Figure 5. Intestines from western diet fed Ire1b^−/−/Apoe^−/− mice secrete more lipids with apoB-lipoproteins.

Twelve week old Apoe^−/− and Ire1b^−/−/Apoe^−/− male mice (n=4) were kept on western diet for 6 weeks. (A–D) Mice were fasted overnight and injected intraperitoneally with poloxamer 407 (30 mg/mouse). After 1 hour, mice were fed 0.5 µCi of [³H]triolein or [¹⁴C]cholesterol as well as 0.2 mg of cholesterol in 15 µL of olive oil. Plasma was collected after 2 hours and separated by gel filtration to determine counts (A and B) and mass (C and D) in different lipoproteins. (E) Total RNA isolated from the intestine of Apoe^−/− (n=3) and Ire1b^−/−/Apoe^−/− (n=5) male mice fed a western diet was used to quantify mRNA levels of CD36, SR-B1, NPC1L1, ABCG5, and ABCG8. (F) To study lipid secretion, enterocytes were isolated from western diet fed overnight fasted mice and labeled for 1 h with 0.5 µCi/ml of [³H]cholesterol. Enterocytes were washed and incubated with fresh media containing 1.4 mM oleic acid containing micelles. Media was used for separating lipoproteins by density gradient ultracentrifugation and radioactivity was determined in each fraction. Fractions 1–3 and 8–10 represent chylomicrons and HDL, respectively. Each measurement was done in triplicate with 3 mice per group. Mean ± SD, *p<0.05 and **p<0.01 compared with Apoe^−/−.