Effects of Rice Bran Protein on Lipid Metabolism and Its Mechanism in Rats

This study investigated the effects of rice bran protein on lipid metabolism and its mechanism in rats fed with high-cholesterol diet. The experiment designed 4 groups including casein group (CAS, control), rice bran protein group(RBP), brown rice protein group (BRP) and rice protein group(WRP). The rats were fed with high-cholesterol diet supplemented with 20% casein, 15% casein+5% rice bran protein, 15% casein+5% brown rice protein and 15% casein+5% rice protein for 3 weeks. The levels of total cholesterol (TC) and contents of triglyceride (TG) in serum, and TC, TG and total lipid in liver of rats were measured. The feces were collected for 3 days before the animals were sacrificed, and the excretion of total bile acids and neutral sterols were determined. The micellar solubility of cholesterol with CAS, RBP, BRP and WRP, and the abilities of different concentrations CAS and RBP to bind with bile acid were determined by simulating human gastrointestinal environment in vitro. The results showed that compared with casein and other protein groups, rice bran protein significantly reduced serum TC (P<0.05) and atherosclerotic index (P<0.05); liver TC level was significantly reduced (P<0.05) and the total bile acid excretion in feces was significantly increased (P<0.05). The in vitro experiments showed that rice bran protein could bound to bile acids and significantly inhibited the solubility of cholesterol micelles (P<0.05). To sum up, rice bran protein bound to bile acids in vivo to inhibit its absorption in the intestines and increase its excretion in feces, and finally achieved the effects of reducing serum lipids.