Study On The Regulation Of Gut Microbiota By Marine Bromophenol Compounds And The Hypoglycemic Effect Of Probiotics

Gut microbiota plays a key role in metabolic diseases including type 2 diabetes mellitus(T2DM).3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)-1,2-catechol(BDB)is a natural bromophenol compound isolated from marine red algae pineal algae.Rencently,the research showed that BDB can alleviate hyperglycemia in type 2 diabetic BKS db mice.In order to research whether BDB regulates the composition of gut microbiota during T2 DM treatment,we randomly divided BKS db diabetic mice into groups and treated them with BDB,metformin,or placebo for 7 weeks.Compared with the model group,the fasting blood glucose level of diabetic mice in BDB or metformin treatment group was decreased significantly after 7 weeks.The effects of BDB on the structure and metabolic function of gut microbiota were studied by using 16 S rRNA sequencing and metagenomics.At the family level,the results showed that,BDB and metformin treatment can significantly increase the relative abundance of short-chain fatty acid(SCFAs)producing bacteria Verrucomicrobiaceae and Bacteroidaceae,respectively.At the genus level,the relative abundance of Akkermansia increased significantly in BDB treatment group.The results of metagenomics showed that BDB could alleviate the metabolic disorder of diabetic mice by promoting propionic acid metabolism,inhibiting starch and sucrose metabolism,amino sugar,and nucleotide sugar metabolism.Through phylogenetic analysis,the diversity of bacteria in the intestinal tract of BKS db mice was studied.209 strains of bacteria were obtained from the fecal samples of mice,including 4 phyla,16 genera,and 25 species.The most abundant genus was Lactobacillus,accounting for 42.6% of the total isolated bacteria.The in vitro probiotic characteristics detection and analysis of 25 isolated strains showed that Lactobacillus strains all have high acid resistance,alkali resistance,and antioxidant activity.The survival rate of Lactobacillus johnsonii BM611 in simulated gastric juice can reach 81.90% for 3 h,and the survival rate for 6 h in simulated intestinal juice can reach 81.98%.Lactobacillus johnsonii BM611 showed strong DPPH free radical scavenging ability in cell disruption solution and cell-free excretory supernatants,with scavenging rates of 44.85% and 13.05%,and strong hydroxyl free radical scavenging ability,with scavenging rates of 17.16% and 15.11%.Lactobacillus johnsonii BM611 can significantly inhibit the growth of opportunistic bacteria such as Escherichia coli,and promote the glucose consumption of C2C12 cells.The hypoglycemic effect of Lactobacillus johnsonii BM611 on BKS db mice and its effect on lipid metabolism related factors were studied by animal experiments.The results showed that Lactobacillus johnsonii BM611 could significantly reduce the fasting blood glucose level of BKS db mice,improve the glucose tolerance and lipid metabolism of type 2 diabetic mice,and the effect of combined treatment with BDB was significantly better than that of single bacterial treatment;Histological and pathological analysis showed that Lactobacillus johnsonii BM611 had no adverse effect on the tissue,but could improve the status of the pancreas and liver tissue in mice.This study not only explored the regulatory effect of marine bromophenol compound BDB on gut microbiota of diabetic mice,but also provided reference for the development of gut microbiota diversity of BKS db model mice,and provided resources for the further development of probiotic hypoglycemic strains.