Metformin affects diabetic trial studies

Metformin has been found to have a stronger effect on gut flora than diabetes Type 2, the condition for which it is prescribed.

Metformin is used to help control blood sugar levels in diabetics. Stool samples from more than 700 people – some type 2 diabetic, others healthy – revealed those were taking metformin had more E. coli and less I. barletti then healthy patients and diabetics not taking metformin.

Dr Peer Bork, who led the study said: “It’s surprising that this single drug triggers such a noticeable change in our microbes. Think how many drugs are out there, and how many people take several drugs daily: even if only a fraction of drugs have this big an impact, they could still be dramatically shaping people’s gut.”

The scientists believe differences observed in diabetics’ gut microbial communities was due to patients taking different amounts of metformin during the different studies. The functions of the bacteria that changed for metformin takers suggested they would have elevated butyrate and propionate production.

Kristoffer Forslund, who was involved in the study, said: “The differences we observed in microbial communities could explain some of metformin’s side effects, which means anyone trying to minimise those side effects could think about acting on the microbes in the gut.”

The scientists suggest in the future, a diabetic taking metformin would also take yoghurt or dietary supplements to maintain their inner gut flora.

Oluf Pedersen, who also led the study at the University of Copenhagen, said: “Our study sets a new standard for exploring the impact of various disorders on the human gut microbiota. Ideally, future studies should be run in treatment-naïve patients to avoid confounding effects of medications on disease-specific imbalances of intestinal microbes.

“We weren’t able to show that other types of antidiabetic drugs had any actual impact on the gut microbiota. When studying type 2 diabetes patients not being treated with metformin, we did, however, discover that they—irrespective of whether they were from Denmark, China or Sweden—had fewer of the bacteria which produce the health-promoting short-chain fatty acids.”

Studies in mice have shown an increase in production of short chain fatty acids triggers intestinal gluconeogenesis. In mice the net result is a positive effect on glucose and energy homeostasis – accompanied with reductions in hepatic glucose production, body weight and appetite, said the scientists.

The study was published in Nature.