Fatty acid synthase is essential for milk fat formation in goat mammary gland
The inevitable role of fatty acid synthase (FASN) on fatty acid metabolism has been a validated concept for a quite long period of time. However, the details of its effect on milk fat formation remain to be unclear. This study explored the potential role of FASN in regulating milk fat accumulation and secretion in lactating goat mammary gland epithelial cells (GMECs). Using quantitative real-time PCR, we detected that FASN was predominantly expressed in fat, small intestine and mammary gland tissues among 10 different tissues (subcutaneous fat, small intestine, mammary gland, lungs, rumen, muscle, spleen, liver, kidney and heart) collected from 3 Xinong Saanen dairy goats at mid-lactation period. In addition, we also found a much higher expression level of FASN gene at mid-lactation mammary gland compared with dry-off period (17.9-fold) from 3 Xinong Saanen dairy goats. These results indicated the potential role of FASN in lactation. Using designed shRNA targeting FASN sequence to construct adenovirus vector with BLOCK-ITTM system, the effect of shRNA on mRNA expression of GMECs were determined after 48h incubation of infected GMECs. Inhibition of FASN by C75 (10 ng/uL) and shRNA mediated interference, with the adenovirus as infection vector, markedly reduced cellular triglyceride (TAG) content by decreasing the expression of genes related to TAG synthesis (glycerol-3-phosphate acyltransferase, GPAT; 1-acylglycerol-3-phosphate O-acyltransferase, AGPAT6; diacylglycerol acyltransferase 2, DGAT2) and enhancing the expression of lipolysis related genes (adipose triglyceride lipase ATGL; hormone-sensitive lipase, HSL) (except ATGL response to shRNA treatment) in GMECs. Consistent with the markedly decreased expression of the genes related to lipid droplets formation and secretion (tail-interacting protein 47 gene, TIP47; adipose differentiation-related protein, ADRP; butyrophilin 1a1, BTN1A1; xanthine oxidoreductase, XOR), cellular lipid droplets were also reduced sharply after incubation with C75 or Ad-shRNA investigated by Oil red O staining method. The results provided evidence of FASN’s essential role in TAG synthesis and secretion in GMECs. Hence, FASN may be future essential for goat milk fat formation.
fatty acid synthase; milk fat; mammary gland epithelial cells; dairy goat