Walnut oil inhibits SCD1 through a FXR pathway in THP-1 MDFC. (A) Activation of walnut oil on nuclear receptor ligand binding domain of Dual Luciferase Reporter Assay. PPAR: peroxisome proliferator-activated receptor; LXR: liver-X-receptor; RXR: retinoic-X-receptor; PXR: pregnane-X-receptor; FXR: farnesoid-X-receptor. (B) SCD1 protein (top) and mRNA (bottom) changes following nuclear receptor agonists treatment. SCD1 protein change was detected by Western blot. Treatments are as follows: Lane 1: DMSO control; Lane 2: ciprofibrate 100 μM (PPAR-α agonist); Lane 3: GW501506 500 nM (PPAR-β agonist); Lane 4: rosiglitazone 10 μM (PPAR-γ agonist); Lane 5: TO901317 5 μM (LXR agonist); Lane 6: 9-cis RA 100 nM (RXR agonist); Lane 7: rifamipicin 25 μM (PXR agonist); Lane 8: GW4064 10 μM (FXR agonist). (C) FXR activation increases cholesterol efflux. (D) FXR activation decreases SCD1 expression. THP-1 MDFCs were treated with 10 μM GW4064 (FXR agonist), walnut oil (0.5 mg/mL), 100 μM ALA in the presence or absence of 50 μM GGS (FXR antagonist). Bars not sharing common letters are significantly different. (E) Walnut oil and ALA activate FXR and increase its target gene SHP expression. (F) Overexpression of SHP inhibits SCD1 expression in MDFC. THP-1 derived macrophages were transfected with pCMX-hSHP and empty plasmid (control) for 24 h. Symbol * in all figure panels indicates a significant difference from respective control (P < 0.05). The data presented are means ± SEM of triplicate wells of two independent experiments.