The mechanism of the cholesterol-lowering effect of water-insoluble fish protein in ovariectomised rats

摘要

The purpose of the present study was to investigate whether water-insoluble fish protein (IFP) from Alaska pollock (Theragra chalcogramma)nprevents hypercholesterolaemia induced by ovarian hormone deficiency. Wistar female rats, aged 6 months, were subjected to sham-operationnor ovariectomy, and fed a cholesterol-free diet containing casein or IPF as a protein source for 28 d. Body-weight gain and food intake increasednin the ovariectomised rats as compared with the sham-operated rats. Plasma total cholesterol concentration was decreased and faecal bile acidnexcretion was increased by IFP in the ovariectomised rats, but not in the sham-operated rats. Plasma homocysteine concentration was decreasednby IFP in the ovariectomised rats, but not in the sham-operated rats. Liver lipids and liver cholesterol concentrations were increased and cholesteroln7a-hydroxylase (CYP7A1) activity was decreased by ovariectomy, but not by diet. Bile acid content and the ratio of cholic acid groups to chenodeoxycholicnacid groups in bile were increased by ovariectomy, but decreased by IFP. Bile acid content in the small intestine was increased bynIFP in the ovariectomised rats, but not in the sham-operated rats. 3-Hydroxy-3-methylglutaryl-CoA reductase and microsomal TAG transfer proteinnmRNA levels were decreased by ovariectomy and IFP, whereas LDL-receptor mRNA level was decreased by ovariectomy but unaffected byndiet. Thus, the preventive effect of IFP on the ovarian hormone deficiency-associated increase in plasma cholesterol concentration seems to benmediated by accelerated faecal excretion of bile acids, coupled with an increase in the intestinal pool of bile acids.