Microbiota and diabetes: an increasingly relevant association

Abstract

333field was opened for further investigations and the term "altered microbiota signature in T2D" was established.In this issue of Polish Archives of Internal Medicine (Pol Arch Intern Med), Salamon et al 6 report on a small study where they investigated fecal microbiome in patients with T1DM, T2DM, and healthy controls. Using 16S ribosomal RNA next generation sequencing, the authors observed that patients with T2DM differed with respect to their microbiome from both T1DM subjects and healthy controls. Patients with T2DM were char acterized by a higher ratio of Firmicutes to Bac teroidetes and demonstrated reduced fecal con centrations of certain Ruminococcaceae, Lachno spiraceae, Clostridiales, Bacteroides, Anaerostipes, and Roseburia, whereas the concentrations of Ruminococcus, Enterobacteriaceae and Proteobacte ria, all rather proinflammatory bacterial strains, were increased. Proteobacteria are considered pro inflammatory and might be able to drive immune responses characterized by increased interferon γ expression. 7 Concentrations of Akkermansia muciniphila, a rather well characterized commensal with mainly antidiabetic and anti inflammatory properties, 8 were increased in T2DM patients in the study by Salomon et al, 6 and the authors pro posed that accompanying metformin treatment might have caused this effect. 9 The findings by Salamon et al 6 with A muciniphila are in contrast to several other studies which have demonstrated that obesity and related metabolic dysfunction are characterized by decreased fecal concentrations of this bacterium. 10 Interestingly, the microbiota composition in T1DM subjects did not differ sig nificantly from that in healthy controls. 6 Some at tention regarding the presented results, however, is needed as authors could not provide data on di etary details and stool consistency, both factors substantially affecting gut microbiota composi tion. Furthermore, the number of analyzed pa tients was rather low (T1DM, n = 22; T2DM, n = 23; controls, n = 23). Despite these shortcomings, The human intestinal tract contains an enor mous number of bacteria, archaea, and virus es. Recent estimates announced that a ratio of 1.3 bacterial cells might exist for every 1 hu man cell. 1 Early studies believed that genes of this microbial world mainly encode functions affecting pathways favoring digestion of com plex carbohydrates or the control of immunity, whereas recent evidence supports that the mi crobiota has major functions in the regulation of metabolic pathways in health and disease. 2 It has been shown in the past years that obese human subjects exhibit a gut microbiome sig nature. 3 Two major studies from the following years showed that such a microbiome signature might also exist in humans with type 2 diabe tes mellitus (T2DM). 4,5 In the first metagenome wide association study, researchers from Chi na demonstrated an intestinal dysbiosis char acterized by a decrease in butyrate producing Roseburia intestinalis and Faecalibacterium prausnitzii. 4 When analyzing potentially associated...

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“…Dysbiotic gut microbiota via synthesizing neuroactive metabolites are able to counteract secretion, motility, and blood flow within the GI tract and, additionally, transfer neural signals through vagus nerve and spinal cord routes. Therefore, the modulation of microbiota-gut-brain pathways opens up new avenues for the management of chronic diseases both of psychiatric and organic origin [12,[138][139][140][141][142][143].…”

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“…Dysbiotic gut microbiota via synthesizing neuroactive metabolites are able to counteract secretion, motility, and blood flow within the GI tract and, additionally, transfer neural signals through vagus nerve and spinal cord routes. Therefore, the modulation of microbiota-gut-brain pathways opens up new avenues for the management of chronic diseases both of psychiatric and organic origin [12,138,139,140,141,142,143].…”