Selenium deficiency

Understanding How Minerals Contribute to Optimal Immune Function

Sufficient mineral supply is vital not only for the innate immune system but also for the components of the adaptive immune defense, which encompass defense mechanisms against pathogens and the delicate balance of pro- and anti-inflammatory regulation in the long term. Generally, a well-balanced diet is capable of providing the necessary minerals to support the immune system. Nevertheless, specific vulnerable populations should be cautious about obtaining adequate amounts of minerals such as magnesium, zinc, copper, iron, and selenium. Inadequate levels of these minerals can temporarily impair immune competence and disrupt the long-term regulation of systemic inflammation. Therefore, comprehending the mechanisms and sources of these minerals is crucial. In exceptional circumstances, mineral deficiencies may necessitate supplementation; however, excessive intake of supplements can have adverse effects on the immune system and should be avoided. Consequently, any supplementation should be approved by medical professionals and administered in recommended doses. This review emphasizes the crucial significance of minerals in promoting optimal functioning of the immune system. It investigates the indispensable minerals required for immune system function and the regulation of inflammation. Moreover, it delves into the significance of maintaining an optimized intake of minerals from a nutritional standpoint.

Use of Cells, Supplements, and Peptides as Therapeutic Strategies for Modulating Inflammation after Spinal Cord Injury: An Update

Spinal cord injury is a traumatic lesion that causes a catastrophic condition in patients, resulting in neuronal deficit and loss of motor and sensory function. That loss is caused by secondary injury events following mechanical damage, which results in cell death. One of the most important events is inflammation, which activates molecules like proinflammatory cytokines (IL-1β, IFN-γ, and TNF-α) that provoke a toxic environment, inhibiting axonal growth and exacerbating CNS damage. As there is no effective treatment, one of the developed therapies is neuroprotection of the tissue to preserve healthy tissue. Among the strategies that have been developed are the use of cell therapy, the use of peptides, and molecules or supplements that have been shown to favor an anti-inflammatory environment that helps to preserve tissue and cells at the site of injury, thus favoring axonal growth and improved locomotor function. In this review, we will explain some of these strategies used in different animal models of spinal cord injury, their activity as modulators of the immune system, and the benefits they have shown.

Antioxidant effects of Se-glutathione peroxidase in alcoholic liver disease

Oxidative damage induced by ethanol and its metabolites is one of the factors that fuels the development of alcoholic liver disease (ALD). Selenium (Se) is an effective cofactor for glutathione peroxidase (GPx), and has antioxidant effects that improve ALD. In patients with ALD, ethanol-induced oxidative damage inhibits the synthesis of related Se-containing proteins such as: selenoprotein P (Sepp1), albumin (ALB), and GPx in the liver, thus decreasing the overall Se level in patients. Both Se deficiency and excess can affect the expression of GPx, resulting in damage to the antioxidant defense system. This damage enhances oxidative stress by increasing the levels of reactive oxygen species (ROS) in the body, which aggravates the inflammatory response, lipid metabolism disorder, and lipid peroxidation and worsens ALD symptoms. A cascade of oxidative damages caused by ALD will deplete selenium deposition in the body, stimulate the expression of Gpx1, Sepp1, and Gpx4, and thus mobilize systemic selenoproteins, which can restore GPx activity in the hepatocytes of ALD patients, reduce the levels of reactive oxygen species and alleviate oxidative stress, the inflammatory response, lipid metabolism disorder, and lipid peroxidation, thus helping to mitigate ALD. This review provides a reference for future ALD studies that evaluate the regulation of Se levels and contributes to studies on the potential pathological mechanisms of Se imbalance in ALD.

Metabolism of Selenium, Selenocysteine, and Selenoproteins in Ferroptosis in Solid Tumor Cancers

A potential target of precision nutrition in cancer therapeutics is the micronutrient selenium (Se). Se is metabolized and incorporated as the amino acid selenocysteine (Sec) into 25 human selenoproteins, including glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs), among others. Both the processes of Se and Sec metabolism for the production of selenoproteins and the action of selenoproteins are utilized by cancer cells from solid tumors as a protective mechanism against oxidative damage and to resist ferroptosis, an iron-dependent cell death mechanism. Protection against ferroptosis in cancer cells requires sustained production of the selenoprotein GPX4, which involves increasing the uptake of Se, potentially activating Se metabolic pathways such as the trans-selenation pathway and the TXNRD1-dependent decomposition of inorganic selenocompounds to sustain GPX4 synthesis. Additionally, endoplasmic reticulum-resident selenoproteins also affect apoptotic responses in the presence of selenocompounds. Selenoproteins may also help cancer cells adapting against increased oxidative damage and the challenges of a modified nutrient metabolism that result from the Warburg switch. Finally, cancer cells may also rewire the selenoprotein hierarchy and use Se-related machinery to prioritize selenoproteins that are essential to the adaptations against ferroptosis and oxidative damage. In this review, we discuss both the evidence and the gaps in knowledge on how cancer cells from solid tumors use Se, Sec, selenoproteins, and the Se-related machinery to promote their survival particularly via resistance to ferroptosis.

The Role of Minerals in the Optimal Functioning of the Immune System

Minerals fulfil a wide variety of functions in the optimal functioning of the immune system. This review reports on the minerals that are essential for the immune system’s function and inflammation regulation. We also discuss nutritional aspects of optimized mineral supply. The supply of minerals is important for the optimal function of the innate immune system as well as for components of adaptive immune defense; this involves defense mechanisms against pathogens in addition to the long-term balance of pro- and anti-inflammatory regulation. Generally, a balanced diet is sufficient to supply the required balance of minerals to help support the immune system. Although a mineral deficiency is rare, there are nevertheless at-risk groups who should pay attention to ensure they are receiving a sufficient supply of minerals such as magnesium, zinc, copper, iron, and selenium. A deficiency in any of these minerals could temporarily reduce immune competence, or even disrupt systemic inflammation regulation in the long term. Therefore, knowledge of the mechanisms and supply of these minerals is important. In exceptional cases, a deficiency should be compensated by supplementation; however, supplement over-consumption may be negative to the immune system, and should be avoided. Accordingly, any supplementation should be medically clarified and should only be administered in prescribed concentrations.

Roles of selenoprotein S in reactive oxygen species-dependent neutrophil extracellular trap formation induced by selenium-deficient arteritis

Selenium (Se) deficiency and poor plasma Se levels can cause cardiovascular diseases by decreasing selenoprotein levels. Neutrophil extracellular traps (NETs) may be the vicious cycle center of inflammation in vasculitis. Here, we show that Se deficiency induced arteritis mainly by reducing selenoprotein S (SelS), and promoted the progression of arteritis by regulating the recruitment of neutrophils and NET formation. Silencing SelS induced chicken arterial endothelial cells (PAECs) to secrete cytokines, and activated neutrophils to promote NET formation. Conversely, scavenging DNA-NETs promoted cytokine secretion in PAECs. The NET formation regulated by siSelS was dependent on a reactive oxygen species (ROS) burst. We also found that the PPAR pathway was a major mediator of NET formation induced by Se-deficient arteritis. Overall, our results reveal how Se deficiency regulates NET formation in the progression of arteritis and support silencing-SelS worsens arteritis.

The Function of Selenium in Central Nervous System: Lessons from MsrB1 Knockout Mouse Models

MsrB1 used to be named selenoprotein R, for it was first identified as a selenocysteine containing protein by searching for the selenocysteine insert sequence (SECIS) in the human genome. Later, it was found that MsrB1 is homologous to PilB in Neisseria gonorrhoeae, which is a methionine sulfoxide reductase (Msr), specifically reducing L-methionine sulfoxide (L-Met-O) in proteins. In humans and mice, four members constitute the Msr family, which are MsrA, MsrB1, MsrB2, and MsrB3. MsrA can reduce free or protein-containing L-Met-O (S), whereas MsrBs can only function on the L-Met-O (R) epimer in proteins. Though there are isomerases existent that could transfer L-Met-O (S) to L-Met-O (R) and vice-versa, the loss of Msr individually results in different phenotypes in mice models. These observations indicate that the function of one Msr cannot be totally complemented by another. Among the mammalian Msrs, MsrB1 is the only selenocysteine-containing protein, and we recently found that loss of MsrB1 perturbs the synaptic plasticity in mice, along with the astrogliosis in their brains. In this review, we summarized the effects resulting from Msr deficiency and the bioactivity of selenium in the central nervous system, especially those that we learned from the MsrB1 knockout mouse model. We hope it will be helpful in better understanding how the trace element selenium participates in the reduction of L-Met-O and becomes involved in neurobiology.

Selenium-chelating corn oligopeptide as a potential antioxidant supplement: investigation of the protein conformational changes and identification of the antioxidant fragment composition

A selenium-chelating corn oligopeptide (Se-COP) with high protein and low molecular weight was prepared as a selenium supplement. We utilized infrared (IR), ultraviolet (UV), and circular dichroism (CD) spectroscopy, 1-anilinonaphthalene-8-sulfonate (ANS)-binding fluorescence spectra, and isothermal titration calorimetry (ITC) to analyze and describe Se-COP and its reactions. It was concluded that the chelation reaction was a spontaneous process driven by enthalpy and entropy, with ΔH=3.79 × 104 ± 4075 cal/mol, ΔS = 146 cal/mol, ΔG = –23356.30 ± 126.94 cal/mol, binding constant Ka = 1.18 × 104 ± 855 M–1, and binding site number n = 0.13 ± 0.0126, and described as coordination bonds forming and hydrophobic interaction, as well as protein conformational changes including secondary and tertiary hydrophobic structure. Se-COP had strong antioxidant capacity, and mass spectrometry (MS) was used to identify the antioxidant peptide fragment, which was characterized as LLPPY and quantified at 428.95 ng/mg. This study indicated that Se-COP prepared by chelation may be a Se supplement with antioxidant capacity that can be applied in functional foods or ingredients.

Influence of daily oral prophylactic selenium treatment on the dibutyltin dichloride (DBTC)-induced pancreatitis in rats

Dibutyltin dichloride (DBTC) is an organotin compound used as model for acute and chronic pancreatitis. Oxidative stress is one of the mechanisms of propagation of acinar cell injury in acute pancreatitis. Selenium is an essential cofactor in the antioxidant glutathione peroxidase pathway. Selenium levels are described to be subnormal in patients with acute and chronic pancreatitis. The aim of our studies was to determine the prophylactic effect of Na-selenite [5 mg kg^-1 body weight (b.w.) per os (p.o.) 7 days] on the pathogenesis and course of DBTC- induced pancreatitis. Male inbred rats (LEW-1W Charles River) of 150 g body weight were used in this study. Experimental pancreatitis was induced by intravenous administration of 6 mg kg^-1 b.w. DBTC in rats. Na-selenite was administered as daily oral dose of 5 mg kg^-1 b.w. 7 days before induction of DBTC-pancreatitis. Malondialdehyde (MDA) was measured for monitoring levels of oxidative stress. Elimination of DBTC was reflected as tin concentration in bile and urine. Organ changes were indicated by serum parameters as well as histology. A prophylactic Na-selenite application significantly diminished MDA- and bilirubin concentration in serum, activities of lipase and transaminases as well as organ injuries compared to DBTC- treated rats in the absence of Na-selenite. The prophylactic oral 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 suggesting prophylactic substitution with Na-selenite to probably elicit beneficial effect on the clinical outcome in patients with endoscopic retrograde cholangiopancreatography (ERCP).

Effects of dietary vitamin E on fertility functions in poultry species

Vitamin E is found in high quantities in vegetable oils. Although vitamin E has multiple functions in humans and animals, its key function is protecting cells from oxidative damage. Since its discovery, several studies have demonstrated that vitamin E deficiency causes impaired fertility in humans and lab animals. However, the effects of vitamin E deficiency or of its supplementation on the fertility of farm animals, particularly on poultry, are less well studied. Therefore, a comprehensive review of the effects of dietary vitamin E on the fertility of poultry species is needed in order to understand the beneficial role of vitamin E in the maintenance of sperm and egg qualities. Based on the observations reviewed here, we found that a moderate amount of vitamin E in poultry diet significantly protects semen/sperm qualities in male birds and egg qualities in female birds via decreasing the lipid peroxidation in semen/sperms and eggs. This review provides an overall understanding of the effects of dietary vitamin E on fertility functions in poultry species.

Selenium status in patients with aspirin-induced asthma

BACKGROUND

Platelets are involved in the pathogenesis of aspirin-induced asthma (AIA). AIA patients suffer from an active disease despite avoidance of aspirin, and it has been suggested that administration of aspirin to these patients increases the generation of immediate oxygen products of arachidonic acid, 12-hydroperoxyeicosatetraenoic acid (12-HPETE), in their platelets. 12-HPETE further activates the 5-lipoxygenase of leukotriene B4-producing inflammatory macrophages precipitating an acute asthmatic attack. Glutathione peroxidase (GPX) has the antioxidant capacity to reduce 12-HPETE, and thus modulate the arachidonic acid metabolic cascade. There is evidence that selenium (Se) nutrition can influence asthma but Se status in AIA patients has not received much attention.

METHODS

We measured Se concentrations and GPX activities in platelets and plasma from 13 patients with AIA. Age- and sex-matched healthy individuals served as the control group.

RESULTS

Patients with AIA had significantly higher median platelet Se concentration (102 ng/mg platelet protein) when compared with controls (49 ng/mg platelet protein, P = 0.003). Plasma Se concentrations in patients with AIA and controls were not significantly different (P = 0.59). Median platelet GPX activity was significantly higher in patients with AIA (102.7 mU/mg platelet protein) than in controls (66 mU/mg protein) (P = 0.05). The patient and control groups when combined showed weak, but significant correlation between platelet Se concentration and platelet GPX activity (r = 0.44; P = 0.03).

CONCLUSION

It is proposed that the higher platelet Se concentration observed in AIA patients contributed to the higher platelet GPX activity seen in these patients. Such an enhanced antioxidant defence system might represent an adaptive response to protect against increasing free radical production by inflammatory cells in AIA and help decelerate ongoing respiratory hypersensitivity.

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.

Low hair selenium and plasma glutathione peroxidase in children with chronic renal failure

Selenium (Se) is a trace element that incorporates into the selenoenzyme glutathione peroxidase (GSH-Px). There are conflicting results regarding the Se levels and activity of GSH-Px in adult uremic patients. The aim of this study was to determine (1) the hair Se status, (2) the possible relation between the hair Se status and the antioxidant enzyme, GSH-Px, and (3) the influence of different treatment procedures on hair Se status and GSH-Px activity in children with CRI, those treated conservatively and those on HD and on CAPD. Ninety-three patients, including 32 patients with CRI, treated conservatively, 42 PD patients, 19 HD patients and 34 healthy children were enrolled in the study. The hair Se level was measured by the atomic absorption spectrophotometer method. Plasma GSH-Px activity was determined using a Randox test combination (RANSEL). Hair Se levels were significantly lower in the CRI, CAPD, and HD groups when compared to the control group (P=0.001, P=0.001, and P=0.001, respectively). Plasma GSH-Px activity was significantly lower in the CRI, CAPD, and HD groups when compared to the control group (P=0.001, P=0.001, and P=0.001, respectively). Plasma GSH-Px activity correlated with the GFR in patients with CRI and the control group (P=0.000; r(2)=0.60). There was no correlation between plasma GSH-Px and hair Se levels in the patient and control groups. These results revealed a decreased hair Se level and impaired antioxidative capacity in children with CRI on CAPD and HD. The lack of any relation between plasma GSH-Px and hair Se suggests that plasma GSH-Px is not a good marker of Se stores.

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.

Selenium serum and urine is associated to mild asthma and atopy. The SUS study

To examine the associations between selenium (Se) status, asthma, bronchial hyperresponsiveness (BHR), and atopy in 154 male subjects (72 with mild asthma, 41 with BHR and 41 with no respiratory symptoms) aged 18 (range 17-22) years. Each subject underwent a medical interview and FEV1 and FVC were recorded. Histamine bronchial reactivity (Yan method) was measured, skin prick test (inhalant allergens) was performed and Se in urine and serum was analysed (AOAC modified fluometric method). Se in serum 74.04 (10.58) micrograms/L (mean (SD)) was lower in subjects with asthma and the logarithm of the ratio of Se in serum (microgram/L) and urine standardised to creatinine excretion (ng/mg creatinine) 0.748 (0.096) (mean (SD)) was lower in subjects with asthma and atopy compared to subjects with no allergic symptoms 77.79 (10.16) micrograms/L and 0.808 (0.111) respectively (p < 0.05). In subjects with asthma atopy was significantly associated to urine Se 0.24 (0.73) (beta (SE)) (p < 0.05). Subjects with BHR had the same Se status as subjects with no respiratory symptoms and heavy smokers had a lower concentration of Se in serum 73.80 (9.56) micrograms/L than non-smokers 78.16 (10.74) micrograms/L (p < 0.05), Se status was associated to asthma and smoking. Measuring Se in urine might add further information to possible relations between Se status, atopy and asthma.

Loss of zinc and selenium does not occur through peritoneal dialysis

A prospective study was done to determine whether zinc (Zn) and selenium (Se) loss occurs in patients on continuous ambulatory peritoneal dialysis through their dialysate effluent. Fifty pairs of aliquots of dialysis fluid were collected from 29 patients. Each paired set of specimens consisted of the dialysate fluid before instillation into the peritoneal cavity and a specimen of the spent effluent after dialysis for comparison. Zn and Se concentrations were measured using inductively coupled plasma atomic emission spectrophotometry. The range of dialysate fluid Zn concentration before instillation was 0 to 1.75 microg/mL and that for Se was 0 to 0.33 microg/mL. Ranges for Zn and Se in the postdialysis effluent were 0 to 0.60 and 0 to 0.56 microg/mL, respectively. The concentration differences in 50 pairs of samples were analyzed with Wilcoxon's test. The difference in Zn levels between the predialysis specimen and the effluent was 0.009 +/- 0.036 microg/mL (P = 0.154). The difference for Se was 0.018 +/- 0.21 microg/mL (P = 0.118). In conclusion, no significant loss or gain of Zn or Se occurs in patients undergoing continuous ambulatory peritoneal dialysis.

T-cell dysfunction in a patient with short bowel syndrome: report of a case

We describe herein the case of a 48-year-old man who underwent emergency massive resection of the small intestine due to strangulated ileus, which led to short bowel syndrome (SBS) as he was left with 7 cm of jejunum and 8 cm of ileum. We evaluated the immune function in this patient, focusing particular attention on T-cell-mediated immunity. Biochemical and nutritional parameters, including minerals and trace elements, indicated that the patient was in relatively good health; however, the proliferative response to mitogen and tumor necrosis factor-alpha production in response to the anti-CD3 monoclonal antibody in peripheral blood lymphocytes (PBL) were impaired compared with age-matched postgastrectomy patients and healthy donors. Moreover, the expression of T-cell receptor (TCR) zeta, which is involved in signal transduction and the subsequent activation of T cells, was downregulated in this patient compared with that in the age-matched postgastrectomy patients and healthy donors. These observations suggest that T-cell function was disturbed in our patient, and that this dysfunction was associated with the decreased expression of TCR zeta molecules.

Plasma and urinary selenium in Saudi Arabian patients with dilated cardiomyopathy

We measured selenium (Se) levels in the urine and blood plasma samples of 72 Saudi Arabian patients with dilated cardiomyopathy (DCM) and 70 control subjects of the same origin. To correct for differences in the hydration state of the subjects, the selenium concentration for each urine sample was normalized by dividing it by the concentration of creatinine (CREAT) in the same sample. The median (and range) of the values found for the concentration of Se in plasma, urine, and normalized concentration in urine for the control subjects was 1.306 (0.66-2.50) microM, 0.478 (0.05-2.00) microM, and 56.7 (10.6-426.5) microM Se/M CREAT, respectively, whereas, for the patients, it was 1.246 (0.53-2.45) microM, 0.39 (0.05-1.90) microM, and 75.1 (4.9-656.2) microM Se/M CREAT, respectively. Additionally, the patients were separated into three subgroups according to the severity of their disease state as judged by NYHA procedure, and were then compared to the control group. Only group 4 (the most severe state of the disease) had a significantly lower concentration of urinary Se than the control group. However, the difference became nonsignificant when normalized for CREAT levels. There was no significant difference in the plasma Se levels between the controls and any of the patient groups. As the plasma Se in the control group and in the DCM patients both fell on the low end of the "normal" range, with the patients being marginally lower than the controls, there is no firm evidence from this study to suggest that Se is related to the high incidence rate of DCM found in Saudi Arabia.

Dietary antioxidants and magnesium in type 1 brittle asthma: a case control study

BACKGROUND

Type 1 brittle asthma is a rare form of asthma. Atopy, psychosocial factors and diet may contribute to this condition. As increased dietary magnesium has a beneficial effect on lung function and selenium, vitamins A, C and E have antioxidant properties, a study was undertaken to test the hypothesis that patients with brittle asthma have diets deficient in these nutrients compared with subjects with non-brittle asthma and healthy adults.

METHODS

A case control study of the dietary intakes of 20 subjects with brittle asthma, 20 with non-brittle asthma, and 20 healthy adults was performed using five day weighed dietary records. Intake of magnesium was the primary outcome measure with selenium and vitamins A, C and E as secondary outcomes. Serum levels were measured at the same time as the dietary assessment.

RESULTS

Sixty subjects (27 men) of mean age 49.5 years were recruited and completed the study. Subjects with brittle asthma had statistically lower median dietary intakes of vitamins A and E than the other groups (vitamin A: brittle asthma 522.5 micrograms/day, non-brittle asthma 869.5 micrograms/day, healthy adults 806.5 micrograms/day; vitamin E: brittle asthma 4.3 mg/day, non-brittle asthma 4.6 mg/day, healthy adults 4.5 mg/day). Median dietary intakes for the other nutrients were not significantly different between groups. Serum levels were within normal ranges for each nutrient in all subjects. Intakes less than the reference nutrient intake (RNI) for magnesium and vitamins A and C, and less than the safe intake (SI) for vitamin E were more likely in patients with brittle asthma than in those with non-brittle asthma.

CONCLUSION

Nutrient deficiency and reduced antioxidant activity may contribute to disease activity in type 1 brittle asthma, although a prospective study of replacement therapy will be needed to confirm this hypothesis.

Direct determination of selenium in human blood plasma and seminal plasma by graphite furnace atomic absorption spectrophotometry and clinical application

Direct determination of selenium (Se) in body fluids by graphite furnace atomic absorption spectrophotometry (GFAAS) may suffer from problems like severe background, matrix effects, preatomization losses, and spectral interferences. In this study we evaluate critically the influence on the accuracy of the direct determination of Se in blood plasma and seminal plasma by GFAAS, and propose a simple, rapid, and accurate method, suitable for routine clinical analysis. The method for blood plasma is mainly based on studies by the use of matched matrix and a Pd-Ni modifier, but for seminal plasma only a Pd modifier is required. The method developed was also applied to study the Se distribution in plasma protein fractions of patients with hepatocellular carcinoma. The Se in plasma of patients was significantly lower than that of the controls. The distribution pattern of Se in blood plasma fractions of patients was also different from that of the controls.

Deficiency of selenium enhances the K+-induced release of dopamine in the striatum of mice

To determine whether a selenium (Se) deficiency in the brain leads to a functional change in dopaminergic transmission in the striatum, in vivo microdialysis was conducted in mice fed a low-Se diet. After 11-13 weeks of the diet regimen, the activity of glutathione peroxidase (GPx) in the Se-deficient brain was reduced to 60% of the control brain. A high K+ perfusion (100 mM) increased the level of dopamine in the dialysate to 67 +/- 16 times the basal level; the increase was significantly greater than that observed in the control group (28 +/- 4 times). Such a between-group difference was not observed after 4-5 weeks of the Se-diet. These results indicated that prolonged Se deficiency altered the function of striatal dopaminergic neurons in mice. A possible contribution of enhanced oxidative stress due to the reduced GPx activity is discussed.

Mice deficient in cellular glutathione peroxidase develop normally and show no increased sensitivity to hyperoxia

Glutathione peroxidase, a selenium-containing enzyme, is believed to protect cells from the toxicity of hydroperoxides. The physiological role of this enzyme has previously been implicated mainly using animals fed with a selenium-deficient diet. Although selenium deficiency also affects the activity of several other cellular selenium-containing enzymes, a dramatic decrease of glutathione peroxidase activity has been postulated to play a role in the pathogenesis of a number of diseases, particularly those whose progression is associated with an overproduction of reactive oxygen species, found in selenium-deficient animals. To further clarify the physiological relevance of this enzyme, a model of mice deficient in cellular glutathione peroxidase (GSHPx-1), the major isoform of glutathione peroxidase ubiquitously expressed in all types of cells, was generated by gene-targeting technology. Mice deficient in this enzyme were apparently healthy and fertile and showed no increased sensitivity to hyperoxia. Their tissues exhibited neither a retarded rate in consuming extracellular hydrogen peroxide nor an increased content of protein carbonyl groups and lipid peroxidation compared with those of wild-type mice. However, platelets from GSHPx-1-deficient mice incubated with arachidonic acid generated less 12-hydroxyeicosatetraenoic acid and more polar products relative to control platelets at a higher concentration of arachidonic acid, presumably reflecting a decreased ability to reduce the 12-hydroperoxyeicosatetraenoic acid intermediate. These results suggest that the contribution of GSHPx-1 to the cellular antioxidant mechanism under normal animal development and physiological conditions and to the pulmonary defense against hyperoxic insult is very limited. Nevertheless, the potential antioxidant role of this enzyme in protecting cells and animals against the pathogenic effect of reactive oxygen species in other disorders remains to be defined. The knockout mouse model described in this report will also provide a new tool for future study to distinguish the physiological role of this enzyme from other selenium-containing proteins in mammals under normal and disease states.

Pulmonary effects of short term selenium deficiency

BACKGROUND

Selenium dependent glutathione peroxidase (GPx) reduces hydrogen peroxide (H2O2) and organic hydrogen peroxides in both normal and pathological states. Chronic dietary deficiency of selenium results in a gradual decrease in GPx and altered response to environmental stress. However, glutathione-S-transferase (GST) isozymes may increase and compensate for chronic GPx deficiency. The pattern of antioxidant enzyme activity and immunolocalisation of various enzymes in rat lung has not been described in short term (< 3 weeks) acute selenium deficiency.

METHODS

The time course of GPx depletion from rat lung (measured every five days in subgroups of rats) during acute dietary selenium deficiency was evaluated. After 20 days of depletion, enzyme activity of lung GPx, catalase, superoxide dismutase (SOD), glutathione reductase (GR), glucose-6-phosphodiesterase (G-6-PD), and GST were determined. Immunohistochemical localisation of GPx and SOD was also performed. The response to lethal hyperoxia (> 95%) in control and selenium deficient rats was then established.

RESULTS

At 20 days, lung GPx activity in the rats fed a selenium deficient diet was one third less than in control animals who received a normal diet, while changes in blood enzymes between control and deficient animals were similar. Other lung enzyme activities remained normal with the exception of cyanide inhibited SOD activity measured in selenium deficient rat lungs which declined to approximately 50% of normal. Immunohistochemical localisation of GPx showed a generalised loss of the enzyme throughout the lung parenchyma with some possible sparing of activity in epithelial cells of the bronchioles. When exposed to lethal hyperoxia, selenium deficient animals were more susceptible than control rats.

CONCLUSIONS

This is the earliest time at which dietary selenium deficiency has been shown to produce moderate loss of GPx activity. This change in activity was associated with increased susceptibility to pulmonary oxidant stress. However, the role of decreased SOD activity (presumed to represent copper, zinc SOD), although unexpected, may have been a major contributor to increased damage from hyperoxia. These results emphasise the complex potential interaction of elemental deficiency with the natural antioxidant response to lethal hyperoxia.

Human selenium supplementation as assessed by changes in blood selenium concentration and glutathione peroxidase activity

This review concentrates on the differences in the effects on indicators of selenium (Se) status of different chemical forms proposed for Se supplementation in healthy subjects. Modifications in blood (plasma and erythrocyte) Se concentrations and in the Se-dependent glutathione peroxidase (GSH-Px) enzymatic activity, in plasma, erythrocytes and platelets, were compared considering the basal Se status, the dose and the chemical form of Se supplement, as well as the duration of the intervention. Organic Se forms (Se-yeast, selenomethionine and food-Se) increased blood Se more concentration rapidly and to a greater extent than inorganic forms (selenite and selenate). However, no significant difference in the response of both plasma and erythrocyte GSH-Px activity could be observed. In contrast, platelet GSH-Px activity was more sensitive to the chemical form of Se administered. Saturation of platelet GSH-Px activity occurred at lower plasma Se levels when selenite or selenate were used as Se supplements than with the organic forms. Interpretation of some of the results is provided and ideas are suggested for consideration in further studies.

Selenium in human lactation

The primary factor determining selenium concentration in human milk is the maternal selenium intake. A significant correlation between selenium in human milk and maternal selenium intake has been reviewed in papers from different regions of the world. Infants fed human milk have higher selenium intake than those fed commercially available formula milk or baby foods. Selenium compounds found in breast milk seem to be more biologically available for infant nutrition than those in formulas. Increased requirements of selenium have been observed in pregnant and lactating women. Supplementation of lactating and pregnant women with different selenium compounds has been assayed, and selenium supplementation of soil and cows has been used to increase the selenium status of children fed infant formula made from cow's milk.

Selenium in uremia

The importance of selenium as an essential trace element for man has been increasingly recognized during the last several years. Selenium deficiency has been associated with cases of congestive cardiomyopathy, skeletal myopathy, anemia, enhanced cancer risk, elevated incidence of cardiovascular disease, immune system alterations, hair and nail changes, and abnormalities in thyroid hormone metabolism. These symptoms are frequently present in chronic uremic patients. Nevertheless, the prevalence and significance of selenium deficiency in the uremic syndrome is still not clearly defined. This article reviews the selenium status in chronic uremic patients, the supposed pathogenetic mechanisms of selenium disturbance in uremia, and the possible role of selenium deficiency on some uremic abnormalities.

A possible beneficial effect of selenium administration in antiarrhythmic therapy

OBJECTIVE

The following review of the literature on the importance of Selenium (Se) in myocardial homeostasis and of the pharmacology of this trace metal, represents an attempt to search, without prejudice to other possible explanations, for a rationale of a beneficial effect of Se substitution as an adjuvant to antiarrhythmic therapy.

BACKGROUND

For several years, in the early 1980s, I had to deal with the problem of a serious ventricular arrhythmia (non-sustained and sustained ventricular tachycardia) which was remarkably resistant to a battery of the most potent antiarrhythmic agents. Eventually, dramatic improvement, lasting for a period of 8 years, was achieved with Flecainide, which, however, left unsolved the episodic occurrence of disabling ventricular bigemini. Over the most recent period of 1 year and 8 months, there was a sudden and unexplained return to unbroken normal sinus rhythm. Among the multiplicity of possible reasons for this fortunate development, the concurrent introduction of Se substitution appeared as the most obvious, though very tentative explanation. Substitution of this trace metal preceded the extinction of ventricular bigemini by 1 week and actually represented the sole modification of otherwise reasonably standardized conditions of antiarrhythmic therapy, life style and diet.

Trace element (Al, Se, Zn, Cu) levels in serum, urine and tissues of burn patients

Trace elements are known to play many important roles in humans. It has also been shown that some of these elements are essential in wound healing. In this study, aluminium, copper, zinc and selenium levels were determined in serum, urine and tissue samples of burned patients and the relationships between wound healing and trace elements were evaluated. Trace element levels were determined using atomic absorption spectrophotometry. During 20 days' treatment, a significant rise in aluminium levels was determined in serum, urine and tissue samples of patients. After day 5 of treatment, copper levels increased significantly only in urine samples. Zinc levels decreased in serum and tissue samples. However, zinc gave high values in urine within the first week then returned to the initial value. There was a significant decrease in zinc in serum and tissue samples taken from burned patients during treatment. Urine selenium levels showed a significant rise within the first 15 days.

Factors affecting the selenium intake of people in Transbaikalian Russia

The selenium concentration in foods grown and consumed and in plasma, red blood cells, and toenails of people living in the district of Chita in the transbaikalian part of Russia were studied in August 1991. Preliminary results from the area have suggested low selenium intakes and the possible occurrence of cardiomyopathy (Keshan disease) in the population. A low selenium concentration in foods grown locally was found: mean selenium concentration in wheat grains was 1, 5, and 28 micrograms/kg, respectively, in three villages studied, that of oats was between 3-6 micrograms/kg, and of cow's milk 10-27 micrograms/kg dry matter. The selenium concentration of bread was considerably higher, between 87-337 micrograms/kg dry wt, presumably because wheat imported from the US had been used for baking. Occasional samples of pork, beef, and mutton contained between 32-218 micrograms selenium/kg dry wt. Low selenium concentrations were observed in samples of soil and river water. The mean plasma selenium concentration of 52 persons was 1.02 mumol/L, including 33 children and 19 adult subjects. The selenium concentrations in red blood cells and toenails were 1.95 mumol/L and 0.61 mg/kg, respectively. No symptoms of heart disease caused by selenium deficiency were observed. It is concluded that the selenium status of people was fairly good thanks to the contribution to dietary intake of imported wheat with a high selenium content. As the selenium concentration was very low in foods grown in the area, the selenium intake of the population will be reduced to a very low level if only locally produced foods are consumed.

Selenium administration does not cause thyroid insufficiency in subjects with mild iodine deficiency and sufficient selenium intake

Selenium is a trace element essential for the activity of type I 5'-deiodinase which converts thyroxine (T4) to 3,5,3'-triiodothyronine (T3). In iodine deficient hypothyroid children at low selenium dietary intake the supplementation of selenium induced a significant decrement of serum FT4 and T4 concentrations and an increase of serum TSH concentrations. Since in western countries selenium tablets begin to be largely consumed as a diet integrator, we have administered 100 micrograms/day of selenium as selenium methionine to 8 euthyroid female subjects with a positive iodine-perchlorate discharge test who had a previous episode of subacute or postpartum thyroiditis. We have studied subjects with positive iodine-perchlorate discharge test since the test indicates the existence of a subtle defect of thyroid hormone synthesis and therefore these subjects are prone to develop thyroid dysfunction. In contrast to previous findings in hypothyroid children at low iodine and selenium dietary intake, the supplementation of selenium did not decompensate thyroid hormone synthesis of euthyroid subjects with reduced thyroid iodine organification. The lack of any effect of selenium on thyroid hormone synthesis even in subjects with subtle thyroid hormone synthesis defect may be due to the fact that these subjects had a sufficient selenium dietary intake before selenium supplementation and an only marginally reduced dietary iodine intake.

Reference values for serum zinc and selenium of French healthy children

Age - and sex-specific reference intervals derived from a healthy pediatric population are presented for zinc, selenium and related analytes in serum. No strong correlations were found between age, sex and trace elements in serum. Serum variables were discussed to assess their ability as biochemical indicators of micronutrient status in the field of biological epidemiology.

Selenium status of healthy immigrant Parisian preschool children

Plasma selenium (Se) concentration and erythrocyte glutathione peroxidase activity (GPx) were assessed in a population of healthy preschool children two to five years old, residing in the city of Paris. In the 118 subjects, mean (+/- SD) plasma Se concentration was 62.10 +/- 13.96 micrograms/L, and mean GPx activity was 23.58 +/- 8.52 U/g Hb. Mean plasma Se of male children was significantly (p = 0.001) higher (12%) than levels of girls. Plasma selenium levels were not correlated with erythrocyte GPx activity. Children from Mediterranean origin had a slightly lower erythrocyte GPx activity (p < 0.05) than children from other regions. Mean plasma Se concentration of this group corresponded to the lower limit of intervals, which characterizes geographical regions of intermediate selenium concentrations.

Serum selenium and glutathione-peroxidase activities and their interaction with toxic metals in dialysis and renal transplantation patients

Selenium, aluminum, cadmium, and magnesium concentrations and glutathione-peroxidase activities in sera of 35 healthy individuals, 30 renal transplants, and 30 hemodialysis patients were measured. Serum selenium, aluminum, and cadmium concentrations in both groups of patients were higher than the controls (p less than 0.001), whereas the serum glutathione-peroxidase levels were lower (p less than 0.001). According to our results, it can be concluded that the patients receiving hemodialysis are subjected to more toxic elements than the transplantation patients. These findings imply that dietary selenium supplement may be suggested in renal failure for the detoxification of elements, such as cadmium and mercury. The essential trace element selenium takes part not only in the direct protection of endothelial cells against the accumulation of aggressive oxygen species, but also in the prevention of the toxic effects of cadmium or in the modulation of the active calcium transport.

Antioxidant status (selenium, vitamins A and E) and aging

Antioxidant status can be evaluated by blood selenium, vitamins A and E. The level of selenium was determined in whole blood, erythrocytes and plasma of 170 French people (70-95 years old) healthy and with intercurrent illness, by using PIXE (proton-induced X-ray emission analysis). These results are discussed with other values from the literature. Plasma levels of vitamins A and E have been measured by HPLC. All data were compared with those obtained for younger subjects. Healthy elderly people residing in a geriatric home received selenium supplements during 1 month. The influence of this supplementation brought to light a deficiency for this trace element. The correlation of aging and nutritional requirements with immune function, heart and cancer death rate is presented and discussed.

Clinical implications of trace elements in endocrinology

The implications of essential trace elements in endocrinological processes, mainly thyroid function, growth, gonadal function, adrenal hormones, prolactin, glucose homeostasis, calcium-phosphorus metabolism, and thymulin activity, are reviewed. Most concerned elements in this field include iodine, zinc, selenium, copper, chromium, manganese and vanadium. The minerals are powerful modulators of several physiological functions that can be considerably perturbed in deficiency states. The resulting biochemical and clinical modifications can be prevented and/or corrected by adequate supplementation. Sometimes, however, they act like pharmacological agents when their beneficial effects are not the result of a correction of a nutritional deficiency state. Their potentialities as therapeutic agents are perfectly described in many cases, but some indications deserve further investigations.

The impact of selenium supplementation on mood

The possibility that a subclinical deficiency of the trace element selenium might exist in a sample of the British population was examined by giving a selenium supplement for 5 weeks. Using a double-blind cross-over design, 50 subjects received either a placebo or 100 mcg selenium on a daily basis. On three occasions they filled in the Profile of Moods States. A food frequency questionnaire was used to estimate the intake of selenium in the diet. Intake was associated with a general elevation of mood and in particular, a decrease in anxiety. The change in mood when taking the active tablet was correlated with the level of selenium in the diet, which was estimated from a food frequency questionnaire. The lower the level of selenium in the diet the more reports of anxiety, depression, and tiredness, decreased following 5 weeks of selenium therapy. The results are discussed in terms of the low level of selenium in the food chain in some parts of the world.

Selenium in rheumatic diseases

Selenium is involved in several important biochemical pathways relevant to rheumatic diseases. Experimental and clinical studies suggest that selenium modulates the inflammatory and immune responses. Patients suffering from inflammatory rheumatic diseases often have low selenium levels, but this finding does not correlate with disease severity. Selenium supplementation needs stricter selection criteria and better ascertainment of dose to obtain a stimulatory or inhibitory effect relevant to the disease state. Prevention of marginal selenium deficiency by moderate supplementation might enhance host defense mechanisms.

Physiological and nutritional importance of selenium

The essential trace element selenium has recently attracted attention because of its potentialities in the maintenance of human health. Selenium forms part of the active site of the peroxide-destroying enzyme glutathione peroxidase, and it also has other functions, for example in biotransformation, detoxification and the immune response. Functional and clinical consequences of selenium deficiency states have been described, and the selenium requirement, which is influenced by the usual selenium exposure, has been discussed. Wide variations have been found in selenium status in different parts of the world, and populations or groups of patients exposed to marginal deficiency are more numerous than was previously thought. Current research activities in the field of human medicine and nutrition are devoted to the possibilities of using selenium for the prevention or treatment of degenerative or free radical diseases such as neurological disorders, inflammatory diseases or cancer. Pharmacological selenium doses are also recommended as an adjuvant in some treatments.

Assessment of cardiac function by M-mode echocardiography in selenium-deficient phenylketonuric children

Selenium (Se) deficiency is associated with cardiac and skeletal muscle dysfunction. Twenty well children aged 2-16 years (10 male) attending the Phenylketonuria (PKU) Clinic at the Royal Children's Hospital, Brisbane, had low Se levels (mean 0.29 +/- 0.02 s.e.m. mumol/L; normal range 0.56-1.16 mumol/L). Their myocardial function was assessed at rest and after exercise provocation by M-mode echocardiography in order to exclude occult left ventricular dysfunction. At rest, fractional shortening (FS) was normal (mean 38.1 +/- 1.1 s.e.m. %, n = 20). After exercise, FS increased significantly (P less than 0.001) from 37.6 +/- 1.4% to 44.3 +/- 1.2%, n = 12). This was associated with a significant rise (P less than 0.001) in heart rate (HR) from 77.3 +/- 3.1 beats/min to 125.8 +/- 5.2 beats/min (n = 12). The normal resting FS and normal increase in FS and HR with exercise is evidence against significant cardiac impairment in this group of Se-deficient children.

Effects of selenium supplementation on blood and urine selenium levels and liver function in patients with primary biliary cirrhosis

To study the mechanism of the reduced serum selenium concentration in patients with liver damage we administered 200 micrograms (2.53 mumol) selenium daily as selenium-rich yeast to 8 patients with primary biliary cirrhosis and 8 healthy controls over 16 weeks. Initially selenium concentrations in serum were 24% lower (P less than 0.001) in patients than controls. During supplementation serum selenium levels increased in both groups but the difference between them persisted. Throughout the study whole blood selenium levels and glutathione peroxidase activities were also somewhat lower (P = NS) in patients than controls. Selenium supplementation had no effect on whole blood glutathione peroxidase activities in either group. The basal 24 h urinary excretion of selenium was similar in both groups but was increased more by supplementation in patients than controls. Selenium administration did not influence the liver function of the patients. We conclude that impaired hepatic production of selenium-containing serum compounds is the most likely explanation for the reduced serum selenium concentration in patients with primary biliary cirrhosis.