Metformin is the first-line treatment for type 2 diabetes. Its mechanism of action is complex and a new study reveals an unexpected effect.
Type 2 diabetes is treated with oral medications, of which metformin is the most frequently prescribed drug.
Doctors use oral antidiabetics to treat non-insulin dependent type 2 diabetes. One of the most frequently prescribed treatments in the world, which has been included in the list of essential medicines of the World Health Organization (WHO), is metformin. This substance has been prescribed since the 1960s for its hypoglycemic effect: it lowers blood sugar levels. However, its complex mode of action has never been fully explained. One study is providing new indications thanks to the use of a state-of-the-art imaging technique normally used to detect the presence of hidden cancers.
Sugar in the stool
To study the effects of metformin, researchers at the University of Kobe, Japan, used fluorodeoxyglucose (FDG)-positron emission tomography (PET) in combination with a CT scanner and an MRI scanner. FDG behaves like sugar in the human body, and some cancers have a known sugar taste. Therefore, this imaging technique is generally used to detect the presence of tumors or metastases that are difficult to detect with other imaging techniques. In this research, which was published in the journal Diabetes Care, it was used to track the FDG pathway (and thus the sugar in this case) in the body of patients who received metformin and others who were not receiving the diabetes medication.
The team found that sugar is highly accumulated in the intestines of patients who take metformin. To better understand the phenomenon, they then examined the intestinal mucosa and its contents, including the stool, separately. They found that metformin causes blood sugar to be transferred from the blood to the ileum (the terminal part of the small intestine) and then excreted through the feces. This was a completely unexpected discovery that could contribute to the development of new diabetes drugs.
The effect on microbiota
Metformin also acts on other targets of the body, such as the fatty acid route and sugar production in the liver. Studies have also shown that its effectiveness depends on the diet and composition of the patients’ intestinal microbiota. Microbiota which is modified by the drug in question as sugar can affect the growth of certain bacteria, it seems possible that metformin-induced excretion of glucose in the intestine is responsible for this variation in the composition of the microbiota.