The interplay between non-esterified fatty acids and bovine peroxisome proliferator-activated receptors: results of an

backgroundIn dairy cows circulating non-esterified fatty acids (NEFA) increase early post-partum while liver and other tissues undergo adaptation to greater lipid metabolism, mainly regulated by peroxisome proliferator-activated receptors (PPAR). PPAR are activated by fatty acids (FA), but it remains to be demonstrated that circulating NEFA or dietary FA activate bovine PPAR. We hypothesized that circulating NEFA and dietary FA activate PPAR in dairy cows.

methodsThe dose-response activation of PPAR by NEFA or dietary FA was assessed using HP300e digital dispenser and luciferase reporter in several bovine cell types. Cells were treated with blood plasma isolated from Jersey cows before and after parturition, NEFA isolated from the blood plasma, FA released from lipoproteins using milk lipoprotein lipase (LPL), and palmitic acid (C16:0). Effect on each PPAR isotype was assessed using specific synthetic inhibitors.

resultsNEFA isolated from blood serum activate PPAR linearly up to ~ 4-fold at 400 μmol/L in MAC-T cells but had cytotoxic effect. Addition of albumin to the culture media decreases cytotoxic effects of NEFA but also PPAR activation by ~ 2-fold. Treating cells with serum from peripartum cows reveals that much of the PPAR activation can be explained by the amount of NEFA in the serum (R

conclusionOur results support dose-dependent activation of PPAR by circulating NEFA in bovine, specifically δ and γ isotypes. Data also support the possibility of increasing PPAR activation by dietary FA; however, this nutrigenomics approach maybe only effective in pre-partum but not post-partum cows.