Fig. 8

Knockdown of LXRB decreases the activity of SCD promoter and the schematic model of LXR-SREBP1 network regulating the cellular homeostasis. Panel A: The goat mammary epithelial cells were transfected with the activity of SCD1 promoter containing a wild type construct (SCD1-wild) or a mutation of the SREBP1 response element (SCD1-SREM) and incubated with the LXR agonist T09 or dimethyl sulfoxide (DMSO). Treatments were replicated 5 times. The values are means ± SEM. The different letters denote significant (P < 0.05) differences. Panel B: Model of LXRB-SREBP1 network regulating lipogenic homeostasis in goat mammary epithelial cells. After activated by the ligand, LXRB regulates several downstream lipogenic genes directly or in an SREBP1-dependent manner. The LXRB and SREBP1 network increased cellular polyunsaturated fatty acids through controlling the activity of stearoyl-CoA desaturase 1 (SCD1) and elongation of very long chain fatty acids protein 5, 6 and 7 (ELOVL5–7). These endogenous PUFA would act as natural ligands participating in milk synthesis and secretion and contribute the cellular homeostasis