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

摘要

This study sought to determine whether water-insoluble fish protein (IFP) from Alaska pollock (Theragra chalcogramma) prevents hypercholesterolaemia induced by ovarian hormone deficiency. Wistar female rats, aged 6 months, were subjected to sham-operation or ovariectomy, and fed a cholesterol-free diet containing casein or IPF as a protein source for 28 days. Body-wt. gain and food intake increased in the ovariectomized rats as compared with the sham-operated rats. Plasma total cholesterol concn. was decreased and faecal bile acid excretion was increased by IFP in the ovariectomized rats, but not in the sham-operated rats. Plasma homocysteine concn. was decreased by IFP in the ovariectomized rats, but not in the sham-operated rats. Liver lipids and liver cholesterol concn. were increased and cholesterol 7 alpha-hydroxylase (CYP7A1) activity was decreased by ovariectomy, but not by diet. Bile acid content and the ratio of cholic acid groups to chenodeoxycholic acid groups in bile were increased by ovariectomy, but decreased by IFP. Bile acid content in the small intestine was increased by IFP in the ovariectomized rats, but not in the sham-operated rats. 3-Hydroxy-3-methylglutaryl-CoA reductase and microsomal TAG transfer protein mRNA levels were decreased by ovariectomy and IFP, whereas LDL-receptor mRNA level was decreased by ovariectomy but unaffected by diet. Thus, the preventive effect of IFP on the ovarian hormone deficiency-associated increase in plasma cholesterol concn. seems to be mediated by accelerated faecal excretion of bile acids, coupled with an increase in the intestinal pool of bile acids.