title: Rice bran oil and oryzanol reduce plasma lipid and lipoprotein cholesterol concentrations and aortic cholesterol ester accumulation to a greater extent than ferulic acid in hypercholesterolemic hamsters.
abstract: Our laboratory has reported that the hypolipidemic effect of rice bran oil (RBO) is not entirely explained by its fatty acid composition. Because RBO has a greater content of the unsaponifiables, which also lower cholesterol compared to most vegetable oils, we wanted to know whether oryzanol or ferulic acid, two major unsaponifiables in RBO, has a greater cholesterol-lowering activity. Forty-eight F(1)B Golden Syrian hamsters (Mesocricetus auratus) (BioBreeders, Watertown, MA) were group housed (three per cage) in cages with bedding in an air-conditioned facility maintained on a 12-h light/dark cycle. The hamsters were fed a chow-based hypercholesterolemic diet (HCD) containing 10% coconut oil and 0.1% cholesterol for 2 weeks, at which time they were bled after an overnight fast (16 h) and segregated into 4 groups of 12 with similar plasma cholesterol concentrations. Group 1 (control) continued on the HCD, group 2 was fed the HCD containing 10% RBO in place of coconut oil, group 3 was fed the HCD plus 0.5% ferulic acid and group 4 was fed the HCD plus 0.5% oryzanol for an additional 10 weeks. After 10 weeks on the diets, plasma total cholesterol (TC) and non-high-density lipoprotein cholesterol (HDL-C) (very low- and low-density lipoprotein) concentrations were significantly lower in the RBO (-64% and -70%, respectively), the ferulic acid (-22% and -24%, respectively) and the oryzanol (-70% and -77%, respectively) diets compared to control. Plasma TC and non-HDL-C concentrations were also significantly lower in the RBO (-53% and -61%, respectively) and oryzanol (-61% and -70%, respectively) diets compared to the ferulic acid. Compared to control and ferulic acid, plasma HDL-C concentrations were significantly higher in the RBO (10% and 20%, respectively) and oryzanol (13% and 24%, respectively) diets. The ferulic acid diet had significantly lower plasma HDL-C concentrations compared to the control (-9%). The RBO and oryzanol diets were significantly lower for plasma triglyceride concentrations compared to the control (-53% and -65%, respectively) and ferulic acid (-47% and -60%, respectively) diets. Hamsters fed the control and ferulic acid diets had significantly higher plasma vitamin E concentrations compared to the RBO (201% and 161%, respectively) and oryzanol (548% and 462%, respectively) diets; the ferulic acid and oryzanol diets had significantly lower plasma lipid hydroperoxide levels than the control (-57% and -46%, respectively) diet. The oryzanol-fed hamsters excreted significantly more coprostenol and cholesterol in their feces than the ferulic acid (127% and 120%, respectively) diet. The control diet had significantly greater aortic TC and FC accumulation compared to the RBO (115% and 89%, respectively), ferulic acid (48% and 58%, respectively) and the oryzanol (74% and 70%, respectively) diets. However, only the RBO and oryzanol diets had significantly lower aortic cholesterol ester accumulation compared to the control (-73% and -46%, respectively) diet. The present study suggests that at equal dietary levels, oryzanol has a greater effect on lowering plasma non-HDL-C levels and raising plasma HDL-C than ferulic acid, possibly through a greater extent to increase fecal excretion of cholesterol and its metabolites. However, ferulic acid may have a greater antioxidant capacity via its ability to maintain serum vitamin E levels compared to RBO and oryzanol. Thus, both oryzanol and ferulic acid may exert similar antiatherogenic properties, but through different mechanisms.
authors.affiliation: Department of Clinical Laboratory and Nutritional Sciences, Center for Health and Disease Research, University of Massachusetts Lowell, Lowell, MA 01854, USA. thomas_wilson@uml.edu
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Wilson
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nicolosi
authors.forename: Benjamin
authors.initials: B
authors.lastname: Woolfrey
authors.forename: David
authors.initials: D
authors.lastname: Kritchevsky
mesh_terms: D000818:Animals; D000924:Anticholesteremic Agents / Q000008:administration & dosage; D001011:Aorta / Q000378:metabolism; D002784:Cholesterol / Q000097:blood; D002788:Cholesterol Esters / Q000378:metabolism*; D008076:Cholesterol, HDL / Q000097:blood; D003373:Coumaric Acids / Q000008:administration & dosage*; D006224:Cricetinae; D006937:Hypercholesterolemia / Q000097:blood / Q000188:drug therapy* / Q000378:metabolism; D000960:Hypolipidemic Agents / Q000008:administration & dosage; D008055:Lipids / Q000097:blood*; D008647:Mesocricetus; D010666:Phenylpropionates / Q000008:administration & dosage*; D010938:Plant Oils / Q000008:administration & dosage*; D000073879:Rice Bran Oil; D015430:Weight Gain; D024504:gamma-Tocopherol / Q000097:blood
chemical_list: D000924:Anticholesteremic Agents; D002788:Cholesterol Esters; D008076:Cholesterol, HDL; D003373:Coumaric Acids; D000960:Hypolipidemic Agents; D008055:Lipids; D010666:Phenylpropionates; D010938:Plant Oils; D024504:gamma-Tocopherol; D002784:Cholesterol; C004999:ferulic acid; D000073879:Rice Bran Oil; C013172:gamma-oryzanol