Trace Elements Status and Their Associations With Related Antioxidant Enzyme Activities in Patients Receiving Peritoneal Dialysis and Hemodialysis

OBJECTIVE

It remains ambiguous as to whether the status of trace elements would affect their related enzyme activities toward defending a possible higher oxidative stress in patients receiving peritoneal dialysis (PD) or hemodialysis (HD) treatment. We investigated copper (Cu), zinc (Zn), and selenium (Se) status in patients receiving PD or HD treatments and further determined the association of these trace elements with their related antioxidant capacities in those patients.

METHODS

Sixty PD and 80 HD patients before and after HD treatment had their blood drawn. Demographic, clinical, and 24-hour diet recall data were recorded and collected. Plasma trace elements, oxidative stress indicators, and antioxidant enzyme activities were measured.

RESULTS

Patients receiving PD or HD treatments experienced similar Zn and Cu intakes. PD and HD patients displayed adequate mean plasma Cu, Zn, and Se levels. Patients receiving PD treatment showed significantly higher levels of Cu, Zn, advanced oxidation protein products (AOPPs), and superoxide dismutase (SOD) activity, but had significantly lower levels of Se and total antioxidant capacity when compared to levels in the HD patients at the pre-HD session. The levels of 3 trace elements and AOPP increased significantly, while the levels of glutathione (GSH), oxidized glutathione (GSSG), GPx, and SOD activities decreased significantly after receiving HD treatment than did the levels in the pre-HD session. Plasma Cu, Se, and Zn levels had a different correlation with plasma AOPP level, GPx, and SOD activities during PD, pre- or post-HD sessions. Plasma Cu, Zn, and Se levels did not have any association with their associated enzyme activities in patients with PD, while plasma Cu and Zn levels may have influenced SOD activity in HD patients.

CONCLUSIONS

An adequate Cu, Zn, and Se status is required in order to help their associated enzyme activity cope with increased oxidative stress during PD or HD sessions.

The effect of oral zinc on hemoglobin and dose of erythropoietin in hemodialysis patients

Background

In hemodialysis (HD) patients, low serum zinc level could cause hyporesponsivity to erythropoiesis-stimulating agents and lead to anemia. This study investigated the effects of oral zinc supplements on the required dose of erythropoietin in patients undergoing HD.

Materials and Methods

In a double-blinded randomized trial, 76 HD patients were assigned to 2 groups of 38. One group (intervention) was treated with oral zinc supplements of 210 mg, daily for 6 months, and the other group (control) used placebo capsules for 6 months. The serum zinc level, hemoglobin level, and required dose of erythropoietin, albumin, ferritin, ferrous, and total iron-binding capacity were evaluated 3 and 6 months after intervention.

Results

Repeated measures ANOVA did not show a significant increase in Hb level after 6 months of intervention (P = 0.28). However, the required dose of erythropoietin was decreased, but the changes were not statistically significant (P > 0.05). The changes in the other variables were not statistically significant.

Conclusion

Oral zinc supplementation in HD patients could not increase hemoglobin level irrespective of their serum zinc level.

Oral Zinc-Rich Oyster Supplementation Corrects Anemia in Rats

This study investigates the impact of various zinc supplementation methods on anemia in rats induced by phenylhydrazine (PHZ) and in 5/6-nephrectomized anemic rats. We compare oral zinc sulfate (ZnSO4) supplementation, oyster Crassostrea gigas supplementation, and hard clam Meretrix lusoria supplementation on red blood cell (RBC) levels. Oral zinc-rich oyster supplementation (2.70 mg Zn (30 g oyster)/day/rat) effectively corrects anemia in both experimental groups. Rats orally fed oysters for four days exhibit similar effectiveness as those receiving a single ZnSO4 injection (0.95 mg Zn (4.18 mg ZnSO4⋅7H2O)/rat). In contrast, oral ZnSO4 supplementation (2.70 mg Zn (11.88 mg ZnSO4⋅7H2O)/day/rat) does not significantly increase RBC levels, suggesting better zinc absorption from oysters. A placebo group of anemic rats supplemented with hard clams, similar in composition to oysters but much lower in zinc, did not change RBC counts. This supports oysters' high zinc content as the key to correcting anemia. Oysters also contain high iron levels, offering a potential solution for iron-deficiency anemia while supporting bone marrow erythropoiesis. In summary, oral oyster supplementation emerges as an effective strategy to correct anemia in rats with added zinc and iron support for erythropoiesis.

Association of Zinc with Anemia

Zinc is an essential trace element, and anemia is the most common blood disorder. The association of zinc with anemia may be divided into three major forms: (1) zinc deficiency contributing to anemia, (2) excess intake of zinc leading to anemia, and (3) anemia leading to abnormal blood-zinc levels in the body. In most cases, zinc deficiency coexists with iron deficiency, especially in pregnant women and preschool-age children. To a lesser extent, zinc deficiency may cooperate with other factors to lead to anemia. It seems that zinc deficiency alone does not result in anemia and that it may need to cooperate with other factors to lead to anemia. Excess intake of zinc is rare. However, excess intake of zinc interferes with the uptake of copper and results in copper deficiency that leads to anemia. Animal model studies indicate that in anemia, zinc is redistributed from plasma and bones to the bone marrow to produce new red blood cells. Inadequate zinc status (zinc deficiency or excess) could have effects on anemia; at the same time, anemia could render abnormal zinc status in the body. In handling anemia, zinc status needs to be observed carefully, and supplementation with zinc may have preventive and curative effects.

Zinc Deficiency, Plasma Fatty Acid Profile and Desaturase Activities in Hemodialysis Patients: Is Supplementation Necessary?

Background: Desaturation and elongation are critical processes in endogenous metabolic fatty acid pathways. Zinc (Zn) is a cofactor for desaturases and elongases enzymes. There is limited evidence regarding the relationships between biomarkers of Zn status, nutritional intake, plasma phospholipid fatty acid profile and clinical outcomes among patients undergoing hemodialysis (HD). Objective: To examine the relationships between dietary and serum levels of Zn and Cu/Zn ratio and to explore associations of these micronutrients with PUFA profile and estimated desaturase and elongase enzyme activities in serum phospholipids among HD patients. Methods: This study included 40 adult patients undergoing hemodialysis treatment. Repeated 24-h recalls were applied for dietary intake assessment. Serum concentration of Zn and Cu were determined using inductively coupled plasma mass spectrometry and fatty acid composition by gas-liquid chromatography. Desaturase and elongase activities were calculated from product-precursor fatty acid ratios. Results: Inadequate dietary Zn intake was found in 55% of HD patients. They all had serum Zn concentration below the reference value of 60 μg/dL (mean 38.8 ± 7.72 μg/dL). Adequate zinc intake was accompanied with significantly higher intake of energy, total fats, SFA, MUFA and proteins. There was no correlation between Zn serum status and Zn intake estimates. Serum Cu/Zn ratio was high, (2.76 ± 0.68), directly and significantly associated with HD period, CRP, BMI, VFA, and inversely with Kt/V, albumin, iron, and iPTH. The n-6/n-3 ratio in plasma phospholipids was elevated (12.25 ± 3.45) and patients with inadequate Zn intake had lower n-3 PUFA intake and status compared to those with adequate intake. Serum Zn concentrations were inversely correlated with linoleic/dihomo-γ-linolenic acid ratio (LA/DGLA) (p = 0.037), related to D6-desaturase activity (p = 0.033) and directly with DGLA relative abundances (p = 0.024). Cu status was inversely associated with EPA level (p = 0.03) and estimates of elongase activity (p = 0.001). Furthermore, positive relationship was found between the Cu/Zn ratio and determined elongase value (p = 0.01). Conclusion: Findings of this study underpin the high prevalence of Zn deficiency and inadequate n-3 PUFA intake and status among subjects undergoing HD. The results obtained indicate that the assessment of Zn status should be a standard parameter of nutritional status screening in HD patients while emphasizing the importance of Cu/Zn determination. Although further research is warranted, Zn and-n-3 PUFA supplementation in HD patients might be beneficial for the prevention and attenuation of adverse health outcomes.

In anemia zinc is recruited from bone and plasma to produce new red blood cells

Anemia is highly prevalent in people with chronic kidney disease (CKD), and CKD patients always have lower plasma but higher erythrocyte Zn levels than healthy people. To date, no satisfactory mechanism has explained these Zn metabolism abnormalities. We collected blood samples from patients on hemodialysis, 5/6 nephrectomized rats and phenylhydrazine (PHZ)-induced anemic mice and rats and compared them with their normal counterparts. We found that all the anemic animals had significantly decreased plasma Zn levels but elevated erythrocyte Zn levels. We also found that in anemic mice, new red blood cells (reticulocytes) had a ~7-fold higher Zn concentration than mature erythrocytes. When excess Zn was supplied to the rats, there was a ~1.2-fold increase in the Zn level in the rat bones. When Zn was depleted in the rats, the bones lost the greatest amount of Zn in the body (a 45% decrease). We prepared Zn-depleted rats and rendered these rats anemic by treating them with PHZ, and we compared them with normal rats. We found that in PHZ-induced anemia, rats released ~16% of Zn from their bones. Rat bones not only act as a 'reservoir' to adjust the excess or deficient Zn levels but also release Zn in anemia, and the released Zn stimulates erythropoiesis in the bone marrow. In anemia, Zn is redistributed from the plasma (causing the plasma Zn level to decreases) and bones to the bone marrow to produce reticulocytes (causing erythrocyte Zn level elevation).

Characterizing Dysgeusia in Hemodialysis Patients

Dysgeusia (abnormal taste) is common in those with chronic kidney disease and contributes to poor nutritional intake. Previous sensory work has shown that taste improves after dialysis sessions. The goal of this pilot study was to characterize altered taste perceptions in patients on dialysis compared with healthy adults, and to evaluate relationships between serum parameters with taste perceptions. We hypothesized that patients undergoing dialysis would experience blunted taste intensities compared with controls, and that serum levels of potential tastants would be inversely related to taste perception of compounds. Using a cross-sectional design, we carried out suprathreshold sensory assessments (flavor intensity and liking) of tastants/flavors potentially influenced by kidney disease and/or the dialysis procedure. These included sodium chloride, potassium chloride, calcium chloride, sodium phosphate, phosphoric acid, urea, ferrous sulfate, and monosodium glutamate. Individuals on maintenance hemodialysis (n= 17, 10 males, range 23-87 years) were compared with controls with normal gustatory function (n=29, 13 males, range 21-61 years). Unadjusted values for intensity and liking for the solutions showed minimal differences. However, when values were adjusted for participants' perceptions of water (as a control for taste abnormalities), intensity of monosodium glutamate, sodium chloride, and sodium phosphate solutions were more intense for patients on dialysis compared with controls. Some significant correlations were also observed between serum parameters, particularly potassium, for dialysis patients and sensory ratings. These results suggest altered taste perception in patients during dialysis warrants further study.

Effect of Zinc Supplementation on Renal Anemia in 5/6-Nephrectomized Rats and a Comparison with Treatment with Recombinant Human Erythropoietin

Anemia is a severe complication in patients with chronic kidney disease (CKD). Treatment with exogenous erythropoietin (EPO) can correct anemia in many with CKD. We produced 5/6-nephrectomized rats that became uremic and anemic at 25 days post surgery. Injection of the anemic 5/6-nephrectomized rats with 2.8 mg zinc/kg body weight raised their red blood cell (RBC) levels from approximately 85% of the control to 95% in one day and continued for 4 days. We compared the effect of ZnSO4 and recombinant human erythropoietin (rHuEPO) injections on relieving anemia in 5/6-nephrectomized rats. After three consecutive injections, both the ZnSO4 and rHuEPO groups had significantly higher RBC levels (98 ± 6% and 102 ± 6% of the control) than the saline group (90 ± 3% of the control). In vivo, zinc relieved anemia in 5/6-nephrectomized rats similar to rHuEPO. In vitro, we cultured rat bone marrow cells supplemented with ZnCl2, rHuEPO, or saline. In a 4-day suspension culture, we found that zinc induced erythropoiesis similar to rHuEPO. When rat bone marrow cells were supplement-cultured with zinc, we found that zinc stimulated the production of EPO in the culture medium and that the level of EPO produced was dependent on the concentration of zinc supplemented. The production of EPO via zinc supplementation was involved in the process of erythropoiesis.

Zinc Supplementation Stimulates Red Blood Cell Formation in Rats

In rats, mice, and humans, it is known that zinc deficiency may be related to anemia, and zinc supplementation influences hemoglobin production. Our previous studies indicate that in fish, zinc supplementation stimulates red blood cell (RBC) formation (erythropoiesis). However, it is not clear whether the mechanism of zinc-induced erythropoiesis stimulation in fish also occurs in rats. We induced anemia in rats using phenylhydrazine (PHZ) and injected either saline or ZnSO₄ solution. We found that an appropriate amount of zinc stimulated erythropoiesis in the PHZ-induced anemic rats. The effects of ZnSO₄ injection were dose-dependent. When the concentration of ZnSO₄ was higher than 2.8 mg zinc/kg body weight, the RBC level of the anemic rats increased from 60 ± 7% to 88 ± 10% that of the normal rats in two days. Rat bone marrow cells with or without ZnCl₂ supplementation were cultured in suspension in vitro. In the cell culture when the zinc concentration was at 0.3 mM, a 1.6-fold proliferation of nascent immature reticulocytes (new RBCs) was observed after one day. In the rat blood, zinc was combined with serum transferrin to induce erythropoiesis. The stimulation of RBC formation by zinc appears to be common among different animals.