Sylvie Opatrná

Cell-Free Plasma DNA during Peritoneal Dialysis and Hemodialysis and in Patients with Chronic Kidney Disease

The mechanisms of clearance of circulating plasma DNA are not fully understood, and so we aimed to examine it in patients with impaired renal function compared with healthy individuals. We also assessed the effect of peritoneal dialysis and hemodialysis on circulating plasma cell‐free DNA (cfDNA) in our treated patients. Overall, 20 healthy volunteers, 20 patients with chronic kidney disease (CKD), 18 patients undergoing peritoneal dialysis (PD), and 17 patients on hemodialysis (HD; high‐flux polysulfone membrane) were examined. Cell‐free DNA levels were determined using real‐time GADPH gene sequence amplification. The levels of cfDNA in all groups of our patients did not differ significantly from those of healthy volunteers. In HD patients, cfDNA levels were significantly increased compared with those of CKD patients (P < 0.05) and PD‐treated patients (P < 0.01). In PD‐treated patients, cfDNA was detectable in overnight effluent, with its levels correlating inversely with the duration of PD treatment (r=−0.619, Spearmans coefficient, P= 0.008). Factors contributing to these differences may include changes in the quality and quantity of the cell population of the peritoneum, highlighting the need for additional studies clarifying the dynamics of cfDNA during PD. The plasma levels of cfDNA do not seem to be dramatically altered even in CKD patients or those on PD or HD (as long as they are measured prior to the procedure in the latter two). Our data suggest renal elimination is not the main mechanism of circulating cfDNA clearance.

Asymmetric dimethylarginine in hemodialysis, hemodiafiltration, and peritoneal dialysis.

Asymmetric dimethylarginine (ADMA) is a mediator of endothelial dysfunction. Production and elimination of ADMA may be affected by the type of renal replacement therapy used and oxidative stress. Plasma ADMA, advanced glycation end products (AGE), and homocysteine were assessed in 59 subjects: 20 hemodialysis (HD) patients, 19 patients undergoing peritoneal dialysis (PD), and 20 controls. Results were compared between the groups. The effect of 8 weeks of HD and high-volume predilution hemodiafiltration (HDF) was compared in a randomized study. HD patients showed higher ADMA (1.20 [0.90-1.39 micromol/L]) compared to controls (0.89 [0.77-0.98], P < 0.01), while ADMA in PD did not differ from controls (0.96 [0.88-1.28]). AGE and homocysteine were highest in HD, lower in PD (P < 0.01 vs. HD), and lowest in controls (P < 0.001 vs. HD and PD). PD patients had higher residual renal function than HD (P < 0.01). The decrease in ADMA at the end of HD (from 1.25 [0.97-1.33] to 0.66 [0.57-0.73], P < 0.001) was comparable to that of HDF. Switching from HD to HDF led to a decrease in predialysis homocysteine level in 8 weeks (P < 0.05), while ADMA and AGE did not change. Increased ADMA levels in patients undergoing HD, as compared to PD, may be caused by higher oxidative stress and lower residual renal function in HD. Other factors, such as diabetes and statin therapy, may also be at play. The decrease in ADMA at the end of HD and HDF is comparable. Switching from HD to HDF decreases in 8 weeks the predialysis levels of homocysteine without affecting ADMA.

Tissue-Type Plasminogen Activator (tPA) and Its Inhibitor (PAI-1) in Patients Treated with Continuous Ambulatory Peritoneal Dialysis

Aim: To establish whether the values of two key enzymes of fibrinolysis, tissue-type plasminogen activator (tPA) and its inhibitor (PAI-1), differ between patients treated with continuous ambulatory peritoneal dialysis (CAPD) and healthy volunteers and whether plasma and dialysate tPA and PAI-1 values vary during one exchange of dialysis solution. Methods: A total of 11 patients with chronic renal failure, treated with CAPD during the peritoneal equilibration test (in addition with blood sampling at time 0), and a control group of 11 healthy volunteers were examined. To identify the factors involved in the changes in tPA and PAI-1, 9 CAPD patients were subsequently monitored, in a crossover manner, during dialysis with solutions of 1.36 and 3.86% dextrose and off dialysis. Results: Compared with healthy individuals, CAPD-treated patients showed a significantly lower tPA activity (0.39 vs. 0.81 IU/ml, p < 0.05). Changes in plasma fibrinolysis during one exchange of dialysis solution were characterized mainly by a decrease in PAI-1 concentrations and activities caused by the circadian rhythm of fibrinolysis. To explain, in the crossover part of the study, the values of plasma PAI-1 antigen at time 0 (07.00 h) and at time 2 (09.00 h) were 9.4 versus 6.5 ng/ml with the 1.36% solution (p < 0.05), 8.2 versus 4.9 with the 3.86% solution (p < 0.05), and 14.1 versus 9.1 ng/ml off dialysis (p < 0.01). Compared to baseline (0 ng/ml with 1.36 as well as 3.86% solutions), the levels of PAI-1 antigen in dialysis solution rose, apparently due to local production in the peritoneal cavity, to 0.5 ng/ml (p < 0.05) with the 1.36% solution, to 0.7 (p < 0.05) with the 3.86% solution after a 2-hour dwell time, and to 1.6 (p < 0.05) and 1.3 ng/ml (p < 0.05) after a 4-hour dwell time, respectively. Hence, the different dextrose levels in the dialysis solutions had no effect on the monitored parameters of fibrinolysis. Conclusion: The lower activity of plasma tPA, and the increase in PAI-1 levels in dialysis solutions may contribute to the development of thromboses in CAPD patients and to fibrin formation on the peritoneal surface with consequences such as peritoneal fibrosis.

Relationship between Anemia and Adequacy of Continuous Ambulatory Peritoneal Dialysis

Sylvie Opatrná, MD, 1st Department of Internal Medicine, Charles University, Alej Svobody 80, CS-304 60 Plzen (Czech Republic), Tel. +42 19 522564, fax +42 19 531110 Dear Sir, It is generally recognized that anemia is a common symptom of chronic renal failure which causes a number of serious problems to the patient. Some studies claim that, in hemodialysis patients, success in treating anemia depends on the efficacy of dialysis therapy. The importance of adequate hemodialysis for successful control of anemia has recently received authoritative support especially by a study conducted by Ifudu et al. [1]· Regarding the relationship between anemia and efficacy of continuous ambulatory peritoneal dialysis (CAPD), it has been explored to a much lesser extent than was the case for hemodialysis, and, what is more, the results are controversial. While some studies have not demonstrated an association, other authors have, even though in case reports [2-4]. Because of the paucity of unambiguous information, we conducted a study designed to establish whether or not the renal anemia in patients with chronic renal failure is affected by the adequacy of CAPD. We examined 22 patients with a mean age of 51.8 (20-79) years (arithmetic mean and range) treated by CAPD (Twin-Bag System; Baxter, Deerfield, Ill., USA) for 14.8 (1.5-52) months for chronic renal failure caused by chronic tubulointerstitial nephritis in 8 cases, chronic glomerulonephritis in 7, diabetic nephropathy in 5, polycystic kidney disease in 1 ‚ and Fanconi’s syndrome in 1 case. None of the patients received recom-binant human erythropoietin or blood transfusion for renal anemia. At the same time the hematocrit was 30.9% (19.4-43.3). The KT/ V index had not changed for 6.3 (1.5-24) months prior to the study when it was at 2.0 (1.4-2.8) per week. The residual glomerular filtration rate (GFR) was 4.8 (0-9.4) ml/ min. The efficacy of blood purification was assessed by the KT/V index considering both peritoneal and renal urea clearances [KT/ Vurea = (Durea/Purea·VD + Curea)/Vtot] and by weekly creatinine clearance corrected for body surface area (BSA), again considering both peritoneal and renal eliminations (Ccrea/BSA = Dcrea/Pcrea·VD·7 + GFRest). The residual GFR was determined as the arithmetic mean of urea and creatinine clearances [GFRest = (Curea + Ccrea)/2] [5]. Besides the hematocrit, we examined, using standard methods,

Intraperitoneal IL-6 Signaling in Incident Patients Treated with Icodextrin and Glucose Bicarbonate/Lactate–Based Peritoneal Dialysis Solutions

♦ Objective: In this study, we compared the activity of interleukin-6 (IL-6), a marker of ongoing peritoneal inflammation and biocompatibility, and its other signaling components, the soluble IL-6 receptor (sIL-6R) and soluble Gp130 (sGp130), in peritoneal effluent from patients treated with icodextrin-based (E) peritoneal dialysis (PD) solution and glucose-based bicarbonate/lactate–buffered (P) solution. ♦ Methods: Using baseline peritoneal ultrafiltration capacity, 33 stable incident PD patients were allocated either to P only (n = 20) or to P plus E for the overnight dwell (n = 13). We used ELISA to determine IL-6, sIL-6R, and sGp130 in timed overnight effluent at 1, 6, and 12 months after PD initiation. Flow cytometry was used to measure expression of IL-6R and Gp130 on isolated peritoneal leukocytes at the same time points. Peritonitis was an exclusion criterion. ♦ Results: At all time points, levels of IL-6 and sIL-6R, and the appearance rates of IL-6 (90.5 pg/min vs. 481.1 pg/min, p < 0.001; 138.6 pg/min vs. 1187.5 pg/min, p < 0.001; and 56.1 pg/min vs. 1386.0 pg/min, p < 0.001), sIL-6R (2035.3 pg/min vs. 4907.0 pg/min, p < 0.01; 1375.0 pg/min vs. 6348.4 pg/min, p < 0.01; and 1881.3 pg/min vs. 5437.8 pg/min, p < 0.01), and sGp130 (37.6 ng/min vs. 65.4 ng/min, p < 0.01; 39.2 ng/min vs. 80.6 ng/min, p < 0.01; 27.8 ng/min vs. 71.0 ng/min, p < 0.01) were significantly higher in peritoneal effluent from E-treated patients than from P-treated patients. Expression of IL6-R and Gp130 on individual leukocyte types isolated from PD effluent did not differ between E- and P-treated patients. The numbers of white blood cells present in effluent were higher in E-treated than in P-treated patients at all time points, but no significant differences were seen in the differential counts or in the number of exfoliated mesothelial cells. The IL-6 parameters in effluent from E-treated patients correlated with their plasma C-reactive protein. Despite the increased activation of the IL-6 system, no increase in peritoneal permeability as assessed by the dialysate-to-plasma ratio of creatinine in E effluent or by systemic inflammation was observed throughout the study. ♦ Conclusions: Higher levels of IL-6, its soluble receptors, and leukocyte expression were observed in E-treated than in P-treated patients, but this difference was not associated with alterations in peritoneal permeability or systemic inflammation during 1 year of follow-up. Leukocyte counts in effluent from E-treated patients were within the normal range previously reported for glucose solutions. This lack of clinical consequences may be a result of a parallel rise in sIL-6R and sGp130, which are known to control the biologic activity of IL-6. The utility of IL-6 level determinations, in isolation, for assessing the biocompatibility of PD solutions is questionable.

Tissue Factor, Its Pathway Inhibitor, and Metabolic Disturbances in Long-Term Peritoneal Dialysis

Background/Aim: The tissue factor (TF) plays a key role in triggering the coagulation system in vivo. Our study was designed to determine whether or not the plasma levels of TF and its pathway inhibitor (TF pathway inhibitor; TFPI) in patients with chronic renal failure (CRF) treated by peritoneal dialysis (PD) (1) are pathologically altered; (2) differ between diabetics and nondiabetics, and (3) depend on the metabolic disorders associated with CRF and/or diabetes. Methods: Using ELISA, plasma TF and TFPI levels were measured once in 21 PD patients (10 with diabetes, 11 without diabetes) and in 21 healthy subjects. Results: As compared with healthy subjects (TF 282 pg/ml; TFPI 73 ng/ml), both TF and TFPI levels were significantly higher in PD patients with diabetes (485 pg/ml, p < 0.001, and 106 ng/ml, p < 0.01, respectively) and in PD patients without diabetes (480 pg/ml, p < 0,001, and 121 ng/ml, p < 0.001, respectively). The difference between diabetics and nondiabetics was not significant. In stepwise regression analysis, the TF levels depended on serum creatinine (partial correlation 0.39, p < 0.05), glycemia (0.43, p < 0.01), and insulin (–0.43, p < 0.05), and the TFPI levels depended on creatinine (partial correlation 0.67, p < 0.001), apolipoprotein B (0.46, p < 0.01), and plasma fibrinogen (0.43, p < 0.01). Conclusions: CRF patients on PD show increased plasma TF and TFPI levels. There is no difference between diabetics and nondiabetics. The TF and TFPI levels depend significantly on the renal function, as assessed by serum creatinine, and on some metabolic disorders. Elevated TF and TFPI levels may be related to thrombosis and atherosclerosis in CRF patients on PD.

Cell-Free Plasma DNA during Hemodialysis

Purpose. Cell-free plasma DNA (cfDNA) levels originating predominantly from apoptotic leukocytes were found to rise during hemodialysis (HD) session, and as such are considered a marker of HD membrane biocompatibility. The purpose of our study was to determine the changes of cfDNA during two consecutive high-flux polysulphone HD sessions after a long (HD-L) and short (HD-S) interdialytic interval. Methods. A total of 17 HD patients were examined. Prior to HD and at 30 and 240 min, cfDNA (using real-time PCR) and leukocyte count were determined. Results. No significant difference was found when comparing pre-HD-S with pre-HD-L cfDNA [4893 (1090–28804) vs. 4589 (691–73796) genomic equivalent/mL]. A significant increase in cfDNA at 240 min was seen in HD-L (p < 0.05) but not in HD-S. Leukocyte count correlated with cfDNA levels before HD-S (r = 0.8; p < 0.01); however, no other correlation was seen between routinely measured biochemical markers and pre-HD cfDNA levels or cfDNA changes during HD. The increase in plasma cfDNA during HD did not correlate with dialysis duration, its efficacy, or ultrafiltration. An association between magnitude of diuresis and cfDNA levels in HD-S was found (r = 0.58; p < 0.05). Conclusions. The behavior of cfDNA during HD after long and short interdialytic interval is inconsistent and cannot be explained by changes in laboratory and clinical parameters. The observed relationship of plasma cfDNA levels with diuresis deserves further investigation.

Low Glucose Degradation Product Peritoneal Dialysis Regimen Is Associated With Lower Plasma EN‐RAGE and HMGB‐1 Proinflammatory Ligands of Receptor for Advanced Glycation End Products

Intraperitoneal glucose degradation products (GDP) load influences systemic advanced glycation end products (AGEs) but the effects on soluble receptor for AGEs (s‐RAGE) and its proinflammatory ligands: extracellular newly identified receptor for advanced glycation end‐products binding protein(EN‐RAGE) and high mobility group box‐1 protein (HMGB‐1) are unknown. We aimed to compare plasma and peritoneal s‐RAGE, EN‐RAGE and HMGB‐1 between three peritoneal dialysis (PD) prescription regimens with different intraperitoneal GDP loads. High GDP load (glucose‐lactate PD fluid, D; N = 8) was compared with a low (glucose‐bicarbonate/lactate with icodextrin for overnight dwell, E; N = 9) and a very low GDP load (glucose‐bicarbonate/lactate, P; N = 16). D group demonstrated higher plasma EN‐RAGE, 77.8 ng/mL, vs. both E, 11.2, P < 0.001 and P, 27.0, P < 0.001 as well as higher plasma HMGB‐1, 2.2 ng/mL vs. both E, 1.1, P < 0.01 and P, 1.5, P < 0.01. Plasma s‐RAGE, which did not differ between D, E and P, correlated with its effluent levels. Patients with faster peritoneal transport (D/Pcr > 0.65) tended to have higher plasma s‐RAGE compared to slow transporters (2300 vs. 1762 pg/mL, P = 0.056). Peritoneal clearance of s‐RAGE and EN‐RAGE was higher with E compared to both D and P (P < 0.001 resp. P < 0.01). Subgroup of PD patients with CRP above median demonstrated higher plasma HMGB‐1 and EN‐RAGE, P < 0.05 for both. A lower intraperitoneal GDP load is associated with decreased plasma levels of EN‐RAGE and HMGB‐1. Peritoneal transport, microinflammation and the capability of icodextrin to increase peritoneal clearance of middle molecular weight substances might also exert an effect on plasma s‐RAGE and its proinflammatory ligands levels.

Acid-base balance in peritoneal dialysis patients: a Stewart-Fencl analysis.

Background. Evaluation of acid-base disorders using the Stewart-Fencl principle is based on assessment of independent factors: strong ion difference (SID) and the total concentration of non-volatile weak acids (Atot). This approach allows for a more detailed evaluation of the cause of acid-base imbalance than the conventional bicarbonate-centered approach based on the Henderson-Hasselbalch principle, which is a necessary yet insufficient condition to describe the state of the system. The aim of our study was to assess acid-base disorders in peritoneal dialysis (PD) patients using both of these principles. Methods. A total of 17 patients with chronic renal failure (10 men), aged 60.7 (22–84) years, treated by PD for 25.7 (1–147) months were examined. A control group included 17 healthy volunteers (HV) (8 males), with a mean age of 42.7 (22–77) years and normal renal function. Patients were treated with a solution containing bicarbonate (25 mmol/L) and lactate (15 mmol/L) as buffers; eleven of them used, during the nighttime dwell, a solution with icodextrin buffered by lactate at a concentration of 40 mmol/L. The following equations were employed for calculations of acid-base parameters according to the Stewart-Fencl principle. The first is SID = [Na+] + [K+] + 2[Ca2+] + 2[Mg2+] − [Cl−] − [UA−], where SID is the strong ion difference and [UA−] is the concentration of undetermined anions. For practical calculation of SID, the second equation, SID = [HCO3−] + [Alb−] + [Pi−], was used, where [Alb−] and [Pi−] are the charges carried by albumin and phosphates. The third is Atot, the total concentration of weak non-volatile acids, albumin [Alb] and phosphates [Pi]. Results. The capillary blood pH in PD group was 7.41 (7.27–7.48), [HCO3−] levels 23.7 (17.6–29.5) mmol/L, SID 36.3 (29.5–41.3) mmol/L, sodium-chloride difference 39.0 (31.0–44.0) mmol/L, [Pi] 1.60 (0.83–2.54) mmol/L, and [Alb] 39.7 (28.8–43.4) g/L (median, min-max). Bicarbonate in blood correlated positively with SID (Rho = 0.823; p < 0.001), with the sodium-chloride difference (Rho = 0.649; p < 0.01) and pH (Rho = 0.754; p < 0.001), and negatively with residual renal function (Rho = −0.517; p < 0.05). Moreover, the sodium-chloride difference was also found to correlate with SID (Rho = 0.653; p < 0.01). While the groups of PD and HV patients did not differ in median bicarbonate levels, significantly lower median value of SID were observed in PD patients, 36.3 vs. 39.3 mmol/L (p < 0.01); additionally, PD patients were shown to have significantly lower mean value of serum sodium levels, 138 vs. 141 mmol/L (p < 0.01), and serum chlorides levels, 100 vs. 104 mmol/L (p < 0.001). Despite the higher [UA−] levels in PD patients, 9.1 vs. 5.4 mmol/L (p < 0.001), this parameter was not found to correlate with bicarbonate levels. Conclusions. The results suggest that the decreased bicarbonate in PD patients results from a combination of decreased sodium-chloride difference and mildly increased unmeasured anions.

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)×106/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.