Plasma Concentrations of Trimethylamine-N-Oxide, Choline, and Betaine in Patients With Moderate to Advanced Chronic Kidney Disease and Their Relation to Cardiovascular and Renal Outcomes

OBJECTIVES

Trimethylamine N-oxide (TMAO) is a gut bacteria-mediated liver metabolite of dietary betaine, choline, and carnitine, which is excreted by glomerular filtration. We studied whether TMAO is excreted by cardiovascular disease (CVD) in patients with chronic kidney disease (CKD).

METHODS

Among 478 patients with CKD stage G2 (n = 104), G3a (n = 163), G3b (n = 123), and G4 (n = 88), we studied the association between fasting plasma concentrations of TMAO, choline, or betaine at baseline and kidney function, prevalent CVD, and future renal outcomes during a mean follow-up of 5.1 years.

RESULTS

Decreased glomerular filtration rate was associated with higher plasma concentrations of TMAO, choline, and betaine. Baseline concentrations of TMAO were higher in participants with preexisting CVD compared to those without CVD (8.4 [10.1] vs. 7.8 [8.0] μmol/L; P = .047), but the difference was not significant after adjusting for confounders. During the follow-up, 147 participants experienced CVD or died, and 144 reached the predefined renal endpoint. In the adjusted regression analyses, TMAO or choline concentrations in the upper three quartiles (vs. the lowest quartile) were not associated with any of the study's clinical endpoints. In contrast, the adjusted hazard ratio of plasma betaine in the highest quartile versus the lowest quartile was 2.14 (1.32, 3.47) for the CVD endpoint and 1.64 (1.00, 2.67) for the renal endpoint.

CONCLUSIONS

Elevated plasma TMAO concentrations were explained by impaired kidney function. Elevated plasma concentrations of betaine, but not those of TMAO or choline, constituted a risk factor for adverse outcomes. TMAO might not be an appropriate target to reduce CVD or renal outcomes in patients with preexisting CKD.

Hydrophilic Modification of Dialysis Membranes Sustains Middle Molecule Removal and Filtration Characteristics

While efficient removal of uremic toxins and accumulated water is pivotal for the well-being of dialysis patients, protein adsorption to the dialyzer membrane reduces the performance of a dialyzer. Hydrophilic membrane modification with polyvinylpyrrolidone (PVP) has been shown to reduce protein adsorption and to stabilize membrane permeability. In this study we compared middle molecule clearance and filtration performance of nine polysulfone-, polyethersulfone-, and cellulose-based dialyzers over time. Protein adsorption was simulated in recirculation experiments, while β2-microglobulin clearance as well as transmembrane pressure (TMP) and filtrate flow were determined over time. The results of this study showed that β2-microglobulin clearance (-7.2 mL/min/m2) and filtrate flow (-54.4 mL/min) decreased strongly during the first 30 min and slowly afterwards (-0.7 mL/min/m2 and -6.8 mL/min, respectively, for the next 30 min); the TMP increase (+37.2 mmHg and +8.6 mmHg, respectively) showed comparable kinetics. Across all tested dialyzers, the dialyzer with a hydrophilic modified membrane (FX CorAL) had the highest β2-microglobulin clearance after protein fouling and the most stable filtration characteristics. In conclusion, hydrophilic membrane modification with PVP stabilizes the removal capacity of middle molecules and filtration performance over time. Such dialyzers may have benefits during hemodiafiltration treatments which aim to achieve high exchange volumes.

ELOVL2-methylation and renal and cardiovascular event in patients with chronic kidney disease

BACKGROUND

Methylation of the Elongation Of Very Long Chain Fatty Acids-Like 2 (ELOVL2) gene promoter may predict premature ageing and cardiovascular risk.

METHODS

We studied the cross-sectional associations between blood ELOVL2-methylation and cardiovascular risk factors in 350 patients with chronic kidney disease (CKD) stage G2-G4 aged between 22 and 90 years. In a follow-up study for a mean of 3.9 years, we investigated the association between baseline ELOVL2-methylation and renal or cardiovascular events including death.

RESULTS

ELOVL2-methylation at seven CpG cites increased with age (the correlation coefficients between 0.67 and 0.87, p < 0.001). The ELOVL2-CpGs methylation was lower in patients with CKD stage G2 versus those in stage G3a, G3b and G4, but the differences were explained by age. ELOVL2-CpGs methylation showed no correlations with cardiovascular risk factors after adjusting for age. During the follow-up, 64 patients showed deterioration in renal function or died and 77 showed cardiovascular events or died. The hazard ratio and 95% confidence intervals for renal or cardiovascular events according to baseline ELOVL2-CpGs methylation were not significant after adjustment for covariates.

CONCLUSIONS

ELOVL2-hypermethylation showed a strong association with age, but was not independently associated with cardiovascular risk factors or with future renal or cardiovascular events in patients with CKD. ELOVL2 gene methylation is not likely to be itself a cause for ageing or illnesses, but it could be rather influenced by other upstream processes that deserve investigation.

Assessment of a serum calcification propensity test for the prediction of all-cause mortality among hemodialysis patients

BACKGROUND

Vascular calcification is a major contributor to the high cardiac burden among hemodialysis patients. A novel in vitro T50-test, which determines calcification propensity of human serum, may identify patients at high risk for cardiovascular (CV) disease and mortality. We evaluated whether T50 predicts mortality and hospitalizations among an unselected cohort of hemodialysis patients.

METHODS

This prospective clinical study included 776 incident and prevalent hemodialysis patients from 8 dialysis centers in Spain. T50 and fetuin-A were determined at Calciscon AG, all other clinical data were retrieved from the European Clinical Database. After their baseline T50 measurement, patients were followed for two years for the occurrence of all-cause mortality, CV-related mortality, all-cause and CV-related hospitalizations. Outcome assessment was performed with proportional subdistribution hazards regression modelling.

RESULTS

Patients who died during follow-up had a significantly lower T50 at baseline as compared to those who survived (269.6 vs. 287.7 min, p = 0.001). A cross-validated model (mean c statistic: 0.5767) identified T50 as a linear predictor of all-cause-mortality (subdistribution hazard ratio (per min): 0.9957, 95% CI [0.9933;0.9981]). T50 remained significant after inclusion of known predictors. There was no evidence for prediction of CV-related outcomes, but for all-cause hospitalizations (mean c statistic: 0.5284).

CONCLUSION

T50 was identified as an independent predictor of all-cause mortality among an unselected cohort of hemodialysis patients. However, the additional predictive value of T50 added to known mortality predictors was limited. Future studies are needed to assess the predictive value of T50 for CV-related events in unselected hemodialysis patients.

Impact of Hydrophilic Modification of Synthetic Dialysis Membranes on Hemocompatibility and Performance

The dialyzer is the core element in the hemodialysis treatment of patients with end-stage kidney disease (ESKD). During hemodialysis treatment, the dialyzer replaces the function of the kidney by removing small and middle-molecular weight uremic toxins, while retaining essential proteins. Meanwhile, a dialyzer should have the best possible hemocompatibility profile as the perpetuated contact of blood with artificial surfaces triggers complement activation, coagulation and immune cell activation, and even low-level activation repeated chronically over years may lead to undesired effects. During hemodialysis, the adsorption of plasma proteins to the dialyzer membrane leads to a formation of a secondary membrane, which can compromise both the uremic toxin removal and hemocompatibility of the dialyzer. Hydrophilic modifications of novel dialysis membranes have been shown to reduce protein adsorption, leading to better hemocompatibility profile and performance stability during dialysis treatments. This review article focuses on the importance of performance and hemocompatibility of dialysis membranes for the treatment of dialysis patients and summarizes recent studies on the impact of protein adsorption and hydrophilic modifications of membranes on these two core elements of a dialyzer.

Time-resolving characterization of molecular weight retention changes among three synthetic high-flux dialyzers

BACKGROUND

Toxin removal capacity (i.e. performance) of a dialyzer is not constant but diminishes during treatment, as the adsorption of proteins to the membrane provides an additional barrier to uremic solutes. We investigated time-resolving molecular weight retention changes among synthetic high-flux dialyzers and compare the results with recent data from a randomized controlled trial.

METHODS

In plasma recirculation experiments over 240min, sieving coefficients (SC) for β2-microglobulin, myoglobin and albumin were determined for the FX CorAL (Fresenius Medical Care), ELISIO (Nipro) and xevonta (B. Braun). Molecular weight retention (MWR) curves were generated and the shifts over 120min were characterized. Effective pore radius was determined, and the predicted albumin loss was compared with clinical data.

RESULTS

SC decreased over time for all dialyzers (mean relative decrease across all dialyzers: β2-microglobulin: 8.0% (120min); myoglobin: 56.6% (240min); albumin: 94.1% (240min)). FX CorAL (7.3%, 52.6% and 91.1%) and ELISIO (7.7%, 51.0% and 93.8%) showed a lower decrease than xevonta (9.0%, 66.2% and 97.4%). For all dialyzers, MWR curves shifted towards lower molecular weight, with the lowest shift for FX CorAL (by 0.23nm at SC50%, 120 min) and highest for xevonta (0.50nm). FX CorAL had the highest slope over time and the smallest decrease in the effective pore radius (2min: 2.31nm, 120min: 2.08nm). Predicted albumin loss over 4h was highest for xevonta (609.3mg) and comparable between ELISIO (283.6mg) and FX CorAL (313.3mg).

CONCLUSIONS

Substantial differences in the temporal performance profile of dialyzers exist. The present approach allows characterization of dialyzer permeability changes over time using standard, clinically relevant protein markers.

FGFR4 and Klotho Polymorphisms Are Not Associated with Cardiovascular Outcomes in Chronic Kidney Disease

INTRODUCTION

High plasma fibroblast growth factor 23 (FGF-23) predicts cardiovascular events in chronic kidney disease (CKD) patients. Experimental evidence suggests FGF receptor 4 (FGFR4) activation by FGF-23, and deficiency of the soluble form of its co-receptor Klotho promotes left-ventricular hypertrophy (LVH). To evaluate the clinical relevance of these findings, a Mendelian randomization study analyzed the association of genetic variants of FGFR4 and Klotho with echocardiographic parameters and cardiac events in CKD patients.

METHODS

The prospective Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Fourth Homburg Evaluation study recruited CKD G2-G4 patients, of whom 519 consented to SNP genotyping (FGFR4: rs351855; Klotho: rs9536314). Echocardiographic examinations at baseline and 5 years later assessed prevalence of LVH by measurement of left-ventricular mass index (LVMI). Patients were followed for 5.1 ± 2.1 years for the primary endpoints of cardiac decompensation and atherosclerotic cardiovascular disease (ASCVD).

RESULTS

Carriers of the different alleles did neither differ in baseline LVMI (rs351855: p = 0.861; rs9536314: p = 0.379) nor in LVMI changes between baseline and follow-up (rs351855: p = 0.181; rs9536314: p = 0.995). Hundred and four patients suffered cardiac decompensation, and 144 patients had ASCVD. Time to cardiac decompensation (rs351855: p = 0.316; rs9536314: p = 0.765) and ASCVD (p = 0.508 and p = 0.800, respectively) did not differ between carriers of different alleles.

DISCUSSION/CONCLUSION

rs351855 and rs9536314 were not associated with LVMI or cardiac events. These findings do not provide evidence for a relevant clinical role of either FGFR4 stimulation or soluble form of Klotho deficiency in LVH development.

Randomized comparison of three high-flux dialyzers during high-volume online hemodiafiltration—the comPERFORM study

Background

Dialyzers should be designed to efficiently eliminate uraemic toxins during dialysis treatment, given that the accumulation of small and middle molecular weight uraemic solutes is associated with increased mortality risk of patients with end-stage renal disease. In the present study we investigated the novel FX CorAL dialyzer with a modified membrane surface for performance during online hemodiafiltration (HDF) in a clinical setting.

Methods

comPERFORM was a prospective, open, controlled, multicentric, interventional, crossover study with randomized treatment sequences. It randomized stable patients receiving regular post-dilution online HDF to FX CorAL 600 (Fresenius Medical Care Deutschland), xevonta Hi 15 (B. Braun) and ELISIO 150H (Nipro) each for 1 week. The primary outcome was β2-m removal rate (β2-m RR) during online HDF. Secondary endpoints were RR and/or clearance of β2-m and other molecules. Albumin removal over time was an exploratory endpoint. Non-inferiority and superiority of FX CorAL 600 versus comparators were tested.

Results

Fifty-two patients were included and analysed. FX CorAL 600 showed the highest β2-m RR (75.47%), followed by xevonta Hi 15 (74.01%) and ELISIO 150H (72.70%). Superiority to its comparators was statistically significant (P = 0.0216 and P < 0.0001, respectively). Secondary endpoints related to middle molecules affirmed these results. FX CorAL 600 demonstrated the lowest albumin removal up to 60 minutes and its sieving properties changed less over time than with comparators.

Conclusions

FX CorAL 600 efficiently removed middle and small molecules and was superior to the two comparators in β2-m RR. Albumin sieving kinetics point to reduced formation of a secondary membrane.

Polyvinylpyrrolidone in hemodialysis membranes: Impact on platelet loss during hemodialysis

INTRODUCTION

Hydrophilic modification with polyvinylpyrrolidone (PVP) increases the biocompatibility profile of synthetic dialysis membranes. However, PVP may be eluted into the patient's blood, which has been discussed as a possible cause for adverse reactions rarely occurring with synthetic membranes. We investigated the content of PVP and its elution from the blood-side surface from commercially available dialyzers, including the novel FX CorAL, with PVP-enriched and α-tocopherol-stabilized membrane, and link the results to the level of platelet loss during dialysis as a maker of biocompatibility.

METHODS

Six synthetic, PVP containing, dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO [Nipro]; xevonta [B. Braun]) were investigated in the present study. The content of PVP on blood-side surface was determined with X-ray photoelectron spectroscopy (XPS). The amount of elutable PVP was measured photometrically after 5 h recirculation. The level of platelet loss was evaluated in an ex vivo recirculation model with human blood.

FINDINGS

Highest PVP content on the blood-side surface was found for the polysulfone-based FX CorAL (26.3%), while the polyethersulfone-based THERANOVA (15.6%) had the lowest PVP content. Elution of PVP was highest for the autoclave steam-sterilized THERANOVA (9.1 mg/1.6 m² dialyzer) and Polyflux (9.0 mg/1.6 m² dialyzer), while the lowest PVP elution was found for the INLINE steam sterilized FX CorAL and FX CorDiax (<0.5 mg/1.6 m² dialyzer, for both). Highest platelet loss was found for xevonta (+164.4% compared to the reference) and the lowest for the FX CorAL (-225.2%) among the polysulfone-based dialyzers; among the polyethersulfone-based dialyzers, THERANOVA (+95.5%) had the highest and ELISIO (-52.1%) the lowest platelet loss.

DISCUSSION

Polyvinylpyrrolidone content and elution differ between commercially available dialyzers and were found to be linked to the membrane material and sterilization method. The amount of non-eluted PVP on the blood-side surface may be an important determinant for the biocompatibility of dialyzers.

Evolution of body composition and wasting indicators by time of day of haemodialysis

BACKGROUND

It has been a long-standing clinical concern that haemodialysis (HD) patients on afternoon shifts (ASs) are more prone to protein-energy wasting (PEW) than those on morning shifts (MSs), as their dialysis scheme and post-dialysis symptoms may interfere with meal intake. We evaluated the effect of time of day of HD on the evolution of body composition changes and PEW surrogates.

METHODS

We conducted a retrospective study among 9.963 incident HD patients treated in NephroCare centres (2011-16); data were routinely collected in the European Clinical Database. The course of multi-frequency bioimpedance determined lean and fat tissue indices (LTI and FTI) between patients in MSs/ASs over 2 years were compared with linear mixed models. Secondary PEW indicators were body mass index, albumin, creatinine index and normalized protein catabolic rate. Models included fixed (age, sex, vascular access and diabetes mellitus) and random effects (country and patient).

RESULTS

Mean baseline LTI and FTI were comparable between MSs (LTI: 12.5 ± 2.9 kg/m2 and FTI: 13.7 ± 6.0 kg/m2) and ASs (LTI: 12.4 ± 2.9 kg/m2 and FTI: 13.2 ± 6.1 kg/m2). During follow-up, LTI decreased and FTI increased similarly, with a mean absolute change (baseline to 24 months) of -0.3 kg/m2 for LTI and +1.0 kg/m2 for FTI. The course of these malnutrition indicators did not differ between dialysis shifts (P for interaction ≥0.10). We also did not observe differences between groups for secondary PEW indicators.

CONCLUSIONS

This study suggests that a dialysis shift in the morning or in the afternoon does not impact the long-term nutritional status of HD patients. Regardless of time of day of HD, patients progressively lose muscle mass and increase body fat.

Performance and Hemocompatibility of a Novel Polysulfone Dialyzer: A Randomized Controlled Trial

Background

High-flux dialyzers effectively remove uremic toxins, are hemocompatible to minimize intradialytic humoral and cellular stimulation, and have long-term effects on patient outcomes. A new dialyzer with a modified membrane surface has been tested for performance and hemocompatibility.

Methods

This multicenter, prospective, randomized, crossover study involved the application of the new polysulfone-based FX CorAL 600 (Fresenius Medical Care, Bad Homburg, Germany), the polyarylethersulfone-based Polyflux 170H (Baxter Healthcare Corporation, Deerfield, IL), and the cellulose triacetate–based SureFlux 17UX (Nipro Medical Europe, Mechelen, Belgium), for 1 week each, to assess the noninferiority of the FX CorAL 600’s removal rate of β2-microglobulin. Performance was assessed by removal rate and clearance of small- and medium-sized molecules. Hemocompatibility was assessed through markers of complement, cell activation, contact activation, and coagulation.

Results

Of 70 patients, 58 composed the intention-to-treat population. The FX CorAL 600’s removal rate of β2-microglobulin was noninferior to both comparators (P<0.001 versus SureFlux 17UX; P=0.0006 versus Polyflux 170H), and superior to the SureFlux 17UX. The activation of C3a and C5a with FX CorAL 600 was significantly lower 15 minutes after treatment start than with SureFlux 17UX. The activation of sC5b-9 with FX CorAL 600 was significantly lower over the whole treatment than with SureFlux 17UX, and lower after 60 minutes than with the Polyflux 170H. The treatments with FX CorAL 600 were well tolerated.

Conclusions

FX CorAL 600 efficiently removed small- and medium-sized molecules, showed a favorable hemocompatibility profile, and was associated with a low frequency of adverse events in this study, with a limited patient number and follow-up time. Further studies, with longer observation times, are warranted to provide further evidence supporting the use of the new dialyzer in a wide range of therapeutic options, and for long-term treatment of patients on hemodialysis, to minimize the potential effects on inflammatory processes.

Complement activation by dialysis membranes and its association with secondary membrane formation and surface charge

Activation of the complement system may occur during blood-membrane interactions in hemodialysis and contribute to chronic inflammation of patients with end-stage renal disease. Hydrophilic modification with polyvinylpyrrolidone (PVP) has been suggested to increase the biocompatibility profile of dialysis membranes. In the present study we compared the complement activation of synthetic and cellulose-based membranes, including the polysulfone membrane with α-tocopherol-stabilized PVP-enriched inner surface of the novel FX CorAL dialyzer, and linked the results to their physical characteristics. Eight synthetic and cellulose-based dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO, SUREFLUX [Nipro]; xevonta [B. Braun]; FDX [Nikkisio Medical]) were investigated in the present study. Complement activation (C3a, C5a, and sC5b-9) was evaluated in a 3 hours ex vivo recirculation model with human blood. Albumin sieving coefficients were determined over a 4 hours ex vivo recirculation model with human plasma as a surrogate of secondary membrane formation. Zeta potential was measured as an indicator for the surface charge of the membranes. The FX CorAL dialyzer induced the lowest activation of the three complement factors (C3a: -39.4%; C5a: -57.5%; and sC5b-9: -58.9% compared to the reference). Highest complement activation was found for the cellulose-based SUREFLUX (C3a: +154.0%) and the FDX (C5a: +335.0% and sC5b-9: +287.9%) dialyzers. Moreover, the FX CorAL dialyzer had the nearest-to-neutral zeta potential (-2.38 mV) and the lowest albumin sieving coefficient decrease over time. Albumin sieving coefficient decrease was associated with complement activation by the investigated dialyzers. Our present results indicate that the surface modification implemented in the FX CorAL dialyzer reduces the secondary membrane formation and improves the biocompatibility profile. Further clinical studies are needed to investigate whether these observations will result in a lower inflammatory burden of hemodialysis patients.

Serum Uric Acid and Mortality Risk Among Hemodialysis Patients

INTRODUCTION

Although high serum uric acid (SUA) has been consistently associated with an increased risk of death in the general population and in persons with nondialysis chronic kidney disease (CKD), studies in patients undergoing dialysis are conflicting. It has been postulated that low SUA simply reflects poor nutritional status in dialysis patients. We here characterize the association between SUA and the risk of death in a large dialysis cohort and explore effect modification by underlying nutritional status as reflected by body composition.

METHODS

In this retrospective cohort study, we included 16,057 hemodialysis (HD) patients treated during 2007 to 2016 in NephroCare centers as recorded in the European Clinical Database (EuCliD). The association between SUA, all-cause, and cardiovascular (CV)-related mortality was evaluated with competing risk models and characterized with splines. Effect modification was explored by lean tissue index (LTI) and fat tissue index (FTI).

RESULTS

During a mean of 1.8 years of follow-up, 2791 patients (17.4%) died. We found a multivariable-adjusted U-shaped pattern between SUA and all-cause mortality. Patients with SUA levels of 6.5 mg/dl (387 μmol/l) were at the lowest risk of death (subdistribution hazard ratio = 0.94 [confidence interval {CI} 0.91; 0.96]). The form of association was not meaningfully affected by underlying LTI and FTI.

CONCLUSION

We found a U-shaped pattern between SUA levels and all-cause mortality among HD patients, which was independent of the patients' body composition.

Epigenetics in non-classical monocytes support their pro-inflammatory gene expression

Non-classical human monocytes are characterized by high-level expression of cytokines like TNF, but the mechanisms involved are elusive. We have identified miRNAs and CpG-methylation sites that are unique to non-classical monocytes, defined via CD14 and CD16 expression levels. For down-regulated miRNAs that are linked to up-regulated mRNAs the dominant gene ontology term was intracellular signal transduction. This included down-regulated miRNA-20a-5p and miRNA-106b-5p, which both are linked to increased mRNA for the TRIM8 signaling molecule. Methylation analysis revealed 16 hypo-methylated CpG sites upstream of 14 differentially increased mRNAs including 2 sites upstream of TRIM8. Consistent with a positive role in signal transduction, high TRIM8 levels went along with high basal TNF mRNA levels in non-classical monocytes. Since cytokine expression levels in monocytes strongly increase after stimulation with toll-like-receptor ligands, we have analyzed non-classical monocytes (defined via slan expression) after stimulation with lipopolysaccharide (LPS). LPS-stimulated cells continued to have low miRNA-20a and miRNA-106b and high TRIM8 mRNA levels and they showed a 10-fold increase in TNF mRNA. These data suggest that decreased miRNAs and CpG hypo-methylation is linked to enhanced expression of TRIM8 and that this can contribute to the increased TNF levels in non-classical human monocytes.

Effects of high-volume online mixed-hemodiafiltration on anemia management in dialysis patients

Background

Anemia is a major comorbidity of patients with end-stage renal disease and poses an enormous economic burden to health-care systems. High dose erythropoiesis-stimulating agents (ESAs) have been associated with unfavorable clinical outcomes. We explored whether mixed-dilution hemodiafiltration (Mixed-HDF), based on its innovative substitution modality, may improve anemia outcomes compared to the traditional post-dilution hemodiafiltration (Post-HDF).

Methods

We included 174 adult prevalent dialysis patients (87 on Mixed-HDF, 87 on Post-HDF) treated in 24 NephroCare dialysis centers between January 2010 and August 2016 into this retrospective cohort study. All patients were dialyzed three times per week and had fistula/graft as vascular access. Patients were matched at baseline and followed over a one-year period. The courses of hemoglobin levels (Hb) and monthly ESA consumption were compared between the two groups with linear mixed models.

Results

Mean baseline Hb was 11.9±1.3 and 11.8±1.1g/dl in patients on Mixed- and Post-HDF, respectively. While Hb remained stable in patients on Mixed-HDF, it decreased slightly in patients on Post-HDF (at month 12: 11.8±1.2 vs 11.1±1.2g/dl). This tendency was confirmed by our linear mixed model (p = 0.0514 for treatment x time interaction). Baseline median ESA consumption was 6000 [Q1:0;Q3:16000] IU/4 weeks in both groups. Throughout the observation period ESA doses tended to be lower in the Mixed-HDF group (4000 [Q1:0;Q3:16000] vs 8000 [Q1:0;Q3:20000] IU/4 weeks at month 12; p = 0.0791 for treatment x time interaction). Sensitivity analyses, adjusting for differences not covered by matching at baseline, strengthened our results (Hb: p = 0.0124; ESA: p = 0.0687).

Conclusions

Results of our explorative study suggest that patients on Mixed-HDF may have clinical benefits in terms of anemia management. This may also have a beneficial economic impact. Future studies are needed to confirm our hypothesis-generating results and to provide additional evidence on the potential beneficial effects of Mixed-HDF.

Clinical outcomes of hemodialysis patients in a public-private partnership care framework in Italy: a retrospective cohort study

Background

Innovative care models such as public-private partnerships (PPPs) may help meet the challenge of providing cost-effective high-quality care for the steadily growing and complex chronic kidney disease population since they combine the expertise and efficiency of a specialized dialysis provider with the population care approach of a public entity. We report the five-years main clinical outcomes of a population of patients treated on hemodialysis within a PPP-care model in Italy.

Methods

This descriptive retrospective cohort study consisted of all consecutive hemodialysis patients treated in the NephroCare-operated Nephrology and Dialysis unit of the Seriate Hospital in 2012–2016, which exercises a PPP-care model. Clinical and treatment information was obtained from the European Clinical Database. Hospitalization outcomes and cumulative all-cause mortality incidences that accounted for competing risks were calculated.

Results

We included 401 hemodialysis patients (197 prevalent and 204 incident patients) in our study. The mean cohort age and age-adjusted Charlson Comorbidity Index were 67.0 years and 6.7, respectively. Patients were treated with online high-volume hemodiafiltration or high-flux hemodialysis. Parameters of treatment efficiency were above the recommended targets throughout the study period. Patients in the PPP experienced benefits in terms of hospitalization (average number of hospital admissions/patient-year: 0.79 and 1.13 for prevalent and incident patients, respectively; average length of hospitalization: 8.9 days for both groups) and had low cumulative all-cause mortality rates (12 months: 10.6 and 7.8%, 5 years: 42.0 and 35.9%, for prevalent and incident patients, respectively).

Conclusions

Results of our descriptive study suggest that hemodialysis patients treated within a PPP-care model framework received care complying with recommended treatment targets and may benefit in terms of hospitalization and mortality outcomes.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1224-2) contains supplementary material, which is available to authorized users.

Plasma levels of the oxyphytosterol 7α-hydroxycampesterol are associated with cardiovascular events

BACKGROUND AND AIMS

There are safety issues regarding plant sterol ester-enriched functional food. Oxidized plant sterols, also called oxyphytosterols, are supposed to contribute to plant sterol atherogenicity. This study aimed to analyze associations of plasma oxyphytosterol levels with cardiovascular events.

METHODS

Plasma cholesterol was measured by gas chromatography-flame ionization detection. Plasma campesterol and sitosterol and their 7-oxygenated metabolites were analyzed by gas chromatography-mass selective detection.

RESULTS

In 376 patients admitted for elective coronary angiography, who were not on lipid-lowering drugs, 82 cardiovascular events occurred during a follow-up period of 4.2 ± 1.8 years. Patients with cardiovascular events had significantly higher 7α-hydroxycampesterol plasma levels (median, 0.46; [interquartile range (IQR) 0.22-0.81] nmol/L vs. median, 0.25 [IQR, 0.17-0.61] nmol/L; p = 0.003) and 7α-hydroxycampesterol-to-cholesterol ratios (median 0.08 [IQR, 0.04-0.14] nmol/mmol vs. median, 0.05 [IQR 0.03-0.11] nmol/mmol; p = 0.005) than controls without such events. Patients above the median were characterized by higher cumulative event rates in Kaplan-Meier-analysis (Logrank-test p = 0.084 and p = 0.025) for absolute and cholesterol corrected 7α-hydroxycampesterol, respectively. After adjustment for influencing factors and related lipids, the hazard ratios per one standard deviation of the log-transformed variables (HR) were 1.19 [95% confidence interval (CI), 0.95-1.48], p = 0.132 for 7α-hydroxycampesterol and HR, 1.18 [95% CI, 0.94-1.48], p = 0.154 for 7α-hydroxycampesterol-to-cholesterol ratio. None of the other investigated oxyphytosterols showed an association with cardiovascular events.

CONCLUSIONS

In patients not on lipid-lowering drugs, absolute plasma levels of 7α-hydroxycampesterol and their ratios to cholesterol are associated with cardiovascular events. Further research is required to elucidate the role of OPS in cardiovascular diseases.

HDL functionality and cardiovascular outcome among nondialysis chronic kidney disease patients

CVD remains the leading cause of morbidity and mortality in patients with chronic kidney disease (CKD). CKD profoundly affects HDL composition and functionality, but whether abnormal HDL independently contributes to cardiovascular events in CKD patients remains elusive. In the present study, we assessed whether compositional and functional properties of HDL predict cardiovascular outcome among 526 nondialysis CKD patients who participate in the CARE FOR HOMe study. We measured HDL cholesterol, the content of HDL-associated proinflammatory serum amyloid A (SAA), and activities of the HDL enzymes paraoxonase and lipoprotein-associated phospholipase A2 (Lp-PLA₂). In addition, we assessed the antioxidative activity of apoB-depleted serum. During a mean follow-up of 5.1 ± 2.1 years, 153 patients reached the predefined primary endpoint, a composite of atherosclerotic cardiovascular events including cardiovascular mortality and death of any cause. In univariate Cox regression analyses, lower HDL-cholesterol levels, higher HDL-associated SAA content, and lower paraoxonase activity predicted cardiovascular outcome, while Lp-PLA₂ activity and antioxidative capacity did not. HDL-cholesterol and HDL-paraoxonase activity lost their association with cardiovascular outcome after adjustment for traditional cardiovascular and renal risk factors, while SAA lost its association after further adjustment for C-reactive protein. In conclusion, our data suggest that neither HDL quantity nor HDL composition or function independently predict cardiovascular outcome among nondialysis CKD patients.

Reprint of: MicroRNA profiling of human intermediate monocytes

Among the three human monocyte subsets, intermediate CD14++CD16+ monocytes have been characterized as particularly proinflammatory cells in experimental studies and as potential biomarkers of cardiovascular risk in clinical cohorts. To further substantiate the distinct role of intermediate monocytes within human monocyte heterogeneity, we assessed subset-specific expression of miRNAs as central epigenetic regulators of gene expression. We hypothesized that intermediate monocytes have a distinct miRNA profile compared to classical and non-classical monocytes. By using small RNA-seq we analyzed 662 miRNAs in the three monocyte subsets. We identified 38 miRNAs that are differentially expressed in intermediate monocytes compared to both classical and non-classical monocytes with a p value of <10^-10, of which two miRNAs - miR-6087 (upregulated) and miR-150-5p (downregulated) - differed in their expression more than ten-fold. Pathway analysis of the 38 differentially expressed miRNAs linked intermediate monocytes to distinct biological processes such as gene regulation, cell differentiation, toll-like receptor signaling as well as antigen processing and presentation. Moreover, differentially expressed miRNAs were connected to those genes that we previously identified as markers of intermediate monocytes. In aggregation, we provide first genome-wide miRNA data in the context of monocyte heterogeneity, which substantiate the concept of monocyte trichotomy in human immunity. The identification of miRNAs that are specific for intermediate monocytes may allow to develop strategies, which particularly target this cell population while sparing the other two subsets.

MicroRNA profiling of human intermediate monocytes

Among the three human monocyte subsets, intermediate CD14++CD16+ monocytes have been characterized as particularly proinflammatory cells in experimental studies and as potential biomarkers of cardiovascular risk in clinical cohorts. To further substantiate the distinct role of intermediate monocytes within human monocyte heterogeneity, we assessed subset-specific expression of miRNAs as central epigenetic regulators of gene expression. We hypothesized that intermediate monocytes have a distinct miRNA profile compared to classical and non-classical monocytes. By using small RNA-seq we analyzed 662 miRNAs in the three monocyte subsets. We identified 38 miRNAs that are differentially expressed in intermediate monocytes compared to both classical and non-classical monocytes with a p value of <10^-10, of which two miRNAs - miR-6087 (upregulated) and miR-150-5p (downregulated) - differed in their expression more than ten-fold. Pathway analysis of the 38 differentially expressed miRNAs linked intermediate monocytes to distinct biological processes such as gene regulation, cell differentiation, toll-like receptor signaling as well as antigen processing and presentation. Moreover, differentially expressed miRNAs were connected to those genes that we previously identified as markers of intermediate monocytes. In aggregation, we provide first genome-wide miRNA data in the context of monocyte heterogeneity, which substantiate the concept of monocyte trichotomy in human immunity. The identification of miRNAs that are specific for intermediate monocytes may allow to develop strategies, which particularly target this cell population while sparing the other two subsets.

Effects of rAAV-mediated FGF-2 gene transfer and overexpression upon the chondrogenic differentiation processes in human bone marrow aspirates

Background

Application of genetically modified bone marrow concentrates in articular cartilage lesions is a promising approach to enhance cartilage repair by stimulating the chondrogenic differentiation processes in sites of injury.

Method

In the present study, we examined the potential benefits of transferring the proliferative and pro-chondrogenic basic fibroblast growth factor (FGF-2) to human bone marrow aspirates in vitro using the clinically adapted recombinant adeno-associated virus (rAAV) vectors to monitor the biological and chondrogenic responses over time to the treatment compared with control (lacZ) gene application.

Results

Effective, significant FGF-2 gene transfer and expression via rAAV was established in the aspirates relative to the lacZ condition (from ~ 97 to 36 pg rhFGF-2/mg total proteins over an extended period of 21 days). Administration of the candidate FGF-2 vector led to prolonged increases in cell proliferation, matrix synthesis, and chondrogenesis but also to hypertrophic and terminal differentiation in the aspirates.

Conclusion

The present evaluation shows the advantages of rAAV-mediated FGF-2 gene transfer to conveniently modify bone marrow concentrates as a future approach to directly treat articular cartilage lesions, provided that expression of the growth factor is tightly regulated to prevent premature hypertrophy in vivo.

The Kinetics of Circulating Monocyte Subsets and Monocyte-Platelet Aggregates in the Acute Phase of ST-Elevation Myocardial Infarction: Associations with 2-Year Cardiovascular Events

In experimental myocardial infarction (MI), a rise in cell counts of circulating monocyte subsets contributes to impaired myocardial healing and to atherosclerotic plaque destabilization. In humans, the prognostic role of monocyte subsets in patients suffering ST-elevation MI (STEMI) is still unclear. In the present study, we aimed to determine the kinetics of the 3 monocyte subsets (classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes), as well as the subset-specific monocyte-platelet aggregates (MPA), in acute STEMI followed by primary percutaneous coronary intervention (PCI), and their relationships with cardiovascular outcomes during a 2-year follow-up.Monocyte subsets and MPA were measured in 100 STEMI patients receiving primary PCI on days 1, 2, 3, 5, and 7 of symptom onset, which were compared with 60 stable coronary heart disease patients and 35 healthy volunteers. From day 1 to day 7, significant increases in the counts of CD14++CD16+ monocytes and CD14++CD16+ MPA were observed, with peak levels on day 2. During a median follow-up of 2.0 years, 28 first cardiovascular events (defined as cardiovascular death, nonfatal ischemic stroke, recurrent MI, need for emergency or repeat revascularization, and rehospitalization for heart failure) were recorded. After adjustment for confounders, CD14++CD16+ monocytosis (day 1 [HR: 3.428; 95% CI: 1.597-7.358; P = 0.002], day 2 [HR: 4.835; 95% CI: 1.106-21.13; P = 0.04], day 3 [HR: 2.734; 95% CI: 1.138-6.564; P = 0.02], and day 7 [HR: 2.647; 95% CI: 1.196-5.861; P = 0.02]), as well as increased levels of CD14++CD16+ MPA measured on all time points (days 1, 2, 3, 5, and 7), had predictive values for adverse cardiovascular events.In conclusion, our data show the expansion of the CD14++CD16+ monocyte subset during acute phase of STEMI has predictive values for 2-year adverse cardiovascular outcomes in patients treated with primary PCI. Future studies will be warranted to elucidate whether CD14++CD16+ monocytes may become a target cell population for new therapeutic strategies after STEMI.

DNA methylation profiling reveals differences in the 3 human monocyte subsets and identifies uremia to induce DNA methylation changes during differentiation

Human monocytes are a heterogeneous cell population consisting of 3 subsets: classical CD14++CD16-, intermediate CD14++CD16+ and nonclassical CD14+CD16++ monocytes. Via poorly characterized mechanisms, intermediate monocyte counts rise in chronic inflammatory diseases, among which chronic kidney disease is of particular epidemiologic importance. DNA methylation is a central epigenetic feature that controls hematopoiesis. By applying next-generation Methyl-Sequencing we now tested how far the 3 monocyte subsets differ in their DNA methylome and whether uremia induces DNA methylation changes in differentiating monocytes. We found that each monocyte subset displays a unique phenotype with regards to DNA methylation. Genes with differentially methylated promoter regions in intermediate monocytes were linked to distinct immunological processes, which is in line with results from recent gene expression analyses. In vitro, uremia induced dysregulation of DNA methylation in differentiating monocytes, which affected several transcription regulators important for monocyte differentiation (e.g., FLT3, HDAC1, MNT) and led to enhanced generation of intermediate monocytes. As potential mediator, the uremic toxin and methylation inhibitor S-adenosylhomocysteine induced shifts in monocyte subsets in vitro, and associated with monocyte subset counts in vivo. Our data support the concept of monocyte trichotomy and the distinct role of intermediate monocytes in human immunity. The shift in monocyte subsets that occurs in chronic kidney disease, a proinflammatory condition of substantial epidemiological impact, may be induced by accumulation of uremic toxins that mediate epigenetic dysregulation.

Impact of individual intravenous iron preparations on the differentiation of monocytes towards macrophages and dendritic cells

Background

Treatment of iron deficiency with intravenous (i.v.) iron is a first-line strategy to improve anaemia of chronic kidney disease. Previous in vitro experiments demonstrated that different i.v. iron preparations inhibit differentiation of haematopoietic stem cells to monocytes, but their effect on monocyte differentiation to macrophages and mature dendritic cells (mDCs) has not been assessed. We investigated substance-specific effects of iron sucrose (IS), sodium ferric gluconate (SFG), ferric carboxymaltose (FCM) and iron isomaltoside 1000 (IIM) on monocytic differentiation to M1/M2 macrophages and mDCs.

Methods

Via flow cytometry and microRNA (miRNA) expression analysis, we morphologically and functionally characterized monocyte differentiation to M1/M2 macrophages and mDCs after monocyte stimulation with IS, SFG, FCM and IIM (0.133, 0.266 and 0.533 mg/mL, respectively). To assess potential clinical implications, we compared monocytic phagocytosis capacity in dialysis patients who received either 500 mg IS or IIM.

Results

Phenotypically, IS and SFG dysregulated the expression of macrophage (e.g. CD40, CD163) and mDC (e.g. CD1c, CD141) surface markers. Functionally, IS and SFG impaired macrophage phagocytosis capacity. Phenotypic and functional alterations were less pronounced with FCM, and virtually absent with IIM. In miRNA expression analysis of mDCs, IS dysregulated miRNAs such as miR-146b-5p and miR-155-5p, which are linked to Toll-like receptor and mitogen-activated protein kinase signalling pathways. In vivo, IS reduced monocytic phagocytosis capacity within 1 h after infusion, while IIM did not.

Conclusions

This study demonstrates that less stable i.v. iron preparations specifically affect monocyte differentiation towards macrophages and mDCs.

PCSK9 Plasma Concentrations Are Independent of GFR and Do Not Predict Cardiovascular Events in Patients with Decreased GFR

BACKGROUND

Impaired renal function causes dyslipidemia that contributes to elevated cardiovascular risk in patients with chronic kidney disease (CKD). The proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of the LDL receptor and plasma cholesterol concentrations. Its relationship to kidney function and cardiovascular events in patients with reduced glomerular filtration rate (GFR) has not been explored.

METHODS

Lipid parameters including PCSK9 were measured in two independent cohorts. CARE FOR HOMe (Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Forth Homburg evaluation) enrolled 443 patients with reduced GFR (between 90 and 15 ml/min/1.73 m2) referred for nephrological care that were prospectively followed for the occurrence of a composite cardiovascular endpoint. As a replication cohort, PCSK9 was quantitated in 1450 patients with GFR between 90 and 15 ml/min/1.73 m2 enrolled in the Ludwigshafen Risk and Cardiovascular Health Study (LURIC) that were prospectively followed for cardiovascular deaths.

RESULTS

PCSK9 concentrations did not correlate with baseline GFR (CARE FOR HOMe: r = -0.034; p = 0.479; LURIC: r = -0.017; p = 0.512). 91 patients in CARE FOR HOMe and 335 patients in LURIC reached an endpoint during a median follow-up of 3.0 [1.8-4.1] years and 10.0 [7.3-10.6] years, respectively. Kaplan-Meier analyses showed that PCSK9 concentrations did not predict cardiovascular events in either cohort [CARE FOR HOMe (p = 0.622); LURIC (p = 0.729)]. Sensitivity analyses according to statin intake yielded similar results.

CONCLUSION

In two well characterized independent cohort studies, PCSK9 plasma levels did not correlate with kidney function. Furthermore, PCSK9 plasma concentrations were not associated with cardiovascular events in patients with reduced renal function.

External Validation of the Kidney Failure Risk Equation and Re-Calibration with Addition of Ultrasound Parameters

BACKGROUND AND OBJECTIVES

Progression of CKD toward ESRD is heterogeneous. The Kidney Failure Risk Equation (KFRE) was developed to identify CKD patients at high risk of ESRD. We aimed to externally validate KFRE and to test whether the addition of predefined Duplex ultrasound markers - renal resistive index (RRI) or difference of resistive indices in spleen and kidney (DI-RISK) - improved ESRD prediction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The prospective Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Fourth Homburg evaluation (CARE FOR HOMe) study recruits CKD stage G2-G4 patients referred to a tertiary referral center for nephrologic care. Four hundred three CARE FOR HOMe participants enrolled between 2008 and 2012 had available RRI measurements at study inclusion; they were subsequently followed for a mean of 4.4±1.6 years. This subcohort was used to validate KFRE and to assess the added value of the ultrasound markers (new models KFRE+RRI and KFRE+DI-RISK). Model performance was assessed by log-likelihood ratio test, c-statistic, integrated discrimination improvement metrics (for study participants without subsequent ESRD [IDI No ESRD] and for patients with ESRD [IDI ESRD]), and calibration plots. If either new model improved on KFRE, we determined to validate it in an independent cohort of 162 CKD patients.

RESULTS

KFRE predicted ESRD in CARE FOR HOMe participants with a c-statistic of 0.91 (95% confidence interval, 0.83 to 0.99). Adding RRI improved the KFRE model (P<0.001), and the KFRE+RRI model was well calibrated; however, the c-statistic (0.91 [0.83-1.00]) was similar, and overall sensitivity (IDI No ESRD=0.05 [0.00-0.10]) or overall specificity (IDI ESRD=0.00 [0.00-0.01]) did not improve. Adding DI-RISK did not improve the KRFE model. In the external validation cohort, we confirmed that the KFRE+RRI model did not outperform KFRE.

CONCLUSIONS

Routine Duplex examinations among CKD patients did not improve risk prediction for progression to ESRD beyond a validated equation.

Comparison of two different strategies for human monocyte subsets gating within the large-scale prospective CARE FOR HOMe Study

Monocytes are heterogeneous cells consisting of (at least) three subsets: classical, intermediate, and nonclassical monocytes. Correct enumeration of cell counts necessitates well-defined gating strategies, which are essentially based upon CD14 and CD16 expression. For the delineation of intermediate from nonclassical monocytes, a "rectangular gating (RG) strategy" and a "trapezoid gating (TG) strategy" have been proposed. We compared the two gating strategies in a well-defined clinical cohort of patients with chronic kidney disease (CKD). Within the ongoing CARE FOR HOMe study, monocyte subsets were reanalyzed in 416 CKD patients, who were followed 3.6 ± 1.6 years for the occurrence of a cardiovascular event. Gating was performed by either RG or TG. We analyzed the expression of surface markers, and compared the predictive role of cell counts of monocyte subsets, as defined by RG and TG, respectively. With both gating strategies, higher intermediate monocyte counts predicted the cardiovascular endpoint in Kaplan-Meier analyses (P < 0.001 with RG; P < 0.001 with TG). After correction for confounders, intermediate monocyte counts remained independent predictors in Cox-Regression analyses (HR = 1.013 [95% CI: 1.006-1.020; P < 0.001] with RG; HR = 1.015 [95% CI: 1.006-1.024; P = 0.001] with TG). NRI was 3.9% when reclassifying patients from quartiles of intermediate monocyte counts with RG strategy toward quartiles of intermediate monocytes counts with TG strategy. In expression analysis, those monocytes which are defined as intermediate monocytes by the RG strategy and as nonclassical monocytes by the TG strategy share characteristics of both subsets. In conclusion, intermediate monocytes were independent predictors of cardiovascular outcome irrespective of the applied gating strategy. Future studies should aim to identify markers that allow for an unequivocal definition of intermediate monocytes, which may further improve their power to predict cardiovascular events.

Comparative analysis of assays for detection of cell-mediated immunity toward cytomegalovirus and M. tuberculosis in samples from deceased organ donors

Cell-mediated immunity assays could be valuable for risk assessment of organ donors, but no data exist on their feasibility in deceased donors. In this study, 105 deceased donors (52.3 ± 16.9 years) were screened at the time of organ procurement. Pathogen-specific stimulation was performed using a cytomegalovirus (CMV) lysate, tuberculin (purified protein derivative [PPD]) and soluble Mycobacterium tuberculosis-specific ESAT-6/CFP-10 proteins in combination with an in-house fluorescence-activated cell sorting (FACS) assay or commercial assay formats (QuantiFERON-CMV/TB for ELISA, T-SPOT.TB for ELISPOT). CMV-IgG antibody titers were determined as gold standard for CMV infection; 51.4% of samples were CMV seropositive. Indeterminate results were observed in 47.6% of ELISA, 12.5% of FACS and 0% of ELISPOT assays. Agreement with serology was highest for FACS (95.6%, κ = 0.91), followed by ELISPOT (84.0%, κ = 0.68) and ELISA (80.0%, κ = 0.60). Agreement between ELISA and serology increased if the CMV lysate was used as stimulus (96.7%, κ = 0.92). Among the T cell assays, agreement between ELISPOT and FACS was highest (κ = 0.70). PPD-positive results among valid samples differed between assays (26.5% for ELISA, 23.1% for FACS and 50.5% for ELISPOT); 2.0% were QuantiFERON-TB positive, 3.3% were ESAT-6/CFP-10-positive in FACS and 13.4% were positive in the T-SPOT.TB assay. In conclusion, cellular immunity may be analyzed from samples of deceased donors, although the assays differ in the rate of positivity and indeterminate results.

Lower Apo A-I and lower HDL-C levels are associated with higher intermediate CD14++CD16+ monocyte counts that predict cardiovascular events in chronic kidney disease

OBJECTIVE

Patients with chronic kidney disease (CKD) display impaired cholesterol efflux capacity and elevated CD14(++)CD16(+) monocyte counts. In mice, dysfunctional cholesterol efflux causes monocytosis. It is unknown whether cholesterol efflux capacity and monocyte subsets are associated in CKD.

APPROACH AND RESULTS

In 438 patients with CKD, mediators of cholesterol efflux capacity (high-density lipoprotein cholesterol/apolipoprotein A-I) and monocyte subsets were analyzed as predictors of cardiovascular events. Monocyte subset-specific intracellular lipid content, CD36, CD68, and ABCA1 were measured in a subgroup. Experimentally, we analyzed subset-specific cholesterol efflux capacity and response to oxidized low-density lipoprotein cholesterol stimulation in CKD. Epidemiologically, both low Apo-I and low high-density lipoprotein cholesterol were associated with high CD14(++)CD16(+) monocyte counts in linear regression analyses (apolipoprotein A-I: β=-0.171; P<0.001; high-density lipoprotein cholesterol: β=-0.138; P=0.005), but not with counts of other monocyte subsets. In contrast to apolipoprotein A-I or high-density lipoprotein cholesterol, higher CD14(++)CD16(+) monocyte counts independently predicted cardiovascular events (hazard ratio per increase of 1 cell/μL: 1.011 [1.003-1.020]; P=0.007). Experimentally, CD14(++)CD16(+) monocytes demonstrated preferential lipid accumulation, high CD36, CD68, and low ABCA1 expression and, consequently, displayed low cholesterol efflux capacity, avid oxidized low-density lipoprotein cholesterol uptake, and potent intracellular interleukin-6, interleukin-1β, and tumor necrosis factor-α production.

CONCLUSIONS

Taken together, mediators of cholesterol efflux are associated with CD14(++)CD16(+) monocyte counts, which independently predict adverse outcome in CKD.

APADB: a database for alternative polyadenylation and microRNA regulation events

Alternative polyadenylation (APA) is a widespread mechanism that contributes to the sophisticated dynamics of gene regulation. Approximately 50% of all protein-coding human genes harbor multiple polyadenylation (PA) sites; their selective and combinatorial use gives rise to transcript variants with differing length of their 3′ untranslated region (3′UTR). Shortened variants escape UTR-mediated regulation by microRNAs (miRNAs), especially in cancer, where global 3′UTR shortening accelerates disease progression, dedifferentiation and proliferation. Here we present APADB, a database of vertebrate PA sites determined by 3′ end sequencing, using massive analysis of complementary DNA ends. APADB provides (A)PA sites for coding and non-coding transcripts of human, mouse and chicken genes. For human and mouse, several tissue types, including different cancer specimens, are available. APADB records the loss of predicted miRNA binding sites and visualizes next-generation sequencing reads that support each PA site in a genome browser. The database tables can either be browsed according to organism and tissue or alternatively searched for a gene of interest. APADB is the largest database of APA in human, chicken and mouse. The stored information provides experimental evidence for thousands of PA sites and APA events. APADB combines 3′ end sequencing data with prediction algorithms of miRNA binding sites, allowing to further improve prediction algorithms. Current databases lack correct information about 3′UTR lengths, especially for chicken, and APADB provides necessary information to close this gap.

Database URL:http://tools.genxpro.net/apadb/

Distinct immunologic effects of different intravenous iron preparations on monocytes

Background

Iron deficiency contributes to anaemia in patients with chronic kidney disease. I.v. iron is therefore widely used for anaemia treatment, although it may induce oxidative stress and activate monocytes. Different i.v. iron preparations are available, but interestingly their substance-specific immunologic effects are poorly studied.

Methods

We analysed the effect of iron sucrose, ferric carboxymaltose, iron isomaltoside 1000, low-molecular-weight iron dextran and ferumoxytol on classical, intermediate and nonclassical monocyte biology. We therefore stimulated in vitro mature monocytes and haematopoietic CD34⁺ stem cells during their differentiation into monocytes with different concentrations (0.133, 0.266, 0.533 mg/mL) of i.v. iron preparations. Alterations of monocyte subset distribution, expression of surface markers (CD86, CCR5, CX₃CR1), as well as production of pro-inflammatory cytokines (TNF-α, IL-1β) and reactive oxygen species were measured using flow cytometry. Additionally, we analysed phagocytosis and antigen presentation capacity.

Results

We found specific immunologic effects after stimulation with iron sucrose which were not induced by the other iron preparations. Iron sucrose activated monocyte subsets leading to significantly increased CD86 expression. Simultaneously CD16 and CX₃CR1 expression and monocytic phagocytosis capacity were decreased. Additionally, differentiation of monocytes from haematopoietic CD34⁺ stem cells was almost completely abolished after stimulation with iron sucrose.

Conclusions

Our findings demonstrate that specific immunologic effects of distinct i.v. iron preparations exist. The clinical relevance of these findings requires further investigation.

Massive analysis of cDNA Ends (MACE) and miRNA expression profiling identifies proatherogenic pathways in chronic kidney disease

Epigenetic dysregulation contributes to the high cardiovascular disease burden in chronic kidney disease (CKD) patients. Although microRNAs (miRNAs) are central epigenetic regulators, which substantially affect the development and progression of cardiovascular disease (CVD), no data on miRNA dysregulation in CKD-associated CVD are available until now. We now performed high-throughput miRNA sequencing of peripheral blood mononuclear cells from ten clinically stable hemodialysis (HD) patients and ten healthy controls, which allowed us to identify 182 differentially expressed miRNAs (e.g., miR-21, miR-26b, miR-146b, miR-155). To test biological relevance, we aimed to connect miRNA dysregulation to differential gene expression. Genome-wide gene expression profiling by MACE (Massive Analysis of cDNA Ends) identified 80 genes to be differentially expressed between HD patients and controls, which could be linked to cardiovascular disease (e.g., KLF6, DUSP6, KLF4), to infection / immune disease (e.g., ZFP36, SOCS3, JUND), and to distinct proatherogenic pathways such as the Toll-like receptor signaling pathway (e.g., IL1B, MYD88, TICAM2), the MAPK signaling pathway (e.g., DUSP1, FOS, HSPA1A), and the chemokine signaling pathway (e.g., RHOA, PAK1, CXCL5). Formal interaction network analysis proved biological relevance of miRNA dysregulation, as 68 differentially expressed miRNAs could be connected to 47 reciprocally expressed target genes. Our study is the first comprehensive miRNA analysis in CKD that links dysregulated miRNA expression with differential expression of genes connected to inflammation and CVD. After recent animal data suggested that targeting miRNAs is beneficial in experimental CVD, our data may now spur further research in the field of CKD-associated human CVD.

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation incorporating both cystatin C and creatinine best predicts individual risk: a cohort study in 444 patients with chronic kidney disease

BACKGROUND

The recently introduced CKD-EPIcreat-cys equation surpassed creatinine-based equations for GFR estimation in a large cross-sectional analysis. However, its performance to predict individual risk of CKD progression and death in patients with various underlying CKD etiologies is unknown.

METHODS

We recruited 444 patients with CKD GFR categories 2-4 (eGFR 15-89 mL/min/1.73 m2); baseline eGFR was estimated by the established MDRD and CKD-EPIcreat equations and by the novel CKD-EPIcreat-cys equation.

RESULTS

Patients were followed for 2.7±1.2 years for the occurrence of the combined predefined endpoint event: death, need for renal replacement therapy or halving of eGFR. The endpoint occurred in 62 patients. Reclassification from MDRD determined categories to CKD-EPIcreat-cys categories yielded net reclassification improvements for those with the endpoint event (NRIevents) of 27.4% (95% CI: 16.7-40.0%) and for those without the event (NRInon-events) of -3.1% (-8.2 to 1.6%). Similarly, reclassification from CKD-EPIcreat categories to CKD-EPIcreat-cys categories yielded an NRIevents of 22.6% (10.2-34.3%) and NRInon-events of -11.3% (-15.9 to -6.5%). Addition of albuminuria to each eGFR equation increased the calculated risk of the outcome for a net 26-32% of those who subsequently reached the endpoint, and reduced the calculated risk in a net 21-23% in non-event patients, but only minimally.

CONCLUSIONS

The CKD-EPIcreat-cys equation assigned patients who went on to have the event to more appropriate CKD risk categories than MDRD and CKD-EPIcreat, but patients without the event to less appropriate categories than CKD-EPIcreat. Addition of albuminuria marginally improved risk classification for those who had the event.

Clinical relevance of epigenetic dysregulation in chronic kidney disease-associated cardiovascular disease

Across the spectrum of clinical medicine, the field of epigenetics has gained substantial scientific interest in recent years. Epigenetics refers to modifications in gene expression which are not explained by changes in DNA sequence. Classical components of epigenetic regulation comprise DNA methylation, histone modifications and RNA interference. In chronic kidney disease (CKD), several features of uraemia, such as hyperhomocysteinemia and inflammation, may contribute to changes in epigenetic gene regulation. It has been suggested that these changes may affect genes related to cardiovascular disease. Thereby, a uraemia-associated disturbance in epigenetic regulation may contribute to the substantial increase in cardiovascular morbidity in CKD patients. The present review aims to summarize current knowledge of epigenetic dysregulation in cardiovascular disease from a nephrological perspective, with a special focus on DNA methylation. We first describe the impact of altered epigenetic regulation in non-CKD-associated arteriosclerosis, and next characterize uraemic features which may affect epigenetic gene regulation in the context of cardiovascular disease. Finally, we conclude that substantial additional work is needed before epigenetic regulatory mechanisms may become therapeutic targets in CKD-associated cardiovascular disease.

SuperTAG methylation-specific digital karyotyping reveals uremia-induced epigenetic dysregulation of atherosclerosis-related genes

BACKGROUND

Accelerated atherosclerosis is a hallmark of chronic kidney disease (CKD). Although the role of epigenetic dysregulation in atherosclerosis is increasingly appreciated, only a few studies focused on epigenetics in CKD-associated cardiovascular disease, virtually all of which assessed epigenetic dysregulation globally. We hypothesized that gene-specific epigenetic dysregulation in CKD exists, affecting genes pertinent to inflammation and atherosclerosis.

METHODS AND RESULTS

Ten clinically stable patients undergoing hemodialysis therapy and 10 healthy age- and sex-matched controls were recruited. Genome-wide analysis of DNA methylation was performed by SuperTAG methylation-specific digital karyotyping, in order to identify genes differentially methylated in CKD. Analysis of 27 043 436 tags revealed 4288 genomic loci with differential DNA methylation (P<10(-10)) between hemodialysis patients and control subjects. Annotation of UniTags to promoter databases allowed us to identify 52 candidate genes associated with cardiovascular disease and 97 candidate genes associated with immune/infection diseases. These candidate genes could be classified to distinct proatherogenic processes, including lipid metabolism and transport (eg, HMGCR, SREBF1, LRP5, EPHX2, and FDPS), cell proliferation and cell-cycle regulation (eg, MIK67, TP53, and ALOX12), angiogenesis (eg, ANGPT2, ADAMTS10, and FLT4), and inflammation (eg, TNFSF10, LY96, IFNGR1, HSPA1A, and IL12RB1).

CONCLUSIONS

We provide a comprehensive analysis of genome-wide epigenetic alterations in CKD, identifying candidate genes associated with proatherogenic and inflammatory processes. These results may spur further research in the field of epigenetics in kidney disease and point to new therapeutic strategies in CKD-associated atherosclerotic disease.

SuperTAG methylation-specific digital karyotyping reveals uremia-induced epigenetic dysregulation of atherosclerosis-related genes

BACKGROUND

Accelerated atherosclerosis is a hallmark of chronic kidney disease (CKD). Although the role of epigenetic dysregulation in atherosclerosis is increasingly appreciated, only a few studies focused on epigenetics in CKD-associated cardiovascular disease, virtually all of which assessed epigenetic dysregulation globally. We hypothesized that gene-specific epigenetic dysregulation in CKD exists, affecting genes pertinent to inflammation and atherosclerosis.

METHODS AND RESULTS

Ten clinically stable patients undergoing hemodialysis therapy and 10 healthy age- and sex-matched controls were recruited. Genome-wide analysis of DNA methylation was performed by SuperTAG methylation-specific digital karyotyping, in order to identify genes differentially methylated in CKD. Analysis of 27 043 436 tags revealed 4288 genomic loci with differential DNA methylation (P<10(-10)) between hemodialysis patients and control subjects. Annotation of UniTags to promoter databases allowed us to identify 52 candidate genes associated with cardiovascular disease and 97 candidate genes associated with immune/infection diseases. These candidate genes could be classified to distinct proatherogenic processes, including lipid metabolism and transport (eg, HMGCR, SREBF1, LRP5, EPHX2, and FDPS), cell proliferation and cell-cycle regulation (eg, MIK67, TP53, and ALOX12), angiogenesis (eg, ANGPT2, ADAMTS10, and FLT4), and inflammation (eg, TNFSF10, LY96, IFNGR1, HSPA1A, and IL12RB1).

CONCLUSIONS

We provide a comprehensive analysis of genome-wide epigenetic alterations in CKD, identifying candidate genes associated with proatherogenic and inflammatory processes. These results may spur further research in the field of epigenetics in kidney disease and point to new therapeutic strategies in CKD-associated atherosclerotic disease.

CD14++CD16+ monocytes independently predict cardiovascular events: a cohort study of 951 patients referred for elective coronary angiography

OBJECTIVES

The aim of this study was to analyze the yet ill-defined relationship of distinct human monocyte subsets with cardiovascular outcomes in a broad patient population at cardiovascular risk.

BACKGROUND

Monocytes, the most abundant immune cell type found in atherosclerotic plaques, are crucial promoters of atherogenesis. Three distinct human monocyte subsets exist: classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes. Immunomodulation of distinct monocyte subsets has recently been discussed as a new therapeutic avenue in atherosclerosis.

METHODS

Cardiovascular events in 951 subjects referred for elective coronary angiography were prospectively analyzed. Monocyte subset analysis was performed using flow cytometry, blinded to patients' clinical characteristics, and patients were categorized according to quartiles of total monocyte and monocyte subset counts. The primary endpoint was defined a priori as the first occurrence of cardiovascular death, acute myocardial infarction, or nonhemorrhagic stroke. Endpoint adjudication was done blinded to monocyte subset distribution.

RESULTS

During a mean follow-up period of 2.6 ± 1.0 years, 93 patients experienced the primary endpoint. In univariate Kaplan-Meier analysis, counts of total (p = 0.010), classical CD14++CD16- (p = 0.024), and intermediate CD14++CD16+ (p < 0.001) monocytes predicted the primary endpoint, whereas nonclassical monocytes did not (p = 0.158). After full adjustment for confounders, CD14++CD16+ monocytes remained the only monocyte subset independently related to cardiovascular events (fourth vs. first quartile: hazard ratio: 3.019; 95% confidence interval: 1.315 to 6.928; p = 0.009).

CONCLUSIONS

CD14++CD16+ monocytes independently predicted cardiovascular events in subjects referred for elective coronary angiography. Future studies will be needed to elucidate whether CD14++CD16+ monocytes may become a target cell population for new therapeutic strategies in atherosclerosis.

CD14++CD16+ monocytes and cardiovascular outcome in patients with chronic kidney disease

AIMS

Patients with chronic kidney disease (CKD) pose a worldwide growing burden to health care systems due to accelerated atherosclerosis and subsequent high cardiovascular (CV) morbidity. Atherogenesis is prominently driven by monocytes and monocyte-derived macrophages. The expression of CD14 and CD16 characterizes three monocyte subsets: CD14(++)CD16(-), CD14(++)CD16(+), and CD14((+))CD16(+) cells; the latter two are often denoted as 'proinflammatory' CD16(+) monocytes. Despite an association between CD16(+) monocyte counts and higher CV risk in cross-sectional cohorts, the prognostic impact of elevated CD16(+) monocyte counts is poorly understood.

METHODS AND RESULTS

We assessed monocyte heterogeneity using flow cytometry in 119 patients with non-dialysis CKD, who were prospectively followed for a median of 4.9 (inter-quartile range 4.8-5.0) years for the occurrence of CV events. In addition, we assessed expression of chemokine receptors on monocyte subsets. CD14(++)CD16(+) monocyte were independently associated with CV events [hazard ratio (for an increase of 10 cells/μL) 1.26 (confidence interval: 1.04-1.52; P = 0.018)] after adjustment for variables that significantly affected CD14(++)CD16(+) cell counts at baseline. Across the spectrum of CKD, CD14(++)CD16(+) monocytes selectively expressed CCR5.

CONCLUSION

We found that CD14(++)CD16(+) monocytes were independently associated with CV events in non-dialysis CKD patients. Our results support the notion that CD16(+) monocytes rather than CD16(-) monocytes are involved in human atherosclerosis.