Circ007071 Inhibits Unsaturated Fatty Acid Synthesis by Interacting with miR-103-5p to Enhance PPARγ Expression in the Dairy Goat Mammary Gland

Understanding more precisely the mechanisms controlling the metabolism of fatty acid in the mammary gland of dairy goats is essential for future improvements in milk quality. Particularly since recent data have underscored a key role for circular RNAs (circRNAs) in the mammary gland function, high-throughput sequencing technology was used to identify expression levels of circRNAs in the mammary tissue of dairy goats during early and peak lactation in the present study. Compared with early lactation, results demonstrated that the expression level of circ007071 during peak lactation was 12.02-fold up-regulated. Subsequent studies in goat mammary epithelial cells (GMECs) revealed that circ007071 stimulated the synthesis of triglycerides (TAG) and cholesterol, as well as increased the content of saturated fatty acids (C16:0 and C18:0). More importantly, using a double luciferase reporting system allowed us to detect the circ007071 sequence at a binding site of miR-103-5p, indicating that it targeted this miRNA. Overexpression of circ007071 significantly decreased the abundance of miR-103-5p and led to inhibition of TAG synthesis. In contrast, the abundance of peroxisome proliferator-activated receptor γ (PPARγ), a target gene of miR-103-5p, was reinforced with the overexpression of circ007071. Thus, we conclude that one key function of circ007071 in the regulation of milk fat synthesis is to attenuate the inhibitory effect of miR-103-5p on PPARγ via direct interactions with miRNA. As a result, the process of TAG and saturated fatty acid is able to proceed.