Independent effects of systemic and peritoneal inflammation on peritoneal dialysis survival

Interleukin-6 trans-signalling induces vascular endothelial growth factor synthesis partly via Janus kinases-STAT3 pathway in human mesothelial cells

AIMS

Interleukin-6 (IL-6) is a vital inflammatory factor in the peritoneal cavity of peritoneal dialysis (PD) patients. Because intraperitoneal inflammation is closely associated with angiogenesis, we sought to explore the effect of IL-6 on vascular endothelial growth factor (VEGF) synthesis and its transduction pathway in mesothelial cells.

METHODS

Human mesothelial cells (Met-5A) were incubated with different concentrations of glucose and mannitol, and the effect of glucose and mannitol on the expression of IL-6 was determined. Then, the cells were stimulated by IL-6 with or without two soluble receptors of IL-6 (sIL-6R or sgp130), and VEGF synthesis was detected. Finally, the cells were incubated with IL-6/sIL-6R combined with or without the inhibitor of Janus kinases (JAK) AG490. The phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and its intracellular translocation were examined.

RESULTS

1. High glucose and mannitol could upregulate IL-6 mRNA expression and IL-6 secretion in mesothelial cells significantly, and there was no difference of its effect between high glucose and mannitol. 2. Met-5A was a cell line with a single IL-6 receptor. The IL-6/sIL-6R complex induced VEGF synthesis of mesothelial cells, which was alleviated by sgp130 or AG490. IL-6 trans-signalling could induce the phosphorylation of STAT3, which is recruited to the cellular nucleus of Met-5A cells.

CONCLUSION

The present study might provide evidence that high glucose upregulates IL-6 synthesis in Met-5A cells, to some extent, depending on its osmolality and that IL-6 trans-signalling could induce VEGF synthesis partly dependent on the JAK/STAT3 pathway.

The NLRP3 Inflammasome Has a Critical Role in Peritoneal Dialysis-Related Peritonitis

Bacterial peritonitis remains the main cause of technique failure in peritoneal dialysis (PD). During peritonitis, the peritoneal membrane undergoes structural and functional alterations that are mediated by IL-1β The NLRP3 inflammasome is a caspase-1-activating multiprotein complex that links sensing of microbial and stress products to activation of proinflammatory cytokines, including IL-1β The potential roles of the NLRP3 inflammasome and IL-1β in the peritoneal membrane during acute peritonitis have not been investigated. Here, we show that the NLRP3 inflammasome is activated during acute bacterial peritonitis in patients on PD, and this activation associates with the release of IL-1β in the dialysate. In mice, lipopolysaccharide- or Escherichia coli-induced peritonitis led to IL-1β release in the peritoneal membrane. The genetic deletion of Nalp3, which encodes NLRP3, abrogated defects in solute transport during acute peritonitis and restored ultrafiltration. In human umbilical vein endothelial cells, IL-1β treatment directly enhanced endothelial cell proliferation and increased microvascular permeability. These in vitro effects require endothelial IL-1 receptors, shown by immunofluorescence to be expressed in peritoneal capillaries in mice. Furthermore, administration of the IL-1β receptor antagonist, anakinra, efficiently decreased nitric oxide production and vascular proliferation and restored peritoneal function in mouse models of peritonitis, even in mice treated with standard-of-care antibiotherapy. These data demonstrate that NLRP3 activation and IL-1β release have a critical role in solute transport defects and tissue remodeling during PD-related peritonitis. Blockade of the NLRP3/IL-1β axis offers a novel method for rescuing morphologic alterations and transport defects during acute peritonitis.

The 24-Month Changes in Body Fat Mass and Adipokines in Patients Starting Peritoneal Dialysis

♦ BACKGROUND: Peritoneal dialysis (PD) is characterized by a gain in fat mass. The fat tissue is a complex endocrine organ that releases various adipokines. In this study, we prospectively examined serial changes of fat composition and adipokines in patients undergoing PD. ♦ METHODS: Body composition was assessed by computed tomography (CT). Nutrition status and adipokines (leptin, adiponectin, interleukin [IL]-6, and tumor necrosis factor [TNF]-α) were assessed on the 7th day and 6 months, 12 months, and 24 months after the start of PD. ♦ RESULTS: Fifty-four patients (28 men), with a mean age of 53.2 ± 13.2 years, were enrolled. Baseline fat mass, especially subcutaneous fat mass, was correlated with baseline leptin (ρ = 0.612), adiponetin (ρ = -0.477), and interleukin-6 (IL-6) (ρ = 0.391). Visceral fat mass was correlated with leptin (ρ = 0.545) and adiponectin (ρ = -0.514). Baseline adiponectin was negatively correlated with baseline leptin (ρ = -0.363). While body weight and leptin increased during the 24 months, serum adiponectin decreased in that period. The changes in visceral and subcutaneous fat mass were greater in the first 12 months and 6 months, respectively. There was no difference in IL-6 and TNF-α. Eight patients died during the follow-up period (mean 47.4 months). Twenty-seven patients continued PD. Increased baseline and serial change of IL-6 level were risk factors for mortality. After adjusting for age, sex, diabetes mellitus (DM), and coronary vascular disease (CVD), the significance of the IL-6 level disappeared. ♦ CONCLUSIONS: Baseline subcutaneous fat in patients starting PD is correlated with baseline adipokine levels rather than visceral fat. The increase in subcutaneous fat was greatest in the first 6 months. While leptin and adiponectin increased and decreased respectively, IL-6 did not change in the first 24 months.

Is there such a thing as biocompatible peritoneal dialysis fluid?

Introduction of the so-called biocompatible peritoneal dialysis (PD) fluids was based on a large body of experimental evidence and various clinical trials suggesting important clinical benefits. Of these, until now, only preservation of residual renal function-likely due to lower glucose degradation product load and, in case of icodextrin, improved fluid and blood pressure control-have consistently been proven, whereas the impact on important clinical endpoints such as infectious complications, preservation of PD membrane transport function, and patient outcome, are still debated. In view of the high morbidity and mortality rates of PD patients, novel approaches are warranted and comprise the search for alternative osmotic agents and enrichment of PD fluids with specific pharmacologic agents, such as alanyl-glutamine, potentially counteracting local but also systemic sequelae of uremia and PD.

Platelet index levels and cardiovascular mortality in incident peritoneal dialysis patients: a cohort study

Prior studies have shown that the levels of some platelet (PLT) indices were associated with mortality in patients undergoing hemodialysis. We aimed to investigate whether the changes in PLT indices associated with mortality in patients on peritoneal dialysis (PD). A single-center, retrospective observational cohort study was conducted in incident PD patients from 1 January 2006 to 31 December 2012, and followed up until 31 December 2014. Cox proportional hazard models were used to examine the relationships between the levels of PLT indices including PLT, plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), platelet large cell ratio (PLCR), and mortality. Of 1324 patients, 276 (20.8%) died during follow-up (median, 37; IQR, 3-107.4 months), among which 134 were due to cardiovascular diseases (CVD). The highest tertile of PLT levels at baseline was associated with increased risk for cardiovascular mortality after adjustment for demographic, clinical characteristics, and laboratory variables (hazard ratio [HR]:1.93; 95% confidence interval [CI]: 1.16-3.20). The similar treads were also observed in the middle and the highest tertile of the PCT level (HR: 1.68, 95%CI: 1.00-2.81 and HR: 1.89, 95%CI: 1.14-3.14, respectively). In addition, the highest tertile of PCT was associated with increased all-cause mortality (HR: 1.41, 95%CI: 1.01-1.96). However, none of the associations in MPV, PDW, and PLCR analyses reached statistical significance (HR: 0.71, 95%CI: 0.43-1.16; HR: 0.72, 95%CI: 0.45-1.18 and HR: 0.74, 95%CI: 0.46-1.19, respectively). These results suggest that higher PLT and PCT may be associated with higher risk for cardiovascular mortality in incident PD patients. Additional studies are needed to investigate whether correction of these two PLT indices reduces the risk.

IL-6 Trans-Signaling Links Inflammation with Angiogenesis in the Peritoneal Membrane

Vascular endothelial growth factor (VEGF) is implicated in the peritoneal membrane remodeling that limits ultrafiltration in patients on peritoneal dialysis (PD). Although the exact mechanism of VEGF induction in PD is unclear, VEGF concentrations in drained dialysate correlate with IL-6 levels, suggesting a link between these cytokines. Human peritoneal mesothelial cells (HPMCs), the main source of IL-6 and VEGF in the peritoneum, do not bear the cognate IL-6 receptor and are thus unable to respond to classic IL-6 receptor signaling. Here, we investigated whether VEGF release by HPMCs is controlled by IL-6 in combination with its soluble receptor (IL-6 trans-signaling). Although treatment with either IL-6 or soluble IL-6 receptor (sIL-6R) alone had no effect on VEGF production, stimulation of HPMCs with IL-6 in combination with sIL-6R promoted VEGF expression and secretion through a transcriptional mechanism involving STAT3 and SP4. Conditioned medium from HPMCs cultured with IL-6 and sIL-6R promoted angiogenic endothelial tube formation, which could be blocked by silencing SP4. In vivo, induction of peritoneal inflammation in wild-type and IL-6-deficient mice showed IL-6 involvement in the control of Sp4 and Vegf expression and new vessel formation, confirming the role of IL-6 trans-signaling in these processes. Taken together, these findings identify a novel mechanism linking IL-6 trans-signaling and angiogenesis in the peritoneal membrane.

The Current State of Peritoneal Dialysis

Technical innovations in peritoneal dialysis (PD), now used widely for the long-term treatment of ESRD, have significantly reduced therapy-related complications, allowing patients to be maintained on PD for longer periods. Indeed, the survival rate for patients treated with PD is now equivalent to that with in-center hemodialysis. In parallel, changes in public policy have spurred an unprecedented expansion in the use of PD in many parts of the world. Meanwhile, our improved understanding of the molecular mechanisms involved in solute and water transport across the peritoneum and of the pathobiology of structural and functional changes in the peritoneum with long-term PD has provided new targets for improving efficiency and for intervention. As with hemodialysis, almost half of all deaths on PD occur because of cardiovascular events, and there is great interest in identifying modality-specific factors contributing to these events. Notably, tremendous progress has been made in developing interventions that substantially reduce the risk of PD-related peritonitis. Yet the gains have been unequal among individual centers, primarily because of unequal clinical application of knowledge gained from research. The work to date has further highlighted the areas in need of innovation as we continue to strive to improve the health and outcomes of patients treated with PD.

Unconventional Human T Cells Accumulate at the Site of Infection in Response to Microbial Ligands and Induce Local Tissue Remodeling

The antimicrobial responsiveness and function of unconventional human T cells are poorly understood, with only limited access to relevant specimens from sites of infection. Peritonitis is a common and serious complication in individuals with end-stage kidney disease receiving peritoneal dialysis. By analyzing local and systemic immune responses in peritoneal dialysis patients presenting with acute bacterial peritonitis and monitoring individuals before and during defined infectious episodes, our data show that Vγ9/Vδ2⁺ γδ T cells and mucosal-associated invariant T cells accumulate at the site of infection with organisms producing (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate and vitamin B₂, respectively. Such unconventional human T cells are major producers of IFN-γ and TNF-α in response to these ligands that are shared by many microbial pathogens and affect the cells lining the peritoneal cavity by triggering local inflammation and inducing tissue remodeling with consequences for peritoneal membrane integrity. Our data uncover a crucial role for Vγ9/Vδ2 T cells and mucosal-associated invariant T cells in bacterial infection and suggest that they represent a useful predictive marker for important clinical outcomes, which may inform future stratification and patient management. These findings are likely to be applicable to other acute infections where local activation of unconventional T cells contributes to the antimicrobial inflammatory response.

Toll-Like Receptors 2 and 4 Are Potential Therapeutic Targets in Peritoneal Dialysis-Associated Fibrosis

Peritoneal dialysis (PD) remains limited by dialysis failure due to peritoneal membrane fibrosis driven by inflammation caused by infections or sterile cellular stress. Given the fundamental role of Toll-like receptors (TLRs) and complement in inflammation, we assessed the potential of peritoneal TLR2, TLR4 and C5a receptors, C5aR and C5L2, as therapeutic targets in PD-associated fibrosis. We detected TLR2-, TLR4-, and C5aR-mediated proinflammatory and fibrotic responses to bacteria that were consistent with the expression of these receptors in peritoneal macrophages (TLR2/4, C5aR) and mesothelial cells (TLR2, C5aR). Experiments in knockout mice revealed a major role for TLR2, a lesser role for TLR4, a supplementary role for C5aR, and no apparent activity of C5L2 in infection-induced peritoneal fibrosis. Similarly, antibody blockade of TLR2, TLR4, or C5aR differentially inhibited bacteria-induced profibrotic and inflammatory mediator production by peritoneal leukocytes isolated from the peritoneal dialysis effluent (PDE) of noninfected uremic patients. Additionally, antibodies against TLR2, TLR4, or the coreceptor CD14 reduced the profibrotic responses of uremic leukocytes to endogenous components present in the PDE of noninfected patients. Enhancing TLR2-mediated inflammation increased fibrosis in vivo Furthermore, soluble TLR2 (sTLR2), a negative modulator of TLRs that we detected in PDE, inhibited PDE-induced, TLR2- or TLR4-mediated profibrotic responses. Notably, sTLR2 treatment markedly reduced Gram-positive and -negative bacteria-induced fibrosis in vivo, inhibiting proinflammatory and fibrotic genes without affecting infection clearance. These findings reveal the influence of peritoneal TLR2 and TLR4 on PD-associated fibrosis and describe a therapeutic strategy against fibrosis.

Preliminary observations on the association between serum IL-6 and hydration status and cardiovascular risk in patients treated with peritoneal dialysis

INTRODUCTION

Systemic inflammation, as defined by elevated blood IL-6, is a strong independent predictor of peritoneal dialysis (PD) patient survival. The present study has aimed to determine whether there exists a particular "phenotype" associated with high systemic IL-6 that characterizes PD patients in terms of their fluid status and cardiac parameters.

METHODS

Fifty-seven prevalent PD patients were classified according to serum concentrations of IL-6. The degree of overhydration was assessed by bioimpedance analysis (BIA). Echocardiography and serum concentrations of NT-proBNP and troponin T were used to assess cardiovascular risk.

RESULTS

Patients with high serum IL-6 were older, more often diabetic, treated with PD for longer, and significantly more overhydrated. There was a significant correlation between serum IL-6, hydration status (r=0.38; p=0.002) and serum albumin (r=-0.35; p=0.009). Multivariate regression analysis confirmed a strong association of overhydration, hypoalbuminemia, and systemic IL-6 concentration. Patients with high IL-6 had significantly increased levels of both NT-proBNP (r=0.36; p=0.006) and TnT (r=0.50; p<0.001) in the absence of abnormalities in echocardiography.

CONCLUSIONS

High systemic IL-6 identifies PD patients with increased cardiovascular risk that is significantly related to overhydration. Thus, the measurement of serum IL-6 may contribute to the more accurate assessment of cardiovascular status in patients undergoing PD.

Peritoneal Dialysate Glucose Load and Systemic Glucose Metabolism in Non-Diabetics: Results from the GLOBAL Fluid Cohort Study

Background and Objectives

Glucose control is a significant predictor of mortality in diabetic peritoneal dialysis (PD) patients. During PD, the local toxic effects of intra-peritoneal glucose are well recognized, but despite large amounts of glucose being absorbed, the systemic effects of this in non-diabetic patients are not clear. We sought to clarify whether dialysate glucose has an effect upon systemic glucose metabolism.

Methods and Materials

We analysed the Global Fluid Study cohort, a prospective, observational cohort study initiated in 2002. A subset of 10 centres from 3 countries with high data quality were selected (368 incident and 272 prevalent non-diabetic patients), with multilevel, multivariable analysis of the reciprocal of random glucose levels, and a stratified-by-centre Cox survival analysis.

Results

The median follow up was 5.6 and 6.4 years respectively in incident and prevalent patients. On multivariate analysis, serum glucose increased with age (β = -0.007, 95%CI -0.010, -0.004) and decreased with higher serum sodium (β = 0.002, 95%CI 0.0005, 0.003) in incident patients and increased with dialysate glucose (β = -0.0002, 95%CI -0.0004, -0.00006) in prevalent patients. Levels suggested undiagnosed diabetes in 5.4% of prevalent patients. Glucose levels predicted death in unadjusted analyses of both incident and prevalent groups but in an adjusted survival analysis they did not (for random glucose 6–10 compared with <6, Incident group HR 0.92, 95%CI 0.58, 1.46, Prevalent group HR 1.42, 95%CI 0.86, 2.34).

Conclusions

In prevalent non-diabetic patients, random glucose levels at a diabetic level are under-recognised and increase with dialysate glucose load. Random glucose levels predict mortality in unadjusted analyses, but this association has not been proven in adjusted analyses.

Effects of Icodextrin and Glucose Bicarbonate/Lactate-Buffered Peritoneal Dialysis Fluids on Effluent Cell Population and Biocompatibility Markers IL-6 and CA125 in Incident Peritoneal Dialysis Patients

Icodextrin peritoneal dialysis (PD) solution has been shown to increase interleukin-6 (IL-6) levels in PD effluent as well as leukocyte and mesothelial cell count. Mesothelial cells release cancer antigen 125 (CA125), which is used as a marker of mesothelial cell mass. This 1-year prospective study was designed to compare peritoneal effluent cell population, its inflammatory phenotype and biocompatibility biomarkers IL-6 and CA125 between icodextrin (E) and glucose bicarbonate/lactate (P) based PD solutions. Using baseline peritoneal ultrafiltration capacity, 19 stable incident PD patients were allocated either to P only (N = 8) or to P plus E for the overnight dwell (N = 11). Flow cytometry was used to measure white blood cell count and differential and the expression of inflammatory molecules on peritoneal cells isolated from timed overnight peritoneal effluents. Compared to P, E effluent showed higher leukocyte (10.9 vs. 7.9), macrophages (6.1 vs. 2.5) and mesothelial cells (0.3 vs. 0.1)×10(6) /L count, as well as expression of HLA DR on mesothelial cells and IL-6 (320.5 vs. 141.2 pg/min) on mesothelial cells and CA125 appearance rate (159.6 vs. 84.3 IU/min), all P < 0.05. In the E group, correlation between IL-6 and CA125 effluent levels (r = 0.503, P < 0.05) as well as appearance rates (r = 0.774, P < 0.001) was demonstrated. No effect on systemic inflammatory markers or peritoneal permeability was found. Icodextrin PD solution activates local inflammation without systemic consequences so the clinical relevance of this observation remains obscure. Correlation between effluent IL-6 and CA125 suggests that CA125 might be upregulated due to inflammation and thus is not a reliable marker of mesothelial cell mass and/or biocompatibility.

Peritoneal inflammation precedes encapsulating peritoneal sclerosis: results from the GLOBAL Fluid Study

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is an uncommon condition, strongly associated with a long duration of peritoneal dialysis (PD), which is itself associated with increased fibrosis in the peritoneal membrane. The peritoneal membrane is inflamed during PD and inflammation is often associated with fibrosis. We hypothesized that patients who subsequently develop EPS might have a more inflamed peritoneal membrane during PD.

METHODS

We performed a nested, case-control study identifying all EPS cases in the UK arm of the GLOBAL Fluid Study and matching them by centre and duration of PD with two to three controls. Dialysate and plasma samples were taken during repeated peritoneal equilibration tests prior to cessation of PD from cases and controls. Samples were assayed by electrochemiluminescence immunoassay for interleukin-1β (IL-1β), tumour necrosis factor α (TNF-α), interferon-γ (IFN-γ) and IL-6. Results were analysed by linear mixed models adjusted for age and time on PD.

RESULTS

Eleven EPS cases were matched with 26 controls. Dialysate TNF-α {0.64 [95% confidence interval (CI) 0.23, 1.05]} and IL-6 [0.79 (95% CI 0.03, 1.56)] were significantly higher in EPS cases, while IL-1β [1.06 (95% CI -0.11, 2.23)] and IFN-γ [0.62 (95% CI -0.06, 1.29)] showed a similar trend. Only IL-6 was significantly higher in the plasma [0.42 (95% CI 0.07, 0.78)]. Solute transport was not significantly different between cases and controls but did increase in both groups with the duration of PD.

CONCLUSIONS

The peritoneal cavity has higher levels of inflammatory cytokines during PD in patients who subsequently develop EPS, but neither inflammatory cytokines nor peritoneal solute transport clearly discriminates EPS cases. Increased systemic inflammation is also evident and is probably driven by increased peritoneal inflammation.

Pro-inflammatory cytokines: a possible relationship with dialytic adequacy and serum albumin in peritoneal dialysis patients

Background

Inflammation and serum albumin concentration are both important predictors of survival in patients treated with peritoneal dialysis (PD). Furthermore, systemic and local inflammatory mediators may induce structural and functional alterations in the peritoneal membrane, thus interfering with dialysis adequacy. PD adequacy is monitored primarily by indices of small solute clearance, such as Kt/V urea and weekly creatinine clearance (wCc). The aim of this study was to investigate the possible relationship between pro-inflammatory cytokines, such as interleukin-6 (IL-6) and interleukin-1β (IL-1β), and serum albumin and C-reactive protein (CRP). Moreover, the relationship between IL-6 and IL-1β and PD adequacy has been analysed.

Methods

We enrolled 46 stable PD patients undergoing maintenance PD for a minimum of 3 months. Plasma levels of serum albumin, high-sensitivity (hs)-CRP, IL-6 and IL-1β were measured in all patients. We used weekly Kt/V urea and wCc to monitor PD adequacy. Daily urine volume was measured in all patients.

Results

The median values of serum albumin, hs-CRP, IL-6 and IL-1β showed no significant differences between continuous ambulatory PD and automated PD patients. IL-6 levels showed a positive correlation with hs-CRP levels (P < 0.001) and a negative correlation with serum albumin concentration (P = 0.01). There was no statistically significant relationship between IL-1β and hs-CRP or serum albumin concentrations. Subsequently, PD patients were divided into two groups based on Kt/V urea value. PD patients with Kt/V ≤1.7 had significantly higher IL-6 levels compared with PD patients with Kt/V >1.7 (P = 0.015). No statistically significant relationship between IL-6 and wCc was observed. There was no significant difference in IL-1β levels between PD patients with Kt/V ≤1.7 and with Kt/V >1.7 [median (interquartile range) 0.82 (0.88–5.2) versus 1.82 (0.95–2.7)]. There was no significant difference in IL-6 and IL-1β levels in PD patients with and without residual diuresis (P = 0.32 and P = 0.77, respectively).

Conclusion

Our data suggest a possible relationship between serum IL-6 levels and serum albumin and hs-CRP in PD patients. Furthermore, IL-6 seems to be higher in patients with lower Kt/V, thus suggesting a possible use of this inflammatory biomarker in PD adequacy monitoring.

Cytokine profiles in peritoneal dialysis effluent predicts the peritoneal solute transport rate in continuous ambulatory peritoneal dialysis patients

Cytokine profiles in peritoneal dialysis effluent (PDE) vary among patients of continuous ambulatory peritoneal dialysis (CAPD), which may indicate the therapeutic efficiency of CAPD. We examined the cytokine profiles of PDE with stable CAPD and analyzed their relation with the peritoneal solute transport rate (PSTR). The peritoneal equilibration test (PET) was performed to evaluate peritoneal solute transport rate (PSTR) by calculating dialysate/plasma creatinine (D/P Cr). Patients were then divided into either low and low-average transport (L/A), or high and high average transport (H/A) groups according PET results. Overnight PDE were collected from 30 CAPD patients and various cytokines and growth factors were detected using the Luminex Flex Map 3D system. The concentrations of interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1 and tumor necrosis factor (TNF)-α in dialysate were 66.4±59.8, 221±96.1 and 1.79±0.34 pg/mL respectively while IL-17A, IL-17F, IL-21, IL-22 or IL-23 could not be detected. Higher IL-6 levels were found in the H/A group as compared with the L/A group (P<0.05); however MCP-1, TNF-α, transforming growth factor (TGF)-β1 and VEGF levels were not significantly different between these two groups (P>0.05). We found that IL-6, MCP-1, vascular endothelial growth factor (VEGF) and TGF-β1 levels were closely correlated with each other and all significantly associated with D/P Cr. Multivariate analysis showed that D/P Cr was independently correlated with IL-6 and negatively correlated with serum albumin (r=-0.369, P=0.045). In conclusion, our study indicates that systemic analysis of cytokine profiles in PDE reveals the transport characteristics of CAPD patients. Long-term follow-up study should be necessary to further confirm the value of cytokine detection in evaluation of PD therapeutic efficiency.

Baseline higher peritoneal transport had been associated with worse nutritional status of incident continuous ambulatory peritoneal dialysis patients in Southern China: a 1-year prospective study

The aim of the present study was to investigate the relationship between baseline peritoneal transport types and nutritional status in Chinese continuous ambulatory peritoneal dialysis (CAPD) patients. In the present single-centre, prospective study, incident CAPD patients were included from 15 April 2010 to 31 December 2011 and were followed up for 12 months. According to the results of baseline peritoneal equilibration test, patients were divided into lower peritoneal transport group (lower transporters) and higher peritoneal transport group (higher transporters). Nutritional status was evaluated by both subjective global assessment (SGA) and protein-energy wasting (PEW) score. The body composition parameters were assessed by body impedance analysis. A total of 283 CAPD patients were included in the study, of which 171 (60.4 %) were males with a mean age of 47.0 (sd 14.9) years. Compared with lower transporters (n 92), higher transporters (n 181) had lower levels of serum albumin (37.1 (sd 4.3) v. 39.6 (sd 4.3) g/l, P< 0.001), serum pre-albumin (356 (sd 99) v. 384 (sd 90) mg/l, P= 0.035), phase angle (6.15 (sd 0.39) v. 6.27 (sd 0.47)°, P< 0.05) and higher rate of malnutrition defined by SGA (52.5 v. 25.0%, P< 0.001) and PEW score (37.0 v. 14.1 %, P< 0.001) at 1-year of follow-up. Baseline higher peritoneal transport, analysed by multivariate binary logistic regressions, was independently associated with malnutrition (SGA mild to moderate and severe malnutrition: OR 3.43, 95% CI 1.69, 6.96, P< 0.01; PEW: OR 2.40, 95% CI 1.08, 5.31, P= 0.03). It was concluded that baseline higher peritoneal transport was independently associated with worse nutritional status of CAPD patients in Southern China.

NRF2 and NF-κB mRNA expression in chronic kidney disease: a focus on nondialysis patients

PURPOSE

To evaluate nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappaB (NF-κB) mRNA expression in nondialysis chronic kidney disease (CKD) patients, comparing with data from hemodialysis (HD) patients and healthy individuals.

METHODS

Twenty nondialysis CKD patients (62.0 ± 8.1 years old, 11 men, estimated glomerular filtration rate of 36.8 ± 13.6 mL/min/1.73 m(2)), twenty HD patients (55.0 ± 15.2 years old, 13 men, and dialysis vintage of 76.5 ± 46.3 months) and eleven healthy individuals (50.9 ± 8.0 years old, 6 men) were enrolled in the study. The peripheral blood mononuclear cells were isolated and processed for the evaluation of expression of NF-κB and Nrf2 by quantitative real-time polymerase chain reaction.

RESULTS

Nrf2 mRNA expression was significantly higher in nondialysis (1.12 ± 0.57) when compared to HD patients (0.58 ± 0.35, p = 0,006) but similar to healthy individuals (1.13 ± 0.64). Inversely, NF-κB mRNA expression was lower in nondialysis (1.21 ± 0.71) when compared to HD patients (2.08 ± 0.7, p < 0.0001) and similar to healthy individuals (1.04 ± 0.22). Nrf2 mRNA was positively correlated with NF-κB mRNA expression in nondialysis CKD patients (r = 0.52, p = 0.02) and healthy individuals (r = 0.77, p < 0.006). By contrast, Nrf2 mRNA was inversely correlated with NF-κB mRNA expression (r = -0.65, p = 0.003) in HD patients.

CONCLUSION

Nondialysis CKD patients may conserve regular homeostatic balance between Nrf2 and NF-κB expressions, being comparable to healthy individuals. However, HD patients seem to have Nrf2 downregulation and NF-κB upregulation. Thus, the association among Nrf2 and NF-κB expressions and nutritional status, kidney disease progression or immune deregulation deserve further investigation.

Peritoneal Equilibration Test and Patient Outcomes

BACKGROUND AND OBJECTIVES

Although a peritoneal equilibration test yields data on three parameters (4-hour dialysate/plasma creatinine, 4- to 0-hour dialysate glucose, and 4-hour ultrafiltration volume), all studies have focused on the prognostic value of dialysate/plasma creatinine for patients undergoing peritoneal dialysis. Because dialysate 4- to 0-hour glucose and ultrafiltration volume may be superior in predicting daily ultrafiltration, the likely mechanism for the association of peritoneal equilibration test results with outcomes, we hypothesized that they are superior to dialysate/plasma creatinine for risk prediction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined unadjusted and adjusted associations of three peritoneal equilibration test parameters with all-cause mortality, technique failure, and hospitalization rate in 10,142 patients on peritoneal dialysis treated between January 1, 2007 and December 31, 2011 in 764 dialysis facilities operated by a single large dialysis organization in the United States, with a median follow-up period of 15.8 months; 87% were treated with automated peritoneal dialysis.

RESULTS

Demographic and clinical parameters explained only 8% of the variability in dialysate/plasma creatinine. There was a linear association between dialysate/plasma creatinine and mortality (adjusted hazards ratio per 0.1 unit higher, 1.07; 95% confidence interval, 1.02 to 1.13) and hospitalization rate (adjusted incidence rate ratio per 0.1 unit higher, 1.05; 95% confidence interval, 1.03 to 1.06). Dialysate/plasma creatinine and dialysate glucose were highly correlated (r=-0.84) and yielded similar risk prediction. Ultrafiltration volume was inversely related with hospitalization rate but not with all-cause mortality. None of the parameters were associated with technique failure. Adding 4- to 0-hour dialysate glucose, ultrafiltration volume, or both did not result in any improvement in risk prediction with dialysate/plasma creatinine alone.

CONCLUSIONS

This analysis from a large contemporary cohort treated primarily with automated peritoneal dialysis validates dialysate/plasma creatinine as a robust predictor of outcomes in patients treated with peritoneal dialysis.

microRNA regulation of peritoneal cavity homeostasis in peritoneal dialysis

Preservation of peritoneal cavity homeostasis and peritoneal membrane function is critical for long-term peritoneal dialysis (PD) treatment. Several microRNAs (miRNAs) have been implicated in the regulation of key molecular pathways driving peritoneal membrane alterations leading to PD failure. miRNAs regulate the expression of the majority of protein coding genes in the human genome, thereby affecting most biochemical pathways implicated in cellular homeostasis. In this review, we report published findings on miRNAs and PD therapy, with emphasis on evidence for changes in peritoneal miRNA expression during long-term PD treatment. Recent work indicates that PD effluent- (PDE-) derived cells change their miRNA expression throughout the course of PD therapy, contributing to the loss of peritoneal cavity homeostasis and peritoneal membrane function. Changes in miRNA expression profiles will alter regulation of key molecular pathways, with the potential to cause profound effects on peritoneal cavity homeostasis during PD treatment. However, research to date has mainly adopted a literature-based miRNA-candidate methodology drawing conclusions from modest numbers of patient-derived samples. Therefore, the study of miRNA expression during PD therapy remains a promising field of research to understand the mechanisms involved in basic peritoneal cell homeostasis and PD failure.

Peritoneal Dialysis in Western Countries

BACKGROUND

Peritoneal dialysis (PD) for the treatment of end-stage renal failure was introduced in the 1960s. Nowadays it has evolved to an established therapy that is complementary to hemodialysis (HD), representing 11% of all patients treated worldwide with dialysis. Despite good clinical outcomes and similar results in patient survival between PD and HD, the penetration of PD is decreasing in the Western world.

SUMMARY

First the major events in the history of the development of PD are described. Then important insights into the physiology of peritoneal transport are discussed and linked to the changes in time observed in biopsies of the peritoneal membrane. Furthermore, the developments in peritoneal access, more biocompatible dialysate solutions, automated PD at home, the establishment of parameters for dialysis adequacy and strategies to prevent infectious complications are mentioned. Finally non-medical issues responsible for the declining penetration in the Western world are analyzed.

KEY MESSAGES

Only after introduction of the concept of continuous ambulatory PD by Moncrief and Popovich has this treatment evolved in time to a renal replacement therapy. Of all structures present in the peritoneal membrane, the capillary endothelium offers the rate-limiting hindrance for solute and water transport for the diffusive and convective transport of solutes and osmosis. The functional and anatomical changes in the peritoneal membrane in time can be monitored by the peritoneal equilibrium test. Peritonitis incidence decreased by introduction of the Y-set and prophylaxis using mupirocin on the exit site. The decrease in the proportion of patients treated with PD in the Western world can be explained by non-medical issues such as inadequate predialysis patient education, physician experience and training, ease of HD initiation, overcapacity of in-center HD, lack of adequate infrastructure for PD treatment, costs and reimbursement issues of the treatment.

FACTS FROM EAST AND WEST

(1) PD is cheaper than HD and provides a better quality of life worldwide, but its prevalence is significantly lower than that of HD in all countries, with the exception of Hong Kong. Allowing reimbursement of PD but not HD has permitted to increase the use of PD over HD in many Asian countries like Hong Kong, Vietnam, Taiwan, Thailand, as well as in New Zealand and Australia over the last years. In the Western world, however, HD is still promoted, and the proportion of patients treated with PD decreases. Japan remains an exception in Asia where PD penetration is very low. Lack of adequate education of practitioners and information of patients might as well be reasons for the low penetration of PD in both the East and West. (2) Patient survival of PD varies between and within countries but is globally similar to HD. (3) Peritonitis remains the main cause of morbidity in PD patients. South Asian countries face specific issues such as high tuberculosis and mycobacterial infections, which are rare in developed Asian and Western countries. The infection rate is affected by climatic and socio-economic factors and is higher in hot, humid and rural areas. (4) Nevertheless, the promotion of a PD-first policy might be beneficial particularly for remote populations in emerging countries where the end-stage renal disease rate is increasing dramatically.

Genetic Polymorphisms and Peritoneal Membrane Function

BACKGROUND

Outcomes for peritoneal dialysis (PD) patients are affected by the characteristics of the peritoneal membrane, which may be determined by genetic variants. We carried out a systematic review of the literature to identify studies which assessed the association between genetic polymorphisms, peritoneal membrane solute transport, and clinical outcomes for PD patients.

METHODS

The National Library of Medicine was searched using a variety of strategies. Studies which met our inclusion criteria were reviewed and data abstracted. Our outcomes of interest included: high transport status peritoneal membrane, risk for peritonitis, encapsulating peritoneal sclerosis (EPS), patient and technique survival. We combined data from studies which evaluated the same genetic polymorphism and the same outcome.

RESULTS

We evaluated 18 relevant studies. All studies used a candidate gene approach. Gene polymorphisms in the interleukin (IL)-6 gene were associated with peritoneal membrane solute transport in several studies in different ethnic populations. Associations with solute transport and polymorphisms in endothelial nitric oxide synthase and receptor for advanced glycation end product genes were also identified. There was evidence of a genetic predisposition for peritonitis found in 2 studies, and for EPS in 1 study. Survival was found to be associated with a polymorphism in vascular endothelial growth factor and technique failure was associated with a polymorphism in the IL-1 receptor antagonist.

CONCLUSIONS

There is evidence that characteristics of the peritoneal membrane and clinical outcomes for PD patients have genetic determinants. The most consistent association was between IL-6 gene polymorphisms and peritoneal membrane solute transport.

Increased dialysate MCP-1 is associated with cardiovascular mortality in peritoneal dialysis patients: a prospective observational study

BACKGROUND

The aim of this study was to investigate the association between the dialysate MCP-1 (dMCP-1) and systemic inflammatory and nutritional markers in peritoneal dialysis (PD) patients. In addition, we examined the prognostic value of dMCP-1 on all-cause or cardiovascular mortality in these patients.

METHODS

We prospectively followed 169 prevalent PD patients from April 1st 2008 to December 31st 2012. At baseline, dMCP-1 and serum biochemical parameters including high sensitivity CRP (hs-CRP) and albumin were checked. All-cause mortality and cause of death were evaluated during the follow-up period. Based on the median level of dMCP-1, patients were classified as either low or high dMCP-1 groups.

RESULTS

Mean age, hs-CRP, and D/Pcr ratio at 4 h were significantly higher, while serum albumin levels and %lean body mass (LBM) were significantly lower in the high dMCP-1 group. During the mean follow-up period of 47.7 months, all-cause mortality and cardiovascular mortality rate were significantly higher in the high dMCP-1 group (9.6 and 6.3 per 100 person-years, respectively) compared to the low dMCP-1 group (5.1 and 3.1 per 100 person-years, respectively; p = 0.021, 0.038). In multivariate Cox analysis, high dMCP-1 was a significant independent predictor of all-cause mortality (hazard ratio: 1.83, 95% confidence interval: 1.03-3.24, p = 0.039).

CONCLUSIONS

dMCP-1 levels are closely correlated with nutritional and systemic inflammatory markers in PD patients. In addition, increased dMCP-1 is significantly associated with higher all-cause and cardiovascular mortality. These findings suggest that local peritoneal inflammation could contribute to poor clinical outcomes in PD patients.

Higher Dialysate Matrix Metalloproteinase-2 Levels Are Associated with Peritoneal Membrane Dysfunction

♦

BACKGROUND

Peritoneal dialysis (PD) patients develop progressive and cumulative peritoneal injury with longer time spent on PD. The present study aimed to a) describe the trend of peritoneal injury biomarkers, matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1), in incident PD patients, b) to explore the capacity of dialysate MMP-2 to predict peritoneal solute transport rate (PSTR) and peritonitis, and c) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on these outcomes. ♦

METHODS

The study included 178 participants from the balANZ trial who had at least 1 stored dialysate sample. Changes in PSTR and peritonitis were primary outcome measures, and the utility of MMP-2 in predicting these outcomes was analyzed using multilevel linear regression and multilevel Poisson regression, respectively. ♦

RESULTS

Significant linear increases in dialysate MMP-2 and TIMP-1 concentrations were observed (p < 0.001), but neither was affected by the type of PD solutions received (MMP-2: p = 0.07; TIMP-1: p = 0.63). An increase in PSTR from baseline was associated with higher levels of MMP-2 (p = 0.02), and the use of standard solutions over longer PD duration (p = 0.001). The risk of peritonitis was independently predicted by higher dialysate MMP-2 levels (incidence rate ratio [IRR] per ng/mL 1.01, 95% confidence interval [CI] 1.005 - 1.02, p = 0.002) and use of standard solutions (Biocompatible solution: IRR 0.45, 95% CI 0.24 - 0.85, p = 0.01). ♦

CONCLUSION

Dialysate MMP-2 and TIMP-1 concentrations increased with longer PD duration. Higher MMP-2 levels were associated with faster PSTR and future peritonitis risk. Administration of biocompatible solutions exerted no significant effect on dialysate levels of MMP-2 or TIMP-1, but did counteract the increase in PSTR and the risk of peritonitis associated with the use of standard PD solutions. This is the first longitudinal study to examine the clinical utility of MMP-2 as a predictor of patient-level outcomes.

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

Background

Endotoxemia is exaggerated and contributes to systemic inflammation and atherosclerosis in patients requiring continuous ambulatory peritoneal dialysis (CAPD). The risk of mortality is substantially increased in patients requiring CAPD for >2 years. However, little is known about the effects of long-term CAPD on circulating endotoxin and cytokine levels. Therefore, the present study evaluated the associations between plasma endotoxin levels, cytokine levels, and clinical parameters with the effects of a short-dwell exchange on endotoxemia and cytokine levels in patients on long-term CAPD.

Methods

A total of 26 patients were enrolled and divided into two groups (short-term or long-term CAPD) according to the 2-year duration of CAPD. Plasma endotoxin and cytokine levels were measured before and after a short-dwell exchange (4-h dwell) during a peritoneal equilibration test (a standardized method to evaluate the solute transport function of peritoneal membrane). These data were analyzed to determine the relationship of circulating endotoxemia, cytokines and clinical characteristics between the two groups.

Results

Plasma endotoxin and monocyte chemotactic protein-1 (MCP-1) levels were significantly elevated in the long-term group. PD duration was significantly correlated with plasma endotoxin (r = 0.479, P = 0.016) and MCP-1 (r = 0.486, P = 0.012). PD duration was also independently associated with plasma MCP-1 levels in multivariate regression. Plasma MCP-1 levels tended to decrease (13.3% reduction, P = 0.077) though endotoxin levels did not decrease in the long-term PD group after the 4-h short-dwell exchange.

Conclusion

Long-term PD may result in exaggerated endotoxemia and elevated plasma MCP-1 levels. The duration of PD was significantly correlated with circulating endotoxin and MCP-1 levels, and was an independent predictor of plasma MCP-1 levels. Short-dwell exchange seemed to have favorable effects on circulating MCP-1 levels in patients on long-term PD.

Nanotechnology and adeno-associated virus-based decorin gene therapy ameliorates peritoneal fibrosis

Peritoneal dialysis (PD) is a life-sustaining therapy for end-stage renal disease (ESRD), used by 10-15% of the dialysis population worldwide. Peritoneal fibrosis (PF) is a known complication of long-term PD and frequently follows episodes of peritonitis, rendering the peritoneal membrane inadequate for dialysis. Transforming growth factor (TGF)-β is an inducer of fibrosis in several tissues and organs, and its overexpression has been correlated with PF. Animal models of peritonitis have shown an increase in expression of TGF-β in the peritoneal tissue. Decorin, a proteoglycan and component of the extracellular matrix, inactivates TGF-β, consequently reducing fibrosis in many tissues. Recently, gold nanoparticles (GNP) have been used for drug delivery in a variety of settings. In the present study, we tested the possibility that GNP-delivered decorin gene therapy ameliorates zymosan-mediated PF. We created a PF model using zymosan-induced peritonitis. Rats were treated with no decorin, GNP-decorin, or adeno-associated virus-decorin (AAV-decorin) and compared with controls. Tissue samples were then stained for Masson's trichrome, enface silver, and hematoxylin and eosin, and immunohistochemistry was carried out with antibodies to TGF-β1, α-smooth muscle actin (α-SMA), and VEGF. Animals which were treated with GNP-decorin and AAV-decorin gene therapy had significant reductions in PF compared with untreated animals. Compared with untreated animals, the treated animals had better preserved peritoneal mesothelial cell size, a significant decrease in peritoneal thickness, and decreased α-SMA. Quantitative PCR measurements showed a significant decrease in the peritoneal tissue levels of α-SMA, TGF-β, and VEGF in treated vs. untreated animals. This study shows that both GNP-delivered and AAV-mediated decorin gene therapies significantly decrease PF in vivo in a rodent model. This approach has important clinical translational potential in providing a therapeutic strategy to prevent PF in PD patients.

Janus kinase signaling activation mediates peritoneal inflammation and injury in vitro and in vivo in response to dialysate

Peritoneal membrane pathology limits long-term peritoneal dialysis (PD). Here, we tested whether JAK/STAT signaling is implicated and if its attenuation might be salutary. In cultured mesothelial cells, PD fluid activated, and the pan-JAK inhibitor P6 reduced, phospho-STAT1 and phospho-STAT3, periostin secretion, and cleaved caspase-3. Ex vivo, JAK was phosphorylated in PD effluent cells from long-term but not new PD patients. MCP-1 and periostin were increased in PD effluent in long term compared with new patients. In rats, twice daily, PD fluid infusion induced phospho-JAK, mesothelial cell hyperplasia, inflammation, fibrosis, and hypervascularity after 10 days of exposure to PD fluid. Concomitant instillation of a JAK1/2 inhibitor virtually completely attenuated these changes. Thus, our studies directly implicate JAK/STAT signaling in the mediation of peritoneal membrane pathology as a consequence of PD.

Intraperitoneal interleukin-6 levels predict peritoneal solute transport rate: a prospective cohort study

BACKGROUND

To evaluate the association of dialysate interleukin-6 (IL-6), a marker of ongoing peritoneal inflammation, with the alteration of peritoneal solute transport rate (PSTR) in continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS

Stable CAPD patients were enrolled in the present study. A total of 128 patients were analyzed in this prospective study. IL-6 concentration in the overnight effluent was determined and expressed as the IL-6 appearance rate (IL-6AR). Mass transfer area coefficients of creatinine (MTACcr) were measured at enrollment and 12 months later. Logistic regression was used to examine the association between IL-6AR and change in MTACcr.

RESULTS

Multivariable linear regression showed that historical glucose exposure was significantly associated with dialysate IL-6AR level [β = 0.008 (0.001-0.015), p = 0.021]. After 12 months, MTACcr was significantly increased [6.40 (4.70-8.75) vs. 7.14 (5.69-8.73) ml/min, p = 0.004], while ultrafiltration capacity decreased [4 h UF 340 (220-400) vs. 280 (180-380) ml, p = 0.006]. Compared to the patients with stable PSTR, the dialysate IL-6AR in patients with increasing PSTR was significantly higher [277.08 (247.45-349.53) vs. 263.18 (69.94-286.72) pg/min, p = 0.015]. Patients with increasing PSTR had lower residual renal function [0.79 (0-2.12) vs. 1.70 (0.39-3.38) ml/min, p = 0.006] and less urine output [225 (0-600) vs. 500 (125-900) ml/24 h, p = 0.014]. Logistic analysis showed that both high dialysate IL-6AR [OR 1.333 and 95% CI (1.024-1.735), p = 0.033] and low RRF [OR 0.831 and 95% CI (0.699-0.988), p = 0.036] were independent risk factors for increasing PSTR.

CONCLUSIONS

This prospective study suggests that intraperitoneal IL-6 is a predictor of increasing PSTR in peritoneal dialysis patients.

Clinical causes of inflammation in peritoneal dialysis patients

Inflammation at both systemic and local intraperitoneal levels commonly affects peritoneal dialysis (PD) patients. Interest in inflammatory markers as targets of therapeutic intervention has been considerable as they are recognised as predictors of poor clinical outcomes. However, prior to embarking on strategies to reduce inflammatory burden, it is of paramount importance to define the underlying processes that drive the chronic active inflammatory status. The present review aims to comprehensively describe clinical causes of inflammation in PD patients to which potential future strategies may be targeted.

Baseline serum interleukin-6 predicts cardiovascular events in incident peritoneal dialysis patients

BACKGROUND

The utility of local and systemic interleukin 6 (IL-6) as a prognostic marker in incident peritoneal dialysis (PD) patients remains to be fully defined. The present study aimed to explore the capacity of systemic IL-6 concentrations to predict cardiovascular events (CVEs) and mortality in PD patients, and to evaluate the influence of neutral-pH PD solutions low in glucose degradation products (GDPs) on systemic IL-6.

METHODS

The study included 175 incident participants from the balANZ trial with at least one stored serum sample. A composite CVE score was used as the primary clinical outcome measure. Multilevel linear regression and Poisson regression models were fitted to describe, respectively, the trend of serum IL-6 over time and its ability to predict composite CVE.

RESULTS

A significant increase in serum IL-6 from baseline to 24 months was observed in the study population (mean difference: 1.68 pg/mL; p = 0.006). The type of PD solution received by patients exerted no significant effect on serum IL-6 (p = 0.12). Composite CVE was significantly and independently associated with baseline serum IL-6 (incidence rate ratio per picogram per milliliter: 1.06; 95% confidence interval: 1.02 to 1.10; p = 0.003).

CONCLUSIONS

Baseline serum IL-6 was a significant independent predictor of composite CVE. Serum IL-6 concentrations increased with increasing PD duration and were not significantly modified with the use of biocompatible fluid over the study period. The present study is the first to link systemic IL-6 concentrations with CVE outcomes in incident PD patients.

Dialysate interleukin-6 predicts increasing peritoneal solute transport rate in incident peritoneal dialysis patients

Background

Repeated exposure to peritoneal dialysis (PD) solutions contributes to cumulative intraperitoneal inflammation and peritoneal injury. The present study aimed to explore the capacity of dialysate interleukin-6(IL-6) to a) predict peritoneal membrane function and peritonitis in incident PD patients, and b) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on dialysate IL-6 levels.

Methods

The study included 88 incident participants from the balANZ trial who had completed 24-months of follow-up. Change in peritoneal solute transport rate (PSTR) and peritonitis were primary outcome measures, and the utility of IL-6 and IL-6 appearance rate (IL-6 AR) in predicting these outcomes was analyzed using multilevel linear regression and Cox proportional hazards models, respectively. Sensitivity analyses were performed by analyzing outcomes in a peritonitis-free cohort (n = 56).

Results

Dialysate IL-6 concentration significantly increased from baseline to 24 months (mean difference 19.07 pg/mL; P < 0.001) but was not affected by the type of PD solution received (P = 0.68). An increase in PSTR from baseline was associated with higher levels of IL-6 (P = 0.004), the use of standard solutions (P = 0.005) and longer PD duration (P < 0.001). Baseline IL-6 level was not associated with a shorter time to first peritonitis (adjusted hazard ratio 1.00, 95% CI 0.99-1.00, P = 0.74). Analysis of IL-6 AR as well as sensitivity analyses in a peritonitis-free cohort yielded comparable results.

Conclusion

Dialysate IL-6 concentration increased with longer PD duration and was a significant, independent predictor of PSTR. The use of biocompatible PD solutions exerted no significant effect on dialysate IL-6 levels but did abrogate the increase in PSTR associated with standard PD solutions. This is the first study to examine the impact of biocompatible solutions on the utility of IL-6 in predicting PSTR and peritonitis.

Longitudinal study of small solute transport and peritoneal protein clearance in peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Peritoneal protein clearance (Pcl) is determined by both effective (small pores) membrane area and relative capillary leakiness (large pores). It is not known how these two components change with duration of peritoneal dialysis (PD) in the context of progressive membrane injury and differential attrition of patients with higher Pcl, which has been associated with increased mortality risk in several studies.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients treated continuously from 2000 to 2011 for a minimum of 4 years were selected from the longitudinal prospective Stoke PD Study. Pcl, membrane area (peritoneal solute transport rate [PSTR]), dialysis prescription, and residual renal function were measured every 6 months, along with comorbidity and peritonitis events. Multilevel multivariate analysis was used to determine associations with Pcl over time, taking into account within-subject correlations.

RESULTS

From 280 incident patients, 335 datasets were analyzed from 49 patients receiving treatment for 4 years. Pcl correlated with PSTR at baseline (R=0.61; P<0.01), but over time there was progressive uncoupling of this relationship (year 4, R=0.28; P=0.05) with increasing PSTR (0.66-0.74; P<0.01) and stable Pcl (78.4-81.9 ml/d; P=0.7). Multivariate analysis found that age, PSTR, daily ultrafiltration, and sodium removal were significant predictors of Pcl when adjusted for sex, comorbidity, glucose exposure, and residual renal function. Peritonitis was associated with increased PSTR but a similar pattern of uncoupling.

CONCLUSION

There is a progressive dissociation of the small- and large-pore pathways with time on PD, which would be in keeping with a switch from local inflammation early on to progressive fibrosis, combined with increased vascular surface area. Measuring longitudinal changes in Pcl may complement membrane function tests used to monitor progressive injury.

Diabetic patients could do as well as non-diabetic patients without inflammation on peritoneal dialysis

Background

Diabetic patients on peritoneal dialysis (PD) have lower survival and are more likely complicated with inflammation than their non-diabetic counterparts. Here, we explored the interaction effects between diabetes and inflammation on the survival of PD patients.

Methods

Overall, 2,264 incident patients were enrolled from a retrospective cohort study in China. Patients were grouped according to the baseline levels of high-sensitive C-reactive protein (hsCRP, ≤3 mg/L or >3 mg/L) or serum albumin (SA, ≥38 g/L or <38 g/L). Then, several multivariable adjusted stratified Cox regression models were constructed for these groups to explore the predicted role of diabetes on all-cause or cardiovascular death under inflammatory or non-inflammatory conditions.

Results

Diabetics on PD were more likely to have inflammation than non-diabetics on PD, and they presented with elevated hsCRP (52.7% vs. 47.3%, P = 0.03) or decreased SA (77.9% vs. 62.7%, P < 0.001) levels. After stratification by size of center and controlling for confounding factors, diabetes was found to predict all-cause death in patients with hsCRP >3 mg/L or SA <38 g/L but not in patients with hsCRP ≤3 mg/L or SA ≥38 g/L. Similarly, the presence of diabetes was an indication of cardiovascular death in patients with hsCRP >3 mg/L or SA <38 g/L. However, if further adjusted by baseline cardiovascular disease, the predicted role of diabetes on death related to cardiovascular disease in patients with SA <38 g/L disappeared.

Conclusion

Diabetic patients could do as well as non-diabetic patients without inflammation on peritoneal dialysis. Active strategies should be implemented to improve inflammation status in diabetic patients on PD.