Urinary excretion of glycosaminoglycans and brush border and lysosomal enzymes as markers of glomerular and tubular involvement in kidney diseases

Low molecular weight heparin may benefit nephrotic remission in steroid‑sensitive nephrotic syndrome via inhibiting elastase

Low molecular weight heparin (LMWH) has a structure similar to heparan sulfate, which exerts anti-inflammatory effects via inhibiting elastase (Ela) activity. Release of Ela along the glomerular capillary wall may induce glomerular injury and proteinuria. The present study aimed to investigate the influence of LMWH on steroid-sensitive nephrotic syndrome (SSNS) and the potential underlying mechanism. A total of 40 SSNS patients and 20 healthy controls were recruited. SSNS patients were treated with LMWH and prednisone simultaneously (LMWH+pred group) or with prednisone alone (pred group). Proteinuria, urinary glycosaminoglycans (GAGs), serum Ela and urinary creatinine levels were measured. The nephrotic period of SSNS was 15.93±5.78 days. The nephrotic period of SSNS in LMWH+pred group was significantly reduced compared with the pred group (14.13±4.56 vs. 18.63±6.49 days; P<0.05). At the follow-up of the SSNS patients, there was no statistically significant difference in number of relapses between the LMWH+pred and pred groups. Proteinuria (2.51±0.97 g/24 h), urinary GAG levels (4.92±0.87 mg/mmol creatinine) and serum Ela levels (77.64±10.99 ng/l) were significantly greater in the nephrotic period of SSNS compared with the remission period (0.107±0.026 g/24 h, 1.53±0.27 mg/mmol Cr and 41.92±7.81 ng/l, respectively) and the healthy control group (0.098±0.027 g/24 h, 1.40±0.26 mg/mmol creatinine and 38.43±9.83 ng/l, respectively; P<0.05). During the remission period, urinary GAG and serum Ela levels in the LMWH+pred group were significantly reduced compared with the pred group (P<0.05), whereas proteinuria did not differ between these groups (P>0.05). Positive correlations were revealed between urinary GAG excretion and proteinuria (r=0.877; P<0.05), proteinuria and serum Ela levels (r=0.844; P<0.05) and serum Ela levels and urinary GAG excretion (r=0.881; P<0.05). The results of the present study indicated that elevated serum Ela levels may induce proteinuria by degrading GAGs in the glomerular basement membrane in children with SSNS. LMWH may benefit nephrotic remission of SSNS via inhibiting Ela.

Significance of urinary glycosaminoglycans/proteoglycans in the evaluation of type 1 and type 2 diabetes complications

Because of the high incidence of kidney disease in diabetic patients, the early diagnosis of renal impairment is a key point for intervention and management. Although urinary albumin excretion currently represents the accepted standard to assess both diabetic nephropathy and cardiovascular risk, it has some limitations as structural changes in the glomerular basement membrane may occur before the onset of microalbuminuria. It is therefore important to identify urinary markers that may provide greater sensitivity, earlier detection, and greater predictive power for diabetes complications. In this respect, urinary glycosaminoglycans/proteoglycans (GAGs/PGs) have been long associated with several kidney diseases as well as diabetic nephropathies as their levels increase more readily than albuminuria. In particular, heparan sulfate, a key component of the glomerular basement membrane responsible for its charge-dependent permeability, is excreted into urine at higher concentrations during the early kidney remodeling events caused by the altered glucose metabolism in diabetes. Over the past few years, also urinary trypsin inhibitor has been linked to a chronic inflammatory condition in both type 1 and 2 diabetes. The underlying mechanisms of such increase are not completely known since either a systemic inflammatory condition or a more localized early renal impairment could play a role. Nevertheless, the association with other inflammatory markers and a detailed urinary trypsin inhibitor structural characterization in diabetes remain to be elucidated. This review will discuss a great deal of information on the association between urinary GAGs/PGs and type 1 and 2 diabetes, with particular emphasis on renal involvement, and their potential as markers useful in screening, diagnosis and follow up to be associated with the current standard tests.

Secreted klotho and chronic kidney disease

Soluble Klotho (sKl) in the circulation can be generated directly by alterative splicing of the Klotho transcript or the extracellular domain of membrane Klotho can be released from membrane-anchored Klotho on the cell surface. Unlike membrane Klotho which functions as a coreceptor for fibroblast growth factor-23 (FGF23), sKl, acts as hormonal factor and plays important roles in anti-aging, anti-oxidation, modulation of ion transport, and Wnt signaling. Emerging evidence reveals that Klotho deficiency is an early biomarker for chronic kidney diseases as well as a pathogenic factor. Klotho deficiency is associated with progression and chronic complications in chronic kidney disease including vascular calcification, cardiac hypertrophy, and secondary hyperparathyroidism. In multiple experimental models, replacement of sKl, or manipulated up-regulation of endogenous Klotho protect the kidney from renal insults, preserve kidney function, and suppress renal fibrosis, in chronic kidney disease. Klotho is a highly promising candidate on the horizon as an early biomarker, and as a novel therapeutic agent for chronic kidney disease.

Ability of low-molecular-weight heparin to alleviate proteinuria by inhibiting respiratory syncytial virus infection

AIM

Low-molecular-weight heparin (LMWH) is a negatively charged glycoprotein and has a very similar structure to that of cell surface heparin sulfate (HS). Thus, LMWH, an analog of HS, may inhibit positively charged respiratory syncytial virus (RSV) infection through cooperative electrostatic association.

METHODS

In this study, rats were respectively treated with 400 IU/kg LMWH before, during or after being inoculated with 6 x 10(6) plaque-forming unit (PFU) RSV. RSV and normal control groups were respectively inoculated by RSV and virus-free Dulbecco's modified Eagle's medium (DMEM). HeLa cells in vitro were pretreated with LMWH, elastase (ELA), heparinase (HpaIII) and protamine before being inoculated with 6 x 10(1) PFU RSV. RSV infectivity was determined by in situ hybridization and plaque assay.

RESULTS

After inoculation, the urinary protein excretion and serum parameters in LMWH-treated rats were significantly lower than those in the RSV group. No abnormalities of glomerular structure were observed in LMWH-treated groups whereas swelling and slight hypercellularity in minority glomeruli and foot process effacement were observed in the RSV group. RSV RNA of LMWH-treated rats had weaker expression than that of the RSV group. In vitro, RSV infection in RSV + LMWH, HpaIII + ELAI, protamine + ELAI, ELAI, HpaIII and protamine treatment cells were significantly lower than that of the RSV control, and that in RSV + LMWH was the least. There were no significant differences in RSV infection between ELAI + LMWH and RSV control.

CONCLUSION

Our study confirmed that there is a correlation between RSV and proteinuria in rats. LMWH can alleviate proteinuria in rats through inhibiting RSV from binding with HS which plays an important role in the onset of RSV infection.

Glycosaminoglycan excretion in children with nephrotic syndrome

Although most childhood nephrotic syndromes respond to steroid treatment, steroid resistant nephrotic syndrome (SRNS) is also common and is particularly difficult to treat. This study investigated the role of glycosaminoglycans (GAG) in the pathogenesis and clinical course of nephrotic syndrome in children. Thirty-four children (21 males and 13 females, mean age 3.7+/-1.6 years) with steroid-sensitive nephrotic syndrome and 20 children with steroid-resistant nephrotic syndrome (12 males and 8 females, mean age 10.9+/-3.8 years; of the twenty, four had primary SRNS (FSGS) and the others had secondary SRNS) were included the study. Mean urine levels of GAG relative to creatinine (U(GAG)/U(Cr)) in patients with SRNS (n=20, 113.01+/-78.46 mg g(-1) Cr) and in patients experiencing the nephrotic period of steroid-sensitive nephrotic syndrome (n=34, 132.15+/-101.55 mg g(-1) Cr) were both significantly higher than mean U(GAG)/U(Cr) for control subjects (n=30, 51.83+/-47.66 mg g(-1) Cr) (P<0.01 for both). Patients excreted significantly more GAG during the nephrotic period of steroid-sensitive nephrotic syndrome than during remission (132.15+/-101.55 vs 39.11+/-42.73 mg g(-1) Cr, respectively; P<0.01). There was, however, no significant difference between U(GAG)/U(Cr) for patients with steroid-resistant nephrotic syndrome and U(GAG)/U(Cr) in the nephrotic period of steroid-sensitive nephrotic syndrome. Urine GAG excretion correlated significantly with the severity of proteinuria. The results suggest that GAG play a significant role in the pathogenesis of nephrotic syndrome but that GAG excretion is not a marker for response to steroid treatment in pediatric patients with this condition.

Enzymuria as an index of renal damage in canine leishmaniasis

Urinary enzyme activities of alanine aminopeptidase, gamma-glutamyl transpeptidase, alkaline phosphatase, N-acetyl-beta-D-glucosaminidase and beta-glucuronidase were determined in 15 dogs with leishmaniasis and in a group of eight normal dogs. Serum creatinine and blood urea nitrogen concentrations were also measured and renal histology was examined. All the affected dogs had renal lesions. However, no significant differences in blood urea nitrogen and creatinine concentrations were found between the control group and the affected group. The urinary enzyme activities of gamma-glutamyl transpeptidase (P < 0.01), N-acetyl-beta-D-glucosaminidase (P < 0.01) and beta-glucuronidase (P < 0.05) were significantly higher in the affected dogs. Urinary enzymes therefore seem to be a more sensitive and reliable test for assessing early renal damage in canine leishmaniasis than serum creatinine or blood urea nitrogen concentrations.

Effects of parathyroid hormone on urinary excretion of N-acetyl-beta-D-glucosaminidase in idiopathic hypoparathyroidism and pseudohypoparathyroidism

N-acetyl-beta-D-glucosaminidase (NAG) is a lysosomal enzyme predominantly located in renal proximal tubules. In idiopathic hypoparathyroidism (IHP), 100 Units of human PTH (1-34) increased urinary excretion of NAG from 0.029 +/- 0.027 to 0.173 +/- 0.035 U/lGF (p less than 0.05) in two patients before treatment and from 0.025 +/- 0.004 to 0.189 +/- 0.092U/lGF (p less than 0.02) in four patients during treatment with active vitamin D3 (1,25(OH)2D3 or 1 alpha OHD3). In pseudohypoparathyroidism (PHP), PTH did not significantly increase the urinary excretion of NAG in one patient with before treatment (0.048 to 0.025 U/lGF) and four patients during treatment with active vitamin D3 (0.018 +/- 0.008 to 0.036 +/- 0.015 U/lGF). Increase in urinary excretion of NAG after injection of PTH may be a new indicator of renal effect of PTH.

Efficacy of captopril in hypertensive diabetic patients

Twenty hypertensive diabetic patients (10 with type I and 10 with type II) were treated with captopril, 50 mg twice a day, for three months. The drug was effective as monotherapy in 16 patients. An additional nine months of follow-up was obtained in 12 of these patients (four with type I and eight with type II) who did not need the addition of diuretics to achieve normal blood pressure. For these patients with long-term treatment, since there was no substantial difference between those with type I and those with type II, the data were pooled. Mean arterial pressure significantly decreased shortly after treatment was begun and the reduction was maintained. No significant change was induced by captopril in urine volume, osmolar clearance, and serum and urinary values of sodium, chloride, calcium, and magnesium, whereas significant reduction was found in fractional excretion of potassium and phosphate. The baseline levels of proteinuria were only slightly elevated, yet they fell in all patients during treatment. All patients maintained satisfactory control of carbohydrate metabolism, and none of them required substantial changes in hypoglycemic treatment. The administration of captopril as monotherapy appears to be an effective and safe way of lowering blood pressure in diabetic hypertensive patients, even in the long term, without effects on renal function and in carbohydrate metabolism.