Characterization of raft microdomains in bovine mammary tissue during lactation: How they are modulated by fatty acid treatments

摘要

The objective of the current study was first to characterizelipid raft microdomains isolated as detergentresistantmembranes (DRM) from mammary glandtissue, and second to determine how dietary fatty acids(FA) such as conjugated linoleic acid (CLA), 19:1 cyclo,and long-chain n-3 polyunsaturated FA affect lipid raftmarkers of mammary cells, and to finally establish relationshipsbetween these markers and lactation performancein dairy cows. Eight Holstein cows were used ina replicated 4 × 4 Latin square design with periods of28 d. For the first 14 d, cows received daily an abomasalinfusion of (1) 406 g of a saturated FA supplement (112g of 16:0 + 230 g of 18:0) used as a control; (2) 36 g of aCLA supplement (13.9 g of trans-10,cis-12 18:2) + 370g of saturated FA; (3) 7 g of Sterculia fetida oil (3.1 g of19:1 cyclo, STO) + 399 g of saturated FA; or (4) 406 gof fish oil (55.2 g of cis-5,cis-8,cis-11,cis-14,cis-17 20:5+ 59.3 g of cis-4,cis-7,cis-10,cis-13,cis-16,cis-19 22:6,FO). Mammary biopsies were harvested on d 14 of eachinfusion period and were followed by a 14-d washoutinterval. Cholera toxin subunit B, which specificallybinds to ganglioside M-1 (GM-1), a lipid raft marker,was used to assess its distribution in DRM. Infusions ofCLA, STO, and FO were individually compared withthe control, and significance was declared at P ≤ 0.05.Milk fat yield was decreased with CLA and FO, but wasnot affected by STO. Milk lactose yield was decreasedwith CLA and STO, but was not affected by FO. Mammarytissue shows a strong GM-1-signal enrichment inisolated DRM from mammary gland tissue. Caveolin(CAV) and flotillin (FLOT) are 2 proteins consideredas lipid raft markers and they are present in DRM frommammary gland tissue. Distributions of GM-1, CAV-1,and FLOT-1 showed an effect of treatments determinedby their subcellular distributions in sucrose gradientfractions. Regardless of treatments, data showed positiverelationships between the yield of milk fat, protein,and lactose, and the abundance GM-1 in DRM fraction.Milk protein yield was positively correlated withrelative proportion of FLOT-1 in the soluble fraction,whereas lactose yield was positively correlated withrelative proportion of CAV-1 in the DRM fractions.Infusion of CLA decreased mRNA abundance of CAV-1, FLOT-1, and FLOT-2. Regardless of treatments, apositive relationship was observed between fat yield andmRNA abundance of FLOT-2. In conclusion, althoughlimited to a few markers, results of the current experimentraised potential links between variation in specificbiologically active component of raft microdomains inbovine mammary gland and lactation performances indairy cows.