Mesothelial toxicity of peritoneal dialysis fluids is related primarily to glucose degradation products, not to glucose per se.

OBJECTIVES: High concentrations of glucose and/or formation of glucose degradation products (GDPs) during heat sterilization of peritoneal dialysis fluids (PDFs) are believed to be key factors in the limited biocompatibility of PDFs. We have previously shown that several identified GDPs can specifically impair human peritoneal mesothelial cell (HPMC) function. In the present study we aimed at differentiating the respective roles of glucose and GDPs in the toxicity of PDF to mesothelial cells. METHODS: HPMCs were acutely pre-exposed to or incubated chronically in the presence of pH-neutral PDF sterilized by either heat (H-PDF) or filtration (F-PDF). In addition, HPMCs were treated with commercially available H-PDF manufactured either conventionally, that is, in single-chamber containers, or using novel dual-chamber bags that help to substantially decrease GDP formation. Functional assessment of HPMCs included viability, release of interleukin (IL)-6, and proliferation. RESULTS: Viability and release of IL-6 from HPMCs pretreated with H-PDF (pH 7.3) for 1 to 4 hours were significantly reduced compared to cells exposed to corresponding F-PDF. Incubation in medium mixed (1:1) with H-PDF considerably impaired growth of HPMCs, and over a period of 10 days gradually decreased both the viability of HPMCs and their ability to generate IL-6. These effects were either absent from or significantly less in HPMCs exposed to F-PDF. Similar differences were observed when commercial GDP-containing H-PDFs were compared with newly designed H-PDFs free of GDPs. CONCLUSIONS: Impaired viability and function of HPMCs exposed to glucose-containing pH-neutral PDF is related predominantly to the presence of GDP and, to a significantly lesser extent, to the presence of glucose per se. Prevention of GDP formation during autoclaving markedly improves the biocompatibility of H-PDF with HPMCs.     

Renal toxicity mediated by glucose degradation products in a rat model of advanced renal failure

Background In peritoneal dialysis (PD) residual renal function contributes to improved patient survival and quality of life. Glucose degradation products (GDP) generated by heat sterilization of PD fluids do not only impair the peritoneal membrane, but also appear in the systemic circulation with the potential for organ toxicity. Here we show that in a rat model of advanced renal failure, GDP affect the structure and function of the remnant kidney. Materials and methods Sprague‐Dawley rats were randomly assigned to a two stage subtotal nephrectomy (SNX) or sham operation and were left untreated for 3 weeks. The SNX + GDP group continuously received chemically defined GDP intravenously for 4 weeks; the SNX and the sham‐operated rats remained without GDP. The complete follow‐up for all groups was 7 weeks postoperatively. We analysed renal damage using urinary albumin excretion as well as a semiquantitative score for glomerulosclerosis and tubulointerstitial damage, as well as for immunohistochemical analyses. Results The SNX + GDP rats developed significantly more albuminuria and showed a significantly higher score of glomerulosclerosis index (GSI) and tubulointerstitial damage index (TII) as compared to SNX or control rats. In the SNX + GDP group the expression of carboxymethyllysine and methylglyoxal was significantly higher in the tubulointerstitium and the glomeruli compared to the SNX rats. Caspase 3 staining and TUNEL assay were more pronounced in the tubulointerstitium and the glomeruli of the SNX + GDP group. In SNX + GDP animals, the expression of the slit diaphragm protein nephrin, was significantly lower compared to SNX or control animals. Conclusion In summary, our data suggests that GDP can significantly advance chronic kidney disease and argues that PD solutions containing high GDP might deteriorate residual renal function in PD.     

How to avoid glucose degradation products in peritoneal dialysis fluids.

OBJECTIVE: The formation of glucose degradation products (GDPs) during sterilization of peritoneal dialysis fluids (PDFs) is one of the most important aspects of biocompatibility of glucose-containing PDFs. Producers of PDFs are thus trying to minimize the level of GDPs in their products. 3,4-Dideoxyglucosone-3-ene (3,4-DGE) has been identified as the most bioreactive GDP in PDFs. It exists in a temperature-dependent equilibrium with a pool of 3-deoxyglucosone (3-DG) and is a precursor in the irreversible formation of 5-hydroxymethyl furaldehyde (5-HMF).The aim of the present study was to investigate how to minimize GDPs in PDFs and how different manufacturers have succeeded in doing so. DESIGN: Glucose solutions at different pHs and concentrations were heat sterilized and 3-DG, 3,4-DGE, 5-HMF, formaldehyde, and acetaldehyde were analyzed. Conventional as well as biocompatible fluids from different manufacturers were analyzed in parallel for GDP concentrations. RESULTS: The concentrations of 3-DG and 3,4-DGE produced during heat sterilization decreased when pH was reduced to about 2. Concentration of 5-HMF decreased when pH was reduced to 2.6. After further decrease to a pH of 2.0, concentration of 5-HMF increased slightly, and below a pH of 2.0 it increased considerably, together with formaldehyde; 3-DG continued to drop and 3,4-DGE remained constant. Inhibition of cell growth was paralleled by 3,4-DGE concentration at pH 2.0 - 6.0. A high glucose concentration lowered concentrations of 3,4-DGE and 3-DG at pH 5.5 and of 5-HMF at pH 1. At pH 2.2 and 3.2, glucose concentration had a minor effect on the formation of GDPs. All conventional PDFs contained high levels of 3,4-DGE and 3-DG. Concentrations were considerably lower in the biocompatible fluids. However, the concentration of 5-H M F was slightly higher in all the biocompatible fluids. CONCLUSION: The best way to avoid reactive GDPs is to have a pH between 2.0 and 2.6 during sterilization. If pHs outside this range are used, it becomes more important to have high glucose concentration during the sterilization process. There are large variations in GDPs, both within and between biocompatible and conventionally manufactured PDFs.     

Six bioabsorbable polymers: in vitro acute toxicity of accumulated degradation products.

Bioabsorbable polymer implants may provide a viable alternative to metal implants for internal fracture fixation. One of the potential difficulties with absorbable implants is the possible toxicity of the polymeric degradation products especially if they accumulate and become concentrated. Accordingly, material evaluation must involve dose-response toxicity data as well as mechanical properties and degradation rates. In this study the toxicity and rates of degradation for six polymers were determined, along with the toxicity of their degradation product components. The polymers studied were poly(glycolic acid) (PGA), two samples of poly(L-lactic acid) (PLA) having different molecular weights, poly(ortho ester) (POE), poly(epsilon-caprolactone) (PCL), and poly(hydroxy butyrate valerate) (5% valerate) (PHBV). Polymeric specimens were incubated at 37 degrees C in 0.05 M Tris buffer (pH 7.4 at 37 degrees C) and sterile deionized water. The solutions were not changed during the incubation intervals, providing a worst-case model of the effects of accumulation of degradation products. The pH and acute toxicity of the incubation solutions and the mass loss and logarithmic viscosity number of the polymer samples were measured at 10 days, 4, 8, 12, and 16 weeks. Toxicity was measured using a bioluminescent bacteria, acute toxicity assay system. The acute toxicity of pure PGA, PLA, POE, and PCL degradation product components was also determined. Degradation products for PHBV were not tested. PGA incubation solutions were toxic at 10 days and at all following intervals. The lower molecular weight PLA incubation solutions were not toxic in buffer but were toxic by 4 weeks in water.(ABSTRACT TRUNCATED AT 250 WORDS)     

Single exposure of mesothelial cells to glucose degradation products (GDPs) yields early advanced glycation end-products (AGEs) and a proinflammatory response.

BACKGROUND: Fluids commonly used for peritoneal dialysis (PD) have a low pH and a high glucose content. Furthermore, heat sterilization of dialysis fluids degrades some of the glucose into glucose degradation products (GDPs), such as methylglyoxal (MGO) and 3-deoxyglucosone (3-DG). Mesothelial cells (MCs) form the first line in the peritoneal cavity and are constantly exposed to these nonphysiological conditions. Since MCs play an important role in the regulation of inflammatory responses in the peritoneal cavity, we studied the kinetics of MC uptake of highly purified GDP species, along with their effect on various cellular biological and immunological parameters. METHODS: Methylglyoxal and 3-DG were purified and added to MC cultures. Complexing to medium components or uptake by MCs was analyzed over time by HPLC of the culture supernatant and by immunocytochemistry of MCs for MGO-modified proteins. Furthermore, MCs were exposed to a single dose of MGO or 3-DG and analyzed for apoptosis, proliferation by MTT assay, and [3H]-thymidine incorporation. Incorporation of [35S]-methionine was determined in order to analyze de novo protein synthesis. Expression of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1), CD44, and vascular cell adhesion molecule-1 (VCAM-1) was analyzed by cell-bound ELISA. Effects of MGO and 3-DG on cytokine production were also analyzed. RESULTS: Substitution of MGO and 3-DG in culture medium resulted in a spontaneous decrease in MGO over time, whereas 3-DG levels decreased minimally. The concentration of these GDPs was more reduced in the presence of MCs, indicating binding to and/or uptake by MCs of these GDPs. Mesothelial cells that had been cultured in the presence of MGO showed positive staining with a monoclonal that specifically recognizes MGO-modified proteins, demonstrating complexing to mesothelial cellular proteins. Cell-bound ELISA showed a two- to three-fold induction of expression of VCAM-1 by MGO and 3-DG; the expression of ICAM-1 and CD44 was not changed. Mesothelial cells showed a twofold increase in interleukin (IL)-6 and IL-8 production after exposure to 3-DG. Furthermore, incubation with MGO and 3-DG induced apoptosis and reduced the proliferation of cells, but did not influence protein synthesis. CONCLUSIONS: In the current report we demonstrate that MCs take up MGO and 3-DG and form early advanced glycation end-products. Upon short exposure to a single GDP, MCs react with enhanced cytotoxic damage and a proinflammatory response, evidenced by increased VCAM-1 expression and elevated production of IL-6 and IL-8.     

Evidence for less irritation to the peritoneal membrane in rats dialyzed with solutions low in glucose degradation products.

BACKGROUND: Acidic pH and the presence of glucose degradation products (GDP) are believed to compromise the biocompatibility of peritoneal dialysis fluids (PDF).The present study examines the effects of long-term exposure to GDP and low pH by comparing conventional PDF and a new, neutral pH, low GDP solution. METHODS: All experiments were performed using a chronic infusion model of dialysis in nonuremic rats. The animals were treated for 6 weeks with 2 daily injections of 4.25% glucose-containing PDF.The following PDF were tested: CAPD3 (single-chamber bag, low pH, high GDP), CAPD3 pH 7.4 (single-chamber bag, neutral pH, high GDP), CAPD3-Balance (double-chamber bag, neutral pH, low GDP). All test solutions were obtained from Fresenius Medical Care, Bad Homburg, Germany. RESULTS: After 6 weeks of exposure, peritoneal permeability to water, urea, creatinine, glucose, and sodium, assessed by peritoneal equilibration test, was similar in all groups. However, compared to other PDF, dialysis with CAPD3-Balance was associated with reduced concentrations of protein and hyaluronan in the dialysate, decreased peritoneal eosinophilia, and reduced dialysate levels of chemokines CCL2/MCP-1 and CCL5/RANTES. Morphologic changes in the peritoneal membrane of CAPD3-Balance-treated animals were much less pronounced and included reduced vascular density, preservation of the mesothelial monolayer and intercellular junction, and no reduplication of the submesothelial basement membrane. CONCLUSIONS: A new generation of PDF with physiologic pH and low GDP level produce less irritation to the peritoneal membrane and better preserve its structural integrity. This effect seems to be related predominantly to minimized GDP concentrations.     

Effect of glucose degradation products on the peritoneal membrane in a chronic inflammatory infusion model of peritoneal dialysis in the rat.

BACKGROUND: Long-term use of the peritoneal membrane as a dialyzing membrane is hampered by its eventual deterioration. One of the contributing factors is glucose degradation products (GDPs) in the dialysis solution. In this study, we evaluated the effect of a low GDP solution on peritoneal permeability, the structural stability of the peritoneal membrane, and vascular endothelial growth factor (VEGF) production in a chronic inflammatory infusion model of peritoneal dialysis (PD) in the rat. METHODS: Male Sprague-Dawley rats were divided into 3 groups: a conventional solution group (group C, n = 12), a test solution group (group T, n = 12), and a normal control group (group NC, n = 8). Group T rats were infused with low GDP solution (2.3% glucose solution with two compartments), and group C rats with conventional dialysis solution (2.3% glucose solution), adjusted to pH 7.0 before each exchange. Animals were infused through a permanent catheter with 25 mL of dialysis solution. In both groups, peritoneal inflammation was induced by infusing dialysis solution supplemented with lipopolysaccharide on days 8, 9, and 10 after starting dialysate infusion. Peritoneal membrane function was assessed before and 6 weeks after initiating dialysis using the 1-hour peritoneal equilibration test (PET) employing 4.25% glucose solution. Both VEGF and transforming growth factor beta1 (TGFbeta1) in the dialysate effluent were measured by ELISA. The number of vessels in the omentum was counted after staining with anti-von Willebrand factor, and the thickness of submesothelial matrix of the trichrome-stained parietal peritoneum was measured. Peritoneal tissue was analyzed for VEGF protein using immunohistochemistry. RESULTS: At the end of 6 weeks, the rate of glucose transport (D/D0, where D is glucose concentration in the dialysate and D0 is glucose concentration in the dialysis solution before it is infused into the peritoneal cavity) was higher in group T (p < 0.05) than in group C. Dialysate-to-plasma ratio (D/P) of protein was lower in group T (p < 0.05) than in group C; D/P(urea), D/P(sodium), and drain volumes did not differ significantly between groups C and T. Dialysate VEGF and TGFbeta levels were lower in group T (p < 0.05) than in group C. Immunohistochemical studies also revealed less VEGF in the peritoneal membranes of group T. There were significantly more peritoneal blood vessels in group C (p < 0.05) than in group T, but the thickness of submesothelial matrix of the parietal peritoneum was not different between the two groups. The VEGF levels in the dialysate effluent correlated positively with the number of blood vessels per field (r = 0.622, p < 0.005). CONCLUSION: Using a chronic inflammatory infusion model of PD in the rat, we show that dialysis with GDP-containing PD fluid is associated with increased VEGF production and peritoneal vascularization. Use of low GDP solutions may therefore be beneficial in maintaining the function and structure of the peritoneal membrane during long-term PD.     

葡萄糖降解产物对内皮细胞AQP1及eNOS表达影响研究

目的研究腹膜透析液毒性成份之一-葡萄糖降解产物（GDPs）对内皮细胞水孔蛋白1（AQP1）及eNOS表达影响。方法选用两种相关的GDPs-2-糠醛（Fur）及甲基乙二醛（MGly）,采用与传统腹膜透析液浓度相当的GDPs刺激内皮细胞系tEnd.124h（Fur 0.8 uM;MGly 35 uM）,以培养液DMEM作为对照组,研究GDPs对内皮细胞AQP1及eNOS表达影响。并进一步通过时间依赖性及浓度依赖性分析研究GDPs对AQP1 mRNA表达影响。使用RT-PCR检测AQP1及eNOS基因表达。使用Western blot检测AQP1蛋白表达。结果内皮细胞系tEnd.1经GDPs（Fur 0.8 uM;MGly 35 uM）刺激24h后,Fur及MGly显著上调内皮细胞eNOS mRNA表达（P〈0.05）。GDPs对AQP1 mRNA表达有降低的趋势但无统计学意义。时间依赖性及浓度依赖性研究同样提示GDPs对AQP1 mRNA表达有下降的趋势。蛋白质印迹分析（Western blot）检测有相似的结果。结论GDPs促进内皮细胞eNOS的表达但并不促进AQP1的表达,GDPs的这种作用可能参与长期腹膜透析过程中腹膜血管新生及超滤衰竭的发生。     

The role of in vitro diagnostic companies in reducing laboratory error.

Laboratory errors have a significant impact on patient safety. The manufacturers of in vitro diagnostic (IVD) products play an important role in the reduction of laboratory errors by ensuring the highest possible safety and efficacy of their products. In order to achieve this, the IVD industry has implemented rigorous product development and manufacturing processes. Many IVD companies apply Six Sigma principles in order to minimize variability within the whole product life cycle, starting with customer requirements, through product design and manufacture, as well as management of the potential issues that occur after the products have been released for use. A closer look into this process is presented here, using an evacuated blood collection tube as a model device.     

Metabolic alterations in the human erythrocyte produced by increases in glucose concentration: The role of the polyol pathway

Human erythrocytes incubated in medium containing 50 mM glucose have increased intracellular sorbitol and fructose concentrations as compared with samples incubated with 5 mM glucose. Increased medium glucose concentration did not significantly alter total glucose consumption or lactate production. However, the intracellular lactate:pyruvate ratio rose, the concentrations of fructose diphosphate, and triose phosphates increased, and the 2,3-diphosphoglycerate concentration fell. [(14)C]O(2) production from glucose-1-(14)C also increased with increased medium glucose concentration. These changes are believed to reflect changes in the redox states of the diphosphopyridine nucleotide/reduced form of diphosphopyridine nucleotide (NAD/NADH) and nicotinamide-adenine dinucleotide phosphate/reduced form of nicotinamide-adenine dinucleotide phosphate (NADP/NADPH) couples resulting from increased activity of the polyol pathway. Addition of pyruvate to the incubation media prevented these changes. These studies illustrate that an increase in the red cell's normal substrate, glucose, can produce changes in red cell metabolism.     

Glucose degradation products in peritoneal dialysis fluids may have both local and systemic effects: a study of residual fluid and mesothelial cells.

OBJECTIVE: When peritoneal dialysis (PD) fluids are heat sterilized, glucose is degraded to carbonyl compounds. These compounds are known to interfere with many cellular functions and to promote the formation of advanced glycation end-products. However, little is known about what actually happens with glucose degradation products (GDPs) after infusion into the peritoneal cavity. The aim of the present study was to investigate possible targets for GDPs in the peritoneal cavity. DESIGN: In vitro reactions between residual fluid and GDPs were studied by incubating unused PD fluid with overnight dialysate. Confluent monolayer cultures of human mesothelial cells were used as a model to study the reactions of GDPs with the cells lining the peritoneal cavity. METHODS: Samples were analyzed, using high pressure liquid chromatography, for the presence of formaldehyde, acetaldehyde, 5-hydroxymethyl-2-furaldehyde (5-HMF), methylglyoxal, and 3-deoxyglucosone (3-DG). Cytotoxicity was determined as inhibition of proliferation of cultured fibroblasts. RESULTS: None of the analyzed GDPs reacted with overnight dialysate. Formaldehyde and methylglyoxal, in contrast to 3-DG and 5-HMF, reacted with the cultured mesothelial cells. CONCLUSIONS: Low molecular weight carbonyls such as formaldehyde and methylglyoxal most probably react with the mesothelial cells lining the peritoneal cavity, and could be responsible for the disappearance of these cells during long-term treatment. 3-Deoxyglucosone showed remarkably low reactivity and was most probably transported within the patient.     

The role of nurses in reducing the use of tobacco

Smoking is a major cause of morbidity and mortality in the UK, and the government has funded a range of local and national smoking cessation initiatives. Supporting people as they attempt to give up smoking requires specialist skills and knowledge, often provided by nurses who have received appropriate training. However, non-specialist nurses can also play a role in cutting smoking rates by encouraging patients to consider giving up and directing them towards specialist services. This article focuses on the role that hospital-based nurses can play in encouraging patients to give up smoking.     

肝素在高糖影响大鼠腹膜间皮细胞的增殖及其表达白细胞介素-1中的作用

目的 初步观察肝素在高糖影响大鼠腹膜间皮细胞(Rat pcritoneal mesothelial cells，BPMC)细胞增殖及其表达白细胞介素—1(Interleukin-1,IL-1)中的作用，从而为持续性非卧床腹膜透析(Continuous ambulatory pcritoncal dialysis，CAPD)中肝素的临床应用打下一定的理论基础。方法 建立BPMC的体外培养；并用四四氮唑蓝(MTT)细胞增殖实验和酶联免疫吸附方法(ELISA)，来分析肝素对高糖(3．86％葡萄糖)影响RPMC增殖及其分泌IL—1的作用。结果 3．86％葡萄糖能显抑制BPMC的增殖，而1．25U／ml肝素能部分逆转高糖对RPMC增殖的抑制作用(P＜0．01)；3．86％葡萄糖能显增加BPMC表达IL—1β，而1．25U／ml肝素能部分减少高糖增加BPMC表达IL-1β的作用(P＜0．01)。结论 本结果提示，肝素可能通过逆转高糖对BPMC的增殖抑制作用及减少高糖增加RPMC表达促炎细胞因子IL—1的作用，而延续CAPD相关性腹膜纤维化的发生，最终有益于CAPD进行。     

A study of the clinical and biochemical profile of peritoneal dialysis fluid low in glucose degradation products

♦ Objective: Although peritoneal dialysis (PD) is a widely accepted form of renal replacement therapy, concerns remain regarding the bioincompatible nature of standard PD fluid (PDF). Short-term studies of new biocompatible PDFs low in glucose degradation products (GDPs) reveal divergent results with respect to peritoneal integrity.♦ Methods: We studied 125 patients on maintenance PD who were assigned, by simple randomization, to receive either conventional or low-GDP PDF at PD initiation. Parameters of dialysis adequacy and peritoneal transport of small solutes were determined at initiation and after a period of maintenance PD at the time when serum and overnight effluent dialysate were simultaneously collected and assayed for various cytokines, chemokines, adipokines, and cardiac biomarkers. All patients were further followed prospectively for an average of 15 months from the day of serum and effluent collection to determine patient survival and cardiovascular events.♦ Results: Patients treated with conventional or low-GDP PDF were matched for sex, age, duration of dialysis, dialysis adequacy, and incidence of cardiovascular disease or diabetes. After an average of 2.3 years of PD treatment, the weekly total and peritoneal creatinine clearance, and the total and peritoneal Kt/V were comparable in the groups. However, urine output was higher in patients using low-GDP PDF despite there having been no difference between the groups at PD initiation. Patients using low-GDP PDF also experienced a slower rate of decline of residual glomerular filtration and urine output than did patients on conventional PDF. Compared with serum concentrations, effluent concentrations of tumor necrosis factor α, hepatocyte growth factor, macrophage migration inhibitory factor, interleukins 8 and 6, C-reactive protein, and leptin were found to be higher in both groups of patients after long-term PD, suggesting that the peritoneal cavity was the major source of those mediators. Compared with patients on low-GDP PDF, patients on conventional fluid showed elevated leptin and reduced adiponectin levels in serum and effluent. The effluent concentration of interleukin 8 was significantly lower in patients using low-GDP PDF. The survival rate and incidence of cardiovascular complications did not differ between these groups after maintenance PD for an average of 3.6 years.♦ Conclusions: It appears that low-GDP PDF results in an improvement of local peritoneal homeostasis through a reduction of chronic inflammatory status in the peritoneum.