Studies in patients with T2D indicate that the gut microbiota is enriched in pathways such as sugar transport across membranes, which increases glucose uptake by cells; excretion of branched-chain amino acids (BCAA), contributing to IR; methane metabolism associated with the anaerobic gut environment; xenobiotic degradation; metabolic transformations linked to drug resistance; and sulfate reduction, which decreases insulin sensitivity. This evidence concerns the gene INS and type 2 diabetes mellitus.