Intake of herring oils containing cetoleic acid resulted in a lower serum cholesterol concentration in male obese Zucker fa/fa rats

A high serum total cholesterol (TC) concentration is a major risk factor for CVD, and lifestyle modifications including a healthy diet is among the first-line strategies for lowering cholesterol concentration and reducing CVD risk. Several studies in rodents have demonstrated a lower circulating TC concentration after intake of cetoleic acid (CA, C22:1n-11). The primary aim was to investigate the effect of consuming herring oil containing CA or a CA concentrate on the circulating TC concentration in obese hypercholesterolemic rats. Secondary aims included investigating effects of CA on a selection of hepatic enzymes and receptors involved in cholesterol metabolism, lipogenesis and VLDL assembly. Thirty male obese Zucker fa/fa rats were fed a diet containing either herring oil (HERO) or a CA concentrate (CECO), containing 0.70 or 1.40 wt% CA, respectively, or a control diet with soyabean oil for 5 weeks. Data were analysed using one-way ANOVA. The serum TC concentration was lower in the HERO and CECO groups compared to the Control group (17 and 20 percent, respectively). Both the HERO and the CECO diets downregulated de novo lipogenesis, cholesterol esterification and lipidation of VLDL in the liver compared to the Control diet, but did not affect the hepatic cholesterol synthesis, the LDL receptor or the faecal excretion of cholesterol and bile acids. To conclude, rats fed the HERO or CECO diets had a lower serum concentration of TC, probably as a result of downregulated VLDL-secretion in response to lower lipogenesis. This may have relevance for lowering TC in hypercholesteraemic humans.