Effects And Molecular Mechanisms Of Black Brown Rice Pericarps On Lipid Metabolism In Rats

The Hyperlipidemia(HLP)is a kind of lipid metabolic disorder. The treatment of the HLP has become a hot global issue because of its harmfuless and chronic complications plus high treatment cost. The HLP is related to gene defect, dietetic irrationality and endocrine dyscrasia, but its cause and pathogenesy remain largely unknown. The abnormal lipid metabolism is considered to be one of the important pathogenesy. The regulation of lipid metabolic abnormalities has become an important link in prevention and treatment of HLP and its chronic complications.Hypolipidemic drugs work faster and effective, but they are expensive and have toxicity side effects. Chinese herbal medicines have advantages of multiple channels, links and targets, but it cannot be used for long-term period. Functional foods possess the advantages of Chinese herbal medicine and can be long-term used without toxicity side effects, which has demonstrated the unique advantages in the prevention and treatment of some metabolic disease. Many scholars have made some achievements in improving lipid metabolism of HLP. However, the mechanism remains poorly understood and needs further investigation.In this study, we used two rice varieties, the black brown rice variety "Fuzi681" with high anthocyanin and black pericarp, red rice variety "Fuhong819" with red pericarp, and three mushroom varieties, Russula, mythic fungus, and veiled lady to compare the effect of these five agricultural products on blood lipid levels in high-fat diet rats. From these five agricultural products, we had screened one for lowering blood lipid level significantly. Then we observed its effects on lipid metabolism, oxidative stress, organ and vessels lesions in hypolipidemic rats.We also investigated the molecular mechanism of hyperlipidemia from the aspects of lipid absorption, synthesis, transformation and regulation. Our research will provide a scientific basis for treatment of metabolic disorders in HLP. The main results are as follows:1Effects of5kinds of agricultural products on the blood lipids level of rats fed with high fat dietThe model of rat HLP is established by long-term high-fat diet. The animals with yellow fur, weight gained fast, lacking physical activity and increased serum TC and TG are fit for clinical characteristics of HLP. Using simvastatin as positive control, we fed HLP rats with black brown rice pericarp (BBRP), red brown rice pericarp (RBRP), Russula, mythic fungus and veiled lady for8weeks to observe the changes of body weight, the level of serum TC, TG in hyperlipidemic rats.The results show that:(l)From the first to seventh week, the weight gain of HLP rats fed with simvastatin, BBRP, RBRP, Russula, mythic fungus, and veiled lady increased gradually, but the growth rate has slowed down compared with the model group. From seventh to eighth week, only the body weight of rats fed with BBRP decreased, but the body weight of rats fed with others continued to increase. After eight weeks, the body weight gain of rats fed with simvastatin, BBRP, RBRP, Russula, mythic fungus, and veiled lady decreased by26.26%,33.16%,39.40%,34.97%,32.15%and6.19%respectively. This indicates that the mentioned above five agricultural products can reduce the weight of rats fed with high fat diet, and the effect of BBRP on weight control is significant.(2) The level of serum TC and TG in HLP rat was reduced by simvastatin, BBRP, Russula, mythic fungus and veiled lady, with the TC ratio18.97%,17.82%,35.06%,27.41%,36.78%respectively and the TG ratio52%,57.33%,8%,10.06%,54.67%respectively. However, serum TC and TG in HLP rat was increased by RBRP with the ratio12.07%and18.67%respectively. Therefore, we chose BBRP to the following experiments.2Effects of BBRP on lipid metabolism in rats fed with high lipid dietUsing the simvastatin as positive control, we fed the HLP model rats with0.09or0.045g/mL dose of BBRP suspension20mL/kg for8weeks to observe the effect on change of weight, blood lipid, apolipoprotein, oxidative stress, the level of FFA and fecal lipid. The results show that:(1) The body weight gain of rats was significantly inhibited and positively correlated with dosage. The body weight gain was reduced by33.16%and24%in high and low dose group, compared to the model group.(2) The level of serum TC, TG, AI, ApoB was significantly decreased, and the level of HDL-C and ApoAI was increased by high or low dosage of black rice pericarp, which was positively correlated with dosage. The level of TC was decreased by17.82%and19.54%. The level of TG was decreased by57.33%and17.33%. The AI value was decreased by39.81%and23.65%. The level of ApoB was decreased by30.83%and30.83%. The level of HDL-C was increased by24.24%and3.03%. The level of ApoAI was increased by68.42%and73.68%.(3) The level of serum MDA was significantly decreased and the activity of SOD, CAT, GSH-Px was increased by high or low dosage of black rice pericarp. Compared to those in the model group, the level of serum MDA was decreased by33.24%and28.92%. The activity of SOD was increased by28.60%and32.46%, with no significant differences to normal group. Tthe activity of CAT was increased by101.16%and97.69%, closely to normal group. The activity of GSH-Px was increased by32.46%and28.60%, significantly higher than that of normal group.(4) The level of serum FFA and TC in feces was significantly decreased by high or low dose of BBRP, but the level of TG in fecal was increased. The level of FFA was slightly higher than that of normal group, and was decreased by31.54%and39.08%respectively compared to the model group. The level of TC in feces was decreased by36.75%and53.23%respectively, the level of TG in fecal was increased by20.37%and5.56%, compared to the model group.3Protective effects of BBRP on the organs and tissues of rats fed with high fat dietUsing the simvastatin as positive control, we fed the HLP model rats with0.09or0.045g/mL dose of BBRP suspension20mL/kg for8weeks to observe the effects of BBRP on liver morphology and weight, fat weight, liver enzymes, the fatty lesions of liver, aorta and heart. The results show that:(1) The liver and fat index was significantly decreased by BBRP. After the rats were fed with BBRP for8weeks, the liver index were decreased by12.26%or10.63%, and the fat index were decreased by35.71%and24.29%, respectively, in high or low dosage group compared to model group.(2) The levels of liver TC or TG was significantly decreased and the activity of serum ALT or AST was significantly reduced by BBRP. In the liver of rats fed with high or low dosage BBRP, the level of TC was decreased by59.74%and50.80%; TG decreased by40.63%and20.31%; the activity of ALT decreased by64.50%and35.41%; the activity of AST decreased by41.79%and23.10%.(3) The fatty lesions of liver and aorta can be greatly improved by BBRP, which is positively correlated to dosage. The morphology of liver and aortic in high dose group is close to that of normal group. There are mild fatty lesions in the liver with and no fatty lesions in the aorta in low dose group. However, the fatty lesions were formed both in the liver and aorta of rats in model group.4Study on the molecular mechanism of improving lipid metabolism of BBRP in rats fed with high fat dietIn order to test the effects of BBRP on the mRNA level of FAS, LCAT, HMG-CoA reductase, CYP7A1and PPARa in rat liver tissue, we performed reverse transcription-PCR (RT-PCR) analysis to show that the mRNA level of PPARa and CYP7A1were significantly up-regulated and the mRNA level of HMG-CoA reductase was significantly down-regulated, the mRNA level of LACT showed an increased tendency and the mRNA level of FAS showed a decreased tendency after BBRP treatment for8weeks.(2) Our results showed that the protein level of LACT showed an increased tendency and the protein level of FAS showed a decreased tendency after BBRP treatment for8weeks through immunohistochemistry.(3) With the method of Western blot, we detected the expression level of HMG-CoA reductase, CYP7A1and PPAR a protein in rat liver. Our results showed that the protein level of PPARa and CYP7A1were significantly up-regulated and the protein level of HMG-CoA reductase was significantly, down-regulated in rat liver after BBRP treatment. This indicated that the expression of HMG-CoA reductase might be inhibited and the expression of PPARa might be induced by BBRP, which stimulated the CYP7A1promoter causing the up-regulation of CYP7A1. As a result, the lipid metabolism was improved and the blood lipid was reduced.