Effect of all-trans retinoic acid on casein and fatty acid synthesis in MAC-T cells

Abstract

Objective: Caseins and fatty acids of milk are synthesized and secreted by the epithelial cells of the mammary gland. All-trans retinoic acid (ATRA), an active metabolite of vitamin A, has been shown to promote mammary development. This study was conducted to determine the effect of ATRA on casein synthesis and fatty acid composition in MAC-T cells.Methods: MAC-T cells were allowed to differentiate for 4 d, treated with ATRA (0, 1.0, 1.5, and 2.0 μM), and incubated for 3 d. We analyzed the fatty acid composition, the mRNA expression of casein and fatty acid synthesis-related genes, and the phosphorylation of casein synthesis-related proteins of MAC-T cells by gas chromatography, quantitative polymerase chain reaction, and western blotting, respectively.Results: In MAC-T cells, ATRA increased the mRNA levels of αS1-casein and β-casein, janus kinase 2 (JAK2) and E74-like factor 5 of the signal transducer and activator of transcription 5 β (STAT5-β) pathway, ribosomal protein S6 kinase beta-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 of the mammalian target of rapamycin (mTOR) pathway, inhibited the mRNA expression of phosphoinositide 3-kinase and eukaryotic initiation factor 4E of the mTOR pathway, and promoted the phosphorylation of STAT5-β and S6K1 proteins. Additionally, ATRA increased the de novo synthesis of fatty acids, reduced the content of long-chain fatty acids, the ratio of monounsaturated fatty acids to saturated fatty acids (SFA), the ratio of polyunsaturated fatty acids (PUFA) to SFA, and the ratio of ω-6 to ω-3 PUFA. The mRNA levels of acetyl-CoA carboxylase 1, fatty acid synthase, lipoprotein lipase, stearoyl-CoA desaturase, peroxisome proliferator-activated receptor gamma, and sterol regulatory element-binding protein 1 (SREBP1) were enhanced by ATRA.Conclusion: ATRA promotes the synthesis of casein by regulating JAK2/STAT5 pathway and downstream mTOR signaling pathway, and it improves the fatty acid composition of MAC-T cells by regulating SREBP1-related genes.

Roles of vitamin A in the regulation of fatty acid synthesis

“…The effect of RA on fatty acid synthesis in bovine mammary alveolar cells (MAC-T) have been studied[ 40 ]. MAC-T cells after being differentiated for 4 d have been treated with 0, 1.0, 1.5, and 2.0 μmol/L RA for additional 3 d. RA treatment increases the amounts of short-chain and medium-chain, saturated and monosaturated fatty acids, and reduces the amounts of long-chain and PUFAs in the cells.…”

“…MAC-T cells after being differentiated for 4 d have been treated with 0, 1.0, 1.5, and 2.0 μmol/L RA for additional 3 d. RA treatment increases the amounts of short-chain and medium-chain, saturated and monosaturated fatty acids, and reduces the amounts of long-chain and PUFAs in the cells. Interestingly, the mRNA level of Acca is reduced by 1 μmol/L RA, but induced by 2 μmol/L RA[ 40 ].…”

Effects of bamboo leaf extract on the production performance, rumen fermentation parameters, and rumen bacterial communities of heat-stressed dairy cows

“…A high rumen TVFA concentration improves the milk yield by cows, and in the present study, the increase in TVFA associated with BLE was also associated with an increase in milk yield. Acetate is the predominant substrate for de novo fatty acid synthesis in dairy cows because it serves as a 2-carbon donor for the synthesis of malonyl-CoA and for nicotinamide adenine dinucleotide phosphate synthesis through the isocitrate pathway [ 23 ]. Additionally, in well-fed cows, acetate is the major VFA produced in the rumen and provides 45% of the energy arising from VFA metabolism [ 7 ].…”

Effect of hyperthermia on cell viability, amino acid transfer, and milk protein synthesis in bovine mammary epithelial cells

“…Bovine mammary epithelial (MAC-T) cells are well-known mammary epithelial cell line and retain the phenotypic characteristics of BMECs [23][24], have been used extensively to study apoptosis in the immune response or oxidative stress [25][26], milk protein synthesis, and mammalian lactation [27][28].…”

“…In vitro , apoptosis induced by hyperthermia is also considered a response to heat stress [ 21 , 22 ]. Bovine mammary epithelial (MAC-T) cells are well-known mammary epithelial cell line and retain the phenotypic characteristics of BMECs [ 23 , 24 ], have been used extensively to study apoptosis in the immune response or oxidative stress [ 25 , 26 ], milk protein synthesis, and mammalian lactation [ 27 , 28 ]. Thus, we primarily aimed to examine the impact of heat stress on the synthesis of milk protein by incubating MAC-T cells at a hyperthermic temperature (42°C).…”