Lipoprotein glomerulopathy treated with LDL-apheresis (Heparin-induced Extracorporeal Lipoprotein Precipitation system): a case report

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.

Lipoprotein Glomerulopathy, First Case Report from Canada

Lipoprotein glomerulopathy (LPG) is caused by a mutation in the apolipoprotein E gene (APOE) gene and is characterized by lipoprotein thrombi in glomerular capillaries. Here, we describe a case of LPG, the first to be reported from Canada and the first case of LPG in North America to be associated with the APOE Tokyo/Maebashi mutation (p.Leu162_Lys164del, traditional nomenclature 142_144del). A 49-year-old man of Chinese descent with a previous diagnosis of dyslipidemia and a new diagnosis of hypertension was found to have proteinuria on routine urinalysis. Renal biopsy showed markedly dilated glomerular capillaries filled with pale staining mesh-like material that stained positive for Oil-Red-O, consistent with lipoprotein thrombi. APOE gene sequencing confirmed the diagnosis of LPG. The patient was treated with fenofibrate and perindopril. His lipid profile normalized and proteinuria dropped to minimal levels. Repeat renal biopsy 2 years after the first showed resolution of lipoprotein thrombi but with rare residual granular densities by electron microscopy consistent with lipoprotein in the subendothelial space, supporting the hypothesis that this subendothelial material contains precursors to lipoprotein thrombi.

An Updated Review and Meta Analysis of Lipoprotein Glomerulopathy

More than 200 cases of lipoprotein glomerulopathy (LPG) have been reported since it was first discovered 30 years ago. Although relatively rare, LPG is clinically an important cause of nephrotic syndrome and end-stage renal disease. Mutations in the APOE gene are the leading cause of LPG. APOE mutations are an important determinant of lipid profiles and cardiovascular health in the population and can precipitate dysbetalipoproteinemia and glomerulopathy. Apolipoprotein E-related glomerular disorders include APOE2 homozygote glomerulopathy and LPG with heterozygous APOE mutations. In recent years, there has been a rapid increase in the number of LPG case reports and some progress in research into the mechanism and animal models of LPG. We consequently need to update recent epidemiological studies and the molecular mechanisms of LPG. This endeavor may help us not only to diagnose and treat LPG in a more personized manner but also to better understand the potential relationship between lipids and the kidney.

A novel apolipoprotein E mutation, ApoE Ganzhou (Arg43Cys), in a Chinese son and his father with lipoprotein glomerulopathy: two case reports

Background

Lipoprotein glomerulopathy is a rare and newly recognized glomerular disease that can lead to kidney failure. Its pathological features include the presence of lipoprotein embolus in the loop cavity of glomerular capillaries. It is believed that apolipoprotein E gene mutation is the initiator of the disease. Since the discovery of lipoprotein glomerulopathy, 16 different apolipoprotein E mutations have been reported worldwide, but most of these cases are sporadic. Here we report two cases of lipoprotein glomerulopathy, a Chinese son and his father, with a novel apolipoprotein E mutation, ApoE Ganzhou (Arg43Cys).

Case presentation

Case 1, a 33-year-old Chinese man, was hospitalized on 3 March 2014 owing to edema and weakness of facial and lower limbs for 1 month. Laboratory data showed urine protein 3+, hematuria 2+, serum creatinine 203 μmol/L, uric acid 670 μmol/L, total cholesterol 12.91 mmol/L, triglyceride 5.61 mmol/L, high-density lipoprotein 1.3 mmol/L, low-density lipoprotein 7.24 mmol/L, apolipoprotein B 2.48 g/L, and lipid protein (a) 571 mg/L. Renal tissue examined by immunofluorescence and electron microscopy indicated lipoprotein glomerulopathy. Case 2, 55-year-old father of case 1, was hospitalized on 12 January 2016 owing to edema of his lower extremities for 6 months. Laboratory data showed urine protein 2+, hematuria 2+, serum creatinine 95 μmol/L, uric acid 440 μmol/L, total cholesterol 4.97 mmol/L, triglyceride 1.91 mmol/L, high-density lipoprotein 1.18 mmol/L, low-density lipoprotein 3.12 mmol/L, apolipoprotein B 2.48 g/L, and lipid protein (a) 196 mg/L. Renal tissue examined by immunofluorescence and electron microscopy indicated lipoprotein glomerulopathy. Apolipoprotein E mutation test showed that they had the same gene mutation, a novel type of apolipoprotein E mutation.

Based on their clinical presentation and examination findings, they were diagnosed with lipoprotein glomerulopathy. Case 1 was treated with prednisone and dual plasma replacement, followed by simvastatin, nifedipine, triptolide, and angiotensin II receptor blocker drug therapy. After 1 month, the edema symptoms of the patient were alleviated, and urinary protein, serum creatinine, and uric acid were quantitatively reduced. Case 2 was treated with Tripterygium wilfordii and angiotensin II receptor blocker drugs for 3 weeks, and his edema symptoms were alleviated, and urinary protein, serum creatinine, and uric acid were quantitatively reduced.

Conclusions

The apolipoprotein E mutation in the two cases we reported was a familial aggregation phenomenon, and the mutation is a novel type, which we named ApoE Ganzhou (Arg43Cys). The location of the gene mutation is close to the most common mutation type of lipoprotein glomerulopathy, ApoE Kyoto (Arg25Cys), so we speculate that its pathogenic role might be the similar to that of ApoE Kyoto (Arg25Cys).

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.

A novel apolipoprotein E mutation caused by a five amino acid deletion in a Chinese family with lipoprotein glomerulopathy: a case report

BACKGROUND

Lipoprotein glomerulopathy (LPG) is a rare kidney disease with a poor prognosis that is related to mutation of the apoE gene. More than 10 variants of apoE associated with LPG have currently been identified.

CASE PRESENTATION

A male and his mother presented with proteinuria during a health examination. They went to hospital for further examination. Renal biopsy was performed, and the diagnosis was lipoprotein glomerulopathy (LPG), which is a rare, inherited renal disease. Medical histories were collected from the 2 LPG patients and their family members. The patients and family members underwent a routine urine test, and their renal function, blood lipids, and lipoprotein levels were examined. Genomic DNA was extracted from the peripheral blood of 7 family members, and exon 2, exon 3 and exon 4 of apoE were amplified by polymerase chain reaction (PCR). The purified PCR products were sequenced. Sequence analysis identified a 15 bp deletion (GCGCAAGCTGCGTAA) in exon 4 of the apoE gene that results in a novel 5 amino acid deletion in apoE (143 K-147R → 0). No mutations were found in exon 2 and exon 3 of the apoE gene.

CONCLUSIONS

This family study suggests that a novel ApoE mutation (143 K-147R → 0) may be etiologically related to LPG, and other genetic or environmental factors may be associated with the occurrence of 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.

Five-year follow-up of a case of lipoprotein glomerulopathy with APOE Kyoto mutation

We report the case of a 34-year-old Japanese male with lipoprotein glomerulopathy (LPG). Renal biopsy showed LPG, and followed by a genetic analysis revealed a mutation in apolipoprotein E gene (APOE Kyoto; Arg25Cys). We started treatment with probucol, bezafibrate, losartan, and allopurinol. Urinary protein decreased in response to treatment but has remained at about 1.27 ± 0.71 g/gCr, and a repeat biopsy which was performed 1 year after the first biopsy showed no clear evidence of pathological remission and complication of other glomerular disease. After 5 years of follow-up after the start of treatment, renal function has almost maintained without apparent deterioration. Interestingly, the course of the urinary protein level closely paralleled his triglyceride and cholesterol levels in a long-term. This observation suggests the importance of tight control of lipid profiles as a means of renoprotection in LPG patient.

Lipoprotein glomerulopathy associated with a mutation in apolipoprotein e

Lipoprotein glomerulopathy is a pathological condition characterized by lipid accumulation in the glomerular capillaries that has been associated with the presence of rare mutants of apolipoprotein E (ApoE). We describe a 51-year-old Italian patient presenting Type III hyperlipidemia and proteinuria in whom renal biopsy showed capillary ectasia and intraluminal lipid deposits, suggesting the diagnosis of lipoprotein glomerulopathy. The patient, who had elevated plasma ApoE level, was found to be heterozygous for a mutation in ApoE (Arg150Cys), designated apoE_MODENA. This mutation induces the formation of ApoE dimers that are detectable under non-reducing conditions. Treatment with hypolipidemic drugs did not result in a complete remission of the proteinuria and was accompanied by a slow but progressive worsening of renal function with the persistence of intracapillary lipid thrombi. The introduction of low-density lipoprotein aphaeresis combined with a more aggressive lipid lowering and antihypertensive therapy resulted in the remission of proteinuria and a substantial improvement of renal function. Switching from low-density lipoprotein aphaeresis to plasma filtration did not result in an equivalent control of renal damage. The patient died of intracranial hemorrhage during an acute episode of malignant hypertension.

Relationship between apolipoprotein E gene polymorphism and total cholesterol level in patients with kidney diseases

AIM: To evaluate the association between apolipoprotein E (apoE) gene polymorphism and total cholesterol (TC) level in patients with kidney diseases.

METHODS: A predefined literature search was performed to collect data from the electronic databases of PubMed, Embase and the Cochrane Library and eligible relevant studies reporting the association of apoE gene polymorphism with TC level in patients with kidney diseases were recruited for meta-analysis.

RESULTS: Twenty-one studies were identified for the analysis of association between apoE gene polymorphism and TC level in patients with kidney disease. Subjects with E3E4 had a higher TC than those with E3E3 [weighted mean differences (WMD) = 2.14, P = 0.01] and subjects with E2E3 had a lower TC than those with E3E3 (WMD = -1.93, P = 0.01). Subjects with ε2 had a lower TC than those with ε3 (ε2 vs ε3: WMD = -1.23, P = 0.002; ε2 vs ε4: WMD = -2.77, P ﹤0.0001) and subjects with 3 had a lower TC than those with 4 (WMD = -0.79, P = 0.03).

CONCLUSION: Subjects with apoE E3E4 and ε4 had a higher TC level and subjects with apoE E2E3 and ε2 had a higher TC level in patients with kidney disease. However, more well-designed studies should be performed in the future to confirm these findings.

A possible structural basis behind the pathogenic role of apolipoprotein E hereditary mutations associated with lipoprotein glomerulopathy

Single amino acid mutations in apolipoprotein E (apoE) have been associated with the development of the rare kidney disease lipoprotein glomerulopathy (LPG). Although the genetic linkage to disease development is well established, the mechanism of pathogenesis is largely unknown, limiting therapeutic insight. Here, we summarize current knowledge in the field and focus on the possible effects of LPG-associated mutations on the structure of apoE. Recent findings have suggested that mutation-induced folding perturbations in apoE lead to structural destabilization and aggregation, effects that may underlie lipoprotein thrombi accumulation in the glomerulus, a hallmark of LPG. The recognition that structural destabilization may underlie the association between apoE mutations and LPG can be key for development of new innovative treatments for this rare disease.

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.

A case of lipoprotein glomerulopathy with thrombotic microangiopathy due to malignant hypertension

BACKGROUND

Lipoprotein glomerulopathy (LPG) is a rare inherited renal disease characterized by intraglomerular lipoprotein within the lumina of severely dilated glomerular capillaries. The common clinical presentation of LPG includes proteinuria or nephrotic syndrome. Hypertension and anemia were thought to be mild in LPG. Thrombotic microangiopathy (TMA) in LPG has not been previously reported. In this report, we present a patient with LPG that developed TMA. To the best of our knowledge, this is the first report of TMA in LPG.

CASE PRESENTATION

Four years ago (2005), a 19-year-old Chinese woman was diagnosed with nephrotic syndrome and provided prednisone treatment. A combination of prednisone and cyclophosphamide did not have any effect and was discontinued after six months. Although she was steroid-resistant, over the next subsequent three years, she maintained normal renal function without anemia and thrombocytopenia. In February 2009, she had a severe headache and blurry vision and presented at a local hospital with severe hypertension. Blood pressure was 220/160 mmHg. Laboratory data showed hemoglobin 3.8 g/dL; platelet counts 29 × 10(9)/L; urinary protein 7.90 g/d; total bilirubin 29.9 umol/L; indirect bilirubin 28.2 umol/L; LDH 1172 U/L; ALB 2.66 g/dL; urea nitrogen 52 mg/dL; serum creatinine 3.2 mg/dL; triglyceride 25  mg/dL; total cholesterol 273 mg/dL. ANA, ds-DNA, ANCA, anti-GBM antibody and anticardiolipin were all negative. A renal biopsy revealed LPG with TMA. Genetic evaluation showed the patient carried the APOE Kyoto mutation. Adequate control of blood pressure improved microangiopathic anemia and thrombocytopenia, however, renal function did not improve and she eventually developed uremia and became hemodialysis dependent.

CONCLUSION

We report on a rare case of TMA probably due to malignant hypertension in LPG. Early lipid-lowering and antihypertensive treatment may improve outcome. The pathophysiologic relationship between LPG and TMA should be investigated further.

A founder haplotype of APOE-Sendai mutation associated with lipoprotein glomerulopathy

Lipoprotein glomerulopathy (LPG) is a hereditary disease characterized by lipoprotein thrombi in the glomerulus, hyperlipoproteinemia, and a marked increase in serum apolipoprotein E (APOE). More than 12 APOE mutations have been identified as causes of LPG, and APOE-Sendai (Arg145Pro) mutation was frequently detected in patients from the eastern part of Japan including Yamagata prefecture. Recently, effective therapy with intensive lipid-lowering agents was established, and epidemiologic data are required for early diagnosis. We determined the haplotype structure of APOE-Sendai in 13 patients from 9 unrelated families with LPG, and found that the haplotype of all APOE-Sendai mutations was identical, suggesting that APOE-Sendai mutation is common in Japanese patients probably through a founder effect. We also studied the gene frequency of APOE-Sendai in 2023 control subjects and 418 patients receiving hemodialysis in Yamagata prefecture using the TaqMan method, but did not identify any subjects carrying the mutation, indicating that it is very rare in the general population even in the eastern part of Japan. In addition to APOE mutation, other genetic and/or epigenetic factors are considered to be involved in the pathogenesis of LPG because of its low penetrance. The patients did not have a common haplotype of the counterpart APOE allele, and some patients had the same haplotype of the counterpart APOE allele as the asymptomatic carriers. These results suggest that the counterpart APOE allele is not likely associated with the onset of LPG. Further study is required to clarify the pathogenesis of LPG.

All-trans retinoic acid can regulate the expressions of gelatinases and apolipoprotein E in glomerulosclerosis rats

Apolipoprotein E (apoE) is an important plasma protein in cholesterol homeostasis and plays a key role in the pathogenesis of glomerulosclerosis (GS). Gelatinases include matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). The abnormal expressions of gelatinases are implicated in the pathogenesis of extracellular matrix accumulation. All-trans retinoic acid (ATRA) is an import biological agent which can play a protective role against GS. We performed this investigation to explore whether ATRA could regulate the expressions of gelatinases and apoE in the glomerulus of GS rats. 120 Wistar rats were randomly divided into three groups: sham operation group (SHO), glomerulosclerosis model group without treatment (GS) and GS model group treated with ATRA (GA). The GS disease was established by uninephrectomy and adriamycin injection. At the end of 9 and 13 weeks, the relevant samples were collected and determined. Compared with GS group at 9/13 weeks, values of 24-hour urine total protein, 24-hour urine excretion for albumin, blood urea nitrogen, serum creatinine and glomerulosclerosis index, and protein expressions of apoE, transforming growth factor-βl (TGF-β1), α-smooth muscle actin, collagen-IV and fibronectin in glomerulus and mRNA expressions of apoE and TGF-β1 in renal tissue were significantly down-regulated by ATRA (each P<0.01). However, the expressions of MMP-2 and MMP-9 (mRNA, protein and activity) were enhanced in GA group than those in GS group. In conclusion, gelatinases are associated with apoE expression, and ATRA can increase the gelatinases expressions and reduce the accumulation of apoE in glomerulus of GS rats, but the detailed mechanism needs to be elucidated in the future.

Lipoprotein glomerulopathy

PURPOSE OF REVIEW

Lipoprotein glomerulopathy is a rare disorder characterized by proteinuria, renal insufficiency and disturbances in lipoprotein metabolism closely related to those observed in type III hyperlipidemia. Rare mutations in apolipoprotein E (apoE) gene may contribute to the pathogenesis of the disease. This article reviews the clinical and laboratory features of lipoprotein glomerulopathy, discusses the mechanisms that may be implicated in its pathogenesis and summarizes the currently available therapeutic options.

RECENT FINDINGS

During the past years two new apoE gene mutations were described in Caucasian patients, apoE Modena (Arg150→Cys) and apoE Las Vegas (Ala152→Asp), a finding indicating that the disease may be more common in white populations than initially thought. Results from case studies suggest that fibrates improve renal pathology and may result in the complete clinical remission of the disease. LDL-apheresis or immunoadsorption onto staphylococcal protein A may also have a role in refractory cases.

SUMMARY

Lipid glomerulopathy is a rare, poorly understood disorder with potentially detrimental consequences. The determination of the effects of apoE mutations on the structural and functional characteristics of the mature protein may provide new insights in the pathogenesis of the disease. Meanwhile, intensive lipid-lowering may reduce proteinuria and preserve renal function in this patient group.

apoE expression in glomerulus and correlation with glomerulosclerosis induced by adriamycin in rats

Lipid deposition in glomerulus plays an important role in the progression of glomerulosclerosis (GS), and apolipoprotein E (apoE) is an important protein in cholesterol homeostasis. This investigation was performed to explore whether there exists an association between apoE and GS susceptibility. Eighty Wistar rats were randomly divided into two groups: sham operation group and glomerulosclerosis model group, n = 40. The GS disease in rat was induced by uninephrectomy and injecting adriamycin (5 mg/kg) through the tail vein. At the end of 9 and 13 weeks, 20 rats in each group were killed and the relative samples were collected. Serum creatinine, blood urea nitrogen, and 24-h urine protein were determined. Immunohistochemical analysis was performed on renal tissue to detect the expression of apoE, collagen IV, fibronectin, α-smooth muscle actin, and transforming growth factor-β1 in glomerulus. Real-time reverse transcription polymerase chain reaction was conducted to detect the apoE mRNA expression in renal tissue. Compared with sham operation group at the end of 9/13 weeks, glomerulosclerosis model group exhibited levels of serum creatinine, blood urea nitrogen, 24-h urine protein, and a glomerulosclerosis index that were significantly elevated ( p < 0.01), and collagen IV, fibronectin, α-smooth muscle actin, and transforming growth factor-β1 protein expression and apoE expression (protein and mRNA) were significantly upregulated (p < 0.01). In conclusion, apoE can increase the accumulation of extracellular matrix in glomerulus and may take part in the progression of GS.

All-trans retinoic acid regulates the expression of apolipoprotein E in rats with glomerulosclerosis induced by Adriamycin

Apolipoprotein E (apoE) is an important plasma protein in cholesterol homeostasis and plays a key role in the progression of glomerulosclerosis (GS). We conducted this investigation to explore whether all-trans retinoic acid (ATRA) could regulate the apoE expression in the pathological process of GS. 120 Wistar rats were divided into three groups at random: sham operation group (SHO), glomerulosclerosis model group without treatment (GS), GS model group treated with ATRA (GA); n=40, respectively. The disease of GS in rat was established by uninephrectomy and adriamycin (5mg/kg) injection. At the end of 9 and 13 weeks, 20 rats in each group were killed and the relevant samples were collected. 24-hour urine total protein (24UTP), 24-hour urine excretion for albumin (24Ualb), serum total protein (TP) and serum albumin (Alb), blood urea nitrogen (BUN), serum creatinine (Scr), total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), serum and urine apoE and glomerulosclerosis index (GSI) were measured. The protein expressions of collagen IV (Col-IV), fibronectin (FN) and apoE in glomeruli were determined by immunohistochemistry. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR) was used to detect the expression of apoE mRNA in kidney. TP and Alb in GA group in 9/13-week were increased than those of GS group, however, the differences were not statistically significant. Compared with group GS at 9/13 weeks, values of 24UTP, 24Ualb, BUN, Scr, TC, TG, HDL, LDL, serum and urine apoE, and GSI in GA group that were significantly reduced, and protein expressions of Col-IV, FN and apoE in glomeruli and expression of apoE mRNA in renal tissue were significantly down-regulated by ATRA (P<0.01). In conclusion, ATRA can regulate the expression of apoE, reduce the accumulation of extracellular matrix (ECM) and step down the progression of GS.

Effect of heparin-induced extracorporeal lipoprotein apheresis on renal function

During the course of heparin-induced extracorporeal lipoprotein apheresis, a patient with no prior known renal impairment or proteinuria demonstrated sustained improvement in estimated glomerular filtration rate, commensurate with reduction in serum lipids and creatine phosphokinase levels. Causes and implications of this observation, which was not a priori, are discussed.