Clinical and Physiological Effects of a New, Less Toxic and Less Acidic Fluid for Peritoneal Dialysis

Objective

To report our first clinical experience with a new continuous ambulatory peritoneal dialysis (CAPD)fiuid (PD-Bio), which is nearly devoid of glucose degradation products and has a higher pH (6.3) than conventional peritoneal dialysis (PD) solutions, and to discuss in general terms some acute and long-term effects of conventional acidic solutions containing glucose degradation products.

Design

1) Pilot study on 4 patients investigated using a modified peritoneal equilibration test (PET) and cytobiology parameters. 2) Computer simulation study, assuming that conventional acidic solutions cause vasodilatation and recruitment of capillary surface area initially (during 0–60 minutes) in a PD dwell.

Patients

Four stable CAPD patients were chosen in an open cross-over study. After a period of three months using conventional PD fluid, the patients were switched to three months on the new PD fluid.

Results

Cancer antigen 125 increased significantly, and patients with discomfort/infusion pain during the control period improved during the period with the new fluid. No significant changes were observed in mass-transfer coefficients or drained volumes with the new solution. PH in the effluent dialysis was, however, higher for PD-Bio at all times during a two-hour dwell. In the computer simulation study, a less acidic solution caused an initially lower rate of glucose dissipation and improved ultrafiltration (UF) after a four -hour dwell, as compared to a conventional PD solution.

Conclusion

A new, differently produced, less toxic and less acidic PD fluid (PD-Bio) seems to be better tolerated than a conventional acidic solution with respect to discomfort/infusion pain. Theoretically, neutralized solutions should show slightly improved UF profiles over conventional acidic solutions, according to the computer simulation analysis. Furthermore, it is speculated that a neutral, less acidic, less toxic fluid would cause less interstitial-mesothelial alterations and less impairment of UF capacity than conventional solutions during longterm CAPD.

Peritoneal Kinetics and Mesothelial Markers in CCPD Using Icodextrin for Daytime Dwell for Two Years

Objective

To evaluate the safety, efficacy, and biocompatibility of icodextrin (Ico), continuous cycling peritoneal dialysis (CCPD) patients were treated for 2 years with either Ico- or glucose (Glu)-containing dialysis fluid for their daytime dwell (14 – 15 hours). Prior to entry into the study, all patients used standard Glu solutions (Dianeal, Baxter BV, Utrecht, The Netherlands).

Design

Open, randomized, prospective two-center study.

Setting

University hospital and teaching hospital.

Patients

Both established patients and patients new to CCPD were included. A life expectancy of more than 2 years, a stable clinical condition, and written informed consent were necessary before entry. Patients aged under 18 years or with peritonitis in the previous month, and women of childbearing potential unless taking adequate contraceptive precautions, were excluded. Thirty-eight patients entered the study (19 Glu, 19 Ico).

Main Outcome Measures

Daytime dwell peritoneal effluents were collected every 3 months in combination with other study variables (clinical data, laboratory measurements, dialysis-related data, and urine collection). Peritoneal transport studies were carried out every 6 months.

Results

In Glu- and Ico-treated patients, peritoneal transport of low molecular weight solutes and protein clearances neither changed during follow-up nor differed between the two groups. Peritoneal membrane markers (CA125, interleukin-8, carboxyterminal propeptide of type I procollagen, and aminoterminal propeptide of type III procollagen) measured in effluents did not differ between the groups and did not change over time. All these markers showed a dialysate/plasma ratio of more than 1, suggesting local production. Residual renal function remained stable during follow-up and adverse clinical effects were not observed.

Conclusions

Peritoneal membrane transport kinetics and markers remained stable in both groups over a 2-year follow-up period. Membrane markers were higher in effluents than in serum, suggesting local production. No clinical side effects were demonstrated. Icodextrin was a well-tolerated effective treatment.

Peritoneal Dialysis

These presentations highlighted some of the current research needs in peritoneal dialysis. They are not meant to eclipse other important issues, such as adequacy and nutrition. These needs have become apparent as the therapy has evolved and progressed. They in fact are a testament to the increasing acceptance, use, and development of the therapy and suggest that there is potential for even further advancement for the therapy of peritoneal dialysis in the future.

High Glucose Solution and Spent Dialysate Stimulate the Synthesis of Transforming Growth Factor-β1of Human Peritoneal Mesothelial Cells: Effect of Cytokine Costimulation

Objective

To investigate the effect of high glucose and spent peritoneal dialysate on the transforming growth factor-β1(TGFβ1) synthesis of cultured human peritoneal mesothelial cells (HPMCs) and to examine the effect of costimulation with high glucose or spent dialysate, and cytokines, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNFα) on TGFβ1synthesis of HPMCs.

Design

HPMCs were exposed to different concentrations of glucose (30, 60, and 90 mmol/L) or spent peritoneal dialysate for 48 hours in the absence or presence of IL-1β (1 ng/mL) and TNFα (1 ng/mL). TGFβ1mRNA expression was assessed by Northern blot analysis and TGFβ1protein release by Western blot analysis and enzymelinked immunosorbent assay (ELISA).

Results

Exposure of HPMCs to high glucose conditions (30, 60, and 90 mmol/L of D-glucose) induced 2.3-, 3.6-, and 4.0-fold increases in TGFβ1mRNA expression of HPMC with enhanced TGFβ1protein synthesis and secretion into the media, whereas there were no significant changes in TGFβ1synthesis with equimolar concentrations of D-mannitol. Incubation with spent dialysate also significantly increased TGFβ1mRNA expression and protein secretion compared to control media ( p < 0.05). Stimulation with IL-1β (1 ng/mL) or TNFα (1 ng/mL) resulted in a significant increase in TGFβ1mRNA expression after 48 hours: 2.7 and 2.1 times the control level, respectively. However, TNFα-induced increase in TGFβ1mRNA expression was not translated into TGFβ1protein secretion, while IL-1β stimulation induced a significant increase in TGFβ1protein secretion as well as TGFβ1mRNA expression. Combined stimulation by high glucose or spent dialysate, together with IL-1β or TNFα, showed a greater increase in TGFβ1mRNA expression and protein secretion compared to stimulation by high glucose or spent dialysate alone.

Conclusion

Our results clearly show that high glucose solution and spent dialysate themselves might be sufficient to stimulate the production of TGFβ1by peritoneal mesothelial cells. In peritoneal dialysis patients, this state of chronic induction of TGFβ1is further exacerbated in the presence of peritonitis because of the stimulatory effect of proinflammatory cytokines, resulting in augmented TGFβ1synthesis, thus promoting peritoneal fibrosis.

Peritoneal dialysis solution induces apoptosis of mesothelial cells

For better simulation of the long-dwell exchanges in conventional CAPD, we have developed a modified mesothelial cell culture system consisting of a Transwell culture apparatus. The equilibration patterns of pH, dextrose and osmolality in the present culture system were observed to be very similar to those in human CAPD. The effects of six different peritoneal dialysis solutions on the apoptosis of mesothelial cells were evaluated using this modified culture system. The results imply that peritoneal dialysis solution per se may incite apoptosis of mesothelial cells, and also that low calcium peritoneal dialysis solution is a milder apoptosis stimulant as compared to the conventional peritoneal dialysis solution. Moreover, varying concentrations of dextrose in the peritoneal dialysis solution were not observed to significantly affect the apoptosis rate. The roles of ambient high concentrations of calcium and dextrose, low pH, as well as high osmolality in the apoptosis are also discussed.

In vitro simulation of the effect of peritoneal dialysis solution on mesothelial cells

All previous in vitro biocompatibility tests of peritoneal dialysis fluids have shown that these have inhibitory effects on the function of peritoneal mesothelium. This report presents results from in vitro experiments performed to study the effect of dialysis fluids (Dianeal 1.36 and Dianeal 3.86; Baxter, Round Lake, IL) on the function of mesothelial cells under conditions that simulate the in vivo state of these solutions in the peritoneal cavity. Thus, cells were initially exposed only to the unused fluids that were thereafter gradually diluted (over 4 hours) with pooled effluent dialysate from continuous ambulatory peritoneal dialysis patients. During the following 20 hours, cells were incubated in a mixture of unused fluid (10% vol/vol) and dialysate effluent (90% vol/vol). The mesothelial cells exposed to dialysis fluids under such conditions became activated cells compared with exposed to dialysate effluent (control) alone. Thus, synthesis by mesothelial cells of all tested substances was enhanced during exposure of the mesothelium to the dialysis fluids: interleukin-6: Dianeal 1.36, +257%; Dianeal 3.86, +181% (both P < 0.05); hyaluronic acid: Dianeal 1.36, +72%; Dianeal 3.86, +63% (both P < 0.05); tissue plasminogen activator: Dianeal 3.86, +33% (P < 0.05); and plasminogen activator/inhibitor-1: Dianeal 1.36, +28%; Dianeal 3.86, +38% (both P < 0.05). Our results show that the peritoneal mesothelium becomes activated when it is exposed to acidic, hyperosmotic dialysis fluids diluted with the dialysate effluent, in a manner that imitates the in vivo changes in these solutions during their intraperitoneal dwell.