Re: effects of low-glucose degradation product solution on peritoneal membrane characteristics in peritoneal dialysis patients: a 3-year follow-up study.

Dear Editor, In the past issue of the Iranian Journal Kidney Disease, Park and colleagues compared the standard peritoneal dialysis (PD) solution to the low glucose degradation products (GDP) solution in a 3-year follow-up.1 Peritoneal dialysis (PD) is an effective and established form of renal replacement therapy in end -stage renal disease over the past 30 years, which is used by approximately 11% of the total global dialysis population. Although PD has improved the quality of life in these patients, several studies have shown inferior PD patients survival compared to hemodialysis patients. Peritonitis and physiologic dysfunction of the peritoneal membrane are major cause of peritoneal failure.2 Thus, a major disadvantage of this treatment is PD solution bioincompatibilty. Peritoneal dialysis solutions contain elevated concentration of glucose to provide the osmotic drive, lactate buffer to correct metabolic acidosis, and low pH to prevent glucose caramelization during heat sterilization, but heat sterilization of PD solutions can lead to glucose degradation products. High glucose concentrations in conventional PD solutions have direct cytotoxicity, stimulation of inflammatory cytokine production, and promotion of formation of advanced glycation end products, which provoke peritoneal inflammation and injury in mesothelial cells, resulting in structural changes in the peritoneal membrane and progressive loss of peritoneal function.3 Glucose degradation productsinduced mesothelial cell injury and apoptosis lead to interacellular hydrogen peroxide production and free radical formation, which is important for peritoneal membrane inflammation and injury. In particular, experimental and clinical exposure to conventional PD solution leads to significant histopathological changes over time, including loss of the surface mesothelial cell layer, thickening of the submesothelial, and progressive vasculopathy.4 Glucose degradation products directly produce the profibrotic cytokine transforming growth factor-β and stimulate vascular endothelial growth factor synthesis. These two signals have a key role in the progression of peritoneal membrane fibrosis and vascular proliferation in long-term PD patients. There are several formulations for PD solution, including conventional, physioneal, gambrosol Trio, Balance, and Bicavera. The conventional solution is 1 chamber with lactate buffer and the final pH of 5 to 5.4. The physioneal is associated with 2 chambers, lactate and bicarbonate buffer and the final pH of 7.3. The Gambrosol Trio includes 3 chambers, lactate buffer, and the final pH of 6.5. The Bicavera is similar to the physioneal with 2 chambers, but bicarbonate buffer and the final pH of 7.1, and finally, balance solution is associated with 2 chambers, lactate buffer, and the final pH of 6.8. The use of a multibag system allows for separation into compartments; a low pH glucose compartment, which minimizes the production of GDPs during heat sterilization and storage and a buffer compartment which can be a bicarbonate and lactate mixture or bicarbonate alone. Several investigations have been done for reducing GDP and improving the biocompatibility of PD solutions. For example, Wieslander and colleagues showed that the separation of the glucose and lactate buffer during storage or heat sterilization reduced GDP formation.5 In addition, Erixon and coworkers suggested that sterilization of glucose at a low pH between 2 and 2.6 reduced cytotoxic GDP.6 To improve biocompatibility, new PD solutions with neutral pH, low GDP, and low glucose concentration have been generated in recent years. Lee and colleagues, in a large retrospective