis and treatment. The concentration of serum creatinine is still the main diagnostic test, although it changes in the course of AKI later than glomerular filtration rate GFR. In addition, the reliability of the determination of creatinine level is limited because it depends on many factors. New studies have presented other, more useful laboratory markers of renal function that can be measured in serum and/or in urine.

OBJECTIVE

The aim of the work was to present the latest data about tubular and glomerular biomarkers of acute kidney injury in newborns.

METHODS

We undertook a structured search of bibliographic databases for peer-reviewed research literature by using focused review topics. According to the conceptual framework, the main idea of research literature has been summarized and presented in this study.

RESULTS

The concentrations of some novel biomarkers are higher in serum and/or urine of term and preterm newborns with AKI, especially in the course of perinatal asphyxia.

CONCLUSION

In this systematic review of the literature, we have highlighted the usefulness of biomarkers in predicting tubular and/or glomerular injury in newborns. However, novel biomarkers need to prove their clinical applicability, accuracy, and cost-effectiveness prior to their implementation in clinical practice.

Clinical prospects of biomarkers for the early detection and/or prediction of organ injury associated with pharmacotherapy

Several biomarkers are used to monitor organ damage caused by drug toxicity. Traditional markers of kidney function, such as serum creatinine and blood urea nitrogen are commonly used to estimate glomerular filtration rate. However, these markers have several limitations including poor specificity and sensitivity. A number of serum and urine biomarkers have recently been described to detect kidney damage caused by drugs such as cisplatin, gentamicin, vancomycin, and tacrolimus. Neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid-binding protein (L-FABP), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein-1 (MCP-1), and cystatin C have been identified as biomarkers for early kidney damage. Hy's Law is widely used as to predict a high risk of severe drug-induced liver injury caused by drugs such as acetaminophen. Recent reports have indicated that glutamate dehydrogenase (GLDH), high-mobility group box 1 (HMGB-1), Keratin-18 (k18), MicroRNA-122 and ornithine carbamoyltransferase (OCT) are more sensitive markers of hepatotoxicity compared to the traditional markers including the blood levels of amiotransferases and total bilirubin. Additionally, the rapid development of proteomic technologies in biofluids and tissue provides a new multi-marker panel, leading to the discovery of more sensitive biomarkers. In this review, an update topics of biomarkers for the detection of kidney or liver injury associated with pharmacotherapy.

Urinary neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, N-acetyl-β-D-glucosaminidase levels and mortality risk in septic patients with acute kidney injury

INTRODUCTION

The aim of the study was to confirm whether higher levels of urinary neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1) and N-acetyl-β-D-glucosaminidase (NAG) are associated with mortality risk scores in severe septic patients with acute kidney injury (AKI).

MATERIAL AND METHODS

A prospective observational study was performed in an adult critical care unit. A total of 135 patients were included. The levels of urinary NGAL, KIM-1 and NAG were compared between patients with acute physiology and chronic health evaluation (APACHE II) score > 25 (group A, n = 31) and APACHE II score ≤ 25 (group B, n = 104).

RESULTS

Median level of NGAL was 105.1 ng/ml (77.6-132.5) in group A versus 40.0 ng/ml (18.6-60.5) in group B (p < 0.001), KIM-1 was 16.2 ng/ml (10.2-22.3) versus 3.3 ng/ml (1.8-4.6) (p < 0.001), and NAG was 32.0 U/l (17.5-46.4) versus 15.0 U/l (7.7-22.3) (p < 0.001). The area under the receiver operating characteristic curve for NGAL was 0.70 (95% CI: 0.60-0.79), KIM-1 was 0.75 (95% CI: 0.66-0.83), and NAG was 0.69 (95% CI: 0.60-0.79). A NGAL level > 102.5 ng/ml had 95% sensitivity and 76% specificity, KIM-1 > 7.3 ng/ml had 96% sensitivity and 61% specificity, and NAG > 15.4 U/l had 86% sensitivity and 74% specificity.

CONCLUSIONS

In severe septic AKI patients, high levels of NGAL, KIM-1 and NAG are associated with mortality risk scores. Urinary NGAL, KIM-1 and NAG concentrations higher than 102.5 ng/ml, 7.3 ng/ml and 15.4 U/l respectively may be used to predict increased of death risk scores.

Associations between Urinary Excretion of Cadmium and Renal Biomarkers in Nonsmoking Females: A Cross-Sectional Study in Rural Areas of South China

OBJECTIVES

The aim of this study was to systematically evaluate the relationship between urinary excretion of cadmium (U-Cd) and biomarkers of renal dysfunction.

METHODS

One hundred eighty five non-smoking female farmers (aged from 44 to 71 years) were recruited from two rural areas with different cadmium levels of exposure in southern China. Morning spot urine samples were collected for detecting U-Cd, urinary creatinine (U-cre), β₂-microglobulin (β₂-MG), α₁-microglobulin (α₁-MG), metallothionein (MT), retinol binding protein (RBP), albumin (AB), N-acetyl-β-D-glucosaminidase (NAG), alkaline phosphatase (ALP), γ-glutamyl transpeptidase (GGT) and kidney injury molecule-1 (KIM-1). Spearman's rank correlation was carried out to assess pairwise bivariate associations between continuous variables. Three different models of multiple linear regression (the cre-corrected, un-corrected and cre-adjusted model) were used to model the dose-response relationships between U-Cd and nine urine markers.

RESULTS

Spearman's rank correlation showed that NAG, ALP, RBP, β₂-MG and MT were significantly associated with U-Cd for both cre-corrected and observed data. Generally, NAG correlated best with U-Cd among the nine biomarkers studied, followed by ALP and MT. In the un-corrected model and cre-adjusted model, the regression coefficients and R² of nine biomarkers were larger than the corresponding values in the cre-corrected model, indicating that the use of observed data was better for investigating the relationship between biomarkers and U-Cd than cre-corrected data.

CONCLUSIONS

Our results suggest that NAG, MT and ALP in urine were better biomarkers for long-term environmental cadmium exposure assessment among the nine biomarkers studied. Further, data without normalization with creatinine show better relationships between cadmium exposure and renal dysfunction.

Urinary kidney biomarkers for early detection of nephrotoxicity in clinical drug development

Early detection of drug-induced kidney injury is vital in drug development. Generally accepted biomarkers such as creatinine and blood urea nitrogen (BUN) lack sensitivity and early injury responses are missed. Many new biomarkers to detect nephrotoxicity for pre-clinical utilization have been described and their use is adopted in regulatory guidelines. However, guidance on appropriate biomarkers for clinical trials is minimal. We provide an overview of potentially useful kidney biomarkers that can be used in clinical trials. This includes guidance to select biomarkers suitable to capture specific characteristics of the (expected) kidney injury. We conclude that measurement of urinary kidney injury marker-1 (KIM-1) serves many purposes and is often an appropriate choice. Cystatin C captures effects on glomerular filtration rate (GFR), but this marker should preferably be combined with more specific markers to localize the origin of the observed effect. Untoward effects on tubules can be captured relatively well with several markers. Direct detection of glomerular injury is currently impossible since specific biomarkers are lacking. Indirect assessment of toxic effects on glomeruli is possible by using carefully selected panels of other injury markers. We conclude that it is possible to obtain appropriate information on nephrotoxicity in clinical drug development by using carefully selected panels of injury markers and suggest that identification and validation of specific glomerular biomarkers could be of great value.

Determination of early urinary renal injury markers in obese children

BACKGROUND

Obesity is an important health issue, the prevalence of which is increasing in childhood. The aim of this study was to examine urinary renal injury markers in order to determine the renal effect of obesity and its comorbidities in a pediatric population.

METHODS

Eighty-four obese children and 64 healthy control subjects were enrolled in the study. We checked their urine using N-acetyl-beta-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and microalbumin as renal injury markers. Associations of renal damage markers with hypertension, an impaired glucose tolerance test, and insulin resistance were assessed.

RESULTS

Obese individuals had higher urinary NAG and KIM-1 values compared to those of healthy controls (p = 0.027, p = 0.026). There was no difference in urinary NGAL between obese and lean subjects (p = 0.885). Urinary renal injury markers were not statistically different in the obese group when checked for impaired glucose tolerance, insulin resistance, and hypertension (p > 0.05).

CONCLUSIONS

This study shows that urinary NAG and KIM-1 could be used as a screening method for detection of early renal damage in obese children.

Evaluation of the usefulness of novel biomarkers for drug-induced acute kidney injury in beagle dogs

As kidney is a major target organ affected by drug toxicity, early detection of renal injury is critical in preclinical drug development. In past decades, a series of novel biomarkers of drug-induced nephrotoxicity were discovered and verified in rats. However, limited data regarding the performance of novel biomarkers in non-rodent species are publicly available. To increase the applicability of these biomarkers, we evaluated the performance of 4 urinary biomarkers including neutrophil gelatinase-associated lipocalin (NGAL), clusterin, total protein, and N-acetyl-β-D-glucosaminidase (NAG), relative to histopathology and traditional clinical chemistry in beagle dogs with acute kidney injury (AKI) induced by gentamicin. The results showed that urinary NGAL and clusterin levels were significantly elevated in dogs on days 1 and 3 after administration of gentamicin, respectively. Gene expression analysis further provided mechanistic evidence to support that NGAL and clusterin are potential biomarkers for the early assessment of drug-induced renal damage. Furthermore, the high area (both AUCs=1.000) under receiver operator characteristics (ROC) curve also indicated that NGAL and clusterin were the most sensitive biomarkers for detection of gentamicin-induced renal proximal tubular toxicity. Our results also suggested that NAG may be used in routine toxicity testing due to its sensitivity and robustness for detection of tissue injury. The present data will provide insights into the preclinical use of these biomarkers for detection of drug-induced AKI in non-rodent species.

A basic science view of acute kidney injury biomarkers

Over the last decade, significant progress has been made in the identification and validation of novel biomarkers as well as refinements in the use of serum creatinine as a marker of kidney function. These advances have taken advantage of laboratory investigations, which have identified these novel molecules that serve important biological functions in the pathogenesis of acute kidney injury (AKI). As we advance and validate these markers for clinical studies in AKI, we recognize that they serve not only to improve our understanding of AKI, but they could also serve as potential targets for the treatment of AKI. This review will underscore the biological basis of specific biomarkers that will contribute to the advancement in the treatment and outcomes of AKI.

Urinary N-acetyl-β-D-glucosaminidase levels are positively correlated with 2-hr plasma glucose levels during oral glucose tolerance testing in prediabetes

BACKGROUND

Urinary N-acetyl-β-D-glucosaminidase (NAG) excretion is increased in patients with impaired glucose tolerance (IGT). This study investigated when during the oral glucose tolerance test (OGTT) the plasma glucose, urine glucose, and insulin levels correlate most strongly with urinary N-acetyl-β-d-glucosaminidase (NAG) levels in prediabetic subjects.

METHODS

The OGTT was administered to 80 subjects who had not yet received a diagnosis of diabetes mellitus (DM) and in whom HbA1c levels were ≤6.8% and fasting plasma glucose levels were <7.0 mmol/l. Forty-two subjects had normal glucose tolerance (NGT), 31 had impaired glucose tolerance (IGT), and 7 had DM according to World Health Organization criteria. Serum levels of cystatin C, the estimated glomerular filtration rate, the urinary albumin-to-creatinine (Cr) ratio, urinary and serum β2-microglobulin, and urinary NAG were measured as markers of renal function.

RESULTS

NAG levels were significantly higher in subjects with DM and in subjects with IGT than in subjects with NGT. No significant associations were observed between glycemic status and other markers of renal function. Multiple linear regression analysis showed that the NAG level was positively correlated with plasma glucose levels at 120 min of the OGTT and was associated with the glycemic status of prediabetic patients.

CONCLUSION

These results suggest that postprandial hyperglycemia is an independent factor that causes renal tubular damage in prediabetes patients.

Preclinical perspective of urinary biomarkers for the detection of nephrotoxicity: what we know and what we need to know

The assessment of kidney damage is a challenge and must incorporate assessment of the functional capacity of the kidney, as well as a comprehensive understanding of the kidney's role. Multiple parameters have been used for many years to measure renal functionality to assess renal damage. It is astonishing that, beside histopathology, the most common traditional parameters are serum based. However, urine is also used to obtain additional information regarding the health status of the kidneys. Since 2008, several novel urinary protein biomarkers have been qualified by the US FDA and the European Medicines Agency in conjunction with the Predictive Safety Testing Consortium in a specially developed qualification process. Subsequently, the Pharmaceuticals and Medical Devices Agency accepted the qualification of these seven urinary biomarkers. This review will give an overview of the state-of-the-art detection based on urinary biomarkers, which will enhance toxicological research in the future. In addition, the qualification process that leads to acceptance of these biomarkers will be described because of its uniqueness and importance for the field of biomarker research.

Urinary N-Acetyl B Glucosaminidase as an Earlier Marker of Diabetic Nephropathy and Influence of Low-Dose Perindopril/Indapamide Combination

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 1A (n = 15) < or = 3 years, Group 1B (n = 19) 3 to 5 years, and Group 1c (n = 16) > 5 years. The inclusion criteria were no prior use of antihypertensive 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 microalbuminuria (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 1 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 1A and highest in Group 1c, 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.

Biomarkers of acute kidney injury

Acute kidney injury (AKI) is a common condition with a high risk of death. The standard metrics used to define and monitor the progression of AKI, such as serum creatinine and blood urea nitrogen levels, are insensitive, nonspecific, and change significantly only after significant kidney injury and then with a substantial time delay. This delay in diagnosis not only prevents timely patient management decisions, including administration of putative therapeutic agents, but also significantly affects the preclinical evaluation of toxicity thereby allowing potentially nephrotoxic drug candidates to pass the preclinical safety criteria only to be found to be clinically nephrotoxic with great human costs. Studies to establish effective therapies for AKI will be greatly facilitated by two factors: (a) development of sensitive, specific, and reliable biomarkers for early diagnosis/prognosis of AKI in preclinical and clinical studies, and (b) development and validation of high-throughput innovative technologies that allow rapid multiplexed detection of multiple markers at the bedside.

Biomarkers of nephrotoxic acute kidney injury

Acute kidney injury (AKI) is a common condition with significant associated morbidity and mortality. Epidemiologic data suggest that a significant proportion of AKI cases is at least partially attributable to nephrotoxin exposure. This is not surprising given intrinsic renal susceptibility to toxicant-induced injury, a consequence of the unique physiologic and biochemical properties of the normally functioning kidney. A number of pathophysiologic mechanisms have been identified that mediate toxic effects on the kidney, resulting in a variety of clinical syndromes ranging from subtle changes in tubular function to fulminant renal failure. Unfortunately, standard metrics used to diagnose and monitor kidney injury, such as blood urea nitrogen and serum creatinine, are insensitive and nonspecific, resulting in delayed diagnosis and intervention. Considerable effort has been made to identify biomarkers that will allow the earlier diagnosis of AKI. Further characterization of these candidate biomarkers will clarify their utility in the setting of acute nephrotoxicity, define new diagnostic and prognostic paradigms for kidney injury, facilitate clinical trials, and lead to novel effective therapies.

Effects of pentoxifylline administration on urinary N-acetyl-beta-glucosaminidase excretion in type 2 diabetic patients: a short-term, prospective, randomized study

BACKGROUND

Tubulointerstitial injury is a major feature of diabetic nephropathy and an important predictor of renal dysfunction. In 45 patients with type 2 diabetes mellitus (DM), we prospectively analyzed urinary excretion of N-acetyl-beta-glucosaminidase (NAG), a marker of tubular renal damage; the potential relationship with urinary protein excretion; and effects of pentoxifylline (PTF) administration.

METHODS

Forty-five patients with type 2 DM initially were compared with 15 healthy controls matched for age and sex. After randomization, PTF (1,200 mg/d) was administered for 4 months to 30 patients and results were compared with data from a control group (n = 15).

RESULTS

Proteinuria and urinary NAG excretion were significantly greater in patients with DM with respect to healthy controls. Before PTF administration, baseline parameters were similar in both groups of patients with DM. At the end of the study, urinary protein excretion and NAG-creatinine ratios decreased in the active group from 920 +/- 522 mg/d and 14.3 +/- 16.9 U/g to 803 +/- 523 mg/d (P < 0.001) and 10.5 +/- 9.3 U/g (P < 0.05), respectively. Conversely, proteinuria and urinary NAG excretion did not change in the control group. Regression analysis showed that urinary NAG excretion was significantly associated with duration of DM (r = 0.61; P < 0.001) and proteinuria (r = 0.51; P < 0.001).

CONCLUSION

Urinary NAG excretion is elevated in patients with type 2 DM compared with healthy individuals and increases as nephropathy progresses. PTF administration is effective in reducing proteinuria and urinary NAG excretion in these patients. These findings suggest that PTF may have beneficial effects on tubulointerstitial damage in diabetic kidney disease.