Management of glomerular proteinuria: a commentary

It is widely accepted that proteinuria reduction is an appropriate therapeutic goal in chronic proteinuric kidney disease. Based on large randomized controlled clinical trials (RCT), ACE inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy have emerged as the most important antiproteinuric and renal protective interventions. However, there are numerous other interventions that have been shown to be antiproteinuric and, therefore, likely to be renoprotective. Unfortunately testing each of these antiproteinuric therapies in RCT is not feasible. The nephrologist has two choices: restrict antiproteinuric therapies to those shown to be effective in RCT or expand the use of antiproteinuric therapies to include those that, although unproven, are plausibly effective and prudent to use. The goal of this work is to provide the documentation needed for the nephrologist to choose between these strategies. This work describes 25 separate interventions that are either antiproteinuric or may block injurious mechanisms of proteinuria. Each intervention is assigned a level of recommendation (Level 1 is the highest; Level 3 is the lowest) according to the strength of the evidence supporting its antiproteinuric and renoprotective efficacy. Pathophysiologic mechanisms possibly involved are also discussed. The number of interventions at each level of recommendation are: Level 1, n = 7; Level 2, n = 9; Level 3, n = 9. Our experience indicates that we can achieve in most patients the majority of Level 1 and many of the Level 2 and 3 recommendations. We suggest that, until better information becomes available, a broad-based, multiple-risk factor intervention to reduce proteinuria can be justified in those with progressive nephropathies. This work is intended primarily for clinical nephrologists; therefore, each antiproteinuria intervention is described in practical detail.     

Mechanisms of proteinuria in diabetic nephropathy: a study of glomerular barrier function

The fractional clearance of neutral dextrans (theta D) with Einstein-Stokes radii between 30 and 64 A was determined in normal subjects (controls, N = 15) and in diabetic patients with heavy proteinuria (advanced nephropathy, N = 16) or trace proteinuria (early nephropathy, N = 8). When plotted on log normal probability coordinates, the correlation between theta D and radius in controls and in early diabetic nephropathy was linear, suggesting that glomerular pores form one population with a normal distribution. In advanced diabetic nephropathy, however, theta D for large molecules (radius greater than 46 A) was elevated and departed from linearity suggesting a bimodal pore size distribution within the glomerular membrane. A mathematical model was devised, which revealed the mean fraction of glomerular filtrate permeating the upper pore mode to be 0.009 +/- 0.002, and the pores to be totally nondiscriminatory toward molecules with radii up to 64 A. We conclude that the development of large pores (or defects) within the glomerular membrane in advanced diabetic nephropathy permits the unrestricted passage of large plasma proteins into the urine.     

The effect of captopril on proteinuria in glomerular diseases

We evaluated the efficacy of an ACE inhibitor captopril (CAP) for the reduction of proteinuria in glomerular diseases, and tried to find the conditions in which urinary protein excretion was significantly decreased by this drug. Renin provocation test by CAP (C-test) was performed, and the result was compared to the effect on proteinuria. In 33 patients with proteinuria, ranging from 1.1 to 14.1 g/day, CAP was administered. Urinary protein excretion was reduced from 3.6 +/- 0.6 to 2.8 +/- 0.4 g/day (mean +/- SEM, p less than 0.01) after 2 weeks. The decrease in urinary protein was significant when renal function was moderately impaired (30 less than or equal to Ccr less than 60 ml/min) or patients were on a salt diet less than 7 g of NaCl daily. Reduction of urinary protein excretion by 2-week treatment of CAP was correlated with the result of C-test (r = 0.874, p less than 0.025). The long-term follow up for more than 6 months also suggested that CAP delayed the deterioration of renal function. Thus, CAP was proved effective in treating proteinuria, and C-test might give us an information of its proteinuria-suppressing effect in an individual case. But its efficacy was observed only in patients with moderately-reduced renal function or on low-salt diet. Therefore, we should select the cases carefully to expect the effect of CAP for the reduction of proteinuria.     

Familial glomerular disease with asymptomatic proteinuria and nephrotic syndrome: a new clinical entity.

Seventy-three members of a 100-member kindred with asymptomatic proteinuria, nephrotic syndrome, and progressive renal failure were studied. Of those studied, 11 members had progressed to end-stage renal disease and seven had significant proteinuria (greater than 1 g/24 hours) with normal renal function. The genetic mode of inheritance was autosomal dominant with variable penetrance and expressivity. Histopathologic changes were variable but included focal segmental glomerulosclerosis and diffuse glomerulosclerosis. Renal failure usually occurred in the fifth decade of life. The most consistent clinical finding was proteinuria without microscopic hematuria or other significant urinary sediment elements. This disease differed from Alport's hereditary nephritis and congenital nephrotic syndrome in age of onset, urinary findings, and associated conditions, that is, nerve deafness. The hereditary proteinuria and nephrotic syndrome described in this kindred represents another facet in the spectrum of hereditary renal disease.     

Studies of enzymuria and proteinuria: Report 2; Relationship between glomerular filtration rate and urinary enzymuria and proteinuria

Urinary splitting enzymes and proteins including N-acetyl-b-D-glucosanimidase (NAG), beta 2 microglobulin (beta 2MG), and alpha 1 microglobulin: (alpha 1MG), which are established to be useful in the evaluation of renal dysfunction, especially renal tubular impairment, were measured to determine the extent of renal tubular impairment in relation to the degree of glomerular dysfunction in patients with renal deterioration. In healthy volunteers, urinary NAG, alpha 1MG and beta 2MG levels were 3.5 +/- 1.4 (mean +/- SD) U/g creatinine, 2.5 +/- 2.0 mg/l and 88 +/- 75 micrograms/l, respectively. While serum beta 2MG level (SBMG; microgram/ml) was between 2.0 and 2.9, among the patients with renal dysfunction, NAG, alpha 1MG and BMG levels showed 8.6 +/- 5.5, 9.8 +/- 5.8 and 785 +/- 1,264, respectively, and further elevated to 10.1 +/- 5.0, 16.5 +/- 0.7 and 525 +/- 440, respectively with a SBMG level over 3.0. Thus glomerular function was deteriorated, urinary alpha 1MG level elevated to significantly higher with a parallel to renal dysfunction. In patients with more severe renal dysfunction, the corresponding urinary NAG and alpha 1MG levels became significantly higher. However, urinary beta 2MG level was significantly higher in patients with moderate renal dysfunction compared to healthy volunteers only when SBMG level was more than 2.0. Therefore, it was more valuable to measure urinary alpha 1MG with NAG or beta 2MG at SBMG level of less than 1.9 and to determine urinary NAG and alpha 1MG at greater than 2.0. These results indicated that the measurement of the levels of urinary splitting enzymes and proteins is valuable in the evaluation of proximal tubular impairment, even when the degree of glomerular impairment is minimal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diclofenac, a nonsteroidal anti-inflammatory drug, decreases proteinuria in some glomerular diseases: a controlled study

Treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) was first used in glomerulonephritis (GN) in 1966 but its efficiency is still debated. We studied the antiproteinuric effect of such a treatment in a double-blind study. 29 GN patients with normal renal function (17 membranoproliferative GN, 12 IgA GN) were randomly assigned to receive 100 mg/day of diclofenac or placebo for at least 2 months. There was a significant antiproteinuric effect of diclofenac versus placebo with a fall of 70% in the diclofenac group versus 6% in the placebo group (p less than 0.001 with the Mann-Whitney test). The median was 3 mg/min at onset and 2.45 mg/min after 2 months treatment with the placebo. In the diclofenac group, it was 2.2 and 0.95 mg/min, respectively (p less than 0.01). Diclofenac did not significantly increase creatinine levels. Gastric irritation was noted only once. This study establishes the short-term antiproteinuric action of diclofenac. Whether this action affects the final outcome is not yet determined.     

Administration of dexamethasone induces proteinuria of glomerular origin in mice

The administration of glucocorticoids has been reported to exacerbate proteinuria in a few patients with glomerulonephritis. This effect has not been well recognized, and the pathogenetic mechanism responsible for this phenomenon remains to be clarified. In this study, we observed that a high daily oral dose (0.5 mg/kg body weight) of dexamethasone was capable of inducing overt proteinuria in mice, beginning on day 5 and persisting for a 19-day duration. One fourth of mice also intermittently presented with slight hematuria beginning on day 12. Renal lesions in the dexamethasone-treated mice, which were killed on day 23, were characterized by mild mesangial expansion, segmental or global hyalinosis/sclerosis in deep cortical glomeruli, and focal tubular changes. No glomerular inflammatory cell infiltration or proliferative lesion was noted in any of the mice. Ultrastructural features of glomeruli included mesangial widening characterized by either an increase of mesangial matrix, dilated mesangial channels filled with slightly electron-dense material or mesangial lysis-like appearance showing intracytoplasmic microcysts filled with electron-lucent material, and evidence to support injury of endothelial cells, erythrocytes, and podocytes. An immunofluorescence study revealed enhanced glomerular deposition of IgG, IgA, IgM, and fibrinogen (P < 0.001, compared with normal control mice), but no glomerular C3 deposition was identified in any of the dexamethasone-treated mice. Charge analysis showed no impairment in anionic property of glomerular tufts in the dexamethasone-treated mice. In addition, the dexamethasone-induced proteinuria was greatly attenuated by treatment with a low molecular weight heparin, although it was not reduced by an angiotensin-converting enzyme inhibitor. Data from these experiments suggest that a large dose of glucocorticoids is potentially nephrotoxic. Alteration of a size-dependent permeability may predominantly contribute to the dexamethasone-induced proteinuria. However, the effect of glomerular hyperfiltration may be only partially involved in the pathogenesis of this dexamethasone-induced glomerulopathy in mice.     

贝尼地平和缬沙坦对慢性肾小球疾病GFR 及蛋白尿的作用比较

本研究对236例慢性肾小球肾病患者分别采用钙通道阻滞剂(CCB)贝尼地平和血管紧张素Ⅱ受体拮抗剂(ARB)缬沙坦进行治疗,观察它们在保护肾功能方面的差异.     

Urinary podocyte loss is a more specific marker of ongoing glomerular damage than proteinuria

Podocyte loss contributes to the development of glomerulosclerosis. Although podocyte detachment has been recognized as a new mechanism of podocyte loss in glomerular diseases, its time course and relationship to disease activity are not known. Urinary excretion of viable podocytes was quantified in two models of transient glomerular injury, i.e., rats with puromycin aminonucleoside-induced nephrosis (PAN) and mesangioproliferative nephropathy (anti-Thy 1.1 nephritis model), as well as in a model of continuous glomerular injury, i.e., hypertensive nephropathy (5/6-nephrectomy model), and in aging rats. The number of glomerular Wilm's tumor (WT)-1-positive podocytes and the glomerular expression of cell-cycle proteins in vivo were assessed. Urinary podocyte loss occurred in both primary (PAN) and secondary (anti-Thy 1.1 nephritis) in parallel to the onset of proteinuria. However, subsequently proteinuria persisted despite remission of podocyturia. In continuous glomerular injury, i.e., after 5/6-nephrectomy, podocyturia paralleled the course of proteinuria and of systemic hypertension, whereas no podocyturia became detectable during normal aging (up to 12 mo). Despite podocyte detachment of varying degrees, no decrease in glomerular podocyte counts (i.e., WT-1 positive nuclei) was noted in either disease model. Podocyturia in the PAN and anti-Thy 1.1 nephritis model was preceded by entry of glomerular podocytes into the cell cycle, i.e., cyclin D1, cdc2, and/or proliferating cell nuclear antigen (PCNA) expression. Podocyturia is a widespread phenomenon in glomerular disease and not simply a reflection of proteinuria because it is limited to phases of ongoing glomerular injury. The data suggest that podocyturia may become a more sensitive means to assess the activity of glomerular damage than proteinuria.     

Proximal tubular epithelial hyperplasia in patients with chronic glomerular proteinuria

BACKGROUND: Proteinuria is known to affect the proximal tubular epithelial structure and function. The present study tested the hypothesis that chronic proteinuria leads to hyperplasia of proximal tubular epithelium. METHODS: This hypothesis was tested by morphometric analysis of the renal biopsy specimens in two groups of patients. Group A (N = 15) was composed of patients with chronic glomerular proteinuria who, for clinical indications, underwent renal biopsy of their native kidneys on two separate occasions. The proteinuria was sustained during the first and second renal biopsies in all but two of the patients with minimal change nephrotic syndrome who experienced transient remission. Group B (N = 10) was composed of patients with little or no proteinuria who underwent renal biopsy because of unexplained hematuria and whose renal biopsy showed only thin glomerular basement membrane (GBM) disease. RESULTS: In Group A, the mean number of epithelial cell nuclei per proximal tubule cross-section increased significantly from the first to the second renal biopsy (11.0 +/- 2.7 vs. 13.0 +/- 2.2, P = 0.005, paired t-test). Also, those with severe proteinuria showed proximal tubules with reactive epithelium (large pale nuclei with a high nucleus to cytoplasm ratio) and marked hyperplasia (double and triple layers of epithelium). Such changes were not seen in group B renal biopsies. Compared with group A biopsies, group B biopsies showed a lower mean value for proximal tubular epithelial cell nuclei per tubular cross-section (P = 0.056) and a higher mean proximal tubular volume (P = 0.049). As a consequence, the mean number of nuclei per relative tubular volume was significantly greater in group A compared with group B (0.55 +/- 0.14 vs. 0.40 +/- 0.06, P = 0.003, by Wilcoxon rank sum). CONCLUSIONS: Chronic heavy proteinuria is associated with hyperplasia of proximal tubular epithelium and contraction of proximal tubular volume. These events may impair glomerular filtration and represent another mechanism of progression of renal disease.