Enterotype Bacteroides Is Associated With A High Risk In Patients With Type 2 Diabetes

BackgroundType 2 diabetes(T2D),which is a complex disorder influenced by both genetic and environmental components,has become a major public health issue throughout the world.Nowadays,increasing evidence shows the relationship between gut microbiota and T2D.Many studies revealed that the microbiome of type 2 diabetic patients is characterized by an enrichment in several opportunistic pathogens,sulphate-reducing bacteria,and the depletion of some probiotics,and some butyrate-producing bacteria.In addition,both human and rodent studies have shown that transfer of the intestinal microbiota can also result in the transfer of specific metabolic disease phenotypes,involving hyperglycemia.Modification of the gut microbiota by diet and prebiotics can improve glucose tolerance and insulin response.Moreover,the therapeutic effects of some hypoglycemic agents such as metformin and a-glucosidase inhibitors may partially be mediated by the gut microbiota.However,the outcomes are not always concordant.Larsen N et al found a lower within-sample diversity in T2D patients while Qin J et al did not observe a significant difference in this diversity between T2D patients and the control group.Also,the latter study found an increase in Akkermansia muciniphila,a mucus-colonizing bacterium that plays a protective role in the gut barrier function,in T2D patients.However,Zhang et al reported the opposite effect,specifically,a decreased abundance of A.muciniphila,in diabetic and glucose-intolerant patients.These discrepancies show that we still have much to know about the relationship between T2D and gut microbiota.Enterotype is another means to investigate the gut microbiota.Arumugam et al first introduced this method in 2011 in a study where,based on the taxonomic composition,they clustered human fecal metagenomic samples from three continents into three enterotypes:the Bacteroides enterotype(ET B),Prevotella enterotype(ET P),and Rumirnococcus enterotype which are not associated with ethnicity,gender,age,or body mass index(BMI).Since then,several studies have replicated enterotypes in new datasets and to different extents,both in the numbers of enterotypes and strength of the statistical support.However,few studies have directly investigated the relationship between enterotypes and T2D.Hence,here,using taxa and enterotype data,we aimed to investigate if enterotypes exist within T2D and non-diabetic controls and if there is an association between enterotypes and T2DMaterials and MethodsWe enrolled 134 patients with type 2 diabetes and 37 non-diabetic controls.The anthropometric and clinical indices of each subject were measured.Fecal samples of each subject were also collected and were processed for 16S rDNA sequencing Multiple logistic regression analysis was used to determine the associations of enterotypes with type 2 diabetes.Multiple linear regression analysis was used to explore the relationship between lipopolysaccharide levels and insulin sensitivity after adjusting age,BMI,TG,HDL-C,DAO and TNF-α.The correlation analysis between factors and microbiota was identified using Spearman correlation analysis.The correlation analysis between factors was identified using partial correlation analysis.Results1.Comparison of baseline dataCompared with the nondiabetic controls,T2D patients had significantly higher age,HbAlc,FPG,FINS,2hPG,2hlNS,and TG.Patients with T2D also exhibited a significantly lower DBP,2hCP,HDL-C,HOMA-β,and Gutt-ISI relative to the nondiabetic control group.However,there was no difference between the two groups in the HOMA-IR values.2.Gut microbiota analysis between the control and T2D groupAnalysis of the α-diversity revealed that there was a lower bacterial diversity in the fecal samples from T2D patients compared with the nondiabetic control group.At the phylum level,we found that the T2D group had lower numbers of Bacteroidetes and a higher F/B ratio than the control group.In addition,the T2D group was enriched for Proteobacteria and Actinobacteria.At the genus level,there were 23 genera significantly different between the two groups.Factor analysis showed that the T2D group had significantly higher levels of DAO,LPS,and TNF-α.3.Enterotype analysis of all 171 subjectsThe fecal communities from all 171 subjects clustered into two enterotypes distinguished by the levels of Bacteroides and Prevotella.Some genus which were richer in Bacteroides enterotype had positive correlations with bad glucose metabolic indices.Logistic regression analysis showed that the Bacteroides enterotype was an independent risk factor for type 2 diabetes by decreasing insulin sensitivity.The levels of LPS and TNF-α were higher in the Bacteroides enterotype compared to the Prevotella enterotype.Partial correlation analysis showed that LPS was closely associated with DAO,TNF-α and Gutt-ISI after adjusting for multiple covariates Furthermore,the level of LPS was found to be an independent risk factor for insulin sensitivity.ConclusionThere was a significant difference in the gut microbiota structure between the T2D and non-diabetic groups.T2D group showed lower bacterial diversity compared with nondiabetic controls.The T2D group had lower numbers of Bacteroidetes and a higher F/B ratio than the control group.In addition,the T2D group was enriched for Proteobacteria and Actinobacteria.Factor analysis showed that the T2D group had significantly higher levels of DAO,LPS,and TNF-α.Furthermore,we identified two enterotypes among our subjects and showed that ET B was an independent risk factor for T2D.Moreover,this increased risk was associated with increased LPS levels and decreased insulin sensitivity in the ET B.