Antioxidants for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular disease (CVD) and death. Increased oxidative stress in people with CKD has been implicated as a potential causative factor. Antioxidant therapy decreases oxidative stress and may consequently reduce cardiovascular morbidity and death in people with CKD. This is an update of a Cochrane review first published in 2012.

OBJECTIVES

To examine the benefits and harms of antioxidant therapy on death and cardiovascular and kidney endpoints in adults with CKD stages 3 to 5, patients undergoing dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies until 15 November 2022 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials investigating the use of antioxidants, compared with placebo, usual or standard care, no treatment, or other antioxidants, for adults with CKD on cardiovascular and kidney endpoints.

DATA COLLECTION AND ANALYSIS

Titles and abstracts were screened independently by two authors who also performed data extraction using standardised forms. Results were pooled using random effects models and expressed as risk ratios (RR) or mean difference (MD) with 95% confidence intervals (CI). Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 95 studies (10,468 randomised patients) that evaluated antioxidant therapy in adults with non-dialysis-dependent CKD (31 studies, 5342 patients), dialysis-dependent CKD (41 studies, 3444 patients) and kidney transplant recipients (21 studies, 1529 patients). Two studies enrolled dialysis and non-dialysis patients (153 patients). Twenty-one studies assessed the effects of vitamin antioxidants, and 74 assessed the effects of non-vitamin antioxidants. Overall, the quality of included studies was moderate to low or very low due to unclear or high risk of bias for randomisation, allocation concealment, blinding, and loss to follow-up. Compared with placebo, usual care, or no treatment, antioxidant therapy may have little or no effect on cardiovascular death (8 studies, 3813 patients: RR 0.94, 95% CI 0.64 to 1.40; I² = 33%; low certainty of evidence) and probably has little to no effect on death (any cause) (45 studies, 7530 patients: RR 0.95, 95% CI 0.82 to 1.11; I² = 0%; moderate certainty of evidence), CVD (16 studies, 4768 patients: RR 0.79, 95% CI 0.63 to 0.99; I² = 23%; moderate certainty of evidence), or loss of kidney transplant (graft loss) (11 studies, 1053 patients: RR 0.88, 95% CI 0.67 to 1.17; I² = 0%; moderate certainty of evidence). Compared with placebo, usual care, or no treatment, antioxidants had little to no effect on the slope of urinary albumin/creatinine ratio (change in UACR) (7 studies, 1286 patients: MD -0.04 mg/mmol, 95% CI -0.55 to 0.47; I² = 37%; very low certainty of evidence) but the evidence is very uncertain. Antioxidants probably reduced the progression to kidney failure (10 studies, 3201 patients: RR 0.65, 95% CI 0.41 to 1.02; I² = 41%; moderate certainty of evidence), may improve the slope of estimated glomerular filtration rate (change in eGFR) (28 studies, 4128 patients: MD 3.65 mL/min/1.73 m², 95% CI 2.81 to 4.50; I² = 99%; low certainty of evidence), but had uncertain effects on the slope of serum creatinine (change in SCr) (16 studies, 3180 patients: MD -13.35 µmol/L, 95% CI -23.49 to -3.23; I² = 98%; very low certainty of evidence). Possible safety concerns are an observed increase in the risk of infection (14 studies, 3697 patients: RR 1.30, 95% CI 1.14 to 1.50; I² = 3%; moderate certainty of evidence) and heart failure (6 studies, 3733 patients: RR 1.40, 95% CI 1.11 to 1.75; I² = 0; moderate certainty of evidence) among antioxidant users. Results of studies with a low risk of bias or longer follow-ups generally were comparable to the main analyses.

AUTHORS' CONCLUSIONS

We found no evidence that antioxidants reduced death or improved kidney transplant outcomes or proteinuria in patients with CKD. Antioxidants likely reduce cardiovascular events and progression to kidney failure and may improve kidney function. Possible concerns are an increased risk of infections and heart failure among antioxidant users. However, most studies were of suboptimal quality and had limited follow-up, and few included people undergoing dialysis or kidney transplant recipients. Furthermore, the large heterogeneity in interventions hampers drawing conclusions on the efficacy and safety of individual agents.

Hypozincemia in COVID-19 Patients Correlates With Stronger Antibody Response

Zinc ion as an enzyme cofactor exhibits antiviral and anti-inflammatory activity during infection, but circulating zinc ion level during Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection is unclear. This study aimed to evaluate serum zinc ion level in Coronavirus Disease 2019 (COVID-19) patients and healthy subjects, as well as its correlation with antibodies against SARS-CoV-2. 114 COVID-19 patients and 48 healthy subjects (38 healthy volunteers and 10 close contacts of patients with COVID-19) were included. Zinc ion concentration and levels of antibodies against SARS-CoV-2 Spike 1 + Spike 2 proteins, nucleocapsid protein, and receptor-binding domain in serum were measured. Results showed that the concentration of zinc ion in serum from COVID-19 patients [median: 6.4 nmol/mL (IQR 1.5 – 12.0 nmol/mL)] were significantly lower than that from the healthy subjects [median: 15.0 nmol/mL (IQR 11.9 – 18.8 nmol/mL)] (p < 0.001) and the difference remained significant after age stratification (p < 0.001) or when the patients were at the recovery stage (p < 0.001). Furthermore, COVID-19 patients with more severe hypozincemia showed higher levels of IgG against the receptor-binding domain of SARS-CoV-2 spike protein. Further studies to confirm the effect of zinc supplementation on improving the outcomes of COVID-19, including antibody response against SARS-CoV-2, are warranted.

Zinc supplementation and immune factors in adults: a systematic review and meta-analysis of randomized clinical trials

PURPOSE

This systematic review and meta-analysis aimed to investigate the effect of zinc supplementation on immune factors in randomized controlled trials.

METHODS

A comprehensive search was done in PubMed, Scopus, Web of Science, Embase, and Cochrane databases up to December 2020. We used standard and weighted mean differences and 95% confidence intervals for net changes in selected parameters of immune responses. Subgroup analysis was used to find heterogeneity.

RESULT

Overall, 35 RCTs comprising 1995 participants were eligible for this meta-analysis. There was a significant reduction of circulating CRP (WMD: -32.4; 95% CI: -44.45 to -19.62, p < 0.001), hs-CRP (WMD: -0.95; 95% CI: -1.01 to -0.89, p < 0.001), Neutrophil levels (SMD: -0.46; 95% CI: -0.90 to -0.01, p = 0.043), following zinc supplementation. CD4 level also increased significantly, (WMD: 1.79; 95% CI: 0.57 to 3, p = 0.004). Zinc supplementation had no significant effect on WBC (SMD: -0.66; 95% CI: -1.67 to 0.36, p = 0.204), lymphocyte (WMD: 1.86; 95% CI: -0.86 to 4.58, p = 0.181), monocyte levels (SMD: -0.16; 95% CI: -0.07 to 0.39, p = 0.167), CD3 (SMD: 0.37; 95% CI: -0.49 to 1.22, p = 0.399).

CONCLUSION

Zinc supplementation decreased the CRP, hs-CRP and TNF-α, IL-6, neutrophil and increased CD3 and CD4 level significantly.

Effects of non-pharmacological interventions as vaccine adjuvants in humans: a systematic review and network meta-analysis

INTRODUCTION

Psychological and behavioural may enhance vaccine effectiveness. We conducted a systematic review and network meta-analysis (NMA) to examine the effects of non-pharmacological adjuvants on vaccine effectiveness, as measured by antibody responses to vaccination.

AREAS COVERED

Electronic databases (EMBASE, Medline, PsychINFO, CINAHL) were searched from inception to 6th February 2018. This yielded 100 eligible papers, reporting 106 trials: 79 interventions associated with diet and/or nutrition; 12 physical activity interventions and 9 psychological interventions.Over half (58/106) of trials reported evidence of an enhanced antibody response to vaccination across one or more outcomes. The NMA considered the comparative effects between all intervention types, control and placebo for antibody titres (48 studies), seroconversion (25 studies) and seroprotection (23 studies) separately. The NMA provided weak evidence in support of nutritional formulae and probiotics in increasing antibody titres.

EXPERT OPINION

This review offers a comprehensive summary of the literature on non-pharmacological interventions as vaccine adjuvants. The evidence is characterised by considerable heterogeneity but provides early evidence in support of nutritional formulae and probiotic interventions. Psychological and exercise-based interventions were characterised by limited and unreliable evidence. Large, well-designed studies including consistent core outcomes and measures of intervention adherence and fidelity are required.

Association between Serum Zinc Levels and Clinical Index or the Body Composition in Incident Hemodialysis Patients

Background: The relationships between serum zinc levels and body composition or clinical outcomes of incident hemodialysis (HD) patients remain unclear. Methods: This prospective observational study examined the relationships between serum zinc levels and clinical indexes, including body composition, in 142 incident HD patients using a bioelectrical impedance analysis. Patients were divided into three groups according to baseline serum zinc levels: tertile, <45, 45–59, and ≥60 µg/dL. The reference group was set as ≥60 µg/dL. Cox’s regression analysis was performed to investigate the relationships between serum zinc categories and cardiovascular events and all-cause mortality after adjustments for potential confounders. Results: Serum zinc levels positively correlated with the nutritional index and negatively correlated with fluid volume markers. In a mean follow-up of 2.5 years, there were 20 cases of cardiovascular events and 15 of all-cause mortality. In the Cox’s regression analysis for cardiovascular events and all-cause mortality, the hazard ratio increased with a decrease in serum zinc levels, but was not significant. Conclusion: Serum zinc levels were associated with nutritional and fluid volume markers in incident HD patients. To clarify the relationship between serum zinc levels and cardiovascular events or mortality, further studies with a larger number of cases will be necessary.

Self-Care for Common Colds: The Pivotal Role of Vitamin D, Vitamin C, Zinc, and Echinacea in Three Main Immune Interactive Clusters (Physical Barriers, Innate and Adaptive Immunity) Involved during an Episode of Common Colds-Practical Advice on Dosages and on the Time to Take These Nutrients/Botanicals in order to Prevent or Treat Common Colds

Maintaining a normal healthy immune defense system lowers the incidence and/or the severity of symptoms and/or the duration of common cold (CC). Physical barriers and innate and adaptive immunity have been involved during a CC episode. Vitamins C and D, zinc, and Echinacea have evidence-based efficacy on these immune system barriers. This review includes 82 eligible studies to consider the preventive role of these nutrients in immune clusters and in CC to provide advice on dosage and assumption of these nutrients. Regarding vitamin C, regular supplementation (1 to 2 g/day) has shown that vitamin C reduces the duration (in adults by 8%, in children by 14%) and the severity of CC. Considering zinc, the supplementation may shorten the duration of colds by approximately 33%. CC patients may be instructed to try zinc within 24 hours of onset of symptoms. As for vitamin D, the supplementation protected against CC overall, considering baseline levels and age. Patients with vitamin D deficiency and those not receiving bolus doses experienced the most benefit. Regarding Echinacea, prophylactic treatment with this extract (2400 mg/day) over 4 months appeared to be beneficial for preventing/treating CC. In conclusion, the current evidence of efficacy for zinc, vitamins D and C, and Echinacea is so interesting that CC patients may be encouraged to try them for preventing/treating their colds, although further studies are needed on this topic.

Effect of Zinc Supplementation on Maintenance Hemodialysis Patients: A Systematic Review and Meta-Analysis of 15 Randomized Controlled Trials

We aimed to examine the effects of zinc supplementation on nutritional status, lipid profile, and antioxidant and anti-inflammatory therapies in maintenance hemodialysis (MHD) patients. We performed a systematic review and meta-analysis of randomized, controlled clinical trials of zinc supplementation. Metaregression analyses were utilized to determine the cause of discrepancy. Begg and Egger tests were performed to assess publication bias. Subgroup analysis was utilized to investigate the effects of zinc supplementation in certain conditions. In the crude pooled results, we found that zinc supplementation resulted in higher serum zinc levels (weighted mean difference [WMD] = 28.489; P < 0.001), higher dietary protein intake (WMD = 8.012; P < 0.001), higher superoxide dismutase levels (WMD = 357.568; P = 0.001), and lower levels of C-reactive protein (WMD = −8.618; P = 0.015) and malondialdehyde (WMD = −1.275; P < 0.001). The results showed no differences in lipid profile. In the metaregression analysis, we found that serum zinc levels correlated positively with intervention time (β = 0.272; P = 0.042) and varied greatly by ethnicity (P = 0.023). Results from Begg and Egger tests showed that there was no significant bias in our meta-analysis (P > 0.1). Results of subgroup analysis supported the above results. Our analysis shows that zinc supplementation may benefit the nutritional status of MHD patients and show a time-effect relationship.

Gestational zinc deficiency impairs humoral and cellular immune responses to hepatitis B vaccination in offspring mice

Background

Gestational zinc deficiency has been confirmed to impair the infant immune function. However, knowledge about effects of maternal mild zinc deficiency during pregnancy on hepatitis B vaccine responsiveness in offspring is limited. In this report, we aimed to examine how maternal zinc deficiency during pregnancy influences humoral and cellular immune responses to hepatitis B vaccination in offspring of BALB/c mice.

Methodology/Principal Findings

From day 1 of pregnancy upon delivery, maternal mice were given a standard diet (30 mg/kg/day zinc), zinc deficient diet (8 mg/kg/day zinc), or combination of zinc deficient diet (8 mg/kg/day zinc in the first 2 weeks of gestation) and zinc supplement diet (150 mg/kg/day zinc for the last week of pregnancy), respectively. Newborn pups of these maternal mice were immunized with hepatitis B vaccine at postnatal weeks 0, 2 and 4. Then, splenocytes and blood samples from the offspring mice were harvested for detection of serum zinc concentrations, humoral and cell-mediated immune responses, expression of cytokines using ELISA, CCK-8 and flow cytometric analysis. Results from the present study demonstrated that gestational zinc deficiency inhibited antibody responses, and decreased the proliferative capacity of T cells in offsprings immunized with hepatitis B vaccine. Additionally, HBsAg-specific cytokines analysis revealed that gestational zinc deficiency could inhibit secretion of IFN-γ from splenocytes, and decrease IFN-γ expression of CD4⁺ and CD8⁺ T cells.

Conclusions/Significance

Gestational zinc deficiency can weaken the humoral and cell-mediated immune responses to hepatitis B vaccine via decreasing B cell counts and hepatitis B virus-specific immunoglobulin G production, as well as reducing T cell proliferation, CD4⁺/CD8⁺ T cell ratio, and Th1-type immune responses.

Zinc supplementation and TNF-α levels in vaccinated cardiac patients

OBJECTIVE

To investigate whether zinc supplementation could affect serum tumor necrosis factor-alpha (TNF-α) levels in congenital and acquired cardiac patients attending for an influenza vaccine.

METHODS

9-18 years old, voluntary children with cardiac disease were weighed, measured height and blood samples for hemoglobin level, zinc level, IgA and IgG titers of influenza A and B serotypes and TNF-α levels were obtained. The children were randomly assigned to 1 of 2 groups: ZV group received both zinc supplementation and influenza vaccine; V group received influenza vaccine. Serum TNF-α levels were measured at 28 days after the immunization.

RESULTS

Mean (±SD) serum zinc level was 100 (±20) μg/dL. Cases with congenital heart disease had lower serum zinc levels than acquired ones (93±17 μg/dL, 116±18 μg/dL; respectively, p<0.001). Median titers of serum TNF-α decreased after vaccination (78.9 pg/mL, 74.8 pg/mL; p<0.05) but this significant change occurred only in ZV group (77.1 pg/mL, 73.4 pg/mL; p=0.001). Vaccine associated adverse events were similar in ZV and V groups except malaise (0% in ZV and 23.8% in V group; p<0.05). Adverse events were similar in patients with congenital and acquired heart diseases. During the previous influenza season, 77.3% had more than two episodes of upper respiratory tract infection (URTI), however, after vaccination only 13.6% had more than two episode of URTI.

CONCLUSION

Zinc supplementation has a beneficial effect on malaise, one of the influenza vaccine associated adverse events, and decrease serum TNF-α levels.

Cu/Zn ratios are associated with nutritional status, oxidative stress, inflammation, and immune abnormalities in patients on peritoneal dialysis

OBJECTIVES

We evaluated the relationship of the plasma copper/zinc (Cu/Zn) ratio with nutritional status, inflammation, oxidative stress, and immune function in peritoneal dialysis patients.

DESIGN AND METHODS

Clinical and laboratory parameters were measured in patients (n=45) and age- and sex-matched healthy individuals (n=30).

RESULTS

There were significant negative correlations of the Cu/Zn ratio with nutrition-related parameters (body mass index [BMI], creatinine, hemoglobin, and albumin) and antioxidant (vitamin C and E) levels and positive correlations of the Cu/Zn ratio with the levels of high sensitivity C-reactive protein (hs-CRP) and oxidation products (malondialdehyde [MDA] and protein carbonyl). The Cu/Zn ratio was negatively correlated with the percentages of B- and T-lymphocyte subsets and the ratio of CD4/CD8 antigens.

CONCLUSIONS

In peritoneal dialysis patients, elevated Cu/Zn ratios are associated with malnutrition, increased oxidative stress, inflammation, and disrupted immune status.

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.

Zinc supplementation for the treatment or prevention of disease: current status and future perspectives

Zinc is a nutritionally essential trace element, and thus zinc deficiency may severely affect human health. Many studies were published in which the effect of nutritional zinc supplementation on the incidence or severity of a certain disease was investigated. This review summarizes the main observations and aims to evaluate the use of nutritional zinc supplementation for prevention and treatment of human disease.

Complementary medicine for treating or preventing influenza or influenza-like illness

The objective of this review was to assess the evidence for the effectiveness of complementary and alternative therapies for preventing or treating influenza or influenza-like illness, including avian influenza. Systematic literature searches were conducted in 5 databases until June 2006; other data sources included bibliographies of located articles, manufacturers of commercially available preparations, and experts in the field. Randomized clinical trials, controlled against placebo or active comparator, were included. Decisions on inclusion, data extraction, and methodological quality assessment were performed independently by 2 reviewers. Fourteen randomized controlled trials testing 7 preparations were included. For Oscillococcinum, P. quinquefolium extract, Sambucus nigra, and the herbal combination Kan Jang, 2 or more trials reporting some encouraging data were identified. In conclusion, the effectiveness of any complementary and alternative therapy for treating or preventing seasonal influenza is not established beyond reasonable doubt. Current evidence from randomized controlled trials is sparse and limited by small sample sizes, low methodological quality, or clinically irrelevant effect sizes. For avian influenza, no data are currently available. These results strengthen conventional approaches for seasonal influenza.

Effect of zinc supplementation on immune and inflammatory responses in pediatric patients with shigellosis

BACKGROUND

Several studies showed benefits of long-term zinc supplementation on the incidence, severity, and duration of diarrhea and on the incidence of respiratory infections. Prolonged zinc supplementation also improves cell-mediated immunity in severely malnourished children.

OBJECTIVE

We studied the effect of short-term zinc supplementation on intrinsic and specific immune and inflammatory responses in moderately malnourished children with acute shigellosis.

DESIGN

A randomized, double-blind, placebo-controlled trial was conducted in Shigella-infected children aged 12-59 mo. Elemental zinc (20 mg) and a multivitamin containing vitamins A and D, thiamine, riboflavin, nicotinamide, and calcium at twice the recommended dietary allowance were given daily for 2 wk to the zinc group (n = 28), whereas the multivitamin alone was given to the control group (n = 28). Standard antibiotic therapy was given to all patients.

RESULTS

Serum zinc concentrations increased in both groups during convalescence; however, zinc supplementation showed a significant effect. The lymphocyte proliferation response in the zinc group increased relative to that in the control group (P = 0.002), but no significant effects were seen on concentrations of cytokines (interleukin 2 and interferon gamma) released from mitogen-stimulated mononuclear cells or on concentrations of cytokines (interleukin 2, interferon gamma, and interleukin 1beta) in feces. Among the antigen [lipopolysaccharide and invasion plasmid-encoded antigen (Ipa)]-specific antibodies, plasma Ipa-specific immunoglobulin G responses at day 30 were significantly higher in the zinc group than in the control group. However, the 2 groups did not differ significantly in the other antigen-specific responses in plasma and stool.

CONCLUSION

A 14-d course of zinc supplementation during acute shigellosis increases the lymphocyte proliferation response and the Ipa-specific immunoglobulin G response.

Trace elements and vitamins in maintenance dialysis patients

Although protein-energy malnutrition occurs commonly in patients with end-stage renal disease undergoing maintenance dialysis treatment, it is not the only form of malnutrition that may exist in these individuals. They may also suffer from deficiencies of micronutrients, particularly trace elements and vitamins. More commonly occurring vitamin deficiencies in maintenance dialysis patients include those for vitamin C (ascorbate), folate, vitamin B6 (pyridoxine), and 1,25-dihydroxycholecalciferol (calcitriol). Among trace elements, deficiencies may occur more commonly for iron, zinc, and possibly selenium, whereas toxicities are more common with aluminum and possibly copper. Evidence suggests that there is an abnormally high prevalence of antioxidant deficiency in maintenance dialysis patients, especially because a low intake of protein and energy may be associated with inadequate ingestion of antioxidant vitamins (ie, vitamins E and C and carotenoids). Thus, some micronutrient deficiencies in maintenance dialysis patients may contribute to the development of atherosclerotic cardiovascular disease. Dietary requirements for vitamins and trace elements in maintenance dialysis patients are reviewed and the recommended daily intakes are discussed.

Intestinal and systemic immune responses to an oral cholera toxoid B subunit whole-cell vaccine administered during zinc supplementation

Zinc plays a critical role in the normal functioning of the immune system. We investigated whether zinc sulfate administered orally to adult zinc-replete volunteers modulates systemic and intestinal immune responses to an oral killed cholera toxoid B subunit (CTB) whole-cell cholera vaccine. The 30 participants were immunized twice, with a 17-day interval. The vaccinees in the intervention group ingested 45 mg of elemental zinc thrice daily for 9 days starting 2 days before each vaccine dose. The median serum anti-CTB immunoglobulin A (IgA) and IgG responses from day 0 to day 30, i.e. after two vaccine doses, were 13-fold lower (P value for identical distribution, <0.005) in the zinc-supplemented compared to the nonsupplemented vaccinees. The median serum vibriocidal responses from baseline to after one (day 0 to day 17) and two (day 0 to day 30) vaccine doses were at least sixfold (P = 0.033) and fourfold (P = 0.091) higher, while the median fecal anti-CTB IgA response after two doses was estimated to be fourfold higher (P = 0.084) in the zinc-supplemented vaccinees. These observations show that zinc reduces the antitoxin and may enhance the antibacterial responses in serum. Zinc may also improve the intestinal antitoxin immune response. Oral zinc administration has the potential to modify critical immune responses to antigens applied to mucosal surfaces.

Zinc-altered immune function

Zinc is known to be essential for all highly proliferating cells in the human body, especially the immune system. A variety of in vivo and in vitro effects of zinc on immune cells mainly depend on the zinc concentration. All kinds of immune cells show decreased function after zinc depletion. In monocytes, all functions are impaired, whereas in natural killer cells, cytotoxicity is decreased, and in neutrophil granulocytes, phagocytosis is reduced. The normal functions of T cells are impaired, but autoreactivity and alloreactivity are increased. B cells undergo apoptosis. Impaired immune functions due to zinc deficiency are shown to be reversed by an adequate zinc supplementation, which must be adapted to the actual requirements of the patient. High dosages of zinc evoke negative effects on immune cells and show alterations that are similar to those observed with zinc deficiency. Furthermore, when peripheral blood mononuclear cells are incubated with zinc in vitro, the release of cytokines such as interleukins (IL)-1 and -6, tumor necrosis factor-alpha, soluble IL-2R and interferon-gamma is induced. In a concentration of 100 micro mol/L, zinc suppresses natural killer cell killing and T-cell functions whereas monocytes are activated directly, and in a concentration of 500 micro mol/L, zinc evokes a direct chemotactic activation of neutrophil granulocytes. All of these effects are discussed in this short overview.

Immunologic defects and vaccination in patients with chronic renal failure

Patients with chronic renal failure suffer from defective host defenses which are directly the result of the renal impairment, in addition to those dependent on the primary illness leading to the renal failure. The mechanisms underlying the defective responses in phagocytic cells, lymphocytes and antigen processing are likely due to either failure to adequately eliminate suppressive compounds by the defective kidneys or to improper metabolic processing of the factors by the damaged renal parynchema. That some of the defects are reversed by transplantation and not dialysis suggests that renal parenchymal metabolic activities may be involved, although it is also possible that functioning glomerular cells are capable of filtering substances that membranes are not currently capable of eliminating. The current strategy for dealing with the immunodeficiency appears to be totally based on developing means to circumvent the defective function. The other approach, correction of the impaired function, cannot be even considered until the mechanisms underlying the defective function of the cells involved in defenses are better delineated. It seems possible that one or a few compounds are pivotal in altering the function of all the affected cell lines, since, with only a small amount of effort, it is possible to relate the dysfunction to abnormal cell membrane functions in phagocytic cells, dendritic cells and lymphocytes. Until the biochemical basis of the dysfunction of all the cell types affected are better defined, such exercises cannot be translated into better management of patients with chronic renal failure. Proper function of host defenses requires that appropriate cells can properly respond to threats to host viability. For the cells of the immune system (phagocytes and lymphocytes) this means that their response to regulatory molecules be appropriate, that their mobility be normal, that their adherence to substrates be preserved, and that they can generate the appropriate response to the challenge. For neutrophils, for example, it is necessary that they recognize and mobilize appropriately to chemotactic stimuli, that they be able to adhere to and migrate through endothelial lining, that their phagocytic activity be sufficient, and that they can kill and degrade endocytosed particles and generate appropriate secretions. Similar lists of requirements for good function can be generated for any cell type in the immune defense system. Uremia, as well as currently available treatments for uremia, directly or indirectly alters the function of all phases of appropriate immune cell function. Defective host responses in uremia have been recognized for decades and there has been considerable effort in the past decade to better define the extent and mechanisms of impaired defenses. Despite the multitude of major defects in humoral, cellular, and inflammatory processes, uremic patients who are cared for today, although they remain at higher risk of serious infectious complications, can and do maintain a good quality of life, with most remaining free of major infections for years and decades.

Zinc and the immune system

Zn is an essential trace element for all organisms. In human subjects body growth and development is strictly dependent on Zn. The nervous, reproductive and immune systems are particularly influenced by Zn deficiency, as well as by increased levels of Zn. The relationship between Zn and the immune system is complex, since there are four different types of influence associated with Zn. (1) The dietary intake and the resorption of Zn depends on the composition of the diet and also on age and disease status. (2) Zn is a cofactor in more than 300 enzymes influencing various organ functions having a secondary effect on the immune system. (3) Direct effects of Zn on the production, maturation and function of leucocytes. (4) Zn influences the function of immunostimulants used in the experimental systems. Here we summarize all four types of influence on the immune function. Nutritional aspects of Zn, the physiology of Zn, the influence of Zn on enzymes and cellular functions, direct effects of Zn on leucocytes at the cellular and molecular level, Zn-altered function of immunostimulants and the therapeutic use of Zn will be discussed in detail.