Regulation of selected selenoproteins in porcine and bovine skeletal muscle

Emily Nicole Terry

Selenium (Se) is a nutritionally essential trace element needed to prevent myopathies in skeletal and cardiac muscle. Selenium acts via the 21st amino acid, selenocysteine (Sec), which is incorporated into the selenoprotein family at the UGA codon during translation. Because this codon also acts as a normal stop codon, special machinery i.e., the selenocysteine insertion sequence, during translation allows UGA to signal for Sec. There are 25 described selenoproteins, with only a few having well-defined functions. However, the entire family has redox capability because Sec is located in the active site. Selenoproteins considered in this paper are glutathione peroxidase-1 (GPx-1), thioredoxin reductase-1 (TrxR-1), selenoprotein W (SelW) and selenoprotein N (Sel-N). Glutathione peroxidase-1 and Sel-W are glutathione dependent antioxidants in vivo where GPx-1 helps reduce lipid peroxides. Low activity of Sel-W is implicated in white muscle disease, a calcification of skeletal and cardiac muscle. Thioredoxin reductase-1 reduces the disulfide bridge in thioredoxin and is highly responsive to changes in oxidant status in the cell. The role of Sel-N is still undefined with the exception of an involvement in muscle cell maturation and in muscular dystrophy when the gene encoding SepN is mutated. In the current studies mRNA expression of GPx-1, Sel-W and Sel-N was measured in fetal and neonatal skeletal muscle from swine with varied maternal Se intake (adequate or deficient). Maternal intake of Se affected mRNA expression of Sel-W, but not GPx-1 or Sel-N in fetal skeletal muscle. Selenoprotein W expression in fetal skeletal muscle increased in late gestation, whereas Sel-N expression was affected by the interaction of diet by time. Additionally, Se concentration in fetal muscle was affected by maternal Se intake and decreased with gestational age. Thus, Sel-W is an important antioxidant for neonatal antioxidant protection. In another study, levels of mRNA for GPx-1, Sel-W and TrxR-1 were measured in bovine skeletal muscle during weight maintenance and weight loss, which induces oxidative stress. GPx-1 mRNA level was unaffected by weight loss whereas mRNA levels for Sel-W and TrxR-1 were upregulated during weight loss. In summary, Sel-W and TrxR-1 are important antioxidants during oxidative stress. These studies further the known action of selenoproteins in protecting cells from reactive oxygen species.

Regulation of selected selenoproteins in porcine and bovine skeletal muscle

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