Effects And Mechanism Of Anthocyanins And Black Rice On Cholesterol Absorption

Hypercholesterolemia, a lipid metabolic disorder, is an important factor of cardiovascular disease. The first strategy of treating hypercholesterolemia is regarded as lowing the total cholesterol (TC). Cholesterol absorption plays an important role in maintaining blood lipid homeostasis. Black rice (Oryza sativa L.) and anthocyanins are often associated with lipid control. But none of existing studies has investigated the effects of black rice on cholesterol absorption. Thus, in this study, we will investigate the effects and mechanism of black rice on cholesterol absorption and prove that this action can be attributed to anthocyanins in this rice.Firstly, different black rice extracts (BRE), which were aqueous (EH2o ethanol extracts and a fraction of macroporous resin (EEnr), were prepared. During the preparation of, we optimized extraction traditions to obtain EEtoH-Also, the best macroporous resin was screened and it was used to get a fraction of marcropous resin. After the preparation of BRE, the content of anthocyanins in them was determined by HPLC and the contents of anthocyanins were in the following order:EEnr>EEtoH>EH2o.Secondly, the models of pancreatic lipase, bile acid micelles and Caco-2cells were established, respectively to investigate the effects of BRE on the activity of lipase, cholesterol solubility and cholesterol uptake, which were all associated with cholesterol absorption. Our results indicated that BRE inhibited cholesterol absorption and the degree was positively relevant to the content of anthocyanins in them. Thus, it is hypothesized that anthocyanins contribute to the actions of BRE.Lastly, the cholesterol absorption inhibiting properties of anthocyanins, which were Cyanidin-3-glucoside (Cy-3-G) and Peonidin-3-glucoside (Pn-3-G), were further investigated by the models established above. The IC50values of Cy-3-G and Pn-3-G against pancreatic lipase were42.43±4.45and18.13±4.22μg/mL, respectively. Kinetic analysis suggested that the enzymatic inhibitory mode of Cy-3-G and Pn-3-G belonged to the competitive type. In mixed micelles, Cy-3-G and Pn-3-G dose dependently reduced the solubility of cholesterol. Meanwhile, a potential mechanism of cholesterol reduction by anthocyanins was investigated. Results showed that anthocyanins led to precipitation of cholesterol from micellar solution, which may induce the reduction of cholesterol. In Caco-2cells, Cy-3-G and Pn-3-G (40μg/mL) exhibited a significant reduction in cholesterol uptake, and the degree of this reduction was almost the same as that observed in the group treated with Ezetimibe at the same concentration.In conclusion, these findings provide important evidence that anthocyanins may partly contribute to the inhibitory effects of black rice on cholesterol absorption, and thus may be applied for the prevention of hypercholesterolaemia.