Effects of nutrient restriction and arginine treatment on oxidative stress in the ovarian tissue of ewes during the luteal phase

The aim of this study was to determine whether nutrient restriction and arginine treatment affect energy metabolism changes and oxidative stress through the mitochondrial pathway in the ovarian tissue of ewes during the luteal phase. On days 6-15 of the estrous cycle, 24 multiparous Hu sheep (BW = 43.56 ± 1.53 kg) were randomly assigned to three groups: control group (CG; n = 6), restriction group (RG; n = 9), and l-arginine group (AG; n = 9) administered Arg treatment (or vehicle) three times per day. The ewes were slaughtered at the end of treatment, and blood samples and ovaries were collected for analysis. In this study, the expression levels of antioxidase enzymes (SOD2, CAT and GPX1) and mitochondrial biogenesis-related genes (ESRRA and TFAM), as well as antioxidase activity and mitochondrial function were examined in ovarian tissue. Nutrient restriction resulted in activation of ESRRA and TFAM and an increase in relative mtDNA copy number, whereas arginine treatment led to a pronounced recovery of ovarian tissue. In addition, we observed increased AMPK phosphorylation at Thr172 and SIRT3 levels in nutrient restricted ewes, and these effects decreased with arginine treatment. In conclusion, the present results indicated that short-term nutritional restriction led to changes in energy metabolism and oxidative stress. These changes disrupted the redox balance, thus leading to apoptosis through the mitochondria-dependent apoptosis pathway. Arginine treatment altered gene expression in ovarian tissue and increased the resistance to oxidative stress and the anti-apoptosis capacity. The results presented here suggest a potential method to increase agricultural productivity and economic benefits in the sheep industry by using dietary supplementation with arginine to decrease temporary undernutrition of ewes.