Type 2 diabetes (T2D) is a complex metabolic syndrome characterized by insulin dysfunction and abnormalities in glucose and lipid metabolism. The gut microbiome has been recently identified as an important factor for development of T2D. In this study, a total of 102 subjects were recruited, and we have looked at the gut microbiota of prediabetics (PreDMs) (n = 17), newly diagnosed diabetics (NewDMs) (n = 11), and diabetics on antidiabetic treatment (KnownDMs) (n = 39) and compared them with healthy nondiabetics (ND) (n = 35). Twenty-five different serum biomarkers were measured to assess the status of diabetes and their association with gut microbiota. Our analysis revealed nine different genera as differentially abundant in four study groups. Among them, Akkermansia, Blautia, and Ruminococcus were found to be significantly (P < 0.05) decreased, while Lactobacillus was increased in NewDMs compared to ND and recovered in KnownDMs. Akkermansia was inversely correlated with HbA1c and positively correlated with total antioxidants. Compared to ND, there was increased abundance of Megasphaera, Escherichia, and Acidaminococcus and decreased abundance of Sutterella in KnownDMs. Among many taxa known to act as community drivers during disease progression, we observed genus Sutterella as a common driver taxon among all diabetic groups. On the basis of the results of random forest analysis, we found that the genera Akkermansia and Sutterella and that the serum metabolites fasting glucose, HbA1c, methionine, and total antioxidants were highly discriminative factors among studied groups. Taken together, our data revealed that gut microbial diversity of NewDMs but not of PreDMs is significantly different from that of ND. Interestingly, after antidiabetic treatment, the microbial diversity of KnownDMs tends to recover toward that of ND.IMPORTANCE Gut microbiota is considered to play a role in disease progression, and previous studies have reported an association of microbiome dysbiosis with T2D. In this study, we have attempted to investigate gut microbiota of ND, PreDMs, NewDMs, and KnownDMs. We found that the genera Akkermansia and Blautia decreased significantly (P < 0.05) in treatment-naive diabetics and were restored in KnownDMs on antidiabetic treatment. To the best of our knowledge, comparative studies on shifts in the microbial community in individuals of different diabetic states are lacking. Understanding the transition of microbiota and its association with serum biomarkers in diabetics with different disease states may pave the way for new therapeutic approaches for T2D.

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