FIGURE 1.

XN reduces SREBP activity and de novo synthesis of fatty acid and cholesterol. A, Huh-7/FAS cells were depleted of sterols by incubating in medium B for 16 h. The cells were then switched to medium B in the presence of vehicle, 1 μg/ml (2.5 μm) 25-HC, 10 μm XN, or 30 μm XN. After incubation for 24 h, luciferase assay was performed, and relative luciferase activity was obtained by normalization to the activity in the presence of the vehicle. B, structure of XN. C, Huh-7 cells were depleted of sterols by incubating in medium C for 16 h. The cells were then switched to medium C in the presence of vehicle, 10 μm XN, or 30 μm XN. After incubation for 24 h, total RNA was isolated from the cells. Real time quantitative PCR was performed, and relative mRNA levels were obtained by normalization to GAPDH mRNA. D, Huh-7 cells were cultured with medium D for 16 h. The cells were then switched to medium D in the presence of vehicle, 10 μm XN, or 30 μm XN. After incubation for 18 h, the cells were treated with 1.6 μCi/ml [¹⁴C]acetate and cultured for an additional 6 h. Fatty acid and cholesterol were extracted, and synthesis rates were determined. All data are presented as means ± S.E. (n = 3). Different superscript letters denote statistical significance (p < 0.05).