The role of SREBP‐1 in lipogenesis in bovine mammary epithelial cells

Sterol regulatory element binding proteins (SREBPs) are a family of transcription factors that regulate lipid metabolism. There are 3 isoforms, SREBP-1a, SREBP-1c and SREBP-2, among which SREBP-1a and SREBP-1c regulate fatty acid synthesis. The objective of this study was to determine the role of SREBP-1 in lipogenesis in bovine mammary epithelial cells. Bovine mammary epithelial cells (MACT) were used in this study. After reaching 80% confluence in a flask, cells were reseeded to plates at a density of 2X104 cells/cm2. After overnight, cells were transfected using small interfering RNAs (siRNA), against SREBP-1 (SSI), a non-targeting sequence as negative control (NEG), and no siRNA as untreated control (UNT), according to protocol (Dharmacon Inc.). Cells were harvested for measurement of mRNA, protein and acetate incorporation after 48 h. SSI reduced SREBP-1 mRNA and protein by 76% and 98%. De novo lipogenic gene mRNA decreased almost 50% (P<0.01). Acetate incorporation also decreased significantly with SSI (P < 0.01). When SREBP-1 decreased, there was a reduction in de novo lipogenic genes and acetate incorporation, thus SREBP-1 might regulate milk fat through the de novo fatty acid synthesis pathway. This project was supported by National Research Initiative Competitive Grant no. 2009-35204-05358 from the USDA National Institute of Food and Agriculture.