- A new mouse study suggests metformin works partly through the brain, not just the liver and gut.
- Researchers identified a pathway in the hypothalamus that seems to be needed for the drug’s glucose-lowering effect at low doses.
- The finding is important, but it is still early stage research and not yet a change to clinical practice.
Metformin has been used for more than 60 years, but scientists still have not fully pinned down how it works.
Most of the focus has been on the liver and, more recently, the gut.
This new study points to the brain as another important part of the story.
Researchers looked at a protein called Rap1 in a brain region known as the ventromedial hypothalamus.
In diabetic mice, metformin’s blood sugar-lowering effect at clinically relevant doses depended on suppressing Rap1 activity in that area.
When mice lacked Rap1 in this region, low-dose metformin no longer improved blood sugar.
Other diabetes treatments, including insulin and GLP-1 drugs, still worked.
That suggests the effect was specific to metformin rather than a general failure to respond to treatment.
The team also gave tiny amounts of metformin directly into the brain.
Even at doses far lower than those taken by mouth, blood sugar still fell.
They then identified a group of neurons called SF1 neurons as part of the pathway.
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This is a fascinating mechanistic study, but it is still a mouse study.
It does not mean metformin should suddenly be thought of as a brain drug in routine diabetes care.
What it does mean is that one of the world’s most familiar diabetes medicines may be working in a more complex way than we realised.
