Cellular mechanisms of lipid injury in the glomerulus

TYG Index as a Novel Predictor of Clinical Outcomes in Advanced Chronic Heart Failure with Renal Dysfunction Patients

Background

The triglyceride-glucose (TYG) index is a novel and reliable marker reflecting insulin resistance. Its predictive ability for cardiovascular disease onset and prognosis has been confirmed. However, for advanced chronic heart failure (acHF) patients, the prognostic value of TYG is challenged due to the often accompanying renal dysfunction (RD). Therefore, this study focuses on patients with aHF accompanied by RD to investigate the predictive value of the TYG index for their prognosis.

Methods and Results

717 acHF with RD patients were included. The acHF diagnosis was based on the 2021 ESC criteria for acHF. RD was defined as the eGFR < 90 mL/(min/1.73 m2). Patients were divided into two groups based on their TYG index values. The primary endpoint was major adverse cardiovascular events (MACEs), and the secondary endpoints is all-cause mortality (ACM). The follow-up duration was 21.58 (17.98-25.39) months. The optimal cutoff values for predicting MACEs and ACM were determined using ROC curves. Hazard factors for MACEs and ACM were revealed through univariate and multivariate COX regression analyses. According to the univariate COX regression analysis, high TyG index was identified as a risk factor for MACEs (hazard ratio = 5.198; 95% confidence interval [CI], 3.702-7.298; P < 0.001) and ACM (hazard ratio = 4.461; 95% CI, 2.962-6.718; P < 0.001). The multivariate COX regression analysis showed that patients in the high TyG group experienced 440.2% MACEs risk increase (95% CI, 3.771-7.739; P < 0.001) and 406.2% ACM risk increase (95% CI, 3.268-7.839; P < 0.001). Kaplan-Meier survival analysis revealed that patients with high TyG index levels had an elevated risk of experiencing MACEs and ACM within 30 months.

Conclusion

This study found that patients with high TYG index had an increased risk of MACEs and ACM, and the TYG index can serve as an independent predictor for prognosis.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

Solidified glomerulosclerosis, identified using single glomerular proteomics, predicts end-stage renal disease in Chinese patients with type 2 diabetes

Few histological prognostic indicators for end-stage renal disease (ESRD) have been validated in diabetic patients. This biopsy-based study aimed to identify nephropathological risk factors for ESRD in Chinese patients with type 2 diabetes. Histological features of 322 Chinese type 2 diabetic patients with biopsy-confirmed diabetic nephropathy (DN) were retrospectively analysed. Cox proportional hazards analysis was used to estimate the hazard ratio (HR) for ESRD. Single glomerular proteomics and immunohistochemistry were used to identify differentially expressed proteins and enriched pathways in glomeruli. During the median follow-up period of 24 months, 144 (45%) patients progressed to ESRD. In multivariable models, the Renal Pathology Society classification failed to predict ESRD, although the solidified glomerulosclerosis (score 1: HR 1.65, 95% confidence interval [CI] 1.04-2.60; score 2: HR 2.48, 95% CI 1.40-4.37) and extracapillary hypercellularity (HR 2.68, 95% CI 1.55-4.62) were identified as independent risk factors. Additionally, single glomerular proteomics, combined with immunohistochemistry, revealed that complement C9 and apolipoprotein E were highly expressed in solidified glomerulosclerosis. Therefore, solidified glomerulosclerosis and extracapillary hypercellularity predict diabetic ESRD in Chinese patients. Single glomerular proteomics identified solidified glomerulosclerosis as a unique pathological change that may be associated with complement overactivation and abnormal lipid metabolism.

Atherogenic dyslipidemia and diabetic nephropathy

Chronic kidney disease is associated with altered lipid metabolism and lipid accumulation. Although it is though that hyperlipemia is a consequence of kidney dysfunction, several lines of evidence support that hyperlipidemia may contribute to the onset and progression of kidney disease, also in diabetes. This review describes the results of recent observational studies supporting the concept that glucose is only partly responsible for kidney damage onset, while a cluster of factors, including hypertriglyceridemia and low HDL-cholesterol, could play a relevant role in inducing onset and progression of DKD. We also report the results of randomized clinical trials investigating in type 2 diabetic patients the role of drug improvement of hypertriglyceridemia on renal outcomes. Finally, we discuss putative mechanisms linking hyperlipidemia (i.e. hypertriglyceridemia or low HDL cholesterol) with kidney disease.

Effect of imidazoline-1 receptor agonists on renal dysfunction in rats associated with chronic, sequential fructose and ethanol administration

Insulin resistance and chronic alcoholism are risk factors for renal dysfunction. This study investigated the therapeutic effects of two imidazoline-1 receptor (I1R) agonists on renal dysfunction in rats after chronic, sequential fructose and ethanol administration. Daily drinking water was supplemented with fructose (10%, w/v) for 12 weeks and then with ethanol (20%, v/v) for another 8 weeks. Rats were treated with rilmenidine and clonidine in the last two weeks of the study. Blood glucose and serum insulin (sIns) levels, lipid profiles, kidney function and renal histopathology were evaluated at the end of the experiment. Additionally, renal gene expression of nischarin, phosphatidylcholine-specific phospholipase C (PC-PLC) and prostaglandin E2 (PGE2) were measured. Renal levels of superoxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS) and total NO (tNO) were detected, and we determined the relative renal gene expression levels of alpha smooth muscle actin (α-SMA), hydroxyproline, interleukin 10 (IL-10), tumour necrosis factor alpha (TNF-α) and caspase-3. The results showed significant deterioration of blood glucose, sIns, lipid profiles, kidney function and renal histopathology in fructose/ethanol-fed rats. Additionally, markers of inflammation, fibrosis, apoptosis and oxidative stress were upregulated. The administration of rilmenidine or clonidine significantly improved blood glucose and sIns levels and reduced renal dysfunction. Our work showed that chronic, sequential fructose and ethanol administration induced fasting hyperglycaemia and renal impairment, and these effects were ameliorated by I1R agonists.

Cardiovascular Disease and Diabetic Kidney Disease

Diabetic kidney disease commonly is associated with an increased risk of cardiovascular disease. There are traditional common risk factors for both conditions including hypertension and poor glycemic control. However, it is likely that there are other pathophysiological mechanisms that explain the clinical phenomenon of increased cardiovascular disease in diabetic patients with chronic kidney and vice versa. Current management of both conditions includes aggressive glucose and blood pressure control. The protective role of treating dyslipidemia has been shown for cardiovascular disease, but the results for renal disease are not as clear. The advent of new classes of glucose-lowering agents such as sodium glucose co-transporter2 inhibitors and glucagon-like peptide-1 agonists has resulted in impressive effects on both cardiovascular and renal disease in diabetes. However, how these drugs act independently of glucose lowering to confer both kidney and cardiovascular protection has not been fully elucidated. Nevertheless, these new treatments provide optimism for reducing both microvascular and macrovascular complications in diabetes, which represent the major causes of morbidity and premature mortality in this condition.

Treatment-resistant PLA2R-negative membranous nephropathy responsive to low-density lipoprotein apheresis

Idiopathic membranous nephropathy is the most common cause of nephrotic syndrome in nondiabetic adults. The antibody most often implicated is the M-type phospholipase A2 receptor (PLA2R) antibody, found in >70% of primary membranous nephropathy cases. First-line therapy is immunosuppressive in nature, but for patients who are treatment-resistant there is a significant risk of end-stage renal disease and mortality. Hypercholesterolemia is not only a side effect of nephrotic syndrome, but also its presence may worsen renal function. A recent single-arm observational study in Japan found that low-density lipoprotein apheresis (LDL-A) was able to ameliorate nephrotic syndrome in half of patients who were resistant to medication. We present a case of treatment resistant PLA2R negative membranous nephropathy who had significant improvement following two courses of LDL-A. To our knowledge, this is the first such reported case in the United States.

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.

Plasma Triglycerides and HDL-C Levels Predict the Development of Diabetic Kidney Disease in Subjects With Type 2 Diabetes: The AMD Annals Initiative

OBJECTIVE

Despite the achievement of blood glucose, blood pressure, and LDL cholesterol (LDL-C) targets, the risk for diabetic kidney disease (DKD) remains high among patients with type 2 diabetes. This observational retrospective study investigated whether diabetic dyslipidemia-that is, high triglyceride (TG) and/or low HDL cholesterol (HDL-C) levels-contributes to this high residual risk for DKD.

RESEARCH DESIGN AND METHODS

Among a total of 47,177 patients attending Italian diabetes centers, 15,362 patients with a baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m², normoalbuminuria, and LDL-C ≤130 mg/dL completing a 4-year follow-up were analyzed. The primary outcome was the incidence of DKD, defined as either low eGFR (<60 mL/min/1.73 m²) or an eGFR reduction >30% and/or albuminuria.

RESULTS

Overall, 12.8% developed low eGFR, 7.6% an eGFR reduction >30%, 23.2% albuminuria, and 4% albuminuria and either eGFR <60 mL/min/1.73 m² or an eGFR reduction >30%. TG ≥150 mg/dL increased the risk of low eGFR by 26%, of an eGFR reduction >30% by 29%, of albuminuria by 19%, and of developing one abnormality by 35%. HDL-C <40 mg/dL in men and <50 mg/dL in women were associated with a 27% higher risk of low eGFR and a 28% risk of an eGFR reduction >30%, with a 24% higher risk of developing albuminuria and a 44% risk of developing one abnormality. These associations remained significant when TG and HDL-C concentrations were examined as continuous variables and were only attenuated by multivariate adjustment for numerous confounders.

CONCLUSIONS

In a large population of outpatients with diabetes, low HDL-C and high TG levels were independent risk factors for the development of DKD over 4 years.

Lipid profile in pre-dialysis chronic kidney disease patients in southern Nigeria

BACKGROUND

Dyslipidaemia is one of the cardiovascular risk factors responsible for cardiovascular disease and rapid progression of chronic kidney disease (CKD) to end stage renal disease. Early detection and management of dyslipidaemia will reduce cardiovascular burden and retard progression of CKD.

AIMS

To determine the prevalence and pattern of dyslipidaemia in pre-dialysis CKD patients in a tertiary hospital in southern Nigeria.

METHODS

This was a case-control study that involved 105 consecutive pre-dialysis CKD patients recruited over two years and 105 age and sex matched control subjects. Data obtained from participants included demographics, body mass index, and aetiology of CKD. Blood sampling was done for the determination of creatinine and fasting serum lipids. P values < 0.05 were taken as significant.

RESULTS

The mean age of the CKD and control subjects were 46.98±16.81 and 47.57±15.97 years respectively with a male:female ratio of 1.7:1. The median atherogenic index of plasma (AIP), low density lipoprotein-cholesterol and triglyceride (TG) were significantly higher in the CKD patients while mean high density lipoprotein-cholesterol (HDL-C) was significantly lower in the CKD patients (p=<0.001). The overall prevalence of dyslipidaemia in the CKD patients was 60% which was significantly higher than 39% in the control (p=0.002). The prevalence of high AIP, elevated TG and reduced HDL-C increased with worsening renal function. Dyslipidaemia was commoner in female CKD patients (p=0.02) and those who were ≥ 45years (p=0.94).

CONCLUSION

Dyslipidaemia is common in pre-dialysis CKD especially in female and older patients. Some lipid abnormalities increased with worsening kidney function.

A Prospective Observational Survey on the Long-Term Effect of LDL Apheresis on Drug-Resistant Nephrotic Syndrome

BACKGROUND/AIMS

LDL apheresis (LDL-A) is used for drug-resistant nephrotic syndrome (NS) as an alternative therapy to induce remission by improvement of hyperlipidemia. Several clinical studies have suggested the efficacy of LDL-A for refractory NS, but the level of evidence remains insufficient. A multicenter prospective study, POLARIS (Prospective Observational Survey on the Long-Term Effects of LDL Apheresis on Drug-Resistant Nephrotic Syndrome), was conducted to evaluate its clinical efficacy with high-level evidence.

METHODS

Patients with NS who showed resistance to primary medication for at least 4 weeks were prospectively recruited to the study and treated with LDL-A. The long-term outcome was evaluated based on the rate of remission of NS 2 years after treatment. Factors affecting the outcome were also examined.

RESULTS

A total of 58 refractory NS patients from 40 facilities were recruited and enrolled as subjects of the POLARIS study. Of the 44 subjects followed for 2 years, 21 (47.7%) showed remission of NS based on a urinary protein (UP) level <1.0 g/day. The UP level immediately after LDL-A and the rates of improvement of UP, serum albumin, serum creatinine, eGFR, and total and LDL cholesterol after the treatment session significantly affected the outcome.

CONCLUSIONS

Almost half of the cases of drug-resistant NS showed remission 2 years after LDL-A. Improvement of nephrotic parameters at termination of the LDL-A treatment was a predictor of a favorable outcome.

APOL1 G1 genotype modifies the association between HDLC and kidney function in African Americans

Background

Despite evidence of an association between variants at the apolipoprotein L1 gene (APOL1) locus and a spectrum of related kidney diseases, underlying biological mechanisms remain unknown. An earlier preliminary study published by our group showed that an APOL1 variant (rs73885319) modified the association between high-density lipoprotein cholesterol (HDLC) and estimated glomerular filtration rate (eGFR) in African Americans. To further understand this relationship, we evaluated the interaction in two additional large cohorts of African Americans for a total of 3,592 unrelated individuals from the Howard University Family Study (HUFS), the Natural History of APOL1-Associated Nephropathy Study (NHAAN), and the Atherosclerosis Risk in Communities Study (ARIC). The association between HDLC and eGFR was determined using linear mixed models, and the interaction between rs73885319 genotype and HDLC was evaluated using a multiplicative term.

Results

Among individuals homozygous for the risk genotype, a strong inverse HDLC-eGFR association was observed, with a positive association in others (p for the interaction of the rs73885319 × HDLC =0.0001). The interaction was similar in HUFS and NHAAN, and attenuated in ARIC. Given that ARIC participants were older, we investigated an age effect; age was a significant modifier of the observed interaction. When older individuals were excluded, the interaction in ARIC was similar to that in the other studies.

Conclusions

Based on these findings, it is clear that the relationship between HDLC and eGFR is strongly influenced by the APOL1 rs73885319 kidney risk genotype. Moreover, the degree to which this variant modifies the association may depend on the age of the individual. More detailed physiological studies are warranted to understand how rs73885319 may affect the relationship between HDLC and eGFR in individuals with and without disease and across the lifespan.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1645-7) contains supplementary material, which is available to authorized users.

The role of platelet-activating factor in mesangial pathophysiology

Platelet-activating factor (PAF) is a powerful proinflammatory mediator that displays an exceedingly diverse spectrum of biological effects. Importantly, PAF is shown to participate in a broad range of pathologic conditions. This review focuses on the role that PAF plays specifically in the pathophysiology of the kidney, the organ that is both a source and a target of PAF. Renal mesangial cells are responsible for glomerular PAF generation and, ultimately, are the victims of its excessive production. Mesangial pathology is widely acknowledged to reflect glomerular damage, which culminates in glomerulosclerosis and proteinuria. Therefore, modulation of mesangial cell responses would offer a pathophysiology-based therapeutic approach to prevent glomerular injury. However, the currently available therapeutic modalities do not allow for targeted intervention into these processes. A more profound understanding of the mechanisms that govern PAF metabolism and signaling in mesangial cells is important, because it could facilitate the quest for improved therapies for renal patients on the basis of PAF as a drug target.

Focal Segmental Glomerular Sclerosis Ameliorated by Long-term Hemodialysis Therapy with Low-density Lipoprotein Apheresis

We report a case involving a 43-year-old Japanese woman with steroid-resistant focal segmental glomerular sclerosis (FSGS) and severe renal dysfunction, which was ameliorated by low-density lipoprotein apheresis (LDL-A). She had been treated with steroid therapy, but had experienced anuria for over 10 weeks and required hemodialysis. She was then treated with LDL-A, which resulted in improved urinary protein excretion and renal function. Her renal function recovered after 97 days of hemodialysis therapy. This case suggests that LDL-A may represent an effective rescue treatment in patients with FSGS and long-term anuria.

LDL-apheresis contributes to survival extension and renal function maintenance of severe diabetic nephropathy patients: a retrospective analysis

AIMS

Low-density lipoprotein (LDL)-apheresis removes various molecules including LDL/oxidized LDL and inflammatory cytokines and recovers clinical laboratory parameters. It is not yet known whether these advantages of LDL-apheresis improve the prognosis of patients with diabetic nephropathy accompanied by nephrotic syndrome.

METHODS

In this study, three groups of patients were retrospectively surveyed in a single center, and followed for approximately 3 years: an LDL-apheresis cohort (LDL-a; N = 20); a control cohort meeting the selection criterion of severe proteinuria ≥ 3g/24h (control-All; N = 55); and a subgroup of control-All with more severe proteinuria ≥ 5 g/24h (control-mSP; N = 10), and evaluated the outcomes as survival and renal dysfunction and death/renal dysfunction free rate.

RESULTS

Death/renal dysfunction free rate was significantly higher in LDL-a than control-All (χ(2) = 4.50; P = 0.03) and control-mSP (χ(2) = 27.68; P < 0.001).

CONCLUSION

These results suggest the possibilities which LDL-apheresis is considered to contribute to survival extension and renal function maintenance of severe diabetic nephropathy patients.

Cellular cholesterol transport proteins in diabetic nephropathy

Background

Lipid accumulation has been shown to accelerate renal injury, and the intracellular accumulation of lipids may be caused by alterations in synthesis as well as lipid uptake and efflux. We have investigated the role of cellular cholesterol transport proteins including adenosine triphosphate binding cassette transporter A1 (ABCA1), G1 (ABCG1) and scavenger receptor class B type I (SR-BI) in diabetic nephropathy.

Methods

Protein expression and the ability to mediate cholesterol efflux of ABCA1, ABCG1 and SR-BI was determined in human renal mesangial cells and proximal tubular epithelial cells cultured under normal or high glucose conditions. Renal expression of these cholesterol transporters was examined in a murine model of streptozotocin-induced type 1 diabetes.

Results

ABCA1, ABCG1 and SR-BI were expressed in both human renal mesangial cells and proximal tubular epithelial cells, and mediated cholesterol efflux to apolipoprotein AI and HDL. In vitro, hyperglycemia reduced the expression and the ability to mediate cholesterol efflux of all three cholesterol transporters (p<0.05). In vivo studies showed that intra-renal accumulation of lipids was increased in diabetic mice, particularly in mice with nephropathy. This was associated with a significant reduction in the expression of ABCA1, ABCG1 and SR-BI in the kidneys. These changes were already seen in diabetic mice without nephropathy and preceded the development of nephropathy. Diabetic mice with nephropathy had the lowest level of these cholesterol transporters.

Conclusion

Inducing diabetes with streptozotocin significantly reduced renal expression of ABCA1, ABCG1 and SR-BI. Defects in cholesterol export pathway in renal cells could therefore promote cholesterol accumulation and might contribute to the development of diabetic nephropathy.

Immediate therapeutic efficacy of low-density lipoprotein apheresis for drug-resistant nephrotic syndrome: evidence from the short-term results from the POLARIS Study

BACKGROUND

Hyperlipidemia is not merely a complication but a major exacerbating factor in longstanding nephrotic syndrome (NS). Low-density lipoprotein apheresis (LDL-A) has been reported to ameliorate dyslipidemia and induce rapid remission of NS. Several clinical studies have suggested the therapeutic efficacy of LDL-A, but the level of clinical evidence is insufficient. Therefore, a multicenter prospective study, POLARIS (Prospective Observational Survey on the Long-Term Effects of LDL Apheresis on Drug-Resistant Nephrotic Syndrome), was initiated in Japan.

METHOD

Patients with drug-resistant NS were prospectively recruited into the study and treated with LDL-A in facilities that were registered in advance. In the POLARIS study design, the clinical data are to be followed up for 2 years. In the current study, we aimed at evaluating the short-term efficacy based on the treatment outcome of LDL-A immediately after completion of treatment.

RESULTS

Along with rapid improvement of hyperlipidemia, LDL-A significantly improved proteinuria and hypoproteinemia after treatment. More than half of the patients showed remission of NS based on the urinary protein level at the completion of LDL-A. The duration of NS before the start of treatment was significantly shorter in patients who responded to LDL-A.

CONCLUSIONS

An analysis of patients registered in the POLARIS study indicated that LDL-A has short-term efficacy for drug-resistant NS. Rapid relief of dyslipidemia by LDL-A may provide early remission in about half of the NS patients who are resistant to conventional medication. Completion of the POLARIS study may reveal additional long-term effects of LDL-A in these patients.

A clinical study about contrast nephropathy: risk factors and the role of beta blockers

Objective:

There is still a group of patient that have unpredictable risk for the development of contrast nephropathy (CN). There is also an effort to find more effficient strategies to prevent CN. Carvedilol, metoprolol and nebivolol seem to have theoretical potentials for the prevention of CN. In this study, we aimed to investigate their effects on the prevention of CN. We also aimed to define the risk factors associated with the development of CN in our study group.

Methods:

In this prospective, cross-sectional study, the patients were divided into four groups according to whether they were taking 25 mg/day carvedilol (n:56), 5 mg/day nebivolol (n:60), 50 mg/day metoprolol (n:68) or none (n:63). We made analysis to determine the agents’ efficiency on the prevention of CN. We also performed multiple logistic regression analysis including all groups to define the risk factors associated with CN.

Results:

The incidents of CN were the lowest in the carvedilol group (4%) while the worst performance occurred in those taking metoprolol (10%). The difference between the groups in terms of the development of CN did not reach statistical significance (p>0.05). Multiple logistic regression analysis showed age (p=0.003), higher triglyceride levels (p=0.011) and family history of coronary artery disease (p=0.038) to be the predictors of CN.

Conclusion:

In this study, we didn’t find any relation between the development of CN and carvedilol, metoprolol or nebivolol usage. We found age, higher levels of triglyceride and family history of coronary artery disease to be risk factors for predicting CN.

Variation in APOL1 Contributes to Ancestry-Level Differences in HDLc-Kidney Function Association

Low levels of high-density cholesterol (HDLc) accompany chronic kidney disease, but the association between HDLc and the estimated glomerular filtration rate (eGFR) in the general population is unclear. We investigated the HDLc-eGFR association in nondiabetic Han Chinese (HC, n = 1100), West Africans (WA, n = 1497), and African Americans (AA, n = 1539). There were significant differences by ancestry: HDLc was positively associated with eGFR in HC (β = 0.13, P < 0.0001), but negatively associated among African ancestry populations (WA: -0.19, P < 0.0001; AA: -0.09, P = 0.02). These differences were also seen in nationally-representative NHANES data (among European Americans: 0.09, P = 0.005; among African Americans -0.14, P = 0.03). To further explore the findings in African ancestry populations, we investigated the role of an African ancestry-specific nephropathy risk variant, rs73885319, in the gene encoding HDL-associated APOL1. Among AA, an inverse HDLc-eGFR association was observed only with the risk genotype (-0.38 versus 0.001; P = 0.03). This interaction was not seen in WA. In summary, counter to expectation, an inverse HDLc-eGFR association was observed among those of African ancestry. Given the APOL1 × HDLc interaction among AA, genetic factors may contribute to this paradoxical association. Notably, these findings suggest that the unexplained mechanism by which APOL1 affects kidney-disease risk may involve HDLc.

Lipid profiles and oxidative stress parameters in male and female hemodialysis patients

To study atherogenesis markers in patients with stage 5D chronic kidney disease (CKD-5D) on hemodialysis to determine which parameters are modified and whether their behavior differ between male and female patients of similar age. Total cholesterol, triglycerides, glucose, total proteins, HDL-cholesterol, LDL-cholesterol, oxidative modification of low-density lipoprotein-cholesterol, autoantibodies against oxidized low-density lipoproteins-cholesterol, homocysteine (Hcy), folate, and vitamin B12 were measured in male and female controls and CKD-5D patients on hemodialysis for >6 months. The CKD-5D patients had significantly lower cholesterol, LDL-c and ox-LDL levels and significantly higher ox-LDL-AB and Hcy levels versus their respective controls. The reduction in ox-LDL in CKD patients does not imply a lower risk of atherosclerosis. In fact, the risk may be higher due to a greater capture of ox-LDL by macrophage scavenger receptors, which are increased in these patients. Elevated Hcy levels may also be a risk factor for atherosclerosis in male and female CKD-5D patients.

Increased class A scavenger receptor and glomerular lipid precede mesangial matrix expansion in the bGH mouse model

OBJECTIVE

Elevated neutral lipid content and mRNA expression of class A scavenger receptor (SRA) have been found in the renal cortex of the bovine growth hormone (bGH) mouse model of progressive glomerulosclerosis (GS). We hypothesize that the increased expression of SRA precedes glomerular scarring in this model.

DESIGN

Real time RT-PCR and immunofluorescence were employed to measure SRA and collagen types I and IV in the bGH transgenic and control mice at 5 and 12 weeks (wk) of age to determine the chronology of change in SRA expression in relation to glomerular scarring. Alternative mechanisms for increasing glomerular lipid were assessed by measuring mRNA expression levels of low-density lipoprotein receptor (LDL-r), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and ATP-binding cassette transporter A1 (ABCA1). In addition, the involvement of macrophages in early GS was assessed by CD68 mRNA expression in kidney cortex.

RESULTS

Both mRNA and protein levels of SRA were significantly increased in 5-wk bGH compared with control mice, whereas the expression of collagen I and IV was unaltered. Unchanged levels of LDL-r and HMGR mRNA indicate that neither regulated cholesterol uptake via LDL-r nor the cholesterol synthetic pathway played a role in the early lipid increase. The finding of increased ABCA1 expression was an indicator of excess intracellular lipid in the renal cortex of bGH mice at 5 wk. CD68 expression in bGH did not differ significantly from that of controls at 5 wk suggesting that cortical macrophage infiltration was not increased in bGH mice at this time point.

CONCLUSION

An early increase in SRA mRNA and protein expression in the bGH kidney precedes glomerular scarring and is independent of macrophage influx.

Tumor Necrosis Factor–Like Weak Inducer of Apoptosis (TWEAK) Enhances Vascular and Renal Damage Induced by Hyperlipidemic Diet in ApoE-Knockout Mice

Objective— Tumor necrosis factor–like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily of cytokines. TWEAK binds and activates the Fn14 receptor, and may regulate apoptosis, inflammation, and angiogenesis, in different pathological conditions. We have evaluated the effect of exogenous TWEAK administration as well as the role of endogenous TWEAK on proinflammatory cytokine expression and vascular and renal injury severity in hyperlipidemic ApoE-knockout mice.

Methods and Results— ApoE −/− mice were fed with hyperlipidemic diet for 4 to 10 weeks, then randomized and treated with saline (controls), TWEAK (10 μg/kg/d), anti-TWEAK neutralizing mAb (1000 μg/kg/d), TWEAK plus anti-TWEAK antibody (10 μg TWEAK +1000 μg anti-TWEAK/kg/d), or nonspecific IgG (1000 μg/kg/d) daily for 9 days. In ApoE −/− mice, exogenous TWEAK administration in ApoE −/− mice induced activation of NF-κB, a key transcription factor implicated in the regulation of the inflammatory response, in vascular and renal lesions. Furthermore, TWEAK treatment increased chemokine expression (RANTES and MCP-1), as well as macrophage infiltration in atherosclerotic plaques and renal lesions. These effects were associated with exacerbation of vascular and renal damage. Conversely, treatment of ApoE −/− mice with an anti-TWEAK blocking mAb decreased NF-κB activation, proinflammatory cytokine expression, macrophage infiltration, and vascular and renal injury severity, indicating a pathological role for endogenous TWEAK. Finally, in murine vascular smooth muscle cells or tubular cells, either ox-LDL or TWEAK treatment increased expression and secretion of both RANTES and MCP-1. Furthermore, ox-LDL and TWEAK synergized for induction of MCP-1 and RANTES expression and secretion.

Conclusion— Our results suggest that TWEAK exacerbates the inflammatory response associated with a high lipid–rich diet. TWEAK may be a novel therapeutic target to prevent vascular and renal damage associated with hyperlipidemia.

Effects of different LDL particles on inflammatory molecules in human mesangial cells

AIMS/HYPOTHESIS

Inflammation is a mechanism of glomerular damage in chronic glomerulopathies. LDL may increase the production of inflammatory cytokines in renal tissues. However, the relative role of native, oxidised and glycated LDL in promoting this process has been only partially elucidated.

METHODS

We tested the inflammatory and proapoptotic effects of native, oxidised and glycated LDL in human mesangial cells (HMCs) by measuring levels of IL6, CD40 and macrophage migration inhibitory factor (MIF) genes, MIF protein, release of IL6, soluble CD40, fibronectin and laminin, early and late apoptosis, and extracellular regulated kinases (ERK) 1/2 and c-Jun N-terminal kinase (JNK) activation.

RESULTS

IL6 and CD40 mRNA were dose-dependently upregulated by all three species; this was closely paralleled by their increased release. MIF mRNA was potently stimulated by modified LDL, as confirmed by immunostaining. Fibronectin and laminin release was stimulated by both oxidised and glycated, but not native, LDL. All LDL species induced some increase in late, but not early, apoptosis, and similarly activated JNK2/3 phosphorylation; in contrast, ERK1/2 phosphorylation was more strongly upregulated by oxidised than either native or glycated LDL.

CONCLUSIONS

In HMCs, the production and release of IL6 and CD40 is stimulated by both native and modified LDL, while MIF is more strongly stimulated by oxidised LDL. Regarding the pattern of mesangial expansion, fibronectin and laminin are upregulated by oxidised and glycated LDL. Apoptosis, if modest, is induced by all species. Intracellular signalling of native and modified LDL involves JNK2/3 and, perhaps more specifically, ERK1/2. Tight control of the lipid profile may be useful in preserving kidney function in patients with metabolic alterations.

Lipids and diabetic nephropathy

Although several factors may mediate the development and progression of diabetic nephropathy, hyperlipidemia is now considered an independent and major determinant of progression of renal disease in diabetes. The following discussion focuses on the experimental evidence that incriminates hyperlipidemia as a pathogenic factor for diabetic nephropathy and the potential mechanisms that may mediate renal injury from hyperlipidemia, as well as the clinical studies involving therapeutic interventions for hyperlipidemia and their impact on progression of diabetic renal disease.

Effect of low-density lipoprotein apheresis on urinary protein and podocyte excretion in patients with nephrotic syndrome due to diabetic nephropathy

BACKGROUND

The aim of the present study is to determine whether low-density lipoprotein (LDL) apheresis affects proteinuria and urinary podocyte excretion in patients with type 2 diabetes and nephrotic syndrome.

METHODS

LDL apheresis was performed on patients with diabetes with long-standing nephrotic syndrome, and urinary protein level and number of urinary podocytes were compared between these patients (5 men, 3 women; mean age, 54.6 years) and 10 nephrotic patients with diabetes not treated with LDL apheresis (6 men, 4 women; mean age, 56.5 years).

RESULTS

LDL apheresis reduced total cholesterol (P < 0.001), LDL cholesterol ( P < 0.001), lipoprotein(a) (P < 0.001), creatinine (P < 0.05), and blood urea nitrogen (P < 0.05) levels and increased creatinine clearance (P < 0.05). The LDL apheresis group showed a significant decrease in urinary protein excretion (from 10.8 +/- 3.2 to 1.8 +/- 1.1 g/d; P < 0.001) and number of urinary podocytes (from 4.8 +/- 2.2 to 0.9 +/- 0.4 cells/mL; P < 0.01).

CONCLUSION

These data suggest that LDL apheresis effectively reduces proteinuria and podocyte excretion, ameliorating renal dysfunction in patients with nephrotic syndrome caused by diabetic nephropathy.

Catabolism of native and oxidized low density lipoproteins: in vivo insights from small animal positron emission tomography studies

The human organism is exposed to numerous processes that generate reactive oxygen species (ROS). ROS may directly or indirectly cause oxidative modification and damage of proteins. Protein oxidation is regarded as a crucial event in the pathogenesis of various diseases ranging from rheumatoid arthritis to Alzheimer's disease and atherosclerosis. As a representative example, oxidation of low density lipoprotein (LDL) is regarded as a crucial event in atherogenesis. Data concerning the role of circulating oxidized LDL (oxLDL) in the development and outcome of diseases are scarce. One reason for this is the shortage of methods for direct assessment of the metabolic fate of circulating oxLDL in vivo. We present an improved methodology based on the radiolabelling of apoB-100 of native LDL (nLDL) and oxLDL, respectively, with the positron emitter fluorine-18 ((18)F) by conjugation with N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). Radiolabelling of both nLDL and oxLDL using [(18)F]SFB causes neither additional oxidative structural modifications of LDL lipids and proteins nor alteration of their biological activity and functionality, respectively, in vitro. The method was further evaluated with respect to the radiopharmacological properties of both [(18)F]fluorobenzoylated nLDL and oxLDL by biodistribution studies in male Wistar rats. The metabolic fate of [(18)F]fluorobenzoylated nLDL and oxLDL in rats in vivo was further delineated by dynamic positron emission tomography (PET) using a dedicated small animal tomograph (spatial resolution of 2 mm). From this study we conclude that the use of [(18)F]FB-labelled LDL particles is an attractive alternative to, e.g., LDL iodination methods, and is of value to characterize and to discriminate the kinetics and the metabolic fate of nLDL and oxLDL in small animals in vivo.

The role of cholesterol on the pressure sensing ability of kidneys in rats

We studied the effect of hypercholesterolemia on the pressure-sensing and regulating ability of the kidneys, using an acute hemorrhage model to provide 40% and 60% reduction in the blood pressure of hypercholesterolemic and control rats. The control group (n = 22) was fed a normal rat pellet diet and tap water; the experimental group (n = 22) received a diet containing 2% cholesterol/0.2% thaurocholate. Half the animals were subjected to 6 mL/kg bw and the others to 12 mL/kg bw of bleeding for 1 min. Blood pressure recording and proper samplings were done before bleeding and during the 20 min post-hemorrhagic period for analysis. Despite a finding of hypercholesterolemia in the experimental group, kidney cholesterol content as well as its function remained unchanged. Following an initial 40% decrease in rats bled 6 mL/kg bw, 20 min later the mean blood pressure returned to 90% of its initial value in control rats and to 70% of its basal level in hypercholesterolemic rats. A similar delay in pressure normalization occurred in rats subjected to 12 mL/kg of bleeding. Plasma renin activity remained unaffected. We conclude that dietary hypercholesterolemia delays the normalization of blood pressure after hemorrhage without affecting the sensing ability of kidneys, and that the kidneys are less sensitive than other organs to plasma cholesterol levels.

Resolution of typical lipoprotein glomerulopathy by intensive lipid-lowering therapy

Lipoprotein glomerulopathy (LPG), characterized by glomerular lipoprotein thrombi, presumably composed of abnormal apolipoprotein E (apoE), leads to a progressive decline in renal function and eventually results in end-stage renal failure. A successful treatment for LPG has not yet been established. The authors treated a 36-year-old woman with LPG and exhibiting a nephrotic syndrome using an intensive lipid-lowering therapy consisting of fenofibrate (300 mg), niceritrol (750 mg), ethyl-icosapentate (1,800 mg), and probucol (500 mg). After the start of treatment, a remarkable decrease in urinary protein excretion and improvement in the hyperlipidemia were obtained; proteinuria was no longer detected 11 months after the initiation of treatment. A second biopsy performed 11 months after the initiation of treatment showed the complete disappearance of the lipoprotein thrombi that had been observed in a diffuse and global manner in the first renal biopsy. These findings suggest that typical LPG could be regressed if the abnormal lipoproteinemia is controlled sufficiently.

A case of nephrotic syndrome due to lupus nephritis which was controlled with low-density lipoprotein apheresis

Our report discusses a 29 year old female patient with nephrotic syndrome due to lupus nephritis, biopsy-proven World Health Organization classification Types IVb and V that was controlled with low-density lipoprotein (LDL) apheresis. She was initially treated with steroid therapy, including methylprednisolone pulse therapy, and the serological activity of her systemic lupus erythematosus was suppressed. However, her nephrotic state, accompanied by severe hyperlipidemia, persisted despite the steroid therapy. Since we could not obtain her consent to administer immunosuppressants such as cyclophosphamide, we tried to treat her using LDL apheresis (LDL-A). We found that her urine protein excretion, hyperlipidemia, hypoalbuminemia, and renal function improved following the initiation of LDL-A. This suggests that LDL-A may be an effective therapy for nephrotic syndrome due to lupus nephritis through short-term amelioration of hyperlipidemia.

Association between plasma oxidized low-density lipoprotein and diabetic nephropathy

To investigate the association of oxidized low-density lipoprotein (ox-LDL) with the development of diabetic nephropathy, plasma levels of ox-LDL were measured in 70 patients with type 2 diabetes mellitus. A sandwich enzyme-linked immunoadsorbent assay (ELISA) using the mouse monoclonal antibody FOH1a/DLH3, which specifically recognizes oxidized phosphatidylcholine, and a horseradish peroxidase (HRP)-labeled goat anti-human apolipoprotein B IgG was used to measure ox-LDL levels. The mean age of the patients was 57.0+/-1 3.4 years, and the mean duration of diabetes was 13.4+/-8.5 years. Plasma ox-LDL levels were similar in patients with normoalbuminuria (13.7+/-3.9 U/ml), patients with microalbuminuria (12.8+/-3.9 U/ml), and normal controls (12.5+/-4.2 U/ml). However, the plasma ox-LDL level in patients with macroalbuminuria (16.8+/-7.5 U/ml) was significantly higher than those in the other groups (P<0.05). Hemoglobin A1c (HbA1c) levels were similar in diabetic patients with normoalbuminuria (8.2+/-2.2%), microalbuminuria (7.8+/-1.3%), or macroalbuminuria (7.2+/-1.4%). There was no significant correlation between the ox-LDL level and the HbA1c level. The significantly elevated plasma ox-LDL levels in patients with macroalbuminuria suggest that ox-LDL may play an important role in the progression of diabetic nephropathy.

Monohydroxylated fatty acid content in peripheral blood mononuclear cells and immune status of people at long times after the Chernobyl accident

The monohydroxylated fatty acid content of peripheral blood mononuclear cells from 23 cleanup workers and 16 unexposed individuals was studied in relation to their immune status after the Chernobyl accident. Men with absorbed doses below 0.32 Gy showed higher levels of free and esterified 12-hydroxyeicosatetraenoic acid (12-HETE) than unexposed men, whereas 15-HETE and the 17-hydroxy derivative of C22 fatty acid (17-OH 22), either free or esterified in phospholipids, were increased in a dose-dependent manner. The percentage of CD4-positive cells was also increased significantly in heavily irradiated men, whereas the percentage of CD8-positive cells tended to decrease with dose. Furthermore, the absolute count of CD4-positive cells was correlated positively with the amount of esterified 15-HETE in the phospholipid fraction of the mononuclear cells and with the total 15-HETE. These results show for the first time that the accumulation of autoxidized/lipoxygenase products of polyunsaturated fatty acids in the mononuclear cells of irradiated individuals was associated with immune imbalance. This may be the basis for certain late effects of radiation such as autoimmune disorders, somatic and neoplastic diseases, and early aging.

Activation of MAPK by modified low-density lipoproteins in vascular smooth muscle cells

A high concentration of circulating low-density lipoproteins (LDL) is a major risk factor for atherosclerosis. Native LDL and LDL modified by glycation and/or oxidation are increased in diabetic individuals. LDL directly stimulate vascular smooth muscle cell (VSMC) proliferation; however, the mechanisms remain undefined. The extracellular signal-regulated kinase (ERK) pathway mediates changes in cell function and growth. Therefore, we examined the cellular effects of native and modified LDL on ERK phosphorylation in VSMC. Addition of native, mildly modified (oxidized, glycated, glycoxidized) and highly modified (highly oxidized, highly glycoxidized) LDL at 25 microg/ml to rat VSMC for 5 min induced a fivefold increase in ERK phosphorylation. To elucidate the signal transduction pathway by which LDL phosphorylate ERK, we examined the roles of the Ca(2+)/calmodulin pathway, protein kinase C (PKC), src kinase, and mitogen-activated protein kinase kinase (MEK). Treatment of VSMC with the intracellular Ca(2+) chelator EGTA-AM (50 micromol/l) significantly increased ERK phosphorylation induced by native and mildly modified LDL, whereas chelation of extracellular Ca(2+) by EGTA (3 mmol/l) significantly reduced LDL-induced ERK phosphorylation. The calmodulin inhibitor N-(6-aminohexyl)-1-naphthalenesulfonamide (40 micromol/l) significantly decreased ERK phosphorylation induced by all types of LDL. Downregulation of PKC with phorbol myristate acetate (5 micromol/l) markedly reduced LDL-induced ERK phosphorylation. Pretreatment of VSMC with a cell-permeable MEK inhibitor (PD-98059, 40 micromol/l) significantly decreased ERK phosphorylation in response to native and modified LDL. These findings indicate that native and mildly and highly modified LDL utilize similar signaling pathways to phosphorylate ERK and implicate a role for Ca(2+)/calmodulin, PKC, and MEK. These results suggest a potential link between modified LDL, vascular function, and the development of atherosclerosis in diabetes.

Hyperphagia as a mediator of renal disease initiation in obese Zucker rats

OBJECTIVE

We sought to determine whether prevention of overeating would block the very earliest manifestations of renal injury in young obese Zucker rats (OZRs).

RESEARCH METHODS AND PROCEDURES

Three groups of rats were studied, obese (fa/fa) Zucker rats and lean (Fa/Fa). Zucker controls were allowed to feed ad libitum, whereas a group of obese (fa/fa) Zucker rats was pair-fed to the lean group. Urine albumin and serum lipids were studied weekly from 6 to 10 weeks of age. Renal pathology and renal glomerular gene expression were examined when the rats were killed at 10 weeks of age.

RESULTS

Obese rats fed ad libitum developed significant albuminuria by 6 weeks of age, increasing at each subsequent time-point. This increase was completely blocked by pair-feeding. Serum triglycerides were significantly increased in obese rats fed ad libitum vs. the other groups. Urine albumin correlated significantly with both body weight and serum triglyceride level. Renal histopathology was normal in all groups. Analysis of gene expression of glomerular proteins by reverse transcriptase-polymerase chain reaction revealed that pair-feeding attenuated the increased expression of glomerular desmin, fibronectin, and the 92-kDa collagenase that was seen in obese animals fed ad libitum.

DISCUSSION

Prevention of overeating in young OZR normalizes albuminuria and attenuates the pathogenic alterations in glomerular gene expression seen at the initiation of renal disease in obese animals allowed to feed ad libitum. This model may be relevant for studying the early end-organ effects of obesity.

Lipoprotein-stimulated mesangial cell proliferation and gene expression are regulated by lipoprotein lipase

BACKGROUND

Hyperlipidemia accelerates the progression of glomerular disease, and lipoproteins bind glomerular mesangial cells (MC) and induce proliferation and cytokine expression. In the vessel wall, the binding of lipoproteins to endothelial cells is markedly enhanced by lipoprotein lipase (LpL), synthesized by the underlying smooth muscle cells. While it is known that LpL is localized to the glomerulus, it is not known if and how it modulates the lipoprotein-mesangial interaction.

METHODS

Very low-density lipoprotein (VLDL) was isolated from rats and was used to treat cultured primary rat MCs. Binding studies were done with and without LpL and with/without pretreatment with heparanase, which degrades cell surface heparan sulfate proteoglycan (HSPG), known to modulate the LpL-lipoprotein interaction in blood vessels. VLDL/LpL was also used to assess MC proliferation and gene expression of the cytokine platelet-derived growth factor (PDGF).

RESULTS

LpL enhanced VLDL binding to MCs by as much as 200-fold, and most of this effect was blocked by pretreatment with heparanase. LpL amplified VLDL-driven MC proliferation and increased VLDL-induced PDGF expression. Heparanase pretreatment of cells eliminated both of these amplifications. LpL alone increased MC proliferation and PDGF gene expression.

DISCUSSION

As in the vessel wall, LpL enhances VLDL binding to MCs. MCs respond to LpL binding by proliferating and expressing cytokines such as PDGF. LpL may be a crucial paracrine mediator of the glomerular response to circulating lipoproteins, amplifying a response that includes cytokine elaboration, influx of circulating monocytes, and eventual sclerosis.

Effects of dietary polyunsaturated fatty acid supplementation in early renal insufficiency in dogs

Dietary supplementation with polyunsaturated fatty acids (PUFAs) alters the course of experimental kidney disease in dogs. In particular, supplementation with omega-6 PUFAs hastens the decline of kidney function, and omega-3 PUFAs are renoprotective. We investigated the early stages of renal insufficiency to determine whether PUFA supplementation altered the magnitude of hypercholesterolemia or glomerular hemodynamics. Two months after 11/12 nephrectomy, dogs were randomly divided into three groups of 6 animals each. Each group of dogs was then fed a low-fat basal diet supplemented with one of three sources of lipid to achieve a final concentration of 15% added fat. Fat sources were rich in omega-3 PUFAs (menhaden fish oil, group FO), omega-6 PUFAs (safflower oil, group SO), or saturated fatty acids (beef tallow, group C). Early in renal insufficiency, before significant kidney damage, group FO had a lower (P<.05) serum cholesterol concentration and tended to have a lower urinary prostaglandin E2 (PGE2) and thromboxane A2 (TxA2) excretion than group C. In contrast, group SO had a higher mean glomerular capillary pressure (P<.05) and more glomerular enlargement (P<.05) and tended to have higher eicosanoid excretion rates than group C. These differences in lipid metabolism, glomerular hypertension and hypertrophy, and urinary eicosanoid metabolism could explain, in part, the beneficial effects of omega-3 PUFAs and the detrimental effects of omega-6 PUFAs when administered on a long-term basis in this model of renal insufficiency.

Diabetic nephropathy: what causes to treat?

In summary, diabetic nephropathy is characterized by a multifactorial disease process. The present survey points to several factors that are treatable by available drugs. We must now consider prophylactic treatment of patients with poor metabolic control not only to lower blood glucose levels, but also to protect against the harmful effects of glucose. ACE inhibitors and several other available drugs have such effects.

Lipoprotein (a) stimulates mitogen activated protein kinase in human mesangial cells

Evidence suggests an important role of elevated serum lipoproteins in the progression of renal glomerulosclerosis. We report here that lipoprotein (a) (Lp(a)) increased phosphorylation and activity of mitogen activated protein kinase (MAPK) in human mesangial cells. When protein kinase C (PKC) was depleted by long-term incubation with the phorbol 12-O-myristate 13-acetate the effect of Lp(a) on MAPK activation was completely inhibited. Forskolin, a stimulator of the adenylyl cyclase, and dibutyryl-cAMP reduced the effect of Lp(a) on MAPK phosphorylation and activation. We conclude that Lp(a) stimulates the MAPK cascade via activation of PKC and that activation of protein kinase A counteracts Lp(a) induced MAPK activation in human mesangial cells.

Interstitial fibrosis in hypercholesterolemic rats: role of oxidation, matrix synthesis, and proteolytic cascades

Uninephrectomized rats with diet-induced hypercholesterolemia develop interstitial inflammation and fibrosis after 8 to 12 weeks. Fibrosis has been associated with the accumulation of lipid peroxidation products within the tubulointerstitium, along with increased renal mRNA levels for transforming growth factor beta-1 (TCF-beta 1), some matrix proteins, and the tissue inhibitor of metalloproteinases (TIMP-1). However, mRNA levels for urokinase-type plasminogen activator (uPA) have been found to be decreased. The purpose of the present study was to determine whether antioxidant therapy could attenuate interstitial fibrosis in hypercholesterolemic rats and to determine changes in the pattern of renal gene expression induced by antioxidant therapy. Three groups of uninephrectomized rats were studied after 12 weeks of feeding standard rat chow, an atherogenic diet (standard chow plus 4% cholesterol/1% cholic acid), or an atherogenic diet supplemented with high doses of the antioxidants probucol and vitamin E. Rats fed the atherogenic diet developed hypercholesterolemia and a 56% increase in total kidney collagen compared with rats fed standard chow. In comparison, the hypercholesterolemic rats treated with antioxidants had normal levels of renal lipid peroxidation products and a normal kidney collagen content. In contrast, there were no significant differences in urinary albumin excretion rates or the number of interstitial macrophages between the two hypercholesterolemic groups. Compared with the untreated hypercholesterolemic group, antioxidant therapy induced significant reductions in renal mRNA levels for procollagen III (to 60% of untreated levels), collagen IV (60%), and TIMP-1 (20%), while uPA levels were significantly increased (to 210%). Paradoxically, antioxidant therapy was associated with a significant increase in renal TGF-beta 1 mRNA levels (to 150%), although TGF-beta 1 protein expression shifted from interstitial to tubular epithelial cells in predominance. The results of the present study demonstrate the efficiency of antioxidant therapy in preventing renal interstitial fibrosis in hypercholesterolemic rats with a single kidney. Based on changes in renal gene expression at the mRNA level, impaired matrix protein synthesis and increased intrarenal activity of the metalloproteinases and uPA/plasmin may play a role in the attenuation of fibrosis.

Preeclamptic nephropathy -- an endothelial lesion. A morphological study with a review of the literature

OBJECTIVE

We investigated wether an endothelial lesion, postulated in pathogenesis of preeclampsia (PE) in general, is also pathogenetically relevant in the characteristic renal lesions of PE, presenting as special glomerular alterations, designated as "preeclamptic nephropathy".

STUDY DESIGN

Renal biopsies of 90 women with PE were analyzed by light microscopy (LM), immunohistology (IH) and electron microscopy (EM). Corresponding with clinical data clinicomorphological correlations were performed.

RESULTS

In IH and EM the altered glomeruli demonstrate an endothelial lesion. Consecutive morphological reactions could be revealed by EM, allowing a subdivision in different stages of disease. The late stage indicates the reversibility of these renal lesions. Close correlations were found between clinical and morphological data. Focal glomerulosclerosis presents a hyperperfusion lesion, developing only facultatively in PE as a result of hyperfiltration.

CONCLUSION

In preeclamptic nephropathy the first morphological substrate of renal changes with the key to pathogenesis presents itself as an endothelial lesion. This results in a disturbance of glomerular basement membrane permeability and in an imbalance of different mediator systems, with dominance of vasoconstrictive reactions but also coagulative-, reparation-, and proliferation-processes, leading to the characteristic glomerular alterations of preeclamptic nephropathy.

Differential ability of cells to promote oxidation of low density lipoproteins in vitro

Atherosclerosis and focal segmental glomerulosclerosis share some common histological features and it is speculated that they result from similar pathobiological mechanisms. There is strong evidence that oxidation of low density lipoprotein (LDL) may be an initiating event in atherogenesis and that oxidised LDL may also be involved in the glomerulosclerotic process. In vitro studies have demonstrated that cells present in the arterial intima and kidney-derived cells promote LDL oxidation. The aim of this study was to compare LDL oxidation by kidney-derived human mesangial cells and proximal tubular cells, with human umbilical vein endothelial cells and the human monocyte cell line THP-1. We used the thiobarbituric acid assay and agarose gel electrophoresis to measure the extent of LDL oxidation. Our results demonstrate that all of the cell types used had the ability to oxidise LDL significantly more than cell-free controls and that endothelial cells induced the highest degree of oxidative modification of LDL under our experimental conditions.

Uptake and metabolism of lipoprotein-X in mesangial cells

Progressive glomerulosclerosis is a major complication in patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency. The lack of LCAT activity results in the accumulation of an abnormal lipoprotein, lipoprotein-X (Lp-X), in the plasma of these patients. Lipoprotein-X contains high levels of unesterified cholesterol and phosphatidylcholine. Lp-X may play a role in the accumulation of lipids in the kidney, which in turn may lead to glomerulosclerosis. The objective of this study is to examine the uptake and metabolism of Lp-X by rat mesangial cells. Our results suggest that Lp-X is taken up by mesangial cells and that the lipids in Lp-X are metabolized. Lysosomes containing unesterified cholesterol and phosphatidylcholine, in a molar ratio similar to Lp-X, were synthesized to investigate the roles individual apolipoproteins (apo CI, II, III and E) play in the uptake of Lp-X. Both apo CI and CIII inhibited its uptake while apo CII (1.5 fold) and E (4 fold) stimulated the uptake of Lp-X. Very low density lipoprotein (VLDL) and low density lipoprotein (LDL) inhibited Lp-X uptake by mesangial cells. However, at higher concentrations of high density lipoprotein (HDL), the uptake of Lp-X was stimulated. Proteoglycans have an important role in regulating the uptake of Lp-X, while cytoskeleton-dependent phagocytosis and the scavenger receptor do not appear to be involved.