Hemodialysis (HD) is the most frequently used treatment for end-stage renal disease. Despite all efforts to improve the outcomes, the mortality of patients on HD is still high, and this especially is related to cardiovascular diseases (CVD). Glucose degradation products accumulate in plasma and tissue as a result of oxidative stress in these patients. Such accumulation is strongly related to the risk of developing CVD. Tissue deposits of advanced glycation end products (AGE) can be easily assessed by a skin autofluorescence (SAF) technique. SAF is one of the strongest prognostic markers of mortality in HD patients. The aim of this thesis is to examine whether intervention on HD treatment can reduce the load of AGE of these patients. The aim of the first study was to investigate whether changes in SAF appear after a single HD session and if they might be related to changes in plasma AF. Skin and plasma AF (PAF) were measured before and after HD in 35 patients on maintenance HD therapy. Median dialysis time was 4 h (range 3-5.5). SAF was measured noninvasively with an AGE Reader, and plasma AF was measured before and after HD. The HD patients had on average a 65% higher SAF value than age-matched healthy persons (P < 0.001). PAF was reduced by 14% (P < 0.001), whereas SAF was not changed after a single HD treatment. No significant influence of the reduced PAF on SAF levels was found. This suggests that the measurement of SAF can be performed during the whole dialysis period and is not directly influenced by the changes in plasma AF during HD. In study 2 different dialysis filters were compared to clarify whether using a high-flux (HF) dialyzer favors plasma or SAF removal compared to low-flux (LF) dialyzer. Twenty-eight patients were treated with either an HF-HD or LF-HD but otherwise unchanged conditions in a cross-over design. SAF was measured non-invasively with an AGE reader before and after HD. PAF was determined as total and non-protein-bound fractions. Corrections for hemoconcentrations by volume changes were made using the change in serum albumin. Paired and non-paired statistical analyses were used. The different treatments did not change SAF after LF- and HF-dialysis. Total, free, and protein-bound PAF were reduced after a single LF-HD by 21%, 28%, and 17%, respectively (P<.001). After HF-HD total and free PAF was reduced by 5% and 15%, respectively (P<.001), while protein-bound values were unchanged. The LF-HD resulted in a more pronounced reduction of PAF than did HF-HD (P<.001). Serum albumin correlated inversely with PAF in HF-HD. There was no significant change in SAF after dialysis, either with LF or with HF dialysis. Although only limited reductions in PAF were observed, these were more pronounced when performing LF dialysis. These data are not in overwhelming support of the use of HF dialysis in the setting used in this study. In the third study the effect on SAF was investigated using either glucose-containing or glucose-free dialysate. SAF and PAF were measured in patients on HD during standard treatment with a glucose-containing dialysate (n=24). After that, the patients were switched to a glucose-free dialysate for a 2 week period, and new measurements were performed on PAF and SAF. There was an increase of pre-dialysis SAF measured at the beginning of the study compared with the values one month later (as in study 4). By comparing pre- and post-dialysis values there was a significant decrease of SAF only when using glucose-free dialysate. Free PAF decreased independently whether glucose-containing or glucose-free dialysate was used. The important finding was that increase in SAF seemed possible to slow down using glucose-free dialysate. Study 4 was performed to investigate whether there are seasonal variations in SAF on a HD population. SAF was measured non-invasively with an AGE Reader in patients on HD at different seasonal periods during one year such as February-May (N=31), May–August (N=28), August–March (N=25). SAF was measured before HD. Paired statistical analyses were performed between each two periods.  Unexpectedly there was at a median 6% increase in SAF during the winter (p=0.004) and a 11% decrease from 4.0 to 3.5 arbitrary units of the SAF during the summer (p<0.001). The study concluded that SAF shows seasonal variation. The cause of these changes could not be clarified. A beneficial effect may be due to extended exposure to sunlight during the summer and/or to different dietary intakes during the seasons. In conclusion, these interventional studies confirmed that PAF is lowered by dialysis. SAF was only decreased by HD when using glucose-free dialysate. SAF was not influenced by a single HD, with glucose-containing dialysate, independent of using HF or LF filters. These data favor glucose-free dialysate as a possible measure to slow down the progress of tissue AGE compared to glucose-containing dialysate. Longitudinal studies will help to clarify this issue further.

Konventionelle hitzesterilisierte, glukosehaltige Peritonealdialyselösungen (PDL) sind aufgrund ihres niedrigen pH-Wertes, ihrer hohen Glukosekonzentration und Osmolalität und ihres Gehaltes an Glukosedegradationsprodukten (GDP) bioinkompatibel. Alternativen zu glukosehaltigen PDL stellen aminosäuren- oder icodextrinhaltige PDL dar. Daneben enthalten auch neuere Glukose-PDL in Doppelkammersystemen aufgrund der Sterilisation von Glukose bei sehr niedrigem pH nur noch sehr geringe GDP-Konzentrationen. In dieser Arbeit wurden die akuten und chronischen Wirkungen verschiedener PDL auf humane peritoneale Mesothelzellen (HPMC) untersucht. Konfluente HPMC wurden mit den zu testenden PDL (glukosehaltige hitze- versus filtersterilisierte und konventionelle versus Doppelkammer-Glukose-PDL, 1% Aminosäuren-PDL und Icodextrin - alle bei neutralem pH-Wert) akut (1-4 Stunden Präinkubation) bzw. chronisch (bis zu 10 Tage) inkubiert. Die Zellvitalität (MTT-Assay) und IL-1beta-stimulierte Sekretion von IL-6 (Zellfunktion) wurden untersucht. Die akute und chronische Exposition von HPMC gegenüber hitzesteriliserten Peritonealdialyselösungen führte zu einer signifkanten Reduktion von Vitalität und Funktion der Zellen. Demgegenüber führte die Inkubation mit filtersteriliserten PDL und GDP-armen PDL zu einer weniger starken Beeinflussung von Vitalität und Funktion. Die aminosäurenhaltige PDL beeinflusste weder akut noch chronisch die Vitalität bzw. Funktion der Zellen negativ. Hingegen unterschied sich die icodextrinhaltige Lösung nicht wesentlich von der hitzesteriliserten PDL mit hohem Glukoseanteil. Die Verringerung des Gehaltes an GDP in PDL mittels Filtersterilisation bzw. alternativer Sterilisation in Zweikammerbeuteln hat einen positiven Einfluss auf Vitalität und Funktion von HPMC in vitro. Der Ersatz des osmotischen Agenz hingegen bedeutet nicht zwansgläufig eine bessere Biokompatibilität. / Conventional heat-sterilized glucose-containing peritoneal dialysis fluids (PDF) are bioincompatible due to their acidic pH, high glucose concentration and resulting hyperosmolality, and the presence of glucose degradation products (GDP). Alternatives to these solutions are PDL containing amino acids or icodextrin as the osmotic agent. Furthermore, novel glucose-based PDF contain only trace amounts of GDPs due to the sterilisation of glucose at very low pH in a dual-chamber container system. The present study examines the acute and chronic effects of different PDL on human peritoneal mesothelial cells (HPMC). Confluent HPMC were exposed to the different test PDF (glucose containing heat- versus filter-sterilised PDF and conventional versus dual-chambered glucose PDF, 1% amino-acid PDF and icodextrin – all at neutral pH) in an acute (1-4 hours preincubation) and chronic (up to 10 days) cell culture model. Cell viability (MTT assay) and IL-1beta stimulated IL-6 (cell function) release were assessed. Acute and chronic exposure of HPMC to heat-sterilised PDF resulted in a significant reduction of viability and cell function. In contrast, the incubation of filter-sterilised PDF and dual chambered low GDP solution had only minor effects on cell viability and function. Neither viability nor cell function were negatively affected by the amino-acid PDF following acute and chronic exposure. However, incubation with icodextrin resulted in a similar degree of inhibition as compared to incubation with conventional heat-sterilised glucose PDF. In conclusion, removal of GDP from PDF either via filter-sterilisation or manufacture in dual chambered containers helps to conserve viability and function of HPMC in vitro. However, the replacement of the osmotic agent per se does not necessarily result in improved biocompatibility.

Peritoneal dialysis (PD) is a form of renal replacement therapy using the peritoneum as a dialysis membrane. PD solutions employed to remove nitrogen metabolites and excess plasma fluid, and to restore electrolyte and acid-base balance are being developed to minimize local and systemic inflammatory responses while maintaining peritoneal homeostasis and host defense. The effect of chronic action of PD solutions on the peritoneum results in its remodeling and, possibly, eventual loss of peritoneal ultrafiltration capacity. Factors most responsible for late complications and peritoneal remodeling include high glucose levels in PD solutions, and the presence and formation of glucose degradation products (GDP) and advanced glycation end - products (AGEs) in the peritoneal cavity. The aim of our study described in this dissertation was to test various PD solutions with different glucose content and GDP and, using AGEs receptor ligands, to define their systemic effects and identify PD solutions with highest biocompatibility. This part of the dissertation characterizes conventional glucose - based solutions, low - glucose and GDP load solutions as well as glucose polymer (icodextrin) - based PD solutions while determining the plasma and dialysate levels of soluble receptor for AGEs (s - RAGE) and its...

Peritoneal dialysis (PD) is a form of renal replacement therapy using the peritoneum as a dialysis membrane. PD solutions employed to remove nitrogen metabolites and excess plasma fluid, and to restore electrolyte and acid-base balance are being developed to minimize local and systemic inflammatory responses while maintaining peritoneal homeostasis and host defense. The effect of chronic action of PD solutions on the peritoneum results in its remodeling and, possibly, eventual loss of peritoneal ultrafiltration capacity. Factors most responsible for late complications and peritoneal remodeling include high glucose levels in PD solutions, and the presence and formation of glucose degradation products (GDP) and advanced glycation end - products (AGEs) in the peritoneal cavity. The aim of our study described in this dissertation was to test various PD solutions with different glucose content and GDP and, using AGEs receptor ligands, to define their systemic effects and identify PD solutions with highest biocompatibility. This part of the dissertation characterizes conventional glucose - based solutions, low - glucose and GDP load solutions as well as glucose polymer (icodextrin) - based PD solutions while determining the plasma and dialysate levels of soluble receptor for AGEs (s - RAGE) and its...