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Asian-Australas J Anim Sci > Accepted Articles
DOI: https://doi.org/10.5713/ajas.19.0315    [Accepted] Published online August 23, 2019.
Effect of all-trans retinoic acid on casein and fatty acid synthesis in MAC-T cells
Xian-Dong Liao1  , Chang-Hai Zhou1  , Jing Zhang1  , Jing-Lin Shen1  , Ya-Jing Wang2  , Yong-Cheng Jin1,*  , Sheng-Li Li2,* 
1Department of Animal Science, College of Animal Science, Jilin University, Changchun, China
2State Key Laboratory of Animal Nutrition, Beijing Engineering Technology Research Center of Raw Milk Quality and Safety Control, College of Animal Science and Technology, China Agricultural University, beijing, China
Correspondence:  Yong-Cheng Jin, Tel: 0431-87836170, Fax: 0431-87836170, Email: ycjin78@163.com
Sheng-Li Li,Email: lisheng0677@163.com
Received: 12 April 2019   • Revised: 15 July 2019   • Accepted: 26 July 2019
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, qPCR, 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 (ELF5) 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 (4EBP1) of the mammalian target of rapamycin (mTOR) pathway, inhibited the mRNA expression of phosphoinositide 3-kinase (PI3K) and eukaryotic initiation factor 4E (eIF4E) 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 (MUFA) 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 (SCD), peroxisome proliferator-activated receptor gamma (PPARγ), 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.
Keywords: All-trans Retinoic Acid; Casein; Fatty Acid; mRNA Expression; MAC-T Cells


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