4β-HC is a unique LXR ligand that drives SREBP1c expression. A: Oxysterol screen for LXR target gene expression. Huh7 cells were treated with indicated oxysterols (20 μM) in 24-h time course. ABCA1 mRNA levels or (B) SREBP1c mRNA level were measured by RT-PCR (N = 3). C: Dose-response curves of 4β-HC and 24-HC in Huh7 cells were treated for 24 h. mRNA levels of ABCA1, (D) ABCG1, and (E) SREBP1c were measured by RT-PCR. Line plotted by nonlinear fit (N = 3). E: SREBP1c induction by 4β-HC is stereospecific. Huh7 cells were treated with 4β-HC or an enantiomer of 4β-HC (ent-4HC) for 24 h in the indicated concentration (N = 3). Bars are the mean + SD. Statistical significance calculated by one-way ANOVA. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001. NS, not significant; 4β-HC, 4β-hydroxycholesterol.