Diet-induced obesity in the selenocysteine lyase knockout mouse

Cathodal bilateral transcranial direct-current stimulation regulates selenium to confer neuroprotection after rat cerebral ischaemia-reperfusion injury

Non-invasive transcranial direct-current stimulation (tDCS) is a safe ischaemic stroke therapy. Cathodal bilateral tDCS (BtDCS) is a modified tDCS approach established by us recently. Because selenium (Se) plays a crucial role in cerebral ischaemic injury, we investigated whether cathodal BtDCS conferred neuroprotection via regulating Se-dependent signalling in rat cerebral ischaemia-reperfusion (I/R) injury. We first showed that the levels of Se and its transport protein selenoprotein P (SEPP1) were reduced in the rat cortical penumbra following I/R, whereas cathodal BtDCS prevented the reduction of Se and SEPP1. Interestingly, direct-current stimulation (DCS) increased SEPP1 level in cultured astrocytes subjected to oxygen-glucose deprivation reoxygenation (OGD/R) but had no effect on SEPP1 level in OGD/R-insulted neurons, indicating that DCS may increase Se in ischaemic neurons by enhancing the synthesis and secretion of SEPP1 in astrocytes. We then revealed that DCS reduced the number of injured mitochondria in OGD/R-insulted neurons cocultured with astrocytes. DCS and BtDCS prevented the reduction of the mitochondrial quality-control signalling, vesicle-associated membrane protein 2 (VAMP2) and syntaxin-4 (STX4), in OGD/R-insulted neurons cocultured with astrocytes and the ischaemic brain respectively. Under the same experimental conditions, downregulation of SEPP1 blocked DCS- and BtDCS-induced upregulation of VAMP2 and STX4. Finally, we demonstrated that cathodal BtDCS increased Se to reduce infract volume following I/R. Together, the present study uncovered a molecular mechanism by which cathodal BtDCS confers neuroprotection through increasing SEPP1 in astrocytes and subsequent upregulation of SEPP1/VAMP2/STX4 signalling in ischaemic neurons after rat cerebral I/R injury. KEY POINTS: Cathodal bilateral transcranial direct-current stimulation (BtDCS) prevents the reduction of selenium (Se) and selenoprotein P in the ischaemic penumbra. Se plays a crucial role in cerebral ischaemia injury. Direct-current stimulation reduces mitochondria injury and blocks the reduction of vesicle-associated membrane protein 2 (VAMP2) and syntaxin-4 (STX4) in oxygen-glucose deprivation reoxygenation-insulted neurons following coculturing with astrocytes. Cathodal BtDCS regulates Se/VAMP2/STX4 signalling to confer neuroprotection after ischaemia.

The Effect of Selenium, Zinc, and their Combined Supplementation on Cardiometabolic Biomarkers-comparing their Effects in the Energy Restriction and High-fat Diet Methods in Obese Rats

INTRODUCTION

The fat distribution in the body determines the risk of cardiometabolic problems such as heart disease and diabetes. Some dietary supplements, such as selenium and zinc, possess lipolytic and anti-angiogenic functions, which may be a useful strategy in reducing the risk of cardiometabolic complications. This study evaluated the effect of zinc (Zn), selenium (Se), and their combined supplementation on cardiometabolic risk factors in male Wistar rats in two nutritional models, including caloric restriction (CR) and high-fat diet (HFD).

METHODS AND MATERIALS

The 48 male Wistar rats were divided into three diet groups (HFD and CR and normal diet (ND)). The HFD group was subdivided into four groups (N=8 rats in each group) that received (HFD+Se), (HFD+Zn), (HFD+Zn+Se), and HFD alone as the control group, respectively. After 8 weeks of intervention, biochemical tests were performed on serum levels, including measurement of lipid profile (triglyceride, Cholesterol, LDL and HDL) and glycemic indices (fasting blood sugar, insulin and insulin sensitivity markers).

RESULTS

The results showed that supplementation significantly improved the lipid profile (P <0.001). A comparison of glucose homeostasis indices in the study groups also showed a significant difference. The serum level of glucose was higher in the HFD group than in the intervention groups (P <0.001). Also, the rate of improvement of lipid profile and glycemic indexes in the group receiving the combination of two supplements showed a better trend than those receiving zinc and selenium alone. However, the values were statistically significant only for glucose homeostasis indices (P <0.001).

CONCLUSION

Although obesity is a multifactorial condition, controlling other risk factors, zinc and selenium and their combined supplementation can lead to promising solutions for the treatment of obesity-induced glucose and lipid homeostasis disorders.

Excess selenium intake is associated with microalbuminuria in female but not in male among adults with obesity: Results from NHANES 2009-2018

Introduction

Selenium is a critical trace element with antioxidant activities that has been related to the preservation of kidney function. Few studies, however, have looked at the effects of excess selenium on kidneys. The purpose of the present study was performed to investigate the relationship between dietary selenium intake and the prevalence of microalbuminuria in American adults with obesity.

Methods

A total of 8,547 participants with obesity in the National Health and Nutrition Examination Survey (NHANES) with the age of 19 years or older were included in the present study. Multivariable regression and subgroup analyses were performed to examine the association between dietary selenium and microalbuminuria in the two genders, separately. A selenium intake above the median was defined as high selenium intake.

Results

Dietary selenium intake was significantly higher in men compared to women (139.49 μg/day vs. 101.06 μg/day; P < 0.0001). Among female participants, the prevalence of microalbuminuria was significantly higher in participants with a high selenium intake compared with those without a high selenium intake (13.82 vs. 9.96%; P = 0.008), whereas this difference did not exist in male participants (10.79 vs. 11.97%; P = 0.40). Dietary selenium is not significantly correlated with microalbuminuria (P = 0.68) in the male population, whereas each 1 μg/day of increase in selenium consumption was independently associated with a 6h higher risk of microalbuminuria (OR = 1.006; 95% CI, 1.001-1.011, P = 0.01) in females.

Conclusion

According to our research, excessive selenium consumption is positively correlated with microalbuminuria in females with obesity, but not in males with obesity.

Selenium in Bodily Homeostasis: Hypothalamus, Hormones, and Highways of Communication

The ability of the body to maintain homeostasis requires constant communication between the brain and peripheral tissues. Different organs produce signals, often in the form of hormones, which are detected by the hypothalamus. In response, the hypothalamus alters its regulation of bodily processes, which is achieved through its own pathways of hormonal communication. The generation and transmission of the molecules involved in these bi-directional axes can be affected by redox balance. The essential trace element selenium is known to influence numerous physiological processes, including energy homeostasis, through its various redox functions. Selenium must be obtained through the diet and is used to synthesize selenoproteins, a family of proteins with mainly antioxidant functions. Alterations in selenium status have been correlated with homeostatic disturbances in humans and studies with animal models of selenoprotein dysfunction indicate a strong influence on energy balance. The relationship between selenium and energy metabolism is complicated, however, as selenium has been shown to participate in multiple levels of homeostatic communication. This review discusses the role of selenium in the various pathways of communication between the body and the brain that are essential for maintaining homeostasis.

Selenium and selenoproteins in thermogenic adipocytes

Selenium (Se) is involved in energy metabolism in the liver, white adipose tissue, and skeletal muscle, and may also play a role in thermogenic adipocytes, i.e. brown and beige adipocytes. Thereby this micronutrient is a key nutritional target to aid in combating obesity and metabolic diseases. In thermogenic adipocytes, particularly in brown adipose tissue (BAT), the selenoprotein type 2 iodothyronine deiodinase (DIO2) is essential for the activation of adaptive thermogenesis. Recent evidence has suggested that additional selenoproteins may also be participating in this process, and a role for Se itself through its metabolic pathways is also envisioned. In this review, we discuss the recognized effects and the knowledge gaps in the involvement of Se metabolism and selenoproteins in the mechanisms of adaptive thermogenesis in thermogenic (brown and beige) adipocytes.

Selenium status and type 2 diabetes risk

Optimal selenium (Se) status is necessary for overall health. That status can be affected by food intake pattern, age, sex, and health status. At nutritional levels of intake, Se functions metabolically as an essential constituent of some two dozen selenoproteins, most, if not all, of which have redox functions. Insufficient dietary intake of Se reduces, to varying degrees, the expression of these selenoproteins. Recent clinical and animal studies have indicated that both insufficient and excessive Se intakes may increase risk of type 2 diabetes mellitus (T2D), perhaps by way of selenoprotein actions. In this review, we discuss the current evidence linking Se status and T2D risk, and the roles of 14 selenoproteins and other proteins involved in selenoprotein biosynthesis. Understanding such results can inform the setting of safe and adequate Se intakes.

Single-nucleus RNA-sequencing reveals singular gene signatures of human ductal cells during adaptation to insulin resistance

Adaptation to increased insulin demand is mediated by β cell proliferation and neogenesis, among other mechanisms. Although it is known that pancreatic β cells can arise from ductal progenitors, these observations have been limited mostly to the neonatal period. We have recently reported that the duct is a source of insulin-secreting cells in adult insulin-resistant states. To further explore the signaling pathways underlying the dynamic β cell reserve during insulin resistance, we undertook human islet and duct transplantations under the kidney capsule of immunodeficient NOD/SCID-γ (NSG) mouse models that were pregnant, were insulin-resistant, or had insulin resistance superimposed upon pregnancy (insulin resistance + pregnancy), followed by single-nucleus RNA-Seq (snRNA-Seq) on snap-frozen graft samples. We observed an upregulation of proliferation markers (e.g., NEAT1) and expression of islet endocrine cell markers (e.g., GCG and PPY), as well as mature β cell markers (e.g., INS), in transplanted human duct grafts in response to high insulin demand. We also noted downregulation of ductal cell identity genes (e.g., KRT19 and ONECUT2) coupled with upregulation of β cell development and insulin signaling pathways. These results indicate that subsets of ductal cells are able to gain β cell identity and reflect a form of compensation during the adaptation to insulin resistance in both physiological and pathological states.

The Role of Selenoprotein Tissue Homeostasis in MetS Programming: Energy Balance and Cardiometabolic Implications

Selenium (Se) is an essential trace element mainly known for its antioxidant, anti-inflammatory, and anti-apoptotic properties, as it is part of the catalytic center of 25 different selenoproteins. Some of them are related to insulin resistance (IR) and metabolic syndrome (MetS) generation, modulating reactive oxygen species (ROS), and the energetic sensor AMP-activated protein kinase (AMPK); they can also regulate the nuclear transcription factor kappa-B (NF-kB), leading to changes in inflammation production. Selenoproteins are also necessary for the correct synthesis of insulin and thyroid hormones. They are also involved in endocrine central regulation of appetite and energy homeostasis, affecting growth and development. MetS, a complex metabolic disorder, can appear during gestation and lactation in mothers, leading to energetic and metabolic changes in their offspring that, according to the metabolic programming theory, will produce cardiovascular and metabolic diseases later in life. However, there is a gap concerning Se tissue levels and selenoproteins’ implications in MetS generation, which is even greater during MetS programming. This narrative review also provides an overview of the existing evidence, based on experimental research from our laboratory, which strengthens the fact that maternal MetS leads to changes in Se tissue deposits and antioxidant selenoproteins’ expression in their offspring. These changes contribute to alterations in tissues’ oxidative damage, inflammation, energy balance, and tissue function, mainly in the heart. Se imbalance also could modulate appetite and endocrine energy balance, affecting pups’ growth and development. MetS pups present a profile similar to that of diabetes type 1, which also appeared when dams were exposed to low-Se dietary supply. Maternal Se supplementation should be taken into account if, during gestation and/or lactation periods, there are suspicions of endocrine energy imbalance in the offspring, such as MetS. It could be an interesting therapy to induce heart reprogramming. However, more studies are necessary.

Female Mice with Selenocysteine tRNA Deletion in Agrp Neurons Maintain Leptin Sensitivity and Resist Weight Gain While on a High-Fat Diet

The role of the essential trace element selenium in hypothalamic physiology has begun to come to light over recent years. Selenium is used to synthesize a family of proteins participating in redox reactions called selenoproteins, which contain a selenocysteine residue in place of a cysteine. Past studies have shown that disrupted selenoprotein expression in the hypothalamus can adversely impact energy homeostasis. There is also evidence that selenium supports leptin signaling in the hypothalamus by maintaining proper redox balance. In this study, we generated mice with conditional knockout of the selenocysteine tRNA^[Ser]Sec gene (Trsp) in an orexigenic cell population called agouti-related peptide (Agrp)-positive neurons. We found that female Trsp^AgrpKO mice gain less weight while on a high-fat diet, which occurs due to changes in adipose tissue activity. Female Trsp^AgrpKO mice also retained hypothalamic sensitivity to leptin administration. Male mice were unaffected, however, highlighting the sexually dimorphic influence of selenium on neurobiology and energy homeostasis. These findings provide novel insight into the role of selenoproteins within a small yet heavily influential population of hypothalamic neurons.

Effect of statin treatment in obese selenium-supplemented mice lacking selenocysteine lyase

People with obesity are often dyslipidemic and prescribed statins to prevent cardiovascular events. A common side effect of statin use is myopathy. This could potentially be caused by the reduction of selenoproteins that curb oxidative stress, in turn, affecting creatine metabolism. We determined if statins regulate hepatic and muscular selenoprotein expression, oxidative stress and creatine metabolism. Mice lacking selenocysteine lyase (Scly KO), a selenium-provider enzyme for selenoprotein synthesis, were fed a high-fat, Se-supplemented diet and treated with simvastatin. Statin improved creatine metabolism in females and oxidative responses in both sexes. Male Scly KO mice were heavier than females after statin treatment. Hepatic selenoproteins were unaffected by statin and genotype in females. Statin upregulated muscular Gpx1 in females but not males, while Scly loss downregulated muscular Gpx1 in males and Selenon in females. Osgin1 was reduced in statin-treated Scly KO males after AmpliSeq analysis. These results refine our understanding of the sex-dependent role of selenium in statin responses.

Sex-Specific Metabolic Impairments in a Mouse Model of Disrupted Selenium Utilization

The essential micronutrient selenium (Se) provides antioxidant defense and supports numerous biological functions. Obtained through dietary intake, Se is incorporated into selenoproteins via the amino acid, selenocysteine (Sec). Mice with genetic deletion of the Se carrier, selenoprotein P (SELENOP), and the Se recycling enzyme selenocysteine lyase (SCLY), suffer from sexually dimorphic neurological deficits and require Se supplementation for viability. These impairments are more pronounced in males and are exacerbated by dietary Se restriction. We report here that, by 10 weeks of age, female Selenop/Scly double knockout (DKO) mice supplemented with 1 mg/ml sodium selenite in drinking water develop signs of hyper-adiposity not seen in male DKO mice. Unexpectedly, this metabolic phenotype can be reversed by removing Se from the drinking water at post-natal day 22, just prior to puberty. Restricting access to Se at this age prevents excess body weight gain and restriction from either post-natal day 22 or 37 reduces gonadal fat deposits. These results provide new insight into the sex-dependent relationship between Se and metabolic homeostasis.

Stress and the Brain: An Emerging Role for Selenium

The stress response is an important tool in an organism’s ability to properly respond to adverse environmental conditions in order to survive. Intense acute or chronic elevation of glucocorticoids, a class of stress hormone, can have deleterious neurological effects, however, including memory impairments and emotional disturbances. In recent years, the protective role of the antioxidant micronutrient selenium against the negative impact of externally applied stress has begun to come to light. In this review, we will discuss the effects of stress on the brain, with a focus on glucocorticoid action in the hippocampus and cerebral cortex, and emerging evidence of an ability of selenium to normalize neurological function in the context of various stress and glucocorticoid exposure paradigms in rodent models.

Effects of selenium supplementation on diet-induced obesity in mice with a disruption of the selenocysteine lyase gene

BACKGROUND

The amino acid selenocysteine (Sec) is an integral part of selenoproteins, a class of proteins mostly involved in strong redox reactions. The enzyme Sec lyase (SCLY) decomposes Sec into selenide allowing for the recycling of the selenium (Se) atom via the selenoprotein synthesis machinery. We previously demonstrated that disruption of the Scly gene (Scly KO) in mice leads to the development of obesity and metabolic syndrome, with effects on glucose homeostasis, worsened by Se deficiency or a high-fat diet, and exacerbated in male mice. Our objective was to determine whether Se supplementation could ameliorate obesity and restore glucose homeostasis in the Scly KO mice.

METHODS

Three-weeks old male and female Scly KO mice were fed in separate experiments a diet containing 45 % kcal fat and either sodium selenite or a mixture of sodium selenite and selenomethionine (selenite/SeMet) at moderate (0.25 ppm) or high (0.5-1 ppm) levels for 9 weeks, and assessed for metabolic parameters, oxidative stress and expression of selenoproteins.

RESULTS

Se supplementation was unable to prevent obesity and elevated epididymal white adipose tissue weights in male Scly KO mice. Serum glutathione peroxidase activity in Scly KO mice was unchanged regardless of sex or dietary Se intake; however, supplementation with a mixture of selenite/SeMet improved oxidative stress biomarkers in the male Scly KO mice.

CONCLUSION

These results unveil sex- and selenocompound-specific regulation of energy metabolism after the loss of Scly, pointing to a role of this enzyme in the control of whole-body energy metabolism regardless of Se levels.

Sex differences in gene expression with galactosylceramide treatment in Cln3Δex7/8 mice

BACKGROUND

CLN3 disease is caused by mutations in the CLN3 gene. The purpose of this study is to discern global expression patterns reflecting therapeutic targets in CLN3 disease.

METHODS

Differential gene expression in vehicle-exposed mouse brain was determined after intraperitoneal vehicle/Galactosylceramide (GalCer) injections for 40 weeks with GeneChip Mouse Genome 430 2.0 arrays.

RESULTS

Analysis identified 66 genes in male and 30 in female brains differentially expressed in GalCer-treated versus vehicle-exposed Cln3Δex7/8 mice. Gene ontology revealed aberrations of biological function including developmental, cellular, and behavioral processes. GalCer treatment altered pathways of long-term potentiation/depression, estrogen signaling, synaptic vesicle cycle, ErbB signaling, and prion diseases in males, but prolactin signaling, selenium compound metabolism and steroid biosynthesis in females. Gene-gene network analysis highlighted networks functionally pertinent to GalCer treatment encompassing motor dysfunction, neurodegeneration, memory disorder, inflammation and astrogliosis in males, and, cataracts, inflammation, astrogliosis, and anxiety in females.

CONCLUSIONS

This study sheds light on global expression patterns following GalCer treatment of Cln3Δex7/8 mice. Understanding molecular effects of GalCer on mouse brain gene expression, paves the way for personalized strategies for treating this debilitating disease in humans.

Genetic analysis of body weight in wild populations of medaka fish from different latitudes

The genetic bases of growth and body weight are of economic and scientific interest, and teleost fish models have proven useful in such investigations. The Oryzias latipes species complex (medaka) is an abundant freshwater fish in Japan and suitable for genetic studies. We compared two wild medaka stocks originating from different latitudes. The Maizuru population from higher latitudes weighed more than the Ginoza population. We investigated the genetic basis of body weight, using quantitative trait locus (QTL) analysis of the F2 offspring of these populations. We detected one statistically significant QTL for body weight on medaka chromosome 4 and identified 12 candidate genes that might be associated with body weight or growth. Nine of these 12 genes had at least one single nucleotide polymorphism that caused amino acid substitutions in protein-coding regions, and we estimated the effects of these substitutions. The present findings might contribute to the marker-assisted selection of economically important aquaculture species.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

Combined Omics Reveals That Disruption of the Selenocysteine Lyase Gene Affects Amino Acid Pathways in Mice

Selenium is a nonmetal trace element that is critical for several redox reactions and utilized to produce the amino acid selenocysteine (Sec), which can be incorporated into selenoproteins. Selenocysteine lyase (SCL) is an enzyme which decomposes Sec into selenide and alanine, releasing the selenide to be further utilized to synthesize new selenoproteins. Disruption of the selenocysteine lyase gene (Scly) in mice (Scly-/- or Scly KO) led to obesity with dyslipidemia, hyperinsulinemia, glucose intolerance and lipid accumulation in the hepatocytes. As the liver is a central regulator of glucose and lipid homeostasis, as well as selenium metabolism, we aimed to pinpoint hepatic molecular pathways affected by the Scly gene disruption. Using RNA sequencing and metabolomics, we identified differentially expressed genes and metabolites in the livers of Scly KO mice. Integrated omics revealed that biological pathways related to amino acid metabolism, particularly alanine and glycine metabolism, were affected in the liver by disruption of Scly in mice with selenium adequacy. We further confirmed that hepatic glycine levels are elevated in male, but not in female, Scly KO mice. In conclusion, our results reveal that Scly participates in the modulation of hepatic amino acid metabolic pathways.

Selenocysteine β-Lyase: Biochemistry, Regulation and Physiological Role of the Selenocysteine Decomposition Enzyme

The enzyme selenocysteine β-lyase (SCLY) was first isolated in 1982 from pig livers, followed by its identification in bacteria. SCLY works as a homodimer, utilizing pyridoxal 5'-phosphate as a cofactor, and catalyzing the specific decomposition of the amino acid selenocysteine into alanine and selenide. The enzyme is thought to deliver its selenide as a substrate for selenophosphate synthetases, which will ultimately be reutilized in selenoprotein synthesis. SCLY subcellular localization is unresolved, as it has been observed both in the cytosol and in the nucleus depending on the technical approach used. The highest SCLY expression and activity in mammals is found in the liver and kidneys. Disruption of the Scly gene in mice led to obesity, hyperinsulinemia, glucose intolerance, and hepatic steatosis, with SCLY being suggested as a participant in the regulation of energy metabolism in a sex-dependent manner. With the physiological role of SCLY still not fully understood, this review attempts to discuss the available literature regarding SCLY in animals and provides avenues for possible future investigation.

SBP2 deficiency in adipose tissue macrophages drives insulin resistance in obesity

Proinflammatory activation and accumulation of adipose tissue macrophages (ATMs) are associated with increased risk of insulin resistance in obesity. Here, we described the previously unidentified role of selenocysteine insertion sequence-binding protein 2 (SBP2) in maintaining insulin sensitivity in obesity. SBP2 was suppressed in ATMs of diet-induced obese mice and was correlated with adipose tissue inflammation. Loss of SBP2 initiated metabolic activation of ATMs, inducing intracellular reactive oxygen species content and inflammasome, which subsequently promoted IL-1β-associated local proliferation and infiltration of proinflammatory macrophages. ATM-specific knockdown of SBP2 in obese mice promoted insulin resistance by increasing fat tissue inflammation and expansion. Reexpression of SBP2 improved insulin sensitivity. Last, an herbal formula that specifically induced SBP2 expression in ATMs can experimentally improve insulin sensitivity. Clinical observation revealed that it improved hyperglycemia in patients with diabetes. This study identified SBP2 in ATMs as a potential target in rescuing insulin resistance in obesity.

Agrp-Specific Ablation of Scly Protects against Diet-Induced Obesity and Leptin Resistance

Selenium, an essential trace element known mainly for its antioxidant properties, is critical for proper brain function and regulation of energy metabolism. Whole-body knockout of the selenium recycling enzyme, selenocysteine lyase (Scly), increases susceptibility to metabolic syndrome and diet-induced obesity in mice. Scly knockout mice also have decreased selenoprotein expression levels in the hypothalamus, a key regulator of energy homeostasis. This study investigated the role of selenium in whole-body metabolism regulation using a mouse model with hypothalamic knockout of Scly. Agouti-related peptide (Agrp) promoter-driven Scly knockout resulted in reduced weight gain and adiposity while on a high-fat diet (HFD). Scly-Agrp knockout mice had reduced Agrp expression in the hypothalamus, as measured by Western blot and immunohistochemistry (IHC). IHC also revealed that while control mice developed HFD-induced leptin resistance in the arcuate nucleus, Scly-Agrp knockout mice maintained leptin sensitivity. Brown adipose tissue from Scly-Agrp knockout mice had reduced lipid deposition and increased expression of the thermogenic marker uncoupled protein-1. This study sheds light on the important role of selenium utilization in energy homeostasis, provides new information on the interplay between the central nervous system and whole-body metabolism, and may help identify key targets of interest for therapeutic treatment of metabolic disorders.

Effect of single-nucleotide polymorphisms on specific reproduction parameters in Hungarian Large White sows

The aim of this study was to reveal the effect of single-nucleotide polymorphisms (SNPs) on the total number of piglets born (TNB), the litter weight born alive (LWA), the number of piglets born dead (NBD), the average litter weight on the 21st day (M21D) and the interval between litters (IBL). Genotypes were determined on a high-density Illumina Porcine SNP 60K BeadChip. Data screening and data identification were performed by a multi-locus mixed-model. Statistical analyses were carried out to find associations between individual genotypes of 290 Hungarian Large White sows and the investigated reproduction parameters. According to the analysis outcome, three SNPs were identified to be associated with TNB. These loci are located on chromosomes 1, 6 and 13 (-log₁₀P = 6.0, 7.86 and 6.22, the frequencies of their minor alleles, MAF, were 0.298, 0.299 and 0.364, respectively). Two loci showed considerable association (-log₁₀P = 10.35 and 10.46) with LWA on chromosomes 5 and X, the MAF were 0.425 and 0.446, respectively. Seven loci were found to be associated with NBD. These loci are located on chromosomes 5, 6, 13, 14, 15, 16 and 18 (-log₁₀P = 10.95, 5.43, 8.29, 6.72, 6.81, 5.90, and 5.15, respectively). One locus showed association (-log₁₀P = 5.62) with M21D on chromosome 1 (the MAF was 0.461). Another locus was found to be associated with IBL on chromosome 8 (-log₁₀P = 7.56; the MAF was 0.438). The above-mentioned loci provide a straightforward possibility to assist selection by molecular tools and, consequently, to improve the competitiveness of the Hungarian Large White (HLW) breed.

Selenium Deficiency Is Associated with Pro-longevity Mechanisms

Selenium (Se) is an essential trace element because of its presence in selenoproteins in the form of selenocysteine residue. Both Se deficiency, which compromises selenoprotein functions, and excess Se, which is toxic, have been associated with altered redox homeostasis and adverse health conditions. Surprisingly, we found that, although Se deficiency led to a drastic decline in selenoprotein expression, mice subjected to this dietary regimen for their entire life had normal lifespans. To understand the molecular mechanisms involved, we performed systemic analyses at the level of metabolome, transcriptome, and microRNA profiling. These analyses revealed that Se deficiency reduced amino acid levels, elevated mononucleotides, altered metabolism, and activated signaling pathways linked to longevity-related nutrient sensing. The data show that the metabolic control associated with nutrient sensing coordinately responds to suppressed selenoprotein functions, resulting in normal lifespan under Se deficiency.

N-ϒ-(l-Glutamyl)-l-Selenomethionine Inhibits Fat Storage via the Stearoyl-CoA Desaturases FAT-6 and FAT-7 and the Selenoprotein TRXR-1 in Caenorhabditis elegans

SCOPE

Selenium is an important nutrient for human health. The influence of dietary selenium on lipid metabolism remains largely unknown. N-γ-(l-glutamyl)-l-selenomethionine (Glu-SeMet) on inhibition of fat accumulation and its underlying mechanisms in the nematode Caenorhabditis elegans are investigated.

METHODS AND RESULTS

Triacylglyceride quantification and post-fixed Nile red staining methods are conducted to evaluate fat accumulation in wild-type N2 worms in normal or high-glucose diet. Glu-SeMet (0.01 µm) treatment effectively reduces fat storage in wild-type N2 C. elegans in both a normal and high-glucose diet. Further evidence shows that Glu-SeMet (0.01 µm) decreases the ratio of oleic acid/stearic acid (C18:1Δ9/C18:0) using gas chromatography-mass spectrometry analysis. The mRNA levels of fatty acid stearoyl-CoA desaturases, FAT-6 and FAT-7, and the mediator-15 (MDT-15) are downregulated while the wild-type N2 worms are co-treated with high glucose and Glu-SeMet (0.01 µm). The effect of reduced fat accumulation is absent in fat-6, fat-7, and trxr-1 mutant worms under high glucose and Glu-SeMet (0.01 µm) co-treatment.

CONCLUSIONS

This study demonstrates that Glu-SeMet inhibiting fat accumulation may be associated with FAT-6 and FAT-7 and the selenoprotein TRXR-1 in C. elegans. This study implies a potential for Glu-SeMet as a new treatment for obesity or its complications.

SEXUAL DIMORPHISM IN SELENIUM METABOLISM AND SELENOPROTEINS

Sexual dimorphism, the condition in which males and females in a species differ beyond the morphology of sex organs, delineates critical aspects of the biology of higher eukaryotes, including selenium metabolism. While sex differences in selenium biology have been described by several laboratories, delineation of the effects of sex in selenium function and regulation of selenoprotein expression is still in its infancy. This review encompasses the available information on sex-dependent parameters of selenium metabolism, as well as the effects of selenium on sex hormones. Gaps in the current knowledge of selenium and sex are identified and discussed.

A genome-wide detection of selection signatures in conserved and commercial pig breeds maintained in Poland

BACKGROUND

Identification of selection signatures can provide a direct insight into the mechanism of artificial selection and allow further disclosure of the candidate genes related to the animals' phenotypic variation. Domestication and subsequent long-time selection have resulted in extensive phenotypic changes in domestic pigs, involving a number of traits, like behavior, body composition, disease resistance, reproduction and coat color. In this study, based on genotypes obtained from PorcineSNP60 Illumina assay we attempt to detect both diversifying and within-breed selection signatures in 530 pigs belonging to four breeds: Polish Landrace, Puławska, Złotnicka White and Złotnicka Spotted, of which the last three are a subject of conservative breeding and substantially represent the native populations.

RESULTS

A two largely complementary statistical methods were used for signatures detection, including: pairwise F_ST and relative extended haplotype homozygosity (REHH) test. Breed-specific diversifying selection signals included several genes involved in processes connected with fertility, growth and metabolism which are potentially responsible for different phenotypes of the studied breeds. The diversifying selection signals also comprised PPARD gene that was previously found to have a large effect on the shape of the external ear in pigs or two genes encoding neuropeptide Y receptors (Y2 and Y5) involved in fat deposition and stress response which are important features differentiating the studied breeds. REHH statistics allowed detecting several within-breed selection signatures overlapping with genes connected with a range of functions including, among others: metabolic pathways, immune system response or implantation and development of the embryo.

CONCLUSIONS

The study provides many potential candidate genes with implication for traits selected in the individual breeds and gives strong basis for further studies aiming at identification of sources of variation among the studied pig breeds.

Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review

Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.

Multi-omic network-based interrogation of rat liver metabolism following gastric bypass surgery featuring SWATH proteomics

Morbidly obese patients often elect for Roux-en-Y gastric bypass (RYGB), a form of bariatric surgery that triggers a remarkable 30% reduction in excess body weight and reversal of insulin resistance for those who are type II diabetic. A more complete understanding of the underlying molecular mechanisms that drive the complex metabolic reprogramming post-RYGB could lead to innovative non-invasive therapeutics that mimic the beneficial effects of the surgery, namely weight loss, achievement of glycemic control, or reversal of non-alcoholic steatohepatitis (NASH). To facilitate these discoveries, we hereby demonstrate the first multi-omic interrogation of a rodent RYGB model to reveal tissue-specific pathway modules implicated in the control of body weight regulation and energy homeostasis. In this study, we focus on and evaluate liver metabolism three months following RYGB in rats using both SWATH proteomics, a burgeoning label free approach using high resolution mass spectrometry to quantify protein levels in biological samples, as well as MRM metabolomics. The SWATH analysis enabled the quantification of 1378 proteins in liver tissue extracts, of which we report the significant down-regulation of Thrsp and Acot13 in RYGB as putative targets of lipid metabolism for weight loss. Furthermore, we develop a computational graph-based metabolic network module detection algorithm for the discovery of non-canonical pathways, or sub-networks, enriched with significantly elevated or depleted metabolites and proteins in RYGB-treated rat livers. The analysis revealed a network connection between the depleted protein Baat and the depleted metabolite taurine, corroborating the clinical observation that taurine-conjugated bile acid levels are perturbed post-RYGB.

Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review

Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.

The Effect of Selenium Supplementation on Glucose Homeostasis and the Expression of Genes Related to Glucose Metabolism

The aim of the study was to evaluate the effect of selenium supplementation on the expression of genes associated with glucose metabolism in humans, in order to explain the unclear relationship between selenium and the risk of diabetes. For gene expression analysis we used archival samples of cDNA from 76 non-diabetic subjects supplemented with selenium in the previous study. The supplementation period was six weeks and the daily dose of selenium was 200 µg (as selenium yeast). Blood for mRNA isolation was collected at four time points: before supplementation, after two and four weeks of supplementation, and after four weeks of washout. The analysis included 15 genes encoding selected proteins involved in insulin signaling and glucose metabolism. In addition, HbA1c and fasting plasma glucose were measured at three and four time points, respectively. Selenium supplementation was associated with a significantly decreased level of HbA1c but not fasting plasma glucose (FPG) and significant down-regulation of seven genes: INSR, ADIPOR1, LDHA, PDHA, PDHB, MYC, and HIF1AN. These results suggest that selenium may affect glycemic control at different levels of regulation, linked to insulin signaling, glycolysis, and pyruvate metabolism. Further research is needed to investigate mechanisms of such transcriptional regulation and its potential implication in direct metabolic effects.

Selenium and Metabolic Disorders: An Emphasis on Type 2 Diabetes Risk

Selenium (Se) is a micronutrient that maintains biological functions through the action of Se containing proteins known as selenoproteins. Due to the known antioxidant effects of Se, supplements containing Se have been on the rise. While Se supplementation may be beneficial for Se deficient populations, few are at risk for Se deficiency due to the transportation of food from Se-rich regions and the rise of Se-enriched foods. Alarmingly, Se supplementation may have adverse effects in people who already receive an adequate Se supply. Specifically, an increased risk of type 2 diabetes has been reported in individuals with high baseline Se levels. However, this effect was restricted to males, suggesting the relationship between Se and glucose homeostasis may be sexually dimorphic. This review will discuss the current understanding of the interaction between Se and glucose homeostasis, including any sex differences that have been described.

Biological activity of selenium: Revisited

Selenium (Se) is an essential micronutrient that exerts multiple and complex effects on human health. Se is essential for human well-being largely due to its potent antioxidant, anti-inflammatory, and antiviral properties. The physiological functions of Se are carried out by selenoproteins, in which Se is specifically incorporated as the amino acid, selenocysteine. Importantly, both beneficial and toxic effects of Se have been reported suggesting that the mode of action of Se is strictly chemical form and concentration dependent. Additionally, there is a relatively narrow window between Se deficiency and toxicity and growing evidence suggests that Se health effects depend greatly on the baseline level of this micronutrient. Thus, Se supplementation is not an easy task and requires an individualized approach. It is essential that we continue to explore and better characterize Se containing compounds and mechanisms of action, which could be crucial for disease prevention and treatment.

The evolving versatility of selenium in biology

This editorial shortly summarizes the highlights described in the Forum, novelties about selenoproteins. Two articles describe the selenoprotein biosynthesis and the role of so far identified proteins involved, including that of selenocysteine-β-lyase, which also may link selenoproteins to energy metabolism. Novel and, in part, unexpected functions are reviewed. Thioredoxin reductase 1 (TrxR1) can change from an anti- to a pro-oxidant and appears to be involved in the regulation of the Nrf2/Keap1 system. Methionine sulfoxide reductase B1 (MsrB1) catalyzes a novel posttranslational protein modification. The membrane proteins, Sel K,S,T,N, and I, form selenylsulfide bonds leading to the formation and stabilization of protein complexes required for protein trafficking. By this mechanism, selenoprotein K (SelK) supports palmitoylation of membrane-associated proteins. Thus, selenium and selenoproteins obviously have functions by far exceeding that of counteracting oxidative stress and even also catalyzing oxidoreductive processes.