Impact of Glucose in Peritoneal Dialysis: Saint or Sinner?

Peritoneal dialysis (PD) solutions using glucose as osmotic agent have been used for more than two decades as effective treatment for patients with end-stage renal disease. Although alternative osmotic agents such as amino acids and macromolecular solutions, including polypeptides and glucose polymers, are now available, glucose is still the most widely used osmotic agent in PD. It has been shown to be safe, effective, readily metabolized, and inexpensive. On the other hand, it is widely assumed that exposure of the peritoneal membrane to high glucose concentrations contributes to both structural and functional changes in the dialyzed peritoneal membrane. As in diabetes, glucose, either directly or indirectly through the generation of glucose degradation products or the formation of advanced glycation end products, may contribute to peritoneal membrane failure. Although efforts to reduce glucose toxicity have been made for years, only a few suggestions, such as dual-bag systems with bicarbonate as buffer system, have found broader acceptance. Recently, some interesting new approaches to the problem of glucose-related toxicity have been made, but further investigations will be necessary before they can be used clinically. This review will focus on adverse effects of glucose in PD solutions and summarize different aspects of glucotoxicity and potential therapeutic interventions.

Malignant peritoneal mesothelioma

BACKGROUND AND OBJECTIVES

The incidence of malignant peritoneal mesothelioma (MPM) is rising. Our aim was to present our experience with this entity in order to increase the awareness about this disease to avoid misdiagnosis.

METHODS

Records of seven patients with histologically confirmed MPM were retrospectively reviewed. Demographic and clinicopathological findings were studied in detail.

RESULTS

There were two females and 5 males; mean age was 50.3 years (range 16-73). Asbestos exposure was recorded in two patients, familial Mediterranean fever in one and previous radiation in one. Main presentations were abdominal pain and distension. None of the patients was diagnosed preoperatively. The average delay in diagnosis was 10 months. Calretinin expression was identified in all tumors. Three patients were treated with cytoreductive surgery combined with systemic chemotherapy. Two patients who remain alive were young female patients who were diagnosed by laparoscopic incidental findings and were treated with cytoreductive surgery combined with hyperthermic intraoperative intraperitoneal chemotherapy (HIIC). Median survival was 19.7 months. The average survival time of the five patients who died of their diseases was 10.2 months.

CONCLUSIONS

An awareness of MPM is important to prevent misdiagnosis. Immunohistochemistry has an important role in confirming the diagnosis. MPM remains a difficult therapeutic challenge. Thorough cytoreductive surgery is the cornerstone of current treatment while HIIC is a promising strategy in suitable patients.

Peritoneal Dialysis in the 21st Century: The Potential of Gene Therapy

ABSTRACT. One of the greatest biotechnologic advances of the last 25 yr is genetic engineering—the ability to identify and isolate individual genes and transfer genetic elements between cells. Genetic engineering forms the basis of a unique biotechnology platform called gene therapy: an approach to treating disease through genetic manipulation. It is becoming clear that during peritoneal dialysis, the peritoneal membrane undergoes various structural and functional changes that compromise the dialyzing efficiency of the membrane and eventually lead to membrane failure. A gene therapy strategy based on genetic modification of the peritoneal membrane could improve the practice of peritoneal dialysis through the production of proteins that would be of therapeutic value in preventing membrane damage and preserving its dialyzing capacity. The peritoneal membrane can be genetically modified by either ex vivo or in vivo gene transfer strategies with a variety of potentially therapeutic genes, including those for anti-inflammatory cytokines, fibrinolytic factors, and antifibrotic molecules. These genes could be administered either on an acute basis, such as in response to peritonitis, or on an intermittent basis to maintain physiologic homeostasis and perhaps to prevent the adverse changes in the membrane that occur over time. The anticipated effect of a gene therapy strategy could be measured in maintenance of desired transport characteristics and in patients being able to remain on the therapy for longer periods of time without the negative outcomes. In summary, the use of a gene therapy strategy to enhance peritoneal dialysis is an innovative and exciting concept with the potential to provide new treatment platforms for patients with end-stage renal disease.

Nonviral gene transfer into primary cultures of human and porcine mesothelial cells

Due to their abundance and accessibility, mesothelial cells may be suitable tools for recombinant reagent expression by gene transfer. Genetically modified porcine mesothelial cells (PMCs) may have the potential for the treatment of vascular diseases in humans. We studied the effect of various transfection reagents on the primary culture of PMCs and human mesothelial cells (HMCs). The cells were transfected with a plasmid encoding a reporter gene (luciferase or green fluorescent protein [GFP]) under the control of the cytomegalovirus promoter. Transfection was achieved using cationic lipids (DOSPER and DOTAP) or calcium phosphate/deoxyribonucleic acid coprecipitation or Fugene 6. Results showed that Fugene 6 was the most efficient and reproducible transfection reagent with both PMCs and HMCs. With Fugene 6, luciferase activity in PMCs (1.5 x 10(8) relative light units [RLU]/10(6) cells) was at least 2.5-fold higher than with the other transfection reagents, and it was 100-fold higher than in HMCs. However, the proportion of transfected cells expressing GFP was only 1%. These preliminary findings open up new avenues for developing experimental studies on the use of genetically modified PMCs.

Adenovirus-mediated transfer of the 39 kD receptor-associated protein increases fibrinolytic capacity

BACKGROUND

The mesothelium has an important role in maintaining an adequate fibrinolytic capacity in the peritoneal cavity and thus in preventing the formation of fibrinous peritoneal adhesions by secreting the fibrinolytic enzyme tissue-type plasminogen activator (t-PA). The fibrinolytic activity of human mesothelial cells (HMCs) is counteracted by rapid uptake of t-PA via the low-density lipoprotein receptor-related protein (LRP). The 39 kD receptor-associated protein (RAP) is an inhibitor of binding of t-PA to LRP, but RAP itself is also rapidly degraded via LRP.

METHODS

Adenovirus-mediated RAP gene transfer technology was used to evaluate the effect of prolonged overexpression of RAP on t-PA accumulation in conditioned medium of HMCs under basal and inflammatory conditions.

RESULTS

Infection of HMCs with a recombinant adenovirus carrying the RAP cDNA resulted within one day in t-PA levels that were maximally twofold to threefold increased as compared with noninfected or adenovirus-beta-galactosidase-infected cells. Whereas upon prolonged incubation, t-PA levels in the conditioned medium of uninfected cells leveled off because of rapid uptake and degradation via LRP, t-PA concentrations in the medium of adenovirus-RAP-infected cells continued to increase, reaching fivefold control levels after 72 hours. The increased t-PA accumulation persisted for seven days and then slowly returned to control values over the next few weeks. In contrast, the production of a specific inhibitor of t-PA, plasminogen activator inhibitor-1 (PAI-1), was not affected by adenoviral RAP gene transfer. Northern blotting analysis showed that t-PA, PAI-1, and LRP mRNA concentrations were not changed after adenoviral infection, underlining that the elevated t-PA levels are the result of RAP-blocked uptake and degradation of t-PA rather than increased t-PA synthesis. RAP gene transfer also restored diminished fibrinolytic activity of cytokine-treated mesothelial cells.

CONCLUSIONS

Adenovirus-mediated transfer of the RAP gene provides an efficient way of transiently increasing the fibrinolytic capacity of mesothelial cells.

Future developments in the treatment of end-stage renal disease: a North American perspective

New technology for the treatment of end-stage renal disease will need to be pharmacoeconomically persuasive in reducing the life-cost of treatment to obtain entry into the market. Increased automation, with closed-loop sensing technology, will occur in the near term. Clearance-based terminology for quantifying performance of equipment will give way to direct quantification of toxin removal. Experiments on the frequency and duration of treatment will redefine what is considered to be adequate therapy in terms other than simple urea removal. Near-term changes in current vascular access technology will be driven by the current cost of access failure. Automated peritoneal dialysis will displace continuous ambulatory peritoneal dialysis, and online compounding of solution for use is likely for both hemodialysis and peritoneal dialysis. In a longer time frame these technologies will merge. Xenografting from the pig will be a reality, and gene therapy of the mesothelium will provide a more user-friendly therapy for end-stage renal disease.