miR-148a and miR-17–5p synergistically regulate milk TAG synthesis via <i>PPARGC1A</i> and <i>PPARA</i> in goat mammary epithelial cells

MicroRNA (miRNA) are a class of ‘18–25’ nt RNA molecules which regulate gene expression and play an important role in several biologic processes including fatty acid metabolism. Here we used S-Poly (T) and high-throughput sequencing to evaluate the expression of miRNA and mRNA during early-lactation and in the non-lactating (“dry”) period in goat mammary gland tissue. Results indicated that miR-148a, miR-17–5p, <i>PPARGC1A</i> and <i>PPARA</i> are highly expressed in the goat mammary gland in early-lactation and non-lactating periods. Utilizing a Luciferase reporter assay and Western Blot, <i>PPARA</i>, an important regulator of fatty acid oxidation, and <i>PGC1a (PPARGC1A)</i>, a major regulator of fat metabolism, were demonstrated to be targets of miR-148a and miR-17–5p in goat mammary epithelial cells (GMECs). It was also revealed that miR-148a expression can regulate <i>PPARA</i>, and miR-17–5p represses <i>PPARGC1A</i> in GMECs. Furthermore, the overexpression of miR-148a and miR-17–5p promoted triacylglycerol (TAG) synthesis while the knockdown of miR-148a and miR-17–5p impaired TAG synthesis in GMEC. These findings underscore the importance of miR-148a and miR-17–5p as key components in the regulation of TAG synthesis. In addition, miR-148a cooperates with miR-17–5p to regulate fatty acid metabolism by repressing <i>PPARGC1A</i> and <i>PPARA</i> in GMECs. Further studies on the functional role of miRNAs in lipid metabolism of ruminant mammary cells seem warranted.