Ability of crude lipid, wax, and oil fractions extracted from red grain sorghum whole kernel to prevent high cholesterol caused by high-fat diets in a hamster model

The lipid fractions extracted from mixed (white and non-containing tannin red) and white grain sorghum (GS) whole kernel (WK) have been shown to possess cholesterol-lowering properties. As other varieties of GS-WK differ in their lipid composition, three studies were conducted to examine the effects of crude lipid (CL), wax, and oil fractions extracted from red GS-WK containing tannins on cholesterol metabolism by using a hamster model. In each study, hamsters were randomly divided into five groups (n=11) each fed either a low fat AIN-93M diet (control), a AIN-93M diet with 10 percent fat and 0.2 percent cholesterol (atherogenic) or an atherogenic diet supplemented with 1.0, 3.0, or 5.0 percent (w/w) red GS-WK lipid fractions for four weeks. The addition of CL, wax and oil into atherogenic diets significantly lowered plasma non-high density lipoprotein cholesterol (non-HDL) and triacylglycerols. Hepatic cholesterol levels were also significantly reduced in response to CL and oil supplemented diets, but were not altered by the wax fraction. Analysis of fecal samples revealed a significant increase in cholesterol excretion in response to all the lipid-supplemented diets, suggesting that these fractions lower non-HDL cholesterol, in part, by preventing cholesterol absorption. However, analysis of several genes involved in cholesterol metabolism indicated that each fraction could also affect other pathways. The CL and oil fraction significantly upregulated the gene expression of hepatic bile acid synthesis, but the CL was also able to upregulate LDL receptors, whereas endogenous cholesterol synthesis was inhibited in the animals fed the wax-based diets. These results indicate that the all the lipid fractions extracted from red GS-WK not only reduced cholesterol absorption, but also regulated different pathways involved in cholesterol metabolism. Although phytosterols present in CL and oil have been purported to be the primary dietary lipids responsible for lowering cholesterol absorption, our results demonstrated that the policosanols present in the wax fraction induced a similar mechanism of action. Policosanols present in wax fraction are most likely to be suppressing cholesterol synthesis. However, other compounds, namely tannins, present in red GS-WK lipid fractions are probably acting additively/synergistically to remediate cholesterol markers induced by an atherogenic diet