The differential diagnostic value of urinary enzyme and amino acid excretion in children with nephrotic syndrome

Diabetic nephropathy: traditional to proteomic markers

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes and it is defined as a rise in the urinary albumin excretion (UAE) rate and abnormal renal function. Currently, changes in albuminuria are considered a hallmark of onset or progression of DN. However, some patients with diabetes have advanced renal pathological changes and progressive kidney function decline even if urinary albumin levels are in the normal range, indicating that albuminuria is not the perfect marker for the early detection of DN. The present article provides an overview of the literature reporting some relevant biomarkers that have been found to be associated with DN and that potentially may be used to predict the onset and/or monitor the progression of nephropathy. In particular, biomarkers of renal damage, inflammation, and oxidative stress may be useful tools for detection at an early stage or prediction of DN. Proteomic-based biomarker discovery represents a novel strategy to improve diagnosis, prognosis and treatment of DN; however, proteomics-based approaches are not yet available in most of the clinical chemistry laboratories. The use of a panel with a combination of biomarkers instead of urinary albumin alone seems to be an interesting approach for early detection of DN, including markers of glomerular damage (e.g., albumin), tubular damage (e.g., NAG and KIM-1), inflammation (e.g., TNF-α) and oxidative stress (e.g., 8-OHdG) because these mechanisms contribute to the development and outcomes of this disease.

Is the urinary protein excretion pattern compatible with renal morphological findings in renal amyloidosis?

The aims of this study are to compare urinary protein excretion pattern with renal morphological findings and to find out whether urinary protein excretion pattern is a prognostic indicator of renal amyloidosis. Fifteen children with renal amyloidosis secondary to familial Mediterranean fever were included in the study. The patients were classified into three groups according to the degree of tubulointerstitial injury in renal biopsy (group 1, <25%; group 2, 25-50%; and group 3, >50%). In all patients, urinary protein electrophoresis were performed. Levels of urinary beta(2)-microglobulin, retinol binding protein, and beta.N-acetyl-D glucosaminidase were measured as markers for tubular injury, and urinary excretions of protein and albumin and plasma albumin levels were measured as markers of glomerular injury. While urinary excretions of protein and albumin and plasma albumin levels were not different between groups, higher urinary beta(2-)microglobulin and retinol binding protein values and lower creatinine clearance values were found in group 3 than in groups 1 and 2 (p < 0.05). We concluded that analysis of urinary protein excretion pattern is a non-invasive and reliable method to detect the degree of tubulointerstitial injury as the most important prognostic factor in renal amyloidosis and may be used to determine the changes during the follow-up period of the patients.

[Damage to proximal tubular epithelial cells in type 2 diabetes mellitus]

INTRODUCTION

Kidney damage from diabetes mellitus is called diabetic nephropathy. At the beginning it is a functional disorder, but later it results in an irreversible damage. The aim of this research was to establish damage to proximal tubular cells in patients with type 2 diabetes mellitus, and various degrees of proteinuria by determining the urinary N-acetyl-beta-D-glucose-aminidase and gamma-glutamyl-transferase; to compare obtained results with the results in healthy examinees; to establish the correlation between these enzymes, and to investigate their sensitivity.

MATERIAL AND METHODS

Patients with type 2 diabetes mellitus and creatinine clearence >80 ml/min were included in the research. Patients were divided into three groups, according to the degree of proteinuria. The first group included diabetics without microalbuminuria; the second--patients with proteinuria <300 mg/24 h and microalbuminuria >20 mg/24 h, and the third group included patients with proteinuria >300 mg/24 h. Healthy examinees were the control group.

RESULTS

Values of the urinary N-acetyl-beta-D-glucosaminidase activity were elevated before microalbuminuria was observed. The highest values were detected in the group of patients with microalbuminuria. Differences among the examined groups were statistically significant, which implies that this enzyme has a high diagnostic importance. Enzyme gamma-glutamyl-transferase was less sensitive in this research. The activity of this enzyme was increased only in the group of patients with proteinuria >300 mg/24h, where values increased with diabetes mellitus duration.

CONCLUSION

The increased activity of urinary N-acetyl-beta-D-glucosaminidase points to early tubular damage, and can be used as a sensitive parameter in its early detection. On the other hand, gamma-glutamyl-transferase was a less sensitive damage indicator.

Damage of tubule cells in diabetic nephropathy type 2: urinary N-acetyl-beta-D-glucosaminidasis and gamma-glutamil-transferasis

BACKGROUND/AIM

A damage of tubular epithelial cells is followed by the release of cell enzymes and production of proinflammatory compounds, which lead to the tubulointerstitial damage. The aim of this study was to examine the function of renal tubules in the patients with diabetes mellitus type 2 (DM type 2) and the various proteinuria degrees, to establish the damage of the proximal tubule cells caused by DM type 2 by determining urinary N-acetyl-beta-D-glucosaminidasis (beta-NAG) and gamma-glutamil-transferasis (gamma-GT) activity in urine, as well as to compare the obtained results in the examined groups of patients with the values in the healthy examinees.

METHODS

A complete examination of renal function and selective enzymuria was performed in 37 patients with DM type 2, and 14 healthy examinees as the controls. The patients were divided in three groups according to the degree of proteinuria. The first group consisted of the patients with diabetes without microalbuminuria; the second one consisted of the patients with proteinuria of < 300 mg/24 h, and microalbuminuria of > 20 mg/24 h, while the third one included the patients with proteinuria of > 300 mg/24 h.

RESULTS

In the patients with DM type 2 and the preserved global renal function, fractional excretion of sodium, potassium and phosphates, as well as renal threshold of phosphates concentration, were not sensitive parameters for discovering the damage of the renal tubule function. The determination of beta-NAG activity proved to be the most sensitive parameter for early discovering of tubule cells damages. The difference among the examined groups was statistically highly significant.

CONCLUSION

The increased presence of beta-NAG in the urine of DM type 2 patients, pointed out an early tubular disorder and damage of cells, while gamma-GT was a less sensitive indicator of this damage.