Evaluation of the Effects of Plant Trypsin Inhibitors on Lipoprotein Binding and Metabolism

Dyslipidemia is an important risk factor in many chronic diseases, like diabetes, hypertension, non-alcoholic fatty liver disease, metabolic syndrome, atherosclerosis for examples. Despite many drugs had been approved for the treatment of dyslipidemia, people are still searching for new substances or new therapeutic targets to make critical controls on blood lipid profiles to lower down the risk of cardiovascular events. In our preliminary results, we found that some plant trypsin inhibitors (TIs) (commercial soybean Kuntiz-type TIs, sweet potato sporamins, and madeira vine rhizome TIs) might have abilities on binding with native/oxidative low-density lipoprotein (LDL), protecting native LDL against copper-induced oxidation, interfering LDL uptake by hepatocytes and eliminating the LDL receptor (LDLR) degradation effect of proprotein convertase subtilisin/kexin type 9 (PCSK9) on HepG2 cell. Therefore, a three-year project is proposed, in the 1st year, we will screen for plant trypsin inhibitors by LDL binding ability and the activities of LDL uptake interfering, LDL receptor expression and protection against PCSK9-mediated LDLR degradation on HepG2 cells which two out of three with higher potentials of above-mentioned will be purified to high amounts for further animal experiments and characterized. In the 2nd year, because the lipoprotein metabolism is a highly complex system, the atherogenic diet-induced guinea pig dyslipidemia animal model will be performed and the potential of lipid profile modulation, anti-NAFLD and anti-atherosclerosis by the two plant trypsin inhibitors will be evaluation in vivo. In the last year, we will try to get the bioactive fragments of plant trypsin inhibitors. Then the bioactivities on hepatocyte, enterocyte and macrophage will be evaluated, including the cytotoxicity, LDL uptake, LDLR expression, PCSK9 expression, cholesterol absorption, etc. In this proposal, the in vitro experiments will give us the basic knowledge if/what plant trypsin inhibitors will have the chance to interact with LDL, the model of interactions and the biological functions/targets of the binding complex. And the animal experiment will make people know that if the plant trypsin inhibitors would potential substances to be developed as functional foods or therapeutic agents for dyslipidemia support or treatment.