Northwestern Study Finds Metformin Lowers Blood Sugar via Gut, Not Liver, in Mice
Updated
Updated · Medical Daily · Jul 28
Northwestern Study Finds Metformin Lowers Blood Sugar via Gut, Not Liver, in Mice
2 articles · Updated · Medical Daily · Jul 28
Summary
Nature Metabolism published a 2026 Northwestern mouse study showing metformin lowers blood sugar mainly through the intestine, not the liver long cited in standard explanations.
Intestinal cells became a glucose sink after metformin blocked mitochondrial complex I, slowing energy production and driving those cells to consume more glucose.
NDI1-engineered mice, whose gut cells could bypass complex I blockade, lost much of metformin's glucose-lowering effect, strengthening the case that the intestine is the drug's primary target in that model.
Berberine appeared to engage the same gut pathway, but researchers said limited evidence and weaker manufacturing standards mean it should not replace prescribed metformin.
Two other 2026 papers pointed to brain and ATP-production pathways, suggesting metformin may act in multiple tissues; the findings do not change current dosing or monitoring and still need human confirmation.