Bifidobacterium bifidum G9-1 ameliorates soft feces induced by metformin without affecting its antihyperglycemic action

Recent studies of metformin, the first-line drug for type 2 diabetes, have reported the involvement of gut microbiota in the mechanism underlying its antihyperglycemic effect. However, the mechanisms underlying the development of diarrhea and bloating, which are adverse effects of metformin, are unclear, and these effects decrease the quality of life of metformin-receiving patients with diabetes. In this study, we focused on the effects of metformin on gut microbiota. Namely, we examined the effects of Bifidobacterium bifidum G9-1 (BBG9-1), which has the ability to improve dysbiosis, on the changes in gut microbiota and occurrence of soft feces (increased fecal water content) during the administration of metformin. The results showed that coadministration of BBG9-1 and metformin suppressed metformin-mediated changes in the gut microbiota and, thus, soft feces. Meanwhile, BBG9-1 did not influence the antihyperglycemic effect of metformin. Based on these results, we believe that BBG9-1, which could improve gut microbiota, suppresses metformin-induced soft feces without influencing the drug’s antihyperglycemic effect.