FIGURE 4.

Intestine-specific MTP and ABCA1 gene deletion decrease triglyceride secretion by enterocytes. To study lipid uptake, enterocytes were isolated from 12-week-old chow diet-fed, overnight-fasted mice and radiolabeled for 1 h with 0.5 μCi/ml of [³H]oleate. After 1 h, enterocytes were washed, and lipids were isolated to determine uptake of radiolabeled fatty acid (A). For characterization of secreted lipoproteins, after 1 h of uptake, enterocytes were washed and incubated with fresh media containing 1.4 mm oleic acid containing micelles for 2 h. Isolated lipids from the cells (B) and media (C) were counted to determine total fatty acid-derived radioactivity. Media from B were lipid-extracted, and lipids were separated by thin layer chromatography to determine radioactivity in triglycerides (D), phospholipids (E), and cholesteryl esters (F). Each measurement was done in triplicate with three mice per group. Mean ± S.D. *, p < 0.05; **, p < 0.01 and ***, p < 0.001 compared with WT.