Corn fiber oil lowers plasma cholesterol by altering hepatic cholesterol metabolism and up-regulating LDL receptors in guinea pigs.
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.
Ramjiganesh
Tripurasundari
T
Department of Nutritional Sciences, University of Connecticut, Storrs, CT 06269, USA.
Roy
Suheeta
S
Freake
Hedley C
HC
McIntyre
Jonathan C
JC
Fernandez
Maria Luz
ML
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
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