Metformin lowers blood sugar by causing sugar excretion thru stool: Study

Researchers at Kobe University Graduate School of Medicine have discovered that metformin brings down blood sugar by causing sugar to be excreted in the stool.The findings of the study have been published in the online edition of Diabetes Care.

Metformin is the the most widely prescribed anti-diabetic drug. Administration of metformin lowers blood sugar levels, but the mechanism behind this effect was not clear. Metformin's mode of action has thus been actively researched over the world.

Metformin's mechanism of action is being enthusiastically investigated due to its diverse effects on the body, making it potentially useful in treating diseases other than diabetes in the future. Better understanding of the mechanism also helps target the therapy precisely to those patient groups that will benefit from it.

This is a completely new discovery that had not been previously been predicted.The research team revealed that metformin promotes the excretion of blood sugar from the large intestine into the stool by using new bio-imaging apparatus PET-MRI.

A number of antidiabetic drugs are available including a number of new medications that reduce blood sugar concentration . However metformin remains one of the oldest classes of drugs and has been used for more than 60 years. Metformin is a first-line drug in many countries that is the most frequently prescribed diabetes medication.

The research team used PET-MRI to investigate the movement of sugar in the bodies of diabetic patients, both those who were taking metformin and those who were not. The team found that sugar (i.e. FDG) is heavily accumulated in the intestine of patients taking metformin.

The research team subsequently investigated the "wall of the intestine" and the "inside of the intestines" separately using a special technique to understand where in the intestine sugar accumulates.

FDG-PET (fluorodeoxyglucose-positron emission tomography) is an imaging test to study where and how much FDG (a substance similar to sugar) is accumulated in the body after the administration of this substance through the vessels. Recently, a device in which PET and MRI (magnetic resonance imaging) are integrated (PET-MRI) has been developed. MRI is used to examine the inside of the body using a strong magnetic field. It can examine bodily structures that cannot be analyzed by CT.

They found that, in patients taking metformin, more sugar was accumulated in the areas inside the intestine that are distal to the ileum . On the other hand, there was no difference in sugar accumulation in the wall of the intestine between patients who were taking and not taking metformin.

These results indicate that, when a patient takes metformin, blood sugar is released from the intestine into the stool. Not only the finding that metformin promotes the excretion of sugar into the stool, but also the revelation that sugar is excreted from the intestine into the stool itself are new discoveries that were not anticipated.

In the present study, the new imaging technology (PET-MRI) allowed the research team to investigate the accumulation in the wall and the inside of the intestine separately.This revealed for the first time that metformin-induced accumulation of sugar occurred exclusively inside the intestine.

However it was not possible to quantitatively evaluate how many grams of sugar was excreted in the stool. The significance of this discovery will be further confirmed by using a new imaging method that will enable the excreted sugar in the stool to be quantified.

It is hypothesized that since changes in nutrients such as sugar affect the growth of bacteria, it is possible that metformin's effect of excreting sugar into the intestine may also be related to the changes in the intestinal flora.

For further reference log on to:

Diabetes Care (2020).