A history of uraemic toxicity and of the European Uraemic Toxin Work Group (EUTox)

Indoxyl Sulfate Contributes to Impaired Height Velocity in (Pre)School Children

Introduction

Growth failure is considered the most important clinical outcome parameter in childhood chronic kidney disease (CKD). Central to the pathophysiology of growth failure is the presence of a chronic proinflammatory state, presumed to be partly driven by the accumulation of uremic toxins. In this study, we assessed the association between uremic toxin concentrations and height velocity in a longitudinal multicentric prospective pediatric CKD cohort of (pre)school-aged children and children during pubertal stages.

Methods

In a prospective, multicentric observational study, a selection of uremic toxin levels of children (aged 0-18 years) with CKD stage 1 to 5D was assessed every 3 months (maximum 2 years) along with clinical growth parameters. Linear mixed models with a random slope for age and a random intercept for child were fitted for height (in cm and SD scores [SDS]). A piecewise linear association between age and height was assumed.

Results

Data analysis included data from 560 visits of 81 children (median age 9.4 years; 2/3 male). In (pre)school aged children (aged 2-12 years), a 10% increase in concurrent indoxyl sulfate (IxS, total) concentration resulted in an estimated mean height velocity decrease of 0.002 SDS/yr (P < 0.05), given that CKD stage, growth hormone (GH), bicarbonate concentration, and dietary protein intake were held constant. No significant association with height velocity was found in children during pubertal stages (aged >12 years).

Conclusion

The present study demonstrated that, especially IxS contributes to a lower height velocity in (pre)school children, whereas we could not find a role for uremic toxins with height velocity during pubertal stages.

Longitudinal Plasma Metabolome Patterns and Relation to Kidney Function and Proteinuria in Pediatric CKD

Key Points

Background

Understanding plasma metabolome patterns in relation to changing kidney function in pediatric CKD is important for continued research for identifying novel biomarkers, characterizing biochemical pathophysiology, and developing targeted interventions. There are a limited number of studies of longitudinal metabolomics and virtually none in pediatric CKD.

Methods

The CKD in Children study is a multi-institutional, prospective cohort that enrolled children aged 6 months to 16 years with eGFR 30–90 ml/min per 1.73 m2. Untargeted metabolomics profiling was performed on plasma samples from the baseline, 2-, and 4-year study visits. There were technologic updates in the metabolomic profiling platform used between the baseline and follow-up assays. Statistical approaches were adopted to avoid direct comparison of baseline and follow-up measurements. To identify metabolite associations with eGFR or urine protein-creatinine ratio (UPCR) among all three time points, we applied linear mixed-effects (LME) models. To identify metabolites associated with time, we applied LME models to the 2- and 4-year follow-up data. We applied linear regression analysis to examine associations between change in metabolite level over time (∆level) and change in eGFR (∆eGFR) and UPCR (∆UPCR). We reported significance on the basis of both the false discovery rate (FDR) <0.05 and P < 0.05.

Results

There were 1156 person-visits (N: baseline=626, 2-year=254, 4-year=276) included. There were 622 metabolites with standardized measurements at all three time points. In LME modeling, 406 and 343 metabolites associated with eGFR and UPCR at FDR <0.05, respectively. Among 530 follow-up person-visits, 158 metabolites showed differences over time at FDR <0.05. For participants with complete data at both follow-up visits (n=123), we report 35 metabolites with ∆level–∆eGFR associations significant at FDR <0.05. There were no metabolites with significant ∆level–∆UPCR associations at FDR <0.05. We report 16 metabolites with ∆level–∆UPCR associations at P < 0.05 and associations with UPCR in LME modeling at FDR <0.05.

Conclusions

We characterized longitudinal plasma metabolomic patterns associated with eGFR and UPCR in a large pediatric CKD population. Many of these metabolite signals have been associated with CKD progression, etiology, and proteinuria in previous CKD Biomarkers Consortium studies. There were also novel metabolite associations with eGFR and proteinuria detected.

Investigation of the inhibition of bacteria and endotoxin influx by back filtration through dialyzer membranes

We investigated the usefulness of assays using human neutrophils for radical production as well as endotoxin (ET) measurement and bacterial culture for endotoxin and bacterial influx by back filtration using dialyzers with different membrane pore diameters. Three types of dialyzers made of cellulose triacetate membrane material with different pore size FB-110EG eco, FB-110U eco, and FB-150UHβ eco were used. A circuit to generate back filtration was created. Back filtrate generated by hydraulic head pressure operation was collected. ET and bacteria were examined. Human neutrophils were exposed to back filtrate (experiments using three different membranes) and contaminated solution, and free radical production was measured using LBP-953 (Berthold) to see if there were differences in production. No bacteria were detected and the concentration of endotoxin was below the detection limit in the back filtrate from the three types of membranes and purified water. Free radical production from neutrophils in the contaminated water was highest at 4,405,750 ± 61,244 cpm (counts per minute) (mean ± SD) (P < 0.01 vs FB-150UHβ eco, FB-110U-eco, and FB-110EG eco) followed by that in back filtrate via FB-150UHβ eco, FB-110U-eco, FB-110EG eco. Radical production from neutrophils was thereby higher in the back filtrate of dialyzers with larger pore-size membranes. No bacteria were observed and the concentration of ET was below the detection limit in back filtrate from any of the membranes. However, when the reverse filtrate was exposed to neutrophils, radical production increased along with pore size, suggesting the influx of small pyrogens and other pyrogenic substances.

Treating Multi-Drug-Resistant Bacterial Infections by Functionalized Nano-Bismuth Sulfide through the Synergy of Immunotherapy and Bacteria-Sensitive Phototherapy

Owing to its flexibility and high treatment efficiency, phototherapy is rapidly emerging for treating bacteria-induced diseases, but how to improve the sensitivity of bacteria to reactive oxygen species (ROS) and heat simultaneously to kill bacteria under mild conditions is still a challenge. Herein, we designed a NIR light catalyst (Bi₂S₃-S-nitrosothiol-acetylcholine (BSNA)) by transforming ^•O₂^- into peroxynitrite in situ, which can enhance the bacterial sensibility to ROS and heat and kill bacteria under a mild temperature. The transformed peroxynitrite in situ possessed a stronger ability to penetrate cell membranes and antioxidant capacity. The BSNA nanoparticles (NPs) inhibited the bacterial glucose metabolic process through down-regulated xerC/xerD expression and disrupted the HSP70/HSP90 secondary structure through nitrifying TYR179. Additionally, the synergistic effect of the designed BSNA and clinical antibiotics increased the antibacterial activity. In the case of tetracycline-class antibiotics, BSNA NPs induced phenolic hydroxyl group structure changes and inhibited the interaction between tetracycline and targeted t-RNA recombinant protein. Besides, BSNA stimulated production of more CD8⁺ T cells and reduced common complications in peritonitis, which provided immunotherapy activity. The targeted and anti-infective effect of BSNA suggested that we propose a nanotherapeutic strategy to achieve more efficient synergistic therapy under mild temperatures.

Toward an individualized determination of dialysis adequacy: a narrative review with special emphasis on incremental hemodialysis

INTRODUCTION

The search for the 'perfect' renal replacement therapy has been paralleled by the search for the perfect biomarkers for assessing dialysis adequacy. Three main families of markers have been assessed: small molecules (prototype: urea); middle molecules (prototype β2-microglobulin); comprehensive and nutritional markers (prototype of the simplified assessment, albumin levels; composite indexes as malnutrition-inflammation score). After an era of standardization of dialysis treatment, personalized dialysis schedules are increasingly proposed, challenging the dogma of thrice-weekly hemodialysis.

AREAS COVERED

In this review, we describe the advantages and limitations of the approaches mentioned above, focusing on the open questions regarding personalized schedules and incremental hemodialysis.

EXPERT OPINION

In the era of personalized dialysis, the assessment of dialysis adequacy should be likewise personalized, due to the limits of 'one size fits all' approaches. We have tried to summarize some of the relevant issues regarding the determination of dialysis adequacy, attempting to adapt them to an elderly, highly comorbidity population, which would probably benefit from tailor-made dialysis prescriptions. While no single biomarker allows precisely tailoring the dialysis dose, we suggest using a combination of clinical and biological markers to prescribe dialysis according to comorbidity, life expectancy, residual kidney function, and small and medium-size molecule depuration.