The ferroxidase activity of caeruloplasmin is reduced in haemodialysis patients

A New Perspective for Potential Organ Damage Due to Iron-Mediated Oxidation in Thalassemia Major Patients

BACKGROUND

The aim of this study is to develop new perspectives to prevent or reduce potential organ damage due to iron-mediated oxidation in thalassemia major patients.

METHODS

Seventy patients were included in this study. Blood samples were taken from the patients before and after transfusion. Total thiol, native thiol, disulfide, disulfide/native thiol percentage ratio, ischemia modified albumin (IMA), total antioxidant status (TAS), total oxidant status (TOS), and ferroxidase levels were determined. Additionally, undepleted thiol level (UTL) was determined as a new parameter associated with organ damage.

RESULTS

After transfusion, the levels of native thiol, total thiol, disulfide, TAS, ferroxidase, and TOS were higher, while the IMA levels and disulfide/native thiol percent ratio were lower. Significant correlations were found between antioxidant and oxidant tests before and after transfusion. Additionally, a negative correlation was found between the TOS and UTL levels of the patients measured before the transfusion.

CONCLUSION

In the present study, transfusion therapy increased both oxidation and the antioxidant levels. In addition, the term UTL has been introduced as a parameter that enables the determination of the oxidation level that may cause potential organ damage in transfusion-dependent thalassemia patients.

Total metal concentrations in serum of dialysis patients and fractionation of Cu, Rb, Al, Fe and Zn in spent continuous ambulatory peritoneal dialysis fluids

Total metal concentrations were determined in the serum of 12 continuous ambulatory peritoneal dialysis (CAPD) patients and in fresh and spent CAPD fluids by electrothermal and flame atomic absorption spectrometry (ETAAS, FAAS). Concentrations of Cu in serum of CAPD patients ranged from 720 to 1780 ngcm(-3), Rb from 128 to 346 ngcm(-3), Al from 10 to 72 ngcm(-3), Fe from 800 to 2300 ngcm(-3) and Zn from 659 to 1310 ngcm(-3). The accuracy of the analytical procedure was checked by the analysis of the reference material Seronomtrade mark, Trace Elements in Serum. Good agreement between the certified and determined values was obtained for Al, Cu, Fe and Zn. The data on the total metal concentrations in CAPD fluids indicated that during CAPD fluid exchange the losses of Cu from 5.0 to 35 ngcm(-3), of Rb from 50 to 110 ngcm(-3) and of Al from 3.0 to 14.0 ngcm(-3) occurred through the peritoneal membrane. Although fresh CAPD fluids contained traces of Fe (3.0-5.0 ngcm(-3)), the transfer of this element took place through the peritoneal membrane into spent CAPD fluid (13.0-38.0 ngcm(-3)). Zn concentrations were in general lower in spent (20.0-80 ngcm(-3)) than in fresh CAPD fluids ( approximately 100 ngcm(-3)). To follow the mechanisms of the transfer of trace elements through the peritoneal membrane of CAPD patients, fractionation of metals was carried out in spent CAPD fluids by size exclusion chromatography with UV and AAS detection, applying Superdex HR 10/30 column. The chromatographic run was followed at 278 nm and separated metal species also determined 'off line' in 1 cm(3) fractions by ETAAS or FAAS. From the UV chromatograms and AAS analysis of trace elements in the separated fractions it was demonstrated that Cu, Al, Fe and Zn were bound to proteins and only partially to low molecular weight (LMW) species, while Rb was associated exclusively with LMW species. For characterisation of the high molecular weight (HMW) binding proteins, fractions containing trace elements were subjected to SDS-PAGE electrophoresis. Al and Fe were presumably bound to transferrin, but due to its low concentration in spent CAPD fluids, it was not possible to confirm its presence in the separated fractions. About 10% of Al and 15% of Fe corresponded to LMW species. A fraction of HMW proteins of Cu in spent CAPD fluids was most probably bound to albumin and Zn to albumin and globulins. About 50% of Cu and Zn existed in LMW proteins, while Zn was also found partially in ionic form.

Trace elements in hemodialysis patients: a systematic review and meta-analysis

BACKGROUND

Hemodialysis patients are at risk for deficiency of essential trace elements and excess of toxic trace elements, both of which can affect health. We conducted a systematic review to summarize existing literature on trace element status in hemodialysis patients.

METHODS

All studies which reported relevant data for chronic hemodialysis patients and a healthy control population were eligible, regardless of language or publication status. We included studies which measured at least one of the following elements in whole blood, serum, or plasma: antimony, arsenic, boron, cadmium, chromium, cobalt, copper, fluorine, iodine, lead, manganese, mercury, molybdenum, nickel, selenium, tellurium, thallium, vanadium, and zinc. We calculated differences between hemodialysis patients and controls using the differences in mean trace element level, divided by the pooled standard deviation.

RESULTS

We identified 128 eligible studies. Available data suggested that levels of cadmium, chromium, copper, lead, and vanadium were higher and that levels of selenium, zinc and manganese were lower in hemodialysis patients, compared with controls. Pooled standard mean differences exceeded 0.8 standard deviation units (a large difference) higher than controls for cadmium, chromium, vanadium, and lower than controls for selenium, zinc, and manganese. No studies reported data on antimony, iodine, tellurium, and thallium concentrations.

CONCLUSION

Average blood levels of biologically important trace elements were substantially different in hemodialysis patients, compared with healthy controls. Since both deficiency and excess of trace elements are potentially harmful yet amenable to therapy, the hypothesis that trace element status influences the risk of adverse clinical outcomes is worthy of investigation.

Antioxidant ceruloplasmin is expressed by glomerular parietal epithelial cells and secreted into urine in association with glomerular aging and high-calorie diet

Biologic aging is accelerated by high-calorie intake, increased free radical production, and oxidation of key biomolecules. Fischer 344 rats that are maintained on an ad libitum diet develop oxidant injury and age-associated glomerulosclerosis by 24 mo. Calorie restriction prevents both oxidant injury and glomerulosclerosis. Ceruloplasmin (Cp) is a copper-containing ferroxidase that functions as an antioxidant in part by oxidizing toxic ferrous iron to nontoxic ferric iron. Glomerular Cp mRNA and protein expression were measured in ad libitum-fed and calorie-restricted rats at ages 2, 6, 17, and 24 mo. In ad libitum-fed rats, Cp mRNA expression increased six-fold (P < 0.01) and protein expression increased five-fold (P = 0.01) between 2 and 24 mo of age. In calorie-restricted rats, Cp mRNA expression increased three-fold (P < 0.01) and protein expression increased 1.6-fold (NS) between 2 and 24 mo of age. Both the cell-associated alternately spliced variant and secreted variants of Cp were expressed. Immunofluorescent analysis showed that Cp was expressed by the parietal epithelial cells that line the inner aspect of Bowman's capsule in the glomerulus. Cp also was present in urine, particularly of old ad libitum-fed rats with high tissue Cp expression. Cp expression by Bowman's capsule epithelial cells therefore occurred in direct proportion to known levels of oxidant activity (older age and high-calorie diet) and is secreted into the urine. It is suggested that Cp expression at this site may be part of the repertoire of the glomerular parietal epithelial cell to protect the glomerular podocytes and the downstream nephron from toxic effects of filtered molecules, including ferrous iron.

Copper, selenium, zinc, and thiamine balances during continuous venovenous hemodiafiltration in critically ill patients

BACKGROUND

Acute renal failure is a serious complication in critically ill patients and frequently requires renal replacement therapy, which alters trace element and vitamin metabolism.

OBJECTIVE

The objective was to study trace element balances during continuous renal replacement therapy (CRRT) in intensive care patients.

DESIGN

In a prospective randomized crossover trial, patients with acute renal failure received CRRT with either sodium bicarbonate (Bic) or sodium lactate (Lac) as a buffering agent over 2 consecutive 24-h periods. Copper, selenium, zinc, and thiamine were measured with highly sensitive analytic methods in plasma, replacement solutions, and effluent during 8-h periods. Balances were calculated as the difference between fluids administered and effluent losses and were compared with the recommended intakes (RI) from parenteral nutrition.

RESULTS

Nineteen sessions were conducted in 11 patients aged 65 +/- 10 y. Baseline plasma concentrations of copper were normal, whereas those of selenium and zinc were below reference ranges; glutathione peroxidase was in the lower range of normal. The replacement solutions contained no detectable copper, 0.01 micromol Se/L (Bic and Lac), and 1.42 (Bic) and 0.85 (Lac) micromol Zn/L. Micronutrients were detectable in all effluents, and losses were stable in each patient; no significant differences were found between the Bic and Lac groups. The 24-h balances were negative for selenium (-0.97 micromol, or 2 times the daily RI), copper (-6.54 micromol, or 0.3 times the daily RI), and thiamine (-4.12 mg, or 1.5 times the RI) and modestly positive for zinc (20.7 micromol, or 0.2 times the RI).

CONCLUSIONS

CRRT results in significant losses and negative balances of selenium, copper, and thiamine, which contribute to low plasma concentrations. Prolonged CRRT is likely to result in selenium and thiamine depletion despite supplementation at recommended amounts.