Body weight loss in beef cows: II. Increased antioxidant messenger ribonucleic acid levels in skeletal muscle but not erythrocyte antioxidant activity.

Twenty-six Angus-cross cows were used to examine the effect of BW loss (WL) on skeletal muscle and erythrocyte markers of oxidative stress. Serum NEFA concentrations, erythrocyte superoxide dismutase, and glutathione peroxidase activities were measured during WL and BW maintenance. Real-time reverse-transcription-PCR was used to determine mRNA levels of antioxidant genes during both periods to assess skeletal muscle response to WL. Body weight loss resulted in elevated serum NEFA concentrations but no change in erythrocyte superoxide dismutase and glutathione peroxidase activities. During WL, mRNA levels of the antioxidant genes glutathione peroxidase 4, mitochondrial superoxide dismutase, thioredoxin reductase 1, and selenoprotein W increased. Abundance of mRNA of genes involved in antioxidant signaling, specifically, PPARgamma coactivator-1 alpha, nuclear respiratory factor 1, estrogen-related receptor alpha, and tumor protein 53, was also increased. In summary, during WL cows had no change in peripheral antioxidant enzyme activity, but mRNA abundance of proteins involved in protecting the body from oxidative stress increased in skeletal muscle. During times when NEFA are used as a fuel source, signals such as mild reactive oxygen species production or increased concentration of lipid by-products activate the transcription of nuclear signaling molecules such as PPARgamma gamma coactivator-1 alpha, nuclear respiratory factor 1, estrogen-related receptor alpha, and tumor protein 53. These genes work to activate antioxidant genes such as mitochondrial superoxide dismutase, glutathione peroxidase 4, and thioredoxin reductase 1 to aid in the detoxification of reactive oxygen species. These data suggest an important role for antioxidant genes to protect cattle that are mobilizing body fat.