Lipoprotein glomerulopathy: renal lipidosis induced by novel apolipoprotein E variants

Clinicopathological characteristics and gene mutations in 11 patients with lipoprotein glomerulopathy

OBJECTIVE

Lipoprotein glomerulopathy (LPG) is a rare disorder characterized by the development of glomerular lipoprotein thrombosis. LPG exhibits familial aggregation, with mutations in the apolipoprotein E (APOE) gene identified as the leading cause of this disease. This study aimed to investigate APOE gene mutations and the clinicopathological features in eleven LPG patients.

METHODS

Clinicopathological and follow-up data were obtained by extracting DNA, followed by APOE coding region sequencing analysis. This study analyzed clinical and pathological manifestations, gene mutations, treatment and prognosis.

RESULTS

The mean age of the eleven patients was 33.82 years. Among them, five had a positive family history for LPG, ten presented with proteinuria, four exhibited nephrotic syndrome, and six presented with microscopic hematuria. Dyslipidemia was identified in ten patients. In all renal specimens, there was evident dilation of glomerular capillary lumens containing lipoprotein thrombi, and positive oil red O staining was observed in frozen sections of all samples. APOE gene testing revealed that one patient had no mutations, while the remaining ten patients exhibited mutations in the APOE gene, with three patients presenting with multiple mutations simultaneously. Following the confirmation of LPG diagnosis, treatment with angiotensin-converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB) was initiated, and the disease progressed slowly.

CONCLUSION

LPG is histologically characterized by lamellated lipoprotein thrombi in glomeruli, and kidney biopsy is essential for diagnosis. Mutations in the APOE gene are the leading cause of LPG. This study revealed clinicopathological characteristics and APOE gene mutations in patients with LPG, which helps us better understand the disease.

Lipoprotein Glomerulopathy With Complete Resolution With Fenofibrate: Report of First Case From Pakistan

Background: Lipoprotein glomerulopathy is an infrequent glomerular disorder that culminates in nephrotic syndrome and often progresses to kidney failure. Whereas most patients have been reported in Japan and China, limited reports have been documented outside these regions. This patient represents the first report of lipoprotein glomerulopathy in Pakistan. Case Presentation: A 25-year-old male patient, hypertensive for 2 years, presented with progressive body edema, frothy urine, and fatigue. Examination revealed elevated blood pressure, bilateral pedal edema, and positive shifting dullness. Laboratory results showed significant proteinuria and elevated cholesterol and triglyceride levels. Renal biopsy revealed enlarged glomeruli with a dilated capillary lumen filled with pale-staining mesh-like material "lipoprotein thrombi." Mild tubular atrophy and interstitial inflammation were observed. No interstitial fibrosis was evident. Electron microscopy detailed the lipoprotein thrombi with lipid granules and vacuoles of various sizes. A diagnosis of lipoprotein glomerulopathy was rendered. Treatment with fenofibrate, rosuvastatin, and captopril led to notable improvements in symptoms, blood pressure, and lipid levels during a 6-month follow-up. Subsequent biopsy showed complete resolution of the lipoprotein thrombi and a significant reduction in subendothelial granular densities. However, the flocculent subendothelial material persisted to some extent despite the complete resolution of lipoprotein thrombi. Conclusion: This report underscores the rarity of lipoprotein glomerulopathy in Pakistan and contributes valuable insights into its histopathologic features and global epidemiology. This unique instance aims to raise awareness among healthcare professionals, aiding in improved recognition of this rare entity. The favorable response to fenofibrate treatment underscores its effectiveness in managing lipoprotein glomerulopathy.

Whole Exome Sequencing Reveals a Novel APOE Mutation in a Patient With Sporadic Early-Onset Alzheimer's Disease

Apolipoprotein (APOE) is implicated and verified as the main risk factor for early-onset Alzheimer's disease (AD). APOE is a protein that binds to lipids and is involved in cholesterol stability. Our paper reports a case of a sporadic early-onset AD (sEOAD) patient of a 54-year-old Korean man, where a novel APOE Leu159Pro heterozygous mutation was revealed upon Whole Exome Sequence analysis. The proband's CSF showed downregulated levels of Aβ42, with unchanged Tau levels. The mutation is in the Low-Density Lipoprotein Receptor (LDLR) region of the APOE gene, which mediates the clearance of APOE lipoproteins. LDLR works as a high-affinity point for APOE. Studies suggest that APOE-LDLR interplay could have varying effects. The LDLR receptor pathway has been previously suggested as a therapeutic target to treat tauopathy. However, the APOE-LDLR interaction has also shown a significant correlation with memory retention. Leu159Pro could be an interesting mutation that could be responsible for a less damaging pattern of AD by suppressing tau-association neurodegeneration while affecting the patient's memory retention and cognitive performance.

Posttransplant proteinuria due to Apolipoprotein E2 deposition in a kidney allograft

Lipoprotein deposition disorders limited to the kidney and causing proteinuria are rare. We present a case of nephrotic range proteinuria presenting within 4 months after deceased donor renal transplantation in a patient with end-stage kidney disease presumed secondary to hypertension. Two transplant kidney biopsies were performed sixteen weeks after transplantation, and one year after the first biopsy, both showing lipoprotein deposits in the glomeruli, progressive focal segmental glomerulosclerosis, and effacement of visceral foot processes. The patient had a normal lipid profile. Based on previous case reports of Apolipoprotein E variants causing proteinuria in native kidneys, Apolipoprotein E genotyping was performed. Genotyping showed Apolipoprotein E2 homozygosity. This Apolipoprotein E variant has been associated with lipoprotein deposition, proteinuria, and progressive kidney disease in the native kidneys. However, this is the first case of Apolipoprotein E2 homozygosity-related kidney disease in a transplant recipient. The patient was treated with fenofibrate, angiotensin enzyme inhibition, and angiotensin receptor blockade with reduction in proteinuria, and he kept good stable kidney function.

Case Report: A Pediatric Case of Lipoprotein Glomerulopathy in China and Literature Review

Background: Lipoprotein glomerulopathy is a rare kidney disease characterized by lipoprotein thrombi in the glomerulus. Here, we report a case of lipoprotein glomerulopathy in a Chinese pediatric patient. Furthermore, we summarized the clinical features and genetic characteristics of lipoprotein glomerulopathy in China. Case Presentation: An 11-year-old Chinese girl presented with nephrotic syndrome with anemia (98 g/L). After excluding secondary causes, primary nephrotic syndrome was considered. Treatment with prednisone (60 mg/day) did not improve her condition. Renal biopsy showed marked dilation of the capillary lumen with lipoprotein thrombi and positive oil red O staining. Genetic testing revealed the genetic variant c.127C > T (p.R43C), known as the Kyoto mutation of the APOE gene. These findings are consistent with the diagnosis of lipoprotein glomerulopathy. Prednisone was gradually tapered and captopril was initiated. A 2-year follow-up revealed elevated urine protein and serum creatinine levels. We also reviewed 17 pediatric and 156 adult cases of lipoprotein glomerulopathy reported in China from the year of creation to 2021. The most common clinical features were edema, hematuria, hypertriglyceridemia, and increased serum apoE levels. Extra-renal manifestations included anemia, splenomegaly, and cardiac lipoprotein deposition. Conclusion: APOE Kyoto is the most common mutation in patients with lipoprotein glomerulopathy. In China, homozygosity for E3 (E3/3) is the most common isoform.

Clinical and genetic analysis of lipoprotein glomerulopathy patients caused by APOE mutations

Background

Lipoprotein glomerulopathy (LPG) is a rare kidney disease caused by APOE mutations. The aim of this study was to correlate the genetic and clinical features of LPG.

Methods

Totally eight LPG patients were recruited in this study and Sanger sequencing of APOE was performed for all available family members. Clinical and histological features were analyzed. A literature review of LPG was also conducted.

Results

Genetic analysis revealed five patients with APOE‐Kyoto, two with APOE‐Osaka/Kurashiki, and one with APOE‐Chicago mutations. LPG patients with urine protein reduced more than 50% had a slower decrease in renal function than those with less urine protein reduction (estimated glomerular filtration rate reduction rate −5.0 ± 0.8 vs. 1.5 ± 0.7 ml/min per 1.73 m²⋅month⁻¹, p = .03). We then enrolled 95 LPG patients from previous studies and this study. LPG patients had higher blood pressure (mean arterial pressure: 109.4 ± 19.4 vs. 94.4 ± 11.1 mmHg, p < .001) than the control group. Interestingly, patients with APOE mutations in the LDL receptor binding region had higher serum apolipoprotein E (apoE) levels [ln(apoE): 2.7 ± 0.4 vs. 2.0 ± 0.5 mg/dl, p < .001] in comparison to other domains.

Conclusion

Here, we report for the first time APOE‐Osaka/Kurashiki and APOE‐Chicago mutations in the Chinese population. LPG was associated with higher blood pressure and serum apoE levels were higher in patients with mutations in LDL receptor binding region. In addition, the findings further indicated that treatment of proteinuria might slow down renal function progression in these patients.

Apolipoprotein E-related glomerular disorders

Of the glomerular disorders that occur due to apolipoprotein E (apoE) mutations, apoE2 homozygote glomerulopathy and lipoprotein glomerulopathy (LPG) have been characterized. ApoE2 homozygote glomerulopathy has been found in individuals expressing homozygous apoE2/2. This was characterized histologically by glomerulosclerosis with marked infiltration of foam cells derived from macrophages, and occasionally with non-lamellated lipoprotein thrombi. Recently, several cases of apoE Toyonaka (Ser197Cys) combined with homozygous apoE2/2 have been reported, in which non-immune membranous nephropathy-like features were observed in glomeruli. Interestingly, in these cases, apoE accumulation was identified by tandem mass spectrometry. Therefore, it is speculated that these findings may arise from apoE molecules without lipids, which result from hinge damage by apoE Toyonaka and may cross the glomerular basement membrane as small molecules. LPG is primarily associated with heterozygous apoE mutations surrounding the low-density lipoprotein-receptor binding site, and it is histologically characterized by lamellated lipoprotein thrombi that lack foam cells. Recent studies have suggested that LPG can be induced by thermodynamic destabilization, hydrophobic surface exposure, and the aggregation of apoE resulting from the incompatibility of apoE mutated residues within helical regions. Additionally, apoE5 may play a supporting role in the development of LPG and in lipid-induced kidney diseases via hyperlipoproteinemia. Thus, it is interesting that many apoE mutations contribute to characteristic glomerular disorders through various mechanisms. In particular, macrophages may uptake lipoproteins into the cytoplasm and contribute to the development of apoE2 homozygote glomerulopathy as foam cells, and their dysfunction may contribute to the accumulation of lipoproteins in the glomerulus, causing lipoprotein thrombi in LPG.

Pathogenesis, histopathologic findings and treatment modalities of lipoprotein glomerulopathy: A review

Lipoprotein glomerulopathy (LPG) is an uncommon cause of nephrotic syndrome and/or kidney failure. At microscopy, LPG is characterized by the presence of lipoprotein thrombi in dilated glomerular capillaries due to different ApoE mutations. ApoE gene is located on chromosome 19q13.2, and can be identified in almost all serum lipoproteins. ApoE works as a protective factor in atherosclerosis due its interaction with receptor-mediated lipoprotein clearance and cholesterol receptor. Most common polymorphisms include ApoE2/2, ApoE3/2, ApoE3/3, ApoE4/2, ApoE4/3, and ApoE4/4. All age-groups can be affected by LPG, with a discrete male predominance. Compromised patients typically reveal dyslipidemia, type III hyperlipoproteinemia, and proteinuria. LPG treatment includes fenofibrate, antilipidemic drugs, steroids, LDL aphaeresis, plasma exchange, antiplatelet drugs, anticoagulants, urokinase, and renal transplantation. Recurrence in kidney graft suggests a pathogenic component(s) of extraglomerular humoral complex resulting from abnormal lipoprotein metabolism and presumably associated to ApoE.

Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs

Miniature Schnauzer dogs are predisposed to idiopathic hypertriglyerceridemia, which increases risk for diseases such as pancreatitis and gallbladder mucocele. Recently, elevated triglyceride concentrations have been associated with proteinuria in this breed, although it is difficult to determine which abnormality is primary. Retrospective review of renal tissue from 27 proteinuric Miniature Schnauzers revealed that 20 dogs had ultrastructural evidence of osmophilic globules consistent with lipid in glomerular tufts. Seven of these dogs had lipid thromboemboli in glomerular capillary loops that distorted their shape and compressed circulating erythrocytes. Triglyceride concentrations were reported in 6 of these 7 dogs, and all were hypertriglyceridemic. In addition, glomerular lipidosis (defined as accumulation of foam cells within peripheral capillary loops) was identified in a single dog. The remaining 12 dogs had smaller amounts of lipid that could only be identified ultrastructurally. Neither signalment data nor clinicopathologic parameters (serum albumin, serum creatinine, urine protein-to-creatinine ratio, and blood pressure) differed among the various types of lipid lesions. During the time course of this study, all dogs diagnosed with glomerular lipid thromboemboli were Miniature Schnauzers, underscoring the importance of recognizing these clear spaces within capillary loops as lipid.

Macrophage-derived apoESendai suppresses atherosclerosis while causing lipoprotein glomerulopathy in hyperlipidemic mice

Lipoprotein glomerulopathy (LPG) is a renal disease often accompanied by dyslipidemia and increased serum apoE levels. apoESendai (Arg145Pro), a rare mutant based on the apoE3 sequence carrying an apoE2 charge, causes LPG in humans and transgenic mice, but its effects on the artery wall are unknown. Macrophage expression of apoESendai may also directly influence renal and arterial homeostasis. We investigated the effects of macrophage-expressed apoESendai in apoE(-/-) mice with or without LDL receptor (LDLR). Murine bone marrow transduced to express apoE2, apoE3, or apoESendai was transplanted into lethally irradiated mice. Macrophage apoESendai expression reduced aortic lesion size and inflammation by 32 and 28%, respectively, compared with apoE2 in apoE(-/-) recipients. No differences in lesion size or inflammation were found between apoESendai and apoE3 in apoE(-/-) recipients. Macrophage apoESendai expression also reduced aortic lesion size by 18% and inflammation by 29% compared with apoE2 in apoE(-/-)/LDLR(-/-) recipients. Glomerular lesions compatible with LPG with increased mesangial matrix, extracellular lipid accumulation, and focal mesangiolysis were only observed in apoE(-/-)/LDLR(-/-) mice expressing apoESendai. Thus, macrophage expression of apoESendai protects against atherosclerosis while causing lipoprotein glomerulopathy. This is the first demonstration of an apoprotein variant having opposing effects on vascular and renal homeostasis.

Topics in lipoprotein glomerulopathy: an overview

Here, we introduce four topics in lipoprotein glomerulopathy (LPG). To date, approximately 150 cases of LPG have been reported worldwide. Recently two groups studied hot spots of APOE-Sendai and APOE-Kyoto, the representative variants of LPG, in narrow areas of Japan and China, respectively. They suggest that both variants have descended through a founder effect. APOE-Sendai and APOE-Kyoto cause different transformations of apolipoproteins aggregating lipoproteins and resulting in lipoprotein thrombi within the glomerulus. Moreover, the macrophage impairment in LPG may provide another mechanism for lipoprotein thrombi in which massive lipoproteins accumulate in the glomerulus without foam cells. On the other hand, the administration of fibrate with the intensive control of triglyceride and apolipoprotein E particularly from the early phase will ameliorate LPG and prevent renal dysfunction.

Macrophage impairment produced by Fc receptor gamma deficiency plays a principal role in the development of lipoprotein glomerulopathy in concert with apoE abnormalities

BACKGROUND

To obtain a clear understanding of the pathogenesis of lipoprotein glomerulopathy (LPG), we studied the role of the deficiency of Fc receptor gamma chain (FcRγ) for the development of LPG in concert with apolipoprotein E (apoE) abnormalities.

METHODS

We generated apoE and FcRγ double-knockout (FcRγ/apoE-KO) mice, and subsequently introduced several kinds of human recombinant apoE genes. At 21 days after infection, the mice were sacrificed and histologically examined. Peritoneal macrophages were evaluated for their response to modified lipids.

RESULTS

In the FcRγ/apoE-KO mice, the human apoE3-injected mice showed the most drastic LPG-like changes, as well as prominent hypertriglyceridemia. Meanwhile, relative to the human apoE3-injected mice, the FcRγ/apoE-KO mice showed greater lipoprotein deposition and less macrophage infiltration into the mesangial area. Moreover, the peritoneal macrophages in the apoE/FcRγ-KO mice were impaired in lipid uptake and secretion of the cytokines monocyte chemotactic protein-1 and regulated upon activation, normal T-cell expressed and secreted, after the uptake of oxidized low-density lipoprotein.

CONCLUSIONS

These results suggest that the impairment of macrophage function resulting from FcRγ deficiency plays a principal role in the development of LPG in the presence of apoE abnormalities.

Scavenger receptor expressions in the kidneys of mice with lipoprotein glomerulopathy

BACKGROUND

To clarify whether dysfunction of the scavenger receptor (SR) participates in the development of lipoprotein glomerulopathy (LPG) in immunoglobulin F(c) receptor γ chain (F(c)Rγ)-deficient mice [F(c)Rγ knock-out (KO) mice] with induced chronic graft-versus-host disease (cGVHD).

METHOD

In wild-type (WT) and F(c)Rγ KO C57BL/6 mice, cGVHD was induced by injection of lymphoid cells from donor Bm12 mice. At 6 months after injection, the mice were sacrificed and histologically examined. Total RNA was extracted from the kidneys and cytokine, chemokine, and SR transcript expressions were evaluated by reverse transcription-polymerase chain reaction.

RESULTS

Three of 4 female cGVHD(+)/F(c)Rγ KO mice presented LPG in >60% of glomeruli. cGVHD(-) and cGVHD(+)/WT mice did not show LPG. The SRs CD36, CD68, and CXCL16 showed a significant difference in the values of their transcripts between cGVHD(+)/WT and cGVHD(+)/F(c)Rγ KO mice. Among them, only CD36 showed a drastic decline of mRNA expressions in cGVHD(+)/F(c)Rγ KO mice.

CONCLUSION

CD36 may play a crucial role in the development of LPG in F(c)Rγ KO mice with cGVHD. In addition to the apolipoprotein E mutation, dysfunction of lipid clearance in the kidney might be one of the factors for the development of LPG.

Successful treatment of lipoprotein glomerulopathy in a daughter and a mother using niceritrol

We report two patients, a daughter and a mother, with lipoprotein glomerulopathy (LPG) who were successfully treated with niceritrol. Both patients carried a mutation in the apolipoprotein E (apoE) gene known as ApoE Tokyo/Maebashi. The daughter was found to have proteinuria at the age of 4 years. Four years later, she was diagnosed as having LPG based on a renal biopsy. She was treated with several medications including pravastatin, ethyl icosapentate, enalapril, warfarin and cyclophosphamide, all of which failed to reduce her proteinuria. At the age of 17 years, she exhibited an increase in proteinuria and a decline in renal function, despite ongoing treatment with pravastatin and enalapril. After switching from pravastatin to niceritrol, a marked reduction in the proteinuria and an improvement in renal function were observed. Her mother was found to have proteinuria at the age of 57 years and was diagnosed as having LPG based on a renal biopsy. She was also treated with niceritrol, resulting in an improvement in her proteinuria and renal function. These cases suggest that niceritrol might be a useful therapeutic option for LPG.

Dyslipidemia in children with chronic kidney disease

Dyslipidemia, a known risk factor for atherosclerosis, is frequent among both adults and children with chronic kidney disease. Here, we describe the prevalence and pattern of dyslipidemia from a cross-sectional analysis of 391 children aged 1-16 years, enrolled in the multicenter Chronic Kidney Disease in Children (CKiD) study, with a median glomerular filtration rate (GFR), measured by the plasma disappearance of iohexol, of 43 ml/min per 1.73 m2. Multivariate analysis was applied to adjust for age, gender, body mass index (BMI), GFR, and the urinary protein/creatinine ratio. Proteinuria was in the nephrotic range in 44 and the BMI exceeded the 95th percentile in 57 patients of this cohort. Baseline lipid analysis found a high prevalence of hypertriglyceridemia in 126, increased non-HDL-C in 62, and reduced HDL-C in 83. Overall, 177 children had dyslipidemia, of whom 79 had combined dyslipidemia. Lower GFR was associated with higher triglycerides, lower HDL-C, and higher non-HDL-C. Nephrotic-range proteinuria was significantly associated with dyslipidemia and combined dyslipidemia. Compared with children with a GFR>50, children with a GFR<30 had significantly increased odds ratios for any dyslipidemia or for combined dyslipidemia. Hence, among children with moderate chronic kidney disease, dyslipidemia is common and is associated with lower GFR, nephrotic proteinuria, and non-renal factors including age and obesity.

Improvement of nephrotic syndrome by intensive lipid-lowering therapy in a patient with lipoprotein glomerulopathy

Lipoprotein glomerulopathy (LPG) is a rare hereditary disease characterized by the accumulation of much thrombi material consisting of lipoproteins at the glomerular capillary lumen. Most patients show nephrotic syndrome; nearly half progress to chronic renal failure. Intensive therapy with lipid-lowering agents reportedly engenders clinical remission with histological resolution. We report the case of a 14-year-old Japanese female patient who had been in a nephrotic condition with hematuria from 4 years old and who had been diagnosed based on pathological and molecular examination at 7 years old. We initially treated the patient with probucol, enalapril (angiotensin-converting enzyme inhibitor: ACEI), and dipyridamole from age 7, but achieved no improvement in her nephrotic status. Subsequently, we replaced probucol with bezafibrate at age 11 and added atorvastatin calcium hydrate and valsartan (angiotensin II receptor blocker: ARB) the following year. The next 3 years' treatment improved her nephrotic status, decreased serum apolipoprotein E, and markedly decreased intraglomerular lipoprotein thrombi. Early and intensive therapy with antilipidemic drugs combined with ACEI and ARB is inferred to be effective for LPG.

Lipoprotein glomerulopathy induced by ApoE-Sendai is different from glomerular lesions in aged apoE-deficient mice

OBJECTIVE

A mutant of apolipoproteinE (apoE), ApoE-Sendai (Arg145Pro), is one of the major causative factors of human lipoprotein glomerulopathy (LPG). An apoE-deficient mouse with introduced ApoE-Sendai gene (ApoE-Sendai mouse) developed a murine counterpart of LPG, whereas it was also reported that apoE-deficient mouse (apoE KO mouse) spontaneously developed LPG-like lesion regardless of introduction of ApoE-Sendai gene. In the present study, we differentiated renal lesions between these two models by detailed analyses of histology and lipoprotein profile, and clarified the role of apoE variants.

METHOD

ApoE-Sendai mice were induced by injection of adenovirus vectors. The kidneys showing LPG-like lesions in apoE-Sendai and apoE KO mice were histopathologically evaluated. Plasma lipids and lipoproteins of both mice were also examined.

RESULTS

Histological alteration of the kidney in ApoE-Sendai mice was observed with light microscopy (in 40 out of 50 mice; mild 24, moderate 13, severe 3). Characteristic lesions were dilated vascular lumens mimicking lipoprotein thrombi in human LPG. Similar changes were found in hematoxylin-eosin stained sections of aged apoE KO mice. Meanwhile, periodic acid-Schiff, Azan Mallory, and Oil red O/Sudan III stained sections revealed that the dilated lumens of ApoE-Sendai mice mainly contained lipids and lipoproteins but those of aged apoE KO mice contained much other materials, e.g., proteins and fibrils. These findings were supported by electron micrographs, in which round-shaped droplets indicating lipoproteins were observed in ApoE-Sendai mice but not in aged apoE KO mice. In the kidney of apoE KO mice many anti-mouse CD68 Ab positive cells were detected. This contrasts with the result seen in ApoE-Sendai mice. The plasma lipoprotein compositions of the two types of mice were totally different.

CONCLUSION

It was certain that the kidneys of aged apoE KO mice showed morphological alteration, but the histological findings of glomerular lesions were different from those seen in the kidneys of ApoE-Sendai mice. According to the histological findings and plasma lipoprotein profile, ApoE-Sendai mice, not apoE KO mice, is a murine model for human LPG. This means that apoE variants are essential to LPG.

Successful treatment of patients with lipoprotein glomerulopathy by protein A immunoadsorption: a pilot study

BACKGROUND

No established therapy is available for patients with lipoprotein glomerulopathy (LPG). Protein A immunoadsorption has been proved to be effective in reducing proteinuria in patients with nephrotic syndrome. In this uncontrolled pilot study, we investigated the efficiency of immunoadsorption onto staphylococcal protein A as treatment for LPG.

METHODS

Thirteen patients with renal biopsy-proven LPG were treated with staphylococcal protein A immunoadsorption. Immunoadsorption was administered for 10 cycles per session and 10 sessions as a course. A total of 30 l of plasma was regenerated in each course.

RESULTS

Single immunoadsorption course led to a rapid decline in proteinuria from 4.01 +/- 3.09 g/24 h to 1.21 +/- 0.97 g/24 h (mean +/- SD) (n = 13, P = 0.001), along with a dramatic decline in apolipoprotein E (apo E) from 9.79 +/- 5.04 mg/dl to 6.20 +/- 2.22 mg/dl (P = 0.004). A repeated renal biopsy (n = 12) showed that intraglomerular lipoprotein thrombi almost disappeared. Six patients were enrolled in the investigation of long-term outcome, and proteinuria returned to baseline levels within 12 months. Four recurrent patients received repeat immunoadsorption treatment; proteinuria decreased from 5.02 +/- 1.85 g/24 h to 1.64 +/- 0.55 g/24 h at the end of the treatment, serum apo E decreased from 14.65 +/- 11.17 mg/dl to 7.90 +/- 1.72 mg/dl. No patients suffered from severe complications.

CONCLUSION

Our observations suggest that immunoadsorption onto protein A might be an effective treatment for resolving intraglomerular thrombi and improving nephrotic syndrome in patients with LPG. Further studies are required to define the influence of immunoadsorption on long-term effects in LPG patients.

Lipoprotein glomerulopathy: a new apolipoprotein E mutation with enhanced glomerular binding

We describe a case of lipoprotein glomerulopathy, the second ever reported from the United States, in a Mexican man with a hitherto undescribed mutation in the apolipoprotein E gene (substitution of proline for arginine at position 147 [Arg147Pro]). In this patient, glomerular basement membranes showed double contours and circumferential mesangial extensions, suggesting that deposition of lipids could be injurious to endothelial cells. Immunofluorescence staining of thrombi was positive for apolipoprotein E and B. To study the reason for lipid deposition in glomeruli, we incubated normal human kidney sections with serum from the patient and a healthy control. Apolipoprotein E from the patient's serum showed binding to the glomerular capillary wall, but the control did not, suggesting enhanced binding of the mutated apolipoprotein E to glomerular capillaries. Apolipoprotein E genotyping by means of restriction endonuclease digestion of polymerase chain reaction-amplified genomic DNA showed it to be of the wild-type E3/E3.

Impact of Lipoprotein Glomerulopathy on the Relationship Between Lipids and Renal Diseases

Lipoprotein glomerulopathy (LPG) is a unique entity of renal lipidosis characterized by peculiar histopathologic characteristics of lipoprotein thrombi and an abnormal plasma lipoprotein profile resembling type III hyperlipoproteinemia, with a marked increase in serum apolipoprotein E (apoE) concentrations. At present, 65 cases have been reported worldwide, although most patients are found in Japan and east Asian countries. Recently, we identified 4 types of novel apoE mutations associated with LPG. In particular, a mutation designated apoE Sendai, in which arginine 145 is substituted with proline, occurs in the majority of Japanese patients. The virus-mediated transduction of apoE Sendai resulting in the development of LPG in apoE-deficient mice confirms the etiologic role of apoE mutation in LPG. Conversely, experimental graft-versus-host disease induced in Fc receptor gamma-chain-deficient mice showed LPG-like lesions in glomeruli without apoE mutations. Considered together, we believe that intrinsic factors in the kidney also contribute to the induction of LPG. Today, apoE and related lipid abnormalities are reported to have an important role in the development of various renal diseases, eg, diabetic nephropathy and immunoglobulin A nephropathy. In this article, we review clinical and histopathologic features of LPG, describe the etiologic role of apoE variants and intrinsic renal factors, and discuss the impact of LPG on mechanisms of other renal diseases.

Apolipoprotein E and renal disease

Apolipoprotein E (ApoE) is a major constituent of plasma lipoproteins with many biological actions of great significance. Beyond the known influence of ApoE polymorphisms on serum lipid profile, the pathogenesis of atherosclerosis, and the development of neurodegenerative disorders, ApoE also has a major role in the pathogenesis and progression of a variety of renal diseases, as well as in the atherosclerotic complications associated with them. Briefly, the polymorphisms of ApoE are major determinants of plasma lipid levels in uremic patients. They may affect the risk for cardiovascular disease in this population, predispose to the development of diabetic nephropathy, influence the severity of certain glomerulopathies, and regulate mesangial and glomerular functions locally in the kidney microenvironment. Finally, certain mutations of the ApoE gene are associated with a recently described nephropathy, termed lipoprotein glomerulopathy.

Lipoprotein glomerulopathy associated with psoriasis vulgaris: report of 2 cases with apolipoprotein E3/3

Lipoprotein glomerulopathy (LPG) is a rare disease, characterized by a special histology, including dilated glomerular capillaries filled with pale-stained and meshlike lipoprotein thrombi. It always presents with proteinuria or nephrotic syndrome. Although hyperlipidemia is not always seen, most patients have type III hyperlipoproteinemia with apolipoprotein (apo) E2/3 phenotyping. Although the clinical feature of LPG is rarely described, LPG associated with other glomerulopathy, including IgA nephropathy, membranous nephropathy, and lupus nephritis, has been documented. Until now, there have been no reports of psoriasis vulgaris associated with LPG. The authors present 2 cases of LPG with apo E3/3 genotyping associated with psoriasis vulgaris. The first patient was a 65-year-old woman who presented with nephrotic syndrome with daily urinary protein loss of 9.05 g and itchy erythematous scaly plaques on her trunk and lower limbs for 1 year. The renal biopsy results showed LPG, and the skin biopsy results showed psoriasis. The second patient was a 50-year-old man with history of psoriasis over his trunk and 4 limbs for 30 years. He also presented with nephrotic syndrome with daily urinary protein loss of 7.55 g. The renal biopsy results also showed LPG. The genotype of apo E showed E3/3, and lipoprotein electrophoresis showed a type III hyperlipoproteinemia-like pattern in both cases. The authors suggest that presence of apo E3/3 genotype cannot rule out the diagnosis of type III hyperlipoproteinemia and LPG. Besides, LPG should be included in the differential diagnosis of psoriatic patients with nephrotic syndrome, especially in Asian patients who show poor response to traditional therapy. Renal biopsy should be performed to make the definitive diagnosis.

Disappearance of intraglomerular lipoprotein thrombi and marked improvement of nephrotic syndrome by bezafibrate treatment in a patient with lipoprotein glomerulopathy

Lipoprotein glomerulopathy (LPG) is a hereditary disorder characterized by intraglomerular lipoprotein thrombi and increased serum apolipoprotein (apo) E. Patients with LPG usually manifest with nephrotic syndrome, and some progress to renal failure; however, no effective therapeutic regimen has been established for this disease. We experienced a patient with LPG for whom bezafibrate treatment was very effective. This 30-year-old Japanese woman had nephrotic syndrome and type III hyperlipoproteinemia. Renal biopsy showed markedly dilated capillary lumina containing massive lipoprotein thrombi. Plasma apo E concentration was elevated to twice that of normal controls. She was proved to be a heterozygote of apo E2 Kyoto (Arg25Cys). After 2 years treatment with bezafibrate (400 mg/day), her plasma albumin gradually increased from 2.1 to 4.0 mg/dl, and intraglomerular lipoprotein thrombi disappeared almost completely. Bezafibrate decreased plasma apo E and dramatically increased high density lipoprotein (HDL)-cholesterol. The decrease in apo E was observed mainly in the pre-beta-fraction, not in the alpha fraction. Lipidological analyses of our patient suggest that the origin her lipoprotein thrombi may be mainly from pre-beta-lipoproteins and that HDL might be involved in resolving lipoprotein thrombi. Our case suggests that administration of fibrates such as bezafibrate may be a novel therapeutic strategy for resolving intraglomerular thrombi and improving nephrotic syndrome in patients with LPG.

Renal injury in apolipoprotein E-deficient mice

Hyperlipidemia is thought to accelerate the progression of renal diseases, but the mechanisms by which hyperlipidemia exerts its deleterious effect is still poorly understood. The aim of this study was to describe the renal pathology in a hyperlipidemic mouse strain, the apolipoprotein E-deficient mice (apoE-/-). Renal specimens from a total of 34 mice were studied, including 19 apoE-/- females at the age of 36 weeks, 9 apoE-/- females at the age of 24 weeks, and 6 wild-type females (C57BL/6) as controls. Kidneys were evaluated by histologic examination, immunohistochemistry, and electron microscopy. Immunohistochemistry was used to detect MAC-2-expressing monocyte/macrophages, and the proliferation marker PCNA. Glomerular cell number, glomerular matrix area, and glomerular area were quantified by morphometry. Glomerular lesions in apoE-/- mice were characterized by macrophage accumulation, commonly with foam cell appearance, deposition of extracellular matrix, glomerular hyperplasia, and at times prominent mesangiolysis associated with capillary microaneurysms. Some cases demonstrated lipid deposits filling glomerular capillaries. Arterioles of the vascular pole demonstrated a "foamy" degeneration of smooth muscle cells. These lesions related to hyperlipidemia in this well-established mouse strain have not been previously described. Because this mouse strain is among the most widely studied for interventions aimed at altering hyperlipidemia and the progression of atherosclerosis, we believe that our observations may be of major importance for the accurate interpretation of interventional studies in this strain and offer a new opportunity to study mechanisms of hyperlipidemic renal injury.

Chronic graft-versus-host autoimmune disease in Fc receptor gamma chain-deficient mice results in lipoprotein glomerulopathy

Lipoprotein glomerulopathy (LPG) is a unique renal disease characterized by intraglomerular lipoprotein thrombi associated with severe proteinuria and frequent progression to renal failure. The histologic hallmark of LPG is the presence of laminated thrombi, consisting of lipid droplet, within the lumina of dilated glomerular capillaries. The findings of thrombi consisting of lipoproteins raised the possibilities that LPG might be related to a primary abnormality in lipid metabolism. However, the precise pathogenic basis of LPG remains unresolved. It was herein found that chronic graft-versus-host disease (GVHD) induced by the transfer of Ia-incompatible spleen cells from B6.C-H2(bm12) into coisogenic C57BL/6 mice with deficiency of Fc receptor gamma chain (FcRgamma) resulted in glomerulopathy that resembled LPG. The uptake of acetylated LDL was partially decreased in peritoneal macrophages isolated from FcRgamma-deficient mice compared with wild-type mice, suggesting that partial impairment of modified LDL uptake might contribute to the development of LPG associated with chronic GVHD in FcRgamma-deficient mice. LPG has been suggested to be a disorder of primary abnormality in lipid metabolism; these findings would therefore provide novel insight into the disease process.

Dyslipidemia in pediatric renal disease: epidemiology, pathophysiology, and management

Dyslipidemia increases the risk of cardiovascular events among individuals with renal disease, and there is a growing body of evidence that it hastens the progression of renal disease itself. Children with nephrotic syndrome or renal transplants have easily recognized hyperlipidemia. Among those with chronic renal insufficiency or end-stage renal disease, detection of dyslipidemia requires more careful analysis and knowledge of normal pediatric ranges. Disordered lipoprotein metabolism results from complex interactions among many factors, including the primary disease process, use of medications such as corticosteroids, the presence of malnutrition or obesity, and diet. The systematic treatment of dyslipidemia in children with chronic renal disease is controversial because conclusive data regarding the risks and benefits are lacking. Hepatic 3-methylglutaryl coenzyme A reductase inhibitors (statins), fibrates, plant stanols, bile acid-binding resins, and dietary manipulation are options for individualized treatment. Prospective investigations are required to guide clinical management.

A patient with apolipoprotein E2 variant (Q187E) without lipoprotein glomerulopathy

Four apolipoprotein (apo) E variants have been reported to be associated with lipoprotein glomerulopathy (LPG), which is characterized by type III hyperlipoproteinemia (type III HLP) and proteinuria and frequently leads to nephrotic syndrome. We report the histologic findings in the kidneys of a type III HLP patient with an apo E variant, apo E Toranomon, in which the glutamine at residue 187 in apo E is substituted by glutamic acid (Q187E). The patient also had type 2 diabetes mellitus. No evidence of lipoprotein thrombi suggestive of LPG was detected, however, and the histologic diagnosis was diabetic nephrosclerosis. This unique case illustrates that not all apo E variants result in LPG, and the location of mutations in the apo E protein is one of the important determinants for the development of LPG.

Etiological significance of apolipoprotein E mutations in lipoprotein glomerulopathy

Lipoprotein glomerulopathy (LPG) is a newly recognized renal disease characterized by thrombus-like lipoproteins in the glomerular capillaries and abnormal lipoprotein profiles similar to those in type III hyperlipoproteinemia. Recently, these conditions have been shown to be associated with some apolipoprotein E (apoE) mutations. We found an apoE mutation (designated apoE-Sendai) that substitutes arginine 145 with proline. This mutation occurs most frequently in Japanese patients with LPG. To elucidate the etiological role of this mutation in the apoE gene, we established an experimental model for LPG by transducing apoE-Sendai in apoE knockout mice with the use of an adenovirus vector. Based on the findings in patients with LPG and its animal model, we suggest that the glomerular lesions are not only caused by hyperlipidemia, but also by in situ interaction between lipoprotein-containing mutant apoE with the glomerulus. In this review, we outline the clinical features of LPG and discuss the relationship between apoE mutations and LPG.

Diminished LDL receptor and high heparin binding of apolipoprotein E2 Sendai associated with lipoprotein glomerulopathy

Variants of apolipoprotein E (apoE) have been linked to lipoprotein glomerulopathy, a new glomerular disease characterized by the deposition of lipoproteins in mesangial capillaries. One third of affected patients are heterozygous for apoE2 Sendai (Arg(145) Pro). Variants of apoE can also produce type III hyperlipoproteinemia (HLP). Recessive type III HLP is caused by apoE2 (Arg(158) Cys), a mutant with diminished low-density lipoprotein (LDL) receptor binding but halfnormal heparin binding. Dominant type III HLP is caused by mutations that markedly alter heparin binding but modestly reduce receptor binding. This study examined whether apoE2 Sendai (Arg(145) Pro) was functionally different from type III HLP-producing apoE variants by expressing apoE3, apoE2 (Arg(158) Cys), apoE1 (Arg(146) Glu), a dominant apoE variant, and apoE2 Sendai (Arg(145) Pro) in the baculovirus system. LDL receptor binding was studied using recombinant apoE complexed to phospholipid vesicles and to very lowdensity lipoprotein from a patient with familiar apoE deficiency. Compared with apoE3, receptor-binding activities of apoE2 (Arg(158) Cys), apoE1 (Arg(146) Glu), and apoE2 Sendai (Arg(145) Pro) all were less than 5%. Heparin-binding activities were 53%, 23%, and 66%, respectively, of apoE3. The distribution of apoE2 Sendai among the major plasma lipoprotein fractions was similar to that of apoE3 and apoE2 (Arg(158) Cys). ApoE2 Sendai (Arg(145) Pro) represents the only known mutation within the heparin-binding domain of apoE (residues 142 through 147), revealing diminished receptor binding and almost normal heparin binding. These unique characteristics of apoE2 Sendai (Arg(145) Pro) may relate to the development of lipoprotein glomerulopathy.

Virus-mediated transduction of apolipoprotein E (ApoE)-sendai develops lipoprotein glomerulopathy in ApoE-deficient mice

Lipoprotein glomerulopathy (LPG) is a unique renal disease characterized by thrombus-like substances in markedly dilated glomerular capillaries, dysbetalipoproteinemia, and elevated plasma concentrations of apoE. Recent studies identified several apoE mutations in patients with LPG, including apoE2(R145P) Sendai (apoE-Sendai). Virus-mediated transduction of apoE-Sendai in apoE-deficient hypercholesterolemic mice resulted in insufficient correction of hypercholesterolemia and a marked and temporal induction of plasma triglyceride levels. In vitro binding studies showed that apoE-Sendai has a reduced affinity for the low density lipoprotein receptor, suggesting that dysbetalipoproteinemia in LPG is caused by the apoE mutation. Furthermore, histological examination revealed marked intraglomerular depositions of apoE-containing lipoproteins in mice injected with apoE-Sendai virus. These LPG-like depositions were detected 6 days after virus injection and were sustained for at least 60 days. Our results demonstrated that apoE-Sendai is an etiological cause of LPG.