Dietary supplementation with organic or inorganic selenium and pyridoxine in gilts on gene expression in the porcine expanded blastocysts in vivo

Abstract Text: This study aimed to determine the effect of dietary selenium (Se) and pyridoxine supplementation, in gilts, on gene expression in the porcine expanded blastocyst (PEB). Eighteen gilts were randomly assigned to one of the 3 experimental diets: 1) basal diet (natural Se content of 0.2 mg/kg) without supplemental Se or pyridoxine (CONT, n=6); 2) basal diet + 0.3 mg/kg of feed of sodium selenite, and 10 mg/kg of feed of hydrochloride pyridoxine  (MSeB₆10, n=6); and 3) basal diet + 0.3 mg/kg of feed of Se-enriched yeast, and 10 mg/kg of feed of hydrochloride pyridoxine (OSeB₆10, n=6). All gilts were inseminated at their fifth estrus, and sacrificed 5 days after. Both uterine horns were flushed for embryo harvesting. Expanded blastocysts were selected for the porcine embryo-specific microarray: direct comparisons were done for MSeB₆10 vs CONT and OSeB₆10 vs CONT, whereas a reference design comparison were used for OSeB₆10 vs MSeB₆10. Data were analyzed according to a randomized arrangement of treatments in blocks with the 3 dietary treatments as the main independent variables. Microarray data were analyzed using FlexArray, with threshold fold change ≥ 1.7 and P-value ≤ 0.05. CONT had lower blood Se concentration than Se-supplemented gilts (P<0.01), but no differences were found between Se sources (P=0.38). CONT had lower pyridoxine concentrations than B₆10 gilts (P<0.05). Plasma glutathione peroxidase (GSH-Px) activity tended to increase during the experimental period (P<0.06), but no treatment effect was detected (P=0.57). MSeB₆10 vs CONT and OSeB₆10 vs CONT respectively showed 24 and 446 differentially expressed genes, whereas the corresponding number was 190 for OSeB₆10 vs MSeB₆10. No specific biological processes were affected using Gorilla gene list analysis in MSeB₆10, however OSeB₆10 stimulated protein folding but not selenoprotein synthesis. Although all associated genes for GSH-Px and other selenoprotein synthesis were found, none of them were differentially expressed in any comparison. Antioxidant genes such as glutaredoxin-3 (GLRX3), peroxiredoxin-4 (PRDX4) and coenzyme Q6 monooxygenase (COQ6) were up-regulated in OSeB₆10 vs CONT, and thioredoxin and thioredoxin domain containing 17 were down-regulated in OSeB₆10 vs CONT and OSeB₆10 vs MSeB₆10, respectively. GLRX3, PRDX4 and COQ6 expression were validated by real-time PCR. In conclusion, OSeB₆10 affects PEB metabolism more markedly than MSeB₆10. Although supplements of both Se sources and pyridoxine did not influence GSH-Px-related genes expression in the PEB, they are involved with other antioxidant enzymes regulating antioxidant defense and cell proliferation, at this stage.

Keywords: porcine embryo, selenium, gene expression