Circ09863 Regulates Unsaturated Fatty Acid Metabolism by Adsorbing miR-27a-3p in Bovine Mammary Epithelial Cells

Fatty
acid composition plays a key role in regulating flavor and
quality of milk. Therefore, in order to improve milk quality, it is
particularly important to investigate regulatory mechanisms of milk
fatty acid metabolism. Circular RNAs (circRNAs) regulate expression
genes associated with several biological processes including fatty
acid metabolism. In this study, high-throughput sequencing was used
to detect differentially expressed genes in bovine mammary tissue
at early lactation and peak lactation. Circ09863 profiles were influenced
by the lactation stage. Functional studies in bovine mammary epithelial
cells (BMECs) revealed that circ09863 promotes triglyceride (TAG)
synthesis together with increased content of unsaturated fatty acids
(C16:1 and C18:1). These results suggested that circ09863 is partly
responsible for modulating fatty acid metabolism. Additionally, software
prediction identified a miR-27a-3p binding site in the circ09863 sequence.
Overexpression of miR-27a-3p in BMECs led to decreased TAG synthesis.
However, overexpression of circ09863 (pcDNA-circ09863) in BMECs significantly
reduced expression of miR-27a-3p and enhanced gene expression of fatty
acid synthase (FASN), a target of miR-27a-3p. Overall,
data suggest that circ09863 relieves the inhibitory effect of miR-27a-3p
on FASN expression by binding miR-27a-3p and subsequently
regulating TAG synthesis and fatty acid composition. Together, these
mechanisms provide new research avenues and theoretical bases to improve
milk quality.