Influence of cholesterol/fat feeding on cholesterol esterification and morphological structures in intestinal mucosa...

Guinea pigs were fed a semisynthetic diet containing 10% (by weight) cottonseed oil and 1% cholesterol. In response to cholesterol/fat feeding there was an increase in both the unesterified cholesterol (UC) and cholesteryl ester (CE) of the intestinal mucosal cell. Along with the increased cholesterol levels there was a 4-fold increase in the microsomal acylCoA:cholesterol acyltransferase (ACAT) activity after only two days of cholesterol/fat feeding. After 6 days on the experimental diet the ACAT activity was up to 8-fold the activity of the control, and then remained at this level for up to 20 days. The increased ACAT activity was probably not due to increased substrate concentration alone, since the fractional esterification of cholesterol also increased when the cholesterol/fat containing diet was given. There was also an increase in the triglyceride content of the intestinal mucosal cells from guinea pigs on the experimental diet. The mucosal cells of the cholesterol/fat fed animals accumulated varying amounts of lipid droplets, which were without an enveloping membrane, suggesting that the uptake of lipids from the intestinal lumen was higher than the capacity to synthesize and/or secrete lipoproteins. Simultaneously the size and amount of secondary lysosomes increased. A considerable increase in lipid droplets, lipolysosomes, and residual bodies was observed in the lamina propria macrophages while no crystalline clefts were seen.