Abstract
Fatty acids (FAs) can promote lipid synthesis in the mammary gland via stimulating lipogenic gene expression, but the underlying molecular mechanism is still not fully understood. Here, we showed the dose-dependent effects of palmitic acid (PA) on lipid synthesis in primary bovine mammary epithelial cells (BMECs) and explored the corresponding molecular mechanism. BMECs were treated with PA (0, 50, 100, 150, and 200 μM), and the 100 μM treatment had the best stimulatory effect on lipid synthesis and expression and maturation of sterol regulatory element-binding protein 1c (SREBP-1c) in cells. Inhibition of phosphatidylinositol 3-kinase (PI3K) almost totally blocked the stimulation of PA on SREBP-1c expression, whereas protein kinase Cα (PKCα) knockdown only partially decreased the stimulation of PA on SREBP-1c expression but abolished the stimulation of PA on its maturation. Knockdown of GPR120 did not change the stimulation of PA on the SREBP-1c signaling. G protein-coupled receptor family C group 6 member A (GPRC6A) knockdown almost totally blocked the stimulation of FA on PI3K and PKCα phosphorylation as well as SREBP-1c expression and maturation. Furthermore, PA dose-dependently promoted GPRC6A expression and plasma membrane localization. Together, these above results reveal that GPRC6A is a key mediator of PA signaling to lipid synthesis in BMECs via the PI3K/PKCα-SREBP-1c pathways.