Urinary glycosaminoglycan composition in chronic glomerulonephritis.

BACKGROUND: Glycosaminoglycans (GAG) play an important role in regulating glomerular permeability, and a reduction in their plasmatic concentration or urinary loss has been implicated in the pathogenesis of diseases associated with increased albumin permeability. The purpose of this study was to evaluate GAG excretion in renal pathology by analyzing the composition of urinary GAG in antibody mediated glomerular injury, such as mesangial glomerulonephritis (IgAGN) and primitive membranous glomerulonephritis (MGN), to verify the effects of glomerular capillary wall lesion with and without mesangial cell injury. METHODS: Urinary GAG excretion was analyzed in 20 patients with IgAGN, 18 patients with MGN, and in 18 healthy subjects (controls). GAG were isolated from 24-hr urine using ion-exchange chromatography on DEAE-Sephacel, and the results are expressed as mg hexuronate/g creatinine (Cr). GAG composition was determined by cellulose acetate electrophoresis and expressed as relative percentages by densitometric scanning of Alcian Blue stained strips. RESULTS: We found total GAG levels significantly higher in the urine of patients with MGN in comparison with controls and patients with IgAGN. The electrophoretic pattern analysis demonstrated low sulfated chondroitin sulfate proteoglycan (LSC-PG) in all patients compared to 44% in controls (8/18), but also low sulfated chondroitin sulfate (LSC) in 18.4% of patients (7/38) and slow migrating LSC (SM-LSC) in 8% of patients (3/38), only in the MGN group. Moreover, in patients with MGN, the LSC-PG relative content was significantly higher when compared to that observed in controls. Finally, in IgAGN and MGN patients, a significant reduction in chondroitin sulfate (CS) relative content was observed. CONCLUSIONS: It seems likely that an increase in total GAG levels takes place when a reduction in renal function occurs, but the alteration of CS and herapan sulfate (HS) relative contents, and the presence of LSC-PG and free LSC also in the urine of IgAGN patients, allows us to suggest that the GAG distribution pattern becomes abnormal before an increase in total urine GAG excretion. In addition, the quali-quantitative determination of urinary GAG and GAGprotein complex could constitute an additional non-invasive marker to appraise the metabolism of renal connective tissue in some renal diseases.

Urinary glycosaminoglycan and proteoglycan excretion in normoalbuminuric patients with type 1 diabetes mellitus.

BACKGROUND: Diabetic nephropathy may be related to an abnormal metabolism of glycosaminoglycans (GAG) in the glomerular basement membrane (GBM). The first manifestation of nephropathy is microalbuminuria, whose appearance indicates a loss of GBM selectivity. The present study evaluated whether GAG excretion becomes abnormal in parallel with microalbuminuria, and whether such abnormalities are also present in normoalbuminuric diabetic patients. METHODS: We measured urinary GAG excretion in 60 patients with type 1 (insulin-dependent) diabetes mellitus and in 22 healthy subjects. GAG were isolated from 24-h urine using ion-exchange chromatography on DEAE Sephacel. GAG composition was determined by cellulose acetate electrophoresis and expressed as percentages by densitometric scanning of Alcian Blue stained strips. RESULTS: On subgrouping for albuminuric status and glyco-metabolic control, we found high urinary GAG concentrations in all except the normoalbuminuric patients with good glyco-metabolic control. The urinary GAG electrophoretic pattern showed alterations in chondroitin sulphate (CS) and heparan sulphate (HS) relative contents. A higher frequency of low sulphated chondroitin sulphate-proteoglycan (LSC-PG) was observed in all patients, including those with normoalbuminuria and good glyco-metabolic control. CONCLUSIONS: This urinary pattern may be indicative of an abnormal GBM metabolism. Since GAG play an important role in GBM permeability, these anomalies might consequently represent a first step towards selective changes of GBM in type 1 diabetes mellitus.

Quali-quantitative analysis of urinary glycosaminoglycans for monitoring glomerular inflammatory activity.

OBJECTIVE: A 2-year follow-up study was carried out in patients with IgA nephropathy (IgAN) in order to verify the possible use of quali-quantitative analysis of urinary glycosaminoglycans (GAGs) as a prognostic index of disease and for drug treatment monitoring. MATERIAL AND METHODS: Ten patients with IgAN were evaluated at four time points: baseline, and 6, 9 and 24 months later. GAGs were isolated from 24-h urine using ion-exchange chromatography on diethylaminoethyl-Sephacel, and concentrations were expressed as milligrams of hexuronate per gram of creatinine. GAG composition was determined by cellulose acetate electrophoresis and expressed as relative percentages by means of densitometric scanning of Alcian Blue-stained strips. RESULTS: The relative content of total low-sulphated chondroitin sulphate species decreased significantly during the study period compared to baseline, whereas the relative percentages of heparan sulphate and chondroitin sulphate increased significantly. Moreover, a significant correlation was noted between the relative contents of urinary GAGs, renal function and inflammation indexes. CONCLUSIONS: It is likely that the excretion of various types of GAGs may be related to different glomerular pathophysiological conditions. Therefore, the determination of urinary GAG composition may represent a reliable indicator of disease activity.

A longitudinal evaluation of urinary glycosaminoglycan excretion in normoalbuminuric type 1 diabetic patients.

BACKGROUND: Previously, we found high urinary glycosaminoglycan (GAG) concentration, together with an altered electrophoretic pattern, in normoalbuminuric type 1 diabetic subjects with hemoglobin A(1c) (HbA(1c)) > or =8.0%. The purpose of this study was long-term evaluation of GAG excretion variations in these patients compared to those with HbA(1c) < 8.0% at baseline who maintained better metabolic control over time. METHODS: We enrolled 26 normotensive, normoalbuminuric type 1 diabetic patients and divided them into two groups according to mean HbA(1c) levels during the follow-up period. GAGs were isolated from 24-h urine samples on two separate occasions, at baseline and after a mean (+/-SD) follow-up of 6.8+/-1.1 years. RESULTS: All patients remained normoalbuminuric at follow-up, and had normal urinary alpha(1)-microglobulin levels. In patients with HbA(1c) <8.0%, total GAG levels and low sulfated chondroitin sulfate-proteoglycan/chondroitin sulfate ratio were almost unchanged during the follow-up period. In contrast, these increased in patients with HbA(1c) > or =8.0% and were significantly related to both HbA(1c) levels and the duration of poor glycemic control. CONCLUSIONS: Our results show a strong influence of hyperglycemic environment on GAG metabolism in diabetes and indicate that the distribution pattern of urinary GAGs, besides their total concentration, may be predictive of altered GAG metabolism in type 1 diabetes.

Urinary transforming growth factor-beta 1 in various types of nephropathy.

Transforming growth factor-beta1 (TGF-beta1) is a potent multifunctional polypeptide that is involved in normal renal function and in the development of glomerular sclerosis. It is also an important mediator of the immune and anti-inflammatory responses. The purpose of this study was to examine whether the measurement of urinary TGF-beta1 excretion in patients with different types of renal diseases and in newly diagnosed type 1 diabetes mellitus represents a non-invasive tool to evaluate disease activity and to monitor response to therapy. We studied the urinary excretion of TGF-beta1 in 57 nephropathic patients divided in different groups according to the underlying disease: 15 had mesangial glomerulonephritis (IgAGN), 9 membranous glomerulonephritis (MGN), 7 rapidly progressive glomerulonephritis (RPGN), 8 systemic lupus erythematosus (SLE), 9 interstitial nephritis (IN), 9 chronic renal failure (CRF). TGF-beta1 was also measured in 38 patients with type 1 (insulin-dependent) diabetes mellitus (12 with newly diagnosed diabetes, 26 long-standing diabetes) and 31 healthy controls. Total urinary TGF-beta1 concentration was assayed by enzyme-linked immunoassay (ELISA), and expressed as a ratio to urinary creatinine concentration. The urinary TGF-beta1 levels were compared with the findings of biopsy and clinical parameters. Urinary TGF-beta1 excretion was significantly increased in all groups except MGN, IN and CRF. In non-diabetic patients, urinary TGF-beta1 levels correlated with crescent formation, floccular adhesion and mesangial proliferation, but not with the degree of tubulo-interstitial fibrosis. Urinary TGF-beta1 levels did not correlate with indices of renal function (serum creatinine, glomerular filtration rate (GFR), albumin excretion rate [AER]). Among diabetic patients, HbA(1C) significantly correlated with TGF-beta1 urinary excretion. Urinary TGF-beta1 levels may represent a valid indicator of acute glomerular flogosis associated with mesangial proliferation in glomerulonephrities. In newly diagnosed diabetic patients, hyperglycaemia seems to represent the principal factor leading to TGF-beta1 overproduction. Follow-up studies of urinary TGF-beta1 levels measured during optimal glycaemic control are necessary to clarify the relationship between hyperglycaemia and TGF-beta1 excretion.