HDL metabolism and activity in chronic kidney disease

HDL Cholesterol Level Is Associated with Contrast Induced Acute Kidney Injury in Chronic Kidney Disease Patients Undergoing PCI

Chronic kidney disease (CKD) is a significant risk factor for contrast induced acute kidney injury (CI-AKI) after percutaneous coronary intervention (PCI). This study included 1592 CKD patients extracted from a prospective multicenter, all comer-based registry of patients undergoing PCI. In multivariate logistic analysis for CI-AKI development, a significant linear trend was observed between the quartiles of HDL-C (quartile 1 vs. 2: odds ratio [OR], 0.716; 95% confidence interval [CI], 0.421-1.219; quartile 1 vs. 3: OR, 0.534; 95% CI, 0.301-0.947; quartile 1 vs. 4: OR, 0.173; 95% CI, 0.079-0.377; P for trend < 0.001). HDL-C quartiles were also negatively correlated with the incidence of CI-AKI; 19.0%, 12.1%, 8.7%, and 3.7% for quartile 1(Q1) (<34 mg/dL), Q2 (34-40 mg/dL), Q3 (40-48 mg/dL), and Q4 (>48 mg/dL) respectively (P < 0.001 overall and for the trend). Multivariate Cox regression analysis for the long term mortality, the highest HDL-C quartile was associated with decreased mortality compared with the lowest HDL-C quartile (hazard ratio [HR] 0.516, 95% CI, 0.320-0.832, P = 0.007). Our study suggests more intensive strategies should be considered for preventing CI-AKI in CKD patients with low serum HDL-C level who is planned for PCI.

High Density Lipoprotein Cholesterol and the Risk of All-Cause Mortality among U.S. Veterans

BACKGROUND AND OBJECTIVES

The relationship between HDL cholesterol and all-cause mortality in patients with kidney disease is not clear. We sought to characterize the relationship of HDL cholesterol and risk of death and examine the association by eGFR levels.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We built a cohort of 1,764,986 men who were United States veterans with at least one eGFR between October of 2003 and September of 2004 and followed them until September of 2013 or death.

RESULTS

Patients with low HDL cholesterol and low eGFR had a higher burden of comorbid illnesses. Over a median of 9.1 years (interquartile range, 7.7-9.4 years), 26,247 (40.1%), 109,222 (32.3%), 152,625 (29.2%), 113,785 (28.5%), and 139,803 (31.8%) participants with HDL cholesterol ≤25, >25 to <34, ≥34 to ≤42, >42 to <50, and ≥50 mg/dl died. In adjusted survival models, compared with the referent group of patients with low HDL cholesterol (≤25 mg/dl), intermediate HDL cholesterol levels (>25 to <34, ≥34 to ≤42, and >42 to <50 mg/dl) were associated with lower risk of death across all levels of eGFR. The lower risk was partially abrogated in those with high HDL cholesterol (≥50 mg/dl), and the risk of death was similar to the referent category among those with eGFR<30 or ≥90 ml/min per 1.73 m2. Analysis by HDL cholesterol deciles and spline analyses suggest that the relationship between HDL cholesterol and death follows a U-shaped curve. There was a significant interaction between eGFR and HDL cholesterol in that lower eGFR attenuated the salutary association of HDL cholesterol and risk of death (P for interaction <0.01). Presence of coronary artery disease attenuated the lower risk of high HDL cholesterol and all-cause mortality in those with eGFR≥60 ml/min per 1.73 m2 (P for interaction <0.05).

CONCLUSIONS

Our results show a U-shaped relationship between HDL cholesterol and risk of all-cause mortality across all eGFR categories. The risk is modified by eGFR and cardiovascular disease.

An integrated lipidomics and metabolomics reveal nephroprotective effect and biochemical mechanism of Rheum officinale in chronic renal failure

Chronic renal failure (CRF) is a major public health problem worldwide. Earlier studies have revealed salutary effects of rhubarb extracts in CRF. In this study, we employed lipidomic and metabolomic approaches to identify the plasma biomarkers and to determine the effect of treatment with petroleum ether, ethyl acetate and n-butanol extracts of rhubarb in a rat model of CRF with adenine-induced chronic tubulointerstitial nephropathy. In addition, clinical biochemistry, histological evaluation and pro-fibrotic protein expression were analyzed. Significant changes were found between the CRF and control groups representing characteristic phenotypes of rats with CRF. Treatment with the three rhubarb extracts improved renal injury and dysfunction, either fully or partially reversed the plasma metabolites abnormalities and attenuated upregulation of pro-fibrotic proteins including TGF-β1, α-SMA, PAI-1, CTGF, FN and collagen-1. The nephroprotective effect of ethyl acetate extract was better than other extracts. The differential metabolites were closely associated with glycerophospholipid, fatty acid and amino acid metabolisms. The results revealed a strong link between renal tubulointerstitial fibrosis and glycerophospholipid metabolism and L-carnitine metabolism in the development of CRF. Amelioration of CRF with the three rhubarb extracts was associated with the delayed development and/or reversal the disorders in key metabolites associated with adenine-induced CRF.

Low levels of high-density lipoprotein cholesterol increase the risk of incident kidney disease and its progression

Available experimental evidence suggests a role for high-density lipoprotein cholesterol (HDL-C) in incident chronic kidney disease (CKD) and its progression. However, clinical studies are inconsistent. We therefore built a cohort of 1,943,682 male US veterans and used survival models to examine the association between HDL-C and risks of incident CKD or CKD progression (doubling of serum creatinine, eGFR decline of 30% or more), or a composite outcome of ESRD, dialysis, or renal transplantation. Models were adjusted for demographics, comorbid conditions, eGFR, body mass index, lipid parameters, and statin use over a median follow-up of 9 years. Compared to those with HDL-C of 40 mg/dl or more, low HDL-C (under 30 mg/dl) was associated with increased risk of incident eGFR under 60 ml/min/1.73 m(2) (hazard ratio: 1.18; confidence interval: 1.17-1.19) and risk of incident CKD (1.20; 1.18-1.22). Adjusted models demonstrate an association between low HDL-C and doubling of serum creatinine (1.14; 1.12-1.15), eGFR decline of 30% or more (1.13; 1.12-1.14), and the composite renal end point (1.08; 1.06-1.11). Cubic spline analyses of the relationship between HDL-C levels and renal outcomes showed a U-shaped relationship, where risk was increased in lowest and highest deciles of HDL-C. Thus, a significant association exists between low HDL-C levels and risks of incident CKD and CKD progression. Further studies are needed to explain the increased risk of adverse renal outcomes in patients with high HDL-C.

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.

A Cluster of Proteins Implicated in Kidney Disease Is Increased in High-Density Lipoprotein Isolated from Hemodialysis Subjects

Cardiovascular disease is the leading cause of death in end-stage renal disease (ESRD) patients treated with hemodialysis. An important contributor might be a decline in the cardioprotective effects of high-density lipoprotein (HDL). One important factor affecting HDL's cardioprotective properties may involve the alterations of protein composition in HDL. In the current study, we used complementary proteomics approaches to detect and quantify relative levels of proteins in HDL isolated from control and ESRD subjects. Shotgun proteomics analysis of HDL isolated from 20 control and 40 ESRD subjects identified 63 proteins in HDL. Targeted quantitative proteomics by isotope-dilution selective reaction monitoring revealed that 22 proteins were significantly enriched and 6 proteins were significantly decreased in ESRD patients. Strikingly, six proteins implicated in renal disease, including B2M, CST3, and PTGDS, were markedly increased in HDL of uremic subjects. Moreover, several of these proteins (SAA1, apoC-III, PON1, etc.) have been associated with atherosclerosis. Our observations indicate that the HDL proteome is extensively remodeled in uremic subjects. Alterations of the protein cargo of HDL might impact HDL's proposed cardioprotective properties. Quantifying proteins in HDL may be useful in the assessment of cardiovascular risk in patients with ESRD and in assessing response to therapeutic interventions.

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.

Association between high-density lipoprotein cholesterol and renal function in elderly hypertension: a cross-sectional study in Chinese population

Few studies have yet investigated the possible association between high-density lipoprotein cholesterol (HDL-C) and kidney function in elderly patients with primary hypertension. Accordingly, the aim of the present study was to evaluate the relationship between HDL-C and kidney function in elderly hypertension. A total of 14,644 elderly hypertensive subjects were enrolled in our cross-sectional study. The patients were categorized based on serum HDL-C level and glomerular filtration rate (GFR) value, respectively. One-way analysis of variance was used to compare the parameters among different groups. Bonferroni correction was performed for multiple comparisons. Analysis of covariance was used to control for confounding factors. The significance of difference between 3 groups and more was determined by chi-square test for categorical variables. Serum creatinine and uric acid were negatively related to HDL-C level, whereas GFR was positively related to HDL-C level in elderly hypertensive patients according to tertiles of HDL-C and tertiles of HDL-C/total cholesterol ratio (all P for trends <0.05). The male elderly hypertensive patients showed stronger relationship between HDL-C and renal function than the female elderly hypertensive subjects. Low HDL-C was associated with renal insufficiency and proteinuria in the hypertensive elderly (P < 0.05). The elderly "renal-hyperfiltrator" appeared to have lower HDL-C level, compared with the "normal renal-filtrator" (P < 0.05). There was an inverse "V" shape between HDL-C and GFR by GFR strata. Our results point out that there is an association of low HDL-C level with impaired kidney function in elderly hypertensive patients. Glomerular hyperfiltration may also affect HDL-C level and sex might be an influential factor for the association of HDL-C with kidney function in elderly hypertension.

Dialysis Modalities and HDL Composition and Function

Lipid abnormalities may have an effect on clinical outcomes of patients on dialysis. Recent studies have indicated that HDL dysfunction is a hallmark of ESRD. In this study, we compared HDL composition and metrics of HDL functionality in patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) with those in healthy controls. We detected a marked suppression of several metrics of HDL functionality in patients on HD or PD. Compositional analysis revealed that HDL from both dialysis groups shifted toward a more proinflammatory phenotype with profound alterations in the lipid moiety and protein composition. With regard to function, cholesterol efflux and anti-inflammatory and antiapoptotic functions seemed to be more severely suppressed in patients on HD, whereas HDL-associated paraoxonase activity was lowest in patients on PD. Quantification of enzyme activities involved in HDL metabolism suggested that HDL particle maturation and remodeling are altered in patients on HD or PD. In summary, our study provides mechanistic insights into the formation of dysfunctional HDL in patients with ESRD who are on HD or PD.

Dysfunctional high-density lipoproteins in children with chronic kidney disease

OBJECTIVES

Our aim was to determine if chronic kidney disease (CKD) occurring in childhood impairs the normally vasoprotective functions of high-density lipoproteins (HDLs).

MATERIALS AND METHODS

HDLs were isolated from children with end-stage renal disease on dialysis (ESRD), children with moderate CKD and controls with normal kidney function. Macrophage response to HDLs was studied as expression of inflammatory markers (MCP-1, TNF-α, IL-1β) and chemotaxis. Human umbilical vein endothelial cells were used for expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin) and adhesion. Cellular proliferation, apoptosis, and necrosis of endothelial cells were measured by MTS/PMS reagent-based assay, flow cytometry, and ELISA. Cholesterol efflux was assessed by gas chromatographic measurements of cholesterol in macrophages exposed to HDLs.

RESULTS

Compared with HDL(Control), HDL(CKD) and HDL(ESRD) heightened the cytokine response and disrupted macrophage chemotaxis. HDL(Control) reduced endothelial expression of ICAM-1, VCAM-1, E-selectin, whereas HDL(CKD) and HDL(ESRD) were less effective and showed reduced capacity to protect endothelial cells against monocyte adhesion. Compared with a dramatically enhanced endothelial proliferation following injurious stimulus by HDL(Control), neither HDL(CKD) nor HDL(ESRD) caused proliferative effects. HDLs of all three groups were equally protective against apoptosis assessed by flow cytometry and cleaved caspase-3 activity. Compared to HDL(Control), HDL(CKD) and HDL(ESRD) trended toward reduced capacity as cholesterol acceptors.

CONCLUSION

CKD in children impairs HDL function. Even in the absence of long-standing and concomitant risk factors, CKD alters specific HDL functions linked to control of inflammation and endothelial responses.

Quantification of HDL proteins, cardiac events, and mortality in patients with type 2 diabetes on hemodialysis

BACKGROUND AND OBJECTIVES

Impairment of HDL function has been associated with cardiovascular events in patients with kidney failure. The protein composition of HDLs is altered in these patients, presumably compromising the cardioprotective effects of HDLs. This post hoc study assessed the relation of distinct HDL-bound proteins with cardiovascular outcomes in a dialysis population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The concentrations of HDL-associated serum amyloid A (SAA) and surfactant protein B (SP-B) were measured in 1152 patients with type 2 diabetes mellitus on hemodialysis participating in The German Diabetes Dialysis Study who were randomly assigned to double-blind treatment of 20 mg atorvastatin daily or matching placebo. The association of SAA(HDL) and SP-B(HDL) with cardiovascular outcomes was assessed in multivariate regression models adjusted for known clinical risk factors.

RESULTS

High concentrations of SAA(HDL) were significantly and positively associated with the risk of cardiac events (hazard ratio per 1 SD higher, 1.09; 95% confidence interval, 1.01 to 1.19). High concentrations of SP-B(HDL) were significantly associated with all-cause mortality (hazard ratio per 1 SD higher, 1.10; 95% confidence interval, 1.02 to 1.19). Adjustment for HDL cholesterol did not affect these associations.

CONCLUSIONS

In patients with diabetes on hemodialysis, SAA(HDL) and SP-B(HDL) were related to cardiac events and all-cause mortality, respectively, and they were independent of HDL cholesterol. These findings indicate that a remodeling of the HDL proteome was associated with a higher risk for cardiovascular events and mortality in patients with ESRD.

An in-silico model of lipoprotein metabolism and kinetics for the evaluation of targets and biomarkers in the reverse cholesterol transport pathway

High-density lipoprotein (HDL) is believed to play an important role in lowering cardiovascular disease (CVD) risk by mediating the process of reverse cholesterol transport (RCT). Via RCT, excess cholesterol from peripheral tissues is carried back to the liver and hence should lead to the reduction of atherosclerotic plaques. The recent failures of HDL-cholesterol (HDL-C) raising therapies have initiated a re-examination of the link between CVD risk and the rate of RCT, and have brought into question whether all target modulations that raise HDL-C would be atheroprotective. To help address these issues, a novel in-silico model has been built to incorporate modern concepts of HDL biology, including: the geometric structure of HDL linking the core radius with the number of ApoA-I molecules on it, and the regeneration of lipid-poor ApoA-I from spherical HDL due to remodeling processes. The ODE model has been calibrated using data from the literature and validated by simulating additional experiments not used in the calibration. Using a virtual population, we show that the model provides possible explanations for a number of well-known relationships in cholesterol metabolism, including the epidemiological relationship between HDL-C and CVD risk and the correlations between some HDL-related lipoprotein markers. In particular, the model has been used to explore two HDL-C raising target modulations, Cholesteryl Ester Transfer Protein (CETP) inhibition and ATP-binding cassette transporter member 1 (ABCA1) up-regulation. It predicts that while CETP inhibition would not result in an increased RCT rate, ABCA1 up-regulation should increase both HDL-C and RCT rate. Furthermore, the model predicts the two target modulations result in distinct changes in the lipoprotein measures. Finally, the model also allows for an evaluation of two candidate biomarkers for in-vivo whole-body ABCA1 activity: the absolute concentration and the % lipid-poor ApoA-I. These findings illustrate the potential utility of the model in drug development.

Association of the triglycerides to high-density lipoprotein cholesterol ratio with the risk of chronic kidney disease: analysis in a large Japanese population

OBJECTIVES

To investigate the relationship between triglycerides to high-density lipoprotein cholesterol ratio (TG/HDL-C) and chronic kidney disease (CKD).

METHODS

We used data from 216,007 Japanese adults who participated in a nationwide health checkup program. Men (n = 88,516) and women (n = 127,491) were grouped into quartiles based on their TG/HDL-C levels (<1.26, 1.26-1.98, 1.99-3.18, and >3.18 in men; <0.96, 0.96-1.44, 1.45-2.22, and >2.22 in women). We cross-sectionally assessed the association of TG/HDL-C levels with CKD [defined as an estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m(2) (low eGFR) and/or proteinuria (defined as urinary protein ≥ 1+ on dipstick testing)], low eGFR, and proteinuria.

RESULTS

The prevalence of CKD, low eGFR, and proteinuria increased significantly with elevating quartiles of TG/HDL-C in both genders (all P for trend <0.001). Participants in the highest quartile of TG/HDL-C had a significantly greater risk of CKD than those in the lowest quartile after adjustment for the relevant confounding factors (odds ratio: 1.57, 95% confidence interval: 1.49-1.65 in men; 1.41, 1.34-1.48 in women, respectively). Furthermore, there were significant associations with low eGFR and proteinuria. In stratified analysis, the risk of CKD increased linearly with greater TG/HDL-C levels in participants with and without hypertension, diabetes, and obesity. Moreover, higher TG/HDL-C levels were relevant for CKD, especially in participants with hypertension and diabetes (P for interaction <0.001, respectively).

CONCLUSIONS

An elevated TG/HDL-C is associated with the risk of CKD in the Japanese population.

Vitamin E tocotrienol supplementation improves lipid profiles in chronic hemodialysis patients

PURPOSE

Chronic hemodialysis patients experience accelerated atherosclerosis contributed to by dyslipidemia, inflammation, and an impaired antioxidant system. Vitamin E tocotrienols possess anti-inflammatory and antioxidant properties. However, the impact of dietary intervention with Vitamin E tocotrienols is unknown in this population.

PATIENTS AND METHODS

A randomized, double-blind, placebo-controlled, parallel trial was conducted in 81 patients undergoing chronic hemodialysis. Subjects were provided daily with capsules containing either vitamin E tocotrienol-rich fraction (TRF) (180 mg tocotrienols, 40 mg tocopherols) or placebo (0.48 mg tocotrienols, 0.88 mg tocopherols). Endpoints included measurements of inflammatory markers (C-reactive protein and interleukin 6), oxidative status (total antioxidant power and malondialdehyde), lipid profiles (plasma total cholesterol, triacylglycerols, and high-density lipoprotein cholesterol), as well as cholesteryl-ester transfer protein activity and apolipoprotein A1.

RESULTS

TRF supplementation did not impact any nutritional, inflammatory, or oxidative status biomarkers over time when compared with the baseline within the group (one-way repeated measures analysis of variance) or when compared with the placebo group at a particular time point (independent t-test). However, the TRF supplemented group showed improvement in lipid profiles after 12 and 16 weeks of intervention when compared with placebo at the respective time points. Normalized plasma triacylglycerols (cf baseline) in the TRF group were reduced by 33 mg/dL (P=0.032) and 36 mg/dL (P=0.072) after 12 and 16 weeks of intervention but no significant improvement was seen in the placebo group. Similarly, normalized plasma high-density lipoprotein cholesterol was higher (P<0.05) in the TRF group as compared with placebo at both week 12 and week 16. The changes in the TRF group at week 12 and week 16 were associated with higher plasma apolipoprotein A1 concentration (P<0.02) and lower cholesteryl-ester transfer protein activity (P<0.001).

CONCLUSION

TRF supplementation improved lipid profiles in this study of maintenance hemodialysis patients. A multi-centered trial is warranted to confirm these observations.

Role of dyslipidemia in impairment of energy metabolism, oxidative stress, inflammation and cardiovascular disease in chronic kidney disease

Advanced chronic kidney disease (CKD) results in a constellation of dysregulation of lipid metabolism, oxidative stress, and inflammation which are causally interconnected and participate in a vicious cycle. The CKD-associated lipid disorders are marked by impaired clearance of very low density lipoprotein and chylomicrons, hypertriglyceridemia, formation of small dense low-density lipoprotein (LDL), oxidative modification of LDL, intermediate density lipoprotein and chylomicron remnants, and high-density lipoprotein deficiency and dysfunction. This review provides a brief overview of the role of CKD-induced lipid disorders in the pathogenesis of oxidative stress, inflammation, cardiovascular disease, impaired exercise capacity, cachexia and wasting syndrome.

Epidemiology and risk factors for chronic kidney disease in patients with ischaemic stroke

BACKGROUND

There is growing evidence for an association between chronic renal disease (CKD) and adverse cerebrovascular events because of the overlap of several risk factors. The purpose of this study is to examine the epidemiology of CKD and the characteristics of risk factors for CKD in the population with ischaemic stroke.

METHODS

This retrospective study included 571 patients with ischaemic stroke. Estimated glomerular filtration rate (eGFR) was calculated by the Modification of Diet in Renal Disease (MDRD) study equation. Renal function was assessed according to the Kidney Disease Outcomes Quality Initiative (K/DOQI)-CKD classification.

RESULTS

Study demonstrated that the major factors associated with CKD in the ischaemic stroke patients were age, diabetes mellitus, hypertension, systolic blood pressure, LDL cholesterol and serum uric acid. Diabetes mellitus (OR 4·146, 95% CI 1·047-16·418, P = 0·043), hypertension and diabetes mellitus (OR 3·574, 95% CI 1·248-10·234, P = 0·018), serum uric acid (OR 1·010, 95% CI 1·006-1·013, P < 0·001) and LDL cholesterol (OR 1·431, 95% CI 1·063-1·928, P = 0·018) were independent risk factors associated with CKD in the patients with ischaemic stroke.

CONCLUSIONS

The patients with ischaemic stroke may be considered as a high-risk population for CKD and be aggressively managed for CKD prevention. The high prevalence of CKD in population with ischaemic stroke prompts the need for greater public awareness about risks of CKD.

Targeting the transcription factor Nrf2 to ameliorate oxidative stress and inflammation in chronic kidney disease

Oxidative stress and inflammation are mediators in the development and progression of chronic kidney disease (CKD) and its complications, and they are inseparably linked as each begets and amplifies the other. CKD-associated oxidative stress is due to increased production of reactive oxygen species (ROS) and diminished antioxidant capacity. The latter is largely caused by impaired activation of Nrf2, the transcription factor that regulates genes encoding antioxidant and detoxifying molecules. Protective effects of Nrf2 are evidenced by amelioration of oxidative stress, inflammation, and kidney disease in response to natural Nrf2 activators in animal models, while Nrf2 deletion amplifies these pathogenic pathways and leads to autoimmune nephritis. Given the role of impaired Nrf2 activity in CKD-induced oxidative stress and inflammation, interventions aimed at restoring Nrf2 may be effective in retarding CKD progression. Clinical trials of the potent Nrf2 activator bardoxolone methyl showed significant improvement in renal function in CKD patients with type 2 diabetes. However, due to unforeseen complications the BEACON trial, which was designed to investigate the effect of this drug on time to end-stage renal disease or cardiovascular death in patients with advanced CKD, was prematurely terminated. This article provides an overview of the role of impaired Nrf2 activity in the pathogenesis of CKD-associated oxidative stress and inflammation and the potential utility of targeting Nrf2 in the treatment of CKD.

Post-transcriptional nature of uremia-induced downregulation of hepatic apolipoprotein A-I production

Chronic kidney disease is associated with premature death from cardiovascular disease, which is, in part, driven by high density lipoprotein deficiency and dysfunction. One of the main causes of high density lipoprotein deficiency in chronic kidney disease is diminished plasma apolipoprotein (Apo)A-I level. Plasma ApoA-I is reduced in dialysis patients and hepatic ApoA-I messenger RNA (mRNA) is decreased in the uremic rats. This study explored the mechanism of uremia-induced downregulation of ApoA-I. Human hepatoma derived cells were incubated in media containing whole plasma or plasma subfractionation from normal subjects and patients with end stage renal disease pre- and posthemodialysis. Cells and culture media were isolated to measure ApoA-I protein and mRNA. ApoA-I promoter activity was measured using transfection with a luciferase promoter construct containing the -2096 to +293 segment of ApoA-I gene. Finally, effect of uremic and control plasma was assessed on ApoA-I RNA stability. Exposure to uremic plasma significantly reduced ApoA-I mRNA expression and ApoA-I protein production. These effects were reversed by replacing uremic plasma with normal plasma. Although no difference in ApoA-I promoter activity was found between cells exposed to uremic and normal plasma, uremic plasma significantly reduced ApoA-I RNA stability. Experiments using plasma subfractions revealed that the inhibitory effect of uremic plasma on ApoA-I mRNA expression resides in fractions containing molecules larger but not smaller than 30 kd. The pre- and postdialysis plasma exerted an equally potent inhibitory effect on ApoA-I mRNA abundance. Uremia lowers ApoA-I production by reducing its RNA stability. The inhibitory effect of uremic milieu on ApoA-I mRNA expression is mediated by non-dialyzable molecule(s) larger than 30 kd.

Diminished antioxidant activity of high-density lipoprotein-associated proteins in chronic kidney disease

Background

Decreased serum arylesterase activity, catalyzed by the high‐density lipoprotein–associated paraoxonase (PON)‐1, is associated with increased oxidant stress and atherosclerosis risk. We sought to determine the prognostic value of serum PON‐1 activity, as monitored by PON or arylesterase activities, in subjects with chronic kidney disease (CKD), particularly in relation to established cardiac biomarkers.

Methods and Results

Serum arylesterase and PON activities were measured in sequential subjects with CKD (n=630; estimated glomerular filtration rate [eGFR] <60 mL/min per 1.73 m²) and an age‐ and sex‐matched control group of non‐CKD subjects (n=315) presenting for cardiac evaluations and prospectively followed for incident (3‐year) major adverse cardiac events (composite of death, nonfatal myocardial infarction, and stroke). Serum arylesterase activity in CKD subjects was lower compared with that in non‐CKD control subjects [median (interquartile range) 94 (77 to 112) versus 103 (85 to 121) μmol(L·min) per mL, P<0.001]; similarly, PON activity in CKD subjects was lower compared with that in non‐CKD control subjects [median (interquartile range) 474 (275 to 936) versus 586 (301 to 1118) nmol(L·min) per mL, P<0.001]. Lower serum arylesterase (hazard ratio 1.8, 95% CI 1.26 to 2.57, P<0.01) was a predictor of poorer outcomes. After adjusting for traditional risk factors and medication use, lower serum arylesterase (hazard ratio 1.55, 95% CI 1.08 to 2.23, P<0.05) still conferred an increased risk of major adverse cardiac events at 3 years.

Conclusions

In patients with CKD, decreased serum arylesterase activity, a measure of diminished antioxidant properties of PON‐1, predicts higher risk of incident long‐term adverse cardiovascular events (heart attack, stroke, or death) in multivariable models adjusting for established clinical and biochemical risk factors.

A prospective controlled study of kidney donors: baseline and 6-month follow-up

BACKGROUND

Most previous studies of living kidney donors have been retrospective and have lacked suitable healthy controls. Needed are prospective controlled studies to better understand the effects of a mild reduction in kidney function from kidney donation in otherwise healthy individuals.

STUDY DESIGN

Prospective, controlled, observational cohort study.

SETTING & PARTICIPANTS

Consecutive patients approved for donation at 8 transplant centers in the United States were asked to participate. For every donor enrolled, an equally healthy control with 2 kidneys who theoretically would have been suitable to donate a kidney also was enrolled.

PREDICTOR

Kidney donation.

MEASUREMENTS

At baseline predonation and at 6 months after donation, medical history, vital signs, measured (iohexol) glomerular filtration rate, and other measurements were collected. There were 201 donors and 198 controls who completed both baseline and 6-month visits and form the basis of this report.

RESULTS

Compared with controls, donors had 28% lower glomerular filtration rates at 6 months (94.6 ± 15.1 [SD] vs 67.6 ± 10.1 mL/min/1.73 m(2); P < 0.001), associated with 23% greater parathyroid hormone (42.8 ± 15.6 vs 52.7 ± 20.9 pg/mL; P < 0.001), 5.4% lower serum phosphate (3.5 ± 0.5 vs 3.3 ± 0.5 mg/dL; P < 0.001), 3.7% lower hemoglobin (13.6 ± 1.4 vs 13.1 ± 1.2 g/dL; P < 0.001), 8.2% greater uric acid (4.9 ± 1.2 vs 5.3 ± 1.1 mg/dL; P < 0.001), 24% greater homocysteine (1.2 ± 0.3 vs 1.5 ± 0.4 mg/L; P < 0.001), and 1.5% lower high-density lipoprotein cholesterol (54.9 ± 16.4 vs 54.1 ± 13.9 mg/dL; P = 0.03) levels. There were no differences in albumin-creatinine ratios (5.0 [IQR, 4.0-6.6] vs 5.0 [IQR, 3.3-5.4] mg/g; P = 0.5), office blood pressures, or glucose homeostasis.

LIMITATIONS

Short duration of follow-up and possible bias resulting from an inability to screen controls with kidney and vascular imaging performed in donors.

CONCLUSIONS

Kidney donors have some, but not all, abnormalities typically associated with mild chronic kidney disease 6 months after donation. Additional follow-up is warranted.

Comparative Analysis of Serum (Anti)oxidative Status Parаmeters in Healthy Persons

Five antioxidant and two oxidative stress assays were applied to serum samples of 43 healthy males. The antioxidant tests showed different inter-assay correlations. A very good correlation of 0.807 was observed between the ferric reducing ability of plasma (FRAP) and total antioxidant status (TAS) assay and also a fair correlation of 0.501 between the biological antioxidant potential (BAP) and TAS assay. There was no statistically significant correlation between the BAP and FRAP assay. The anti-oxidant assays have a high correlation with uric acid, especially the TAS (0.922) and FRAP assay (0.869). The BAP assay has a much lower and no statistically significant correlation with uric acid (0.302), which makes BAP more suitable for the antioxidant status. The total thiol assay showed no statistically significant correlation with uric acid (0.114). The total thiol assay, which is based on a completely different principle, showed a good and statistically significant correlation with the BAP assay (0.510) and also to the TAS assay, but to a lower and not significant extent (0.279) and not with the FRAP assay (-0.008). The oxy-adsorbent test (OXY) assay has no correlation with any of the other assays tested. The oxidative stress assays, reactive oxygen metabolites (ROM) and total oxidant status (TOS), based on a different principle, do not show a statistically significant correlation with the serum samples in this study. Both assays showed a negative, but not significant, correlation with the antioxidant assays. In conclusion, the ROM, TOS, BAP and TTP assays are based on different principles and will have an additional value when a combination of these assays will be applied in large-scale population studies.

Homocysteine-mediated cholesterol efflux via ABCA1 and ACAT1 DNA methylation in THP-1 monocyte-derived foam cells

Homocysteine (Hcy) has been recognized as a prevalent risk factor for cardiovascular events. Cholesterol-loaded foam cells are a central component of atherosclerotic lesions. ATP-binding cassette transporter A1 (ABCA1), which mediates the efflux of cellular cholesterol and phospholipids, is the rate-limiting step in lipid metabolism. Acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) promotes accumulation of cholesterol ester in macrophages, thereby resulting in the foam cell formation, a hallmark of early stage in atherosclerosis. In this study, cultured monocyte-derived foam cells were incubated with clinical relevant concentrations of Hcy for 24 h. Both increased number of foam cells and accumulation of cholesterol were found, and the mRNA and protein expression levels of ABCA1 were decreased, while ACAT1 expression was increased in the presence of Hcy. Furthermore, the DNA methylation level of ABCA1 gene was increased whereas ACAT1 DNA methylation was decreased by using different concentrations of Hcy. Moreover, our results showed that DNA methyltransferase (DNMT) activity and DNA methyltransferase 1 (DNMT1) mRNA expression were increased by Hcy. It is indicated that DNA methylation has the function to regulate the expression of ABCA1 and ACAT1 via DNMT. In conclusion, these results suggest that ABCA1 and ACAT1 DNA methylation induced by Hcy may play a potential role in ABCA1 and ACAT1 expression and the accumulation of cholesterol in monocyte-derived foam cells.

High-density lipoprotein in uremic patients: metabolism, impairment, and therapy

Several studies have shown that HDL has altered antioxidant and anti-inflammatory effects in chronic uremia, either by the reduction in its antioxidant enzymes or by the impairment of their activity. Systemic oxidative stress, which is highly prevalent in chronic kidney disease (CKD) patients, has been shown to decrease antioxidant and anti-inflammatory effects of HDL and even transform it into a pro-oxidant and pro-inflammatory agent. For this reason, we believe that the propensity for accelerated cardiovascular disease in CKD is facilitated by a few key features of this disease, namely, oxidative stress, inflammation, hypertension, and disorders of lipid metabolism. In a nutshell, oxidative stress and inflammation enhance atherosclerosis leading to increased cardiovascular mortality and morbidity in this population. In this detailed review, we highlight the current knowledge on HDL dysfunction and impairment in chronic kidney disease as well as the available therapy.

Lysophosphatidylcholine, oxidized low-density lipoprotein and cardiovascular disease in Korean hemodialysis patients: analysis at 5 years of follow-up

Although oxidized low-density lipoprotein (LDL) and lysophosphatidylcholine (LPC) have been proposed as important mediators of the atherosclerosis, the long-term contribution to the risk of cardiovascular disease (CVD) in hemodialysis patients has not been evaluated. This study investigated the relation between oxidized LDL and LPC levels with long term risk of CVD. Plasma oxidized LDL and LPC levels were determined in 69 Korean hemodialysis patients as a prospective observational study for 5 yr. During the observation period, 18 cardiovascular events (26.1%) occurred including 6 deaths among the hemodialysis patients. The low LPC level group (≤ 254 µM/L, median value) had much more increased risk of CVD compared to the high LPC level group (> 254 µM/L) (P = 0.01). However, serum levels of oxidized LDL were not significantly different between groups with and without CVD. In adjusted Cox analysis, previous CVD, (hazard ratio [HR], 5.68; 95% confidence interval [CI], 1.94-16.63, P = 0.002) and low LPC level (HR, 3.45; 95% CI, 1.04-11.42, P = 0.04) were significant independent risk factors for development of CVD. It is suggested that low LPC, but not oxidized LDL, is associated with increased risk of CVD among a group of Korean hemodialysis patients.

Reasons for the lack of salutary effects of cholesterol-lowering interventions in end-stage renal disease populations

Cardiovascular disease (CVD) is the main cause of premature death in patients with chronic kidney disease (CKD). The underlying mechanisms of CVD in patients with mild to moderate CKD are different from those with end-stage renal disease (ESRD). While serum cholesterol is frequently elevated and contributes to atherosclerosis in many CKD patients, particularly those with nephrotic proteinuria, it is usually normal, even subnormal, in most ESRD patients receiving hemodialysis. CVD in the ESRD population is primarily driven by oxidative stress, inflammation, accumulation of the oxidation-prone intermediate-density lipoproteins, chylomicron remnants and small dense low-density lipoprotein particles as well as high-density lipoprotein deficiency and dysfunction, hypertension, vascular calcification, and arrhythmias. Only a minority of hemodialysis patients have hypercholesterolemia which is most likely due to genetic or unrelated factors. In addition, due to peritoneal losses of proteins which simulate nephrotic syndrome, peritoneal dialysis patients often exhibit hypercholesterolemia. Clearly when present, hypercholesterolemia contributes to CVD in the CKD and ESRD population and justifies cholesterol-lowering therapy. However, the majority of ESRD patients and a subpopulation of CKD patients with minimal proteinuria have normal or subnormal serum cholesterol levels and do not benefit from and can be potentially harmed by statin therapy. In fact the lack of efficacy of statins in hemodialysis patients has been demonstrated in several randomized clinical trials. This review is intended to provide an overview of the mechanisms responsible for the failure of statins to reduce cardiovascular morbidity and mortality in most ESRD patients and to advocate the adoption of individualized care principles in the management of dyslipidemia in this population.

Autoantibodies to apolipoprotein A-1 in cardiovascular diseases: current perspectives

Immune-mediated inflammation plays a major role in atherosclerosis and atherothrombosis, two essential features for cardiovascular disease (CVD) development, currently considered as the leading cause of death in the western world. There is accumulating evidence showing that humoral autoimmunity might play an important role in CVD and that some autoantibodies could represent emerging cardiovascular risk factors. Recent studies demonstrate that IgG autoantibodies against apolipoprotein A-1 (apoA-1) are raised in many diseases associated with a high cardiovascular risk, such as systemic lupus erythematosus, acute coronary syndrome, rheumatoid arthritis, severe carotid stenosis, and end-stage renal disease. In this work, we aimed at reviewing current data in the literature pointing to anti-apolipoprotein A-1 antibodies (anti-apoA-1 IgG) as a possible prognostic and diagnostic biomarker of cardiovascular risk and appraising their potential role as active mediators of atherogenesis.

Dysregulation of hepatic fatty acid metabolism in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) results in hypertriglyceridemia which is largely due to impaired clearance of triglyceride-rich lipoproteins occasioned by downregulation of lipoprotein lipase and very low-density lipoprotein (LDL) receptor in the skeletal muscle and adipose tissue and of hepatic lipase and LDL receptor-related protein in the liver. However, data on the effect of CKD on fatty acid metabolism in the liver is limited and was investigated here.

METHODS

Male Sprague-Dawley rats were randomized to undergo 5/6 nephrectomy (CRF) or sham operation (control) and observed for 12 weeks. The animals were then euthanized and their liver tissue tested for nuclear translocation (activation) of carbohydrate-responsive element binding protein (ChREBP) and sterol-responsive element binding protein-1 (SREBP-1) which independently regulate the expression of key enzyme in fatty acid synthesis, i.e. fatty acid synthase (FAS) and acyl-CoA carboxylase (ACC) as well as nuclear Peroxisome proliferator-activated receptor alpha (PPARα) which regulates the expression of enzymes involved in fatty acid oxidation and transport, i.e. L-FABP and CPT1A. In addition, the expression of ATP synthase α, ATP synthase β, glycogen synthase and diglyceride acyltransferase 1 (DGAT1) and DGAT2 were determined.

RESULTS

Compared with controls, the CKD rats exhibited hypertriglyceridemia, elevated plasma and liver tissue free fatty acids, increased nuclear ChREBP and reduced nuclear SREBP-1 and PPARα, upregulation of ACC and FAS and downregulation of L-FABP, CPT1A, ATP synthase α, glycogen synthase and DGAT in the liver tissue.

CONCLUSION

Liver in animals with advanced CKD exhibits ChREBP-mediated upregulation of enzymes involved in fatty acid synthesis, downregulation of PPARα-regulated fatty acid oxidation system and reduction of DGAT resulting in reduced fatty acid incorporation in triglyceride.

Current smoking status may be associated with overt albuminuria in female patients with type 1 diabetes mellitus: a cross-sectional study

BACKGROUND

There are very few clinical reports that have compared the association between cigarette smoking and microangiopathy in Asian patients with type 1 diabetes mellitus (T1DM). The objective of this study was to assess the relationships between urinary protein concentrations and smoking and gender-based risk factors among patients with T1DM.

METHODS

A cross-sectional study of 259 patients with T1DM (men/women = 90/169; mean age, 50.7 years) who visited our hospital for more than 1 year between October 2010 and April 2011 was conducted. Participants completed a questionnaire about their smoking habits. Patient characteristics included gender, age, body mass index, blood pressure, hemoglobin A1c, lipid parameters, and microangiopathy. Diabetic nephropathy (DN) was categorized as normoalbuminuria (NA), microalbuminuria (MA), or overt albuminuria (OA) on the basis of the following urinary albumin/creatinine ratio (ACR) levels: NA, ACR levels less than 30 mg/g creatinine (Cr); MA, ACR levels between 30 and 299 mg/g Cr; and OA, ACR levels over 300 mg/g Cr.

RESULTS

The percentages of current nonsmokers and current smokers with T1DM were 73.0% (n = 189) and 27.0% (n = 70), respectively. In addition, the percentage of males was higher than that of females (52.2% versus 13.6%) in the current smoking population. The percentage of DN was 61.8% (n = 160) in patients with NA, 21.6% (n = 56) in patients with MA, and 16.6% (n = 43) in patients with OA. The percentage of males among OA patients was also higher than that of females (24.4% versus 12.4%). However, current smoking status was associated with OA in females with T1DM only [unadjusted odds ratio (OR), 4.13; 95% confidence interval (CI), 1.45-11.73, P < 0.01; multivariate-adjusted OR, 5.41; 95% CI, 1.69-17.30, P < 0.01].

CONCLUSIONS

Based on our results in this cross-sectional study of Asian patients with T1DM, smoking might be a risk factor for OA among female patients. Further research is needed of these gender-specific results.

Reduced kidney lipoprotein lipase and renal tubule triglyceride accumulation in cisplatin-mediated acute kidney injury

Peroxisome proliferator-activated receptor-α (PPARα) activation attenuates cisplatin (CP)-mediated acute kidney injury by increasing fatty acid oxidation, but mechanisms leading to reduced renal triglyceride (TG) accumulation could also contribute. Here, we investigated the effects of PPARα and CP on expression and enzyme activity of kidney lipoprotein lipase (LPL) as well as on expression of angiopoietin protein-like 4 (Angptl4), glycosylphosphatidylinositol-anchored-HDL-binding protein (GPIHBP1), and lipase maturation factor 1 (Lmf1), which are recognized as important proteins that modulate LPL activity. CP caused a 40% reduction in epididymal white adipose tissue (WAT) mass, with a reduction of LPL expression and activity. CP also reduced kidney LPL expression and activity. Angptl4 mRNA levels were increased by ninefold in liver and kidney tissue and by twofold in adipose tissue of CP-treated mice. Western blots of two-dimensional gel electrophoresis identified increased expression of a neutral pI Angptl4 protein in kidney tissue of CP-treated mice. Immunolocalization studies showed reduced staining of LPL and increased staining of Angptl4 primarily in proximal tubules of CP-treated mice. CP also increased TG accumulation in kidney tissue, which was ameliorated by PPARα ligand. In summary, a PPARα ligand ameliorates CP-mediated nephrotoxicity by increasing LPL activity via increased expression of GPHBP1 and Lmf1 and by reducing expression of Angptl4 protein in the proximal tubule.

Effect of uremia on structure and function of immune system

End-stage renal disease (ESRD) is simultaneously associated with immune activation, marked by systemic inflammation, and immune deficiency. Systemic inflammation contributes to atherosclerosis, cardiovascular disease, cachexia, and anemia, whereas immune deficiency leads to impaired response to vaccination, and increased incidence and severity of microbial infections. ESRD-associated inflammation and immune deficiency are associated with the following: (a) general expansion of monocytes and elevations of their basal integrin, Toll-like receptor (TLR)-2, TLR-4 expression, cytokine production, and reactive oxygen species (ROS) generation and reduced phagocytic capacity, (b) depletion and impaired inhibitory activity of regulatory T cells, (c) spontaneous activation, degranulation, increased basal ROS production, decreased phagocytic capacity, and increased apoptosis of the circulating polymorphonuclear leukocytes, (d) upregulation of ROS production machinery and chemokine expression in the cellular constituents of various tissues, highlighting participation of nonimmune cells in the prevailing inflammatory state, (e) depletion of the antigen-presenting dendritic cells, (f) reduced CD4/CD8 T cell ratio and depletion of naïve and central memory T cells, (g) diffuse B cell lymphopenia leading to impaired humoral immunity, and (h) increased proinflammatory activity of low-density lipoprotein and reduced anti-inflammatory capacity of high-density lipoprotein. Thus, ESRD-associated inflammation is due to activation of innate immune system, orchestrated by monocytes, macrophages, granulocytes, and cellular constituents of other organs/tissues. This is coupled with immune deficiency that is caused by depletion of dendritic cells, naïve and central memory T cells and B cells, and impaired phagocytic function of polymorphonuclear leukocytes and monocytes.

Paraoxonase 1 in chronic kidney failure

In this review we summarize the findings from the literature and our own laboratory on the decreased PON1 activity in renal failure, the mechanisms proposed and the effect of interventions. In addition to profound alterations in lipoproteins, reduced serum PON1 activity has been clearly established in the past decade and could contribute to accelerated development of atherosclerosis in ESRD and in HD. PON1 lactonase activity is lower in ESRD patients. Hemodialysis partially restores PON1 lactonase and the other activities. PON1 activity recovery after dialysis suggests that uremic toxins may play a mechanistic role in PON1 inactivation. Lower PON1 activity in CRF patients is associated with low thiol concentration, high CRP, and is beneficially enhanced with vitamin C and flavonoids. Changes in HDL subclasses, namely lower HDL₃ in these patients may also play a role in PON1 lower activity. Future research should focus on: (1) mechanistic studies on causes for low PON1 activity and mass; (2) prospective studies focusing on whether there is an added predictive value in measuring PON1 activity (and PON1 activity in HDL₃) in this patient population; (3) intervention studies attempting to increase PON1 activity.

Prevalence and risk factors for chronic kidney disease in patients with coronary artery disease

OBJECTIVES

Chronic renal disease (CKD) is recognized as a worldwide public health problem. Traditional risk factors for CKD are also present in coronary artery disease (CAD). The purpose of this study is to examine the prevalence and characteristics of risk factors for CKD in the population with CAD.

METHODS

Renal function was evaluated in 527 patients with CAD in order to assess characteristics of the incidence, risk factors for CKD in the population with CAD. In the present study in order to concentrate on evaluation for eGFR of the patients with CAD proteinuria is not included in the definition of CKD.

RESULTS

Univariate analysis demonstrated that the major risk factors associated with CKD in the patients with CAD were age (P ≤ 0.001), smoking (P = 0.016), diabetes mellitus (P = 0.021), hypertension (P ≤ 0.001), and systolic blood pressure (P = 0.004). The percentages of patients with both hypertension and diabetes mellitus were significantly greater in the CKD3-4 group (P < 0.001). The results of multivariable analysis showed that hypertension (OR 1.925, 95% CI 1.196-3.098, P = 0.007), diabetes mellitus (OR 1.744, 95% CI 1.044-2.914, P = 0.034) and serum uric acid (OR 1.008, 95% CI 1.006-1.010, P ≤ 0.001) were independent risk factors for reduced eGFR.

CONCLUSIONS

CKD is common and has a high prevalence in the population with CAD. Several risk factors are known to simultaneously affect heart and kidney. The patients with CAD may be considered as a high-risk population for CKD.

Statins in the management of dyslipidemia associated with chronic kidney disease

The cause of death in the majority of patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) is accelerated cardiovascular disease and not renal failure per se, suggesting a role for statin therapy in this setting. During the past 6 years three large, randomized, placebo-controlled studies of three different statins have been conducted in the dialysis population-but two of these studies did not demonstrate any benefits of statin therapy, and the third study showed only marginally positive results. To understand why statins have failed to reduce cardiovascular events in patients with ESRD, the basic mechanisms underlying the pathogenesis of dyslipidemia in CKD must be critically examined. The observed negative results in the clinical trials of statin therapy might also reflect the biomarkers and targets that were chosen to be evaluated. The characteristics of dyslipidemia in patients with CKD not yet requiring dialysis treatment differ markedly from those of individuals with established ESRD and form the basis for therapeutic recommendations. The potential adverse effects associated with statin therapy are important to consider in the management of dyslipidemia in patients with CKD.

Serum amyloid A in uremic HDL promotes inflammation

Uremia impairs the atheroprotective properties of HDL, but the mechanisms underlying why this occurs are unknown. Here, we observed that HDL isolated from healthy individuals inhibited the production of inflammatory cytokines by peripheral monocytes stimulated with a Toll-like receptor 2 agonist. In contrast, HDL isolated from the majority of patients with ESRD did not show this anti-inflammatory property; many HDL samples even promoted the production of inflammatory cytokines. To investigate this difference, we used shotgun proteomics to identify 49 HDL-associated proteins in a uremia-specific pattern. Proteins enriched in HDL from patients with ESRD (ESRD-HDL) included surfactant protein B (SP-B), apolipoprotein C-II, serum amyloid A (SAA), and α-1-microglobulin/bikunin precursor. In addition, we detected some ESRD-enriched proteins in earlier stages of CKD. We did not detect a difference in oxidation status between HDL isolated from uremic and healthy patients. Regarding function of these uremia-specific proteins, only SAA mimicked ESRD-HDL by promoting inflammatory cytokine production. Furthermore, SAA levels in ESRD-HDL inversely correlated with its anti-inflammatory potency. In conclusion, HDL has anti-inflammatory activities that are defective in uremic patients as a result of specific changes in its molecular composition. These data suggest a potential link between the high levels of inflammation and cardiovascular mortality in uremia.

Oxidized high-density lipoprotein as a risk factor for cardiovascular events in prevalent hemodialysis patients

BACKGROUND AND OBJECTIVES

Here, we assessed the impact of oxidized high-density lipoprotein (oxHDL), dysfunctional HDL, on mortality and cardiovascular disease (CVD) events in prevalent HD patients and compared oxHDL to interleukin-6 (IL-6), a strong predictor of CVD events in HD patients.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This prospective study examined a cohort of prevalent HD patients (n=412). Blood samples were obtained at baseline to measure lipids, high-sensitive C-reactive protein (hsCRP), IL-6, oxidized low-density lipoprotein, N-terminal pro B-type natriuretic peptide, intercellular adhesion molecule 1 (ICAM-1), myeloperoxidase, adiponectin, and oxHDL. Carotid intima-media thickness (CIMT) was assessed at baseline and 3-year follow-up. Nutritional status was assessed by subjective global assessment (SGA), body mass index, and geriatric nutritional risk index (GNRI). After the baseline assessment, study patients were prospectively followed up (mean observational period, 40 months).

RESULTS

At baseline, patients with high oxHDL had a worse nutritional state and higher HDL-cholesterol (HDL-chol), ICAM-1, and adiponectin levels and a higher oxHDL/HDL-chol ratio than low oxHDL patients. A combination of high oxHDL and high IL-6 was significantly associated with increased CIMT at baseline and a larger increase in CIMT at 3-year follow-up. High oxHDL did not predict all-cause mortality; however, it was significantly associated with CVD-related mortality and composite CVD events, particularly with concomitant high IL-6. These associations were confirmed in multivariate Cox hazard models adjusted with confounding variables.

CONCLUSIONS

High oxHDL, particularly with concomitant high IL-6, may be associated with an increased risk of CVD events and CVD-related mortality in prevalent HD patients.

Lipoprotein lipase deficiency in chronic kidney disease is accompanied by down-regulation of endothelial GPIHBP1 expression

BACKGROUND

Chronic renal failure (CRF) is associated with hypertriglyceridemia and impaired clearance of very low density lipoprotein (VLDL) and chylomicrons which are largely due to lipoprotein lipase (LPL) deficiency/dysfunction. After its release from myocytes and adipocytes, LPL binds to the endothelium in the adjacent capillaries where it catalyzes hydrolysis of triglycerides in VLDL and chylomicrons. The novel endothelium-derived molecule, glycosylphosphatidylinositol-anchored binding protein 1 (GPIHBP1), plays a critical role in LPL metabolism and function by anchoring LPL to the endothelium and binding chylomicrons. GPIHBP1-deficient mice and humans exhibit severe hypertriglyceridemia and diminished heparin-releasable LPL, pointing to the critical role of GPIHBP1 in regulation of LPL activity. Given its central role in regulation of LPL activity and triglyceride metabolism, we explored the effect of chronic kidney disease (CKD) on GPIHBP1 expression.

METHODS

Expression of GPIHBP1 and LPL were determined by reverse transcriptase-polymerase chain reaction, Western blot and immunohistochemical analyses in the adipose tissue, skeletal muscle and myocardium of rats 12 weeks after 5/6 nephrectomy (CRF) or sham-operation (control).

RESULTS

Compared to the controls, the CRF group exhibited severe hypertriglyceridemia, significant reduction of the skeletal muscle, myocardium and adipose tissue LPL mRNA and protein abundance. This was accompanied by parallel reductions of GPIHBP1 mRNA abundance and immunostaining in the tested tissues.

CONCLUSIONS

LPL deficiency in CKD is associated with and compounded by GPIHBP1 deficiency. Together these abnormalities contribute to impaired clearance of triglyceride-rich lipoproteins, diminished availability of lipid fuel for energy storage in adipocytes and energy production in myocytes and consequent hypertriglyceridemia, cachexia, muscle weakness and atherosclerosis.

APOL1 localization in normal kidney and nondiabetic kidney disease

In patients of African ancestry, genetic variants in APOL1, which encodes apolipoprotein L1, associate with the nondiabetic kidney diseases, focal segmental glomerulosclerosis (FSGS), HIV-associated nephropathy (HIVAN), and hypertensive nephropathy. Understanding the renal localization of APOL1 may provide clues that will ultimately help elucidate the mechanisms by which APOL1 variants promote nephropathy. Here, we used immunohistology to examine APOL1 localization in normal human kidney sections and in biopsies demonstrating either FSGS (n = 8) or HIVAN (n = 2). Within normal glomeruli, APOL1 only localized to podocytes. Compared with normal glomeruli, fewer cells stained for APOL1 in FSGS and HIVAN glomeruli, even when expression of the podocyte markers GLEPP1 and synaptopodin appeared normal. APOL1 localized to proximal tubular epithelia in normal kidneys, FSGS, and HIVAN. We detected APOL1 in the arteriolar endothelium of normal and diseased kidney sections. Unexpectedly, in both FSGS and HIVAN but not normal kidneys, the media of medium artery and arterioles contained a subset of α-smooth muscle actin-positive cells that stained for APOL1. Comparing the renal distribution of APOL1 in nondiabetic kidney disease to normal kidney suggests that a previously unrecognized arteriopathy may contribute to disease pathogenesis in patients of African ancestry.