Low-density Lipoprotein Receptor Activities, Lipids, Apolipoprotein, and Clinical Course of Patients with Steroid-resistant Nephrotic Syndrome Treated with Low-density Lipoprotein Apheresis: A Case Series

Abstract

We herein report three cases of steroid-resistant nephrotic syndrome successfully treated with low-density lipoprotein apheresis (LDL-A). All patients were treated with a combination of steroids, cyclosporine, and LDL-A. In all cases, the serum concentrations of LDL, total and high-density lipoprotein cholesterol, and triglycerides were significantly lowered following LDL-A administration. Furthermore, the estimated LDL receptor activity increased, while both serum LDL and total cholesterol levels decreased, suggesting that LDL-A increases LDL receptor activity by driving changes in serum cholesterol concentration. This case series suggests that LDL-A increases LDL receptor activity, which may improve the intracellular uptake of cyclosporine.

Introduction

Nephrotic syndrome results in hyperlipidemia and alterations in lipid and lipoprotein metabolism, which contribute to the development and progression of cardiovascular diseases and kidney disease (1). Low-density lipoprotein apheresis (LDL-A) using a dextran sulfate cellulose column can be an effective treatment for steroid-resistant nephrotic syndrome, particularly focal segmental glomerulosclerosis (FSGS) (2,3).

However, while various hypothetical mechanisms have been reported (2,4), the precise mechanisms remain unclear.

Case Reports

Case 1

A 62-year-old man was admitted to our hospital with anasarca. A urinalysis revealed proteinuria (21.1 g/gCr). The serum creatinine and LDL-cholesterol levels were elevated at 1.18 mg/dL and 439 mg/dL, respectively. Serum total protein and albumin levels were low, at 4.0 g/dL and 1.0 g/dL, respectively. Based on these results, he was diagnosed with nephrotic syndrome. A renal biopsy revealed mild mesangial proliferation (Fig. 1a). Immunofluorescence staining revealed a granular pattern of immunoglobulin A (IgA) in the mesangium (Fig. 1b). The patient was diagnosed with IgA nephropathy (M0E0S1T1C0, according to the Oxford Classification).

Figure 1.

Renal biopsy specimen. Case 1. (a) Mild mesangial proliferation can be seen on periodic acid-Schiff staining (400× magnification). (b) Immunofluorescence staining showing a granular pattern of IgA in the mesangium (400× magnification). Case 2. (c) Segmental sclerotic lesions. Periodic acid-Schiff staining (400× magnification). (d) Immunofluorescence staining revealed focal and segmental deposition of IgM (400× magnification). (e) Electron microscopy showing foam cells (1,500× magnification) and (f) diffuse foot process effacement (5,000× magnification). Case 3. (g) Mild mesangial proliferation can be seen on periodic acid-Schiff staining (400× magnification). Immunofluorescence staining revealing granular (h) IgG and (i) IgG3 deposition in the glomerular capillary loops and mesangial area (400× magnification). (j) Electron microscopy showing electron-dense deposits on the epithelial side of the glomerular basement membrane (30,000× magnification). (k) Segmental sclerotic lesions and mild mesangial proliferation can be seen on periodic acid-Schiff staining (400× magnification). (l) Immunofluorescence staining showing attenuation of IgG deposition (400× magnification).

The patient's clinical course is shown in Fig. 2a. He was treated with methylprednisolone pulse therapy (1,000 mg/day) for 3 days, after which his prednisolone dose was reduced to 40 mg/day for 4 weeks; however, urine protein was persistent (16.4 g/gCr). After 2 courses of this regimen, his proteinuria had not decreased (12.0 g/gCr). Because IgA nephropathy rarely presents with steroid-resistant nephrotic syndrome, we considered the complication of minimal change nephrotic syndrome or FSGS based on the diffuse foot process effacement shown by electron microscopy. We subsequently initiated LDL-A treatment on day 43, but the proteinuria did not decrease even after 7 sessions of LDL-A (14.4 g/gCr). After administering cyclosporine on day 67 (after 12 sessions of LDL-A), his proteinuria gradually decreased to 7.6 g/gCr, and his proteinuria was further decreased at discharge (0.27 g/gCr).

Figure 2.

Clinical course of patients: (a) a 62-year-old man, (b) a 79-year-old woman, and (c) a 53-year-old woman. LDL-A: low-density lipoprotein apheresis, HD: hemodialysis, UP: urine protein, sCr: serum creatinine, sAlb: serum albumin, mPSL: methylprednisolone, PSL: prednisolone, CyA: cyclosporine, Tac: tacrolimus, MMF: mycophenolate mofetil

Case 2

A 79-year-old woman with anasarca was admitted to the hospital. A urinalysis revealed proteinuria (7.7 g/gCr) and hematuria (sediment red blood cells, 10-19 per high-power field). Her blood urea nitrogen and serum creatinine levels were elevated at 64.5 mg/dL and 3.03 mg/dL, respectively. In addition, she had low serum total protein and albumin levels of 4.6 g/dL and 1.4 g/dL, respectively. Her LDL-cholesterol level was 343 mg/dL. Based on these results, she was diagnosed with nephrotic syndrome.

Chest and abdominal computed tomography revealed pleural effusion, ascites, and a normal kidney. Because dyspnea and uremia were prominent, a renal biopsy was difficult to perform. The patient was therefore treated with steroids, including methylprednisolone pulse therapy. The patient's clinical course is shown in Fig. 2b. Hemodialysis was initiated due to oliguria on day 14, and cyclosporine was added on day 30. A renal biopsy was performed on day 35, revealing 17 glomeruli. None of the glomeruli had global sclerosis; however, several exhibited segmental sclerotic lesions (Fig. 1c). Immunofluorescence staining revealed focal and segmental depositions of IgM (Fig. 1d). Electron microscopy revealed foam cells (Fig. 1e) and diffuse foot process effacement (Fig. 1f). FSGS was diagnosed based on these findings.

After hemodialysis induction, 24-hour urine protein levels decreased due to oliguria, accompanied by decreased albumin levels. Due to an insufficient response, LDL-A therapy was initiated. On day 104, the patient's proteinuria, serum albumin, and serum creatinine levels had improved to 0.18 g/day, 2.0 g/dL, and 1.18 mg/dL, respectively.

Case 3

A 53-year-old woman with anasarca and oliguria was admitted to our hospital. She had a medical history of systemic lupus erythematosus and Sjögren syndrome. She had undergone a renal biopsy for nephrotic syndrome at 51 years old. Mild mesangial proliferation was also observed (Fig. 1g). Immunofluorescence staining revealed granular IgG (Fig. 1h) and IgG3 (Fig. 1i) deposition in the glomerular capillary loops and mesangial areas. Electron microscopy revealed electron-dense deposits on the epithelial side of the glomerular basement membrane (Fig. 1j).

Based on the above findings, she was diagnosed with class II+V lupus nephritis and received steroid pulse therapy and immunosuppressants, including tacrolimus, cyclosporine, and mycophenolate mofetil. She was also treated with statins and ezetimibe. However, she later experienced relapses (Fig. 2c). Upon admission for repeated a renal biopsy, a urinalysis revealed proteinuria (9.2 g/day) and hematuria (sedimented red blood cells, 10-19 per high-power field). Her blood urea nitrogen and serum creatinine levels were 20.7 mg/dL and 0.68 mg/dL, respectively. She had low serum total protein and albumin levels of 4.0 g/dL and 1.4 g/dL, respectively, while her LDL-cholesterol level was 353 mg/dL. A repeat biopsy revealed segmental sclerotic lesions in several glomeruli (Fig. 1k) and mild mesangial proliferation. Immunofluorescence staining revealed attenuation of IgG deposition (Fig. 1l). A diagnosis of class II and V lupus nephritis complicated with FSGS was established.

As long-term therapy with steroids and cyclosporine did not maintain remission, LDL-A therapy was initiated following methylprednisolone pulse therapy on day 35. After initiating LDL-A, her proteinuria and serum albumin levels gradually improved to 0.56 g/day and 3.0 g/dL, respectively.

Methods

In the present cases, three patients with steroid-resistant nephrotic syndrome were treated with a combination of steroids, cyclosporine, and LDL-A administered over a total of 12 sessions (twice a week) using a dextran sulfate adsorption system (Liposorber LA15; Kaneka, Osaka, Japan). Approximately 4,000-5,000 mL of plasma was administered per session. We measured blood cyclosporine levels 1-3 times during this study, finding that they were maintained at 600-800 ng/mL for 2 hours following oral administration. Subsequently, we evaluated the serum LDL-cholesterol, total cholesterol, high-density lipoprotein (HDL)-cholesterol, non-HDL-cholesterol, and triglyceride concentrations as well as the LDL-cholesterol/HDL-cholesterol ratio before and after LDL-A administration. We further monitored the LDL receptor activity and lipid levels along with apolipoprotein B, apolipoprotein A1, and apolipoprotein C2 levels following LDL-A administration. LDL receptor activity was estimated using a previously reported formula (5): LDL receptor activity (%)=63.595+13.459×apolipoprotein C2 (mg/dL)−0.366×apolipoprotein B (mg/dL).

Results

Changes in serum lipid levels after LDL-A treatment

The serum concentrations of LDL-cholesterol, total cholesterol, HDL-cholesterol, non-HDL-cholesterol, and triglycerides as well as the LDL-cholesterol/HDL-cholesterol ratio after LDL-A administration were significantly lower than those before LDL-A administration (Table).

Table.

Changes in Serum Lipid Levels before and after LDL-A Treatment.

Variables		Before		After		p
LDL cholesterol (mg/dL)		90 [71-147]		13 [11-21]		<0.001***
Total cholesterol (mg/dL)		198 [142-251]		76 [64-92]		<0.001***
HDL cholesterol (mg/dL)		50 [43-72]		45 [38-62]		<0.001***
Non-HDL cholesterol (mg/dL)		138 [96-194]		28 [25-37]		<0.001***
Triglycerides (mg/dL)		257 [161-389]		61 [49-74]		<0.001***
LDL cholesterol/HDL cholesterol ratio		1.8 [1.4-2.5]		0.3 [0.3-0.4]		<0.001***

Differences between groups were assessed using Mann-Whitney’s rank-sum test.

***p<0.001, when comparing before versus after.

LDL-A: low-density lipoprotein apheresis, HDL: high-density lipoprotein

Time course of estimated LDL receptor activity, lipid levels, and apolipoprotein concentrations following LDL-A administration

The time course of the estimated LDL receptor activity, lipid levels, and apolipoprotein concentrations following LDL-A administration are shown in Fig. 3. In all cases, the estimated LDL receptor activity level increased (Fig. 3a), while both the serum LDL-cholesterol and total cholesterol levels decreased (Fig. 3b, c). No definite trends were observed for HDL-cholesterol, triglycerides, or apolipoprotein C2 (Fig. 3d, e, i). The concentrations of apolipoprotein B decreased, while those of apolipoprotein A1 increased, resulting in a reduction in the apolipoprotein B/apolipoprotein A1 ratio following LDL-A (Fig. 3f-h).

Figure 3.

Time course of LDL receptor activities, serum lipid levels, and apolipoprotein concentrations during LDL-A treatment. Levels of (a) LDL receptor activity, (b) serum LDL-cholesterol, (c) total cholesterol, (d) HDL-cholesterol, (e) triglycerides, (f) apolipoprotein B, (g) apolipoprotein A1, (h) apolipoprotein B/apolipoprotein A1, and (i) apolipoprotein C2 over time.

Discussion

Treatment of steroid-resistant nephrotic syndrome remains a major challenge for nephrologists. In this report, the patients were successfully treated with a combination of steroids, cyclosporine, and LDL-A, resulting in favorable outcomes. Two patients achieved complete remission (<0.3 g/day or <0.3 g/gCr), while 1 patient achieved only incomplete remission I (0.3-1.0 g/day or 0.3-1.0 g/gCr). All three cases in this study were atypical, with considerable differences in clinical course and pathophysiology. However, the significance of this case report is that proteinuria markedly decreased with the common treatments in all three cases. This study highlights an important clinical issue in that LDL-A may be useful for improving LDL receptor activity and hypercholesterolemia and decreasing proteinuria. To our knowledge, there have been few reports on the time course of these factors, especially LDL receptor activity, following LDL-A administration in steroid-resistant nephrotic syndrome.

LDL plays an important role in cholesterol metabolism, while the activity of LDL receptors in the liver mainly affects serum cholesterol concentration (6). Statins enhance LDL receptor activity by suppressing cholesterol synthesis in the liver. Nephrotic syndrome results in acquired LDL receptor deficiency, leading to increased serum LDL-cholesterol levels (1). LDL-A lowers lipid levels and improves the bioavailability of steroids and calcineurin inhibitors (7). A negative correlation has previously been reported between LDL receptor activity and serum LDL-cholesterol levels (8); therefore, our results suggest that LDL-A increases LDL receptor activity by altering the serum cholesterol concentration. Enhancement of LDL receptor activity may further improve the intracellular uptake of cyclosporine, a lipid-soluble drug, through LDL receptors (9), which may have resulted in favorable therapeutic effects in our cases. The apolipoprotein A1 ratio has previously been identified as a marker of plasma atherogenicity (10) and cardiovascular risk (11). Our results indicated that LDL-A decreases the apolipoprotein B/apolipoprotein A1 ratio, leading to a desirable outcome.

This study suggests that LDL-A increases LDL receptor activity, which may improve the intracellular uptake of cyclosporine. However, in Case 1, the patient was administered CyA along with LDL-A, suggesting that LDL-A might directly improve nephrotic syndrome but not the response to CyA. Therefore, there may be other mechanisms of LDL-A besides elevated LDL receptor activities. The mechanisms underlying the effects of LDL-A on steroid-resistant nephrotic syndrome may involve improvement in dyslipidemia, removal of autoantibodies, reduced potential vascular permeability factors and inflammatory cytokines, absorption of humoral factors, and improved responsiveness to immunosuppressants (2,12,13).

Several limitations associated with the present study warrant mention. First, considering that some patients with steroid-resistant nephrotic syndrome can achieve remission without LDL-A, increasing the LDL receptor activity may be just one possible mechanism. Second, LDL receptor activities were not directly evaluated. Third, in Case 3, the patient underwent LDL-cholesterol- and triglyceride-lowering therapy, which might have affected the increase in LDL receptor activity.

In conclusion, LDL-A should be administered to patients with steroid-resistant nephrotic syndrome who do not respond to immunosuppressants.