Study Of Different Gut Microbiota Structures Response To Laminaria Japonica Fucoidan

Obesity is considered as a metabolic disorder related with the development of type 2diabetes mellitus and cardiovascular disease.Obesity is characterized by increased body weight,fat accumulation and gut microbiota dysbiosis.Over the past several decades,the prevalence of obesity has been a major threat to public health.Studies have shown that fu-coidan can play an anti-obesity effect by regulating the gut microbiota.However,recent re-ports have shown that the composition of an individual’s initial gut microbiota can affect the beneficial effects of polysaccharides.Therefore,more attention should be paid to the utili-zation and functional effects of fucoidan of different microbiota.Laminaria japonica is the major source of fucoidan.In the present study,fucoidan was isolated from L.japonica and the physicochemical properties of it was determinted.The effects of dietary L.japonica supplementation on the gut microbiota of normal human and the capabilities of the gut microbiota to utilize fucoidan were evaluated,and the bacteria involved in the utilization of fucoidan was revealed.Furthermore,mouse models with altered gut microbiota were established by treating with low dose of penicillin or metronidazole.And the anti-obesity effects of Fuc _Lj in normal mice and gut microbiota-altered mice were then compared and investigated.The present study provide a basis for the better development of fucoidan in personalized nutrition and precision medicine,the results are as follows:1.In this study,fucoidan of L.japonica(Fuc _Lj)was isolated by enzymolysis and pre-cipitated with hyamine quaternary ammonium（the yield was 2.0%）,and Fuc _Lj contained35.6±0.4%total sugar,6.6±0.2 protein,22.2±0.7%sulfate and 12.1±0.5%uronic acid,and the average molecular weight was 627.5 k Da.The major monosaccharide components of Fuc _Lj were fucose and galactose in a molar ratio of 7.5:1.0.2.The changes in the gut microbiota of 12 volunteers who continuously ingested L.japonica for 14 days were analyzed.A 14-day L.japonica supplementation could balance Firmicutes/Bacteroidetes ratio.The Fuc _Lj’utilization capability was not significantly en-hanced by L.japonica supplementation and it is varied among individuals.Gut microbiota from Erysipelotrichaceae,Bacteroidaceae and Prevotellaceae contributed to the degradation of Fuc _Lj’.Of note,the generation of acetic acid and the total short-chain fatty acids（SCFAs）in fermentation were consistent with the consumption of Fuc _Lj’.In addition,gut microbiota communities showed different monosaccharide preferences in Fuc _Lj’consumption.3.Low-dose antibiotics were used to establish mouse model with different gut micro-biota structures.The 16S r RNA sequencing revealed the differences of gut microbiota among penicillin-treated（LDP group）,metronidazole-treated（LDM group）and normal groups（CTL group）,and mice treated with penicillin was characterized by more relative abundance of phylum Bacteroidetes,family Muribaculaceae and Bacteroidaceae.Furthermore,Fuc _Ljameliorated HFD-induced body weight gain,fat accumulation,serum lipid profiles,insulin resistance,hepatic steatosis and adipocyte hypertrophy in LDP group and CTL group mice while no effects were observed in LDM group mice.Overall,mice with different initial gut microbiota differentially respond to Fuc _Lj supplementation on a high-fat diet,and neomycin-sensitive gut bacteria negatively corelated with obesity symptoms and were required for Fu-c _Lj’s anti-obesity effects.Moreover,the anti-obesity effects are not dependent on the utiliza-tion of Fuc _Lj by gut microbiota to produce SCFAs.