Effects of conjugated linoleic acids isomers on oxidative mammary gland metabolism

The study aimed at investigating the effect of CLA isomers cis- 9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12), on oxidative status of bovine mammary gland. For the study bovine epithelial cell line BME-UV1 and the aflatoxin B1 (AFB1) as oxidizing agent as experimental model have been used. The uptake rates of CLA in cells at 3 and 48h were tested using DAD HPLC analy- sis. The cells were pre-incubated with complete medium contain- ing 50 mM c9,t11, 50 mM t10,c12 and 50 mM CLA Mix (50% c9,t11 and 50% t10,c12) and then AFB1 (20 mg/mL) was added. After 48h of incubation the cells treated in the presence or absence of AFB1 were collected for determining cell viability (XTT assay), oxidative markers such as nicotinamide adenine dinucleotide phosphate (NADP+/NADPH), glutathione (GSH/GSSG), thiobar- bituric acid reactive substances (TBARS), protein carbonyl groups (CP), superoxide dismutase (SOD), glutathione peroxi- dase (GPx1), glutathioneS-transferase (GST) and glutathione reductase (GR). The mRNAs quantification of bovine GSHPx-1, GSR, GST and SOD, and milk α-CN, β-CN and α-Lalb was per- formed by rt-PCR. Data were analysed by ANOVA and differences were declared significant at P<0.05. The results showed that the uptake rates of CLA in cells increased from 3 to 48h. Cells exposed to AFB1 showed a loss of cell viability after 48h. CLA have increased (P<0.05) the concentration of reduced GSH and NADPH and decreased (P<0.01) the levels of GSSG, mostly in cells treated with t10,c12. The activity of GR and GST was decreased (P<0.05) in cells treated with CLA. Higher levels of GSPx1 and SOD (P<0.01) activities were observed in cells treat- ed with CLA in presence of AFB1. Increase of TBARS levels was observed in cells treated with CLA in presence of AFB1, whereas CP content increased both in cells treated with CLA and with CLA in presence of AFB1. Regarding the mRNA’s expression of GPX1, GR, GST and SOD no differences were observed among all treat- ments. No treatments, CLA alone or CLA plus AFB1, had a sub- stantial effect on gene expression of milk proteins. Findings of the present study corroborate an antioxidant role of CLA by developing a significant improvement of redox status in cells, in particular t10,c12. CLA treatment might enhance the intracellu- lar redox homeostasis and could be of help in improving physio-logical oxidative stress situations as the periparturient period in dairy cow.