Effects Of Metformin On Gut Microbiota In Patients With Type 2 Diabetes Mellitus

ObjectiveDiabetes mellitus is a worldwide metabolic disease,and more than ninety percent of diabetes patients are diagnosed of type 2 diabetes mellitus(T2DM).The pathogenesis of T2DM has not been fully understood.In recent years,more and more evidence shows that the gut microbiota community plays an important role in the pathogenesis of T2DM.Although there are various of hypoglycemic drugs,metformin is still recommended as the first choice of treatment for patients with T2DM.Many evidences have shown that the key of metformin’s hypoglycemic effect lies in the digestive tract.In recent years,some animal experiments and clinical studies have been conducted to explore the effect of metformin on gut microbiota of those patients,but most of the research population concentrated on the western population,and the treatment period of most of those studies are 2-4 months.The objective of this study is to establish a longitudinal cohort in T2DM patients treated with metformin,to explore the differences of gut microbiota before metformin treatment,2 weeks and 1 month after metformin treatment,and correlations between glucose and lipid metabolism indicators and those gut microbiota,so as to determine the effects on gut microbiota of metformin,and provide reference for the future researches on exploring the mechanism of metformin in gastrointestinal tract,and lay the foundation for metabolic regulation by regulating gut microbiota.MethodsThis study is a longitudinal cohort study.19 newly diagnosed T2DM patients who meet the inclusion and exclusion criteria were enrolled.They were treated with metformin 0.5g three times a day.Fecal samples were collected before treatment,2 weeks and 1 month after treatment.The 16S rDNA v3-4 region was sequenced by Illumina hiseq sequencing platform.Peripheral blood samples were collected before treatment and 1 month after treatment to analyze the glucose and lipid metabolism related indicators.Results1.A total of 19 patients with newly diagnosed T2DM were included in this study.According to the treatment period of metformin,they were divided into pre medication group(EJSG0 group),2-week after metformin treatment group(EJSG1 group)and 1-month after metformin treatment group(EJSG2 group).The average age of those patients was 48.95±13.30 years,After 1 month of metformin treatment,the body mass index(BMI)and weight of those patients decreased,but the difference was not statistically significant;fasting plasma glucose(FPG)and glycated hemoglobin Alc(HbA1c)decreased significantly;blood lipid indexes,homeostatic model assessment of insulin resistance(HOMA-IR)and homeostasis model assessment-β(HOMA-β)were improved,but differences were not statistically significant.2.A total of 716 operational Taxonomic Units(OTUs)were obtained by OTUs cluster analysis of the valid sequences of all samples,including 714 in EJSG0 group,707 in EJSG1 group and 694 in EJSG2 group.Compared with EJSG1 and EJSG2 groups,EJSGO group had 3 unique OTUs.The number of unique OTUs in EJSG1 group and EJSG1 group was 9 and 2 respectively,and that in EJSG0 group and EJSG2 group was 22 and 2 respectively.The results showed that there was no significant difference in the distribution of gut microbiota among before and after metformin treatment for 2 weeks and 1 month.3.α diversity analysis showed that the species richness and diversity of gut microbiota in patients after oral metformin treatment showed a downward trend,and the Shannon index and Simpson index after 1 month of treatment were significantly lower than those before treatment.4.PCoA analysis showed that there was no significant difference in the overall composition of gut microbiota before metformin administration,2 weeks and 1 month after metformin administration.5.In terms of species analysis,at the family level,it was found that after 2 weeks and 1 month of metformin treatment,the number of f_Peptostreptococcaceae and f_Clostridiaceael were decreased significantly.At the genus level,after 2 weeks of treatment,the number of g_Peptostreptococcaceae,g_Peptoclostridium,g_Clostridium sensu strictol,g_Veillonella and g_Intestinibacter decreased significantly.And after 1 month of treatment,except for the above bacteria,the species abundance of g_Ruminococcaceae_uncultured,g_Turicibacter,g_Ruminiclostridium9,g_Flavonifractor and g_Lachnospiraceae NK4A136 also decreased significantly.6.By Spearman correlation analysis,we found that g_Ruminococcaceae_uncultured positively correlated with HOMA-IR(r=0.664,P=0.018)and negatively correlated with alanine aminotransferase(r=-0.671,P=0.002).g_Clostridium sensu stricto 1 positively correlated with fasting C-peptide(r=0.572,P=0.032)and urinary microalbuminuria(r=0.722,P=0.005).g_Veillonella positively correlated with BMI(r=0.673,P=0.002).ConclusionIn this study,we explored the differences of gut microbiota before metformin treatment,2 weeks and 1 month after metformin treatment in a longitudinal cohort.We found that the species diversity of gut microbiota decreased significantly after metformin administration,and the abundance of bacteria related to impairment of intestinal mucosal barrier and bile acid metabolism decreased,and the abundance of g_Escherichia-Shigella increased,while there was no significant difference in the abundance of g_Akkermansia.We believe that metformin treatment can play the role of metabolic regulation by changing the abundance of specific bacteria without increasing the species richness of gut microbiota.However,some beneficial bacteria species could not significantly increase in just 1 month,which needs a long-term treatment and observation.