Dietary Karaya Saponin andRhodobacter capsulatusExert Hypocholesterolemic Effects by Suppression of Hepatic Cholesterol Synthesis and Promotion of Bile Acid Synthesis in Laying Hens

Abstract

This study was conducted to elucidate the mechanism underlying the hypolipidemic action of karaya saponin orRhodobacter (R.) capsulatus. A total of 40 laying hens (20-week-old) were assigned into four dietary treatment groups and fed a basal diet (as a control) or basal diets supplemented with either karaya saponin,R. capsulatus, or both for 60 days. The level of serum low-density-lipoprotein cholesterol and the levels of cholesterol and triglycerides in the serum, liver, and egg yolk were reduced by all the supplementations (). Liver bile acid concentration and fecal concentrations of cholesterol, triacylglycerol, and bile acid were simultaneously increased by the supplementation of karaya saponin,R. capsulatus, and the combination of karaya saponin andR. capsulatus(). The supplementation of karaya saponin,R. capsulatus, and the combination of karaya saponin andR. capsulatussuppressed the incorporation of from -palmitic acid into the fractions of total lipids, phospholipids, triacylglycerol, and cholesterol in the liver in vitro (). These findings suggest that the hypocholesterolemic effects of karaya saponin andR. capsulatusare caused by the suppression of the cholesterol synthesis and the promotion of cholesterol catabolism in the liver.