Impact Of Gut Microbiota And Serum Metabolites On Pancreatic Islet Function In Type 2 Diabetes Mellitus

Objective:1.To clarify the changes of gut microbiota in patients with overweight-obesity and type 2diabetes mellitus(T2DM),and the microbial features unique to each condition.2.To assess the association of gut microbiota with insulin sensitivity and pancreatic ?-cell function in type 2 diabetic subjects.Methods:1.Subjects were divided into fourgroups:(1)Healthy control(HC)with normal weight and blood glucose;(2)Overweight-obesity(OWO)with normal blood glucose;and patients with T2 DM furtherdivided into two subgroups:(3)Type 2 diabetes with overweight-obesity(OOD)and(4)Type 2 diabetes without overweight-obesity(T2D).We collected general clinical data of all subjects and performed the assessment of pancreatic ?-cell function in type 2 diabetic patients.2.The 16S rRNA sequencing analysis of all stool samples were performed.We evaluated the abundance and diversity of intestinal microbiota in fourgroups,and identified the significantly differential gut microbiota in different groups,as well as assessed intestinal bacterial symbiotic relationship.3.Spearman correlation analysis of differential bacterial genera with clinical metabolic indicators and multi-layered islet ?-cell function parameters were carried out to find the bacterial genera that have potential effects on ?-cell function.Results:1.The patients of type 2 diabetes with overweight-obesity had more obvious insulin resistance,while subjects of type 2 diabetes without overweight-obesity had worse total insulin secretion and pancreatic ?-cell dysfunction.2.The abundance and diversity of the gut microbiota decreased in patients with T2 DM and overweight-obesity,and there were similarities and differences in microbial changes,such as the decline of some butyrate-producing bacteria and the rise of Escherichia-Shigella in both two conditions;however,Blautia was mainly enriched in overweight-obese subjects,while Akkermansia and Lactobacillus were enriched in type2 diabetic patients.3.The symbiotic interactions within intestinal bacteria changed in both overweight-obese and T2 DM patients.4.The imbalance of gut microbiota was closely related to glucose metabolism and islet?-cell function,among which Ruminococcus gnavus group correlated positively with HOMA-? and Desulfovibrio linked negatively with ISSI-2.Conclusions:1.The gut bacterial diversity and richness declined in type 2 diabetic patients,gut microbiota imbalanced,especially,some butyrate-producing bacteria decreased.2.Insulin sensitivity and pancreatic ?-cell function in patients with T2 DM were closely related to aberrant gut microbiota.Objective:1.To clarify the alterations of serum metabolites in patients with type 2 diabetes mellitus(T2DM).2.To expore the association between serum metabolites and pancreatic ?-cell function in type 2 diabetic subjects.Methods:1.Subjects were divided into three groups:(1)Healthy control(HC)with normal weight and blood glucose;and patients with T2 DM further divided into two subgroups:(2)Type 2 diabetes with overweight-obesity(OOD)and(3)Type 2 diabetes without overweight-obesity(T2D).We collected general clinical data of all subjects and assessed pancreatic ?-cell function in type 2 diabetic patients.2.The serum metabolomics analysis was performed.We clarified the alterations of serum metabolite profiles in type 2 diabetic subjects.3.The correlation between the differential metabolites and aberrant gut microbiota in Part 1 were analyzed by Spearman analysis.4.Further analyses were performed to expore the association between serum metabolites,especially microbial tryptophan catabolites,and pancreatic ?-cell function of patients with T2 DM.Results:1.The serum metabolite profiles of patients with T2 DM altered,the main abnormal metabolites involved in a variety of fatty acids and amino acids.Significantly,tryptophan and its derived metabolites reduced in type 2 diabetic patients.2.The level of differential metabolites was related to the abundance of aberrant gut microbiota.Tryptophan,indole and 3-indoleacrylic acid positively associated with Lachnospiraceae NK4A136 group,Butyricicoccus and Fusicatenibacter but negatively correlated Lactobacillus.3.Microbial tryptophan catabolites associated strongly with pancreatic ?-cell function in type 2 diabetic subjects.Tryptophan and indole were positively correlated to Ins120 and Cp120.Indole-3-lactic acid and 1-acetylindole were significantly positive correlation with total insulin responses and ?-cell function.Conclusions:1.Serum tryptophan and its derivative metabolites decreased in patients with T2 DM.2.Tryptophan catabolites affected by gut microbiota were closely related to pancreatic?-cell function in type 2 diabetic subjects.Objective:To reveal the impact of microbial tryptophan catabolites indole on mediating islet function in db/db mice.Methods:1.After 6-week-old male db/db mice(BKS background)and littermate wild-type m/m mice were adaptively fed for two week,the db/db mice were randomly divided into:(1)db/db group(db/db): db/db diabetic mice were fed with standard chow diet for five weeks;(2)Indole group(Indole): db/db mice were fed with same diet and indole intervention(50mg/kg intraperitoneal injection)daily for total five weeks;(3)B+I group(B+I): db/db mice were fed with same diet accompanied by drinking water containing broad-spectrum antibiotics(to deplete the impact of intestinal bacteria)and indole intervention(50mg/kg intraperitoneal injection)daily for total five weeks;(4)m/m group(m/m): m/m mice were fed with same diet for 5 weeks.2.Body weight and fasting blood glucose of all mice were monitored weekly.After metabolite intervention for 5 weeks,IPGTT and IPITT were performed to assess glucose metabolism and insulin sensitivity,and fasting insulin and serum total GLP-1 level were tested.3.The pancreatic tissue of mice were performed H&E staining and immunofluorescence staining to observe the morphological and structural changes of islets,and phenotypic changes of ? and ?-cell.The expression of GLP-1 in colon of mice was detected using immunofluorescence staining.The status of islet inflammation was evaluated by immunohistochemical staining and RT-PCR.Results:1.Indole slightly reduced blood glucose in db/db mice,especially when combined with antibiotics intervention,significantly alleviated insulin sensitivity of db/db mice.2.Intervention of indole or combined antibiotics improved pancreatic islet morphology in db/db mice and reshaped the balance of islet ?/? cells.3.The islet macrophage infiltration remarkablely increased in db/db mice and the expression of IL6 up-regulated.Noteworthy,indole combined with antibiotics intervention ameliorated macrophage infiltration of db/db mice and declined the expression of IL6 m RNA.4.Indole recovered the expression of colon GLP-1 in db/db mice,however serum total GLP-1 level had no significant change.Conclusions:1.Indole,a microbial tryptophan catabolite,improved the impaired islet function in db/db mice.2.Indole exerted a beneficial effect on islet function involving in both ameliorating islet inflammation and recovering the expression of colon GLP-1 in db/db mice.3.Microbial tryptophan catabolite indole may be an important signal molecule between the crosstalk of gut microbiota and pancreatic islets.