Sterol-CoA desaturase 1 (Scd1) plays a pivotal role in the synthesis and metabolism of fatty acids (FA). However, whether Scd1 contributes to lipid accumulation in dairy goat mammary epithelial cells (GMEC), and how it affects FA synthesis and metabolism remains unexplored. The aim of this study was to detect the effect of Scd1 on lipid droplets (LD) formation and uncover its regulatory mechanism in GMEC. In this study, a novel fluorescence reporter system was developed to confirm the expression of SCD1 protein in GMEC plasma. In addition, a mammalian expression vector (pCAG-SCD1) and siRNA targeting Scd1 were constructed and confirmed to be efficient by qRT-PCR. Notably, the amount and the size of LD varied with the alteration of Scd1. Furthermore, Scd1 induced the mRNA expression of genes involved in de novo FA synthesis, triacylglycerol (TAG) biosynthesis, lipid droplets formation, and milk fat lipolysis. In particular, changes in Scd1 led to a consistent change in LD formation-associated genes (tail-interacting protein of 47kDa (Tip47) and adipose differentiation-related protein (Adrp)). Overall, the results suggest that Scd1 affects lipid accumulation by altering the FA metabolic profile in GMEC.Practical Applications: As is known, FA metabolism closely associates with human health. The results of our research firstly exposed the metabolic profile associated with SCD1 in GMEC. It will be helpful for our understanding about the regulatory role of Scd1 in FA metabolism in mammary gland of dairy goats. It also provides a reference for the studies on Scd1-related FA metabolic pathways, which is of great significance for human health. Furthermore, this study lays the foundation for engineering the FA content via SCD1 in transgenic goat milk products. Sterol-CoA desaturase 1 (Scd1) differentially activates signaling pathways associated with de novo fatty acid (FA) synthesis (Acaca and Fasn), TAG biosynthesis (Gpam, Agpat6, and Dgat1), lipid droplets (LD) formation (Tip47 and Adrp), and milk fat lipolysis (Atgl and Hsl) in GMEC; in particular, it contributes to the LD formation through transcriptional regulation of Tip47 and Adrp.
