Effect Of Fucoidan On Prevention Of Diet-induced Obesity-related Hyperlipidemia And Modulation Gut Microbiota In ICR Mice

Objectives:(1)The present study firstly investigated the effect of fucoidan from U.pinnatifida on the cholesterol-lowering ability and bile salt hydrolase(BSH)activity of Enterococcus faecium(E.faecium)R0026 in vitro.(2)The preventive effects of fucoidan on diet-induced obesity-related hyperlipidaemia in ICR mice and regulation of gut microbiota,were further clarified through animal experiments.Methods:(1)The strains were activated,inoculated in different carbon source media and bacteria were counted at different time points on plates to calculate CFU values.(2)Activated E.faecium R0026 was inoculated into cholesterol media with different carbon sources and cholesterol levels in the fermentation broth were measured.(3)E.faecium R0026 grown in different media was incubated for 12 hours and the BSH enzyme activity was assayed in vitro by an enzymatic reaction.(4)Forty 4-week-old male ICR mice were acclimatized and fed for one week,randomly divided into 4 groups(10 mice per group),normal group(NFD)fed normal chow;model group(HFD),fucoidan low dose group(Fuc0.5)and fucoidan high dose group(Fuc2.5)fed high-fat diet for 5 weeks of intervention.Fucoidan(50 mg/kg/day and 250 mg/kg/day)was dissolved in saline and the normal and model groups were gavaged with 0.2 m L of saline.In the fucoidan groups,0.2 m L of fucoidan solution was gavaged.All animals were allowed to eat and drink freely during the experiment.The amount of food was recorded daily and the mice were weighed every week after fasting and fasting blood glucose was measured every fortnight in the tail vein.(5)At the end of the experiment the body length(distance from nose to anus)of the mice was measured and the liver,epididymal fat and brown adipose tissue were collected and weighed.(6)Serum TC,TG,HDL-C,LDL-C were measured using kits.Serum LPS,TBA and TNF-α levels were measured using ELISA kits.(7)Mouse liver and small intestine segments were collected,stained for hematoxylin and eosin(HE)and photographed under a light microscope at 100 x.(8)The contents of the cecum of mice were collected and the composition of the gut microbiota was analysed using deformation gradient gel electrophoresis(PCR-DGGE)technique and 16 S r RNA gene sequencing.Real-time fluorescence quantitative PCR(q PCR)technique was used to quantify the dominant bacteria of the gut.(9)Correlation of blood lipid and inflammation levels with characteristic gut microbiota in mice using Speaeman.Results:(1)E.faecium R0026 had significantly higher CFU in media containing fucoidan than in media without fucoidan.E.faecium R0026 showed a cholesterol removal rate of60.18% in media containing 1% fucoidan,77.78% in media containing 2% fucoidan,58.35% in media containing glucose and 45.20% in media without fucoidan and glucose.The number of viable bacteria of E.faecium R0026 showed a significant negative correlation with the cholesterol concentration in the medium fermentation broth and a positive correlation with the cholesterol degradation rate.The number of viable bacteria of E.faecium R0026 showed a significant positive correlation with the bacterial BSH enzyme activity.(2)Fucoidan reduced body weight,weight gain,BMI,Lee’s index,liver index and epididymis fat index in ICR mice,with no effect on blood glucose.(3)Fucoidan intervention improved blood lipid levels in mice.(4)Fucoidan intervention improved the levels of LPS,TBA,and TNF-α in mice.(5)Fucoidan improved hepatic steatosis and small intestinal villi disorder in mice.(6)The diversity and richness of the gut microbiota of mice were significantly improved after the intervention of fucoidan,and the content of the dominant gut microbiota was increased.Improvement in gut microbiota was significantly associated with lipid and inflammation levels.Conclusions:(1)Fucoidan was able to increase the BSH enzyme activity and in vitro cholesterol-lowering ability of E.faecium R0026 by increasing the viable count of the bacterium in vitro.(2)Fucoidan improved body weight,weight gain,BMI,organ index serum lipids,inflammation and hepatic steatosis levels in high-fat diet-induced ICR mice.(3)Fucoidan improved obesity-related lipid,bile acid and inflammation levels by increasing the diversity and abundance of gut microbiota and the relative abundance of F.prausnitzii in obese mice.