The Screening And Mechanism Of Clostridium Butyricum Strains On Reducing Obesity

Obesity is a chronic disease prevalent all over the world,which is related to the increased risk of many diseases such as type 2 diabetes and nonalcoholic fatty liver.As a multifactorial disease,obesity is not only related to genetic factors,but also influenced by environmental factors such as diet and living habits,sleep quality and circadian rhythm.In recent years,the relationship between gut microbiota and obesity has been continuously revealed,and it has been recognized as one of the environmental factors that cause obesity.Compared with individuals with normal weight,the diversity and composition of intestinal microbiota of obese individuals are obviously different,and the abundance of butyrate-producing Clostridium in intestinal microbiota of obese individuals is obviously reduced.Clostridium butyricum is one of the butyrate-producing Clostridium in intestine,which can play a beneficial role by regulating the metabolic functions of intestine,adipose tissue,liver and brain.Studies have shown that the abundance of Clostridium butyricum is decreasing in patients with type 2 diabetes,and the increase of its abundance is related to the decrease of obesity susceptibility.In addition,Clostridium butyricum supplementation can alleviate obesity-related phenotypes,but its mechanism and material basis for alleviating obesity have not been clarified.Based on the above background,this study screened Clostridium butyricum strains that can resist obesity by establishing an obese mouse model induced by high-fat diet,and analyzed the mechanism and material basis of effective strains to alleviate obesity by means of 16 S r RNA amplicon sequencing,transcriptome,non-targeted metabonomics and real-time quantitative PCR(q PCR).The main results are as follows:(1)Taking C57BL/6J mice as the research object,five strains of Clostridium butyricum isolated from different evolutionary clusters in our laboratory were gavaged while using highfat diet to induce obesity,and the weight,blood lipid,fat mass,adipose tissue inflammation(F4/80 immunohistochemistry),liver pathological changes and inflammation(TNF-α,IL-1β)were used as indicators to evaluate the alleviating effects of different strains on obesity.The results showed that the effective strains CCFM1299 and Z1T1 could significantly inhibit the weight gain(Compared with the HFD group,the body weight decreased by 20.47% and 18.66%respectively)and reduce the fat mass under the high-fat diet,and effectively alleviate the disorder of blood lipid(under the intervention of CCFM1299 and Z1T1,the total cholesterol decreased to 1.54 mmol/L and 1.35 mmol/L,the low-density lipoprotein cholesterol decreased to 0.20 mmol/L and 0.19 mmol/L,and the ratio of low-density lipoprotein cholesterol to highdensity lipoprotein cholesterol decreased to 0.16 and 0.17.),reduce the recruitment of macrophages in adipose tissue,and improve the fatty degeneration and inflammation of the liver.By setting up sodium butyrate group and detecting the content of short-chain fatty acids such as butyric acid(SCFAs)in cecum,it was found that the effect of sodium butyrate was not as good as CCFM1299 and Z1T1,and the effective strains did not significantly change the concentrations of butyrate,propionic acid and acetic acid in cecum.In the aspect of intestinal microbiota,CCFM1299 and Z1T1 had no effect on the α diversity of intestinal microbiota,but changed the β diversity.Both effective strains increased the abundance of Muribaculaceae,and decreased the abundance of Mesorhizobium,Coriobaciliaceae＿UCG＿002 and Erysipelatoclostridium.To sum up,Clostridium butyricum CCFM1299 and Z1T1 are effective strains to relieve obesity,and both strains of Clostridium butyricum have changed the composition of intestinal microbiota in mice.However,butyrate was not the material basis for the two strains to alleviate obesity.(2)Taking Orlistat as a positive control,the effects of effective strains CCFM1299 and Z1T1 on relieving obesity were compared with those of existing diet drugs.The results showed that the effective strains and Orlistat had considerable effects in inhibiting weight gain(the body weight decreased to 35.85 g under the intervention of CCFM1299,34.45 g under the intervention of Z1T1 and 35.39 g under the intervention of orlistat.),reducing fat mass and improving blood lipid and blood sugar.Subsequently,the mechanism of effective strains to improve obesity was explored by q PCR and transcriptomics.The results showed that the two effective strains did not significantly reduce the absorption of lipids in the small intestine,but alleviated obesity by increasing the basal metabolic rate of mice,activating the thermogenic function of brown adipose tissue and improving the inflammation and function of epididymal fat.Furthermore,the potential material basis of the two strains to alleviate obesity was explored by non-targeted metabonomics.Strain CCFM1299 significantly increased the contents of bile acids such as taurocholate(TCDCA),taurocholic acid(TUDCA)and ursodeoxycholic acid(UDCA)in feces.Strain Z1T1 increased the content of allopurinol-1-ribonucleoside(inosine analog)in intestine,which can promote the synthesis of inosine,a purine metabolite.Therefore,strains CCFM1299 and Z1T1 alleviate obesity by participating in bile acid metabolism and purine metabolism respectively.