Type 2 diabetes (T2D) is associated with dysbiosis of the gut microbiota, though diabetes treatment regimens, including metformin, may confound the results. Forslund et al. (2015) identify distinct disease and drug signatures and highlight the importance of adjusting for treatment when investigating how T2D influences the human gut microbiome.
Mardinoglu, A., Boren, J., & Smith, U. (2016, January 12). Confounding Effects of Metformin on the Human Gut Microbiome in Type 2 Diabetes. Cell Metabolism. Cell Press. https://doi.org/10.1016/j.cmet.2015.12.012