Lime-treated corn husks lower plasma LDL cholesterol in guinea pigs by altering hepatic cholesterol metabolism

Lime-treated corn husks (LTCH) containing 69% of fiber (5.0% as soluble fiber) were evaluated on their hypolipidemic properties in guinea pigs. Animals were fed two doses of corn husks replacing dietary fiber: 7.5% and 10% (w/w) and LTCH effects on hepatic cholesterol metabolism and lipoprotein levels were compared to a central diet containing cellulose. LTCH significantly lowered plasma LDL cholesterol by 25% (P < 0.01) and VLDL cholesterol by 37% (P < 0.05), although a dose effect was not observed in this parameter. Plasma triacylglycerol (TAG) concentrations and HDL cholesterol levels were not affected by LTCH intake. The number of cholesteryl ester, TAG and phospholipid molecules were lower in VLDL from animals fed LTCH diets compared to control (P < 0.01) indicating modifications on VLDL size that were confirmed by the smaller calculated VLDL diameter of guinea pigs treated with LTCH. In addition, LTCH intake resulted in a smaller, cholesteryl ester depleted LDL particle compared with LDL derived from control animals. Hepatic cholesterol and TAG were not affected by LTCH, however microsomal-free cholesterol was lower in animals fed LTCH compared with control. In agreenment with the observed reductions on microsomal cholesterol, HMG-CoA reductase activity was upregulated 87% and 100%, ACAT downregulated 54% and 65% and cholesterol 7α-hydroxylase activity upregulated 120% and 180% by LTCH diets in a dose dependent manner (P < 0.01). In addition, LDL building to hepatic membranes (B(max)) was higher in animals fed LTCH diets. These results indicate that the lower plasma VLDL and LDL cholesterol concentrations induced by LTCH intake are associated with decreases in microsomal cholesterol that alter the regulatory enzymes of cholesterol homeostasis and upregulate LDL receptors.