title: Corn fiber oil lowers plasma cholesterol by altering hepatic cholesterol metabolism and up-regulating LDL receptors in guinea pigs.
abstract: To evaluate some of the mechanisms involved in the hypocholesterolemic effects of corn fiber oil (CFO), male Hartley guinea pigs were fed diets containing increasing doses of CFO [0 (control), 5, 10 or 15 g/100 g]. Total fat was adjusted to 15 g/100 g in all diets with regular corn oil. Diets contained 0.25 g/100 g cholesterol. A positive control group (LC) with low dietary cholesterol (0.04 g/100 g) was also included. Plasma LDL cholesterol concentrations were 32, 55 and 57% (P < 0.0005) lower with increasing doses of CFO. Compared with controls, intake of CFO resulted in 27-32% lower hepatic microsomal cholesterol (P < 0.0001), the regulatory pool of LDL receptor (LDL-R) expression. CFO intake resulted in favorable plasma and hepatic cholesterol concentrations, similar to those in guinea pigs fed the LC diet. Hepatic cholesterol 7alpha-hydroxylase (CYP7) activity was approximately 88% higher in guinea pigs fed the two higher dosages of CFO (P < 0.05). In parallel, CYP7 mRNA abundance was approximately 88% higher in guinea pigs fed all three CFO diets. CFO treatment also induced hepatic LDLR mRNA by 66-150% with significant differences at the highest CFO dose. These results suggest that CFO, as a result of decreased bile acid absorption, increased mRNA abundance and activity of CYP7. Because hepatic cholesterol is the substrate for CYP7, a lowering of cholesterol concentrations in the total and microsomal pools was observed. As a response to the depleted microsomal free cholesterol pool, the LDL receptor was up-regulated, drawing more cholesterol from plasma, thus leading to the observed decrease in plasma LDL cholesterol concentrations.
authors.affiliation: Department of Nutritional Sciences, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Tripurasundari
authors.initials: T
authors.lastname: Ramjiganesh
authors.forename: Suheeta
authors.initials: S
authors.lastname: Roy
authors.forename: Hedley C
authors.initials: HC
authors.lastname: Freake
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: McIntyre
authors.forename: Maria Luz
authors.initials: ML
authors.lastname: Fernandez
mesh_terms: D000818:Animals; D001483:Base Sequence; D002784:Cholesterol / Q000097:blood* / Q000378:metabolism*; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D002791:Cholesterol, Dietary / Q000008:administration & dosage; D008078:Cholesterol, LDL / Q000097:blood; D003314:Corn Oil / Q000494:pharmacology*; D018076:DNA, Complementary / Q000737:chemistry; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology*; D006168:Guinea Pigs; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011973:Receptors, LDL / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology
chemical_list: D002791:Cholesterol, Dietary; D008078:Cholesterol, LDL; D018076:DNA, Complementary; D004042:Dietary Fats, Unsaturated; D012333:RNA, Messenger; D011973:Receptors, LDL; D003314:Corn Oil; D002784:Cholesterol; D002790:Cholesterol 7-alpha-Hydroxylase