Increased binding of LDL and VLDL toapo B,E receptors of hepatic plasma membrane of rats treatedwith Fibernat

Summary. Background: Research has focussed on the hypocholesterolemic effectsof certain types of dietary fiber such as enhancing conversionof hepatic cholesterol to bile acids or increase in catabolismof low density lipoprotein (LDL) via the apo B,Ereceptor. Aim of thestudy: The effect of oral administration of a unique fibrecocktail of fenugreek seed powder, guar gum and wheat bran(Fibernat) and its varied effects on some aspects of lipidmetabolism and cholesterol homeostasis in rats wereexamined. Methods: Rats were administered Fibernat along with the atherogenicdiet containing 1.5 % cholesterol and 0.1 % cholic acid. Amountsof hepatic lipids, hepatic and fecal bile acids and activity ofhepatic triglyceride lipase (HTGL) were determined. Transmissionelectron microscopic examination of the liver tissue and extentof uptake of ¹²⁵I-LDL and ¹²⁵I-VLDL by the hepatic apo B,Ereceptor was carried out. Results: Food intake and body weight gain were similar between the3 different dietary groups. Fibernat intake significantlyincreased apo B,E receptor expression in rat liver as reflectedby an increase in the maximum binding capacity(B_max) of the apo B,E receptor to ¹²⁵I-LDL and ¹²⁵I-VLDL. The activity of HTGL wasincreased by approximately 1.5-fold in Fibernat-fed rats ascompared to those fed the atherogenic diet alone. A markedhypocholesterolemic effect was observed. Cholesterol homeostasiswas achieved in Fibernat-fed rats. Conclusion: Two possible mechanisms are postulated to be responsiblefor the observed hypocholesterolemic effect a) an increase inconversion of cholesterol to bile acids and b) possibly byintra-luminal binding which resulted in increased fecalexcretion of bile acids and neutral sterols. The resultingreduction in cholesterol content of liver cells coupled withupregulation of hepatic apo B,E receptors and increasedclearance of circulating atherogenic lipoproteins—LDL and verylow density lipoprotein (LDL and VLDL)—is the main mechanisminvolved in the hypocholesterolemic effect of Fibernat. Theresults suggest that Fibernats effect on plasma LDLconcentration is also possibly mediated by increasedreceptor-mediated catabolism of VLDL. Thus, Fibernat therapy isan effective adjunct to diet therapy and might find potentialuse in the therapy of hyperlipidemic subjects.