Relationship of serum selenium and antioxidants to plasma lipoproteins, platelet aggregability and prevalent ischaemic heart disease in Eastern Finnish men

Sex-specific relationship between blood selenium levels and platelet count in a large cohort representative of the United States population

While several small studies have found that selenium deficiency is associated with low platelet counts, they lack generalizability. We used data from the National Health and Nutrition Examination Surveys collected over a 12-year period. We examined the relationship between selenium quartiles and platelet count using survey-weighted linear regression models adjusting for age, sex, race, household income to poverty threshold income, highest education attainment, smoking status, red blood cell folate, and body mass index. Of the 21,764 participants, 51% were females, 23% African Americans, and 25% were >65 years of age. Mean (SD) platelet count was 243(64) 10⁹/L and selenium was 183(32) µg/L. Women had significantly higher platelet count but lower selenium levels than men (258 vs. 227 10⁹/L and 181 vs. 185 µg/L respectively; both P < 0.0001). In adjusted analysis, participants in the highest selenium quartile had 8.0x10⁹/L higher platelet count as compared to those in the lowest selenium quartile (95%CI = 4.1 to 11.9; P < 0.0001). Gender modified the relationship between the two; although there was no difference in women, platelet count was higher in the highest than the lowest selenium quartile in men (interaction p-value = 0.001). These findings highlight the importance of selenium and gender in platelet biology which needs to be explored.

Dietary selenium intake and the risk of kidney stones in adults, an analysis of 2007-2018 National Health and Nutrition Examination Survey, a cross-sectional study

Purpose

To evaluate the association between dietary selenium intake and the risk of kidney stones in adults.

Materials and methods

We performed a cross-sectional analysis using data from 2007 to 2018 National Health and Nutrition Examination Survey (NHANES). Dietary intake information of 30,184 participants was obtained using first 24-h dietary recall interview, and kidney stones were presented by a standard questionnaire. The quartile analysis, stratified analysis and non-linearity analysis were used to estimate the association between dietary selenium intake and kidney stones after an adjustment for potential confounders.

Results

The multiple logistic regression indicated that the fourth quantile (Q4) of dietary selenium intake had a lower risk of kidney stones than the first quantile (Q1) in Model 3 (OR 0.82, P < 0.05). The stratified analyses indicated there were statistical differences between dietary selenium intake and kidney stones among younger (age < 50) (OR 0.65, P < 0.01), male (OR 0.73, P < 0.01) and overweight/obese (BMI ≥ 25.0) (OR 0.80, P < 0.05) individuals in Model 3. The non-linear relationship was founded between dietary selenium intake and kidney stones in all participants, younger, male and overweight/obese individuals after adjusting for confounding factors.

Conclusion

Our study revealed an inverse relation between the level of dietary selenium intake and the risk of kidney stones for the United States population, especially for younger (age < 50), male and overweight/obese (BMI ≥ 25.0) individuals. The study provides preliminary guidance on dietary selenium intake for the prevention of kidney stones in different populations. Further studies are required to confirm our findings and clarified the biological mechanisms.

Selenium concentration is associated with occurrence and diagnosis of three cardiovascular diseases: A systematic review and meta-analysis

BACKGROUND

Selenium (Se) is a vital trace element playing its biological functions through selenoprotein, which has been implicated in various physiological and pathological processes. A growing number of studies indicate that low Se increases the risk of cardiovascular diseases (CVDs). This meta-analysis aimed to compare and analyze differences in Se levels between patients with heart failure (HF), myocardial infarction (MI), coronary heart disease (CHD), and healthy people. This will provide ideas with the potential to improve clinical intervention and prevention of CVDs.

METHODS

The PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI) and Chinese Biomedical databases were systematically searched for relevant publications until November 20, 2020. The following combination keywords were used: "(heart failure disease OR myocardial infarction OR coronary heart disease) AND (selenium OR Se)". The identified studies were screened against inclusion and exclusion criteria and extracted data were analyzed using RevMan5.3 and State 16.0 software.

RESULTS

A total of 49 eligible studies (including 61 cohorts) were obtained. Results of the meta-analysis showed that there was a significant difference in Se levels between HF, MI, CHD patients and healthy people. The standard mean difference (SMD) level of Se in HF patients [SMD = -0.98, 95 % CI (-1.34, -0.62)], MI patients [MI: SMD = -3.46, 95 % CI (-4.43, -2.85)], and CHD patients [CHD: SMD = -0.47, 95 % CI (-0.64, -0.28)] were all significantly lower compared to healthy controls. Analysis of the correlation between Se level and publication year showed that SMD of Se levels in HF and controls was positively correlated with time. Se level was found to be a good diagnostic marker of MI (AUC = 0.7107, P = 0.0167, Sensitivity = 77.27 %, Specificity = 72.73 %).

CONCLUSIONS

This meta-analysis shows that Se levels in patients with HF, MI, and CHD are generally lower compared with healthy controls. However, due to the small number of included studies, further studies are needed to confirm the present results.

Correlation study between gastronomy culture and content of selenium towards prevalence of cardiovascular and diabetes in West Java, Indonesia

BACKGROUND AND AIM

Selenium (Se) is an important element in the human body. Deficiency or excess of Se can cause harm to human health. A previous study showed an association of Se with cardiovascular and diabetes diseases. One of the food sources of Se is vegetables. In West Java, Indonesia, people consume fresh vegetables such as Garlic, Jengkol, and Petai. This research aims to study the correlation between the gastronomy culture of people in West Java, Se content in Garlic (Allium sativum), Jengkol (Archidendron pauciflorum) and Petai (Parkia speciosa) from several Regencys/cities in West Java, and the prevalence cardiovascular and diabetic diseases.

METHOD

A cultural study was conducted based on a literature review. Cluster sampling was chosen for the sampling method. The prevalence of cardiovascular disease and diabetes in these regencies were obtained from the Ministry of Health of Indonesia. The measurement of Se content in a sample was conducted by the fluorometry method, based on the formation of the piazoselenol complex from the reaction between selenite ion and DAN (2,3-diaminonapthalene).

RESULTS

People in West Java prefer to consume garlic, jengkol, and petai as a fresh vegetable as part of their culture. The highest content of Se in Allium sativum was found in Tasikmalaya City with a value of 69.20 ng/g. For Archidendron pauciflorum from Subang Regency values were 498 ng/g. Parkia speciosa found in the Bandung Barat Regency had a mean value 257.9 ng/g. There is a positive correlation between Se-concentration in Archidendron pauciflorum and the prevalence of diabetes while negative correlation with the prevalence of cardiovascular disease. In addition, no correlation was observed for Allium sativum and Parkia Specose might be due to a lower Se-concentration in these vegetables that in the Archidendron fauciflorum.

CONCLUSION

Different areas have varying concentrations of Se in plants that grow in the region. The gastronomy culture and Se content may play a role to increase or decrease cardiovascular and diabetes prevalence in that area.

Understanding of metals dysregulation in patients with systolic and diastolic dysfunction in ischemic heart disease

Ischemic heart disease (IHD) is the leading cause of death and chronic disability in the world. IHD affects both the systolic and diastolic function of the heart which progressively leads to heart failure; a structural and functional impairment of filling or ejection of blood from the heart. In this study, the progression of systolic and diastolic dysfunction characterized according to their echocardiographic parameters including left ventricular ejection fraction (EF), grades of diastolic dysfunction and ratio between early mitral inflow velocity and mitral annular early diastolic velocity (E/eʹ), were correlated with differential regulation of various metals in patients sera samples (n = 62) using inductive coupled plasma-mass spectrometry (ICP-MS). Chromium, nickel and selenium were found significant (p < 0.05) in patients having EF < 45% compared with EF > 45%. In patients with systolic dysfunction (EF < 45%), the level of selenium was decreased while the level of chromium and nickel was increased compared to patients with EF > 45%. Selenium level was also decreased significantly (p < 0.05) in grade 1A and 2 patients that are considered as higher grades of diastole dysfunction in comparison to grade 0–1. Overall, selenium deficiency was identified in both systolic and diastolic dysfunctions of IHD patients corresponding to the progression of disease that could be related to many metabolic and translational pathways specifically which involve selenoproteins.

Biomarkers of the metabolic syndrome: Influence of minerals, oligo- and trace elements

Influences of minerals, oligo- and trace elements on the concentration of biomarkers of the metabolic syndrome (MetS) are reviewed. Since food is a complex mixture of caloric compounds and essential non-caloric food components with multiple interactions and varying bioavailability, it is hard to separate or identify the effect of one single component in a total meal or diet. Moreover the diet contains various non-nutritive biologically active components, which may add some beneficial characteristics. Therefore, conclusions on the effect of components on various biomarkers of MetS are sometimes quite contradictory. Reasons therefore are mentioned. Literature data should be studied in detail to conclude whether a component is related to a reduction of MetS-related symptoms or whether its influence is merely affecting a biomarker.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Randomised controlled trial of the effect of long-term selenium supplementation on plasma cholesterol in an elderly Danish population

Although cross-sectional studies have shown a positive association between Se and cholesterol concentrations, a recent randomised controlled trial in 501 elderly UK individuals of relatively low-Se status found that Se supplementation for 6 months lowered total plasma cholesterol. The Danish PRECISE (PREvention of Cancer by Intervention with Selenium) pilot study (ClinicalTrials.gov ID: NCT01819649) was a 5-year randomised, double-blinded, placebo-controlled trial with four groups (allocation ratio 1:1:1:1). Men and women aged 60-74 years (n 491) were randomised to 100 (n 124), 200 (n 122) or 300 (n 119) μg Se-enriched yeast or matching placebo-yeast tablets (n 126) daily for 5 years. A total of 468 participants continued the study for 6 months and 361 participants, equally distributed across treatment groups, continued for 5 years. Plasma samples were analysed for total and HDL-cholesterol and for total Se concentrations at baseline, 6 months and 5 years. The effect of different doses of Se supplementation on plasma lipid and Se concentrations was estimated by using linear mixed models. Plasma Se concentration increased significantly and dose-dependently in the intervention groups after 6 months and 5 years. Total cholesterol decreased significantly both in the intervention groups and in the placebo group after 6 months and 5 years, with small and nonsignificant differences in changes in plasma concentration of total cholesterol, HDL-cholesterol, non-HDL-cholesterol and total:HDL-cholesterol ratio between intervention and placebo groups. The effect of long-term supplementation with Se on plasma cholesterol concentrations or its sub-fractions did not differ significantly from placebo in this elderly population.

Selenium Level and Dyslipidemia in Rural Elderly Chinese

OBJECTIVE

Higher selenium level has been hypothesized to have the potential to reduce the risk of cardiovascular diseases including dyslipidemia. However, results from previous studies are inconsistent. This study aims to determine the association between selenium level and dyslipidemia in elderly Chinese with relatively low selenium status.

METHODS

A cross-sectional study of 1859 participants aged 65 or older from four rural counties in China was conducted. Serum total cholesterol (TC), triglycerides (TG), high density lipoprotein-cholesterol (HDLC) and low-density lipoprotein-cholesterol (LDLC), nail selenium concentration and APOE genotype were measured in all subjects. The four types of dyslipidemia were defined as >5.17 mmol/L for High-TC, >1.69 mmol/L for High-TG, >3.36 mmol/L for High-LDLC, and <1.04 mmol/L for Low-HDLC according to Chinese Guidelines on Prevention and Treatment of Dyslipidemia in Adults. Logistic models adjusting for age, gender, APOE genotype, body mass index, alcohol consumption, smoking, physical activity, medication use for cardiovascular diseases were used to examine the relationship between selenium levels and the risk of dyslipidemia.

RESULTS

Mean nail selenium concentration was 0.465 μg/gin this sample. Rates for High-TC, High-LDLC, High-TG, Low-HDLC were 18.13%, 13.23%, 12.21% and 32.76% respectively. Results from logistic models indicated that higher selenium levels were significantly associated with higher risk of High-TC, High-LDLC and lower risk of Low-HDLC adjusting for covariates (p < 0.0001). Compared with the lowest selenium quartile group, participants in selenium quartile groups 2, 3 and 4 had significantly higher rates of High-TC, High-LDLC, High-TG, and lower rate of Low-HDLC adjusting for covariates. No significant association was observed between selenium level and the risk of High-TG. APOEε4 carriers had higher rates of High-TC and High-LDLC. There was no interaction between selenium level and APOE with the rates of dyslipidemia.

CONCLUSIONS

Our results suggest long-term selenium exposure level may be associated with the risk of dyslipidemia in elderly population. Future studies are needed to examine the underlying mechanism of the association.

Association between selenium nutritional status and metabolic risk factors in men with visceral obesity

BACKGROUND AND AIM

Previous evidence has suggested an association between selenium and cardiovascular disease, which is main outcome of metabolic syndrome. The aim of this study was to examine possible correlation between selenium nutritional status and metabolic risk factors in men with visceral obesity.

METHODS

Plasma samples were collected from 123 Indonesian men with visceral obesity. Their metabolic risk factors and selenium nutritional status were analyzed. The eligible subjects (n=78) were stratified according to the International Diabetes Federation: obese, obese plus one component, and obese plus two components or more. Obese plus two components or more were diagnostic criteria of metabolic syndrome. Pearson's correlation was performed to examine the correlation in each group.

RESULTS

In the obese group, selenium positively correlated with high-density lipoprotein (HDL) cholesterol (r=0.390, P<0.05) and with fatty acid binding protein-4 (FABP4) (r=0.474, P<0.05); glutathione peroxidase-3 (GPx3) activity was inversely correlated with FABP4 (r=-467, P<0.05). In the obese plus one component group, GPx3 activity positively correlated with HDL cholesterol (r=0.413, P<0.05). In the metabolic syndrome group, selenium negatively correlated with monocytes chemoattractant protein (MCP)-1 (r=-0.429, P<0.05).

CONCLUSIONS

These results show that the association between selenium nutritional status and metabolic risk factors is limited to particular group of obese men with or without metabolic syndrome.

Selenium supplementation for the primary prevention of cardiovascular disease

BACKGROUND

Selenium is a key component of a number of selenoproteins which protect against oxidative stress and have the potential to prevent chronic diseases including cardiovascular disease (CVD). However, observational studies have shown inconsistent associations between selenium intake and CVD risk; in addition, there is concern around a possible increased risk of type 2 diabetes with high selenium exposure.

OBJECTIVES

To determine the effectiveness of selenium only supplementation for the primary prevention of CVD and examine the potential adverse effect of type 2 diabetes.

SEARCH METHODS

The following electronic databases were searched: the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 10 of 12, October 2012) on The Cochrane Library; MEDLINE (Ovid) (1946 to week 2 October 2012); EMBASE Classic + EMBASE (Ovid) (1947 to 2012 Week 42); CINAHL (EBSCO) (to 24 October 2012); ISI Web of Science (1970 to 24 October 2012); PsycINFO (Ovid) (1806 to week 3 October 2012); Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment Database and Health Economics Evaluations Database (Issue 4 of 4, October 2012) on The Cochrane Library. Trial registers and reference lists of reviews and articles were searched and experts in the field were approached. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials on the effects of selenium only supplementation on major CVD end-points, mortality, changes in CVD risk factors, and type 2 diabetes were included both in adults of all ages from the general population and in those at high risk of CVD. Trials were only considered where the comparison group was placebo or no intervention. Only studies with at least three months follow-up were included in the meta-analyses, shorter term studies were dealt with descriptively.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Twelve trials (seven with duration of at least three months) met the inclusion criteria, with 19,715 participants randomised. The two largest trials that were conducted in the USA (SELECT and NPC) reported clinical events. There were no statistically significant effects of selenium supplementation on all cause mortality (RR 0.97, 95% CI 0.88 to 1.08), CVD mortality (RR 0.97, 95% CI 0.79 to 1.2), non-fatal CVD events (RR 0.96, 95% CI 0.89 to 1.04) or all CVD events (fatal and non-fatal) (RR 1.03, 95% CI 0.95 to 1.11). There was a small increased risk of type 2 diabetes with selenium supplementation but this did not reach statistical significance (RR 1.06, 95% CI 0.97 to 1.15). Other adverse effects that increased with selenium supplementation, as reported in the SELECT trial, included alopecia (RR 1.28, 95% CI 1.01 to 1.62) and dermatitis grade 1 to 2 (RR 1.17, 95% CI 1.0 to 1.35). Selenium supplementation reduced total cholesterol but this did not reach statistical significance (WMD - 0.11 mmol/L, 95% CI - 0.3 to 0.07). Mean high density lipoprotein (HDL) levels were unchanged. There was a statistically significant reduction in non-HDL cholesterol (WMD - 0.2 mmol/L, 95% CI - 0.41 to 0.00) in one trial of varying selenium dosage. None of the longer term trials examined effects on blood pressure. Overall, the included studies were regarded as at low risk of bias.

AUTHORS' CONCLUSIONS

The limited trial evidence that is available to date does not support the use of selenium supplements in the primary prevention of CVD.

Environmental Pathology

Humans are constantly exposed to hazardous pollutants in the environment—for example, in the air, water, soil, rocks, diet, or workplace. Trace metals are important in environmental pathology because of the wide range of toxic reactions and their potential adverse effects on the physiological function of organ systems. Exposures to toxic trace metals have been the subject of numerous environmental and geochemical investigations, and many studies have been published on the acute and/or chronic effects of high-level exposures to these types of agents; however, much fewer data are available concerning the health effects of low-dose chronic exposure to many trace metals. Chronic low-dose exposures to toxic elements such as cadmium and arsenic have been shown to cause these metals to accumulate in tissues over time, leading to multiple adverse effects in exposed individuals.

Selenium supplementation for the primary prevention of cardiovascular disease

This is the protocol for a review and there is no abstract. The objectives are as follows: The primary objective is to determine the effectiveness of selenium only supplementation for the primary prevention of CVD. We will also determine potential adverse effects of selenium only supplementation on major CVD risk factors, such as blood pressure, blood lipids and type 2 diabetes. Results will be stratified by baseline selenium status and country where possible, as well as by selenium dosage.

Studies on scavenger receptors under experimental hypercholesterolemia: modulation on selenium supplementation

Scavenger receptors (SR) are the cell surface proteins that can bind and internalize modified lipoproteins. Because ox-LDL seems to play a key role in foam cell formation during atherogenesis, SR may be critical for pathogenesis of atherosclerosis. The present study was aimed to study the effect of selenium (Se) supplementation on SR, i.e., SRB1 and CD36 under experimental hypercholesterolemia. Male Sprague Dawley rats were divided into three groups and fed on the control diet, high cholesterol diet (HCD), and HCD + Se, respectively, for a period of 4 months. Selenium and reactive oxygen species (ROS) levels were estimated in serum and liver respectively. mRNA expression using RT-PCR and protein expression using ELISA were analyzed for SRB1 and CD36 receptors. Selenium levels decreased whereas ROS levels increased under experimental hypercholesterolemic state. Selenium supplementation (1 ppm), however, diminished the HCD-induced ROS levels. Furthermore, the protein expression of SRB1 was significantly reduced in HCD group in comparison to the control group. On the other hand, HCD-induced increase in CD36 mRNA and protein expression decreased significantly on Se supplementation. In conclusion, CD36 receptors seem to play a pro-atherogenic role under hypercholesterolemic state. Selenium supplementation, in addition, might prove to be a therapeutically valuable approach in near future to limit the adverse effect of hypercholesterolemia.

Selenium and preeclampsia: A global perspective

Preeclampsia is a complex multisystem disorder of pregnancy where oxidative stress plays an important aetiological role. The role of selenium in the synthesis of endogenous antioxidants is well documented, and a significant reduction in selenium has been reported in preeclamptic women. The objective of this study was to map global selenium status and preeclampsia incidence. This study identified peer reviewed journal articles reporting national preeclampsia incidence (%) and matched these with reported values of selenium intake and plasma/serum selenium concentrations (μg/L). Matched data were obtained for 45 regions, reporting 6456,570 births, spanning Europe, Asia, Australasia, Africa, North and South America. Increasing plasma selenium concentration was found to be correlated with a reduction in preeclampsia incidence (Pearson's r=-0.604, P<0.0001). Countries with a reported serum/plasma selenium level of ⩾95μg/L were considered selenium sufficient and a significant reduction in preeclampsia incidence for countries above this value (P=0.0007) was noted. Significant reductions in preeclampsia incidence were found to coincide with increases in plasma/serum selenium concentration in the New Zealand (P=0.0003) and Finland (0.0028) populations following Government intervention. This study supports the hypothesis that selenium supplementation may be beneficial in reducing oxidative stress in women at risk of preeclampsia.

Selenium status and cardiometabolic health: state of the evidence

Use of selenium enriched foods, supplements and fertilizers has increased markedly in recent years in the US and other Western countries because of the perception that the anti-oxidant properties of selenium could potentially reduce the risk of cancer and other chronic diseases. However, concern has been raised recently about possible adverse cardiometabolic effects of high selenium exposure, including an increased risk of diabetes and hyperlipidemia with high selenium intake. Hence, from a public health perspective, the relationship between selenium status and cardiometabolic health should be clarified in order to help guide consumers in their choices of nutritional supplements and enriched food products. Additional experimental evidence is needed to provide new insights into the role of selenium and of specific selenoproteins in human biology, especially to clarify the underlying mechanisms linking selenium to chronic disease endpoints. Further epidemiological studies and randomized clinical trials across populations with different selenium status should be conducted to determine the causal effect of selenium on cardiovascular disease and risk factors. Nevertheless, at the present time the widespread use of selenium supplements or other strategies that artificially increase selenium status above the level required for optimal selenoprotein activity is not justified and should not be encouraged.

Serum selenium concentration is associated with metabolic factors in the elderly: a cross-sectional study

Background

Selenium is an essential micronutrient known for its antioxidant function. However, the association of serum selenium with lipid profiles and fasting glucose are inconsistent in populations with average intake of selenium. Furthermore, there were few studies conducted specifically for the elderly. This study examined the relationship of serum selenium concentration with serum lipids and fasting glucose in the Taiwanese elderly population.

Methods

This was a cross-sectional study of 200 males and females aged 65-85 years (mean 71.5 ± 4.6 years) from Taipei, Taiwan. Serum selenium was measured by inductively coupled plasma-mass spectrometer. The association between serum selenium and metabolic factors was examined using a multivariate linear regression analysis after controlling several confounders.

Results

The mean serum selenium concentration was 1.14 μmol/L, without significant difference between sexes. Total cholesterol, triglycerides, and LDL cholesterol increased significantly with serum selenium concentration (P < 0.001, P < 0.05 and P < 0.001, respectively) after adjusting for age, gender, anthropometric indices, lifestyle factors, and cardio-vascular risk factors in several linear regression models. Furthermore, there was a significantly positive association between serum selenium and serum fasting glucose concentrations (P < 0.05).

Conclusions

Total cholesterol, triglycerides, and LDL cholesterol, and fasting serum glucose concentrations increased significantly with serum selenium concentration in the Taiwanese elderly. The underlying mechanism warrants further research.

The effect of insulin in combination with selenium on blood glucose and GLUT4 expression in the cardiac muscle of streptozotocin-induced diabetic rats

We evaluated the effect of a combination of low doses of insulin (1 U/kg/day) and selenium (180 microg/kg/day) on general physiological parameters and the level of glucose transporter (GLUT4) in the cardiac muscle of streptozotocin-induced diabetic rats. Diabetic rats were treated with insulin, selenium and a combination of insulin and selenium for 4 weeks. The levels of blood glucose and hemoglobin A1c were estimated; the level of the GLUT4 in the cardiac muscle was examined by immunoblotting and immunohistochemistry. Insulin in combination with selenium could significantly lower blood glucose and HbA1c levels and could restore disturbances in GLUT4 level in the cardiac muscle. The treatment with insulin was only partially effective in the restoration of diabetic alterations. We conclude that there was cooperation between insulin and selenium, and that the treatment of diabetic rats with combined doses of insulin and selenium was effective in the control of blood glucose and correction of altered GLUT4 distribution in diabetic rat hearts.

Protective role of selenium supplementation against cardiac lesions induced by the combination of levomepromazine and risperidone in the rabbit

Neuroleptics are a suspected cause of sudden death in psychiatric patients, especially in those with pre-existing cardiac lesions. As these lesions were previously shown to be associated with selenium (Se) deficiency, the aim of the present study was to evidence the possible protective effect of Se supplementation against cardiac lesions induced by the combination of the neuroleptic drugs levomepromazine and risperidone in the rabbit. Two groups of 6 rabbits were treated with 3 mg/kg of levomepromazine daily intramuscularly combined with 1 mg/kg of risperidone intramuscularly every other week for 3 consecutive months, and one group additionally received a solution of sodium selenite (2 μg/kg/day) intramuscularly during the whole treatment period. Furthermore, one group of six untreated animals was given the Se supplementation and another group of six control animals received saline daily. Blood samples were drawn before and at the end of the treatment period for the measurement of serum Se levels. At the end of the study, all animals were sacrificed and their hearts were removed for the measurement of tissue Se concentrations. In addition, the hearts were prepared for histopathological examination. A variety of cardiac lesions was found in the neuroleptics-treated animals without supplementation and to a lesser extent in the control and Se-supplemented untreated animals. Importantly, only rare cardiac lesions were observed in neuroleptics-Se-treated animals. The most striking differences in Se concentrations were noted in the myocardium: as compared to controls, there was a 43% reduction in neuroleptics-treated, but non-Se-supplemented animals (p < .01), at the end of the treatment period, whereas only a 14% reduction (p < .05) was noted in the neuroleptics-Se-treated animals. These results confirm that neuroleptics induce cardiac lesions associated with Se deficiency. Selenium supplementation markedly decreased the incidence and severity of neuroleptics-induced cardiac lesions and these findings may serve as a basis for further evaluation of the protective role of Se supplementation in neuroleptics-treated patients. However, Se supplementation in normal animals without Se deficiency was also shown to be cardiotoxic.

Antioxidant enzyme activity and coronary heart disease: meta-analyses of observational studies

Controversial data exist concerning the relation between the activities of scavenger antioxidant enzymes and coronary heart disease (CHD) risk. The authors report updated meta-analyses of studies assessing the activities of 3 antioxidant enzymes--glutathione peroxidase, superoxide dismutase, and catalase--and CHD risk. Computer-based and manual searches of the relevant literature from January 1966 to January 2008 were performed. Studies assessing glutathione peroxidase, superoxide dismutase, and catalase activities in cells or biologic fluids and clinical CHD outcomes were selected. Pooled odds ratios for CHD were calculated by using an inverse-variance-weighted random-effects model. Forty-two case-control studies and 3 prospective studies were included. The pooled odds ratios for CHD associated with a 1-standard-deviation increase in glutathione peroxidase, superoxide dismutase, and catalase activity levels were 0.51 (95% confidence interval: 0.35, 0.75), 0.48 (95% confidence interval: 0.32, 0.72), and 0.32 (95% confidence interval: 0.16, 0.61), respectively, with substantial between-study heterogeneity (I(2) > 90% for the 3 enzymes). These findings were remarkably robust in the sensitivity analysis. The authors' meta-analyses support an inverse association between circulating levels of superoxide dismutase, glutathione peroxidase, and catalase activities with CHD and emphasize the need for additional high-quality prospective studies.

Metabolism of selenium compounds catalyzed by the mammalian selenoprotein thioredoxin reductase

The mammalian thioredoxin reductases (TrxR) are selenoproteins with a catalytic selenocysteine residue which in the oxidized enzyme forms a selenenylsulfide and in the reduced enzyme is present as a selenolthiol. Selenium compounds such as selenite, selenodiglutathione and selenocystine are substrates for the enzyme with low K(m)-values and the enzyme is implicated in reductive assimilation of selenium by generating selenide for selenoprotein synthesis. Redox cycling of reduced metabolites of these selenium compounds including selenide with oxygen via TrxR and reduced thioredoxin (Trx) will oxidize NADPH and produce reactive oxygen species inducing cell death at high concentrations explaining selenite toxicity. There is no free pool of selenocysteine since this would be toxic in an oxygen environment by redox cycling via thioredoxin systems. The importance of selenium compounds and TrxR in cancer and cardiovascular diseases both for prevention and treatment is discussed. A selenazol drug like ebselen is a direct substrate for mammalian TrxR and dithiol Trx and ebselen selenol is readily reoxidized by hydrogen peroxide and lipid hydroperoxides, acting as an anti-oxidant and anti-inflammatory drug.

Fibrates but not statins increase plasma selenium in dyslipidemic aged patients--the EVA study

This secondary analysis of "Etude du Vieillissement Artériel" (EVA) study reports the effect of fibrates and statins on plasma selenium concentration and its 9-year change in free-living dyslipidemic elderly. Dyslipidemic patients were categorized in three sub-groups according to final low-density lipoprotein (LDL)-cholesterol level or hypolipidemic treatment: non-treated dyslipidemic (LDL-cholesterol >4.41 mmol/L, n=84); dyslipidemics who were treated exclusively by fibrates (n=47) or by statins (n=25) whatever their serum LDL-cholesterol concentration. The influence of lipid-lowering treatments on plasma selenium concentrations and its 9-year change was evaluated by analysis of variance (ANOVA) and multivariate linear regression models taking into account cardiovascular risk and changes in lipid-profile parameters. Multivariate linear regression indicated that the plasma selenium decline was associated with the longitudinal variation in LDL (beta=-0.039+/-0.019, p=0.04) and high-density lipoprotein (HDL)-cholesterol concentrations (beta=0.187+/-0.059, p=0.002) but not with triglycerides (beta=-0.018+/-0.031, p=0.57). During the 9-year follow-up, similar plasma selenium declines were observed in all the sub-groups (p=0.33) despite plasma selenium levels being higher in fibrate users and lower in statin users (p=0.0004). The mechanisms underlying these data are not yet totally understood, but considering the risk of selenium deficiency in the elderly and its relationship with poor health status further clinical trial is needed to verify the proposed hypotheses.

Serum selenium and serum lipids in US adults

BACKGROUND

Selenium, an essential micronutrient, has received considerable attention for its antioxidant properties. In addition, selenium may affect several cardiometabolic risk factors, such as glucose homeostasis and lipid concentrations. However, the effects of selenium intake on the lipid profile in selenium-replete populations, such as the United States, are largely unknown.

OBJECTIVE

We examined the relation of serum selenium concentrations with serum lipids in a representative sample of US adults.

DESIGN

This was a cross-sectional analysis of 5452 men and women aged >/= 20 y participating in the third National Health and Nutrition Examination survey. Serum selenium was measured by atomic absorption spectrometry.

RESULTS

The multivariable adjusted differences in total cholesterol, LDL cholesterol, HDL cholesterol, apolipoprotein B (apo B), and apolipoprotein A-I (apo A-I) comparing the highest with the lowest quartile of serum selenium were 16.6 mg/dL (95% CI: 11.6, 21.4 mg/dL), 10.9 mg/dL (95% CI: 6.4, 15.4 mg/dL), 3.2 mg/dL (95% CI: 1.6, 5.0 mg/dL), 8.9 mg/dL (95% CI: 5.6, 12.2 mg/dL), and 6.9 mg/dL (95% CI: 1.7, 12.1 mg/dL), respectively. Participants in the highest quartile of serum selenium had 10% higher concentrations of triacylglycerols than did participants in the lowest quartile (ratio of triacylglycerol concentrations: 1.10; 95% CI: 1.05, 1.17). The difference in the ratios of LDL cholesterol to HDL cholesterol and apo B to apo A-I that compared the highest with the lowest selenium quartiles were 0.11 (95% CI: -0.02, 0.25) and 0.03 (95% CI: 0.00, 0.06), respectively.

CONCLUSION

Elevated serum selenium was associated with elevated serum concentrations of total cholesterol, LDL cholesterol, HDL cholesterol, triacylglycerols, apo B, and apo A-I among US adults, a selenium-replete population. Experimental studies are needed to determine cause and effect relations and the potential mechanisms underlying these associations.

Associations of blood selenium and serum lipid levels in Japanese premenopausal and postmenopausal women

OBJECTIVE

The purpose of this study was to investigate whether the level of selenium in serum or the level of selenium in erythrocytes (E-Se) was associated with serum lipid parameters (total cholesterol [TC], triglycerides, and high-density and low-density lipoprotein cholesterol [LDL-C]) in pre- and postmenopausal women.

DESIGN

Healthy female workers aged 35 to 60 years were recruited, and TC, triglycerides, high-density lipoprotein cholesterol, LDL-C, E-Se, and serum-Se levels were measured in 68 premenopausal and 59 postmenopausal women after excluding those who were treated for hyperlipidemia, receiving hormone therapy, had previous gynecological surgeries, or had irregular menstrual cycles. Information on these women, such as smoking status, current status of menstruation, and current or previous medical treatments, was obtained from a self-administered questionnaire. Correlation analyses and stepwise multiple regression analysis were applied to reveal the interrelationship between serum lipids and Se levels after adjusting for age, body mass index, smoking, and menopause status.

RESULTS

Postmenopausal women had significantly higher levels of TC, triglycerides, and LDL-C and lower levels of E-Se than premenopausal women. TC and LDL-C levels after menopause correlated negatively with E-Se. These associations were also statistically significant after controlling for age, smoking status, and body mass index. E-Se was selected as a significant related variable to explain TC and LDL-C levels as well as body mass index by multiple regression analysis.

CONCLUSION

E-Se may be one of the possible associated factors that decrease the levels of TC and LDL-C after menopause. Further studies are needed to clarify the cause-and-effect relationship of nutritional Se status and lipid profile.

Seasonal mercury exposure and oxidant-antioxidant status of James Bay sport fishermen

The effects of a moderate seasonal exposure to methylmercury on plasma low-density lipoprotein (LDL) oxidation and cardiovascular risk indices are not known. The objective of the study was to assess the effects of a seasonal exposure to mercury at similar dose reported to increase cardiovascular risk through fish consumption. Effects on lipoprotein cholesterol and fatty acid profiles, LDL oxidation, and blood oxidant-antioxidant balance were to be assessed in sport fishermen presenting normal blood selenium and omega-3 fatty acid contents. Thirty-one healthy James Bay sport fishermen were assessed for within-subject longitudinal seasonal variations in hair and blood mercury, plasma oxidized LDL, lipophilic antioxidants, homocysteine, blood selenium, and glutathione peroxidase and reductase activities determined before and after the fishing season and compared by matched-pair tests. Hair mercury doubled during the fishing season (2.8+/-0.4 microg/g, P<.0001). Baseline blood selenium, homocysteine, and erythrocyte fatty acid profiles did not change. Plasma high-density lipoprotein cholesterol increased (+5%, P=.05), whereas very low-density lipoprotein cholesterol and oxidized LDL decreased (-8%, P=.05; -18%, P=.008). Blood glutathione peroxidase (+9.7%, P=.001), glutathione reductase (+7.2%, P<.0001), and total glutathione (+45% P<.0001) increased during the fishing season. Plasma total coenzyme Q10 (+13%, P=.02), ubiquinone-10 (+67%, P=.03), and beta-carotene (+46%, P=.01) also increased, whereas vitamin E status was unaffected. Pairwise correlations revealed no association between mercury exposure and any of the biomarkers investigated. In contrast, strong predictors of cardiovascular risk such as high-density lipoprotein cholesterol, oxidized LDL, and glutathione peroxidase improved during the fishing season despite elevated methylmercury exposure. The beneficial effects of seasonal fishing activity and fish consumption on cardiovascular health may suppress detrimental effects of concomitant moderate methylmercury exposure.

Selenium intake and cardiovascular risk: what is new?

PURPOSE OF REVIEW

Selenium is an essential element with a narrow safety margin. Adequate selenium intake is needed to maximize the activity of glutathione peroxidases and other selenoproteins. This review discusses recent experimental and epidemiologic contributions on the role of selenium for the prevention of atherosclerotic cardiovascular disease.

RECENT FINDINGS

Few randomized trials have evaluated the efficacy of selenium supplementation on cardiovascular endpoints. Most trials, conducted in selenium-replete populations, found no evidence of cardiovascular protection. A meta-analysis of 13 prospective cohort studies found a moderate inverse relationship between plasma/serum selenium and coronary heart disease. The interpretation of these data is complicated, however, by potential residual confounding and publication bias. In contrast, recent data from trials of selenium-containing supplements and from epidemiologic studies suggest that chronically increased selenium intake in selenium-replete populations can induce diabetes and maybe also hypercholesterolemia.

SUMMARY

Current evidence is insufficient to support a protective role for selenium in cardiovascular prevention. Large high-quality randomized controlled trials and observational studies are needed across populations with different levels of selenium intake. Furthermore, subjects living in regions with high selenium intake should be aware that selenium supplements may increase their risk of diabetes and hypercholesterolemia.

Plasma copper, zinc, and selenium levels and correlates with metabolic syndrome components of lebanese adults

Zinc, copper, and selenium statuses were reported to be linked to the development of chronic diseases, especially coronary heart disease (CHD). Metabolic syndrome, a known CHD risk factor, was found to be highly prevalent in Lebanon. Nevertheless, no data are available on the statuses of plasma zinc, copper, and selenium, especially in terms of their relation to the components of the metabolic syndrome. A sample of 398 men and women aged 18-65 years was drawn from 23 health centers across Lebanon; anthropometric measurements and biochemical analyses of fasting plasma samples were performed. Subjects were found to have normal plasma statuses of copper and selenium but were at elevated risk of zinc deficiency. Plasma selenium levels correlated positively with all the components of the metabolic syndromes, while that of copper correlated only with total, high-density lipoprotein and low-density lipoprotein cholesterol. Plasma zinc did not correlate with any of the metabolic syndrome components.

Role of selenium in heart lesions produced by neuroleptics in the rabbit

Organic and/or functional heart lesions sometimes resulting in sudden death have been described in psychiatric patients treated with neuroleptics. As selenium has been suggested previously to play a role in the development of such lesions, the present study was undertaken to determine whether a correlation could be found between heart lesions induced by neuroleptics and changes in blood selenium as well as myocardial tissue concentrations in the rabbit. Twelve NZW adult rabbits were treated intramuscularly with both levomepromazine (3 mg kg(-1) day(-1)) and risperidone (1 mg kg(-1) once every other week) for 3 months, and compared with 12 saline-treated controls. Blood samples were drawn before and at the end of the study. Tissue samples from the heart, liver and kidneys were obtained at the end of treatment, and the hearts were examined histologically. Heart lesions including disorganization of cardiac fibers, myolysis, interstitial and endocardial fibrosis, and necrosis were noted in treated animals, but not in controls. There was a 20% decrease in selenium blood levels and a 50% decrease in selenium myocardial tissue levels in treated animals compared with controls (P < 0.001). In contrast, no differences in selenium levels in liver and kidneys were found across the experimental groups. These results suggest a possible correlation between selenium depletion and neuroleptics-induced heart lesions.

Relationships between selenium, lipids, iron status and hormonal therapy in women of the SU.VI.M.AX cohort

Significant differences in serum selenium concentration according to contraceptive treatment and age have been evidenced in women of the SU.VI.M.AX cohort. This study aimed at verifying the physiopathological hypothesis that the observed increase in serum selenium concentration could be related to serum lipid increase and/or bleeding decrease. Women were divided into six groups: menopausal with or without hormonal replacement therapy; non-menopausal using contraceptive pills; intrauterine device; other contraceptive treatment or no contraceptive treatment. Adjusted linear regression indicated positive associations between selenium and apolipoprotein A1 (r(2) from 0.038 to 0.074, p<0.07 depending on groups) or ferritin in serum (r(2) from 0.032 to 0.075, p<0.07 depending on groups). These relationships could explain the differences observed according to hormonal treatment and age in the SU.VI.MAX study.

Decreased beta-adrenoceptor chronotropic response in selenium-deficient mice: negative crosstalk between iNOS activity and cAMP accumulation

With the aim to study if selenium (Se) deficiency affects the basal frequency and cardiac response to isoproterenol (ISO), mice were fed a Se-deficient diet (Se-) or the same diet supplemented with 0.2 ppm Se as sodium selenite (Se+) for 4 wk. Atria frequency, cyclic AMP (cAMP) accumulation, nitric oxide synthase (NOS) activity, and beta-adrenoceptor-binding assay were then examined. Results showed that Se-mice have both a reduction in atria frequency as well as in cAMP content but higher NOS activity levels either at basal or after ISO stimulation. These differences were suppressed by feeding Se-mice with a Se-supplemented diet for 1 wk or by inhibition of inducible nitric oxide synthase (iNOS). Alterations observed after ISO stimulation in atria of Se-mice were not related to a beta-adrenoceptor expression modification because specific radioligand-binding parameters in cardiac membranes from Se-mice and Se+ mice were similar. The reduced response on rate and cAMP in atria from Se-mice to direct adenylate cyclase (AC) stimulation by forskolin and the shifted upward levels present in 2-amino-4-methylpyridine-treated Se-mice is in agreement with a negative crosstalk between iNOS activity and AC activity in Se-mice.

Selenium and coronary heart disease: a meta-analysis

BACKGROUND

It is hypothesized that low selenium concentrations are associated with an increased risk of cardiovascular disease and that selenium supplements prevent coronary heart disease.

OBJECTIVE

The objective was to perform a meta-analysis on the association of selenium biomarkers with coronary heart disease endpoints in observational studies and on the efficacy of selenium supplements in preventing coronary heart disease endpoints in randomized trials.

DESIGN

The MEDLINE and the Cochrane Library databases were searched for studies conducted from 1966 through 2005. Relative risks were pooled by using an inverse-variance weighted random-effects model.

RESULTS

Twenty-five observational studies (14 cohort and 11 case-control studies) that measured blood or toenail selenium concentrations and 6 randomized trials that evaluated supplements containing selenium met our inclusion criteria. The pooled relative risk in a comparison of the highest with the lowest selenium concentration categories was 0.85 (95% CI: 0.74, 0.99) in cohort studies and 0.43 (0.29, 0.66) in case-control studies. In observational studies, a 50% increase in selenium concentrations was associated with a 24% (7%, 38%) reduction in coronary heart disease risk. In randomized trials, the pooled relative risk in a comparison of supplements containing selenium with placebo was 0.89 (0.68, 1.17).

CONCLUSIONS

Selenium concentrations were inversely associated with coronary heart disease risk in observational studies. Because observational studies have provided misleading evidence for other antioxidants, the validity of this association is uncertain. Few randomized trials have addressed the cardiovascular efficacy of selenium supplementation, and their findings are still inconclusive. Evidence from large ongoing trials is needed to establish low selenium concentrations as a cardiovascular disease risk factor. Currently, selenium supplements should not be recommended for cardiovascular disease prevention.

Selenium-induced alterations in ionic currents of rat cardiomyocytes

In the present study, rats were treated with sodium selenite (5 micromol/kg body weight/day, ip) for 4 weeks and the parameters of contractile activity, action potential, L-type Ca2+-current (ICaL), as well as transient outward (Ito), inward rectifier (IK1), and steady state (Iss) K+-currents were investigated. Sodium selenite treatment increased rat blood glucose level and lowered plasma insulin level, significantly. This treatment also caused slightly prolongation in action potential with no significant effects on spontaneous contraction parameters and intracellular Ca2+ transients of the heart preparations. These effects were associated with marked alterations in the kinetics of both ICaL and Ito including a significant slowing in both inactivation time constants of ICaL and a significant shift to negative potential at half-inactivation of these channels without any change in the current density. Also, there was a significantly faster inactivation of Ito and no shift in half-inactivation of this channel without any change in its current density. Consequently, there was a approximately 50% increase in total charges carried by Ca2+ current and approximately 50% decrease in total charges carried by K+ currents of the treated rat cardiomyocytes. Additionally we observed a significant inhibition in IK1 density in treated rat cardiomyocytes. Oxidized glutathione level was significantly increased (70%) while the observed decrease in reduced glutathione was much less. Since a shift in redox state of regulatory proteins is related with cell dysfunction, selenium-induced increase in blood glucose and decrease in plasma insulin may correlate these alterations. These alterations, in the kinetics of the channels and in IK1 density, might lead to proarrhythmic effect of chronic selenium supplementation.

Whole blood selenium content in healthy adults in the Czech Republic

Over a 5-year period, from 1996 to 2001, blood selenium levels were recorded in a set of 2414 healthy blood donors (1781 men and 633 women; 880 smokers and 1534 nonsmokers) living in four selected areas of the Czech Republic. About 100 blood samples per year and region were analyzed using the HGA method. The internal and external quality controls of this method were performed throughout the duration of the study. In general, blood selenium concentrations (81.9 and 106.7 microg/l for median and 90th percentile, respectively) did not reach optimum values; in approximately 10% of the population sample, values lower than 60 microg/l were detected. Nonetheless, the values obtained increased significantly, with median concentrations of 73.2 microg/l in 1996 and 91.5 microg/l in 2001. The percentage of subjects with a whole blood selenium level of less than 60 microg/l also decreased from nearly 20% in 1996 to 0.2% in 2001. No substantial regional or gender-related differences were observed, but significantly lower blood selenium levels were found in smokers as opposed to nonsmokers. Although mild selenium deficiency continues to be observed, the data presented do not indicate extremely low selenium levels in the population sample.

Preischemic selenium status as a major determinant of myocardial infarct size in vivo in rats

Prospective epidemiological studies have shown that the incidence of numerous cardiovascular pathologies is correlated with body selenium status. However, it remains unclear whether selenium status also influences the outcome of myocardial infarction. The aim of the present study was to test whether dietary selenium intake affects myocardial necrosis induced by transient regional ischemia in vivo in rats. For this purpose, male Wistar rats received either a high-selenium (High-Se: 1.5 mg of Se/kg) or a low-selenium (Low-Se: 0.05 mg of Se/kg) diet for 10 weeks. Animals were subjected to 30 min of myocardial ischemia induced by coronary artery ligation followed by 60 min of reperfusion. Pre- and postischemic blood samples were collected for glutathione (GSH and GSSG) determination and for glutathione peroxidase (GSH-Px) assessment. Our results show that high-selenium intake reduces myocardial infarct size (High-Se: 25.16 +/- 1.19% versus Low-Se: 36.51 +/- 4.14%, p < 0.05), preserves postischemic GSH/GSSG ratio (High-Se: 1.37 +/- 0.37 versus Low-Se: 0.47 +/- 0.10, p < 0.05), increases plasma GSH-Px activity, and improves postischemic mean arterial pressure. In conclusion, preischemic body selenium status is a major determinant of the outcome of myocardial ischemia in vivo in rats probably because it influences the cellular redox status.

Effects of Se and Zn supplementation on the antagonism against Pb and Cd in vegetables

The antagonistic effects of supplementation of Zn and Se to the soil on vegetables were studied in this work. In the pot experiment, Se (Se4+) and Zn (Zn2+) were applied, respectively, to the soil, in which the Chinese cabbage (Brassica rapa) and the lettuce (Lactuca sativa L.) were planted. As a result, Se and Zn were enriched evidently in the two vegetables. The contents of Pb and Cd in the two vegetables were decreased markedly while contents of some healthy mineral elements, like Mn and Mg, were increased to some extent when Se and Zn were applied. The antagonism of Se and Zn against Pb and Cd in plants was suggested. The farmland experiment on the lettuce was conducted to explore further the effect of supplementation of Zn and Se under the actual field conditions. Result came out to be that the enrichment of Zn and Se restrained the accumulation of Pb and Cd in the lettuce remarkably, as well as enhanced the absorption of some other nutritional elements, like Fe, Mn, Cu, Ca and Mg. Therefore, application of Se and Zn was proved to be an effective and feasible method to improve trace elements nutrition in the vegetables.

Ascorbic acid recycling in human erythrocytes is induced by smoking in vivo

Tobacco smoke contains large numbers of radicals that burden the antioxidant defense and, thus, lower plasma antioxidants, in particular vitamin C or ascorbic acid, is commonly observed among smokers. Ascorbic acid recycling describes the process in which ascorbic acid is oxidized to dehydroascorbic acid by various pathways and subsequently reduced back to ascorbic acid intracellularly, e.g., in erythrocytes, thereby preserving the ascorbic acid pool. In humans who are unable to synthesize ascorbic acid, and in smokers in particular, who are prone to oxidation, this process must be very efficient and of great importance. It has previously been reported that isolated erythrocytes subjected to tobacco smoke in vitro had significantly lower ascorbic acid recycling as compared to controls. In contrast to these findings, we now report that freshly isolated erythrocytes from long-term smokers (n = 39) display a significantly increased rate of ascorbic acid recycling in vivo as compared to those isolated from nonsmokers (n = 31; p <.0001). Preliminary data suggests that the increase results from induction of dehydroascorbic acid reductase activity rather than from differences in energy status, glutathione content, or altered transport capacity. The induction of ascorbic acid recycling as a potential adaptation mechanism of the antioxidant defense to oxidative insults is discussed.

Glutathione peroxidase 1 activity and cardiovascular events in patients with coronary artery disease

BACKGROUND

Cellular antioxidant enzymes such as glutathione peroxidase 1 and superoxide dismutase have a central role in the control of reactive oxygen species. In vitro data and studies in animal models suggest that these enzymes may protect against atherosclerosis, but little is known about their relevance to human disease.

METHODS

We conducted a prospective study among 636 patients with suspected coronary artery disease, with a median follow-up period of 4.7 years (maximum, 5.4) to assess the risk of cardiovascular events associated with base-line erythrocyte glutathione peroxidase 1 and superoxide dismutase activity.

RESULTS

Glutathione peroxidase 1 activity was among the strongest univariate predictors of the risk of cardiovascular events, whereas superoxide dismutase activity had no association with risk. The risk of cardiovascular events was inversely associated with increasing quartiles of glutathione peroxidase 1 activity (P for trend <0.001); patients in the highest quartile of glutathione peroxidase 1 activity had a hazard ratio of 0.29 (95 percent confidence interval, 0.15 to 0.58; P<0.001), as compared with those in the lowest quartile. Glutathione peroxidase 1 activity was affected by sex and smoking status but retained its predictive power in these subgroups. After adjustment for these and other cardiovascular risk factors, the inverse association between glutathione peroxidase 1 activity and cardiovascular events remained nearly unchanged.

CONCLUSIONS

In patients with coronary artery disease, a low level of activity of red-cell glutathione peroxidase 1 is independently associated with an increased risk of cardiovascular events. Glutathione peroxidase 1 activity may have prognostic value in addition to that of traditional risk factors. Furthermore, increasing glutathione peroxidase 1 activity might lower the risk of cardiovascular events.

Does vitamin E supplementation prevent cardiovascular events?

In recent years, vitamin E has been investigated as a cardioprotective agent. Experimental studies have identified potential mechanisms by which vitamin E may inhibit the development of atherosclerosis, and observational studies of individuals without coronary disease suggest that vitamin E intake may prevent future cardiovascular events. Secondary prevention trials to date have demonstrated little benefit from vitamin E supplementation. It remains possible, however, that supplementation may be useful among certain high-risk groups, including those with nutritional deficiencies. Limited data from completed primary prevention trials also indicate minimal cardioprotection from vitamin E, but large-scale trials now in progress may yet show benefit. Results from ongoing trials will contribute powerfully to the totality of evidence on which to formulate both appropriate clinical recommendations for individual patients and a rational public health policy for the population as a whole. At this time, there is insufficient evidence for issuing a public health recommendation to use vitamin E supplements to prevent cardiovascular disease (CVD). Rather, increased intake of fruits, vegetables, and other antioxidant-rich foods should be promoted as part of a healthy diet because they provide nutritional benefits beyond any potential antioxidant effect. Moreover, even if found to reduce CVD risk, vitamin supplement use should be considered an adjunct, not an alternative, to established cardioprotective measures, such as smoking abstention, avoidance of obesity, adequate physical activity, and control of high blood pressure and hyperlipidemia.

Reduced inotropic heart response in selenium-deficient mice relates with inducible nitric oxide synthase

Atria from mice fed a selenium-deficient (Se(-)) diet have a diminished beta-adrenoceptor-inotropic cardiac response to isoproterenol or norepinephrine compared with atria from mice fed the same diet supplemented with 0.2 mg/kg Se as sodium selenite (Se(+)). This diminished response could be reversed by feeding Se(-) mice the Se(+) diet for 1 wk or by pretreatment with nitric oxide synthase (NOS) inhibitors such as N(G)-monomethyl-l-arginine or aminopyridine. Elevated serum concentrations of nitrite/nitrate as well as a threefold increase in the atrial NOS activity were seen in the Se(-) versus Se(+) mice. Western blotting and indirect immunofluorescence indicated an enhanced expression of inducible NOS in hearts from Se(-) mice. Increased expression and activity of NOS and increased nitrite/nitrate levels from Se(-) mice correlated with an impaired response to beta-adrenoceptor inotropic cardiac stimulation. Elevated nitric oxide levels may account for some of the pathophysiological effects of Se deficiency on the heart.

Effect of sodium selenite treatment on platelet aggregation of streptozotocin-induced diabetic rats

INTRODUCTION

There is a well-known association between diabetes and atherosclerosis. Platelets are involved in the development of atherosclerotic vascular diseases and play a key role in atherosclerotic complications. Diabetes mellitus is related to alteration in the homeostasis of selenium and the protective role of selenium against lipid peroxidation in diabetes is reported. In the present study, thrombin-induced platelet aggregation and thromboxane A2 (TxA2) formation in diabetes and the effect of sodium selenite were evaluated.

MATERIALS AND METHODS

Diabetes was induced by intraperitoneal injection of streptozotocin (STZ) in Wistar rats (n = 21). Thirty of them were used as control rats. A week after streptozotocin injection, 11 of the control rats and 12 of the diabetics were injected with 5 micromol/kg/day of sodium selenite for 4 weeks. Thrombin-induced aggregation of the platelets was evaluated by optical technique. Thromboxane B2 (TxB2), TxA2 metabolite, was measured by enzyme-linked immunoassay (EIA) in thrombin-induced platelets.

RESULTS AND CONCLUSION

The platelet aggregation and TxB2 level increased in diabetic rats. Sodium selenite reversed the increase in platelet aggregation and TxB2 and caused a small but significant (p < 0.05) decrease in the glucose level. The hyperaggregability of platelets in STZ-induced diabetic rats was thought to be related to the enhanced TxA2 formation of platelets. Increase in TxA2 formation implies lipid peroxidation. Sodium selenite decreased the TxA2 formation. Besides its antioxidative effect, further studies are needed to establish the insulin-like effect of selenite because of a small decrease in blood glucose.

Ultrastructural examination of rabbit aortic wall following high-fat diet feeding and selenium supplementation: a transmission electron microscopy study

Experiments were carried out to examine the changes occurring in the wall of rabbit aortae following high-fat diet (HFD) feeding as well as HFD + selenium supplementation. Male New Zealand White rabbits were divided into three groups-control, HFD-fed and HFD + Se supplementation-and were treated for three months. The study depicted that levels of serum total cholesterol and triglycerides were markedly increased in the HFD-fed group as compared with control animals. However, in the HFD + Se-fed group, these levels were markedly suppressed vis-à-vis animals fed on HFD only. Development of atherogenic and atheromatic plaques has been shown at the light microscopy level in HFD-fed rabbits, whereas these developments were not visible in the HFD + Se-fed rabbits. Transmission electron microscopy findings indicated altered ultrastructure in the endothelial cells of the intimal layer as well as smooth-muscle cells of the medial layer in HFD-fed animals. However, these findings indicated normal ultrastructure in most of the cells, with little ultrastructural alterations from animals supplemented with Se along with HFD feeding. The study on the whole depicted the ability of Se to inhibit the onset of progression of aortic disease and hence has relevance to its therapeutic potential.

Antioxidant vitamins and prevention of cardiovascular disease: epidemiological and clinical trial data

Naturally occurring antioxidants such as vitamin E, beta-carotene, and vitamin C can inhibit the oxidative modification of low density lipoproteins. This action could positively influence the atherosclerotic process and, as a consequence, the progression of coronary heart disease. A wealth of experimental studies provide a sound biological rationale for the mechanisms of action of antioxidants, whereas epidemiologic studies strongly sustain the "antioxidant hypothesis." To date, however, clinical trials with beta-carotene supplements have been disappointing, and their use as a preventive intervention for cancer and coronary heart disease should be discouraged. Only scanty data from clinical trials are available for vitamin C. As to vitamin E, discrepant results have been obtained by the Alpha-Tocopherol, Beta Carotene Cancer Prevention Study with a low-dose vitamin E supplementation (50 mg/d) and the Cambridge Heart Antioxidant Study (400-800 mg/d). The results of the GISSI-Prevenzione (300 mg/d) and HOPE (400 mg/d) trials suggest the absence of relevant clinical effects of vitamin E on the risk of cardiovascular events. Currently ongoing are several large-scale clinical trials that will help in clarifying the role of vitamin E in association with other antioxidants in the prevention of atherosclerotic coronary disease.