Selenium (Se), a micronutrient essential for human health, is incorporated into at least 25 selenoproteins including selenoprotein P (SePP), which transports Se within the body. This research identified two single nucleotide polymorphisms (SNPs) in the SePP gene, one in the coding region (position 24731, causing an Ala to Thr change) and one in the 3'untranslated region (position 25191). Their frequency was similar in Caucasian, Chinese, and South Asian populations. Prospectively genotyped volunteers were supplemented for 6 wk with 100 microg sodium selenite/day. Blood samples were analyzed for plasma Se and selenoprotein biomarkers at baseline, after supplementation, and during a washout period. Plasma Se, SePP, and glutathione peroxidase 3 (GPx3) levels increased with supplementation. Baseline plasma Se content depended on both SePP genotypes and body mass index. Presupplementation SePP concentration was associated with gender and genotype at SNP 24731 and postsupplementation concentration with SNP 25191. Both SNPs and gender were associated with differences in GPx3 activity, plasma, and erythrocyte thioredoxin reductase 1 concentrations and lymphocyte glutathione peroxidase 1 and 4 activities and concentrations. In conclusion, the data reveal two common functional SNPs within the human SePP gene that may predict behavior of biomarkers of Se status and response to supplementation and thus susceptibility to disease.

Background: Selenium is essential for health in humans. Selenium is present as selenocysteine in selenoproteins such as the glutathione peroxidases (GPx). Selenocysteine incorporation requires specific structures in the 3Јuntranslated region (3ЈUTR) of selenoprotein mRNAs. Objective: This study investigated the functional significance of the single-nucleotide polymorphism (SNP) GPx4c718t within the 3ЈUTR of the GPx4 gene. Design: A selenium supplementation trial was carried out with prospectively genotyped individuals of both homozygote genotypes for this SNP. Blood samples were analyzed at baseline, after a 6-wk supplementation with 100 g Se as sodium selenite/d, and during a 6-wk washout period. RNA-protein binding studies were carried out in vitro. Results: Both lymphocyte GPx1 protein concentrations and plasma GPx3 activity increased significantly after selenium supplementation in CC but not TT participants. After selenium withdrawal, there was a significant fall in both lymphocyte GPx4 protein concentrations and GPx4 activity in TT but not in CC participants; this effect was modulated by sex. RNA-protein binding assays showed that both T and C variants of transcripts corresponding to the GPx4 3ЈUTR formed complexes in vitro and that the C variant bound more strongly than did either the T variant or the GPx1 3ЈUTR. Conclusions: The GPX4c718t SNP both alters protein binding to the 3ЈUTR in vitro and influences the concentration of lymphocyte GPx4 and other selenoproteins in vivo. The latter is consistent with competition for selenium in selenoprotein synthesis, and, at low selenium intake, the SNP thus may influence susceptibility to disease.

Selenium (Se), a dietary trace metal essential for human health, is incorporated into selenoproteins as selenocysteine. Selenoprotein P (SePP), the major plasma selenoprotein, has both transport and antioxidant functions. In humans, it exists in plasma as two isoforms of approximately 50 and 60 kDa. This study investigated the effect of polymorphisms in the SEPP-1 gene, Se supplementation, and disease status on the proportions of SePP plasma isoforms. SePP was isolated from plasma from healthy volunteers, before and after a 6-week supplementation with 100 microg sodium selenite, and from colon cancer patients and controls. SePP isoform distribution was analysed by Western blot. In healthy volunteers, the relative abundance of each isoform depended on two SEPP-1 polymorphisms: rs3877899, predicted to cause an Ala-to-Thr amino acid change at position 234, and rs7579, located in the 3'-untranslated region of SEPP-1 mRNA. The difference between genotypes disappeared after Se supplementation. A genotype-dependent reduction was seen in the proportion of the 60-kDa isoform in patients with colorectal cancer compared with controls. We conclude that functional polymorphisms in the SEPP-1 gene influence the proportion of SePP isoforms in plasma. An elevated proportion of the 60-kDa isoform of SePP may increase selenoprotein synthesis and reduce colorectal cancer risk.

The effect of forage conservation method on ruminal lipid metabolism and microbial ecology was examined in 2 complementary experiments in cows. Treatments comprised fresh chopped grass, barn-dried hay, or untreated (UTS) or formic acid-treated silage (FAS) prepared from the same grass sward. Preparation of conserved forages coincided with the collection of samples from cows offered fresh grass. In the first experiment, 5 multiparous Finnish Ayrshire cows (229 d in milk) were used to compare the effects of feeding diets based on grass followed by hay during 2 consecutive 14-d periods separated by a 5-d transition during which extensively wilted grass was fed. In the second experiment, 5 multiparous Finnish Ayrshire cows (53 d in milk) were assigned to 1 of 2 blocks and allocated treatments according to a replicated 3×3 Latin square design with 14-d periods to compare the effects of hay, UTS, and FAS. Cows received 7 or 9 kg/d of the same concentrate in experiments 1 and 2, respectively. Conservation of grass by drying, but not ensiling, decreased forage fatty acid content primarily due to losses of 18:2n-6 and 18:3n-3. Compared with grass, feeding hay had no effect on dry matter intake (DMI), rumen pH, or fermentation characteristics, other than increasing ammonia content, but lowered whole-tract organic matter and fiber digestibility (experiment 1). Relative to hay, silage increased DMI, rumen volatile fatty acid (VFA) concentrations, and molar proportions of butyrate, and decreased molar acetate proportions (experiment 2). Compared with UTS, FAS increased DMI, had no effect on rumen ammonia or VFA concentrations, but tended to lower rumen pH and the molar ratio of lipogenic to glucogenic VFA. Conservation method had no substantial effect on ruminal or whole-tract digestibility coefficients. Compared with fresh grass and silages, hay decreased lipolysis and biohydrogenation (BH) of dietary unsaturates in the rumen, resulting in similar flows of 18:2n-6 and 18:3n-3, but lower amounts of trans-11 18:1 and Δ11,13 18:2 at the omasum. The extent of silage fermentation had minimal influence on ruminal lipid metabolism. Treatments were not associated with changes in the relative abundance of specific bacteria known to be capable of BH or rumen protozoal numbers. In conclusion, conservation method altered forage lipids, the extent of lipolysis and BH in the rumen, and the flow of fatty acids at the omasum, in the absence of substantial changes in ruminal Butyrivibrio populations.

Fasting is one of the simplest metabolic challenges that can be performed in humans. We here report for the first time a comprehensive analysis of the human ''fasting metabolome'' obtained from analysis of plasma and urine samples in a small cohort of healthy volunteers, using nuclear magnetic resonance (NMR), gas chromatography-and liquid chromatography-mass spectrometry (GC-MS and LC-MS). Intra-and inter-individual variation of metabolites was on measurement of four overnight fasting samples collected from each volunteer over a four week period. One additional sample per volunteer was collected following a prolonged fasting period of 36 h. Amongst a total of 377 quantified entities in plasma around 44% were shown to change significantly in concentration when volunteers extended fasting from 12 to 36 h. In addition to known markers (plasma free fatty acids, glycerol, ketone bodies) that reflect changes in the body's fuel management under fasting conditions a wide range of ''new'' entities such as a-aminobutyrate as well as other amino and keto acids were identified as fasting markers. Based on multiple correlations amongst the metabolites and selected hormones in plasma such as leptin or insulinlike-growth-factor-1 (IGF-1), a robust metabolic network with coherent regulation of a wide range of metabolites could be identified. The metabolomics approach described here demonstrates the plasticity of human metabolism and identifies new and robust markers of the fasting state.