Abstract
Background: Metformin is the first-line oral therapy for type 2 diabetes mellitus. However, its mode of action is poorly defined. There is an increasing awareness regarding the cross talk of gut microbiota and metformin. The current review aimed to assess the bidirectional relationship between metformin and gut microbiota.
Methods: Electronic search was conducted in Pub Med and the first 100 articles in Google Scholar published until November 2019. However, only randomized controlled trials on humans published in the English language were included. The terms "gut microbiota," "gut flora "and "metformin" were as keywords to perform the search. Although 124 articles were retrieved, only six met the inclusion criteria of the study.
Results: Of the six full texts of randomized controlled trials included in the study, two-thirds were published in Europe, one in the USA, and one in China. Six hundredthirty five patients were included and the duration of the studies ranged from seven days to six months. The studies concluded that microbiota modulates some metformin actions on plasma glucose; while metformin enhances the abundance of microbiota that positively affect insulin resistance and plasma glucose.
Conclusion: The current review showed that microbiota dysbiosis may mediate metformin antidiabetic effects. Whereas metformin shifted the gut microbiota toward the beneficial species ameliorating insulin resistance. The present study might provide insights into a novel therapeutic approach to treat type 2 diabetes mellitus.