Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine
Fig 8
Poorly absorbable sitosterol and sitostanol show greater efflux efficiencies than cholesterol.
A, Time-course uptake of 3H-cholesterol (circles), 3H-sitosterol (squares), and 3H-sitostanol (triangles) by differentiated Caco-2 cells. Plots are shown as mean of duplicate assays. B, An illustrated protocol for the luminal perfusion assay with sitosterol or sitostanol tracers. Assay time course is indicated from left to right. Open triangles show time points when reagents were given to mice. C, Upper; Plots for 3H-decay per minute (DPM) counts in the perfusate (right, gray circles) and perfused intestinal segment (left, open circles). Lower; Comparison of efflux efficiency of three tracers: cholesterol, sitosterol, and sitostanol. D, Change in 3H abundance per cm of intestinal segment during luminal perfusion assay with 3H-sitosterol or 3H-sitostanol. Bars indicate medians. Each plot shows an individual assay result. E, Comparison of sterol absorption efficiency (cholesterol absorption efficiency as 100%) with efflux efficiency for cholesterol, sitosterol, and sitostanol. Sterol absorption efficiencies were obtained from Igel et al. (Ref. 10), in which absorption efficiencies for sitosterol and sitostanol were estimated as 7% and 1%, respectively. Efflux efficiencies were obtained from C. F, Efflux efficiency of three sterol tracers in ABCG5/G8 double knockout (DKO) mice. Upper; Plots for 3H-DPM counts in the perfusate (right, gray circles) and perfused intestinal segment (left, open circles). Lower; Effect of ABCG5/G8 DKO on sterol efflux efficiency. P values were obtained using the Student’s t-test (sitostanol and cholesterol) or the Mann—Whitney U test (sitosterol) for comparison of efflux efficiency. Each plot shows an individual assay result.