Hypoalbuminemia and proteinuria contribute separately to reduced lipoprotein catabolism in the nephrotic syndrome

A Risk Prediction Model for New-Onset Chronic Kidney Disease in the Elderly

INTRODUCTION

Worsening renal function poses a significant health risk to elderly individuals. This study aimed to construct a simple risk prediction model for new-onset chronic kidney disease (CKD) among elderly populations.

METHODS

In this retrospective cohort study, 5,416 elderly residents (aged ≥65 years) who underwent physical examinations as part of the National Basic Public Health Service project at least twice between January 2017 and July 2021 were included. The endpoint was new-onset CKD, defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 during the follow-up period. Predictors of new-onset CKD were selected using multivariable Cox regression and a stepwise approach. A risk prediction model based on the selected predictors was constructed and evaluated using the concordance index (C-index) and area under curve (AUC). External validation was conducted to verify the model's performance.

RESULTS

During the median follow-up period of 2.3 years, the incident of new-onset CKD was 20.1% (n = 1,088). Age, female gender, diabetes, elevated triglyceride levels, and baseline eGFR were selected as predictors. The model demonstrated good predictive performance across the cohort, with a C-index of 0.802. The AUCs for 2-year, 3-year, and 4-year predictions were 0.831, 0.829, and 0.839, respectively. External validation confirmed the model's efficacy, with a 2-year AUC of 0.735.

CONCLUSION

This study developed a simple yet effective risk prediction model for new-onset CKD among elderly populations. The model facilitates prompt identification of elderly individuals at risk of renal function decline in primary care, enabling timely interventions.

Dyslipidemia in children with chronic kidney disease-findings from the Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study

BACKGROUND

Dyslipidemia is an important and modifiable risk factor for CVD in children with CKD.

METHODS

In a cross-sectional study of baseline serum lipid levels in a large prospective cohort study of children with stage 3-5 (predialysis) CKD, frequencies of abnormal lipid levels and types of dyslipidemia were analyzed in the entire cohort and in subpopulations defined by fasting status or by the presence of nephrotic range proteinuria. Associated clinical and laboratory characteristics were determined by multivariable linear regression analysis.

RESULTS

A total of 681 patients aged 12.2 ± 3.3 years with a mean eGFR of 26.9 ± 11.6 ml/min/1.73 m2 were included. Kidney diagnosis was classified as CAKUT in 69%, glomerulopathy in 8.4%, and other disorders in 22.6% of patients. Nephrotic range proteinuria (defined by a urinary albumin/creatinine ratio > 1.1 g/g) was present in 26.9%. Dyslipidemia was found in 71.8%, and high triglyceride (TG) levels were the most common abnormality (54.7%). Fasting status (38.9%) had no effect on dyslipidemia status. Except for a significant increase in TG in more advanced CKD, lipid levels and frequencies of dyslipidemia were not significantly different between CKD stages. Hypertriglyceridemia was associated with younger age, lower eGFR, shorter duration of CKD, higher body mass index (BMI-SDS), lower serum albumin, and higher diastolic blood pressure.

CONCLUSIONS

Dyslipidemia involving all lipid fractions, but mainly TG, is present in the majority of patients with CKD irrespective of CKD stage or fasting status and is significantly associated with other cardiovascular risk factors.

Analysis of the association of NPHS2 and ACTN4 genes polymorphism with nephrotic syndrome in Egyptian children

BACKGROUND

One of the most common kidney illnesses in developing countries is pediatric nephrotic syndrome (PNS), which is frequently associated with dyslipidemia and edema. The rapid discovery of genes related to NS has aided in the understanding of the molecular mechanics of glomerular filtration. The goal of this study is to determine the relationship between NPHS2 and ACTN4 in PNS youngsters.

METHODS

A study with 100 NS children and 100 healthy matched volunteers was conducted. Genomic DNA was extracted from peripheral blood. Single-nucleotide polymorphisms were genotyped using ARMS-PCR.

RESULTS

A substantial decline in the level of albumin was found in NS cases (P < 0.001) Further on, a significantly difference in T.C and TG level between healthy and NS patient. Molecular study showed a highly significant difference of NS patients from controls regarding NPHS2 rs3829795 polymorphic genotypes as the GA heterozygous genotype shows highly significant difference from controls (P < 0.001) as well as GA + AA genotypes (P < 0.001) in comparison with GG genotype. Regarding rs2274625, The GA heterozygous genotype showed no statistically significant difference between genotypes and alleles with NS (P = 0.246). Association of AG haplotype NPHS2 rs3829795-rs2274625 haplotypes found a significant association with the risk of developing NS (P = 0.008). Concerning the ACTN4 rs121908415 SNP, there was no link between this mutation and NS children.

CONCLUSION

The correlation of AG haplotype NPHS2 rs3829795-rs2274625 haplotypes identified a strong association with the likelihood of getting NS, according to our findings. There was no connection found between the ACTN4 rs121908415 SNP and NS children.

Does pathological type of primary nephrotic syndrome affect serum concentrations of proprotein convertase subtilisin/kexin type 9?

Background

Dyslipidemia is a common finding in primary nephrotic syndrome (PNS). Serum PCSK9 level is also increased in PNS and is the main cause of dyslipidemia in such patients. There is a paucity of data on the relation between dyslipidemia and pathological types of PNS. We hypothesized that severity of dyslipidemia varies across different types of PNS, and this variation is due to differences in serum PCSK9 levels.

Methods

Fifty patients recently diagnosed with PNS were included in this cross-sectional study. Serum PCSK9, albumin, creatinine, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol (VLDL-C), triglycerides (TG), and 24-h urine protein were measured. Comparison of patients’ characteristics between pathological types of PNS and correlations between serum PCSK9 and other parameters were assessed.

Results

Serum PCSK9 levels were significantly higher in PNS patients compared with healthy individuals (314.58 ± 73.83 vs 253.42 ± 36.66 ng/ml, p < 0.001). No differences found between PNS types regarding serum levels of PCSK9 (p = 0.571), TC (p = 0.806), LDL-C (p = 0.950), HDL-C (p = 0.844), VLDL-C (p = 0.472), and TG (p = 0.969). Serum PCSK9 levels correlated significantly with TC (p < 0.001), LDL-C (p < 0.001), HDL-C (p = 0.003), VLDL-C (p = 0.008), TG (p = 0.005), 24-h urine protein (p = 0.005), and male sex (p = 0.014).

Conclusion

The pathological type of PNS does not affect serum levels of PCSK9 and components of lipid profile.

Clinical Efficacy of Persian Medicine Diet Combined with Western Medicine-Based Diet on Proteinuria in Pediatric Nephrotic Syndrome: A Randomized Controlled Clinical Trial

Introduction

Nephrotic syndrome (NS) is a common chronic kidney disorder during childhood. The most important characteristic of this disease is proteinuria. The Persian medicine (PM) has important dietary recommendations for strengthening the kidney function and treatment of this disease. The aim of this study was to investigate the effect of a diet including PM recommendations and general principles of Western medicine.

Materials and Methods

Twenty children with nephrotic syndrome were randomly divided into intervention and control groups and monitored for one month. The control group received a diet based on the general principles of Western medicine. In the intervention group, in addition to the Western medicine diet, dietary recommendations of PM were also prescribed including the pomegranate (Cydonia oblonga mill.), quince (Cydonia oblonga mill.), and whole grains (wheat and barley). A 24-hour dietary questionnaire was applied and anthropometric and biochemical indices including spot urine protein (proteinuria), albumin (Alb), urea, creatinine (Cr), total cholesterol (TC), and triglyceride (TG) were measured before and after the study.

Results

The amount of protein intake reduced significantly in the diet of both groups but the differences between the two groups were not significant. Proteinuria reduced significantly in both the Western and PM groups; however, proteinuria was significantly lower in the Persian medicine group compared to the control group. TC and Cr levels reduced significantly in the intervention group, although the changes were not significant compared to the control group.

Conclusion

The results of this study showed that adding dietary recommendations of the Persian medicine to the general rules of the Western medicine diet reduced proteinuria and improved the combat against nephrotic syndrome.

Albumin is an interface between blood plasma and cell membrane, and not just a sponge

Albumin is the most abundant protein in blood plasma and acts as a carrier for many circulating molecules. Hypoalbuminaemia, mostly caused by either renal or liver disease or malnutrition, can perturb vascular homeostasis and is involved in the development of multiple diseases. Here we review four functions of albumin and the consequences of hypoalbuminaemia on vascular homeostasis. (i) Albumin is the main determinant of plasma colloid osmotic pressure. Hypoalbuminaemia was therefore thought to be the main mechanism for oedema in nephrotic syndrome (NS), however, experimental studies showed that intrarenal mechanisms rather than hypoalbuminaemia determine formation and, in particular, maintenance of oedema. (ii) Albumin functions as an interface between lysophosphatidylcholine (LPC) and circulating factors (lipoproteins and erythrocytes) and the endothelium. Consequently, hypoalbuminaemia results in higher LPC levels in lipoproteins and erythrocyte membrane, thereby increasing atherosclerotic properties of low-density lipoprotein and blood viscosity, respectively. Furthermore, albumin dose-dependently restores LPC-induced inhibition of vasodilation. (iii) Hypoalbuminaemia impacts on vascular nitric oxide (NO) signalling by directly increasing NO production in endothelial cells, leading to reduced NO sensitivity of vascular smooth muscle cells. (iv) Lastly, albumin binds free fatty acids (FFAs). FFAs can induce vascular smooth muscle cell apoptosis, uncouple endothelial NO synthase and decrease endothelium-dependent vasodilation. Unbound FFAs can increase the formation of reactive oxygen species by mitochondrial uncoupling in multiple cell types and induce hypertriglyceridemia in NS. In conclusion, albumin acts as an interface in the circulation and hypoalbuminaemia impairs multiple aspects of vascular function that may underlie the association of hypoalbuminaemia with adverse outcomes. However, hypoalbuminaemia is not a key to oedema in NS. These insights have therapeutic implications.

Infections and risk of end-stage renal disease in patients with nephrotic syndrome: a nationwide population-based case-control study

Background

Infections are a major cause of morbidity in patients with nephrotic syndrome (NS); however, the risk of infections in NS and its subsequent effect on adverse renal outcomes are not well established.

Methods

From 2000–2013 claims data, 4,856 patients with NS were identified from the Taiwanese National Health Insurance Research Database (NHIRD). In the study group, 554 patients progressing to end-stage renal disease (ESRD), as identified during follow-up, were enrolled. In the control group, two patients with NS without progression to ESRD, during the same period, matched with one patient from the study group were included. The correlation between rates of infections and risk of ESRD in patients with NS was estimated using conditional logistic regression analysis.

Results

The proportion of outpatient visits for infections in patients with NS with and without progression to ESRD was 61.2% and 32.8%, respectively, and the proportion of hospitalization due to infections was 28.9% and 1.7%, respectively. The risk of ESRD was higher in patients with frequent outpatient visits for infections (>10 outpatient visits), with a relative risk of 3.20 [95% confidence interval (CI), 1.84–5.57]. Additionally, a significant association was found between severe infections requiring hospitalization and ESRD, with a relative risk of 7.01 (95% CI, 3.65–13.44). Subgroup analysis stratified by sex or age indicated that the risk associated with ESRD was significantly higher in female and elderly patients with NS.

Conclusions

The risk of ESRD in patients with NS was linked to the incidence of infection, especially those requiring hospitalization due to more severe bacterial infections. Implications of study results are important for clinicians who should be aware of the possibility of ESRD development in patients with NS with infectious complications.

Pathogenesis and Management of Acute Kidney Injury in Patients with Nephrotic Syndrome Due to Primary Glomerulopathies

Acute kidney injury in the context of nephrotic syndrome is a serious and alarming clinical problem. Largely, acute kidney injury is a relatively frequent complication among patients with comorbidities while it has been independently associated with an increased risk of adverse outcomes, including death and chronic kidney disease. Nephrotic syndrome, without hematuria or with minimal hematuria, includes a list of certain glomerulopathies; minimal change disease, focal segmental glomerulosclerosis and membranous nephropathy. In the light of primary nephrotic syndrome, pathophysiology of acute kidney injury is differentiated by the nature of the primary disease and the severity of the nephrotic state. This review aims to explore the clinical circumstances and pathogenetic mechanisms of acute kidney injury in patients with nephrotic syndrome due to primary glomerulopathies, focusing on newer perceptions regarding the pathogenesis and management of this complicated condition, for the prompt recognition and timely initiation of appropriate treatment in order to restore renal function to its baseline level. Prompt recognition of the precise cause of acute kidney injury is crucial for renal recovery. Clinical characteristics, laboratory and serological findings along with histopathological findings, if required, will reveal the implicated pathway leading to individualized approach and management.

Kidney Lipidomics by Mass Spectrometry Imaging: A Focus on the Glomerulus

Lipid disorders have been associated with glomerulopathies, a distinct type of renal pathologies, such as nephrotic syndrome. Global analyses targeting kidney lipids in this pathophysiologic context have been extensively performed, but most often regardless of the architectural and functional complexity of the kidney. The new developments in mass spectrometry imaging technologies have opened a promising field in localized lipidomic studies focused on this organ. In this article, we revisit the main works having employed the Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) technology, and the few reports on the use of TOF-Secondary Ion Mass Spectrometry (TOF-SIMS). We also present a first analysis of mouse kidney cortex sections by cluster TOF-SIMS. The latter represents a good option for high resolution lipid imaging when frozen unfixed histological samples are available. The advantages and drawbacks of this developing field are discussed.

Dyslipidaemia in nephrotic syndrome: mechanisms and treatment

Nephrotic syndrome is a highly prevalent disease that is associated with high morbidity despite notable advances in its treatment. Many of the complications of nephrotic syndrome, including the increased risk of atherosclerosis and thromboembolism, can be linked to dysregulated lipid metabolism and dyslipidaemia. These abnormalities include elevated plasma levels of cholesterol, triglycerides and the apolipoprotein B-containing lipoproteins VLDL and IDL; decreased lipoprotein lipase activity in the endothelium, muscle and adipose tissues; decreased hepatic lipase activity; and increased levels of the enzyme PCSK9. In addition, there is an increase in the plasma levels of immature HDL particles and reduced cholesterol efflux. Studies from the past few years have markedly improved our understanding of the molecular pathogenesis of nephrotic syndrome-associated dyslipidaemia, and also heightened our awareness of the associated exacerbated risks of cardiovascular complications, progressive kidney disease and thromboembolism. Despite the absence of clear guidelines regarding treatment, various strategies are being increasingly utilized, including statins, bile acid sequestrants, fibrates, nicotinic acid and ezetimibe, as well as lipid apheresis, which seem to also induce partial or complete clinical remission of nephrotic syndrome in a substantial percentage of patients. Future potential treatments will likely also include inhibition of PCSK9 using recently-developed anti-PCSK9 monoclonal antibodies and small inhibitory RNAs, as well as targeting newly identified molecular regulators of lipid metabolism that are dysregulated in nephrotic syndrome.

Characteristics of lipid metabolism including serum apolipoprotein M levels in patients with primary nephrotic syndrome

Background

Apolipoprotein M (apoM) is a 26-kD apolipoprotein that is mainly expressed in specific cell types, such as human liver parenchymal cells and kidney proximal renal tubular epithelial cells. ApoM can regulate the formation of pre-β-HDL and the reverse cholesterol transport and thus plays an important role in the metabolism of lipids and lipoproteins, meaning that it can affect the development of lipid metabolism disorders. Significantly elevated serum apoM levels are detected in patients with hyperlipidemia. However, few studies have shown how apoM is expressed in primary nephrotic syndrome (PNS), which is often accompanied with hyperlipidemia, and the underlying mechanism is poorly understood. This study was aimed at examining the apoM levels in patients with PNS and at determining the effects of PNS on serum apoM levels in these patients.

Methods

This study included patients with hyperlipidemia (n = 37), the PNS with hyperlipidemia group (n = 62), PNS without hyperlipidemia group (n = 33), and healthy controls (n = 73). The age and body–mass index (BMI) matched among the groups of participants. Their serum apoM concentrations were measured by an enzyme-linked immunosorbent assay. Serum levels of conventional lipids and renal function indices were assessed using an automatic biochemical analyzer. The data were analyzed by means of Pearson’s correlation coefficient (continuous variables) or Student’s t test (mean differences).

Results

The average serum apoM concentrations were higher in the hyperlipidemia group (61.1 ± 23.2 mg/L, P = 0.004) than in the healthy controls (31.6 ± 18.92 mg/L). The serum apoM concentrations were lower in the PNS with hyperlipidemia group (25.1 ± 16.31 mg/L, P = 0.007) and in the PNS without hyperlipidemia group (21.00 ± 17.62 mg/L, P = 0.003) than in the healthy controls. The serum apoM concentrations in the PNS with hyperlipidemia group did not differ significantly from those in the PNS without hyperlipidemia group (P = 0.083). Moreover, serum apoM levels positively correlated with serum high-density lipoprotein cholesterol (HDL-C) and apoA1 levels and negatively correlated with proteinuria in PNS patients (r = 0.458, P = 0.003; r = 0.254, P = 0.022; r = −0.414, P = 0.028).

Conclusion

Serum apoM concentrations are higher in patients with hyperlipidemia than in healthy controls. Low serum apoM levels in patients with PNS are likely caused by PNS.

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.

Treatment of Hyperlipidemia Changes With Level of Kidney Function-Rationale

Lipoprotein abnormalities such as low levels of high-density lipoprotein (HDL) and high triglycerides (TGs), associated with the metabolic syndrome, are also associated with subsequent decline in kidney function. Patients with end-stage kidney disease also exhibit low HDL and high TGs and a modest reduction in low-density lipoprotein (LDL), although the mechanisms responsible for these changes differ when patients with end-stage kidney disease are compared with those having metabolic syndrome with normal kidney function, as do lipoprotein structures. Among dialysis patients, oxidized LDL, levels of TG-rich intermediate-density lipoprotein, and low HDL are associated with aortic pulsewave velocity and other markers of atherosclerosis. Statins are effective in reducing LDL and do decrease risk of cardiovascular events in patients with CKD not requiring dialysis but have no significant effect on outcomes, including all-cause mortality among dialysis patients. Similarly gemfibrozil and other fibrates lower TGs, increase HDL, and reduce cardiovascular events, but not mortality, among patients with CKD not requiring dialysis but have no significant effect on cardiovascular outcomes in dialysis patients. There is potential clinical benefit in treating elevated LDL, TGs, and low HDL in patients with CKD using statins or fibrates in those not yet requiring dialysis.

Disorders of lipid metabolism in nephrotic syndrome: mechanisms and consequences

Nephrotic syndrome results in hyperlipidemia and profound alterations in lipid and lipoprotein metabolism. Serum cholesterol, triglycerides, apolipoprotein B (apoB)-containing lipoproteins (very low-density lipoprotein [VLDL], immediate-density lipoprotein [IDL], and low-density lipoprotein [LDL]), lipoprotein(a) (Lp[a]), and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are increased in nephrotic syndrome. This is accompanied by significant changes in the composition of various lipoproteins including their cholesterol-to-triglyceride, free cholesterol-to-cholesterol ester, and phospholipid-to-protein ratios. These abnormalities are mediated by changes in the expression and activities of the key proteins involved in the biosynthesis, transport, remodeling, and catabolism of lipids and lipoproteins including apoproteins A, B, C, and E; 3-hydroxy-3-methylglutaryl-coenzyme A reductase; fatty acid synthase; LDL receptor; lecithin cholesteryl ester acyltransferase; acyl coenzyme A cholesterol acyltransferase; HDL docking receptor (scavenger receptor class B, type 1 [SR-B1]); HDL endocytic receptor; lipoprotein lipase; and hepatic lipase, among others. The disorders of lipid and lipoprotein metabolism in nephrotic syndrome contribute to the development and progression of cardiovascular and kidney disease. In addition, by limiting delivery of lipid fuel to the muscles for generation of energy and to the adipose tissues for storage of energy, changes in lipid metabolism contribute to the reduction of body mass and impaired exercise capacity. This article provides an overview of the mechanisms, consequences, and treatment of lipid disorders in nephrotic syndrome.

Proteinuria and lipoprotein lipase activity in Miniature Schnauzer dogs with and without hypertriglyceridemia

Spontaneous hyperlipidemia in rats causes glomerular disease. Idiopathic hypertriglyceridemia (HTG) is prevalent in Miniature Schnauzers, but its relationship with proteinuria is unknown. Decreased activity of major lipid metabolism enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL), may play a role in the cyclic relationship between hyperlipidemia and proteinuria. These enzymes have also not been previously investigated in Miniature Schnauzers. The aims of this study were to determine the relationship between HTG and proteinuria in Miniature Schnauzers and to measure LPL and HL activities in a subset of dogs. Fifty-seven Miniature Schnauzers were recruited (34 with and 23 without HTG). Fasting serum triglyceride concentrations and urine protein-to-creatinine ratios (UPC) were measured in all dogs, and LPL and HL activities were determined in 17 dogs (8 with and 9 without HTG). There was a strong positive correlation between triglyceride concentration and UPC (r = 0.77-0.83, P < 0.001). Proteinuria (UPC ≥ 0.5) was present in 60% of dogs with HTG and absent from all dogs without HTG (P < 0.001). Proteinuric dogs were not azotemic or hypoalbuminemic. Dogs with HTG had a 65% reduction in LPL activity relative to dogs without HTG (P < 0.001); HL activity did not differ. Proteinuria occurs with HTG in Miniature Schnauzers and could be due to lipid-induced glomerular injury. Reduced LPL activity may contribute to the severity of HTG, but further assay validation is required.

The non-immunosuppressive management of childhood nephrotic syndrome

Idiopathic nephrotic syndrome (INS) is one of the most common renal diseases found in the paediatric population and is associated with significant complications, including infection and thrombosis. A high proportion of children enter sustained remission before adulthood, and therapy must therefore mitigate the childhood complications, while minimising the long-term risk to health. Here we address the main complications of INS and summarise the available evidence and guidance to aid the clinician in determining the appropriate treatment for children with INS under their care. Additionally, we highlight areas where no consensus regarding appropriate management has been reached. In this review, we detail the reasons why routine prophylactic antimicrobial and antithrombotic therapy are not warranted in INS and emphasise the conservative management of oedema. When pharmacological intervention is required for the treatment of oedema, we provide guidance to aid the clinician in determining the appropriate therapy. Additionally, we discuss obesity and growth, fracture risk, dyslipidaemia and thyroid dysfunction associated with INS. Where appropriate, we describe how recent developments in research have identified potential novel therapeutic targets.

HDL abnormalities in nephrotic syndrome and chronic kidney disease

Normal HDL activity confers cardiovascular and overall protection by mediating reverse cholesterol transport and through its potent anti-inflammatory, antioxidant, and antithrombotic functions. Serum lipid profile, as well as various aspects of HDL metabolism, structure, and function can be profoundly altered in patients with nephrotic range proteinuria or chronic kidney disease (CKD). These abnormalities can, in turn, contribute to the progression of cardiovascular complications and various other comorbidities, such as foam cell formation, atherosclerosis, and/or glomerulosclerosis, in affected patients. The presence and severity of proteinuria and renal insufficiency, as well as dietary and drug regimens, pre-existing genetic disorders of lipid metabolism, and renal replacement therapies (including haemodialysis, peritoneal dialysis, and renal transplantation) determine the natural history of lipid disorders in patients with kidney disease. Despite the adverse effects associated with dysregulated reverse cholesterol transport and advances in our understanding of the underlying mechanisms, safe and effective therapeutic interventions are currently lacking. This Review provides an overview of HDL metabolism under normal conditions, and discusses the features, mechanisms, and consequences of HDL abnormalities in patients with nephrotic syndrome or advanced CKD.

Residual Cardiovascular Risk in Chronic Kidney Disease: Role of High-density Lipoprotein

Although reducing low-density lipoprotein-cholesterol (LDL-C) levels with lipid-lowering agents (statins) decreases cardiovascular disease (CVD) risk, a substantial residual risk (up to 70% of baseline) remains after treatment in most patient populations. High-density lipoprotein (HDL) is a potential contributor to residual risk, and low HDL-cholesterol (HDL-C) is an established risk factor for CVD. However, in contrast to conventional lipid-lowering therapies, recent studies show that pharmacologic increases in HDL-C levels do not bring about clinical benefits. These observations have given rise to the concept of dysfunctional HDL where increases in serum HDL-C may not be beneficial because HDL loss of function is not corrected by or even intensified by the therapy. Chronic kidney disease (CKD) increases CVD risk, and patients whose CKD progresses to end-stage renal disease (ESRD) requiring dialysis are at the highest CVD risk of any patient type studied. The ESRD population is also unique in its lack of significant benefit from standard lipid-lowering interventions. Recent studies indicate that HDL-C levels do not predict CVD in the CKD population. Moreover, CKD profoundly alters metabolism and composition of HDL particles and impairs their protective effects on functions such as cellular cholesterol efflux, endothelial protection, and control of inflammation and oxidation. Thus, CKD-induced perturbations in HDL may contribute to the excess CVD in CKD patients. Understanding the mechanisms of vascular protection in renal disease can present new therapeutic targets for intervention in this population.

Nutritional and other types of oedema, albumin, complex carbohydrates and the interstitium - a response to Malcolm Coulthard's hypothesis: Oedema in kwashiorkor is caused by hypo-albuminaemia

The various types of oedema in man are considered in relation to Starling's hypothesis of fluid movement from capillaries, with the main emphasis on nutritional oedema and the nephrotic syndrome in children. It is concluded that each condition has sufficient anomalous findings to render Starling's hypothesis untenable. The finding that the endothelial glycocalyx is key to control of fluid movement from and into the capillaries calls for complete revision of our understanding of oedema formation. The factors so far known to affect the function of the glycocalyx are reviewed. As these depend upon sulphated proteoglycans and other glycosaminoglycans, the argument is advanced that the same abnormalities will extend to the interstitial space and that kwashiorkor is fundamentally related to a defect in sulphur metabolism which can explain all the clinical features of the condition, including the formation of oedema.

Mechanism underlying an elevated serum bile acid level in chronic renal failure patients

INTRODUCTION

Bile acids play an important role in the digestion of dietary lipids. Bile acid metabolism is regulated by the digestive system. The kidney is an important organ of the urinary system and is believed to play a minor role in bile acid excretion; however, many recent studies have reported an increased serum bile acid level and alterations in bile acid homeostasis in both clinical and animal model studies on chronic renal failure. The existing research findings on the mechanisms underlying this phenomenon were mostly derived from animal model studies, but clinical investigations have been limited.

MATERIALS AND METHODS

Kidney tissues and serum and urine samples from CRF patients and normal controls were studied.

RESULTS

We found increased serum bile acid levels and decreased urine bile acid output levels in chronic renal failure patients. Mesangial cell and endothelial cell proliferation, glomerular sclerosis, renal interstitial fibrosis, and intrarenal vascular sclerosis were observed based on hematoxylin-eosin and Masson trichrome staining pathology analysis. Scatter diagram and Pearson correlation analysis showed that in chronic renal failure patients, the estimated glomerular filtration rate and serum bile acid level were interrelated. Reverse transcription polymerase chain reaction and Western blotting results indicated that reabsorption and secretion of bile acid at the apical surface of the proximal renal tubular did not contribute to the elevated serum BA level.

CONCLUSION

The increase in plasma bile acid is due to decreased bile acid filtration through the kidneys in CRF patients.

Fish oil -- how does it reduce plasma triglycerides?

Long chain omega-3 fatty acids (FAs) are effective for reducing plasma triglyceride (TG) levels. At the pharmaceutical dose, 3.4g/day, they reduce plasma TG by about 25-50% after one month of treatment, resulting primarily from the decline in hepatic very low density lipoprotein (VLDL-TG) production, and secondarily from the increase in VLDL clearance. Numerous mechanisms have been shown to contribute to the TG overproduction, but a key component is an increase in the availability of FAs in the liver. The liver derives FAs from three sources: diet (delivered via chylomicron remnants), de novo lipogenesis, and circulating non-esterified FAs (NEFAs). Of these, NEFAs contribute the largest fraction to VLDL-TG production in both normotriglyceridemic subjects and hypertriglyceridemic, insulin resistant patients. Thus reducing NEFA delivery to the liver would be a likely locus of action for fish oils (FO). The key regulator of plasma NEFA is intracellular adipocyte lipolysis via hormone sensitive lipase (HSL), which increases as insulin sensitivity worsens. FO counteracts intracellular lipolysis in adipocytes by suppressing adipose tissue inflammation. In addition, FO increases extracellular lipolysis by lipoprotein lipase (LpL) in adipose, heart and skeletal muscle and enhances hepatic and skeletal muscle β-oxidation which contributes to reduced FA delivery to the liver. FO could activate transcription factors which control metabolic pathways in a tissue specific manner regulating nutrient traffic and reducing plasma TG. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.

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.

Dyslipidemia associated with chronic kidney disease

Cardiovascular disease is a major cause of morbidity and mortality in patients with impaired renal function. Dyslipidemia has been established as a well-known traditional risk factor for cardiovascular disease (CVD) in the general population and it is well known that patients with chronic kidney disease (CKD) exhibit significant alterations in lipoprotein metabolism. In this review, the pathogenesis and treatment of CKD-induced dyslipidemia are discussed. Studies on lipid abnormalities in predialysis, hemodialysis and peritoneal dialysis patients are analyzed. In addition, the results of the studies that tested the effects of the hypolipidemic drugs on cardiovascular morbidity and mortality in patients with CKD are reported.

Cilnidipine suppresses podocyte injury and proteinuria in metabolic syndrome rats: possible involvement of N-type calcium channel in podocyte

OBJECTIVES

Clinical studies have indicated the beneficial effect of an L/N-type calcium channel blocker (CCB), cilnidipine, on the progression of proteinuria in hypertensive patients compared with an L-type CCB, amlodipine. In the present study, we examined the effects of cilnidipine and amlodipine on the renal injury in spontaneously hypertensive rat/ND mcr-cp (SHR/ND) and their underlying mechanism.

METHODS AND RESULTS

SHR/ND were treated with vehicle (nU10), cilnidipine [33 mg/kg per day, orally (p.o.); nU11] or amlodipine (20 mg/kg per day, p.o.; nU9) for 20 weeks. SHR/ND developed proteinuria in an age-dependent manner. Cilnidipine suppressed the proteinuria greater than amlodipine did. The immunohistochemical analysis showed that N-type calcium channel and Wilm's tumor factor, a marker of podocyte, were co-expressed. SHR/ND had significantly greater desmin staining, an indicator of podocyte injury, with lower podocin and nephrin expression in the glomeruli than Wistar-Kyoto rat or SHR. Cilnidipine significantly prevented the increase in desmin staining and restored the glomerular podocin and nephrin expression compared with amlodipine. Cilnidipine also prevented the increase in renal angiotensin II content, the expression and membrane translocation of NADPH oxidase subunits and dihydroethidium staining in SHR/ND. In contrast, amlodipine failed to change these renal parameters.

CONCLUSION

These data suggest that cilnidipine suppressed the development of proteinuria greater than amlodipine possibly through inhibiting N-type calcium channel-dependent podocyte injury in SHR/ND.

Early intervention strategies to lower cardiovascular risk in early nephropathy: focus on dyslipidemia

Patients with chronic kidney disease (CKD) are at high cardiovascular risk and we can consider them to have a risk equivalent to coronary heart disease, putting them into the high-risk category. A mixed dyslipidemia with high triglyceride levels; low high-density lipoprotein (HDL) levels; and small, dense low-density lipoprotein (LDL) particles is a common pattern in patients with CKD, contributing to their high cardiovascular disease (CVD) risk. A treatment strategy to reduce LDL cholesterol to the current high-risk category goals reduces risk similar to patients without CKD. Emerging evidence suggests that targeting non-HDL cholesterol can have the potential to bring about further CVD risk reduction. Non-HDL cholesterol should be a secondary target for all patients with CKD. Further studies are needed to determine the magnitude of the risk reduction we can expect to gain by targeting non-HDL cholesterol and the most effective way to treat this target.

Lipoprotein lipase releases esterified oxylipins from very low-density lipoproteins

We previously demonstrated that defects in lipoprotein metabolism alter the distribution of oxygenated polyunsaturated fatty acids (PUFAs) in lipoprotein particles. If these oxidation products are released by lipoprotein lipase (LpL), then their delivery to peripheral tissues with bulk lipids could influence cellular function. Using 26-week-old normolipidemic and hyperlipidemic Zucker rats, we measured PUFA alcohols, epoxides, diols, ketones, and triols (i.e. oxylipins) in esterified and non-esterified fractions of whole plasma, VLDL, and LpL-generated VLDL-lipolysates. Whole plasma, VLDL, and lipolysate oxylipin profiles were distinct and altered by hyperlipidemia. While >90% of the whole plasma oxylipins were esterified, the fraction of each oxylipin class in the VLDL varied: 46% of alcohols, 30% of epoxides, 19% of diols, <10% of ketones, and <1% triols. Whole plasma was dominated by arachidonate alcohols, while the linoleate alcohols, epoxides, and ketones showed an increased prevalence in VLDL. LpL-mediated VLDL lipolysis of PUFA alcohols, diols and ketones was detected and the relative abundance of oxygenated linoleates was enhanced in the lipolysates, relative to their corresponding VLDL. In summary esterified oxylipins were seen to be LpL substrates with heterogeneous distributions among lipoprotein classes. Moreover, oxylipin distributions are changes within the context of obesity-associated dyslipidemia. These results support the notion that the VLDL-LpL axis may facilitate the delivery of plasma oxylipins to the periphery. The physiological implications of these findings are yet to be elucidated; however, these molecules are plausible indicators of systemic oxidative stress, and could report this status to the peripheral tissues.

Oxidative modification of low-density lipoprotein in relation to dyslipidemia and oxidant status in children with steroid sensitive nephrotic syndrome

It has been proposed that nephrotic syndrome is a consequence of an imbalance between oxidant/antioxidant statuses. The present study aimed to assess oxidant and antioxidant status in relation to dyslipidemia in children during remission and relapse phases of steroid sensitive nephrotic syndrome (SSNS). The study dealt with 40 children diagnosed as SSNS. They were categorized into two subgroups. The first subgroup included 25 children during remission stage. The second subgroup included 15 children during relapse. Control group consisted of age and gender-matched 15 healthy children. Significantly higher serum levels of malondialdehyde, oxidized LDL, total cholesterol, LDL cholesterol, triglycerides, apolipoprotein A-I, and apolipoprotein-B were observed in patients with SSNS especially in the relapsers. The serum levels of albumin, glutathione peroxidase activity, vitamin C, A, and E, and HDL cholesterol were significantly lower in patients especially among relapsers. In conclusion, a strong relationship between the oxidant/antioxidant status and dyslipidemia is documented in patients with SSNS, especially among relapsers. No normalization of the biochemical indices was observed despite the use of glucocorticoids. Therefore, the combined use of steroid, antioxidant therapy, and lipid lowering therapy can be recommended in such children.

Proteinuria increases oxylipid concentrations in VLDL and HDL but not LDL particles in the rat

We previously established that proteinuria alters the apolipoprotein content of lipoproteins. This study was conducted to establish whether proteinuria also alters the concentrations of oxidized lipids within lipoprotein density fractions. To this end, we induced passive Heymann nephritis in Sprague Dawley rats and measured an array of alkaline-stable oxylipids in VLDL, LDL, and HDL particles. Proteinuria increased the total oxylipid amounts in the HDL and VLDL fractions. More importantly, these levels were increased when expressed per unit lipoprotein protein, indicating that the oxidized lipid load per particle was increased. Epoxides and diols increased approximately 2-fold in HDL and approximately 5-fold in VLDL, whereas LDL showed approximately 2-fold decreases. The hydroxyeicosatetraenoic acids and hydroxyoctadecadienoic acids (HODEs) increased >4-fold in HDL and >20-fold in VLDL, whereas LDL showed approximately 2-fold decreases in the HODEs. Therefore, nephrotic syndrome alters the lipoprotein oxylipid composition independently of an increase in total lipoprotein levels. These proteinuria-induced changes may be associated with the cardiovascular risk of lipoprotein oxidation.

The dyslipidemia of chronic renal disease: effects of statin therapy

PURPOSE OF REVIEW

Dyslipidemia is a prevalent condition in patients with chronic renal disease, but is often left untreated. Statin treatment constitutes an effective way to improve lipid abnormalities. This review summarizes present studies on dyslipidemia and its treatment in patients with chronic renal disease.

RECENT FINDINGS

The specific dyslipidemia in renal disease is associated with the presence of proteinuria and decreased creatinine clearance, and may even adversely affect the progression of chronic renal disease. Statin therapy may have renoprotective effects due to a combination of lipid lowering and pleiotropic effects. Statins exert several anti-inflammatory properties and lead to a decrease of proteinuria. Post-hoc analyses of large-scale lipid lowering trials have shown that the reduction of cardiovascular risk was equivalent to the reduction achieved in patients without chronic renal failure. We feel, however, that if intervention with statins is postponed until patients reach end-stage renal disease, statins have limited benefit.

SUMMARY

Present studies suggest that patients with renal disease should be screened early for dyslipidemia and that statins have to be considered as the lipid lowering therapy of choice. These drugs reduce cardiovascular risk. Further studies are needed to firmly establish whether statins preserve renal function.

Statins in nephrotic syndrome: a new weapon against tissue injury

The nephrotic syndrome is characterized by metabolic disorders leading to an increase in circulating lipoproteins levels. Hypertriglyceridemia and hypercholesterolemia in this case may depend on a reduction in triglyceride-rich lipoproteins catabolism and on an increase in hepatic synthesis of Apo B-containing lipoproteins. These alterations are the starting point of a self-maintaining mechanism, which can accelerate the progression of chronic renal failure. Indeed, hyperlipidemia can affect renal function, increase proteinuria and speed glomerulosclerosis, thus determining a higher risk of progression to dialysis. 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is the rate-limiting enzyme in cholesterol synthesis from mevalonate and its inhibitors, or statins, can therefore interfere with the above-mentioned consequences of hyperlipidemia. Statins are already well known for their effectiveness on primary cardiovascular prevention, which cannot be explained only through their hypolipemic effect. As far as kidney diseases are concerned, statin therapy has been shown to prevent creatinine clearance decline and to slow renal function loss, particularly in case of proteinuria, and its favorable effect may depend only partially on the attenuation of hyperlipidemia. Statins may therefore confer tissue protection through lipid-independent mechanisms, which can be triggered by other mediators, such as angiotensin receptor blockers. Possible pathways for the protective action of statins, other than any hypocholesterolemic effect, are: cellular apoptosis/proliferation balance, inflammatory cytokines production, and signal transduction regulation. Statins also play a role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. In this study, we would like to provide scientific evidences for the pleiotropic effects of statins, which could be the starting point for the development of new therapeutical strategies in different clinical areas.

The complex nature of the interaction between disease activity and therapy on the lipid profile in patients with pediatric systemic lupus erythematosus

OBJECTIVE

To determine the prevalence of lipid abnormalities at different times and to determine the influence of both the disease and corticosteroid therapy on lipid abnormalities in pediatric patients with systemic lupus erythematosus (SLE).

METHODS

Lipid measurements were obtained in an inception cohort of 139 pediatric patients with SLE (114 females). Fasting levels of total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol in the SLE patients were compared with those in age- and sex-matched control subjects. Disease activity levels and medication dosages were obtained at the time of lipid measurements.

RESULTS

At the time of diagnosis, the mean levels of total cholesterol, LDL cholesterol, and triglycerides were highest, whereas the mean levels of HDL cholesterol were lowest. The percentage of patients with abnormal triglyceride values was highest at diagnosis, decreased at year 1, and then remained relatively constant thereafter. The mean total cholesterol and LDL cholesterol levels decreased at year 1 as compared with the time of diagnosis and then remained relatively constant. The lowest mean HDL cholesterol levels were found at the time of diagnosis, and these values rose with time. Comparison of lipid levels at different prednisone dosages and disease activity levels revealed that changes in triglyceride levels were mainly associated with changes in disease activity, changes in both total cholesterol and LDL cholesterol levels were associated with changes in the prednisone dosage and not disease activity, and low levels of HDL cholesterol were associated with active SLE, whereas the prednisone dosage was associated with increased levels of HDL cholesterol.

CONCLUSION

Factors intrinsic to SLE appear to alter lipid levels. Control of SLE may be the most important factor in improving abnormal lipid profiles, and paradoxically, prednisone therapy may improve abnormal lipid levels.

Dyslipidemia and nephrotic syndrome: Recent advances

Patients with nephrotic syndrome (NS) have one of the most pronounced secondary changes in lipoprotein metabolism known, and the magnitude of the changes correlates with the severity of the disease. These changes are of a quantitative as well as a qualitative nature. All apolipoprotein B (apo B)-containing lipoproteins, such as very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and lipoprotein(a) [Lp(a)], are elevated in nephrotic syndrome. High-density lipoproteins (HDL) are reported to be unchanged or reduced. In addition to these quantitative changes, the lipoprotein composition is markedly changed, with a higher ratio of cholesterol to triglycerides in the apo B-containing lipoproteins and an increase in the proportion of cholesterol, cholesterol ester, and phospholipids compared with proteins. Also apolipoproteins show major changes, with an increase in apolipoprotein A-I, A-IV, B, C, and E. Particularly the changes in apo C-II, which is an activator of the enzyme lipoprotein lipase (LPL), and apo C-III, an inhibitor of LPL, with an increase of the C-III to C-II ratio, might contribute to the impaired lipoprotein catabolism in NS. The mechanisms for these changes in lipoprotein metabolism are discussed in this review as far as they are known. Furthermore, the tremendous elevations of Lp(a) in nephrotic syndrome and its primary and secondary causes are reviewed. Primary causes became recently apparent by a significantly higher frequency of low-molecular-weight apo(a) phenotypes in patients compared with controls. The secondary causes were shown by an increase of Lp(a) in all apo(a) isoform groups. Because Lp(a) is an LDL-like particle that is usually included in the measured or calculated LDL cholesterol fraction, the influence of the extremely high Lp(a) levels in NS on the measurement of LDL cholesterol is discussed.

Graded effects of proteinuria on HDL structure in nephrotic rats

Nephrotic syndrome is characterized by increased triglycerides resulting from decreased clearance of VLDL and chylomicrons. These triglyceride-rich lipoproteins are structurally altered by interaction with HDL derived from animals with proteinuria and not as a consequence of hypoalbuminemia. HDL isolated from rats with massive proteinuria is depleted in apolipoprotein E (apoE). It is unknown at what threshold of urinary albumin loss HDL structure is altered, and it is unknown what effects proteinuria has on apolipoproteins other than apoE. Two models of albuminuria were used in Sprague-Dawley rats: Adriamycin and passive Heymann nephritis (HN). The adriamycin group was divided into minimal albumin excretion (MAE) and intermediate albumin excretion (MAE, 1 to 40; intermediate albumin excretion, 60 to 210 mg/d per 100 g body wt). Urinary albumin excretion exceeded 300 mg/d per 100 g body wt in the HN rats. HDL apolipoprotein composition was analyzed with SDS-PAGE densitometry and liquid chromatography-time of flight mass spectrometer mass spectrometry. HDL apoA-IV content relative to apoA-I was reduced at all levels of albuminuria (P < 0.0001). ApoE was not reduced in MAE but was significantly reduced in IAE (72%; P < 0.001). By contrast, apoA-II and apoC-III were each significantly increased with increasing UAE. ApoA-IV and apoE were decreased to approximately 10% of control in HDL isolated from rats with HN, whereas apoA-II, apoC-II, and apoC-III were each significantly increased relative to apoA-I. HDL is structurally altered by levels of albuminuria that are insufficient to change serum albumin levels and is progressively altered as albuminuria increases.

Up-regulation of hepatic Acyl CoA: Diacylglycerol acyltransferase-1 (DGAT-1) expression in nephrotic syndrome

BACKGROUND

Nephrotic syndrome is associated with hypercholesterolemia, hypertriglyceridemia, and marked elevations of plasma low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL). Hypertriglyceridemia in nephrotic syndrome is accompanied by increased hepatic fatty acid synthesis, elevated triglyceride secretion, as well as lipoprotein lipase, VLDL-receptor, and hepatic triglyceride lipase deficiencies, which lead to impaired clearance of triglyceride-rich lipoproteins. Acyl CoA: diacylglycerol acyltransferase (DGAT) is a microsomal enzyme that joins acyl CoA to 1, 2-diacylglycerol to form triglyceride. Two distinct DGATs (DGAT-1 and DGAT2) have recently been identified in the liver and other tissues. The present study tested the hypothesis that the reported increase in hepatic triglyceride secretion in nephrotic syndrome may be caused by up-regulation of DGAT.

METHODS

Male Sprague-Dawley rats were rendered nephrotic by two sequential injections of puromycin aminonucleoside (130 mg/kg on day 1 and 60 mg/kg on day 14) and studied on day 30. Placebo-treated rats served as controls. Hepatic DGAT-1 and DGAT-2 mRNA abundance and enzymatic activity were measured.

RESULTS

The nephrotic group exhibited heavy proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, and marked elevation of VLDL concentration. Hepatic DGAT-1 mRNA, DGAT-1, and total DGAT activity were significantly increased, whereas DGAT-2 mRNA abundance and activity were unchanged in the nephrotic rats compared to the control animals. The functional significance of elevation of DGAT activity was illustrated by the reduction in microsomal free fatty acid concentration in the liver of nephrotic animals.

CONCLUSION

Nephrotic syndrome results in up-regulation of hepatic DGAT-1 expression and activity, which can potentially contribute to the associated hypertriglyceridemia by enhancing triglyceride synthesis. Thus, it appears that both depressed catabolism and increased synthetic capacity contribute to hypertriglyceridemia of nephrotic syndrome.

AT-1 receptor blockade prevents proteinuria, renal failure, hyperlipidemia, and glomerulosclerosis in the Imai rat

BACKGROUND

The Imai rat is a model of spontaneous focal glomerulosclerosis which leads to nephrotic syndrome, hyperlipidemia, hypertension, and progressive renal failure. We evaluated the effects of angiotensin II receptor type 1 (AT-1)blockade, and compared the results with the effects of the administration of hypolipidemic treatment with a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. All treatments were started at 10 weeks of age when the rats were already proteinuric and continued for 6 months when rats were sacrificed.

METHODS

The following groups (N= 6 each) were studied: (1) control Sprague-Dawley rats, 34 weeks old; (2) Imai group that received vehicle; (3) Imai + angiotensin II receptor blockade (ARB) group that received olmesartan (10 mg/kg/day by gastric gavage); (4) Imai + prava group, that received pravastatin (20 mg/kg/day by gastric gavage); and (5) Imai + ARB + prava group that received both ARB and pravastatin. Lipid profile, renal function, and structure were assessed at 6 months.

RESULTS

As expected, the untreated Imai rats exhibited heavy proteinuria, hypoalbuminemia, hypertension, renal insufficiency, marked glomerulosclerosis, tubulointerstitial inflammation, and profound hyperlipidemia. Pravastatin treatment alone led to a significant, but partial improvement of hyperlipidemia and renal disease. The ARB treatment alone or in combination with pravastatin resulted in normalization of the blood pressure, urinary protein excretion, plasma cholesterol, triglycerides, low-density lipoproteins (LDLs), very low-density lipoproteins (VLDLs), and albumin concentrations and renal function. Significant glomerulosclerosis was prevented and tubulointerstitial injury and immune cell infiltration were reduced by long-term AT-1 blockade.

CONCLUSION

The study revealed that long-term AT-1 blockade corrects proteinuria, hyperlipidemia, and nephropathy in this model of spontaneous glomerulosclerosis.

The Potential Role of HMG-CoA Reductase Inhibitors in Pediatric Nephrotic Syndrome

OBJECTIVE

To evaluate the safety and efficacy of the hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) as a potential treatment option for the dyslipidemia associated with childhood nephrotic syndrome.

DATA SOURCES

Searches of MEDLINE (1966–April 2004), Cochrane Library, International Pharmaceutical Abstracts (1977–April 2004), and an extensive manual review of journals were performed using the key search terms nephrotic syndrome, familial hypercholesterolemia, dyslipidemia, and HMG-CoA reductase inhibitor.

STUDY SELECTION AND DATA EXTRACTION

Two prospective uncontrolled studies evaluating the safety and efficacy of statin therapy in pediatric nephrotic syndrome were included.

DATA SYNTHESIS

While an extensive amount of data is available in adult nephrotic syndrome in which statin therapy decreases total plasma cholesterol 22–39%, low-density lipoprotein cholesterol (LDL-C) 27–47%, and total plasma triglycerides 13–38%, only 2 small uncontrolled studies have been conducted evaluating the utility of these agents in pediatric nephrotic syndrome. These studies indicate that statins are capable of safely reducing total cholesterol up to 42%, LDL-C up to 46%, and triglyceride levels up to 44%.

CONCLUSIONS

Lowering cholesterol levels during childhood may reduce the risk for atherosclerotic changes and may thus be of benefit in certain patients with nephrotic syndrome. Statins have demonstrated short-term safety and efficacy in the pediatric nephrotic syndrome population. Implementing pharmacologic therapy with statins in children with nephrotic syndrome must be done with care until controlled studies are conducted in this population.

Nephrotic livers secrete normal VLDL that acquire structural and functional defects following interaction with HDL

BACKGROUND

Binding of very low-density lipoprotein (VLDL) isolated from serum of nephrotic rats VLDL to endothelial cells is defective. This defect is conferred on normal VLDL by prior incubation with high-density lipoprotein (HDL) from nephrotic, but not control rats. It is not known whether the defect is present in nascent VLDL (nVLDL) or is acquired after secretion. We test the hypothesis that VLDL is normal at the time of secretion from the liver and the defect in binding to endothelium is conferred following secretion through interaction with HDL.

METHODS

nVLDL was synthesized by and collected from isolated perfused livers from either control or nephrotic rats. nVLDL was labeled with 3H-oleate to measure binding and 35S methionine to evaluate apolipoprotein exchange and composition. To test whether HDL conferred a binding defect, nVLDL was incubated with HDL obtained either from control or nephrotic rats prior to measurement of binding. To distinguish the effects of proteinuria from reduced albumin concentration we additionally incubated nVLDL with HDL obtained from rats with hereditary analbuminemia. Both HDL and VLDL were reisolated by centrifugation prior to subsequent binding and lipolysis determination. Exchange of 35S-labeled apolipoprotein E (apoE) among the subsequent VLDL and HDL fractions was determined. To determine the effect of HDL on lipolysis, HDL-treated VLDL was exposed to lipoprotein lipase-coated 96-well plates and 3H-oleate release measured. To establish whether differences in apoE content could explain the differences in binding and lipolysis, apoE was restored to nephrotic VLDL and lipolysis and binding were subsequently measured.

RESULTS

Binding of nephrotic nVLDL was greater than control nVLDL (0.58 +/- 0.13 vs. 0.75 +/- 0.07 ng protein bound/mg cell protein) (P= 0.04, N= 6). Lipolysis was similarly elevated (0.091 +/- 0.010 vs 0.064 +/- 0.002 nmol NEFA released/well/hour) (P < 0.05). Prior incubation with nephrotic HDL reduced binding of nVLDL obtained from either nephrotic or control livers (P= 0.02, N= 6). Treatment with nephrotic (vs. control) HDL reduced both binding (control nVLDL + control HDL, 0.64 +/- 0.02; control + nephrotic, 0.43 +/- 0.06; nephrotic + control, 0.69 +/- 0.05; and nephrotic + nephrotic, 0.62 +/- 0.04 mg VLDL protein/mg cell protein) and lipolysis (control nVLDL + control HDL, 0.053 +/- 0.004; control + nephrotic, 0.038 +/- 0.004; nephrotic + control, 0.069 +/- 0.004; and nephrotic + nephrotic, 0.062 +/- 0.004 nmol NEFA/well/hour) (P < 0.05 vs. nVLDL + control HDL) of nVLDL from either source. The apoE content of nVLDL coincubated with control HDL or analbuminemic HDL was increased compared nVLDL incubated with either no HDL or nephrotic HDL (P < 0.05). Similarly, the apoE/apoA-I ratio was reduced in HDL from nephrotic rats but not in HDL from controls (P < 0.05). Reintroduction of apoE to nephrotic VLDL resulted in increased binding.

CONCLUSION

Unlike circulating VLDL, binding of nVLDL from isolated livers from nephrotic rats to endothelial cells is greater and its lipolysis is increased compared to control nVLDL. Decreased binding and lipolysis is conferred following incubation with HDL isolated from control, but not nephrotic rats and binding can be restored by reintroduction of apoE. Thus both defects are conferred on VLDL by exposure to HDL obtained from nephrotic animals, possibly a consequence of a failure of nephrotic HDL to enrich VLDL with apoE during clearance.

Nephrotic syndrome in childhood

Childhood nephrotic syndromes are most commonly caused by one of two idiopathic diseases: minimal-change nephrotic syndrome (MCNS) and focal segmental glomerulosclerosis (FSGS). A third distinct type, membranous nephropathy, is rare in children. Other causes of isolated nephrotic syndrome can be subdivided into two major categories: rare genetic disorders, and secondary diseases associated with drugs, infections, or neoplasia. The cause of idiopathic nephrotic syndrome remains unknown, but evidence suggests it may be a primary T-cell disorder that leads to glomerular podocyte dysfunction. Genetic studies in children with familial nephrotic syndrome have identified mutations in genes that encode important podocyte proteins. Patients with idiopathic nephrotic syndrome are initially treated with corticosteroids. Steroid-responsiveness is of greater prognostic use than renal histology. Several second-line drugs, including alkylating agents, ciclosporin, and levamisole, may be effective for complicated and steroid-unresponsive MCNS and FSGS patients. Nephrotic syndrome is associated with several medical complications, the most severe and potentially fatal being bacterial infections and thromboembolism. Idiopathic nephrotic syndrome is a chronic relapsing disease for most steroid-responsive patients, whereas most children with refractory FSGS ultimately develop end-stage renal disease. Research is being done to further elucidate the disorder's molecular pathogenesis, identify new prognostic indicators, and to develop better approaches to treatment.

Diverse effects of increasing lisinopril doses on lipid abnormalities in chronic nephropathies

BACKGROUND

Dyslipidemia frequently complicates chronic nephropathies and increases the risk of renal and cardiovascular events. This might be ameliorated by drugs, such as angiotensin-converting enzyme inhibitors, which effectively reduce proteinuria.

METHODS AND RESULTS

In this longitudinal study, we evaluated the extent to which uptitration of the ACE inhibitor lisinopril to maximum tolerated doses (median [range]: 30 [10 to 40] mg/d) ameliorated proteinuria and dyslipidemia in 28 patients with nondiabetic chronic nephropathies. Maximum lisinopril doses significantly and safely reduced proteinuria, serum total, LDL cholesterol, and triglycerides without substantially affecting serum HDL and renal hemodynamics. Proteinuria already decreased at 10 mg/d. Serum lipids progressively and dose-dependently decreased during uptitration to maximum doses. Reduction in total and LDL cholesterol correlated with increases in serum albumin/total protein concentration and oncotic pressure, peaked at lisinopril maximum doses, and persisted after treatment withdrawal. Despite less proteinuria reduction, hypercholesterolemia decreased more (and reflected the increase in serum albumin) in hypoalbuminemic than in normoalbuminemic patients who, despite more proteinuria reduction, had less decrease in cholesterol and no changes in serum albumin. Changes in serum triglycerides were independent of changes in serum proteins, were strongly correlated with lisinopril doses (r=-0.89, P=0.003) and recovered promptly after treatment withdrawal. Lisinopril was well tolerated, did not affect renal hemodynamics, and caused symptomatic, reversible hypotension in only two patients.

CONCLUSIONS

In chronic nephropathies, angiotensin converting enzyme inhibitor uptitration to maximum tolerated doses safely ameliorated hypertriglyceridemia by a direct, dose-dependent effect, and hypercholesterolemia through amelioration of the nephrotic syndrome, particularly in patients with more severe hypoalbuminemia.

2-Hydroxyestradiol attenuates renal disease in chronic puromycin aminonucleoside nephropathy

It has been previously shown that 2-hydroxyestradiol (2-OHE) attenuates the development of renal disease in genetic nephropathy associated with obesity and the metabolic syndrome. The purpose of this study was to test the hypothesis that 2-OHE, irrespective of its effects on metabolic status and/or obesity, exerts direct renoprotective effects in vivo. First, the effects of increasing doses of 2-OHE on mesangial cell growth, proliferation, and collagen synthesis in isolated rat glomerular mesangial cells were evaluated in vitro. Second, the effects of 12-wk administration of 2-OHE (10 micro g/h per kg) on renal function and structure in chronic puromycin aminonucleoside (PAN)-induced nephropathy in rats were evaluated in vivo. 2-OHE concentration-dependently (0.001 to 1 micro mol/L; P < 0.001) inhibited serum (2.5%)-induced cell growth ((3)H-thymidine incorporation), collagen synthesis ((3)H-proline incorporation), and cell proliferation (cell number). Importantly, the inhibitory effects of 2-OHE (0.1 micro mol/L) were not blocked by ICI182780 (50 micro mol/L), an estrogen receptor antagonist. In vivo, chronic administration of PAN (75 mg/kg + 5 x 20 mg/kg) over 12 wk induced severe chronic renal disease. Chronic treatment with 2-OHE significantly (P < 0.05) attenuated PAN-induced decrease in glomerular filtration, reduced proteinuria, and the elevated BP, and it had no effect on PAN-induced increase in plasma cholesterol and triglycerides levels. 2-OHE had no effects on plasma testosterone levels in male nephropathic animals. Immunohistochemical staining for collagen IV and proliferating cell nuclear antigen (PCNA) in glomeruli and transforming growth factor-beta (TGF-beta) in renal tubular cells were significantly higher in PAN nephropatic rats versus control animals with intact kidneys. PAN also markedly increased glomerular and interstitial macrophage infiltration (ED1(+) cells). 2-OHE had no effects on renal tubular cell TGF-beta, but it significantly reduced glomerular PCNA and collagen IV and glomerular and interstitial macrophage infiltration. In summary, this study provides the first evidence that 2-OHE exerts direct renoprotective effects in vivo. These effects are mediated by estrogen receptor-independent mechanisms and are due, at least in part, to the inhibition of some of the key proliferative mechanisms involved in glomerular remodeling and sclerosis.

Hyperlipidemia in kidney disease: causes and consequences

Dyslipidemias are common in patients with chronic kidney disease. The causes vary with the stage of kidney disease, the degree of proteinuria, and the modality of end-stage renal disease treatment. Dyslipidemias have been associated with kidney disease progression, and a number of small, randomized, controlled trials of lipid-lowering agents have been conducted. Unfortunately, the results of these trials, although encouraging, have been inconclusive because of the small numbers of patients enrolled. Dyslipidemias may also contribute to the high incidence of cardiovascular disease in patients with chronic kidney disease. This is most likely for patients with chronic renal insufficiency and for kidney transplant recipients. Less certain is the role of dyslipidemias in the pathogenesis of cardiovascular disease among dialysis patients.

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.

Endothelial chylomicron binding is altered by interaction with high-density lipoprotein in Heymann's nephritis

Very-low-density lipoprotein (VLDL) catabolism is impaired in the nephrotic syndrome, partly as a result of structural changes that impair endothelial binding in the presence of lipoprotein lipase. Previous results suggested that postsynthetic modification of VLDL by high-density lipoprotein (HDL) in nephrotic syndrome rats causes their failure to bind endothelia normally. It is unknown (1) whether the structure of secreted lipoproteins is normal before exposure to nephrotic syndrome serum and (2) whether the same structural or functional defects are imparted to chylomicrons (CMs) through their interaction with HDL from nephrotic syndrome rats. CMs were isolated from thoracic duct lymph from rats with passive Heymann's nephritis (HN) and normal controls. CMs from control rats were incubated with HDL from either HN or control rats and reisolated, and apolipoprotein E (apo E) content and endothelial binding were determined. We found that CMs secreted by HN and control rats had similar apo E/B-48 ratios. HDL from HN rats had significantly lower apo E/A-I ratios than controls. Incubation of nascent control CMs with control HDL resulted in a 4-fold increase in CM apo E content, but binding was unaffected. Incubation with HDL from HN resulted in only a 50% increase in CM apo E content but reduced binding of these treated CMs by 50% compared either with nascent control CMs or with CMs incubated with control HDL. HDL from rats with HN alters CM binding to lipoprotein lipase by a mechanism that does not involve reducing the content of apo E already present on CMs at the time of secretion.