Differentiation of glomerular, tubular, and normal proteinuria: determinations of urinary excretion of beta-2-macroglobulin, albumin, and total protein

A low molecular weight beta(2)-globulin (beta(2)-microglobulin), albumin, and total protein were measured in concentrated 24-hr urine specimens from 20 healthy subjects and 30 patients with clinical proteinuria of glomerular or tubular type. Classification of proteinuria was made on the basis of clinical diagnosis and size distribution of urinary proteins after gel chromatography. The molecular radii (Stokes' radii) of beta(2)-microglobulin and albumin, estimated by gel chromatography, were 15 A and 35 A. The average 24-hr urinary excretion in healthy subjects was 0.12 mg for beta(2)-microglobulin, 10 mg for albumin, and 80 mg for total protein. The patients with renal glomerular disorders had normal or only somewhat increased excretion of beta(2)-microglobulin, despite considerably increased excretion of albumin and total protein. Most of the patients with tubular dysfunction excreted large amounts of beta(2)-microglobulin, although they excreted normal or only slightly increased amounts of albumin and only moderately increased quantities of total protein. Consequently, the ratio or urinary albumin/urinary beta(2)-microglobulin was high in glomerular proteinuria (1100: 14,200), intermediate in normal proteinuria (33: 163), and low in tubular proteinuria (1.0: 13.3). Determinations of urinary clearances of beta(2)-microglobulin and albumin in four healthy subjects and 11 patients indicated that increased excretions of the two proteins were associated with increased clearances. The results suggest that quantitative determinations of urinary beta(2)-microglobulin and urinary albumin may be useful for detecting disorders of the renal handling of plasma proteins. The findings also seem to suggest a selective tubular reabsorption of the two proteins. Estimates on sera revealed a close correlation between serum levels of beta(2)-microglobulin and creatinine and also a greatly raised serum concentration of beta(2)-microglobulin after bilateral nephrectomy.

Podocyte-secreted angiopoietin-like-4 mediates proteinuria in glucocorticoid-sensitive nephrotic syndrome

The main manifestations of nephrotic syndrome include proteinuria, hypoalbuminemia, edema, hyperlipidemia and lipiduria. Common causes of nephrotic syndrome are diabetic nephropathy, minimal change disease (MCD), focal and segmental glomerulosclerosis (FSGS) and membranous nephropathy. Among the primary glomerular diseases, MCD is usually sensitive to glucocorticoid treatment, whereas the other diseases show variable responses. Despite the identification of key structural proteins in the glomerular capillary loop which may contribute to defects in ultrafiltration, many of the disease mechanisms of nephrotic syndrome remain unresolved. In this study, we show that the glomerular expression of angiopoietin-like-4 (Angptl4), a secreted glycoprotein, is glucocorticoid sensitive and is highly upregulated in the serum and in podocytes in experimental models of MCD and in the human disease. Podocyte-specific transgenic overexpression of Angptl4 (NPHS2-Angptl4) in rats induced nephrotic-range, and selective, proteinuria (over 500-fold increase in albuminuria), loss of glomerular basement membrane (GBM) charge and foot process effacement, whereas transgenic expression specifically in the adipose tissue (aP2-Angptl4) resulted in increased circulating Angptl4, but no proteinuria. Angptl4(-/-) mice that were injected with lipopolysaccharide (LPS) or nephritogenic antisera developed markedly less proteinuria than did control mice. Angptl4 secreted from podocytes in some forms of nephrotic syndrome lacks normal sialylation. When we fed the sialic acid precursor N-acetyl-D-mannosamine (ManNAc) to NPHS2-Angptl4 transgenic rats it increased the sialylation of Angptl4 and decreased albuminuria by more than 40%. These results suggest that podocyte-secreted Angptl4 has a key role in nephrotic syndrome.

Acquired antithrombin III deficiency and thrombosis in the nephrotic syndrome

Antithrombin III levels were studied in relation to the occurrence of thromboembolism in 48 patients with various degrees of proteinuria. Nine of these patients had clinical signs of thrombosis, including four with renal vein thrombosis. In eight of these nine patients, antithrombin III concentrations were below 70 per cent. There was a significant negative correlation between the antithrombin III concentration and the urinary protein excreation (P less than 0.001). Antithrombin III was found in the urine of 32 of 42 patients. There was a significant correlation between the renal clearance and the degree of antithrombin III serum deficiency (P less that 0.001). The clearance and serum level of albumin closely paralleled these changes. We conclude that thrombosis in patients with severe proteinuria is associated with a deficiency of antithrombin III due to urinary excretion of this protein.

Long-term outcome of primary nephrotic syndrome

One hundred and fourteen children with primary nephrotic syndrome were followed up prospectively for periods of between 5 and 14 years. Urine samples from 94 of them became protein-free during the initial 8-week course of prednisone, and the outcome for these children was good: 74 of them have been free of symptoms for at least 3 years, 18 have had relapses during the last 3 years, and only one child still has proteinuria. All these children have normal renal function and blood pressure. One child died accidentally. Twenty children did not respond to the initial prednisone treatment. Thirteen of them had remissions later, of whom 2 have had relapses during the last 3 years. Seven were totally resistant to prednisone 4 of whom died in renal failure, the remaining 3 have persistent proteinuria with normal levels of creatinine; one has high blood pressure too. Remission during the initial treatment indicated a good prognosis, but two-thirds of the initial non-responders also fared well.

Additive antiproteinuric effect of ACE inhibition and a low-protein diet in human renal disease

Both ACEi and a low-protein diet (LPD) are reported to reduce urinary protein excretion in patients with stable non-diabetic renal disease. To test whether the combination of both may have an additive antiproteinuric effect, we studied the effects of single treatment with ACEi (10 mg enalapril o.d.), LPD (target, 50% reduction in protein intake), and the combination of both in 14 of such patients with stable proteinuria exceeding 3 g per day. Baseline measurements were performed while patients were on a normal protein diet (NPD). In group A (n = 7), first the effects of a LPD were investigated, whereafter the effects of addition of ACEi to LPD were studied. In group B (n = 7), first the effects of ACEi were investigated, whereafter the effects of addition of a LPD to ACEi were studied. Each treatment period lasted 2 months. LPD decreased proteinuria with 17% in patients without ACEi treatment (group A), and similarly with 19% in patients with ACEi treatment (group B). The antiproteinuric response obtained with the LPD in individual patients ranged from -63% to +1%. This variation is at least partly explained by interindividual differences in diet compliance, since the antiproteinuric effect of the LPD was found to correlate with the achieved reduction in protein intake (r = 0.58, P < 0.05). ACEi lowered proteinuria with 32% during the NPD (group B), and similarly with 43% during the LPD (group A).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of drugs in patients with the nephrotic syndrome

Since the binding of drugs to plasma proteins can significantly after the intensity of pharmacological and toxicological effects of drugs, we studied the pharmacokinetics of three drugs in patients with hypoalbuminemia secondary to the nephrotic syndrome, but with relatively normal renal function. No significant differences were seen in the pharmacokinetic parameters observed for antipyrine, a drug which is less than 10% bound to plasms proteins. The percentage of unbound diphenylhydantoin, a highly plasms protein-bound drug, was found in patients with the nephrotic syndrome to be twice that of healthy individuals (19,2 vs. 10.1%, P smaller than 0.001). However, there was also a lower steady-state plasma concentration of diphenylhydantoin (2.9 plus or minus 0.6 vs. 6.8 plus or minus 0.6 mug/ml, P smaller than 0.001) secondary to an increase in the plasms clearance (0.048 plus or minus 0.019 vs. 0.022 plus or minus 0.006 liter/kg.h, P smaller than 0.001) in the nephrotic patients. The net effect is no difference in the absolute concentration of unbound diphenylhydantoin in healthy individuals (0.69 plus or minus 0.05 mug/ml) and patients with the nephrotic syndrome (0.59 plus or minus 0.06 mug/ml). Qualitatively, similar differences were observed with clofibrate. The dose of these drugs need not be routinely reduced in patients with the nephrotic syndrome as long as they have reasonably normal renal function (creatinine clearance greater than 50 ml/min). With all highly bound acidic drugs, knowledge of the concentration of unbound drug is essential to the proper interpretation of total blood levels and subsequent treatment of the patient.

Apical cell membranes are shed into urine from injured podocytes: a novel phenomenon of podocyte injury

Previously it was shown that urine from patients with nephritis contains podocytes and their fragments (podocalyxin [PCX]-positive granular structures [PPGS]), reflecting the degree of podocyte injury. The present study was designed to trace PPGS to their origin. Urine samples and renal biopsy specimens from 53 children with nephrotic syndrome and nephritis were examined immunohistochemically. Immunofluorescence studies of kidney sections using an anti-PCX antibody demonstrated that PPGS originated from the glomerulus and flowed into the tubular lumen. Electron microscopic examination revealed that PPGS originated from microvillous or vesicle-like structures on injured podocytes in the glomerulus. For examining the origin of the PPGS, apical, slit-diaphragmatic, and basal portions of the podocytes were specifically stained, revealing that PPGS are composed primarily of apical podocyte membranes. Several newly developed antibodies that are reactive with various segments of the PCX molecule were used to analyze more detailed membrane structures, and it was found that PPGS contained intact PCX molecules, indicating that cell membrane structures are excreted in urine. The quantification of PCX content and podocyte numbers revealed that urinary sediment PCX (u-sed-PCX) content per urinary podocyte was much higher than PCX content per podocyte from isolated glomeruli of normal controls, suggesting that u-sed-PCX are derived from sources other than just the cell debris of detached podocytes. Analysis of the correlation between u-sed-PCX and renal histology revealed that the presence of PPGS reflects acute glomerular injury. In conclusion, podocyte apical cell membranes are shed into the urine from injured podocytes, indicating a previously unrecognized manifestation of podocyte injury.

Urinary podocytes in primary focal segmental glomerulosclerosis

BACKGROUND/AIM

Focal segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome. Although the pathogenesis is not known, recent studies suggest that FSGS may be a podocyte disease. The aim of this study was to look for podocyte injury in this disease, using measurements of urinary podocytes.

METHODS

We examined the first morning urine of the day collected from 71 patients (45 men and 26 women, median age and range 11.2 and 3-29 years) diagnosed as having nephrotic syndrome. Freshly voided urine samples were examined by immunofluorescence labeling using monoclonal antibodies against human podocalyxin. Renal histological examinations were performed in 58 of the 71 patients: 28 had minimal-change disease, 20 had FSGS, and 10 had membranous nephropathy.

RESULTS

Median and range of urinary podocytes measured were 0.2 and 0-40.8 cells/ml for 71 patients with nephrotic syndrome and 0 and 0-0.8 cells/ml for normal healthy control subjects (n = 200). Patients with FSGS had significantly higher levels of urinary podocytes (median and range 1.3 and 0-40.8 cells/ml) than those with minimal-change disease (median and range 0 and 0-6.9 cells/m; p = 0.003) or membranous nephropathy (median and range 0 and 0-1.4 cells/ml; p = 0.02).

CONCLUSIONS

The urinary excretion of podocytes is significantly higher in patients with FSGS as compared with those having membranous nephropathy or minimal-change disease. These findings suggest that podocyte injury and loss in the urine may have an important role in the pathogenesis of FSGS.

Nephrotic-range proteinuria, the major risk factor for early atherosclerosis in juvenile-onset systemic lupus erythematosus

OBJECTIVE

To determine the presence of early carotid atherosclerosis and associated risk factors in patients with juvenile-onset systemic lupus erythematosus (SLE).

METHODS

The carotid intima-media wall thickness (IMT) was measured by B-mode ultrasound in patients with SLE onset before the age of 16 years and in sex- and age-matched healthy control subjects. Risk factors for atherosclerosis were determined at the time of the ultrasound scan and included traditional cardiovascular and SLE-related risk factors.

RESULTS

Twenty-six patients with juvenile-onset SLE and 26 healthy controls were studied. The mean (+/- SD) IMT of the SLE patients was significantly higher than that of the control group (0.57+/-0.05 mm and 0.54+/-0.03 mm, respectively; P = 0.006). The results of IMT measurement were not correlated with the patients' age, disease duration, SLE Disease Activity Index (SLEDAI) score, Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index (DI) score, laboratory indicators of lupus activity, or cumulative prednisone dose. Patients with nephrotic-range (NR) proteinuria (> or = 3.5 gm/24 hours; n = 6) had a significantly higher IMT than did those without (n = 20) (P = 0.02). Patients with NR proteinuria also had significantly higher SLEDAI scores, SLICC/ACR DI scores, and systolic and diastolic blood pressures, and significantly higher levels of total cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, and fibrinogen. No difference in any of the above variables, including the IMT, was observed when SLE patients without NR proteinuria were compared with healthy controls.

CONCLUSION

These patients with juvenile-onset SLE had ultrasonographic evidence of premature atherosclerosis. The risk of early atherosclerosis may be higher in patients with NR proteinuria.

Albumin synthesis, albuminuria and hyperlipemia in nephrotic patients

Hyperlipemia is a common manifestation of the nephrotic syndrome. Serum lipid concentrations have been observed by others to be negatively correlated with serum protein concentration. Hyperlipemia has been postulated to result from a coordinate increase in the synthesis of both albumin and lipoproteins, as well as from their decreased catabolism. Simultaneous measurements of serum lipid concentration and the rate of albumin synthesis have not been previously reported. We measured the rate of albumin synthesis, urinary albumin loss, serum albumin, protein, cholesterol and triglyceride concentration in 13 nephrotic patients. Changes in the rate of albumin synthesis and in urinary albumin excretion were induced in eight patients by alteration in dietary protein intake. The resultant changes in serum triglyceride and cholesterol were analyzed by multiple regression analysis. The rate of albumin synthesis measured while patients were eating a low protein diet was 12.61 +/- 1.20 g/1.73 m2/day, well within normal limits, yet both serum triglyceride and cholesterol concentrations were markedly elevated (265 +/- 65 mg/dl and 325 +/- 44 mg/dl, respectively). Albumin synthetic rate increased to 17.60 +/- 1.25 g/1.73 m2/day when dietary protein intake was increased, while serum triglyceride and cholesterol concentrations changed little; triglyceride concentration was 306 +/- 75 mg/dl and cholesterol 376 +/- 55 mg/dl. Serum cholesterol concentration, by multiple regression analysis, was dependent only upon the renal clearance of albumin P less than 0.0001, and changes in serum cholesterol concentration was dependent only upon changes in the renal clearance of albumin, P less than 0.001. Serum cholesterol concentration was completely independent of the rate of albumin synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteinuria, not altered albumin metabolism, affects hyperlipidemia in the nephrotic rat

It has been established previously that nephrotic hyperlipidemia is characterized by both an increase in lipid synthesis and a defect in removal of lipoproteins. The relationship between these defects and altered albumin metabolism is uncertain. One hypothesis is that hepatic lipogenesis increases in parallel with albumin synthesis. To test this hypothesis, albumin synthesis was increased in nephrotic rats fed an 8.5% protein diet (LPN) by increasing dietary protein to 40% (HPN). Proteinuria was modulated in half of the rats fed 40% protein by enalapril (HPE). Albumin synthesis was the same in both HPN and HPE, but proteinuria was reduced in HPE compared to HPN, and so were serum cholesterol and triglycerides (TG). To examine the effect of serum albumin on lipid clearance in the absence of proteinuria, plasma clearance of chylomicrons (CM) and VLDL was measured in Nagase analbuminemic rats (NAR) and found to be no different than in normal SD rats. When proteinuria was induced in NAR and in SD rats, a severe and identical defect in both CM and VLDL clearance was acquired in both groups and blood lipid levels were increased to a similar degree in both groups. Neither hyperlipidemia nor defective removal of lipoproteins from the circulation are linked to albumin synthesis or serum albumin concentration but result, at least in part, from proteinuria. Postheparin lipoprotein lipase (LPL) activity was reduced slightly in nephrotic animals compared to nonnephrotic controls, but the most striking finding was a highly significant decrease in postheraprin LPL activity in normal NAR compared to SD rats (P less than 0.001), suggesting that reduced LPL activity is not responsible for reduced clearance of CM and VLDL in nephrotic rats.

The presence of a natriuretic factor in urine of patients with chronic uremia. The absence of the factor in nephrotic uremic patients

A gel filtration fraction of serum from chronically uremic patients has been shown previously to produce natriuresis in the rat. In the present studies, the same fraction from urine of uremic patients and normal subjects was studied for its natriuretic activity. Urine samples were obtained from 17 chronically uremic patients (mean glomerular filtration rate [GFR], 8.7 ml/min; mean fractional sodium excretion [FE(Na)], 5.7%), and 14 normal subjects. The fraction from the uremic patients produced a significant increase in absolute sodium excretion (U(Na)V) and FE(Na); the fraction from normal subjects had no statistically significant effect on either U(Na)V or FE(Na); and the difference between the response to the uremic vs. normal fractions was highly significant for both parameters of sodium excretion. When a more concentrated urine fraction from uremic patients was administered, a striking natriuresis was observed with values for FE(Na) rising to levels as high as 12%. Studies also were performed on eight patients with far advanced chronic renal insufficiency and the nephrotic syndrome. The serum fraction was studied in each of these patients and the urine fraction in three. For the group, U(Na)V in the assay rats decreased by 0.87 mueq/min and FE(Na) decreased by 1.35% after infusion of the serum fraction. These results differ significantly from those of patients with chronic uremia without the nephrotic syndrome. The data are consistent with the view that the increased activity of the natriuretic factor in the serum of chronically uremic patients is not due to failure of excretion; rather it relates either to an increased rate of production and/or a decreased rate of degradation. The data also show that the inhibitor is detectable when FE(Na) is increased, but not when uremia is associated with a sodium-retaining state.

Role of plasma vasopressin in the impairment of water excretion in nephrotic syndrome

To verify whether or not an increased secretion of ADH may cause the water retention commonly observed in nephrotic syndrome, 16 nephrotic patients and 13 normal control subjects were studied in basal conditions and following a water load or an iso-osmotic blood volume expansion by 20% albumin infusion. In the basal condition there were no differences in plasma ADH, urine output, urinary osmolality (UOsm), and plasma renin activity between nephrotic patients and control subjects; POsm, PNa+, UNaV, and blood volume (BV) instead, were significantly lower in nephrotic patients than in control subjects. Following the water load control subjects reached a minimal UOsm of 82 +/- 12 mOsm/kg at 60 min and excreted completely the ingested water in 150 min; nephrotic patients reached a minimal UOsm of 160 +/- 111 mOsm/kg at 120 min, and the water was eliminated completely in 240 min. Plasma ADH decreased significantly in the first hour following water load only in control subjects. A significant direct correlation was observed between plasma ADH and POsm in control subjects (ADH = -85 + 0.30 POsm, P less than 0.001) but not in nephrotic patients. Plasma ADH was inversely correlated with BV in nephrotic patients (ADH = 15.47 -0.17 BV, P less than 0.001) but not in normal control subjects. In nephrotic patients with reduced BV the expansion of BV with 20% albumin was effective in reducing the plasma levels of ADH and promoting a water diuresis. Our results demonstrate a sustained volume mediated secretion of ADH in the nephrotic syndrome, which is responsible for the impairment in water excretion.

Quantitation of proteinuria with urinary protein/creatinine ratios and random testing with dipsticks in nephrotic children

We examined the relative feasibility of using random urinary dipstick testing and urinary protein/creatinine ratios in the quantitation of proteinuria. Sixty-four children with relapsing nephrotic syndrome, ranging in age from 1 1/2 to 16 years, contributed 145 timed urine collections and 150 random specimens, which were analyzed by urinary protein dipstick, quantitation of protein and creatinine, or both. Total protein excretion was expressed as grams per surface area per day and the urinary protein/creatinine ratio as milligrams of protein per milligram of creatinine. Degrees of proteinuria were designated as physiologic (less than 0.1 gm/m2/day), intermediate (greater than 0.1 and less than 1.0 gm/m2/day), or nephrotic (greater than 1.0 gm/m2/day). The log regression analysis of the 24-hour urinary protein/creatinine ratio (y) and total protein excretion (x) was highly significant (r = 0.97; p less than 0.001). The upper and lower confidence limits of the urinary protein/creatinine ratio (1.0 and 0.1, respectively) closely approximated the designations for nephrotic and physiologic proteinuria, respectively. These values were therefore used to classify degrees of proteinuria by the urine protein/creatinine ratio. The validity of these tests was assessed by sensitivity, specificity, and predictive value, and compared with that of random testing by urinary dipstick. The urinary protein/creatinine ratio offered good reliability as a test for classifying degrees of proteinuria and accurately predicting nephrotic and physiologic proteinuria. The random dipstick testing was reliable only when results were distinctly positive and when sensitivity and specificity were low. The error in the total protein excretion value that was imposed by collection errors with high and low variations in the creatinine value (57% of samples) was largely corrected by normalization of the data by log transformation. When controlled for creatinine excretion, linear regression analysis allowed calculation of total protein excretion (TP) from the urinary protein/creatinine ratio (U P/Cr) by the following equation: TP (gm/m2/day) = 0.63 (U P/Cr) at all levels of proteinuria. The random urinary protein/creatinine ratio appeared to offer the most sensitive test for classification of proteinuria in children with nephrosis, with the advantages of ease and expediency not afforded by the 24-hour urine quantitation.

Nephrotic syndrome associated with acquired immunodeficiency syndrome in children

We report here the cases of 15 children in whom nephrotic syndrome developed, from among 164 children (55% male, 90% black) followed in our acquired immunodeficiency syndrome clinic from 1984 through 1990. Mean age at onset of nephrotic syndrome was 4.9 +/- 2.6 years. Fourteen patients were black and one was Hispanic. Seventy-three percent of our patients with nephrotic syndrome were girls. The mean duration of clinical acquired immunodeficiency syndrome before development of nephrotic syndrome was 1.7 +/- 1.1 years. In eight patients, nephrotic syndrome appeared between 3 and 11 months after intravenous infusions of immune globulin or albumin were administered as part of a research protocol; this incidence (8/47) was higher than the incidence of nephrotic syndrome among those who did not receive intravenous infusions (7/117, p less than 0.05). Tissue for histologic examination was available for 80% of the patients, and histologic examination demonstrated mesangial hypercellularity (5 patients), focal segmental glomerulosclerosis (4 patients), minimal change disease (2 patients), and IgM nephropathy (1 patient). Deposition of one or more immunoglobulins was noted in all but one patient studied with immunofluorescence. Corresponding electron-dense deposits were seen by electron microscopy in 78% of specimens. Prednisone did not induce a remission of nephrotic syndrome in the 13 patients treated, whereas cyclosporine did so in the 3 patients to whom it was administered. Five patients were in the end stage of renal disease within 8 months. Successful maintenance peritoneal dialysis was performed in three patients, but 80% of patients have died of human immunodeficiency virus-related complications; one patient was lost to follow-up. We conclude that immune-complex deposition is consistently seen in children with human immunodeficiency virus-associated nephrotic syndrome. This nephrotic syndrome is resistant to steroid therapy, but we observed a remission of the proteinuria with cyclosporine therapy in three patients. For patients with end-stage renal disease, maintenance peritoneal dialysis may improve the quality of life.

Metabolism of apolipoprotein B-containing lipoproteins in subjects with nephrotic-range proteinuria

Although hyperlipidemia is a well recognized complication of the nephrotic syndrome, the precise disturbances of lipoprotein metabolism which cause the elevated plasma lipid and lipoprotein concentrations have not been clearly defined in humans. This study examines the metabolism of apolipoprotein B-containing lipoproteins in patients with nephrotic-range proteinuria and in healthy controls. Two radioiodinated tracers of very low density lipoproteins (VLDL1, Sf60 to 400, and VLDL2, Sf20 to 60), were used to trace the metabolism of apolipoprotein B through the delipidation cascade from very low density lipoproteins (VLDL) to low density lipoproteins (LDL). The data from the apoB specific radioactivity curves and the pool sizes of apoB in four subfractions were analyzed by a multicompartmental modeling procedure using the SAAM 30 program. The main findings in the nephrotic group were: 1.) a consistent decrease in the fractional rate of apoB transfer from VLDL1----VLDL2 (median values-nephrotic 0.92 pools/day vs. controls 3.66, P less than 0.02) and from VLDL2----IDL (1.49 vs. 2.74, P less than 0.05); 2.) increased secretion of apoB into VLDL2 (14.5 mg/kg/day vs. 4.2, P less than 0.02); 3.) a trend towards decreased removal of IDL and LDL attributable to a defect in LDL receptor-mediated removal as previously shown (Metabolism 39:187-192, 1990). These findings suggest that catabolic defects of the apo B-containing lipoproteins are as important as increased hepatic synthesis in the pathogenesis of nephrotic hyperlipidemia in humans.

Lipoprotein distribution and composition in the human nephrotic syndrome

Plasma lipoprotein profiles were quantitated in 9 patients with the nephrotic syndrome. Six subjects were studied both during an active proteinuric phase and during a remission phase without proteinuria. During the proteinuric phase, the plasma triglyceride, cholesterol and apo B levels were markedly increased, whereas the HDL cholesterol, apo A-I, and apo A-II concentrations were normal. Analysis of the distribution and composition of the lipoprotein subclasses, separated by isopycnic ultracentrifugation, showed typical patterns characterized by: (1) elevated apo B-rich VLDL and LDL fractions, (2) the presence of a denser LDL subfraction, floating at d 1.053 g/ml, which contained about 35% of LDL cholesterol and apo B and (3) a redistribution among HDL subclasses. The HDL2b (d 1.063-1.100 g/ml) fraction was markedly decreased, while the HDL2a + 3a (d 1.100-1.150 g/ml) and HDL3b + 3c (d 1.150-1.210 g/ml) subclasses were moderately elevated. The decreased cholesterol and apo A-I contents of HDL2b therefore counterbalanced their increase in HDL2a + 3a and HDL3b + 3c, resulting in normal plasma HDL cholesterol and apo A-I concentrations. When reinvestigated during a remission phase without proteinuria, the nephrotic patient's overall lipoprotein distribution and composition were similar to those in healthy controls. The combination of several factors such as the presence of elevated apo B-rich VLDL, IDL and LDL, together with decreased HDL2 cholesterol and HDL2 apo A-I suggests that nephrotic patients are at increased risk for atherosclerosis.

Influence of proteinuria on glycated albumin values in diabetic patients with chronic kidney disease

BACKGROUND

Glycated albumin (GA), which is an alternative glycemic marker, is influenced by factors associated with albumin turnover, and it is not clear whether proteinuria influences GA values in diabetic patients with chronic kidney disease (CKD).

METHODS

We enrolled 94 diabetic patients with CKD stages 3 to 5. GA, glycated hemoglobin, and urinary protein excretion (UP) levels were consecutively obtained in each patient. The correlations between GA and UP and those between changes in GA and UP were examined.

RESULTS

There was a significant correlation between GA and UP in all cases (r=-0.46, p<0.0001), however no significant correlation was found in cases with UP of 0-3.49 g/day (r=0.01). GA values in cases with UP ≥3.5 g/day were significantly lower than those in cases with UP <3.5 g/day [UP ≥3.5 g/day and serum albumin (Alb) ≤3 g/dL; 12.0 ± 1.3%, UP ≥3.5 g/day and Alb >3 g/dL; 17.8 ± 4.3%, 0≥ UP <3.5 g/day; 21.2 ± 4.2%], while no significant difference in HbA(1c) or glucose levels was found. In cases with a minimum of UP ≥0.5 g/day, no significant correlation was found between the difference in GA and the difference in UP at the point of maximum UP and minimum UP (r=0.04).

CONCLUSION

Nephrotic-range proteinuria decreases GA values independent of the glycemic state, while non-nephrotic range proteinuria has no significant influence on GA values in diabetic CKD patients.

Effect of vegetarian soy diet on hyperlipidaemia in nephrotic syndrome

Nephrotic patients with persistent proteinuria also have various lipid abnormalities that may promote atherosclerosis and more rapid progression of renal disease. We aimed to find out whether dietary manipulation can correct the hyperlipidaemia found in these patients. After a baseline control period of 8 weeks on their usual diets, 20 untreated patients with chronic glomerular diseases, stable long-lasting severe proteinuria (5.9 [SD 3.4] g/24 h) and hyperlipidaemia (mean serum cholesterol 8.69 [3.34] mmol/l) ate a vegetarian soy diet for 8 weeks. The diet was low in fat (28% of total calories) and protein (0.71 [0.36] g/kg ideal body weight daily), cholesterol free, and rich in monounsaturated and polyunsaturated fatty acids (polyunsaturated/saturated ratio 2.5) and in fibre (40 g/day). After the diet period the patients resumed their usual diets for 8 weeks (washout period). During the soy-diet period there were significant falls in serum cholesterol (total, low-density lipoprotein, and high-density lipoprotein) and apolipoproteins A and B, but serum triglyceride concentrations did not change. Urinary protein excretion fell significantly. The concentrations of all lipid fractions and the amount of proteinuria tended to return towards baseline values during the washout period. We do not know whether the favourable effect of this dietary manipulation on proteinuria was due to the qualitative or quantitative modifications of dietary protein intake or was a direct consequence of the manipulation of dietary lipid intake.

High density lipoproteinuria in nephrotic syndrome

Intravenous administration of the aminonucleoside of puromycin produces the nephrotic syndrome (proteinuria, hypercholesterolemia, hypoproteinemia and edema) in rats. This model is very similar to human nephrotic syndrome caused by various disease states. The current study was designed to assess the nature of urinary lipoproteins in the urine of nephrotic rats, including studies related to the urinary loss of the "activator" apolipoproteins for the lipoprotein lipase-triglyceride interaction. Sprague-Dawley rats were given a single intravenous injection (10 mg/100 g) of puromycin aminonucleoside. Plasma and urine were collected before and 7, 18, 29, 36, and 53 days after injection of puromycin. Urine was fractionated in the preparative ultracentrifuge into density (d) fractions less than 1.006 (very low-density lipoproteins), d = 1.006-1.063 (low-density lipoproteins), and d = 1.063-1.210 (high-density lipoproteins--HDL). The cholesterol, triglyceride, phospholipid, and protein content of these fractions was analyzed. Lipoprotein electrophoresis was performed in agarose agar. Urine from normal and nephrotic rats was added to an in vitro system containing lipoprotein lipase and triglyceride. The free fatty acids (FFA) liberated were then measured as an index of urinary activator property on this system. Measurable urinary lipoproteins were present only on days 7 and 18 after induction of the nephrotic syndrome. Coelectrophoresis of these urinary lipoproteins with rat plasma revealed a single band having alpha- (HDL) electrophoretic mobility. The total mean protein content of day-7 urinary lipoproteins (64.3%) was greater than the content of plasma HDL (52.9%). The protein content of urinary lipoproteins also increased with time. When day-7 and day-18 postinjection urine at nephrotic rats was added to the lipoprotein lipase system, the hydrolysis of triglyceride yielded a mean of 0.320 and 0.235 muEq FFA/ml/20 min, respectively. Control rat urine yielded 0.030 muEq FFA/ml/20 min and 0.000 muEq FFA/ml/20 min 7 and 18 days after injection of normal saline, respectively. It is inferred that in this experimental model (1) high-density lipoproteins are probably excreted in the glomerular filtrate, (2) alterations in the composition of the excreted lipoproteins may occur during their passage through the nephron. The possibility that only a selective portion of the HDL spectrum is excreted into the glomerular filtrate cannot be excluded. It is suggested that the urinary or renal loss of this functionally important lipoprotein may contribute to the pathophysiology of hyperlipoproteinemia in the nephrotic syndrome.

Vitamin D metabolites in childhood nephrotic syndrome

We measured serum levels of total and ionised calcium, phosphate, intact parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D] and the vitamin D binding protein (DBP) in 14 children with idiopathic nephrotic syndrome and 10 healthy, age-matched controls. In all nephrotics serum DBP levels were below the normal range. Serum 25(OH)D was below 7 ng/ml in 10 of 14 nephrotic children and in the low normal range in the remaining 4 patients. The average serum 1,25(OH)2D levels were lower in the nephrotic patients than in the controls. However, free 1,25(OH)2D levels were normal in the nephrotic patients. Both serum 25(OH)D and 1,25(OH)2D correlated positively with the concentration of DBP. There was a significant negative correlation between serum DBP levels and the urinary protein excretion and a significant positive correlation between the urinary excretions of DBP and albumin. From this study it can be concluded that the nephrotic child is capable of maintaining appropriate serum concentrations of free calcitriol despite important urinary losses of both substrate and bound calcitriol.

Remission of idiopathic nephrotic syndrome after treatment with cyclosporin A

Nephrotic syndrome in minimal change lipoid nephrosis and focal segmental glomerulosclerosis may be due to alteration of glomerular anionic sites by a lymphokine. Six adults with nephrotic syndrome who were resistant to treatment with corticosteroids and immunosuppressants were treated with cyclosporin A. In three patients with minimal change lipoid nephrosis who had been nephrotic for 3.5 to 23 years proteinuria resolved within 12 to 42 days. Subsequently, these patients became dependent on cyclosporin A. In three patients with focal segmental glomerulosclerosis who had been nephrotic for four to six years mean (SD) 24 hour urinary protein decreased from 14.7 (8.4) g to 3.6 (0.6) g within 20 to 25 days, serum albumin concentration rose, and oedema subsided. One patient died of myocardial infarction when still in partial remission after 11 weeks' treatment. Two patients remained proteinuric despite continuing treatment with cyclosporin A, but control of sodium balance was easy and serum albumin concentrations remained higher than without cyclosporin A. In all patients renal function improved during treatment. These preliminary results show that cyclosporin A may be effective in the treatment of patients with nephrotic syndrome that resists every other form of treatment and especially in the treatment of those with minimal change lipoid nephrosis. The results are in keeping with a T lymphocyte mediated mechanism of minimal change lipoid nephrosis and focal segmental glomerulosclerosis, but they also suggest that minimal change lipoid nephrosis and focal segmental glomerulosclerosis are separate entities.