Biochemical and molecular responses to antioxidant supplementation in sheep

The biochemical and molecular effects of tomato pomace (1.3% lycopene) or grape skin (87% polyphenols) supplementation for the control of hand-on induced stress in sheep were investigated. Twenty ewes were fed with a same basal diet for a preliminary period of 30 days and thus assigned to five groups: control group without any antioxidant (CTR); α-tocopherol (VIE, 100 mg/head/day); grape skin extracts (GRA, 5.5 g/head/day); tomato pomace (TOM, 10 g/head/day); tomato pomace and grape skins (TOG, 5.5 g/head/day of grape skins and 10 g/head/day of tomato pomace). Stress was administered by sampling blood at 0, 2, 3, 5, 7, 10 and 15 days after the beginning of the antioxidant administration. For the experiment, only samples at 0, 3 and 15 days were analysed. Plasma malondialdehyde (MDA), blood glutathione (GSx) and blood glutathione peroxidase (GPx) were not affected by dietary antioxidants, but significantly changed during the experimental period for all the sheep. A significant down-regulation of mRNA glutathione-S-transferase (GST) expression was observed 3 days after the addition of grape skins (P = 0.006). After 15 days from the beginning of antioxidant administrations, the mRNA expression of cytochrome P450 (P450) showed a consistent reduction (P = 0.011) in CTR, TOM and VIE groups, and superoxide dismutase (SOD) was up-regulated for TOG, GRA and TOM groups (P = 0.000).Present results indicate that grape skins were more effective in inducing specific transcriptional activiy of genes involved in oxidant defences than tomato pomace and Vitamin E. The positive effect of Vitamin E is instead more evident in the short-term variations of GSx and GPx.