Associations between the duration of dialysis, endotoxemia, monocyte chemoattractant protein-1, and the effects of a short-dwell exchange in patients requiring continuous ambulatory peritoneal dialysis

Establishing a stable platform for the measurement of blood endotoxin levels in the dialysis population

BACKGROUND

Gram-negative lipopolysaccharides are potent inducers of inflammation and have been shown to be present in patients with end-stage kidney disease. There are a variety of different manufacturers and assay types to quantify endotoxin levels; however, there is no standard methodology to demonstrate its presence in plasma.

METHODS

A control group consisting of haemodialysis and non-kidney disease was selected. Five sets of experiments were conducted to try and ascertain the best platform for plasma endotoxin testing. This included: testing of blank tubes; the effects of freezing, thawing and storage on recovery; the effect of different buffers; use of an endpoint assay and comparison of turbidimetric vs. chromogenic kinetic assays.

RESULTS

No endotoxin was detected in the blood collection tubes. Freezing and thawing per se did not affect spike recovery rates. However, the sequencing of sample dilution relative to freezing had a significant effect on endotoxin recovery. Buffers increased spike recovery at all levels of dilution. No endotoxin was demonstrated with either the turbidimetric or chromogenic kinetic assay at two different dilutions in the haemodialysis controls. The endpoint assay at a 1:5 dilution did not achieve a valid standard curve.

CONCLUSIONS

The findings of our study suggest that, when testing plasma samples, either a turbidimetric or chromogenic assay may be used and should be diluted with appropriate buffers to achieve optimal recovery. Studies looking to quantify the presence of plasma endotoxin need to internally validate their assays and specify their validation findings in their results.

Hyaluronan reduces colitis-induced intraperitoneal inflammation during peritoneal dialysis

BACKGROUND

Peritoneal dialysis induces the inflammatory response within the peritoneal cavity, which contributes to the progressive damage of the peritoneum. Due to close contact of the peritoneal cavity and the intestines, there is the possibility that the visceral disorders can affect the intraperitoneal inflammation during peritoneal dialysis.

OBJECTIVES

Study of the effect of acute colitis on the intraperitoneal inflammation in conditions of peritoneal dialysis and evaluation of the protective effect of hyaluronan in that scenario.

METHODS

In rats with the dextran sulphate-induced colitis, 6-h peritoneal dialysis was performed with dianeal 2.5% +/- hyaluronan 10 mg/dL. In the control group, rats without colitis were studied. Peritoneal permeability and dialysate inflammation were studied at the end of the dialysate exchange.

RESULTS

In rats with colitis, intraperitoneal inflammatory reaction was increased as compared with the control group and reflected by the following studied parameters: dialysate cell count (+26%, p < 0.01), number of neutrophils (+75%, p < 0.01), generation of free radicals in the leukocytes (+70%, p < 0.05), dialysate level of elastase (+102%, p < 0.01), tumor necrosis factor α (+48%, p < 0.01) and monocyte chemoattractant protein-1 (+42%, p < 0.01). Drained dialysate volume was lower (-21%, p < 0.01) and peritoneal permeability increased in rats with colitis (+55%, p < 0.01). In animals with the hyaluronan supplemented dialysis fluids, the intensity of the intraperitoneal inflammation was reduced.

CONCLUSIONS

Visceral inflammation during colitis induces the inflammatory reaction within the peritoneal cavity that may accelerate damage to the peritoneum. Supplementation of the dialysis fluid with hyaluronan reduces the intensity of that effect.

Association between Dyslipidemia and Peritoneal Dialysis Technique Survival

BACKGROUND:

A large body of research has investigated the effects of pro-atherogenic lipid profile on cardiovascular diseases (CVD) in peritoneal dialysis (PD) patients. However, there is a general lack of research on the association between atherogenic dyslipidemia and PD technique survival.

AIM:

The study aimed to define the association between dyslipidemia and PD technique survival.

METHODS:

It was a prospective single-centre observational study involving 40 outpatients on continuous ambulatory PD treatment for more than 3 months between 2010 and 2016 in a single centre in Ukraine. There were 27 males and 13 females. The mean age of the participants was 49.3 ± 12.2 years. The primary outcome measures were all-cause technique failure.

RESULTS:

Atherogenic dyslipidemia was identified in 28/40 (70 %) patients and correlated with PD adequacy parameters. During the 36-month- follow-up period technique failure occurred in 2/12 (16.6 %) patients with atherogenic dyslipidemia compared with 12 / 28 (42.9 %) patients without atherogenic dyslipidemia (χ² = 2.5; p = 0.12). In the univariate Cox regression model, atherogenic dyslipidemia at baseline was significantly associated with a higher risk of all-cause PD technique failure (HR 4.5; 95% CI 1.6 to 12.9; χ² = 5.5, p = 0.019).

CONCLUSION:

The presence of atherogenic dyslipidemia was significantly associated with a higher risk of technique failure in PD patients. This is an important issue for future research. Further well-designed clinical trials are needed to determine the impact of dyslipidemia on PD adequacy and technique survival.

Systemic Endotoxin in Peritoneal Dialysis Patients

Previous reports linked systemic endotoxemia in dialysis patients to increased markers of inflammation, cardiovascular disease, and mortality. Many peritoneal dialysis (PD) patients use acidic, hypertonic dialysates, which could potentially increase gut permeability, resulting in systemic endotoxemia. However, the results from studies measuring endotoxin in PD patients are discordant. We therefore measured systemic endotoxin in 55 PD outpatients attending for routine assessment of peritoneal membrane function; mean age 58.7 ± 16.4 years, 32 (58.2%) male, 21 (38.2%) diabetic, median duration of PD treatment 19.5 (13 - 31) months, 32 (58.2%) using 22.7 g/L dextrose dialysates, and 47 (85.5%) icodextrin. The median systemic endotoxin concentration was 0.0485 (0.0043 - 0.103) Eu/mL. We found no association between endotoxin levels and patient demographics, markers of inflammation, serum albumin, N-terminal pro-brain natriuretic peptide, extracellular volume measured by bioimpedance, blood pressure, PD prescriptions or peritoneal membrane transporter status, or medications. The measurement of endotoxin can be lowered by failure to effectively release protein-bound endotoxin prior to analysis and increased by contamination when taking blood samples and processing and storing the samples. Additionally, contamination with β-glucan from fungal cell walls and the use of different assays to analyze endotoxin can also give differing results. These factors may help to explain the disparate results reported in different studies. Our study would suggest that exposure to standard peritoneal dialysates does not substantially increase systemic endotoxin. However, until endotoxin assays can measure free and bound endotoxin separately, the role of endotoxin causing inflammation in PD patients remains to be determined.

Is peritoneal dialysis causing a measurable burden of inflammatory and endothelial injury on top of metabolic syndrome?

PURPOSE

Low-grade chronic inflammation is present in patients on peritoneal dialysis (PD) and in metabolic syndrome (MS). Due to possible greater endothelial changes in dialyzed patients, inflammatory response and oxidative stress are probably stronger in patients on PD. The objective of the study was to investigate possible in between adipokines, inflammatory, endothelial and oxidative stress markers between MS patients and patients on PD.

METHODS

Concentrations of adipokines (leptin, resistin), inflammatory markers [interleukin-6 (IL-6), soluble tumor necrosis factor alpha receptor (sTNF-R), myeloperoxidase (MPO), monocyte chemoattractant protein 1 (MCP-1)] and endothelial markers [soluble intracellular adhesion molecule-1 (sICAM-1), soluble CD40 ligand (sCD40L)] were determined in 55 MS patients and 18 patients on PD, with flow cytometry, and visfatin concentration was measured with ELISA. Routine biochemistry parameters were measured on Beckman Coulter AU2700 analyzer.

RESULTS

Patients on PD have significantly higher concentration of: CRP [6.5 (3.7-12.1) versus 2.6 (1.3-4.0) mg/L, P < 0.001], IL-6 [13.83 (8.48-31.31) versus 2.05 (0.67-4.11) pg/mL, P < 0.001], MCP-1 [2172.28 (1563.84-2922.77) versus 1353.58 (1166.33-1961.70) pg/mL, P = 0.023], sTNF-R [18.25 (12.81-25.22) versus 1.23 (0.89-1.43) ng/mL, P < 0.001] and sICAM-1 [830.03 (599.21-967.02) versus 463.85 (315.25-751.71) ng/mL, P = 0.006] than subjects with MS. MS patients have higher concentrations of MPO [175.47 (120.15-231.67) versus 101.76 (53.55-186.06) ng/mL, P = 0.016] and visfatin [1.5 (0.9-2.3) versus 0.9 (0.6-1.6) ng/mL, P = 0.013].

CONCLUSION

In patients on PD, inflammatory reaction is higher than in patients with MS. On the contrary, patients with MS have stronger oxidative stress response and adipose tissue activity caused probably by the chronic low level of inflammation and underlying metabolic disorders.