The Gut Akkermansia Muciniphila Mediates The Regulatory Mechanism Of Fu Brick Tea Polysaccharide To Exhibit The Thermogenic Function Of Adipocytes

The overweight and obesity associated with a long term high-fat diet(HFD)are the basis of many chronic metabolic diseases,and the health problems resulting from this are restricting social and economic development.Activating the thermogenic activity of brown adipose tissue(BAT)and inducing the browning of white adipose tissue(WAT)is a positive and effective strategy to fight against obesity.Some studies have shown that the characteristic fu brick tea after the deliberate fermentation with the fungus Eurotium cristatum has good lipid-lowering and gut microbiota regulation effects,but there is no evidence to show fu brick tea's effect in regulating the thermogenic activity of adipose tissue,and the exact mechanism of fu brick tea in inhibiting obesity is still unclear.In this paper,Fu brick tea aqueous extract(FTE)and Fu brick tea polysaccharide(FBTP)were used as dietary intervention nutritional factors.Obese mice induced by a HFD and"pseudo-sterile" mice induced by antibiotics(Abs)were used as animal models.In addition,the material basis and mechanism of activating the thermogenic activity of BAT and inducing the browning of WAT were deeply explored by using the fecal microbiota transplantation(FMT)and animal interventions for gut microbes experiment,combined with routine biochemical analysis,molecular biology and 16S rDNA gene sequencing technology.The main research contents and results are shown as follows:(1)Mice on high fat diet(HFD)were supplementation of C57BL/6J mice with FTE for 8 consecutive weeks.The results showed that adding 4%and 8%FTE to the HFD could effectively prevent the abnormal weight gain and fat accumulation,reverse the decrease of serum leptin and the increase of insulin level,and effectively improve the glucose tolerance and insulin sensitivity of HFD mice.In addition,8 weeks of FTE intervention enhanced the expression of thermogenic marker proteins(UCP1,PGC-1?)in interscapular brown adipose tissue(iBAT)of HFD mice,and regulated the expression levels of key transcription factors(PRDM16)browning in inguinal white adipose tissue(iWAT)and thermogenic proteins.Meanwhile,it was found that FTE feeding of HFD-fed mice led to decrease in the Firmicutes and the increase of Bacteroidetes at the phyla level,while 8%FTE significantly increased the relative abundance of Akkermansia,Bacillus,Bifidobacterium and Ruminococcus 2 at the genus level,and improved the structural diversity of gut microbiota.The above results indicated that FTE could effectively reduce lipid accumulation and regulate gut microbiota disturbance in HFD mice by promoting the thermogenic activity of fat.(2)Polysaccharide FBTP was obtained from Fu brick tea by means of water boiling and ethanol sedimentation.In addition,through 8 weeks of FBTP intervention on HFD mice,it was found that at low dose of 100 mg/kg·bW,medium dose of 200 mg/kg·BW and high dose of 400 mg/kg-BW,respectively,the weight gain and fat accumulation in HFD mice could be effectively inhibited.In addition,immunofluorescence staining results showed that the intervention of FBTP could enhance the expression of iBAT and iWAT thermogenic marker proteins(UCP1 and PGC-1?)in HFD mice,while the H&E staining results of liver,iBAT,iWAT and epididymal white adipose tissue(eWAT)further confirmed the anti-obesity effect of FBTP.The results of 16S rDNA gene sequencing showed that the high dose of FBTP intervention significantly reduced the relative abundance of Firmicutes,significantly increased the relative abundance of Bacteroidetes at the phylum level,significantly increased the relative abundance of Turiclbacter,Akkemansia and Bifidobacterium,and reduced the relative abundance of Dubosiella at the genus level of HFD mice.(3)FBTP was used to intervene in the "pseudo-aseptic" mouse model established by antibiotics(Abs)for 12 weeks.The results showed that Abs intervention for 12 weeks could eliminate most microorganisms in the intestinal tract of HFD mice,and at the phylum level,Abs eliminated the relative abundance of Firmicutes and Bacteroidetes,which accounted for the main proportion of intestinal microorganisms,and Proteobacteria became the most important phylum in Abs intervention mice.However,FBTP intervention could significantly increase the abnormal decrease of Firmicutes and Bacteroidetes in the gut microbiota level of mice caused by Abs,and significantly increase the relative abundance of Klebsiella in the colon of mice fed with HFD assisted by Abs and decrease the relative abundance of Pseudomonas.In addition,FBTP could significantly improve the Abs-induced weight loss and improve the glucose homeostatic in mice,while the expressions of iBAT and iWAT thermogenic proteins PGC-1?,CIDEA and UCP1 in mice were not significantly changed.The above results indicated that the regulation of FBTP on fat thermogenesis in HFD mice may mainly depend on its changes in intestinal microorganisms.(4)FBTP was used to intervention fecal microbiota of rats.FMT was performed for 8 weeks in rats fed with normal and high-fat diets.The results showed that the fecal microbiota of the rats transfused with FBTP could significantly increase the relative abundance of Akkermansia in the colon of the rats fed with ordinary diet and the obese rats induced by HFD,and reverse the increase of Firmicute and the decrease of Bacteroidetes at thephyla level of the rats caused by HFD.In addition,transplantation of rat faecal treated with FBTP could improved HFD-induced obesity,lipid deposition(eWAT and iWAT),dyslipidemia,glucose homeostasis,and the expression of thermogenic proteins PGC-1? and UCP1 in iBAT and iWAT.The above results indicated that FBTP could promote the colonization of Akkermansia in fecal microbiota of rats and promote the thermogenesis of HFD-induced brown fat and subcutaneous fat in obese rats independently of FBTP intervention.(5)Mice fed with normal and high-fat diets were treated with AKK for 12 weeks.The results showed that 12 weeks of 1×108 CFU/mL AKK intervention could effectively inhibit weight gain and lipid deposition(eWAT and iWAT),improve glucose homeostasis and promote the expression of brown fat and subcutaneous fat thermogenic proteins PGC-1?,CIDEA and UCP1 in mice fed with HFD,In addition,the AKK intervention could reverse the increase of Firmicutes at thephyla level of HFD mice,promote the colonization of AKK in the colon of HFD mice,and reduce the relative abundance of Dubosiella at the genus level.The above results suggest that FBTP in inhibiting obesity by targeting AKK bacteria in the intestinal tract and then regulating the thermogenic function of fat,inhibiting obesity and improving glucose metabolism.