SummaryThe effect of dietary safflower phospholipid (Saf-PL) and soybean phospholipid (Soy-PL) on plasma, liver, and fecal lipids in rats fed a hypercholesterolemic diet was compared with that of triglyceride mixture (controls). Triglyceride mixture (SP-Oil) of safflower oil and palm oil (8:2) contained almost comparable amounts of linoleic acid to safflower phospholipid or soybean phospholipid. Concentration of total cholesterol in plasma of rats fed the Saf PL and Soy-PL diets were significantly decreased in comparison with that of the SP-Oil diet. Simi larly, both Saf PL and Soy-PL induced a reduction in the concentration of liver cholesterol compared with SP-Oil; Saf PL indicated the lowest value. Saf PL only significantly increased the level of high density lipoprotein (HDL) cholesterol. The level of chylomicron plus very low density lipoprotein (VLDL) cholesterol was lower in rats fed the Saf-PL and Soy-PL diets than that of the SP-Oil diet. The activity of plasma lecithin-cholesterol acyltransferase (LCAT) was increased in rats fed Saf-PL and Soy-PL. Saf PL and Soy-PL caused an enhanced excretion of fecal neutral steroids, but not acidic steroids compared with SP-Oil. These results suggest that, in addition to soybean phospholipid, safflower phospholipid suppresses the elevation of plasma and liver cholesterol and that this effect may be brought about by inhibiting the absorption of cholesterol in the small intestine.

The effects of guar gum and cholestyramine on cholesterol metabolism were studied in meal-fed male Wistar adult rats maintained on a cholesterol-enriched or cholesterol-free purified diet for 2 weeks. At 3.5h after the last meal, blood was withdrawn by cardiac puncture, and then plasma and plasma lipoprotein-lipids, and liver cholesterol were determined. The results obtained were as follows: 1) In the cholesterol-fed rats, guar gum and cholestyramine suppressed the increase of plasma and liver cholesterol, and the decrease of HDL-cholesterol due to cholesterol intake. 2) In the rats fed the cholesterol-free diet, cholestyramine decreased chylomicron+VLDL-cholesterol, but did not alter the level of plasma cholesterol. 3) Guar gum decreased chylomicron+VLDL-, HDL-and plasma cholesterol in rats fed the cholesterol-free diet. These results demonstrate that the mechanism whereby guar gum lowers the plasma cholesterol level cannot be fully explained by interference with absorption of bile acid and cholesterol, which is the mode of action of cholestyramine.

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The effects of dietary fiber on plasma cholesterol, the level of steroid in intestinal contents and feces, and short-chain fatty acid (SCFA) in cecum and feces were studied in 8-week-old male Wistar rats. The rats were fed a cholesterol-free diet containing 5% dietary fiber (cellulose, bacterial cellulose, apple pulp, gum arabic, guar gum, guar gum hydrolysate) with meals provided twice daily for 2 weeks. At 3.5h after the last meal, the animals were sacrificed.Only guar gum significantly decreased the level of plasma cholesterol and increased fecal bile acid and total steroid excretion.However, there was no relationship between the plasma cholesterol concentration and fecal total steroid or bile acid excretion, when data obtained from all rats were combined.Plasma cholesterol concentration was negatively correlated with bile acid content in the upper small intestine.In rats except those in the guar gum hydrolysate group, there was a negative relationship between plasma cholesterol concentration and SCFA content, especially propionate, in the cecum. These results demonstrate that fecal steroid excretion, bile acid secretion and propionate production in the cecum may be involved in the mechanism responsible for the plasma cholesterol-lowering effects of dietary fiber.Key Words dietary fiber, plasma cholesterol, short chain fatty acid, fecal steroid.

The effect of dietary safflower phospholipid (Saf-PL) on the postprandial changes of steroids in the small intestinal and cecal contents was examined in rats fed a hypercholesterolemic diet. The triglyceride mixture (SP-Oil) containing a comparable amount of linoleic acid to Saf-PL was used as a reference fat source. Saf-PL suppressed the elevation of plasma cholesterol levels at all times after meal intake , when compared to SPOil. The reduction of plasma cholesterol in rats fed the Saf-PL diet was exclusively observed both in chylomicron plus very low density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions. The rate of gastric emptying was not modified by the Saf-PL diet. The level of neutral steroids in the small intestinal contents was almost comparable in both groups, but in the cecal contents and feces it was significantly higher in rats fed the Saf-PL diet. On the other hand , the level of acidic steroids in the small intestinal contents tended to be higher in rats fed the Saf-PL diet than in those fed the SPOil diet , whereas in the cecal contents and feces it was comparable in the two diets. These results suggest that Saf-PL causes the accumulation of neutral steroids in the cecum due to the rapid transit through the samll intestine .