Enhancement of PPARα-Inhibited Leucine Metabolism-Stimulated β-Casein Synthesis and Fatty Acid Synthesis in Primary Bovine Mammary Epithelial Cells

Leucine, a kind of branched-chain amino acid, plays a regulatory role in the milk production of mammalian mammary glands, but its regulatory functions and underlying molecular mechanisms remain unknown. This work showed that a leucine-enriched mixture (LEUem) supplementation increased the levels of milk protein and milk fat synthesis in primary bovine mammary epithelial cells (BMECs). RNA-seq of leucine-treated BMECs indicated alterations in lipid metabolism, translation, ribosomal structure and biogenesis, and inflammatory response signaling pathways. Meanwhile, the supplementation of leucine resulted in mTOR activation and increased the expression of BCKDHA, FASN, ACC, and SCD1. Interestingly, the expression of PPAR alpha was independently correlated with the leucine-supplemented dose. PPAR alpha activated by WY-14643 caused significant suppression of lipogenic genes expression. Furthermore, WY-14643 attenuated leucine-induced beta-casein synthesis and enhanced the level of BCKDHA expression. Moreover, promoter analysis revealed a peroxisome-proliferator-response element (PPRE) site in the bovine BCKDHA promoter, and WY-14643 promoted the recruitment of PPAR alpha onto the BCKDHA promoter. Together, the present data indicate that leucine promotes the synthesis of beta-casein and fatty acid and that PPAR alpha-involved leucine catabolism is the key target.

Automated summary

Leucine supplementation increases milk protein and milk fat synthesis in bovine mammary cells. It activates mTOR and increases the expression of key genes involved in lipid metabolism. PPAR alpha is independently correlated with leucine dosage and plays a role in leucine catabolism.