Zinc supplementation does not alter plasma homocysteine, vitamin B12 and red blood cell folate concentrations in French elderly subjects

BACKGROUND/AIMS

In ageing, low folates and vitamin B12 status are frequent and can explain the increase of plasma homocysteine level. Zinc is involved in the folates and vitamin B12 metabolism with opposite actions. The aim of this study was to investigate the effects of zinc supplementation on homocysteine and vitamin B12 plasma levels as well as red blood cell folate level in French ageing subjects participating in the ZENITH study.

METHODS

Apparently healthy middle-aged (55-70 years) and free-living older (70-85 years) subjects were enrolled. They were randomly allocated to three groups: 0, 15 or 30 mg Zn per day for 6 months as zinc gluconate in addition to their usual dietary intake.

RESULTS

At baseline, plasma homocysteine levels (15.2+/-3.5 micromol/L) in older people were higher than in the middle-aged subjects (12.7+/-2.7 micromol/L) and was negatively correlated with vitamin B12 values (p=0.0036, r=-0.215) and with RBC folate levels (p<0.0001, r=-0.30). These results are in agreement with previous data. However, we found no correlation between the biomarkers of zinc status and homocysteine, vitamin B12 or folate levels at baseline. Moreover, 6-month zinc supplementation did not modify homocysteine, vitamin B12 and RBC folate values in either of the groups.

CONCLUSIONS

Zinc supplementation at moderate doses do not lead to deleterious effect on folate or vitamin B12 status in ageing healthy free-living people, but does not have any beneficial effects on homocysteine metabolism either.

Should plasma homocysteine be used as a biomarker of venous thromboembolism? A case-control study

Mild or moderate hyperhomocysteinemia as a risk factor for venous thrombosis is still a matter of debate. The strength of this study is to bring a body of elements to evaluate whether hyperhomocysteinemia should be used as a biomarker for venous thromboembolism (VTE). These elements consist of a biological evaluation of several hematological risk factors, and an original control group made of patients with a negative Doppler ultrasonography. A total of 151 cases and 155 controls were included. Total plasma homocysteine level, MTHFR C677T polymorphism, inherited abnormalities of the natural anticoagulant system as well as plasma folate and cobalamin levels were determined. A total of 41 (27.2 %) of cases and only 9 (5.8%) of controls had at least one of the coagulation defects studied. No significant difference was observed for total homocysteine levels between the 2 groups: median (interquartile range) = 8.3 (7.2-10.8) micromol/L for cases and 8.4 (7-10.9) micromol/L for controls. We found significantly more plasma folates and/or cobalamin deficiencies in controls (18.3%) than in cases (8.6%). After adjustment for several variables significantly related to risk factors of VTE, hyperhomocysteinemia (>13.2 micromol/L) was not found statistically associated with VTE: odds ratio 1.36 (95% confidence interval, 0.52-3.54). The prevalence of the homozygous 677TT polymorphism in the MTHFR gene was not increased in cases compared with controls. Mild or moderate hyperhomocysteinemia does not seem to be a strong determinant in VTE not only when the control group does not exclusively include healthy persons but also in investigated disease-free (thromboembolic disease) controls.

Effect of zinc supplementation on vitamin status of middle-aged and older European adults: the ZENITH study

OBJECTIVE

To assess the effects of zinc supplementation on vitamin status in middle-aged and older volunteers.

SUBJECTS/METHODS

Three hundred and eighty-seven healthy middle-aged (55-70 years) and older (70-85 years) men and women, randomly allocated to three groups to receive 15 or 30 mg Zn/day or placebo for 6 months. Dietary intake was assessed by means of a validated 4-day recall record. Fasting blood samples were simultaneously analysed for levels of plasma retinol and alpha-tocopherol by high-performance liquid chromatography. Erythrocyte folates were measured by a competitive immunoassay with direct chemiluminescence detection on an automatized immunoanalyser. Biochemical measurements were performed at baseline and after 3 and 6 months of zinc supplementation.

RESULTS

Plasma vitamin A levels were significantly increased proportionally with zinc dose and period of treatment, particularly at 6 months (for 15 mg Zn/day, P<0.05; for 30 mg Zn/day, P<0.0001); no significant changes were observed in the placebo group. There was no effect of zinc supplementation on vitamin E/cholesterol ratio and erythrocyte folates.

CONCLUSIONS

Our results show that a long-term zinc supplementation increases plasma vitamin A levels in middle-aged and older people of similar characteristics to those involved in this study. Moreover, supplementation influences serum zinc levels but does not affect erythrocyte zinc concentration and both plasma vitamin E and erythrocyte folate status.

[Evaluation of plasmatic homocysteine determination by gas chromatography-mass spectrometry]

Total plasma homocysteine emerged in the past few years as an independent risk factor for cardiovascular diseases. This test is now currently prescribed for the diagnosis of unexplained thrombosis in young adults or recurrent thrombosis in patients with arteriopathy. This sulphured amino-acid is an important intermediate in transsulfuration and remethylation pathways of methionine metabolism. Within the context of a collaboration between Monastir and Grenoble Universities and because a gas chromatograph mass spectrometer (GC-MS) instrument was available in Monastir, we proposed to transpose a GC-MS method previously developed in Grenoble's hospital for this parameter and to validate it by comparison with the liquid chromatography tandem mass spectrometry (LC-MS-MS) method, used at present. Analytical performances were good: detection limit 0.4 micromol/L and linear range up to 4 mg/L (29.6 micromol/L), and between-run and within-run precision with coefficients of variation < 5% and < 8 %, respectively. The comparison with LC-MS-MS method showed a good correlation (y = 0.9874 x -0.208; r(2) = 0.84). Mean difference from LC-MS-MS was -0.4 micromol/L. Plasma concentrations of homocysteine (mean + SD) determined among Tunisian adults, 29 men, 27 women, of the same age were respectively: 11.6 +/- 2.4 micromol/L and 10.1 +/- 2.7 micromol/L, p = 0.025. This method is now currently used to evaluate tHcy concentration in patients with risk factors for cardiovascular disease.

Hyperhomocysteinaemia is associated with osteoporosis in patients with Crohn's disease

BACKGROUND

A high prevalence of osteoporosis is observed in Crohn's disease. Recent data have shown that homocysteinaemia is an important risk factor in low-bone mineralization and fracture.

AIM

To look for an association between homocysteinaemia and low-bone mineralization in Crohn's disease patients.

PATIENTS AND METHODS

Ninety-two consecutive patients (sex ratio M/F 0.87; mean age: 36.6 +/- 13.2 years) were recruited between 2003 and 2005. Bone densitometry was performed on inclusion. The following parameters were analysed: age, sex, Crohn's Disease Activity Index, duration and extent of Crohn's disease, smoking status, corticosteroid treatment, immunosuppressive drugs, plasma homocysteine, folate and vitamin B12 concentration.

RESULTS

The prevalence of a high homocysteine level (>15 micromol/L) was 60%. Osteoporosis and low-bone mineralization observed in 26 (28%), and 60 (65%) patients, respectively. On a multivariate analysis, associated factors for osteoporosis and low-bone mineralization were respectively: hyperhomocysteinaemia (OR: 61.4; CI: 95: 23-250; P < 0.001), and ileal Crohn's disease [OR: 13.8; CI: 95: 2.5-150; P = 0.036] for osteoporosis and hyperhomocysteinaemia [OR: 63.7; CI: 95: 8.5-250; P < 0.001] and disease duration of at least 5 years [OR: 11.4; CI: 95: 1.31-99; P = 0.039] for low-bone mineralization. Results were similar whichever site osteoporosis was detected.

CONCLUSION

Hyperhomocysteinaemia was observed in 60% of our Crohn's disease patients and was strongly associated with low-bone mineralization and osteoporosis (OR: 61.4).

A robust liquid chromatography tandem mass spectrometry method for total plasma homocysteine determination in clinical practice

BACKGROUND

Total plasma homocysteine has emerged as an independent risk factor for vascular disease. To meet increasing requests by clinicians for this homocysteine determination, a rapid assay for a routine use has been developed.

METHODS

A robust, stable, isotope-dilution liquid chromatography tandem mass spectrometry (LC/MS/MS) method is described, including all the practical details and analytical performance results.

RESULTS

The method allows homocysteine quantitation over a linear working range up to 100 micromol/L, with the limit of quantification estimated at a low value of 0.09 micromol/L. Total analytical imprecision is less than 4%. Accuracy was assessed by measuring the homocysteine concentration in a serum Standard Reference Material.

CONCLUSIONS

The method was demonstrated to be quick, reliable and cheap after 1 year of use on a time-shared instrument in our hospital unit.

Cross-sectional association between homocysteine and motor function in the elderly

OBJECTIVE

To determine if there is a cross-sectional association between homocysteine (tHcy) level and measures of gait and balance in elderly subjects.

METHODS

We studied 3,609 noninstitutionalized subjects aged 65 to 85 years from the Dijon (France) center of the Three-City Study. tHcy concentration was measured from fasting blood samples. Motor function was assessed by measuring walking speed and by using a modified version of the Tinetti scale.

RESULTS

After adjustment for confounders, mean maximum walking speed (MWS) decreased with increasing tHcy levels (p = 0.001). The odds ratio (OR) (95% CI) for having a MWS below the 40th percentile was 1.9 (1.4 to 2.5) in subjects with tHcy levels in the upper quintile compared with those in the lowest quintile. Compared with subjects in the lowest tHcy quintile, the OR for having a modified Tinetti score below 16 ranged from 1.0 (0.8 to 1.4) in the second quintile to 1.9 (1.3 to 2.6) in the upper quintile (p < 0.0001).

CONCLUSIONS

Elevated homocysteine concentrations are associated with worse motor performances in the elderly. These findings support the hypothesis of a vascular contribution to motor function.

Estimation of intake and status of vitamin A, vitamin E and folate in older European adults: the ZENITH

OBJECTIVE

To report selected dietary intake and vitamin status at baseline of volunteers participating in the ZENITH study and the correlation of vitamin status with zinc.

DESIGN

A multicentre prospective intervention study employing a randomised double-blind design.

SETTING

Clermont-Ferrand, Theix (France), Coleraine (Northern Ireland), Grenoble (France), Rome (Italy).

PARTICIPANTS

In total, 387 healthy middle-aged (55-70 y) and older (70-87 y) men and women participated in the study.

METHODS

Dietary intake was assessed by means of a validated 4-d recall record. Fasting blood samples were simultaneously analysed for retinol and alpha-tocopherol by the HLPC method. Erythrocyte folates were measured by a competitive immunoassay with direct chemiluminescence detection on an automatised immunoanalyser.

RESULTS

In all centres, men had a significantly (P < 0.0001) higher mean nutrient intake than women. Comparison between age-groups showed that older individuals had significantly lower intakes of macro- and selected micronutrients than middle-aged subjects (P < 0.0001). A high fat intake (from 36 to 40% of total energy) was observed in all examined groups. In relation to biochemical measures of vitamin status, all parameters were above their respective cut-off values for normality and, thus, none of the subjects had biochemical evidence of deficiency of these selected vitamins. A moderate correlation was found with plasma vitamin A and serum zinc (r = 0.12, P < 0.05) or red blood cell zinc (r = 0.12, P < 0.01) and with erythrocyte folates and red blood cell zinc (r = 0.11, P < 0.05).

CONCLUSIONS

There were only moderate differences in the nutrient intake of the ZENITH study volunteers among the four European centres. Their biochemical status for retinol, alpha-tocopherol and folate appeared adequate.

Kinetic Changes of Oxidative Stress and Selenium Status in Plasma and Tissues following Burn Injury in Selenium-Deficient and Selenium-Supplemented Rats

BACKGROUND

This study investigates the relationship between the burn-induced oxidative stress and the selenium status.

METHODS

The rats were fed with a selenium-adequate diet or a selenium-depleted diet for 5 weeks, before a third-degree thermal injury was applied to the animals. One group of selenium-depleted animals received injections of sodium selenite after the injury. The selenium status and the oxidative stress parameters were measured for 5 days.

RESULTS

The selenium-deficient diet leads to oxidative stress with a high stimulation of the superoxide dismutase activity. After the burn injury, the oxidative stress appears important because the initial selenium status is already impaired and, in all animals, the selenium levels and the antioxidant seleno-dependent glutathione peroxidase (GPx) activity decrease in the plasma and the tissues. A treatment with daily selenium injections is efficient in normalizing selenium levels and restores the GPx activity, but fails to counteract the initial oxidative damages induced by the selenium-deficient diet.

CONCLUSIONS

The selenium status before the burn injury is a modulating factor of the burn-induced oxidative stress. A single selenium supplement is not sufficient to counteract these oxidative damages and henceforth combined antioxidant supplementations should be investigated to improve the early treatment of the burn patients.

Hyperhomocystéinémie et facteurs associés au cours des MICI : étude prospective chez 81 patients

BACKGROUND

A high prevalence (52%) of hyperhomocysteinemia is observed in Crohn disease (CD), however it is not well documented in ulcerative colitis (UC). Furthermore, in the different works studying hyperhomocysteinemia the associated factors are different.

AIM

Prospective evaluation of hyperhomocysteinemia in inflammatory bowel disease (IBD) patients, of the risk factors and the determination of a potential risk of colorectal carcinoma in case of hyperhomocysteinemia.

PATIENTS AND METHODS

IBD patients followed in our department were prospectively recruited between November 2003-September 2004. To be included patients should have passed a coloscopy in the two years. Patients with kidney failure or drugs supposed, to interfere with homocystéine metabolism (folates, vitamin B12, methotrexate) were excluded from the study. The following parameters were analysed: age, sex, clinical activity indexes (CDAI for Crohn disease and CAI for ulcerative colitis), length-extent and type of the disease (CD or UC), smoking, plasma homocystein concentration, folates and vitamin B12.

RESULTS

Eighty-one patients (60 CD, 21 UC, mean age 43.8 +/- 17.3) were included, 30 had an active disease at inclusion and 16 were smokers. The prevalence of high homocystein concentration was 55.6%. In univariate analysis a low rate of folates was the only risk factor for a high homocystein concentration (74 vs. 52.8%; P = 0.018). Smoking was almost an associated factor. In multivariate analysis, a low rate of folate was the only risk factor of hyperhomocysteinemia, OR = 3.59 [1.27-10.17]. Five endoscopic lesions considered as precancerous were described; these patients had all a hyperhomocysteinemia.

CONCLUSION

The prevalence of hyperhomocysteinemia is high in UC and in CD. A low folate rate is the only risk factor observed in our study. There is a possible link between colorectal cancer and hyperhomocysteinemia. A high Plasma homocystein concentration must be search in inflammatory bowel disease patients and a substitutive treatment of folates and vitamin B12 is necessary in case of hyperhomocysteinemia.

Hyperhomocystéinémie sévère révélant une homocystinurie chez deux jeunes adultes présentant un phénotype peu marqué

INTRODUCTION

To the request of total plasma homocysteine determination in the investigation of vascular disease, diagnosis of homocystinuria in young adult patients with mild phenotype is not so rare.

EXEGESIS

A 26-year-old man developed embolic cerebral infarction and a 22-year-old woman presented a right renal venous thrombosis one week after delivery. In each case, high concentration of total plasma homocysteine was first found and plasma and urinary amino acids analysis later on directed the diagnosis towards homocystinuria. Finally, reduced skin fibroblast cystathionine beta-synthase activity confirmed the diagnosis of homocystinuria.

CONCLUSION

Total plasma homocysteine determination must be determined for screening for hyperhomocysteinemia in young adults with venous thromboembolism without characteristic phenotypic features of homocystinuria.

Homocysteine is not associated with arterial thickness and stiffness in healthy middle-aged French volunteers

BACKGROUND

To study the association between the total plasma homocysteine (tHcy) concentration and the carotid artery intima-medial wall thickness (IMT), pulse wave velocity (PWV) and the presence of arterial plaques in a French population.

METHODS

Cross-sectional analysis of data from 556 male and 559 female middle-aged participants (mean (+/-SD) age 59.6+/-4.7 years) provided by an ongoing intervention trial.

RESULTS

Mean geometric tHcy concentration was higher for men than for women (10.6 vs. 8.5 micromol/L, p<0.001) and was associated in the expected direction with known determinants. The mean IMT was 0.71+/-0.1 mm for men and 0.69+/-0.1 mm for women (p<0.001), the mean PWV was, respectively, 12.0+/-2.8 and 10.9+/-2.2 m/sec (p<0.001), and the percentages of subjects with plaques were, respectively, 40.8% and 22.7% (p<0.001). In men only, the age-adjusted mean IMT and PWV increased with an increasing tHcy concentration: the IMT was 0.71 mm in the first tHcy-quartile and 0.73 mm in the fourth tHcy-quartile (p for linear trend=0.03), the PWV values were, respectively, 11.6 and 12.4 m/sec (p for linear trend=0.01). These associations disappeared after adjustment for conventional cardiovascular disease risk factors.

CONCLUSION

In this population, the tHcy concentration was not associated with measures of arterial thickness and stiffness.

[Belated decompensation of an Imerslund-Grasbeck disease]

Imerslund-Gräsbeck disease is an autosomic recessive disease characterised by a megaloblastic anemia due to a vitamin B12 deficiency and by a moderate proteinuria without kidney failure. It is caused by the malabsorption of Cobalamin-intrinsic factor complex bringing into play cubulin and other proteins (megaline, amnioless), some mutations of which are described at present. We report herein the observation of a child whose diagnosis was made belatedly during an acute decompensation with biological hemophagocytic syndrome. Its evolution was marked by the appearance of neurological disorders at the beginning of the vitamin B12 substitution treatment. These disorder regressed as the dosage was increase. The purpose of this observation is to recapitulate the main characteristics of this disease and to review the current data.

Mitochondrial production of reactive oxygen species and incidence of age-associated lymphoma in OF1 mice: Effect of alternate-day fasting

There is currently of a great interest investigating the role of nutrition in the prevention of age-associated disorders. The present study aimed to evaluate, on a particular strain of mice, the efficacy of alternate-day fasting on the mitochondrial production of free radical species and on the incidence of a specific cancer (lymphoma) in aged mice. Alternate fasting, that was initiated in middle age mice through a 4 month period, reduced significantly the incidence of lymphoma (0% versus 33% for controls). No remarkable difference was observed in the overall food consumption between alternate-fed (AF) and ad libitum (AL) mice, suggesting that the efficacy of alternate fasting did not really depend on calorie restriction. A significant decrease in the mitochondrial generation of reactive oxygen species (ROS) that was associated with a significant increase in spleen mitochondria SOD activity was observed when mice were maintained on intermittent fasting. Our results suggest that alternate fasting could exert a beneficial antioxidant effect and a modulation of the oxidative stress associated with aging.

Optimization of selenium status by a single intraperitoneal injection of Se in Se-deficient rat: possible application to burned patient treatment

In order to investigate the efficiency of a single selenium (Se) administration in restoring selenium status, Se and antioxidant enzymes were studied in an animal model of Se depletion. In Se-depleted animals receiving or not a single parenteral administration of Se, plasma, red blood cell (RBC), and tissue Se levels were measured concurrently with glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities. The oxidative stress was assessed by thiobarbituric acid-reactive species (TBARs), total thiol groups, glutathione, and tocopherol measurements. Our study showed that Se depletion with alterations in the antioxidant defense system (Se and GPx activity decreases) led to an increase of lipid peroxidation, a decrease of the plasma vitamin E level, and SOD activation. Sodium selenite injection resulted after 24 h in an optimal plasma Se level and a reactivation of GPx activity. In liver, brain, and kidney, Se levels in injected animals were higher than those in reference animals. However, this single administration of Se failed to decrease free radical damage induced by Se depletion. Therefore, in burned patients who exhibit an altered Se status despite a daily usually restricted Se supplementation, the early administration of a consistent Se amount to improve the GPx activity should be of great interest in preventing the impairment of the antioxidant status.

Rapidly exchangeable pool study of zinc in free-living or institutionalized elderly women

OBJECTIVE

We evaluated the effect of age and institutionalization on zinc metabolism by using a stable isotope technique.

METHODS

This was a randomized case-control study. Three groups were recruited: nine young women (group 1, ages 36+/-1 y) as controls, nine free-living elderly women (group 2, ages 72+/-2 y), and nine institutionalized women (group 3, ages 73+/-2 y). Only women were recruited to obtain homogeneous groups. The study was set in a Valence hospital (France) in the geriatric department (headed by Dr. Ferry). The experimental design of the study was reviewed and approved by the local ethical committee, and all participants signed a consent form. No subject dropped out of the study. A zinc stable isotope label (0.73 mg of (70)Zn) was injected intravenously into patients and measured by inductively coupled plasma mass spectrometry.

RESULTS

Decay curves of the plasma (70)Zn followed a one-compartment kinetic leading to the determination of one pool. The size of this pool suggested that it corresponded to the liver compartment. The size of this pool was significantly smaller in elderly people. (70)Zn plasma resident time was significantly longer in elderly individuals, and shorter in institutionalized than in free-living elderly subjects.

CONCLUSION

These data suggest that the zinc metabolism of elderly women is related to lifestyle or its consequences and to age. Moreover, we have demonstrated that kinetic studies using stable isotopes of zinc can provide novel information on exchangeable zinc pools in clinical situations.

Plasma homocysteine is related to folate intake but not training status

BACKGROUND AND AIM

Lifestyle including intakes of several essential nutrients and physical activity are of particular interest in reducing plasma total homocysteine concentration (tHcy), a risk factor for cardiovascular diseases. The aim of this study was to determine in athletes, whether dietary factors such as intakes of folate, vitamin B6 and B12 were associated with lower plasma tHcy, and whether this depended on daily energy expenditure (EE) and type of physical activity performed (aerobic, anaerobic, intermittent).

METHODS

Seventy-four well-trained athletes completed 7-day food and activity records in a cross-sectional study. Blood was sampled on day 8.

RESULTS

Percentage of vegetal protein, vitamin B6, and folate intakes were higher and tHcy was lower (1) in athletes with high EE (> 16.72 MJ/d) compared to athletes with lower EE; (2) in aerobic athletes compared to intermittent athletes and sedentary subjects. After backward step by step analysis, folate intake was the only significant variable retained in the model to explain tHcy variability. Moreover, after introducing folate intake as a covariate in ANOVA tests, group effects on tHcy were no longer significant. Nutrient density of folate was inversely correlated to tHcy in athletes (r = -0.33; P = 0.004).

CONCLUSION

High energy intake (> 16.72 MJ/d) allows the necessary folate intake (> 500 microg/d) for tHcy decrease to occur, which is moreover favored by aerobic activity. The mechanism underlying low tHcy in relation to high EE could only play a minor role when compared to the effect of dietary folate intake on tHcy.

Evaluation of Advia Centaur automated chemiluminescence immunoassay for determining total homocysteine in plasma

BACKGROUND

A lot of methods are now available for total plasma homocysteine (tHcy) determination. HPLC with fluorescence detection were the most widely used methods until recently but immunoassays, easier to use, currently supplant in-house laboratory methods.

METHODS

The latest commercial automated chemiluminescence immunoassay (ICL) for tHcy, developed on the ADVIA Centaur analyzer (Bayer Diagnostics), was fully evaluated and compared with a current HPLC method.

RESULTS

The ICL-ADVIA Centaur method had a detection limit <0.9 micromol/l and was linear for tHcy between 2.4 and 58.8 micromol/l. The within- and between assay imprecision was <6% and <7%, respectively. The analytical recovery ranged from 93.5% to 109.7%. The comparison of 168 clinical plasma specimens indicated a good correlation between the two methods (r=0.96, p<0.0001) but a systematic positive bias for ICL-ADVIA Centaur method (mean difference=3.0 micromol/l).

CONCLUSIONS

The ADVIA Centaur method is a useful and practicable alternative to HPLC methods for tHcy determination. The ICL method is even more convenient than chromatographic methods for routine use because of its significantly higher throughput (200 samples/h vs. 40 per 24 h). However, the agreement among methods is insufficient to allow them to be used interchangeably.

Influence of Short-Chain Fructo-Oligosaccharides (sc-FOS) on Absorption of Cu, Zn, and Se in Healthy Postmenopausal Women

OBJECTIVE

This study was carried out to evaluate the effect of short-chain fructooligosaccharides (sc-FOS) on the absorption of Cu, Zn, and Se among postmenopausal women who are potential candidates to subclinical trace element deficiencies.

DESIGN

A randomized double blind cross-over study.

SETTING

This study was carried out at the Human Nutrition Research Center, Clermont-Ferrand, France.

SUBJECTS

11 postmenopausal women aged 53-70 y, not taking hormone replacement therapy were enrolled and completed the study.

INTERVENTIONS

Diets with 10 g/day sc-FOS or placebo were given for 5 weeks each in random order followed by a wash-out period of at least 3 weeks. At the end of each period, stable isotopes (3.19 mg 67Zn as ZnCl2, 2.06 mg 65Cu as CuCl2 and 52.3 microg 74Se as sodium selenite) and radiopaque pellets (as fecal excretion index) were administered during lunch. Stools were collected for the next 5-7 days. Isotopes were determined by ICP-MS (Cu and Zn) or GC-MS (Se).

RESULTS

Copper absorption was significantly enhanced (p = 0.042) by sc-FOS. No effect of sc-FOS was observed on Zn, and Se absorption.

CONCLUSION

To our knowledge, this is the first study on the influence of sc-FOS on trace element metabolism. The observed increase in copper absorption may be of interest regarding daily copper requirements in menopausal women. However, the relevance of this observation remains to be established.

Selenium status as determinant of connexin-43 dephosphorylation in ex vivo ischemic/reperfused rat myocardium

Recent studies have demonstrated that electrical uncoupling at gap junctions during ischemia is associated with cardiac Connexin-43 (Cx43) dephosphorylation. Whether oxidative stress is involved in this phenomenon still remains unclear. In the present study, we examined the influence of selenium intake on reperfusion-induced Cx43 dephosphorylation. Male Wistar rats were fed a diet containing either 0.05 mg/kg (Low-Se, n = 13) or 1.5 mg/kg (High-Se, n = 11) selenium for 8 weeks. At the end of this diet, hearts were isolated and subjected to 10 min regional ischemia followed by 10 min reperfusion. The level of dephosphorylated Cx43 was determined in tissue samples from ischemic/reperfused and non-ischemic regions of the hearts. At the end of the experiemental diet, the activity of the antioxidant enzyme glutathione peroxidase (GSH-Px) was increased in high-Se hearts compared with low-Se hearts (+ 13%; p < 0.05). After ischemia/reperfusion, in low-Se hearts, Cx43 dephosphorylation appeared significantly increased in the left ventricle compared to the non-ischemic right ventricle (+ 149%; p < 0.05). The high-Se diet significantly reduced Cx43 dephosphorylation in the left ventricle (p < 0.05 vs. low-Se diet). In conclusion, our results suggest that oxidative stress may be involved in Cx43 dephosphorylation during myocardial ischemia/reperfusion, thereby contributing to arrhythmogenesis.

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.

First survey of fungi in hypersaline soil and water of Mono Lake area (California)

Mono Lake is a closed lake located in central California, east of the Sierra Nevada mountains. It contains dissolved carbonates, sulfates and chlorides at high concentrations. Due to its high salinity, Mono Lake was sometimes compared to the Dead Sea. However, it appears that Mono Lake water and vicinity abound with life. In this work, the fungal flora living in this extreme ecosystem was studied for the first time. Soil, tufa, water and sediment samples were also analyzed for their mineral and salt composition. Results showed that water was particularly rich in sodium, potassium, phosphorus and boron. Soil and sediments contained very high levels of calcium and magnesium, but also barium, boron and strontium. Sodium, phosphorus and iron levels varied in a large extent from one to another sample. Neutral to very alkaline pH were recorded. Water samples were found sterile in the conditions chosen for fungi isolation, while sediment, soil and tufa samples led to the isolation of a total of 67 fungal species (from 23 samples), belonging to various taxonomic groups. From our results no clear effects of the chemical parameters of the samples were observed on fungal life apart from the pH. The methods chosen did not allow the isolation of extremely halotolerant species. We isolated in this work a series of ubiquitous species, suggesting that a selection of resistant and/or adaptable strains of some common species could have occurred. Depending on the medium and the temperature of isolation, it can be hypothesized that some species were present as dormant structures, while some others, isolated at pH 8 on a medium enriched in Na and Ca, could be in a growing form adapted to alkaline and saline conditions. This work contributes to a better knowledge of the mycobiota present in the Mono Lake's ecosystem.

Early evolution of selenium status and oxidative stress parameters in rat models of thermal injury

The objective of the present study was to measure the relationship between selenium status and oxidative stress in two rat models of thermal injury. A non-lethal third-degree burn injury involving 20% (experiment 1) or 40% (experiment 2) of total body surface area (TBSA) was applied to male Wistar rats. Selenium level, glutathione peroxidase (GPx) activity in plasma, red blood cells (RBC) and tissues (liver, kidney, muscle, and brain), and plasma selenoalbumin (Se-alb) were measured in control rats and in burned rats respectively 6 hours after injury and daily from day 1 to day 5. In parallel, lipid and protein oxidative damages, monitored by plasma and tissue thiobarbituric acid reactive species (TBARs) levels and plasma total thiol groups were assessed. We observed a decrease of plasma Se and Se-albumin 6 hours after burn injury. In parallel, plasma GPx activity rapidly decreased and remained significantly lower than in control rats. These alterations were enhanced by the burn injury severity. Plasma TBARs followed the same pattern as that of plasma cholesterol, with an initial decrease and an increase at day 3 in 40% TBSA burned rats. Plasma thiol groups decreased in the two experiments indicating plasma protein oxidation. These results confirm an early oxidative stress in burn injury, and suggest an early selenium mobilization, which might counteract this oxidative stress. These data underline the crucial need of a restored selenium status in burned patients immediately after the burn injury.