MiR-140 downregulates fatty acid synthesis by targeting transforming growth factor alpha (TGFA) in bovine mammary epithelial cells

Fat is an indispensable nutrient and basic metabolite for sustaining life, and milk is particularly rich in fatty acids, including a variety of saturated and unsaturated fatty acids. MicroRNA (miRNA) and mRNA play an important role in the regulation of milk fat metabolism in mammary gland tissue. It has been shown that lipid metabolism has a complex transcriptional regulation, but the mechanism by which milk fat synthesis is regulated through miRNA-mRNA interactions is poorly understood. In this study, we performed transcriptome sequencing with bovine mammary gland tissue in the late lactation (270 and 315 days after parturition) to identify the key gene that regulating milk fat metabolism. A total of 1 207 differentially coexpressed genes were selected, 828 upregulated genes and 379 downregulated genes were identified. The transforming growth factor alpha (TGFA) gene was selected as the target gene, and luciferase reporter assay, Western blotting and qRT-PCR were used for further study. The results demonstrated that miR-140 was an upstream regulator of TGFA, and miR-140 could inhibit (P<0.01) unsaturated fatty acid and triglyceride (TAGs) production in bovine mammary epithelial cells (BMECs). In contrast, TGFA promoted (P<0.01) unsaturated fatty acid and TAG production. Rescue experiments further indicated the miR-140/TGFA regulatory mechanism. Taken together, these results suggest that the miR-140/TGFA pathway can inhibit (P<0.01) milk fat metabolism and improve milk quality by genetic means.