Abstract
We assessed the potential of phenolic compounds from Pistacia lentiscus (lentisk) to enhance production of milk constituents in bovine mammary epithelial cells (MEC). MEC were exposed to 0 (control), 1 or 10 ppm of polyphenols from lentisk ethanolic extract (PLEE) for 24 h. PLEE were absorbed by the MEC plasma membrane, but also penetrated the cell to accumulate in and around the nucleus. PLEE increased triglyceride content in the cell and its secretion to the medium, and significantly increased intracellular lipid droplet diameter. Compared to control, PLEE increased dose-dependently the lactose synthesis, secretion of whey proteins, and contents of casein. To evaluate mitochondrial activity under pro-oxidant load, MEC were preincubated with PLEE and exposed for 2 h to H2O2. Exposure to H2O2 increased the proportion of cells with impaired mitochondrial membrane potential twofold in controls, but not in PLEE-pre-treated cells. Accordingly, proton leakage was markedly decreased by PLEE, and coupling efficiency between the respiratory chain and ATP production was significantly enhanced. Thus, lentisk polyphenols divert energy to production of milk fat, protein and lactose, with less energy directed to cellular damage control; alternatively, PLEE enables MEC to maintain energy and oxidative status under extreme metabolic rate required for milk production and secretion, and reduces the limitation on energy required to support production.
Highlights
Selection of dairy animals for production traits results in constant physiological and metabolic stress in various organs and tissues, and especially in the mammary gland[1]
Doses of polyphenols from lentisk ethanolic extract (PLEE) used in the present study were according to preliminary dose response experiment with 1, 10 and 100 ppm of PLEE, which resulted in 99.01% ± 12.8 and 100.52% ± 29.4 and 40.9% ± 33.3 live cells, respectively, compared to 100% living cells in control group
The autofluorescence intensity was higher for the 10 ppm vs. 1 ppm PLEE treatment, whereas no autofluorescence was observed in control cells, which were not exposed to the plant extract
Summary
Selection of dairy animals for production traits results in constant physiological and metabolic stress in various organs and tissues, and especially in the mammary gland[1]. ROS are the product of cellular physiological processes, primarily oxidative phosphorylation in the mitochondria, which are the main producer of cellular ROS4 These unstable molecules are important metabolites for normal physiological activity in mammalian cells, including signal-transduction cascades and h omeostasis[5]. An alternative strategy for scavenging ROS is through the use of exogenous antioxidant resources, for example, dietary phenolic compounds which can be acquired from a dietary plant s ource[14] Some of these plant secondary metabolites, if frequently consumed, maintain high concentrations of polyphenols in different o rgans[15], which may alleviate the detrimental effects of an acute increase in ROS level. Polyphenols might affect ROS by direct neutralization or by activation of the Nrf[2] system, enhancing the cells’ capacity to quench ROS and other reactive metabolites[16,17]
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