Rapid communication: lipid metabolic gene expression and triacylglycerol accumulation in goat mammary epithelial cells are decreased by inhibition of <italic>SREBP-1</italic>.

Xu, Huifen; Luo, Jun; Tian, Huibin; Li, Jun; Zhang, Xueying; Chen, Zhi; Li, Ming; Loor, Juan J

In mammals, sterol regulatory element binding protein-1 (&lt;bold&gt;&lt;italic&gt;SREBP-1&lt;/italic&gt;&lt;/bold&gt;) is the master regulator of fatty acid and triacylglycerol synthesis. Recent gene silencing studies in mammary cells indicate that &lt;italic&gt;SREBP-1&lt;/italic&gt; has a central role in milk fat synthesis. However, &lt;italic&gt;SREBP-1&lt;/italic&gt; knockdown studies in goat mammary cells have not been performed; hence, its direct role in controlling mRNA expression of lipid metabolism genes and triacylglycerol synthesis remains unknown. Inhibition of &lt;italic&gt;SREBP-1&lt;/italic&gt; in goat mammary epithelial cells (&lt;bold&gt;GMEC&lt;/bold&gt;) by small interference RNA (&lt;bold&gt;siRNA&lt;/bold&gt;) markedly reduced the content of cellular triacylglycerol (~50% decrease, &lt;italic&gt;P&lt;/italic&gt; &lt; 0.05) and was partly related to downregulation of &lt;italic&gt;AGPAT6&lt;/italic&gt;, &lt;italic&gt;LPIN1&lt;/italic&gt;, and &lt;italic&gt;DGAT2&lt;/italic&gt; (−23%, −28% and −19%, respectively. &lt;italic&gt;P&lt;/italic&gt; &lt; 0.05), which are key enzymes involved in triacylglycerol synthesis, cellular triacylglycerol content and lipid droplet accumulation all decreased by &lt;italic&gt;SREBP-1&lt;/italic&gt; inhibition. The expression of lipid droplet formation and secretion genes was not altered in response to treatment. Although the lack of effect on expression of &lt;italic&gt;ACACA&lt;/italic&gt; and &lt;italic&gt;FASN&lt;/italic&gt; (rate-limiting enzymes for de novo fatty acid synthesis) with &lt;italic&gt;SREBP-1&lt;/italic&gt; knockdown was unexpected (&lt;italic&gt;P&lt;/italic&gt; &gt; 0.05), the downregulation of genes related to synthesis of acetyl-CoA and acetate activation (&lt;italic&gt;ACLY&lt;/italic&gt;, &lt;italic&gt;ACSS2,&lt;/italic&gt; and &lt;italic&gt;IDH1&lt;/italic&gt;, &lt;italic&gt;P&lt;/italic&gt; &lt; 0.05) suggests that lipogenesis was inhibited. &lt;italic&gt;SREBP-1&lt;/italic&gt; knockdown also resulted in decreased expression of genes associated with fatty acid desaturation and elongation (&lt;italic&gt;SCD1&lt;/italic&gt; and &lt;italic&gt;ELOVL6&lt;/italic&gt;, &lt;italic&gt;P&lt;/italic&gt; &lt; 0.05), long-chain fatty acid (LCFA) activation and transport (&lt;italic&gt;ACSL1&lt;/italic&gt;, &lt;italic&gt;FABP3,&lt;/italic&gt; and &lt;italic&gt;SLC27A6&lt;/italic&gt;, &lt;italic&gt;P&lt;/italic&gt; &lt; 0.05). The results underscored the essential role of &lt;italic&gt;SREBP-1&lt;/italic&gt; not only in fatty acid synthesis but also in desaturation, elongation, and esterification in GMEC. Clearly, the lack of effect on &lt;italic&gt;ACACA&lt;/italic&gt; and &lt;italic&gt;FASN&lt;/italic&gt;, both of which are considered the key lipogenic enzymes, implies that there may be different regulatory mechanisms in goat compared with bovine mammary cells.

STEROL regulatory element-binding proteins; LIPID metabolism; GENE expression; TRIGLYCERIDES; MESSENGER RNA; EPITHELIAL cells; GOATS

Journal of Animal Science, 2018, Vol 96, Issue 6, p2399

0021-8812

Academic Journal

10.1093/jas/sky069