Selenium, systemic immune response syndrome, sepsis, and outcome in critically ill patients

Hierarchical regulation of selenoprotein expression and sex-specific effects of selenium

The expression of selenoproteins is controlled on each one of the textbook steps of protein biosynthesis, i.e., during gene transcription, RNA processing, translation and posttranslational events as well as via control of the stability of the involved intermediates and final products. Selenoproteins are unique in their dependence on the trace element Se which they incorporate as the 21st proteinogenic amino acid, selenocysteine. Higher mammals have developed unique pathways to enable a fine-tuned expression of all their different selenoproteins according to developmental stage, actual needs, and current availability of the trace element. Tightly controlled and dynamic expression patterns of selenoproteins are present in different tissues. Interestingly, these patterns display some differences in male and female individuals, and can be grossly modified during disease, e.g. in cancer, inflammation or neurodegeneration. Likewise, important health issues related to the selenium status show unexpected sexual dimorphisms. Some detailed molecular insights have recently been gained on how the hierarchical Se distribution among the different tissues is achieved, how the selenoprotein biosynthesis machinery discriminates among the individual selenoprotein transcripts and how impaired selenoprotein biosynthesis machinery becomes phenotypically evident in humans. This review tries to summarize these fascinating findings and highlights some interesting and surprising sex-specific differences.

On the importance of selenium and iodine metabolism for thyroid hormone biosynthesis and human health

The trace elements iodine and selenium (Se) are essential for thyroid gland functioning and thyroid hormone biosynthesis and metabolism. While iodine is needed as the eponymous constituent of the two major thyroid hormones triiodo-L-thyronine (T3), and tetraiodo-L-thyronine (T4), Se is essential for the biosynthesis and function of a small number of selenocysteine (Sec)-containing selenoproteins implicated in thyroid hormone metabolism and gland function. The Se-dependent iodothyronine deiodinases control thyroid hormone turnover, while both intracellular and secreted Se-dependent glutathione peroxidases are implicated in gland protection. Recently, a number of clinical supplementation trials have indicated positive effects of increasing the Se status of the participants in a variety of pathologies. These findings enforce the notion that many people might profit from improving their Se status, both as a means to reduce the individual health risk as well as to balance a Se deficiency which often develops during the course of illness. Even though the underlying mechanisms are still largely uncharacterised, the effects of Se appear to be exerted via multiple different mechanisms that impact most pronounced on the endocrine and the immune systems.

Down-regulation of the hepatic selenoprotein biosynthesis machinery impairs selenium metabolism during the acute phase response in mice

The acute-phase response (APR) is characterized by an impaired metabolism of the essential trace element selenium (Se). Moreover, low-Se concentrations correlate to mortality risk in sepsis. Therefore, we analyzed the expression of the central Se transport and storage protein selenoprotein P (Sepp1) during an APR in mice. Serum Se and Sepp1 concentrations declined in parallel after injection of lipopolysaccharide to 50 and 39% of control-injected littermates, respectively. This negative APR proceeded largely independent from hepatic Sepp1 transcript concentrations. Instead, we identified a set of hepatic transcripts involved in Se metabolism, which declined coordinately during the APR, including the selenocysteine-specific elongation factor (EFsec), selenophosphate-synthetase 2 (Sephs2), selenocysteine-tRNA[Ser]Sec synthase (SecS), and phosphoseryl-tRNA[Ser]Sec kinase (Pstk). Pstk reacted most strongly and qualified as a new limiting factor for Sepp1 biosynthesis in siRNA-mediated knockdown experiments in hepatocytes in culture. Analogous experiments were performed with mice transgenic for hepatocyte-specific human Sepp1 cDNA to verify this hypothesis. Similar kinetics and effect sizes of Sepp1 expression were observed as before in wild-type mice. We conclude that hepatic translation of Sepp1 mRNA is specifically impaired during the APR. This deficit disrupts regular Se metabolism, transport, and supply to peripheral tissues and likely aggravates the pathological status.

Selenium and thyroid hormone axis in critical ill states: an overview of conflicting view points

In critical ill states the plasma selenium levels are low and inversely correlated with the severity and outcome of the disease. The plasma selenium levels indicate the amount of circulating selenoproteins and selenoenzymes. These are important for the maintenance of the redox system, modulating the immune system and also for thyroid hormone metabolism. Not only all three deiodinases (D1-3) are selenoenzymes, but within the thyroid gland there are several other selenoenzymes, which are important for the maintenance of normal thyroid function. In critical ill states also triodothyronine (T3) is low and reverse T3 elevated, and also TSH and thyroxin (T4) are low, correlating like low plasma selenium with the severity of the disease. Subsequently, several intervention trials had been performed to evaluate whether an adjuvant selenium supplementation might attenuate the course of the disease and improve outcome. The selenium supplementation improved outcome and even reduced mortality in some but not all prospective randomized trials. A few prospective randomized intervention trials with selenium supplementation had also been performed to evaluate the hypothesis, whether low selenium is the cause of low-T3-syndrome, however, with conflicting results and no clear evidence that low D1 activity is due to the selenium deficiency in critical illness. Because D1 catalyses the conversion of T4 to T3 and also the clearance of reverse T3, low D1 activity would sufficiently explain low plasma T3 and elevated reverse T3. It had been, however, clearly shown that cytokines are responsible for the inhibition of D1 activity, but D2 and D3 are even higher during acute inflammation in critically ill patients. One of the most important effects of selenium on the immune system seems to be the reduction of cytokine release and therefore an indirect connection between low selenium and low D1 activity has to be postulated and not a lower D1 activity due to lower availability of selenium for the D1 expression.

Selenium in Critically Ill Patients

There is increasing evidence that particular nutritional substrates may be important in critically ill patients and in recent years there has been growing interest in selenium. This review aims to outline the incidence of selenium deficiency in critically ill patients, the consequences of such a deficiency and present the evidence for, and effect of, selenium supplementation in these patients. Selenium levels fall during periods of oxidative stress as occurs in critically ill patients with conditions such as severe sepsis, burns, and following trauma. Data from individual studies and meta-analyses suggests that selenium is an important adjuvant therapy in certain critically ill patients and supplementation of selenium may offer a mortality benefit.

Novel Approaches to the Treatment of Sepsis Syndrome

Sepsis, severe sepsis, and septic shock are common diagnoses in intensive care units worldwide. In the United States, it is estimated that 750 000 cases of sepsis occur annually. This rate is expected to climb, with an additional 1 million cases per year expected by 2020. These infection-induced inflammatory syndromes ultimately lead to organ dysfunction, and a significantly high mortality rate. Recently, advances in knowledge of sepsis syndrome have led to progress in identifying potential treatment options beyond our current standards of care. Many health care facilities have implemented protocols to guide clinicians to use such standards: early goal-directed therapy and activated protein C therapy in qualifying patients. Nonetheless, debate continues to confuse identification of patient populations in whom corticosteroid therapy should be recommended. While the data describing studies of novel treatment approaches has been controversial in some cases, there have been promising results observed in others. Here we review several treatments that have recently gained attention in the medical literature: HMG-CoA reductase inhibitors (statins), selenium therapy, immunoglobulin therapy, and several agents currently in preclinical study.

Influence of early antioxidant supplements on clinical evolution and organ function in critically ill cardiac surgery, major trauma, and subarachnoid hemorrhage patients

Introduction

Oxidative stress is involved in the development of secondary tissue damage and organ failure. Micronutrients contributing to the antioxidant (AOX) defense exhibit low plasma levels during critical illness. The aim of this study was to investigate the impact of early AOX micronutrients on clinical outcome in intensive care unit (ICU) patients with conditions characterized by oxidative stress.

Methods

We conducted a prospective, randomized, double-blind, placebo-controlled, single-center trial in patients admitted to a university hospital ICU with organ failure after complicated cardiac surgery, major trauma, or subarachnoid hemorrhage. Stratification by diagnosis was performed before randomization. The intervention was intravenous supplements for 5 days (selenium 270 μg, zinc 30 mg, vitamin C 1.1 g, and vitamin B₁ 100 mg) with a double-loading dose on days 1 and 2 or placebo.

Results

Two hundred patients were included (102 AOX and 98 placebo). While age and gender did not differ, brain injury was more severe in the AOX trauma group (P = 0.019). Organ function endpoints did not differ: incidence of acute kidney failure and sequential organ failure assessment score decrease were similar (-3.2 ± 3.2 versus -4.2 ± 2.3 over the course of 5 days). Plasma concentrations of selenium, zinc, and glutathione peroxidase, low on admission, increased significantly to within normal values in the AOX group. C-reactive protein decreased faster in the AOX group (P = 0.039). Infectious complications did not differ. Length of hospital stay did not differ (16.5 versus 20 days), being shorter only in surviving AOX trauma patients (-10 days; P = 0.045).

Conclusion

The AOX intervention did not reduce early organ dysfunction but significantly reduced the inflammatory response in cardiac surgery and trauma patients, which may prove beneficial in conditions with an intense inflammation.

Trials Registration

Clinical Trials.gov RCT Register: NCT00515736.

Role of Zinc and Selenium in Oxidative Stress and Immunosenescence: Implications for Healthy Ageing and Longevity

Ageing is an inevitable biological process with gradual and spontaneous biochemical and physiological changes and increased susceptibility to diseases. Some nutritional factors (zinc and selenium) may remodel these changes leading to a possible escaping of diseases with subsequent healthy ageing, because they are especially involved in improving immune functions as well as antioxidant defense. Experiments performed “in vitro” (human lymphocytes exposed to endotoxins) and “in vivo” (old mice or young mice fed with low zinc dietary intake) show that zinc is important for immune response both innate and adoptive. Selenium provokes zinc release by Metallothioneins (MT), via reduction of glutathione peroxidase. This fact is crucial in ageing because high MT may be unable to release zinc with subsequent low intracellular free zinc ion availability for immune response. Taking into account the existence of zinc transporters (ZnT and ZIP family) for cellular zinc efflux and influx, respectively, the association between ZnT and MT is important in maintaining satisfactory intracellular zinc homeostasis in ageing. Improved immune performance occur in elderly after physiological zinc supplementation, which also induces prolonged survival in old, nude and neonatal thymectomized mice. The association “zinc plus selenium” improves humoral immunity in old subjects after influenza vaccination. Therefore, zinc and selenium are relevant for immunosenescence in order to achieve healthy ageing and longevity.

Effects of high doses of selenium, as sodium selenite, in septic shock: a placebo-controlled, randomized, double-blind, phase II study

INTRODUCTION

Sepsis is associated with the generation of oxygen free radicals and (lacking) decreased selenium plasma concentrations. High doses of sodium selenite might reduce inflammation by a direct pro-oxidative effect and may increase antioxidant cell capacities by selenium incorporation into selenoenzymes. We investigated the effects of a continuous administration of high doses of selenium in septic shock patients.

METHODS

A prospective, multicentre, placebo-controlled, randomized, double-blind study was performed with an intention-to-treat analysis in severe septic shock patients with documented infection. Patients received, for 10 days, selenium as sodium selenite (4,000 microg on the first day, 1,000 microg/day on the nine following days) or matching placebo using continuous intravenous infusion. The primary endpoint was the time to vasopressor therapy withdrawal. The duration of mechanical ventilation, the mortality rates in the intensive care unit, at hospital discharge, and at 7, 14, 28 and 180 days and 1 year after randomization, and adverse events were recorded.

RESULTS

Sixty patients were included (placebo, n = 29; selenium, n = 31). The median time to vasopressor therapy withdrawal was 7 days in both groups (95% confidence interval = 5-8 and 6-9 in the placebo and selenium groups, respectively; log-rank, P = 0.713). The median duration of mechanical ventilation was 14 days and 19 days in the placebo and selenium groups, respectively (P = 0.762). Mortality rates did not significantly differ between groups at any time point. Rates of adverse events were similar in the two groups.

CONCLUSION

Continuous infusion of selenium as sodium selenite (4,000 microg on the first day, 1,000 microg/day on the nine following days) had no obvious toxicity but did not improve the clinical outcome in septic shock patients. Trial Registration = NCT00207844.

Pharmaconutrition: a new emerging paradigm

PURPOSE OF REVIEW

This paper highlights recent studies of interest and provides rationale for why deficiencies with the current scientific paradigm of immunonutrition has produced studies with conflicting results, and why it should be replaced with a new paradigm termed 'pharmaconutrition'.

RECENT FINDINGS

Considering the overall treatment effect of immune-modulating nutrients, parenteral glutamine is recommended in patients receiving parenteral nutrition, while enteral glutamine should be considered in burn and trauma patients. Antioxidants, particularly selenium, should be considered for critically ill patients, and enteral formulas enriched with fish oils are recommended in patients with acute respiratory distress syndrome. Arginine-supplemented diets are not recommended. There are currently insufficient data to enable useful recommendations on the optimal route, timing, duration and dosage of each nutrient. The pending results of a large, rigorously designed, randomized trial, however, in which nutrients are viewed and tested as pharmacological agents, promise to clarify some of the current ambiguities and inform future practice.

SUMMARY

This review provides insights into why the current paradigm of immunonutrition has failed to consistently demonstrate a beneficial effect of key immunomodulating nutrients, and offers a timely solution through the new paradigm of pharmaconutrition.

Effect of age on sexually dimorphic selenoprotein expression in mice

Clinical data suggest that selenium (Se) supplementation decreases disease predisposition and severity and accelerates recovery in a variety of pathologies. Pre-supplementation Se levels and sex represent important determinants of these Se-dependent health effects. Accordingly, we previously reported on sexually dimorphic expression patterns of Se-dependent glutathione peroxidase 1, type I deiodinase, and selenoprotein P in young mice. In the present study we investigated whether these differences vary with age. The strong sexual dimorphic expression of hepatic type I deiodinase that was observed in young mice vanished both at the mRNA and enzyme activity level by 1 year of age. In contrast, the strong sex-specific differences in renal type I deiodinase mRNA expression were sustained with age. Accordingly, deiodinase enzymatic activities differed in male and female kidneys, largely independent of age [average of 6.8 vs. 15.7 pmol/(min mg) in males vs. females]. In parallel, hepatic Se concentrations and glutathione peroxidase activities increased in female mice compared to male littermates, establishing a new sexual dimorphism in liver. Thus, age represents another important modifier of the dynamic sex- and tissue-specific selenoprotein expression patterns. These data highlight again the unique physiological regulatory mechanisms that have evolved to control Se metabolism according to the actual needs of the organism.

Low serum alpha-tocopherol and selenium are associated with accelerated apoptosis in severe sepsis

During sepsis, a severe systemic disorder, micronutrients often are decreased. Apoptosis is regarded as an important mechanism in the development of often significant immunosuppression in the course of the disease. This study aimed to investigate alpha-tocopherol and selenium in reference to apoptosis in patients with sepsis. 16 patients were enrolled as soon as they fulfilled the criteria of severe sepsis. 10 intensive care patients without sepsis and 11 healthy volunteers served as controls. alpha-Tocopherol, selenium and nucleosomes were measured in serum. Phosphatidylserine externalization and Bcl-2 expression were analyzed in T-cells by flow cytometry. Serum alpha-tocopherol and selenium were decreased in severe sepsis but not in non-septic critically ill patients (p < 0.05). Conversely, markers of apoptosis were increased in sepsis but not in critically ill control patients: Nucleosomes were found to be elevated 3 fold in serum (p < 0.05) and phosphatidylserine was externalized on an expanded subpopulation of T-cells (p < 0.05) while Bcl-2 was expressed at lower levels (p < 0.05). The decrease of micronutrients correlated with markers of accelerated apoptosis. Accelerated apoptosis in sepsis is associated with low alpha-tocopherol and selenium. The results support the investigation of micronutrient supplementation strategies in severe sepsis.

New assay for the measurement of selenoprotein P as a sepsis biomarker from serum

Selenium (Se) is incorporated into selenoproteins as the 21st proteinogenic amino acid selenocysteine. Serum Se concentrations decline during critical illness and are indicative of poor prognosis. Serum Se is mainly contained in the hepatically derived selenoprotein P (SePP) which controls the expression of antioxidative selenoproteins. Here, we describe the development of an immunoluminometric sandwich assay that uses two polyclonal sheep antihuman SePP antibodies. After assessing the stability of the analyte, we determined SePP concentrations in samples from healthy individuals and patients with sepsis. The analytical detection limit was 0.016 mg SePP/L serum. The assay was linear on dilution. SePP was stable in serum at room temperature for at least 24 h and resistant to six freeze-thaw cycles. Median SePP concentration in healthy individuals was 3.04 mg SePP/L serum (25th-75th percentiles, 2.6-3.4 mg/L) which corresponded to 98.4 microg Se/L serum. The interlaboratory CV was <20% for SePP values >0.06 mg/L. There was no association with gender, but concentrations differed between young and older individuals. Median SePP concentrations were significantly (P<0.0001) decreased in patients with sepsis (n=60) compared to healthy controls (n=318). Since SePP contains the major fraction of serum Se, we conclude that downregulation of SePP biosynthesis or removal of circulating SePP from blood underlies the negative acute phase response of serum Se in critical illness.

Antioxidant supplementation in sepsis and systemic inflammatory response syndrome

OBJECTIVE

Summarize the current knowledge about oxidative stress-related organ dysfunction in inflammatory and septic conditions, and its potential prevention and treatment by antioxidants in critically ill patients, focusing on naturally occurring antioxidants and clinical trials.

STUDY SELECTION

PubMed, MEDLINE, and personal database search.

SYNTHESIS

Plasma concentrations of antioxidant micronutrients are depressed during critical illness and especially during sepsis. The causes of these low levels include losses with biological fluids, low intakes, dilution by resuscitation fluids, as well as systemic inflammatory response syndrome-mediated redistribution of micronutrients from plasma to tissues. Numerous clinical trials have been conducted, many of which have shown beneficial effects of supplementation. Interestingly, among the candidates, glutamine, glutathione, and selenium are linked with the potent glutathione peroxidase enzyme family at some stage of their synthesis and metabolism.

CONCLUSIONS

Three antioxidant nutrients have demonstrated clinical benefits and reached level A evidence: a) selenium improves clinical outcome (infections, organ failure); b) glutamine reduces infectious complication in large-sized trials; and c) the association of eicosapentaenoic acid and micronutrients has significant anti-inflammatory effects. Other antioxidants are still on the clinical benchmark level, awaiting well-designed clinical trials.

Selenium supplementation increases liver MnSOD expression: molecular mechanism for hepato-protection

Selenium is recognized as essential in animal and human nutrition. Several hypotheses have been advanced for its biological activity. The aim of this study was to investigate the in vivo effect of selenium on rat liver manganese superoxide dismutase (MnSOD), a key antioxidant enzyme, under naïve and inflammatory conditions. Rats received sodium selenite supplementation and LPS injection. Whole-liver samples, isolated hepatocytes, Kupffer cells and blood samples were subjected to protein, RNA and biochemical analysis. Liver enrichment with selenium increased whole-liver MnSOD levels due to an increase in MnSOD transcription in hepatocytes. This was due to an increase in the ratio of specificity protein 1 to activating enhancer binding protein 2 DNA-binding activity. The inflammatory stimulus further elevated MnSOD levels in the whole-liver that was abrogated in sodium selenite supplementation due to reduced transcription of MnSOD in Kupffer cells. Moreover, selenium enrichment decreased Kupffer cells IL-6 transcription in LPS-injected animals. Anti-inflammatory activity of selenium was demonstrated by normalized blood levels of ALT and IL-6 in LPS-injected animals. In conclusion, selenium up-regulates hepatocytes MnSOD expression, probably improving their anti-oxidant defense, while decreasing MnSOD and IL-6 transcription in Kupffer cells in the presence of inflammatory stimuli, attenuating their inflammatory response. This selective mechanism may explain the anti-inflammatory and hepato-protective effect of selenium.

New evaluation therapies for sepsis

This article presents an analysis of the literature of the last 2 years on the treatment of sepsis and septic shock. It appears that most of the antimediator therapies applied in phase II or III clinical trials yielded disappointing results. But, many other therapeutic approaches are proposed or are ongoing, and many papers report critical analysis of the reasons for the lack of success of past clinical trials.

Nutritional interventions in critical illness

The metabolism of critical illness is characterised by a combination of starvation and stress. There is increased production of cortisol, catecholamines, glucagon and growth hormone and increased insulin-like growth factor-binding protein-1. Phagocytic, epithelial and endothelial cells elaborate reactive oxygen and nitrogen species, chemokines, pro-inflammatory cytokines and lipid mediators, and antioxidant depletion ensues. There is hyperglycaemia, hyperinsulinaemia, hyperlactataemia, increased gluconeogenesis and decreased glycogen production. Insulin resistance, particularly in relation to the liver, is marked. The purpose of nutritional support is primarily to save life and secondarily to speed recovery by reducing neuropathy and maintaining muscle mass and function. There is debate about the optimal timing of nutritional support for the patient in the intensive care unit. It is generally agreed that the enteral route is preferable if possible, but the dangers of the parenteral route, a route of feeding that remains important in the context of critical illness, may have been over-emphasised. Control of hyperglycaemia is beneficial, and avoidance of overfeeding is emphasised. Growth hormone is harmful. The refeeding syndrome needs to be considered, although it has been little studied in the context of critical illness. Achieving energy balance may not be necessary in the early stages of critical illness, particularly in patients who are overweight or obese. Protein turnover is increased and N balance is often negative in the face of normal nutrient intake; optimal N intakes are the subject of some debate. Supplementation of particular amino acids able to support or regulate the immune response, such as glutamine, may have a role not only for their potential metabolic effect but also for their potential antioxidant role. Doubt remains in relation to arginine supplementation. High-dose mineral and vitamin antioxidant therapy may have a place.

Time course and relationship between plasma selenium concentrations, systemic inflammatory response, sepsis, and multiorgan failure

BACKGROUND

Selenium plays an important role in defence against acute illness. We investigated, in intensive care unit (ICU) patients, the time course of plasma selenium concentrations and their relationship to systemic inflammatory response syndrome (SIRS), organ dysfunction/failure, infection, and ICU outcome.

METHODS

Plasma selenium and laboratory indices of organ dysfunction/failure, tissue inflammation, and infection were measured daily during the ICU stay in 60 consecutive ICU patients, 15 in each of four a priori defined subgroups: ICU controls (no SIRS); uncomplicated SIRS; severe SIRS; and severe sepsis/septic shock.

RESULTS

Plasma selenium concentrations were below standard values for healthy subjects (74 microg litre(-1)) in 55 patients (92%). Selenium concentrations decreased during the ICU stay in all groups, except controls, to a minimum value that was lower in patients with organ failure, particularly in those with infection. The minimum plasma selenium was inversely correlated to admission Acute Physiology and Chronic Health Evaluation II and Simplified Acute Physiology System II scores, indicators of inflammation, and the maximal degree of organ dysfunction/failure during the ICU stay. Plasma selenium was positively correlated with minimum platelet count, minimum plasma antithrombin activity, and protein C activity. In a receiver operator characteristic analysis, SAPS II score [area under the curve (AUC) = 0.903] and minimum selenium concentration (AUC = 0.867) were the strongest predictive factors for ICU mortality.

CONCLUSIONS

In critically ill surgical patients, plasma selenium concentrations are generally low with a greater decrease during the ICU stay in patients with organ failure, especially when attributed to infection. Lower plasma selenium concentrations are associated with more tissue damage, the presence of infection or organ dysfunction/failure, and increased ICU mortality.

Seleno-enzymes and seleno-compounds: the two faces of selenium

Selenium protects cells and inhibits many inflammatory cell mechanisms through antioxidant seleno-enzymes. Immunity improvement is illustrated by the study of Berger and colleagues, with reduction of nosocomial pneumonia in burnt patients under multi-trace-element supplementation. As seleno-compounds (especially sodium selenite) are pro-oxidant, however, administration above 800 μg/day may be dangerous in septic shock. Paradoxically, direct reversible pro-oxidative effects of seleno-compounds may also be beneficial for reduction of inflammation (genomic action, apoptosis), and may even be bactericidal or virucidal. These facts need to be further examined, as well as the possible dramatic drop of plasma selenoprotein P in septic shock and its role in endothelium protection.

Reduction of nosocomial pneumonia after major burns by trace element supplementation: aggregation of two randomised trials

Introduction

Nosocomial pneumonia is a major source of morbidity and mortality after severe burns. Burned patients suffer trace element deficiencies and depressed antioxidant and immune defences. This study aimed at determining the effect of trace element supplementation on nosocomial or intensive care unit (ICU)-acquired pneumonia.

Methods

Two consecutive, randomised, double-blinded, supplementation studies including two homogeneous groups of 41 severely burned patients (20 placebo and 21 intervention) admitted to the burn centre of a university hospital were combined. Intervention consisted of intravenous trace element supplements (copper 2.5 to 3.1 mg/day, selenium 315 to 380 μg/day, and zinc 26.2 to 31.4 mg/day) for 8 to 21 days versus placebo. Endpoints were infections during the first 30 days (predefined criteria for pneumonia, bacteraemia, wound, urine, and other), wound healing, and length of ICU stay. Plasma and skin (study 2) concentrations of selenium and zinc were determined on days 3, 10, and 20.

Results

The patients, 42 ± 15 years old, were burned on 46% ± 19% of body surface: the combined characteristics of the patients did not differ between the groups. Plasma trace element concentrations and antioxidative capacity were significantly enhanced with normalisation of plasma selenium, zinc, and glutathione peroxidase concentrations in plasma and skin in the trace element-supplemented group. A significant reduction in number of infections was observed in the supplemented patients, which decreased from 3.5 ± 1.2 to 2.0 ± 1.0 episodes per patient in placebo group (p < 0.001). This was related to a reduction of nosocomial pneumonia, which occurred in 16 (80%) patients versus seven (33%) patients, respectively (p < 0.001), and of ventilator-associated pneumonia from 13 to six episodes, respectively (p = 0.023).

Conclusion

Enhancing trace element status and antioxidant defences by selenium, zinc, and copper supplementation was associated with a decrease of nosocomial pneumonia in critically ill, severely burned patients.

REducing Deaths due to OXidative Stress (The REDOXS Study): Rationale and study design for a randomized trial of glutamine and antioxidant supplementation in critically-ill patients

Critically-ill patients experience an extent of hyperinflammation, cellular immune dysfunction, oxidative stress and mitochondrial dysfunction. Supplementation with key nutrients, such as glutamine and antioxidants, is most likely to have a favourable effect on these physiological derangements, leading to an improvement in clinical outcomes. The results of two meta-analyses suggest that glutamine and antioxidants may be associated with improved survival. The purpose of the present paper is to report the background rationale and study protocol for the evaluation of the effect of high-dose glutamine and antioxidant supplementation on mortality in a large-scale randomized trial in 1200 mechanically-ventilated, critically-ill patients. Patients admitted to an intensive care unit (ICU) with clinical evidence of severe organ dysfunction will be randomized to one of four treatments in a 2 x 2 factorial design: (1) glutamine; (2) antioxidant therapy; (3) glutamine and antioxidant therapy; (4) placebo. The primary outcome for this study is 28 d mortality. The secondary outcomes are duration of stay in ICU, adjudicated diagnosis of infection, multiple organ dysfunction, duration of mechanical ventilation, length of stay in hospital and health-related quality of life at 3 and 6 months. A novel design feature is the combined use of parenteral and enteral study nutrients dissociated from the nutrition support. The therapeutic strategies tested in the randomized trial may lead to less morbidity and improved survival in critically-ill patients. The trial will be conducted in approximately twenty tertiary-care ICU in Canada and the first results are expected in 2009.

Effects of high doses of selenium, as sodium selenite, in septic shock patients a placebo-controlled, randomized, double-blind, multi-center phase II study--selenium and sepsis

Selenium has a double action. (i) Seleno-compounds, among them sodium selenite have a direct pro-oxidant action leading to acute toxicity but may be also beneficial as drug. (ii) Selenium is an essential anti-oxidant required for anti-oxidant seleno-enzymes. Septic shock is a common severe syndrome leading to endothelium damage and multiple organ failure, with increased data suggesting the principle role of oxidative stress. Selenoprotein P, main selenium constituent of the plasma, may decrease dramatically and specifically in septic shock patients and may be involved in the endothelium protection. A prospective, multi-center placebo-controlled, randomized, double-blind study in severe septic shock patients with documented infection has been preformed. Patients received, for 10 days, selenium as sodium selenite (4000 microg on the first day, 1000 microg/day on the 9 following days) or matching placebo using continuous intravenous infusion. Mortality rates did not significantly differ between groups at any time point. Adverse events rates were similar in the two groups. However, high-dose selenium administration has been associated with a tendency to decrease the mortality in septic shock animal and patients, especially when using a bolus administration, whereas studies using a continuous administration failed to find any benefit on mortality. The interest of the successive use of pro-oxidant action of seleno-compounds, followed by anti-oxidant action need to be the further studied in cellular and animal models, preceding new dose-effect phase II. The interest of the selenoprotein-P as a marker of septic shock and for endothelium protection needs also to be studied further.

Selenium in Intensive Care (SIC): Results of a prospective randomized, placebo-controlled, multiple-center study in patients with severe systemic inflammatory response syndrome, sepsis, and septic shock*

OBJECTIVE

Sepsis is associated with an increase in reactive oxygen species and low endogenous antioxidative capacity. We postulated that high-dose supplementation of sodium-selenite would improve the outcome of patients with severe sepsis and septic shock.

DESIGN

Prospective randomized, placebo-controlled, multiple-center trial.

SETTING

Eleven intensive care units in Germany.

PATIENTS

Patients were 249 patients with severe systemic inflammatory response syndrome, sepsis, and septic shock and an Acute Physiology and Chronic Health Evaluation (APACHE) III score >70.

INTERVENTIONS

Patients received 1000 microg of sodium-selenite as a 30-min bolus injection, followed by 14 daily continuous infusions of 1000 microg intravenously, or placebo.

MEASUREMENTS AND MAIN RESULTS

The primary end point was 28-day mortality; secondary end points were survival time and clinical course of APACHE III and logistic organ dysfunction system scores. In addition, selenium levels in serum, whole blood, and urine as well as serum glutathione-peroxidase-3 activity were measured. From 249 patients included, 11 patients had to be excluded. The intention-to-treat analysis of the remaining 238 patients revealed a mortality rate of 50.0% in the placebo group and 39.7% in the selenium-treated group (p = .109; odds ratio, 0.66; confidence interval, 0.39-1.1). A further 49 patients had to be excluded before the final analysis because of severe violations of the study protocol. In the remaining 92 patients of the study group, the 28-day mortality rate was significantly reduced to 42.4% compared with 56.7% in 97 patients of the placebo group (p = .049, odds ratio, 0.56; confidence interval, 0.32-1.00). In predefined subgroup analyses, the mortality rate was significantly reduced in patients with septic shock with disseminated intravascular coagulation (n = 82, p = .018) as well as in the most critically ill patients with an APACHE III score > or =102 (>75% quartile, n = 54, p = .040) or in patients with more than three organ dysfunctions (n = 83, p = .039). Whole blood selenium concentrations and glutathione peroxidase-3 activity were within the upper normal range during selenium treatment, whereas they remained significantly low in the placebo group. There were no side effects observed due to high-dose sodium-selenite treatment.

CONCLUSIONS

The adjuvant treatment of patients with high-dose sodium-selenite reduces mortality rate in patients with severe sepsis or septic shock.

Effect of selenium supplementation on biochemical markers and outcome in critically ill patients

BACKGROUND & AIMS

This study aimed to assess the effect of high dose selenium (Se) supplementation on Se status in blood, oxidative stress, thyroid function and possible effects on requirement for renal replacement therapy (RRT) in severely septic patients admitted to the intensive care unit (ICU).

METHODS

This prospective single-centre study was carried out in 40 septic ICU patients who were randomized to high dose Se (Se+ group, N=18 (474, 316, 158 microg/day), each for 3 consecutive days followed by a standard dose of 31.6 microg/day of Se given as sodium selenite whereas the control group (Se-, N=22) received only the standard dose of Se. Plasma Se, glutathione peroxidase (GSH-Px), F2 isoprostanes, thyroid function tests (total T4 and total T3), C-reactive protein (CRP) and red blood cell (RBC) GSH-Px were estimated on day 0, 3, 7, 14.

RESULTS

In the Se+ group, plasma Se increased by day 3 and 7 (P<0.0001) and day 14 (P=0.02), plasma GSH-Px increased by day 3 and 7 (P=0.01) as compared to Se- group. There was a significant negative correlation between plasma Se and SOFA (sepsis related organ failure assessment) (r=-0.36, P=0.03) along with low plasma Se and high CRP at the time of admission. Requirement for renal replacement therapy was not significantly different between the groups.

CONCLUSION

Although high dose Se supplementation increased plasma Se and GSH-Px activity, it did not reduce oxidative damage or the requirement for RRT. Se levels in blood are influenced by redistribution and severity of illness and therefore should be interpreted with caution.

Selenium in critical illness

PURPOSE OF REVIEW

Selenium is a trace element essential to human health. Critical illness is associated with the generation of oxygen free radicals resulting in a condition of oxidative stress. Supplementing critically ill patients with antioxidant nutrients may improve survival. Selenium levels can be low due to redistribution to high-priority organs and dilution associated with aggressive resuscitation of the patient. The purpose of this review is to investigate the benefit of selenium supplementation in critically ill patients.

RECENT FINDINGS

Most of the selenium-supplementation trials were performed in relatively small patient populations presenting with trauma, sepsis, burns and adult respiratory distress syndrome. Widely varying doses of selenium of between 200 and 1000 microg were used, either alone or in combination with other antioxidants. Significant improvements have been demonstrated in length of hospital stay, rate of infection and need for haemodialysis in these patients. However, no trial has demonstrated a statistically significant improvement in mortality. Two recent meta-analyses suggest a trend towards reduced mortality with selenium supplementation.

SUMMARY

Selenium, by supporting antioxidant function, may be associated with a reduction in mortality. To demonstrate this large, well-designed randomized trials are required.

Influence of selenium treatment on the acute toxicity of dibutyltin dichloride in rats

BACKGROUND/AIMS

Dibutyltin dichloride (DBTC) is an organotin compound used as a model for acute pancreatitis. The aim was to determine the effect of various doses of Na-selenite on the pathogenesis and course of DBTC-induced toxic changes in organs and serum of rats.

METHODS

Experimental pancreatitis was induced by intravenous administration of 6 mg kg(-1) BW DBTC. Na-selenite was applied as a single intravenous dose of 5 mg kg(-1) BW and as daily oral dose of 1 mg kg(-1) BW. Malondialdehyde (MDA) was detected to observe the level of oxidative stress. The tin concentration in bile and urine shows the elimination of DBTC. Organ changes were indicated by serum parameters as well as histology.

RESULTS

DBTC causes an acute pancreatitis, cholestasis and liver lesions determined by specific elevated serum parameters and several histological lesions. Na-selenite significantly diminished MDA concentration, lipase, bilirubin and transaminases as well as organ injuries compared to only DBTC-treated rats.

CONCLUSIONS

The treatment with Na-selenite in the scope of DBTC-induced pancreatitis points to a reduced oxidative stress characterized by diminished MDA serum levels and a milder course of pancreatitis. The generation of DBTC-Na-selenite complexes could also be a mechanism to decrease the toxicity of organotin compounds like DBTC.

Practicalities of selenium supplementation in critically ill patients

PURPOSE OF REVIEW

To review the reason for and clinical effects of selenium supplementation in critically ill patients.

RECENT FINDINGS

Selenium-dependent enzymes and selenoprotein P regulate immune and endothelial cell function. Obviously not the anorganic compounds of selenium but the activity of selenium-dependent enzymes is the most important factor modulating the immune system and the clinical outcome of patients. Despite low selenium levels in severely ill patients and low glutathione peroxidase activity associated with the extent of multiorgan dysfunction, only a few trials have investigated the effect of selenium supplementation on clinical outcome. A metaanalysis did not reveal a statistically significant survival rate with selenium supplementation, but suggested a dose-dependent trend. The recently completed multicentre trial on high-dose selenium supplementation in septic patients also did not reveal a significant overall reduction in mortality.

SUMMARY

The available evidence suggests that selenoproteins play an important role in the immunomodulation of critically ill patients and a sodium selenite supplementation upregulates these selenoenzymes. The intervention trials with sodium selenite performed to date are small and therefore only a tendency in reduction of morbidity and mortality could be demonstrated. Larger trials are necessary to show the supposed benefits and risks of selenite supplementation in critically ill patients.

The Relevance of Selenium to Immunity, Cancer, and Infectious/Inflammatory Diseases

Selenium is an essential trace element involved in several key metabolic activities via selenoproteins, enzymes that are essential to protect against oxidative damage and to regulate immune function. Selenium also may have other health benefits unrelated to its enzymatic functions. It may provide important health benefits to people whose oxidative stress loads are high, such as those with inflammatory or infectious diseases like rheumatoid arthritis or human immunodeficiency virus/acquired immunodeficiency syndrome, or who are at high risk for cancers, particularly prostate cancer. Some studies have generated compelling evidence that selenium is beneficial, either alone or in conjunction with other micronutrients. Additional data from large clinical trials that provide the highest level of evidence will be key to determining the benefits accrued at various selenium intake levels. When the strength of the evidence becomes sufficient, clinical health professionals will need to use dietary and clinical assessment methods to ensure that people at increased risk for cancer or inflammatory and infectious diseases can be appropriately advised about selenium intake.

Impact of vitamin E or selenium deficiency on nematode-induced alterations in murine intestinal function

The effects of deficiencies in the antioxidant nutrients, vitamin E and selenium, on the host response to gastrointestinal nematode infection are unknown. The aim of the study was to determine the effect of antioxidant deficiencies on nematode-induced alterations in intestinal function in mice. BALB/c mice were fed control diets or diets deficient in selenium or vitamin E and the response to a secondary challenge inoculation with Heligmosomoides polygyrus was determined. Egg and worm counts were assessed to determine host resistance. Sections of jejunum were mounted in Ussing chambers to measure changes in permeability, absorption, and secretion, or suspended in organ baths to determine smooth muscle contraction. Both selenium and vitamin E deficient diets reduced resistance to helminth infection. Vitamin E, but not selenium, deficiency prevented nematode-induced decreases in glucose absorption and hyper-contractility of smooth muscle. Thus, vitamin E status is an important factor in the physiological response to intestinal nematode infection and may contribute to antioxidant-dependent protective mechanisms in the small intestine.

Selenium attenuates expression of MnSOD and uncoupling protein 2 in J774.2 macrophages: molecular mechanism for its cell-death and antiinflammatory activity

Selenium can activate cell death. However, the mechanism of action is not yet fully defined. We hypothesized that selenium may impede mitochondrial superoxide dismutation to H2O2 and O2, leading to cell death in macrophages and that this effect may be relevant to antiinflammatory treatment by selenium. In this study, the mechanism of action of selenium was investigated in nonactivated and activated (immune-stimulated) J774.2 macrophages. Sodium selenite treatment decreased dichlorodihydrofluorescein-reacting intracellular reactive oxygen species (ROS) (mainly peroxides and hydroxyl radicals), with no correlation to glutathione peroxidase activity. However, selenite decreased the transcription and expression of manganese superoxide dismutase (MnSOD) and uncoupling protein 2 (UCP2). This cellular effect was due to inhibition of specificity protein-1 (Sp1) binding to its DNA binding site. Following immune stimulation of macrophages using lipopolysaccharides plus interferon-gamma, MnSOD was up-regulated. Activated macrophages showed higher mitochondrial membrane potential, intracellular ROS levels, and cellular resistance to cell death. Selenite treatment attenuated all of these parameters. Selenite prevented nuclear factor-kappaB (NF-kappaB) activation as a mechanism of its inhibitory activity on MnSOD expression in the immune-stimulated cells. In addition, overexpression of human MnSOD protected against death induced by selenite treatment. It is therefore concluded that selenium at high nanomolar to low micromolar concentrations shifts the balance between inflammatory response and cell death toward the latter, through a direct effect on the transcription factors Sp1 and NF-kappaB, and down-regulation of MnSOD and UCP2.

Antioxidant nutrients: a systematic review of trace elements and vitamins in the critically ill patient

OBJECTIVE

Critical illness is associated with the generation of oxygen free radicals and low endogenous antioxidant capacity leading to a condition of oxidative stress. We investigated whether supplementing critically ill patients with antioxidants, trace elements, and vitamins improves their survival.

METHODS

We searched four bibliographic databases from 1980 to 2003 and included studies that were randomized, reported clinically important endpoints in critically ill patients, and compared various trace elements and vitamins to placebo.

RESULTS

Eleven articles met the inclusion criteria. When the results of all the trials were aggregated, overall antioxidants were associated with a significant reduction in mortality [Risk Ratio (RR) 0.65, 95% confidence intervals (CI) 0.44-0.97, p=0.03] but had no effect on infectious complications. Studies that utilized a single trace element were associated with a significant reduction in mortality [RR 0.52, 95% CI 0.27-0.98, p=0.04] whereas combined antioxidants had no effect. Studies using parenteral antioxidants were associated with a significant reduction in mortality [RR 0.56, 95% CI 0.34-0,92, p=0.02] whereas studies of enteral antioxidants were not. Selenium supplementation (alone and in combination with other antioxidants) may be associated with a reduction in mortality [RR 0.59, 95% CI 0.32-1.08, p=0.09] while nonselenium antioxidants had no effect on mortality.

CONCLUSIONS

Trace elements and vitamins that support antioxidant function, particularly high-dose parenteral selenium either alone or in combination with other antioxidants, are safe and may be associated with a reduction in mortality in critically ill patients.

Selenium concentrations in maternal and umbilical cord blood at 24-42 weeks of gestation: basis for optimization of selenium supplementation to premature infants

BACKGROUND & AIMS

Selenium (Se) deficiency may have deleterious effects on premature infants. Umbilical cord (UC) Se concentrations presumably reflect fetal Se concentrations and represent reference values that should be achieved in premature infants. We aimed to establish reference data of Se serum concentrations in parturient women and their neonates across gestation.

SUBJECTS AND METHODS

Parturient mothers and their newborn infants born after 24-42 weeks of gestation were enrolled. Only appropriate for gestational age (GA) singleton infants were included. Se serum concentrations were measured by atomic absorption spectrometry, in blood samples from parturient mothers and their infants (umbilical blood). Demographic, perinatal and labor data were obtained, and their correlations with umbilical Se serum concentrations, maternal Se serum concentrations, and the maternal-umbilical Se difference were examined.

RESULTS

UC Se serum concentrations increased as gestation progressed (P<0.01). A statistically significant linear relationship was found between UC Se serum concentrations and GA (R=0.341, P<0.0001), birth weight (R=0.237, P=0.002), and 5-min Apgar score (R=0.202, P<0.01). Using multiple regression analysis, only GA was significantly associated with UC serum Se concentration (P=0.012). Maternal Se serum concentration were stable throughout gestation, and maternal-umbilical Se difference was negatively correlated with GA (R=-0.337, P<0.0001) and birth weight (R=-0.369, P<0.0001).

CONCLUSIONS

UC Se serum concentration increases and the maternal-umbilical Se difference declines with gestation progression, probably reflecting fetal accretion of Se. With the current Se supplementation in premature infants, Se concentrations are lower than those measured in our study. We, therefore, suggest a two-fold increase or more in the recommended Se dosage.

Assessing the antioxidative status in critically ill patients

PURPOSE OF REVIEW

Oxidative stress is caused by a higher production of reactive oxygen and reactive nitrogen species or a decrease in endogenous protective antioxidative capacity. In all types of critical illness, such as sepsis, trauma, burn injury, acute pancreatitis, liver injury, severe diabetes, acute respiratory distress syndrome, AIDS and kidney failure, the occurrence of increased oxidative stress or a reduced antioxidative status is described. Whereas in the past, reactive oxygen and reactive nitrogen species were mainly known as harmful agents, recent investigations have given a new insight into the (patho)physiological importance of these substances as powerful messenger molecules involved in gene regulation, thereby enabling the synthesis of cytokines or adhesion molecules necessary for defending inflammatory processes. As shown in this review, there are numerous possibilities for the quantification of oxidative stress.

RECENT FINDINGS

Several investigations showed a close association of single or multiple parameters, such as total antioxidative capacity, lipid peroxidation, vitamins C and E, the activation of nuclear factor kappa B, and respiratory burst, with the patient's outcome. However, no recommendation for a single parameter to be measured can be given because the assays described do not allow the definition of an overall "antioxidative status" for patients.

SUMMARY

The occurrence of oxidative stress in critically ill patients is associated with a poor prognosis. The measurement of a cluster of assays representative of the quantification of reactive species or of antioxidants may improve the usefulness of therapeutic intervention and increase knowledge of pathophysiological alterations.

Immune cells: free radicals and antioxidants in sepsis

The excessive production of reactive oxygen species (ROS), associated with inflammation, leads to a condition of oxidative stress. Oxidative stress is a major contributing factor to the high mortality rates associated with several diseases such as endotoxic shock. This condition can be controlled to a certain degree by antioxidant therapies. Immune cells use ROS in order to support their functions and therefore need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive production of ROS. This review discusses the toxic effects of endotoxin, paying particular attention to immune function. It continues by analyzing the mechanism to which specific cells of the immune system recognize endotoxin, and the resulting pathways leading to nuclear factor-kappaB activation and proinflammatory gene transcription. We also focus on the involvement of reactive oxygen and nitric oxide (NO) and the protective role of antioxidants. The potential clinical use of antioxidants in the treatment of sepsis and the effects on the redox state of the immune cells are discussed.

Skeletal muscle disorders associated with selenium deficiency in humans

Skeletal muscle disorders manifested by muscle pain, fatigue, proximal weakness, and serum creatine kinase (CK) elevation have been reported in patients with selenium deficiency. The object of this report was to review the conditions in which selenium deficiency is associated with human skeletal muscle disorders and to evaluate the importance of mitochondrial alterations in these disorders. A systematic literature review using the Medline database and Cochrane Library provided 38 relevant articles. The main conditions associated with selenium deficiency fell into three categories: (1) insufficient selenium intake in low soil-selenium areas; (2) parenteral or enteral nutrition, or malabsorption; and (3) chronic conditions associated with oxidative stress, such as chronic alcohol abuse and human immunodeficiency virus (HIV) infection. In low soil-selenium areas, reversibility of muscle symptoms was similar after selenium supplementation and placebo administration, suggesting a role for other factors in the development of disease. In parenteral or enteral nutrition, or malabsorption, muscle symptoms improved after selenium supplementation in 18 of 19 patients (median delay: 4 weeks). The reason that only a minority of selenium-deficient patients present with skeletal muscle disorders is unclear and is possibly related to cofactors, such as viral infections and drugs. Prospective studies of selenium-deficient myopathies would be useful in critically ill patients, alcohol abusers, and HIV-infected patients.

Anti-inflammatory strategies for the treatment of sepsis

Sepsis leads to an overwhelming inflammatory response of the host and is usually accompanied by well-known clinical symptoms (fever, tachycardia, leukocytosis, and so on) and the accompanying systemic inflammatory response syndrome (SIRS). Accordingly, most efforts to develop treatment strategies for sepsis have focused on those designed to counteract overactivation of the inflammatory system. Despite intensive research into identifying targets in sepsis, most of the resulting clinical trials have been based on experimental data and have resulted in no beneficial effects (i.e., survival). Recombinant activated protein C (APC) represents the first treatment that has led to restricted approval for use in sepsis in the USA and worldwide. This article reviews approaches to anti-inflammatory treatment in sepsis and provides an outlook into ongoing clinical trials as well as new treatments that have not yet been evaluated in the clinical setting.

Oxidative stress and gene expression in sepsis

Dysregulation of the immuno-inflammatory response, as seen in sepsis, may culminate in host cell and organ damage. Lipopolysaccharide from Gram-negative bacterial cell walls induces gene activation and subsequent inflammatory mediator expression. Gene activation is regulated by a number of transcription factors at the nuclear level, of which nuclear factor kappaB appears to have a central role. The redox (reduction-oxidation) cellular balance is important for normal cellular function, including transcription factor regulation. In sepsis, a state of severe oxidative stress is encountered, with host endogenous antioxidant defences overcome. This has implications for cellular function and the regulation of gene expression. This review gives an overview of the mechanisms by which transcription factor activation and inflammatory mediator overexpression occur in sepsis, together with the events surrounding the state of oxidative stress encountered and the effects on the host's antioxidant defences. The effect of oxidative stress on transcription factor regulation is considered, together with the role of antioxidant repletion in transcription factor activation and in sepsis in general. Other interventions that may modulate transcription factor activation are also highlighted.