Natural antioxidants incorporated into Longissimus dorsi muscles of pasture or grain fed steers and their relation to gene expression

摘要

The aim of this work was to study the prooxidant/antioxidant behavior in longissimus dorsi (LD) muscle and the concomitant gene expression related to the incorporation of antioxidants. For this reason, two groups of crossbreed steers were fed either pasture diet (P): reared on winter pastures and finished on alfalfa or corn silage diet (C): 68% corn silage, 15% sunflower flour, 5% hay, 2% vit/mineral. Significant differences (P<0.05) for α-tocopherol and β-carotene were 2.24±0.44 vs. 1.66±0.49; 0.16±0.04 vs. 0.06±0.02 respectively for P vs. C samples. No differences were found for retinol, lutein and γ-tocopherol. Additionally, the effect of diet on antioxidant capacity (AOC) of hydrophilic and lipophilic antioxidants was evaluated using the FRAP-ferric reducing ability. AOC showed similar values for both groups. In addition, AOC values of the hydrophilic antioxidants were significantly higher than lipophilic values. TBARs values were similar for P and C groups in fresh samples. However, after the induction of oxidation with FeSO_4 and ascorbic acid, P samples showed a higher resistance to oxidation compared with C samples. Gene expression was determined in mRNA isolated from LD tissue by RT-PCR. Selected genes corresponded to: AOX2P: Non-selenium glutathione phospholipid-peroxidase; α TAP: a-tocopherol associated protein; α-TTP: α-tocopherol transfer protein and CRBP1: retinol binding protein. Transcription assays showed that signals for α-TAP and α-TTP were less significant for P compared to C samples. Neither AOX2P nor CRBP1 showed differential expression between diets. Pasture feeding enhanced the resistance to oxidation and could modulate gene expression related to tocopherol incorporation into LD muscle.