Selenium in Australia: selenium status and biofortification of wheat for better health

Chasing high and stable wheat grain mineral content: Mining diverse spring genotypes under induced drought stress

Climate change-induced drought has an effect on the nutritional quality of wheat. Here, the impact of drought at different plant stages on mineral content in mature wheat was evaluated in 30 spring-wheat lines of diverse backgrounds (modern, old and wheat-rye-introgressions). Genotypes with rye chromosome 3R introgression showed a high accumulation of several important minerals, including Zn and Fe, and these also showed stability across drought conditions. High Se content was found in genotypes with chromosome 1R. Old cultivars (K, Mg, Na, P and S) and 2R introgression lines (Fe, Ca, Mn, Mg and Na) demonstrated high mineral yield at early and late drought, respectively. Based on the low nutritional value often reported for modern wheat and negative climate effects on the stability of mineral content and yield, genes conferring high Zn/Fe, Se, and stable mineral yield under drought at various plant stages should be explicitly explored among 3R, 1R, old and 2R genotypes, respectively.

Selenoproteins in Health

Selenium (Se) is a naturally occurring essential micronutrient that is required for human health. The existing form of Se includes inorganic and organic. In contrast to the inorganic Se, which has low bioavailability and high cytotoxicity, organic Se exhibits higher bioavailability, lower toxicity, and has a more diverse composition and structure. This review presents the nutritional benefits of Se by listing and linking selenoprotein (SeP) functions to evidence of health benefits. The research status of SeP from foods in recent years is introduced systematically, particularly the sources, biochemical transformation and speciation, and the bioactivities. These aspects are elaborated with references for further research and utilization of organic Se compounds in the field of health.

Characterization of Triticum turgidum sspp. durum, turanicum, and polonicum grown in Central Italy in relation to technological and nutritional aspects

Introduction

Wheat is a staple food, with the two most common species being Triticum aestivum and Triticum turgidum ssp. durum. Moreover, the latter, T. turgidum, includes other tetraploid subspecies, among which the sspp. turanicum (Khorasan wheat) and polonicum (Polish wheat), whose importance has increased in the last decades, representing alternative crops for marginal areas, in addition to being a source of genetic diversity.

Methods

In this work, different accessions of these three subspecies of T. turgidum have been grown in 2 years in the same environment and have been characterized for technological properties and factors affecting nutritional quality, such as fiber amount and the content of micro- and macro-nutrients in grains, and for root morphological traits.

Results

These analyses allowed the identification, in particular, of a Polish wheat accession showing better technological performances, a higher amount of positive micro- and macro-elements, and a lower amount of toxic cadmium. The modern variety Svevo and the Polish Pol2 showed the lowest and the highest shoot:root ratio, respectively. The high shoot:root ratio in Pol2 was mainly attributable to the decrease in root growth. Although Pol2 had a lower root biomass, its particular root morphology made it more efficient for nutrient uptake, as evident from the greater accumulation of micro- and macro-nutrients.

Discussion

These results underline that it is not possible to draw general conclusions about the difference between primitive and modern wheats, but rather a case-by-case approach should be chosen.

Determination of toxic metal burden and related risk factors in pregnant women: a biological monitoring in Sabzevar, Iran

Nowadays, the adverse effect of toxic metals on humans is well known, especially in the fetal period such as preventing cognitive development and congenital abnormalities of the central nervous system. Hence, this study aims to evaluate the toxic metal burden in mothers and newborns in Sabzevar. Obtained data can be useful for authorities in public health issues. To determine heavy metals in placental blood and umbilical cord blood, one hundred eighty blood samples were taken from ninety mothers referred to Shahidan Mobini Hospital for delivery. The amount of metals in samples was analyzed using inductively coupled plasma optical emission spectrometry (ICP OES). The results of this study revealed that 21.52%, 26.19%, and 60.71% of maternal blood samples (placental blood) and 16.47%, 56.47%, and 20% of umbilical cord blood samples were higher than the US center for disease control (CDC) recommended levels for Pb, Cd, and As respectively. According to the multiple linear regression analysis, the Pb (p = 0.054), As (p < 0.001), and Se (p < 0.001) levels had an association with the mother's living area. Also, there was a significant association between Se (0.021) and the age of the mother. However, the Se values in its optimum concentrations in the blood (60-140 μg/L) can decrease the adverse effects of toxic metals, 72.5% of the pregnant women had Se values below the 60 μg/L and only 6% of pregnant women had Se levels higher than 140 μg/L. We concluded that the mothers inhabiting the rural areas need more Se sources in their diets.

Meta-QTLs, ortho-MetaQTLs and candidate genes for grain Fe and Zn contents in wheat (Triticum aestivum L.)

Majority of cereals are deficient in essential micronutrients including grain iron (GFe) and grain zinc (GZn), which are therefore the subject of research involving biofortification. In the present study, 11 meta-QTLs (MQTLs) including nine novel MQTLs for GFe and GZn contents were identified in wheat. Eight of these 11 MQTLs controlled both GFe and GZn. The confidence intervals of the MQTLs were narrower (0.51-15.75 cM) relative to those of the corresponding QTLs (0.6 to 55.1 cM). Two ortho-MQTLs involving three cereals (wheat, rice and maize) were also identified. Results of MQTLs were also compared with the results of earlier genome wide association studies (GWAS). As many as 101 candidate genes (CGs) underlying MQTLs were also identified. Twelve of these CGs were prioritized; these CGs encoded proteins with important domains (zinc finger, RING/FYVE/PHD type, flavin adenine dinucleotide linked oxidase, etc.) that are involved in metal ion binding, heme binding, iron binding, etc. qRT-PCR analysis was conducted for four of these 12 prioritized CGs using genotypes which have differed for GFe and GZn. Significant differential expression in these genotypes was observed at 14 and 28 days after anthesis. The MQTLs/CGs identified in the present study may be utilized in marker-assisted selection (MAS) for improvement of GFe/GZn contents and also for understanding the molecular basis of GFe/GZn homeostasis in wheat.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01149-9.

Supranutritional selenium suppresses ROS-induced generation of RANKL-expressing osteoclastogenic CD4+ T cells and ameliorates rheumatoid arthritis

OBJECTIVE

The benefit of Se supplementation in rheumatoid arthritis (RA) has been tested in clinical trials, but results remain inconclusive. The objective of this study was to specifically investigate the potential benefit of supranutritional Se by examining human samples from an area with supranutritional Se intake and testing a mouse model of RA.

METHODS

Peripheral blood mononuclear cells (PBMCs) from RA patients (N = 57) and healthy controls (HC, N = 71) from an area of supranutritional Se intake (Enshi, Hubei, China) were analysed by flow cytometry. Serum cytokine and Se levels were measured by cytometric beads array (CBA) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. With sufficient or supranutritional selenium intake, mice were induced with collagen-induced arthritis (CIA) and examined for disease activity and immunopathology. The influence of Se supplementation in the generation of RANKL-expressing osteoclastogenic CD4+ T cells was investigated by in vitro assays.

RESULTS

In Enshi city, HC showed the above-normal concentrations of serum Se concentrations while RA patients were enriched in the normal range (70-150 ng mL-1) or below. RA patients with higher Se levels demonstrated milder disease and lower levels of C-reactive protein, IL-6, RANKL and Th17 cells. In the mouse CIA model, supranutritional Se supplementation delayed disease onset, ameliorated joint pathology and reduced CD4+CD44+RANKL+ T cells. Se supplementation could suppress RANKL expression in cultured mouse Th17 cells.

CONCLUSION

Supranutritional Se suppresses RANKL-expressing osteoclastogenic CD4+ T cells and could be beneficial to RA, which warrants formal testing in randomised clinical trials.

Distribution, accumulation and speciation of selenium at the different growth stages of four garlic clones

Selenium (Se) is an essential micronutrient for humans. Garlic (Allium sativum L.) metabolises Se into important Se-amino acids like Se-methylselenocysteine (Se-MetSeCys), precursor of methylselenol, an active species for cancer prevention. Therefore, the Se accumulation and speciation in garlic were studied to evaluate their relations with growth stages and types of plant clones. Four garlic clones (Nieve INTA, Union FCA, Gostoso INTA and Rubí INTA) were fortified with a Se solution (169 g Se L^-1). The association of Se to different molecular weight fractions was evaluated by size-exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP-MS) detection. Also, anion exchange chromatography (AEC-ICP-MS) was used for the determination of Se-amino acids, while their identification was performed by ESI-MS/MS. The Se was incorporated into high (7-5 kDa) and low (2-4 kDa) molecular weight fractions. The presence of Se-MetSeCys was observed mostly. Se-MetSeCys increased in bulbs to a maximum value but increased, then decreased, in leaves and roots. The Se-organic species were mostly found in bulbs in the last growth stage. Garlic showed a significant ability to accumulate and metabolise Se, specially, the red clones (Gostoso INTA and Rubí INTA). Also, this work suggests that this plant may become an attractive source of Se-amino acids with important biological properties.

Biofortification and bioavailability of Zn, Fe and Se in wheat: present status and future prospects

Knowledge of genetic variation, genetics, physiology/molecular basis and breeding (including biotechnological approaches) for biofortification and bioavailability for Zn, Fe and Se will help in developing nutritionally improved wheat. Biofortification of wheat cultivars for micronutrients is a priority research area for wheat geneticists and breeders. It is known that during breeding of wheat cultivars for productivity and quality, a loss of grain micronutrient contents occurred, leading to decline in nutritional quality of wheat grain. Keeping this in view, major efforts have been made during the last two decades for achieving biofortification and bioavailability of wheat grain for micronutrients including Zn, Fe and Se. The studies conducted so far included evaluation of gene pools for contents of not only grain micronutrients as above, but also for phytic acid (PA) or phytate and phytase, so that, while breeding for the micronutrients, bioavailability is also improved. For this purpose, QTL interval mapping and GWAS were carried out to identify QTLs/genes and associated markers that were subsequently used for marker-assisted selection (MAS) during breeding for biofortification. Studies have also been conducted to understand the physiology and molecular basis of biofortification, which also allowed identification of genes for uptake, transport and storage of micronutrients. Transgenics using transgenes have also been produced. The breeding efforts led to the development of at least a dozen cultivars with improved contents of grain micronutrients, although land area occupied by these biofortified cultivars is still marginal. In this review, the available information on different aspects of biofortification and bioavailability of micronutrients including Zn, Fe and Se in wheat has been reviewed for the benefit of those, who plan to start work or already conducting research in this area.

Impact of nano-selenium on nuclear maturation and genes expression profile of buffalo oocytes matured in vitro

Supplementation of maturation media with antioxidant (bulk form) improves oocyte maturation. However, the influence of adding antioxidant (nano-particles) on oocyte maturation is not well known. We aimed to evaluate the effect of selenium nano-particles (SeNP) and bulk selenium (Se) on buffalo oocytes maturation, in terms nuclear maturation and molecular level. Oocytes were distributed into four groups; 1st group was control, 2nd group was supplied with Se (10 ng/ml), 3rd and 4th groups were supplied with 1 µg/ml SeNP (67 nm), and SeNP (40 nm), respectively. Matured oocytes were fixed and stained to determine nuclear maturation. Oocytes and COC after IVM were stored at - 80 °C, for RNA isolation and qRT-PCR for selected genes. The Se and seNP (40 nm) had a positive effect on oocytes nuclear maturation rates. Apoptosis-related cysteine peptidase (CASP3) was reduced in all supplemented groups. Anti-Mullerian hormone (AMH) was up-regulated in oocytes supplemented with SeNP (40 nm). In COC, AMH increased in group supplemented with SeNP (67 nm). In oocytes, phospholipase A2 group III (PLA2G3) decreased in all supplemented groups. While in COC, PLA2G3increased in group supplied with Se. In COC, luteinizing hormone/choriogonadotropin receptor (LHCGR) increased in groups supplied with Se or SeNP (40 nm).Glutathione peroxidase 4 (GPX4) increased in all supplemented groups, in oocytes and COC. In oocytes, superoxide dismutase (SOD) was up-regulated in supplemented groups {Se and SeNP (67 nm)}.The DNA methyltransferase (DNMT) in oocytes was reduced in supplemented groups. In oocytes, the POU class 5 homeobox 1 (OCT4) increased in all supplemented groups. In COC, the OCT4 was over-expressed in group supplemented with SeNP (40 nm). Selenium supplementation in bulk or nano-particle improved in vitro buffalo oocytes maturation, viaup-regulation of antioxidant defense and development competence genes. SeNP (smaller size, 40 nm) induced higher expression of antioxidant gene.

Improving the efficacy of selenium fertilizers for wheat biofortification

Increasing the selenium (Se) concentration of staple crops by fertilization is a valuable pathway to increase Se in the human diet, thus preventing Se deficiency. A pot trial was set up to investigate whether the application of 3.33 µg kg-1 of Se (equivalent to 10 g ha-1) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertilizer supplying nitrogen, phosphorus, potassium or sulfur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilizers. With grain Se concentrations varying from 0.13-0.84 mg kg-1, soil application of selenate-only was 2-15 times more effective than granular Se-enriched macronutrient fertilizers in raising grain Se concentrations. Co-application of foliar Se with an N carrier doubled the Se concentration in wheat grains compared to the application of foliar Se on its own, the majority of which was in the highly bioavailable selenomethionine fraction. Results from this study demonstrate the possibility of improving the efficacy of Se fertilizers, which could enrich crops with Se without additional application costs in the field.

Simultaneous Biofortification of Wheat with Zinc, Iodine, Selenium, and Iron through Foliar Treatment of a Micronutrient Cocktail in Six Countries

Field experiments were conducted on wheat to study the effects of foliar-applied iodine(I) alone, Zn (zinc) alone, and a micronutrient cocktail solution containing I, Zn, Se (selenium), and Fe (iron) on grain yield and grain concentrations of micronutrients. Plants were grown over 2 years in China, India, Mexico, Pakistan, South Africa, and Turkey. Grain-Zn was increased from 28.6 mg kg^-1 to 46.0 mg^-1 kg with Zn-spray and 47.1 mg^-1 kg with micronutrient cocktail spray. Foliar-applied I and micronutrient cocktail increased grain I from 24 μg kg^-1 to 361 μg kg^-1 and 249 μg kg^-1, respectively. Micronutrient cocktail also increased grain-Se from 90 μg kg^-1 to 338 μg kg^-1 in all countries. Average increase in grain-Fe by micronutrient cocktail solution was about 12%. The results obtained demonstrated that foliar application of a cocktail micronutrient solution represents an effective strategy to biofortify wheat simultaneously with Zn, I, Se and partly with Fe without yield trade-off in wheat.

Rice seed priming with sodium selenate: Effects on germination, seedling growth, and biochemical attributes

The aim of this study was to determine the effects of sodium selenate (15, 30, 45, 60, 75, 90, and 105 mg kg⁻¹) on the germination and seedling growth of Changnongjing 1 rice (Oryza sativa L.) at 25 °C and 30 °C. Low selenate concentrations induced shorter and more uniform germination periods than did ultrapure water at both temperatures. Seedlings primed with low selenate concentrations were superior to those primed with ultrapure water in terms of plant height, fresh weight, dry matter accumulation, and soluble carbohydrate and protein contents. Lower selenate concentrations (15–75 mg kg⁻¹) induced higher chlorophyll and phenol contents in seedlings than did ultrapure water. Lower selenate concentrations also increased the superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), and glutathione peroxidase (GPx) contents in seedlings and significantly decreased the stress-related malondialdehyde (MDA) content compared to ultrapure water. In conclusion, rice seedling germination and growth were promoted by priming with low selenate concentrations (15–75 mg kg⁻¹) but inhibited by priming with high selenate concentrations (90–105 mg kg⁻¹).

Genotypic Variation and Biofortification with Selenium in Brazilian Wheat Cultivars

Selenium is essential to human and animal health, as it regulates glutathione peroxidase activity. Although not considered essential to plants, it may be beneficial to plant growth and development at low concentrations. This study evaluated the effect of selenate application on Se biofortification, macro- and micronutrient content, and the expression of genes involved in Se uptake and assimilation in 12 Brazilian wheat ( L.) cultivars. This nutrient-solution experiment was performed in a greenhouse and consisted of a complete 12 × 2 factorial randomized design, with 12 wheat cultivars in the absence or presence of Se in solution (13 μmol), with three replicates. The presence of Se in solution did not affect growth and yield of wheat cultivars. Selenium content and accumulation in the grain varied significantly among the different cultivars. The presence of Se affected macronutrient content more than micronutrient content, and selenate application increased S content in the shoots of eight cultivars and in the grains of five cultivars. Examination of gene expression did not allow identification of responses within the two groups of cultivars-with high or low Se contents-after selenate application. Our findings are relevant to the design of Se biofortification strategies for wheat in tropical and subtropical agroecosystems.

The Level of Toxic Elements in Edible Crops from Seleniferous Area (Punjab, India)

The primary objective of the present study was to assess the level of selenium and toxic trace elements in wheat, rice, maize, and mustard from seleniferous areas of Punjab, India. The content of selenium (Se) and toxic trace elements, including aluminum (Al), arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), and tin (Sn), in crop samples was assessed using inductively coupled plasma mass-spectrometry after microwave digestion of the samples. The obtained data demonstrate that cultivation of crops on seleniferous soils significantly increased Se level in wheat, mustard, rice, and maize by a factor of more than 590, 111, 85, and 64, respectively. The study also showed that Se exposure affected toxic metal content in crops. In particular, Se-rich wheat was characterized by a significant decrease in Al, As, Ni, Pb, and Sn levels. The level of As, Cd, Ni, Pb, and Sn was significantly decreased in Se-rich rice, whereas As content was increased. In turn, the decrease in Al, As, Cd, Ni, Pb, and Sn levels in Se-rich maize was associated with a significant elevation of Hg content. Finally, Se-rich mustard was characterized by a significant increase in Al, As, and Hg levels, while the content of Ni, Pb, and Sn was significantly lower than the control levels. These findings should be taken into account while developing the nutritional strategies for correction of Se status. At the same time, the exact mechanisms underlying the observed differences are to be estimated.

Grain amino acid composition of barley (Hordeum vulgare L.) cultivars subjected to selenium doses

Background:

Selenium (Se34) is an essential micronutrient for humans and animals and has growth promoting and antioxidative effects at low concentrations.

Methods:

Effects of various sodium selenite (Na2SeO3) doses on grain amino acid content of barley cultivars (Bülbül 89 and Çetin 2000) was investigated using ion exchange liquid chromatography.

Results:

Majority of the amino acids could be altered with Selenium (Se) fertilization. Grain Se content of Bülbül 89 (0.175 mg kg−1) and Çetin 2000 (0.171 mg kg−1) were similar and both displayed an increase in proteinogenic, essential, and sulfur amino acids. The response of cultivars was more pronounced for Se accumulation and amino acid content at mid dose (12.5 mg ha−1). The quantities of proteinogenic, essential and sulfur amino acids increased considerably at that dose. Se induced increase in nitrogen content might cause an increase in some of the proteins of grain and consequently can alter amino acid composition. An obvious increase in the limiting amino acids (lysine and threonine) were prominent in response to Se fertilization.

Conclusion:

Se treatment influence amino acid composition of barley grains; especially improve the quantity of limiting amino acids and consequently nutritional value of the grain.

Selenium supplementation during in vitro maturation enhances meiosis and developmental capacity of yak oocytes

The objectives of the present study were to investigate the effects of selenium (Se) supplementation during in vitro maturation (IVM) on the developmental capacity of yak (Bos grunniens) oocytes. Nuclear maturation, DNA integrity, glutathione peroxidase (GSH-Px) activity, subsequent embryonic development, and gene expression after in vitro fertilization (IVF) were evaluated. The Se concentrations in yak plasma and follicular fluid were 0.142 and 0.069 μg/mL, respectively. The DNA damage in cumulus cells decreased significantly with 2 and 4 μg/mL supplementation of sodium selenite to IVM medium (P < 0.05). Total GSH-Px activity in oocytes increased in all Se supplementation groups, and the 2 and 4 μg/mL groups were significantly higher than the control group (0 μg/mL). However, the cleavage rate was not significantly different after Se supplementation (P > 0.05). The IVF blastocyst formation rates of 0, 1 and 4 μg/mL sodium selenite groups were 47.7%, 51.2% and 58.9%, respectively. The 2 μg/mL sodium selenite group had the highest blastocyst formation rate (60.5%). Gene expression analysis revealed that the quantity of transcripts associated with selenoprotein and protein synthesis were high in the 2 and 4 μg/mL groups. In conclusion, both GSH-Px activity of oocytes and DNA integrity of cumulus cells significantly increased with supplemental Se during oocyte IVM. Considering that embryonic development is responsive to Se supplementation, we inferred that appropriate Se concentrations during IVM were beneficial for yak oocyte maturation and subsequent development.

QTL mapping of selenium content using a RIL population in wheat

Selenium (Se) is an essential trace element that plays various roles in human health. Understanding the genetic control of Se content and quantitative trait loci (QTL) mapping provide a basis for Se biofortification of wheat to enhance grain Se content. In the present study, a set of recombinant inbred lines (RILs) derived from two Chinese winter wheat varieties (Tainong18 and Linmai6) was used to detect QTLs for Se content in hydroponic and field trials. In total, 16 QTLs for six Se content-related traits were detected on eight chromosomes, 1B, 2B, 4B, 5A, 5B, 5D, 6A, and 7D. Of these, seven QTLs were detected at the seedling stage and nine at the adult stage. The contribution of each QTL to Se content ranged from 7.37% to 20.22%. QSsece-7D.2, located between marker loci D-3033829 and D-1668160, had the highest contribution (20.22%). This study helps in understanding the genetic basis for Se contents and will provide a basis for gene mapping of Se content in wheat.

Selenium speciation in wheat grain varies in the presence of nitrogen and sulphur fertilisers

This study investigated whether selenium species in wheat grains could be altered by exposure to different combinations of nitrogen (N) and sulphur (S) fertilisers in an agronomic biofortification experiment. Four Australian wheat cultivars (Mace, Janz, Emu Rock and Magenta) were grown in a glasshouse experiment and exposed to 3 mg Se kg^-1 soil as selenate (Se^VI). Plants were also exposed to 60 mg N kg^-1 soil as urea and 20 mg S kg^-1 soil as gypsum in a factorial design (N + S + Se; N + Se; S + Se; Se only). Plants were grown to maturity with grain analysed for total Se concentrations via ICP-MS and Se species determined via HPLC-ICP-MS. Grain Se concentrations ranged from 22 to 70 µg Se g^-1 grain (dry mass). Selenomethionine (SeMet), Se-methylselenocystine (MeSeCys), selenohomolanthionine (SeHLan), plus a large concentration of uncharacterised Se species were found in the extracts from grains. SeMet was the major Se species identified accounting for between 9 and 24 µg Se g^-1 grain. Exposure to different N and S fertiliser combinations altered the SeMet content of Mace, Janz and Emu Rock grain, but not that of Magenta. MeSeCys and SeHLan were found in far lower concentrations (<4 µg Se g^-1 grain). A large component of the total grain Se was uncharacterisable (>30 % of total grain Se) in all samples. When N fertiliser was applied (with or without S), the proportion of uncharacterisable Se increased between 60 and 70 % of the total grain Se. The data presented here indicate that it is possible to alter the content of individual Se species in wheat grains via biofortification combined with manipulation of N and S fertiliser regimes. This has potential significance in alleviating or combating both Se deficiency and Se toxicity effects in humans.

Trace elements in native and improved paddy rice from different climatic regions of Sri Lanka: implications for public health

Background

Samples of 226 new improved and 21 indigenous rice (Oryza sativa L.) varieties were collected from the rice fields in three climatic zones of Sri Lanka and concentrations of 18 trace elements (Li, B, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Ba, Pb and Bi) were measured giving particular emphasis on Se, Cd and As using ICP-MS. The two way multivariate analysis of variance (MANOVA) method was employed to identify the differences in composition among rice from different climatic zones.

Results

The mean values obtained for both white and red rice were Se (36; 25 µg/kg), As (42; 45 µg/kg) and Cd (70; 123 µg/kg) on dry weight basis. However mean content of Se, As and Cd of native rice varieties were 69, 74 and 33 µg/kg, respectively. Statistical interpretations showed that in the majority of cases, there was a significant difference in Cd content among climatic zones whereas Se and Pb show differences between white and red rice varieties. Arsenic did not indicate any significant difference either between rice types or among climatic regions. Notably Se and As contents in indigenous rice were higher than that of improved rice types. To assess the safety of dietary of intake, daily intake of Se, Cd and As by rice were calculated. Non-gender specific Estimated Daily Intake (EDI) of Se, Cd and As consuming improved rice are 9.31, 24.1 and 12.2 µg day⁻¹, respectively.

Conclusions

Since over 50 % of daily meals of people contain rice or rice based products, Se intake is expected to be deficient among the Sri Lankan population.

Selenium promotes sulfur accumulation and plant growth in wheat (Triticum aestivum)

Selenium (Se) is an essential micronutrient for animals and humans and a target for biofortification in crops. Sulfur (S) is a crucial nutrient for plant growth. To gain better understanding of Se and S nutrition and interaction in plants, the effects of Se dosages and forms on plant growth as well as on S level in seven wheat lines were examined. Low dosages of both selenate and selenite supplements were found to enhance wheat shoot biomass and show no inhibitory effect on grain production. The stimulation on plant growth was correlated with increased APX antioxidant enzyme activity. Se forms were found to exert different effects on S metabolism in wheat plants. Selenate treatment promoted S accumulation, which was not observed with selenite supplement. An over threefold increase of S levels following selenate treatment at low dosages was observed in shoots of all wheat lines. Analysis of the sulfate transporter gene expression revealed an increased transcription of SULTR1;1, SULTR1;3 and SULTR4;1 in roots following 10 μM Na2 SeO4 treatment. Mass spectrometry-based targeted protein quantification confirmed the gene expression results and showed enhanced protein levels. The results suggest that Se treatment mimics S deficiency to activate specific sulfate transporter expression to stimulate S uptake, resulting in the selenate-induced S accumulation. This study supports that plant growth and nutrition benefit from low dosages of Se fertilization and provides information on the basis underlying Se-induced S accumulation in plants.

The case for pre-parturient selenium and iodine supplementation of ewes for improving lamb survival

Lamb survival is an issue of high relevance to the Australian sheep industry, as lamb-survival rates have direct bearing on overall reproductive performance of the sheep, and also constitute a main concern from an animal welfare perspective (Mellor and Stafford 2004). Both genetic and management factors play an important role in this complex issue (Hinch and Brien 2014). Ewe nutrition is of particular relevance as the intrauterine growth conditions prepare the lamb for the crucial transition to life outside the uterus. Effects of body condition of the ewe during various stages of the pregnancy have been investigated in detail, yet much less is known about the critical role of micronutrient provision to the ewe. Although several risk factors for selenium (Se) and iodine (I) subclinical deficiencies exist for sheep on pasture in Australia, determining micronutrient status in sheep or pasture is not straightforward. Several studies have separately found effects of Se and I supplementation on lamb survival. Studies investigating the interaction of Se and I supplementation have been few but results have demonstrated an interaction between Se and I. With increased twinning rates as a result of increased selection of numbers of lambs weaned, nutritional demands during pregnancy across flocks are increasing, and effects of micronutrients on lamb health and survival have greater impact. New opportunities in nutritional research are encouraging new studies into the effects of Se and I supplementation on lamb survival.

The role of selenium in human conception and pregnancy

Selenium (Se) is a trace element essential for the appropriate course of vital processes in the human body. It is also a constituent of the active center of glutathione peroxidase that protects cellular membranes against the adverse effects of H2O2 lipid peroxides. Epidemiological surveys have demonstrated that selenium deficiency in the body may contribute to an increased risk for certain neoplasmic diseases (including colonic carcinoma, gastric carcinoma, pulmonary carcinoma and prostate carcinoma), as well as diseases of the cardiovascular, osseous and nervous systems. Apart from its cancer prevention and antioxidative activities, selenium protects the body against detrimental effects of heavy metals and determines the proper functioning of the immunological system. Furthermore, selenium plays a significant role in the undisturbed functioning of the reproductive system. Many studies have addressed correlations between its intake and fertility as well as disorders of procreation processes. Selenium deficiencies may lead to gestational complications, miscarriages and the damaging of the nervous and immune systems of the fetus. A low concentration of selenium in blood serum in the early stage of pregnancy has been proved to be a predictor of low birth weight of a newborn. A deficiency of this element may also cause infertility in men by causing a deterioration in the quality of semen and in sperm motility. For this reason, supplementation in the case of selenium deficiencies in the procreation period of both women and men is of utmost significance.

Selenate-enriched urea granules are a highly effective fertilizer for selenium biofortification of paddy rice grain

This study examined the effects of applied selenium (Se) species, time of application, method of application, and soil water management regimen on the accumulation of Se in rice plants. Plants were grown to maturity in a temperature- and humidity-controlled growth chamber using three water management methods: field capacity (FC), submerged until harvest, and submerged and drained 2 weeks before harvest. Two Se species, selenate (SeO4(2-)) and selenite (SeO3(2-)), were applied at a rate equivalent to 30 g ha(-1). Four application methods were employed as follows: (i) Se applied at soil preparation, (ii) Se-enriched urea granules applied to floodwater at heading; (iii) foliar Se applied at heading; and (iv) fluid fertilizer Se applied to soil or floodwater at heading. Total Se concentrations in rice grains, husks, leaves, culms, and roots were measured, as well as Se speciation in grains from the Se-enriched urea granule treatment. Highest Se concentrations in the grain occurred with SeO4(2-) and with fertilizer applied at heading stage; SeO4(2-)-enriched urea granules applied at heading increased grain Se concentrations 5-6-fold (by 450-600 μg kg(-1)) compared to the control (no fertilizer Se applied) in all water treatments. Under paddy conditions other Se fertilization strategies were much less effective. Drainage before harvesting caused Se to accumulate in/on rice roots, possibly through adsorption onto iron plaque on roots. Rice grains contained Se mainly in the organic form as selenomethionine (SeM), which comprised >90% of the total grain Se in treatments fertilized with SeO4(2-)-enriched urea granules. The results of this study clearly show that of the fertilizer strategies tested biofortification of Se in rice grains can best be achieved in lowland rice by broadcast application of SeO4(2-)-enriched urea granules to floodwater at heading stage.

Natural variation in grain selenium concentration of wild barley, Hordeum spontaneum, populations from Israel

Wild barley (Hordeum spontaneum), the progenitor of cultivated barley, is an important genetic resource for cereal improvement. Selenium (Se) is an essential trace mineral for humans and animals with antioxidant, anticancer, antiarthropathy, and antiviral effects. In the current study, the grain Se concentration (GSeC) of 92 H. spontaneum genotypes collected from nine populations representing different habitats in Israel was investigated in the central area of Guizhou Province, China. Remarkable variations in GSeC were found between and within populations, ranging from 0 to 0.387 mg kg(-1) among the 92 genotypes with an average of 0.047 mg kg(-1). Genotype 20_C from the Sede Boqer population had the highest GSeC, while genotype 25_1 from the Atlit population had the lowest. The mean value of GSeC in each population varied from 0.010 to 0.105 mg kg(-1). The coefficient of variation for each population ranged from 12% to 163%. Significant correlations were found between GSeC and 12 ecogeographical factors out of 14 studied. Habitat soil type also significantly affected GSeC. The wild barley exhibited wider GSeC ranges and greater diversity than its cultivated counterparts. The higher Se grain concentrations found in H. spontaneum populations suggest that wild barley germplasm confer higher abilities for Se uptake and accumulation, which can be used for genetic studies of barley nutritional value and for further improvement of domesticated cereals.

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 concentration and speciation in biofortified flour and bread: Retention of selenium during grain biofortification, processing and production of Se-enriched food

The retention and speciation of selenium in flour and bread was determined following experimental applications of selenium fertilisers to a high-yielding UK wheat crop. Flour and bread were produced using standard commercial practices. Total selenium was measured using inductively coupled plasma-mass spectrometry (ICP-MS) and the profile of selenium species in the flour and bread were determined using high performance liquid chromatography (HPLC) ICP-MS. The selenium concentration of flour ranged from 30ng/g in white flour and 35ng/g in wholemeal flour from untreated plots up to >1800ng/g in white and >2200ng/g in wholemeal flour processed from grain treated with selenium (as selenate) at the highest application rate of 100g/ha. The relationship between the amount of selenium applied to the crop and the amount of selenium in flour and bread was approximately linear, indicating minimal loss of Se during grain processing and bread production. On average, application of selenium at 10g/ha increased total selenium in white and wholemeal bread by 155 and 185ng/g, respectively, equivalent to 6.4 and 7.1μg selenium per average slice of white and wholemeal bread, respectively. Selenomethionine accounted for 65-87% of total extractable selenium species in Se-enriched flour and bread; selenocysteine, Se-methylselenocysteine selenite and selenate were also detected. Controlled agronomic biofortification of wheat crops for flour and bread production could provide an appropriate strategy to increase the intake of bioavailable selenium.

Arsenic influence on genetic variation in grain trace-element nutrient content in Bengal delta grown rice

It has previously been shown that across different arsenic (As) soil environments, a decrease in grain selenium (Se), zinc (Zn), and nickel (Ni) concentrations is associated with an increase in grain As. In this study we aim to determine if there is a genetic element for this observation or if it is driven by the soil As environment. To determine the genetic and environmental effect on grain element composition, multielement analysis using ICP-MS was performed on rice grain from a range of rice cultivars grown in 4 different field sites (2 in Bangladesh and 2 in West Bengal). At all four sites a negative correlation was observed between grain As and grain Ni, while at three of the four sites a negative correlation was observed between grain As and grain Se and grain copper (Cu). For manganese, Ni, Cu, and Se there was also a significant genetic interaction with grain arsenic indicating some cultivars are more strongly affected by arsenic than others.

Critical evaluation of strategies for mineral fortification of staple food crops

Staple food crops, in particular cereal grains, are poor sources of key mineral nutrients. As a result, the world's poorest people, generally those subsisting on a monotonous cereal diet, are also those most vulnerable to mineral deficiency diseases. Various strategies have been proposed to deal with micronutrient deficiencies including the provision of mineral supplements, the fortification of processed food, the biofortification of crop plants at source with mineral-rich fertilizers and the implementation of breeding programs and genetic engineering approaches to generate mineral-rich varieties of staple crops. This review provides a critical comparison of the strategies that have been developed to address deficiencies in five key mineral nutrients-iodine, iron, zinc, calcium and selenium-and discusses the most recent advances in genetic engineering to increase mineral levels and bioavailability in our most important staple food crops.

Increased consumption of wheat biofortified with selenium does not modify biomarkers of cancer risk, oxidative stress, or immune function in healthy Australian males

Increased intake of selenium (Se) may reduce the risk of degenerative diseases including cancer but excessive intake may be toxic. Wheat is a major source of dietary Se in humans. However, the effect of Se from wheat that is agronomically biofortified with Se on biomarkers of human health status is unknown. This study aimed to investigate whether improving Se status, by increased dietary intake of Se-biofortified wheat, affects biomarkers of cancer risk, cardiovascular disease risk, oxidative stress, and immune function in healthy South Australian men. A 24-week placebo-controlled double-blind intervention was performed in healthy older men (n = 62), with increased dose of Se intake every 8 weeks. Wheat was provided as 1, 2, and 3 puffed wheat biscuits, during weeks 1-8, 9-16, and 17-24, respectively. Blood was collected to measure a wide range of disease risk biomarkers. Consumption of Se-biofortified wheat was found to increase plasma Se concentration from a baseline level of 122 to 192 microg/L following intake of three biscuits/day, which provided 267 microg Se. Platelet glutathione peroxidase, chromosome aberrations, and DNA damage in lymphocytes measured using the cytokinesis-block micronucleus cytome assay and with the Comet assay, plasma F2-isoprostanes, protein carbonyls, plasma C-reactive protein, and leukocyte number were unaffected by the improved Se status. Improvement of Se status by consumption of Se-biofortified wheat did not substantially modify the selected biomarkers of degenerative disease risk and health status in this apparently selenium-replete cohort of healthy older men in South Australia.

Biofortification of crops with seven mineral elements often lacking in human diets--iron, zinc, copper, calcium, magnesium, selenium and iodine

The diets of over two-thirds of the world's population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification). This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se). Two complementary approaches have been successfully adopted to increase the concentrations of bioavailable mineral elements in food crops. First, agronomic approaches optimizing the application of mineral fertilizers and/or improving the solubilization and mobilization of mineral elements in the soil have been implemented. Secondly, crops have been developed with: increased abilities to acquire mineral elements and accumulate them in edible tissues; increased concentrations of 'promoter' substances, such as ascorbate, beta-carotene and cysteine-rich polypeptides which stimulate the absorption of essential mineral elements by the gut; and reduced concentrations of 'antinutrients', such as oxalate, polyphenolics or phytate, which interfere with their absorption. These approaches are addressing mineral malnutrition in humans globally.

Serum levels of antioxidants (Zn, Cu, Se) in healthy volunteers living in Tehran

Zinc (Zn), copper (Cu), and selenium (Se) are well-known as essential trace elements. These elements attract a great interest, not only in the scientific world, but also in the public option. The aim of this study was to evaluate the serum Zn, Cu, and Se levels in healthy volunteers (60 females and 55 males) living in Tehran. The age (6-62 years) and sex of the subjects, as well as drug and tobacco consumption, were registered. The concentrations of these elements were determined by atomic absorption spectrometry. The serum levels of Zn, Cu, and Se in the normal population of Tehran was 0.89 +/- 0.16 mg/L, 0.95 +/- 0.20 mg/L, and 99.10 +/- 21.78 microg/L, respectively. There was no significant gender-related difference in serum Zn concentration (p < 0.15). However, a significant difference (p < 0.05) in both Cu and Se levels was observed between males and females.

Regulation of the insulin antagonistic protein tyrosine phosphatase 1B by dietary Se studied in growing rats

Protein tyrosine phosphatase 1B (PTP1B) is a key enzyme in the counterregulation of insulin signaling, and its physiological modulation depends on H2O2 and glutathione (GSH). Se via GSH peroxidases (GPxs) and its specific metabolism is involved in the removal of H2O2 and in the regulation of GSH metabolism. Recent results from animal trials and epidemiological studies with humans have shown that a high GPx1 activity or a permanent surplus of Se may promote the development of obesity and diabetes. Our nutrition physiological study with 7 x 7 growing rats was carried out to examine if PTP1B is modulated by Se supplements and, thus, may represent one trigger mediating these undesirable metabolic effects of Se. One group of rats was fed an Se-deficient diet for 8 weeks. The diets of the other six groups contained Se as selenite or selenate according to the recommendations (0.20 mg/kg diet) and at two supranutritional levels (1.00 and 2.00 mg/kg diet). All Se-supplemented animals featured a significantly higher body weight (6-14%) compared to their Se-deficient companions. Expression and activity of GPx1 in the liver of Se supplemented animals was 10- and 70-fold higher compared to Se deficiency. The detailed study of PTP1B regulation using an enzymatic assay and Western Blot analysis with an antibody against protein glutathionylation revealed that PTP1B was significantly up-regulated by both a maximization of GPx1 activity and by increasing dietary Se supply, reducing its inhibition via glutathionylation. Selenate effected a stronger PTP activation compared to selenite. In conclusion, our results suggest that the modulation of PTP1B activity may represent one plausible mechanism by which a long-term intake of Se supplements exceeding the requirements can promote the development of obesity and diabetes and needs further intensive investigation.

Selenium speciation and bioavailability in biofortified products using species-unspecific isotope dilution and reverse phase ion pairing-inductively coupled plasma-mass spectrometry

In some regions of the world, where the bioavailability of selenium (Se) in soil is low and/or declining (e.g., due to use of high-sulfur fertilizers), there is increased risk of adverse affects on animals and human health. In recent years, increased research attention has focused on understanding the relationships between Se contents in foods and supplements and their nutritional benefits for animal and humans. The objective of this study was to use a species-unspecific isotope dilution and reverse phase ion pairing-inductively coupled plasma-mass spectrometry techniques for the identification and quantification of Se species in biofortified grains (i.e., wheat and triticale), flour, and wheat biscuits. The information on Se species was used to gain an understanding of the bioavailability of Se in biofortified and process-fortified wheat biscuits used in a clinical trail. The major Se species identified in biofortified and process-fortified samples were selenomethionine (76-85%) and selenomethionine selenoxide (51-60%), respectively. Total plasma Se concentrations in the biofortified Se exposure group were found to increase throughout the 6 month trial period (mean=122 microg L(-1) at 0 months to 194 microg L(-1) at 6 months). In contrast, the trial group exposed to process-fortified Se biscuits showed little increase in mean total Se plasma concentrations until 4 months of exposure (mean=122 microg L(-1) at 0 months to 140 microg L(-1) at 4 months) that remained constant until the end of the trial period (mean=140 microg L(-1) at 4 months to 138 microg L(-1) at 6 months). The difference in total Se plasma concentrations may be due to the presence and bioavailability of different Se species in biofortified and process-fortified biscuits. An understanding of Se speciation in foods enables better understanding of pathways and their potential benefits for animals and humans.

Selenium: its role as antioxidant in human health

Selenium (Se) is an essential trace element, and its low status in humans has been linked to increased risk of various diseases, such as cancer and heart disease. In recent years, Se research has attracted tremendous interest because of its important role in antioxidant selenoproteins for protection against oxidative stress initiated by excess reactive oxygen species (ROS) and reactive nitrogen species (NOS). The synthesis of selenoproteins requires a unique incorporation of amino acid selenocysteine (Sec) into proteins directed by the UGA codon, which is also a termination codon. Interest in Se research has led to the discovery of at least 30 selenoproteins; however, the biochemical functional roles of some of these selenoproteins are still unknown. Besides in the form of selenoproteins, Se can exist in many different chemical forms in biological materials either as organic Se compounds, such as selenomethionine and dimethylselenide, and inorganic selenites and selenates. In foods, Se is predominantly present as selenomethionine, which is an important source of dietary Se in humans, and also as a chemical form that is commonly used for Se supplements in clinical trials. Concern for potential deficiency diseases associated with low Se status has led to the establishment of the recommended daily requirements for Se in many countries. However, excess Se intakes through supplementation and its potential misuse as health therapy could also pose a risk of adverse health effects if its use is not properly regulated.

Selenium interactions with essential and toxic elements in egg yolk from commercial and fortified eggs

The main objective of this work was to evaluate the interaction between selenium concentration in both commercial and Se-enriched eggs and other essential/toxic elements (Ca, Mg, Fe, Zn, Pb, and Cd), taking into account a possible synergic action of iodine. Commercial eggs were purchased from several sale points or directly from the producers (farmyard eggs). Fortified eggs were obtained by supplementing chickenfeed for 6 weeks with Se as sodium selenite (1.0 microg/g Se) or Se plus iodine (1.0 microg/g Se+3.7 microg/g I). Se in experimental egg yolks significantly increased over the basic value by 39% in the Se group and 61% in the Se+I group, suggesting that I addition may enhance Se absorption. Levels of Se in commercial yolks were identical in free-range, barn or battery eggs, but significantly lower in farmyard and higher in organic eggs where the Se content approximated that found in Se fortified eggs. A significant reduction in Cd was observed in Se+I treated yolks compared to both control and Se alone diet, thus suggesting a high sensitivity of Cd to the detoxifying effect of Se combined with I. Furthermore, Se+I supplementation was associated with a significant Zn reduction, a finding which needs clarification to avoid attempts to maximize one component affecting the levels of other essential elements.

Increased plasma selenium levels correlate with elevated resistance of Heliothis virescens larvae against baculovirus infection

We reported that dietary selenium (Se) impacted the growth and development of Trichoplusia ni reared for many generations on diet containing extremely low levels of Se. Larvae had an elevated resistance to per os infection with a baculovirus. In this study, we examine how dietary Se (in the form of selenite) affects the growth, development, and Se content of Heliothis virescens that have been laboratory reared for less than two years. Larvae fed a commercial tobacco budworm diet supplemented with greater than 20 ppm Se grew at a slower rate than insects fed lower levels of Se and had an increase in the amount of Se sequestered in pupae. Larvae fed diets containing from 10-60 ppm Se exhibited elevated plasma concentrations of the micronutrient and increased plasma virucidal activity against Helicoverpa zea single nucleopolyhedrovirus (HzSNPV). Larvae reared on diet supplemented with 10 or 60 ppm Se until the onset of the penultimate instar were then infected per os or by injection with increasing concentrations of the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV). Larvae fed dietary Se and infected with occluded virus per os displayed a significantly lower mortality compared with infected larvae not fed Se. Our results suggest that dietary Se levels are directly correlated with plasma Se levels, and that plasma Se levels are in turn correlated with baculovirus resistance.