Pathological role of aminolevulinate in uremic patients.

Previous reports have demonstrated that δ-aminolevulinate (ALA) can promote iron release from horse spleen ferritin under conditions of high serum ALA levels in uremia; therefore, we speculated that the accumulated ALA in uremic patients would stimulate iron release from ferritin, resulting in accelerated oxidative stress and uremic complications. We measured the plasma ALA of uremic patients and examined the ALA-induced iron release from human ferritin. The participants consisted of 30 hemodialysis patients and 14 healthy subjects. Plasma malondialdehyde was measured as a surrogate marker of lipid peroxidation. The plasma exchange effluent from two patients who had undergone plasma exchange (for the treatment of systemic lupus erythematosus and acute myeloblastic leukemia) was collected and treated to obtain the human ferritin-rich fraction. Iron release from ferritin was examined using bathophenanthroline sulfate. The influence of antioxidants and different pH levels on iron release were investigated. Plasma ALA and malondialdehyde concentration in the hemodialysis patient was significantly higher than that in healthy subjects. ALA was positively correlated with malondialdehyde. The abundance of iron release was dependent on the ALA concentration and incubation time. Iron release at the high pH of 7.6 was decreased compared with that at pH 7.4. Citrate increased iron release at pH 7.4, but citrate-stimulated iron release was totally abolished at pH 7.6. Our study suggests that ALA accumulation may have a role to play in certain complications in uremic patients, such as oxidative stress, by releasing iron from ferritin.

Role of aldose reductase in the peritoneal changes of patients undergoing peritoneal dialysis.

BACKGROUND/AIMS: The mesothelium of patients undergoing peritoneal dialysis (PD) is exposed to glucose in dialysate. Glucose metabolites 3-deoxyglucosone and advanced glycation endproducts (AGEs) in the PD fluid induce peritoneal damage. Circulating factors also affect the peritoneum in the uremic model and predialysis patients. Aldose reductase (AR) generates precursors of 3-deoxyglucosone. We have reported AR acceleration in uremic patients. Therefore, AR acceleration might affect the peritoneum. The purpose of this study was to evaluate the AR level in PD patients and to determine the factors that change the peritoneum of these patients. METHODS: We measured the PD effluent (eff-) concentration of cancer antigen 125 (CA125) as a marker of mesothelial viability in PD patients. Erythrocyte AR, eff-, and plasma (p-) concentrations of 3-deoxyglucosone, AGEs, and malondialdehyde were also studied in 30 PD patients, 18 patients undergoing hemodialysis, and 8 control subjects. RESULTS: In the PD group, AR, p-3-deoxyglucosone, p-AGEs, and p-malondialdehyde were higher than in the control group. The predictors for eff-CA125 were not only PD duration and eff-3-deoxyglucosone, but also AR. CONCLUSION: AR was upregulated in PD patients. AR acceleration may affect the peritoneum in these patients. Further studies are needed to clarify the role of AR in PD patients.