The Hypolipidemic Effects And Mechanism Of Lactobacillus Brevis Fermented Kelp In High-fat Diet Rats

In this study,kelp(Laminaria japonica)was used as raw material,and Lactobacillus brevis used to ferment kelp was selected from a variety of lactic acid bacteria,Hypolipidemic effect of the fermented kelp was investigated by establishing a model of High-fat diet-induced hyperlipidemia rats.Furthermore,the mechanism of fermented kelp regulating lipid metabolism was explored.The main research contents and results were listed as follows:1?The process optimization of Lactobacillus brevis fermented kelp was studied.Lactobacillus brevis was used as the strain of fermented kelp and the number of live bacteria was used as an index to evaluate fermentation effects.The single-factor experiment was carried out in terms of the concentration of kelp,lactic acid bacteria inoculum size and fermentation time.The result showed the optimal fermentation conditions was determined as follows:kelp concentration of 3.3%,lactic acid bacteria inoculation size of 4.6%,and fermentation time of 25.7 h.The number of live bacteria in the fermentation supernatant of kelp was over10~8CFU/m L under the optimal fermentation condition.Compared with unfermented kelp,the soluble sugar in the kelp fermentation was reduced by 28%.The results showed that Lactobacillus brevis can use the soluble sugar in the kelp during the fermentation process.2?Effect of fermented kelp with Lactobacillus brevis on lowering lipids level in vivo was studied by establishing the model of High-fat diet-induced hyperlipidemia rats.It was found that the intervention of fermented kelp with Lactobacillus brevis can significantly decrease the liver index and fat index(P<0.05),significantly reduce the levels of total cholesterol(TC)and triglyceride(TG)on serum and liver of high-fat diet rats(P<0.05),increase the level of hepatic total bile acid(TBA)(P<0.05)and increase the level of hepatic oxidative stress.At the same time,according to testing the total fat content of the liver,the results showed that the intervention of fermented kelp significantly reduced the total fat content in the liver,and liver histological examination also confirmed the intervention of fermented kelp can decrease liver fat accumulation in high-fat diet rats.In addition,the results showed that the intervention of fermented kelp significantly increased the levels of TC,TG and TBA on the feces(P<0.05)and significantly increased the content of acetic acid,propionic acid and n-butyric acid in the intestine(P<0.05).These results suggested that Lactobacillus brevis fermented kelp could decrease blood lipid absorption or promote lipid excretion,which had a certain improvement effect on high-fat diet rats induced by a high-fat diet.3?The potential hypolipidemic mechanism of Lactobacillus brevis fermentation kelp was investigated by measuring the lipid metabolism related gene expression and intestinal microorganism of hyperlipidemia rat.The results showed that the intervention of fermented kelp changed the expression of genes related to lipid metabolism in high-fat diet rats,and sharply down-regulated the expression level of HMGCR,ACAT2 and SREBP-1C genes in the liver(P<0.01),which was beneficial to inhibit hepatic cholesterol synthesis.The intervention of fermented kelp also promoted hepatic CYP7A1 gene expression,which increased cholesterol metabolism and reduced lipid accumulation in the liver.From the analysis of intestinal microbial abundance,the intervention of fermented kelp significantly improved the disturbance of intestinal flora in rats caused by a high-fat diet,and restored the intestinal microbial abundance and Alpha-diversity in high-fat diet rats.Moreover,the abundance of the Firmicutes(Lactobacillaceae,Ruminococcaceae,Lachnospiraceae,and Clostridiaceae)had been improved by the treatment of fermented kelp.In addition,the analysis of the correlation between intestinal flora and lipid metabolism parameters found that The body weight,the serum HDL,the hepatic TC,TG and fat and fecal TBA showed positive correlations with Akkermansia.The intervention of fermented kelp not only significantly reduced the expression of genes related to lipid metabolism,increased cholesterol metabolism in the liver,but also increased the relative abundance of Lactobacillaceae and Akkermansia in the intestine.In summary,this article systematically studied the optimal conditions of Lactobacillus brevis fermentation kelp,and the effects of fermented kelp on blood lipids in high-fat diet rats.Finally,the potential mechanism of lipid-lowering on Lactobacillus brevis fermented kelp was analyzed from levels of gene expression and intestinal flora.The research results provide a theoretical basis for the development of kelp functional food.