Figure 1.
Mechanism of cholesterol uptake by Caco-2 cells (A–D): A, time dependence; B, concentration dependence; C, temperature dependence; D, Eadie–Hofstee plot.
The inhibitory effect of ezetimibe preincubation on cholesterol uptake by Caco-2 cells is shown (E). Values are mean ± standard error (n = 3). Statistical analyses were performed using Dunnett's multiple comparison test (*P<0.05; **P<0.01).
Figure 2.
Chemical structure of the screened polyphenols.
Figure 3.
Screening of polyphenols for their inhibitory effects on intestinal cholesterol absorption by Caco-2 cells.
Polyphenols (100 µM) were added to the cholesterol micelle solution. The mixture was maintained at 37°C for 1 h and then incubated with Caco-2 cell monolayers. Values are mean ± standard error (n = 3). Statistical analyses were performed using Dunnett's multiple comparison test (*P<0.05; **P<0.01).
Figure 4.
The relationship between the inhibitory effects of cholesterol uptake and concentrations of luteolin (A) and quercetin (B) and stability of the inhibitory effects of luteolin (100 µM), quercetin (100 µM), and ezetimibe (20 µM) (C).
Caco-2 cells were preincubated with flavonoids or ezetimibe at 37°C for 1 h, and Caco-2 cells were washed before the cholesterol uptake assay. The cholesterol micelles were added and uptake by Caco-2 cells was quantified to measure radioactivity. Values are mean ± standard error (n = 3). Statistical analyses were performed using Dunnett's multiple comparison test (*P<0.05; **P<0.01).
Figure 5.
Effects of luteolin (100 µM), quercetin (100 µM), and ezetimibe (20 µM) on cholesterol uptake by HEK293T cells.
HEK293T cells were preincubated with flavonoids or ezetimibe at 37°C for 1 h and were washed out before the cholesterol uptake assay. Then, the cholesterol micelles were added, and their uptake was quantified to measure radioactivity. Values are mean ± standard error (n = 3). Statistical analyses were performed using Dunnett's multiple comparison test. Different letters indicate significant differences; P<0.05.
Figure 6.
Body weight (A), total food intake (B), and serum concentration of cholesterol (C).
Values are mean ± standard error (n = 7 or 8). HC, high cholesterol diet (n = 7); HL, HC with 20 mM luteolin at 5 mL/kg body weight diet (n = 8); HQ, HC with 20 mM quercetin at 5 mL/kg body weight diet (n = 7); NC, noncholesterol diet (n = 7). Statistical analyses were performed using Tukey–Kramer multiple comparison test. Different letters indicate significant differences; P<0.05.
Figure 7.
Effects of 100 µM luteolin and quercetin on NPC1L1 mRNA (A) and protein (B) expression in Caco-2 cells.
Values are mean ± standard error (n = 3). Statistical analyses were performed using Tukey–Kramer multiple comparison test (*P<0.05; **P<0.01).