Loss of selenoprotein W in murine macrophages alters the hierarchy of selenoprotein expression, redox tone, and mitochondrial functions during inflammation.

Macrophages play a pivotal role in mediating inflammation and subsequent resolution of inflammation. The availability of selenium as a micronutrient and the subsequent biosynthesis of selenoproteins, containing the 21st amino acid selenocysteine (Sec), are important for the physiological functions of macrophages. Selenoproteins regulate the redox tone in macrophages during inflammation, the early onset of which involves oxidative burst of reactive oxygen and nitrogen species. SELENOW is a highly expressed selenoprotein in bone marrow-derived macrophages (BMDMs). Beyond its described general role as a thiol and peroxide reductase and as an interacting partner for 14-3-3 proteins, its cellular functions, particularly in macrophages, remain largely unknown. In this study, we utilized Selenow knock-out (KO) murine bone marrow-derived macrophages (BMDMs) to address the role of SELENOW in inflammation following stimulation with bacterial endotoxin lipopolysaccharide (LPS). RNAseq-based temporal analyses of expression of selenoproteins and the Sec incorporation machinery genes suggested no major differences in the selenium utilization pathway in the Selenow KO BMDMs compared to their wild-type counterparts. However, selective enrichment of oxidative stress-related selenoproteins and increased ROS in Selenow-/- BMDMs indicated anomalies in redox homeostasis associated with hierarchical expression of selenoproteins. Selenow-/- BMDMs also exhibited reduced expression of arginase-1, a key enzyme associated with anti-inflammatory (M2) phenotype necessary to resolve inflammation, along with a significant decrease in efferocytosis of neutrophils that triggers pathways of resolution. Parallel targeted metabolomics analysis also confirmed an impairment in arginine metabolism in Selenow-/- BMDMs. Furthermore, Selenow-/- BMDMs lacked the ability to enhance characteristic glycolytic metabolism during inflammation. Instead, these macrophages atypically relied on oxidative phosphorylation for energy production when glucose was used as an energy source. These findings suggest that SELENOW expression in macrophages may have important implications on cellular redox processes and bioenergetics during inflammation and its resolution.

Molecular characterization and expression analysis of selenoprotein W gene in rainbow trout (Oncorhynchus mykiss) with dietary selenium levels.

Selenium (Se) plays an essential role in the growth of fish and performs its physiological functions mainly through incorporation into selenoproteins. Our previous studies suggested that the selenoprotein W gene (selenow) is sensitive to changes in dietary Se in rainbow trout. However, the molecular characterization and tissue expression pattern of selenow are still unknown. Here, we revealed the molecular characterization, the tissue expression pattern of rainbow trout selenow and analyzed its response to dietary Se. The open reading frame (ORF) of the selenow gene was composed of 393 base pairs (bp) and encodes a 130-amino-acid protein. The 3' untranslated region (UTR) was 372 bp with a selenocysteine insertion sequence (SECIS) element. Remarkably, the rainbow trout selenow gene sequence was longer than those reported for mammals and most other fish. A ß1-α1-ß2-ß3-ß4-α2 pattern made up the secondary structure of SELENOW. Furthermore, multiple sequence alignment revealed that rainbow trout SELENOW showed a high level of identity with SELENOW from Salmo salar. In addition, the selenow gene was ubiquitously distributed in 13 tissues with various abundances and was predominantly expressed in muscle and brain. Interestingly, dietary Se significantly increased selenow mRNA expression in muscle. Our results highlight the vital role of selenow in rainbow trout muscle response to dietary Se levels and provide a theoretical basis for studies of selenow.

Selenoprotein W as a molecular target of d-amino acid oxidase is regulated by d-amino acid in chicken neurons.

Selenoprotein W (SelW) is an important member of the avian selenoprotein family. It is well known for its important role in protecting neurons from oxidative stress during neuronal development. d-Amino acid (d-serine), as a neurotransmitter in the central nervous system (CNS), can mediate neurotoxicity. d-Amino acid oxidase (DAAO) is responsible for regulating the d-serine levels in cells. However, the correlation between SelW and DAAO is not clear yet. To investigate the regulations between SelW and DAAO, chicken embryo monolayer neurons were treated with d-serine and/or Se. In this study, we predicted molecular binding between SelW and DAAO. These results showed that the 9-16, 18, 41-47 and 66 residues of SelW could combine with the DAAO, which suggested that chicken SelW might be the target of DAAO. We determined the DAAO activity and the mRNA expression of SelW in in vitro cultured chicken embryo primitive neuron cells. d-Serine influenced the activity of DAAO and, moreover, a significant increase in the mRNA expression of SelW was found in neurons treated with Se. Notably, we also observed changes in the expression of SelW and DAAO when neurons were treated with various concentrations of d-serine and Se. In conclusion, these data suggest that d-serine could regulate the mRNA expression of SelW by interfering with the activity of DAAO in chicken embryo neurons.

Selenoproteins regulate stress erythroid progenitors and spleen microenvironment during stress erythropoiesis.

Micronutrient selenium (Se) plays a key role in redox regulation through its incorporation into selenoproteins as the 21st amino acid selenocysteine (Sec). Because Se deficiency appears to be a cofactor in the anemia associated with chronic inflammatory diseases, we reasoned that selenoproteins may contribute to erythropoietic recovery from anemia, referred to as stress erythropoiesis. Here, we report that loss of selenoproteins through Se deficiency or by mutation of the Sec tRNA (tRNA[Sec]) gene (Trsp) severely impairs stress erythropoiesis at 2 stages. Early stress erythroid progenitors failed to expand and properly differentiate into burst-forming unit-erythroid cells , whereas late-stage erythroid progenitors exhibited a maturation defect that affected the transition of proerythroblasts to basophilic erythroblasts. These defects were, in part, a result of the loss of selenoprotein W (SelenoW), whose expression was reduced at both transcript and protein levels in Se-deficient erythroblasts. Mutation of SelenoW in the bone marrow cells significantly decreased the expansion of stress burst-forming unit-erythroid cell colonies, which recapitulated the phenotypes induced by Se deficiency or mutation of Trsp Similarly, mutation of SelenoW in murine erythroblast (G1E) cell line led to defects in terminal differentiation. In addition to the erythroid defects, the spleens of Se-deficient mice contained fewer red pulp macrophages and exhibited impaired development of erythroblastic island macrophages, which make up the niche supporting erythroblast development. Taken together, these data reveal a critical role of selenoproteins in the expansion and development of stress erythroid progenitors, as well as the erythroid niche during acute anemia recovery.

Selenomethionine Alleviates AFB1-Induced Damage in Primary Chicken Hepatocytes by Inhibiting CYP450 1A5 Expression via Upregulated SelW Expression.

This study aims to evaluate the protective effects of selenomethionine (SeMet) on aflatoxin B1 (AFB1)-induced hepatotoxicity in primary chicken hepatocytes. Cell viability and lactic dehydrogenase activity assays revealed the dose dependence of AFB1 toxicity to chicken hepatocytes. AFB1 concentrations of >0.05 µg/mL significantly reduced glutathione and total superoxide dismutase levels and increased the malondialdehyde concentration and cytochrome P450 enzyme 1A5 (CYP450 1A5) mRNA levels (P < 0.05). AFB1, however, did not affect CYP450 3A37 mRNA levels. Supplementation with 2 µM SeMet protected against AFB1-induced changes and significantly increased selenoprotein W (SelW) mRNA levels (P < 0.05). Additionally, SelW knockdown attenuated the protective effect of SeMet on AFB1-induced damage and significantly increased the level of CYP450 1A5 expression (P < 0.05). Therefore, SeMet alleviates AFB1-induced damage in primary chicken hepatocytes by improving SelW expression, thus inhibiting CYP450 1A5 expression.

Identification, characterization of selenoprotein W and its mRNA expression patterns in response to somatostatin 14, cysteamine hydrochloride, 17ß-estradiol and a binary mixture of 17ß-estradiol and cysteamine hydrochloride in topmouth culter (Erythroculter ilishaeformis).

In this study, a selenoprotein W cDNA was cloned from topmouth culter (Erythroculter ilishaeformis), and it was designated as EISelW. The EISelW open reading frame was composed of 261 base pairs (bp), encoding 86-amino-acid protein. The 5' untranslated region (UTR) consisted of 104 bp, and the 3'-UTR was composed of 365 bp. A selenocysteine insertion sequence (SECIS) element was found in the 3'-UTR of EISelW mRNA. The SECIS element was classified as form II because of a small additional apical loop presented in SECIS element of EISelW mRNA. Bioinformatic approaches showed that the secondary structure of EISelW was a ß1-α1-ß2-ß3-ß4-α2 pattern from amino-terminal to carboxy-terminal. Real-time PCR analysis of EISelW mRNAs expression in 17 tissues showed that the EISelW mRNA was predominantly expressed in liver, ovary, pituitary, various regions of the brain, spinal cord and head kidney. Study of intraperitoneal injection showed that the levels of EISelW mRNA in brain, liver, ovary and spleen were regulated by somatostatin 14 (SS14), 17ß-estradiol (E2), cysteamine hydrochloride (CSH) and a binary mixture of E2 and CSH, dependent on the dosage. These results suggest that E2, SS14 and CSH status may affect tissues of selenium metabolism by regulating the expression of SelW mRNA, as SelW plays a central role in selenium metabolism.

Selenoprotein W as biomarker for the efficacy of selenium compounds to act as source for selenoprotein biosynthesis.

Selenium is an essential trace element and, like all elements, present in many different compounds with unequivocal functions. This fact is only sporadically mentioned when recommended intake or supplementation is indicated just as "selenium." In mammals, selenium is an integral part of selenoproteins as selenocysteine. Selenocysteine is formed from serine at the respective tRNA((ser)sec), a reaction that requires selenophosphate formed from selenide and ATP. Thus, only compounds that can be metabolized into selenide can serve as sources for selenoprotein biosynthesis. We therefore tested the ability of selenium compounds such as sodium selenite, methylseleninic acid (MeSeA), Se-methyl selenocysteine, and selenomethionine to increase the activity, protein, or mRNA levels of commonly used biomarkers of the selenium status, glutathione peroxidase-1 (GPx1) and thioredoxin reductase, and of putatively new biomarkers, selenoprotein W1 (SepW1), selenoprotein H, and selenoprotein 15 in three different cell lines. Selenite and MeSeA were most efficient in increasing all markers tested, whereas the other compounds had only marginal effects. Effects were higher in the noncancerous young adult mouse colon cells than in the cancer cell lines HepG2 and HT-29. At the protein level, SepW1 responded as well as GPx1 and at the mRNA level, even better. Thus, the outcome of selenium treatment strongly depends on the chemical form, the cell type, and the biomarker used for testing efficacy.

Possible correlation between selenoprotein W and myogenic regulatory factors in chicken embryonic myoblasts.

The biological function of selenium (Se) is mainly elicited through Se-containing proteins. Selenoprotein W (SelW), one member of the selenoprotein family, is essential for the normal function of the skeletal muscle system. To investigate the possible relationship of Se in the process of differentiation in chicken myoblasts and the expression of SelW, the cultured chicken embryonic myoblasts were incubated with sodium selenite at different concentrations for 72 h, and then the mRNA levels of SelW and myogenic regulatory factors (MRFs) in myoblasts were determined at 12, 24, 48, and 72 h, respectively. Furthermore, the correlation between SelW mRNA expression and MRF mRNA expression was assessed. The results showed that the sodium selenite medium enhanced the mRNA expression of SelW, Myf-5, MRF4, and myogenin in chicken myoblasts. The mRNA expression levels of MRFs were significantly correlated with those of SelW at 24, 48, and 72 h. These data demonstrate that Se is involved in the differentiation of chicken embryonic myoblasts, and SelW showed correlation with MRFs.

Effects of Selenoprotein W gene expression by selenium involves regulation of mRNA stability in chicken embryos neurons.

Selenium (Se) and Selenoprotein W (SelW) plays a pivotal role in the brain development, function, and degeneration and that SelW expression in the brain may be affected by Se. However, the mechanism which Se regulates the SelW gene expression in neurons remains to be unclear. To investigate the effects of the SelW gene expression and mRNA stability induced by Se, primary cultured chicken embryos neurons derived from 8-day-old chick embryo cerebral hemispheres were treated with 10(-9)-10(-5) mol/l Se as selenite for 3, 6, 12, 24 or 48 h, respectively. The morphology and viability of Neurons was detected. The SelW mRNA expression level and mRNA half-life was examined in Se-treated neurons. The relative low concentrations of Se enhanced the neurite outgrowth, increased the SelW mRNA levels and elevated the mRNA half-life of chick embryo neurons. In contrast, the high concentrations of Se presented neurotoxic to neurons, decreased the SelW mRNA levels and reduced the mRNA half-life of neuronal cells. These results suggest that the alteration of post-transcriptional stabilization of SelW mRNA is an important mechanism of Se-induced the elevation or reduction of the SelW expression level in chick embryo neurons.

Selenium regulates gene expression of selenoprotein W in chicken skeletal muscle system.

Selenoprotein W (SelW) is abundantly expressed in skeletal muscles of mammals and necessary for the metabolism of skeletal muscles. However, its expression pattern in skeletal muscle system of birds is still uncovered. Herein, to investigate the distribution of SelW mRNA in chicken skeletal muscle system and its response to different selenium (Se) status, 1-day-old chickens were exposed to various concentrations of Se as sodium selenite in the feed for 35 days. In addition, myoblasts were treated with different concentrations of Se in the medium for 72 h. Then the levels of SelW mRNA in skeletal muscles (wing muscle, pectoral muscle, thigh muscle) and myoblasts were determined on days 1, 15, 25, and 35 and at 0, 24, 48, and 72 h, respectively. The results showed that SelW was detected in all these muscle components and it increased both along with the growth of organism and the differentiation process of myoblasts. The thigh muscle is more responsive to Se intake than the other two skeletal muscle tissues while the optimal Se supplementation for SelW mRNA expression in chicken myoblasts was 10(-7) M. In summary, Se plays important roles in the development of chicken skeletal muscles. To effect optimal SelW gene expression, Se must be provided in the diet and the media in adequate amounts and neither at excessive nor deficient levels.

Selenoprotein W depletion induces a p53- and p21-dependent delay in cell cycle progression in RWPE-1 prostate epithelial cells.

The anticancer activity of selenium (Se) has been demonstrated in myriad animal and in vitro studies, yet the mechanisms remain obscure. The main form of Se in animal tissues is selenocysteine in selenoproteins, but the relative importance of selenoproteins versus smaller Se compounds in cancer protection is unresolved. Selenoprotein W (SEPW1) is a highly conserved protein ubiquitously expressed in animals, bacteria, and archaea. SEPW1 depletion causes a delay in cell cycle progression at the G1/S transition of the cell cycle in breast and prostate epithelial cells. Tumor suppressor protein p53 is a master regulator of cell cycle progression and is the most frequently mutated gene in human cancers. p53 was increased in SEPW1 silenced cells and was inversely correlated with SEPW1 mRNA in cell lines with altered SEPW1 expression. Silencing SEPW1 decreased ubiquitination of p53 and increased p53 half-life. SEPW1 silencing increased p21(Cip1/WAF1/CDKN1A), while p27 (Kip1/CDKN1B) levels were unaffected. G1-phase arrest from SEPW1 knockdown was abolished by silencing p53 or p21. Cell cycle arrest from SEPW1 silencing was not associated with activation of ATM or phosphorylation of Ser-15 in p53, suggesting the DNA damage response pathway was not involved. Silencing GPX1 had no effect on cell cycle, suggesting that G1-phase arrest from SEPW1 silencing was not due to loss of antioxidant protection. More research is required to identify the function of SEPW1 and how it affects stability of p53.

Dietary selenium regulation of transcript abundance of selenoprotein N and selenoprotein W in chicken muscle tissues.

Selenium (Se), selenoprotein N (SelN) and selenoprotein W (SelW) play a crucial role in muscle disorders. Se status highly regulates selenoprotein mRNA levels. However, few attempts have been performed on the effect of dietary Se supplementation on muscle SelN and SelW mRNA levels in birds. To investigate the effects of Se on the regulation of SelN and SelW mRNA levels in muscle tissues, one-day-old male chickens were fed either a commercial diet or a Se-supplemented diet containing 1.0, 2.0, 3.0 or 5.0 mg/kg sodium selenite for 90 days. Muscle tissues (breast, flight, thigh, shank and cardiac muscles) were collected and examined for Se content and mRNA levels of SelN and SelW. Moreover, Selenophosphate synthetase-1 (SPS-1) and selenocysteine-synthase (SecS) mRNA levels were analyzed. Significant increases in SelN mRNA levels were obtained in breast, thigh and shank muscles treated with Se, with maximal effects at 3.0 mg Se/kg diet, but 2.0 mg Se/kg diet resulted in peak levels of Sel N mRNA in flight muscles. Changes in SelW mRNA abundance in thigh and shank muscles increased in response to Se supply. After reaching a maximal level, higher Se supplementation led to a reduction in both SelN and SelW mRNAs. However, SelN and SelW mRNA levels displayed a different expression pattern in different skeletal and cardiac muscles. Thus, it suggested that skeletal and cardiac muscles SelN and SelW mRNA levels were highly regulated by Se supplementation and different muscle tissues showed differential sensitivity. Moreover, Se supplementation also regulated the levels of SPS1 and SecS mRNAs. The mRNA levels of SPS1 and SecS were enhanced in the Se supplemented groups. These data indicate that Se regulates the expression of SelN and SelW gene and affect the mRNA levels of SecS and SPS1.

Marginal selenium deficiency down-regulates inflammation-related genes in splenic leukocytes of the mouse.

Moderate selenium deficiency may lead to an impaired capacity to cope with health challenges. Functional effects of suboptimal selenium intake are not fully known, and biomarkers for an insufficient selenium supply are inadequate. We therefore fed mice diets of moderately deficient or adequate selenium intake for 6 weeks. Changes in global gene expression were monitored by microarray analysis in splenic leukocytes. Genes for four selenoproteins, Sepw1, Gpx1, Selh and Sep15, were the most significantly down-regulated in moderate selenium deficiency, and this was confirmed by quantitative polymerase chain reaction (qPCR). Classification of significantly affected genes revealed that processes related to inflammation, heme biosynthesis, DNA replication and transcription, cell cycle and transport were affected by selenium restriction. Down-regulation by moderate selenium deficiency of specific genes involved in inflammation and heme biosynthesis was confirmed by qPCR. Myeloperoxidase and lysozyme activities were decreased in selenium-restricted leukocytes, providing evidence for functional consequences. Genes for 31 nuclear factor (NF)-κB targets were down-regulated in moderate selenium deficiency, indicating an impaired NF-κB signaling. Together, the observed changes point to a disturbance in inflammatory response. The selenoproteins found here to be sensitive to selenium intake in murine leukocytes might also be useful as biomarkers for a moderate selenium deficiency in humans.

Delayed cell cycle progression from SEPW1 depletion is p53- and p21-dependent in MCF-7 breast cancer cells.

Selenium (Se) is an essential redox-active trace element with close connections to cancer. Most of Se's biological functions have been attributed to the antioxidant properties of Se-containing proteins. However, the relative contribution of selenoproteins and small Se compounds in cancer protection is still a matter of debate. The tumor suppressor p53 is the most frequently mutated gene in human cancer and is often referred to as the "guardian of the genome". In response to genomic stresses, p53 causes cell cycle arrest to allow time for genomic damage to be repaired before cell division or induces apoptosis to eliminate irreparably damaged cells. Selenoprotein W (SEPW1) is a highly conserved small thioredoxin-like protein required for cell cycle progression. The present work shows that SEPW1 facilitates the G1 to S-phase transition by down-regulating expression of the cyclin-dependent kinase inhibitor p21. SEPW1 controls p21 by modulating levels of the p53 transcription factor, and this is associated with changes in phosphorylation of Ser-33 in p53. More work is needed to identify the mechanism by which SEPW1 regulates phosphorylation of Ser-33 and the kinase or phosphatase enzymes involved.

Dietary selenium influences pancreatic tissue levels of selenoprotein W in chickens.

Selenium (Se) influences the levels of selenoprotein W (SelW) in mammals. However, little is known about the pattern of SelW expression in the pancreatic tissue of birds. To investigate the effects of dietary Se levels on the expression of SelW mRNA in the pancreatic tissue of birds, one-day-old chickens were randomly allocated to three groups. The L group was fed a basal diet deficient in Se (containing 0.033mg/kg Se); the M and H groups were fed Se-supplemented diets with either 0.15 or 1.5mg/kg Se, respectively (as sodium selenite) for 55days. The pancreatic tissue was collected and examined for Se content and mRNA levels of SelW at 15, 25, 35, 45 and 55days old. In the H group, a significant increase (P<0.05) in mRNA levels of SelW was observed. When the chickens were fed a Se-deficient basal diet, the abundance of SelW mRNA significantly decreased (P<0.05) during the sampling period. In this study, two enzymes were also examined, namely, selenocysteine-tRNA([Ser]Sec) synthase (SecS) and selenophosphate synthetase 1 (SPS1). The mRNA levels of two factors were slightly enhanced in the Se-supplemented groups, and a Se-deficient diet down regulated the mRNA expression of SecS. These data indicate that SelW is expressed in the pancreatic tissue of birds and that the transcription of the SelW gene is very sensitive to dietary Se. Se also has an effect on the mRNA levels of SecS, but has a little effect on SPS1 in this study.

Effects of dietary selenium on selenoprotein W gene expression in the chicken immune organs.

Selenoprotein W (SelW) is expressed in the immune systems of mammals. However, its pattern of expression in the immune organs of birds is still unclear. To investigate the distribution of SelW and effects of dietary Se levels on the SelW mRNA expression in the immune organs of birds, 1-day-old male chickens were fed either a commercial diet or an Se-supplemented diet containing 0.601, 1.058, 1.514, or 2.427 mg Se per kilogram, and 1.0, 2.0, 3.0 or 5.0 mg sodium selenite per kilogram for 90 days. The immune organs (spleen, thymus, and bursa of Fabricius) were collected and examined for Se content and SelW mRNA levels. The mRNA expression of SelW was detected in all the tissues. Although Se content was the highest in the spleen, the remarkable stability of the SelW mRNA level was observed in this organ during different times of dietary Se supplementation. Se-supplemented diet can make the SelW expression levels higher within a certain range in thymus and bursa of Fabricius. The present study demonstrates that SelW is widely expressed in immune organs of birds and that Se-supplementation of the feed increases SelW expression in the thymus and the bursa of Fabricius.

Dietary selenium affects selenoprotein W gene expression in the liver of chicken.

As selenium in the form of "Selenoprotein W (SelW)" is essential for the maintenance of normal liver function, the expression of SelW liver depends on the level of selenium supplied with the diet. Whereas this is well known to be the case in mammals, relatively little is known about the effect of dietary Se on the expression SelW in the livers of avian species. To investigate the effects of dietary Se levels on the SelW mRNA expression in the liver of bird, 1-day-old male chickens were fed either a commercial diet or a Se-supplemented diet containing 1.0, 2.0, 3.0, and 5.0 mg/kg sodium selenite (Na(2)SeO(3)) for 90 days. The livers were collected and examined for Se content and mRNA levels of SelW, Selenophosphate synthetase-1, and selenocysteine-synthase (SecS). The data indicate that, within a certain range, a Se-supplemented diet can increase the expression of SelW and the mRNA levels of SecS, and also, that the transcription of SelW is very sensitive to dietary Se.

Characterization and expression of chicken selenoprotein W.

As an essential trace element, selenium (Se) deficiency results in White Muscle Disease in livestock and Keshan disease in humans. The main objectives of this study were to clone and characterize the chicken selenoprotein W (SeW) gene and investigate SeW mRNA expression in chicken tissues. The deduced amino acid (AA) sequence of chicken SeW contains 85 AAs with UAG as the stop codon. Like all SeW genes identified in different species, chicken SeW contains one well-conserved selenocysteine (Sec) at the 13th position encoded by the UGA codon. The proposed glutathione (GSH)-binding site at the Cys(37) of SeW is not conserved in the chicken, but Cys(9) and Sec(13), with possible GSH binding, are conserved in SeWs identified from all species. There are 23-59% and 50-61% homology in cDNA and deduced AA sequences of SeW, respectively, between the chicken and other species. The predicted secondary structure of chicken SeW mRNA indicates that the selenocysteine insertion sequence element is type II with invariant adenosines within the apical bulge. The SeW mRNA expression is high in skeletal muscle followed by brain, but extremely low in other tissues from chickens fed a commercial maize-based diet. The SeW gene is ubiquitously expressed in heart, skeletal muscle, brain, testis, spleen, kidney, lung, liver, stomach and pancreas in chickens fed a commercial diet supplemented with sodium selenite. These results indicate that dietary selenium supplementation regulates SeW gene expression in the chicken and skeletal muscle is the most responsive tissue when dietary Se content is low.

Selenoprotein W gene expression in the gastrointestinal tract of chicken is affected by dietary selenium.

Selenoprotein W (SelW) and selenium (Se) plays important roles in gastrointestinal function and that SelW expression in the gastrointestinal system of mammals is sensitive to Se levels. However, little is known about the pattern of SelW expression in the bird gastrointestinal tract. To investigate the distribution of SelW and effects of dietary Se levels on the SelW mRNA expression in the gastrointestinal tract tissues of birds, 1-day-old male chickens were fed either a commercial diet or a Se-supplemented diet containing 1.0, 2.0, 3.0 or 5.0 mg/kg sodium selenite for 90 days. The gastrointestinal tract tissues (tongue, esophagus, crop, proventriculus, gizzard, duodenum, small intestine, cecum and rectum) were collected and examined for Se content and mRNA levels of SelW. The mRNA expression of SelW was detected in all tissues. The greatest increase in SelW mRNA levels was observed in the gizzard, whereas Se content was highest in the duodenum and small intestine. A significant increase in SelW mRNA levels was observed in the gastrointestinal tract tissues of chickens fed the diets containing 1-3 mg/kg sodium selenite while decreased SelW mRNA levels were observed in the esophagus, crop, proventriculus, gizzard, duodenum and cecum in chickens fed the diet containing 5 mg/kg sodium selenite. These data indicate that SelW is widely expressed in the gastrointestinal tract tissues of birds and the transcription of the SelW gene is very sensitive to dietary Se.

Enhanced water-holding capacity of meat was associated with increased Sepw1 gene expression in pigs fed selenium-enriched yeast.

To study the effect of selenium-enriched yeast (SeY) level on selenoprotein genes expression and the relation between gene expression and antioxidant status and meat quality, 30 selenium (Se)-depleted pigs (7-week old, 10.30±0.68 kg) were randomly divided into 3 groups and fed a basal diet plus 0, 0.3 and 3.0 mg Se/kg as SeY for 8 weeks. Results showed that dietary SeY supplementation improved the antioxidant status in muscle. The increased levels of SeY decreased (P<0.05) the drip loss and the concentration of thiobarbituric acid reactive substances in the muscle and meat. However, increased dietary SeY intake quadratically increased (P<0.01) the mRNA level of Sepw1 gene among the 12 selenoprotein genes examined in muscle. Statistical analysis showed drip loss was negatively correlated with the mRNA level of Sepw1 gene. These suggested that the enhanced water-holding capacity of meat was associated with the increased expression of Sepw1 gene.