Brain Cells Key to Metformin's Diabetes Power

For over sixty years, metformin has been a cornerstone treatment for type 2 diabetes, yet its precise mechanisms remained partially elusive. New research from Baylor College of Medicine, involving international collaborators, has pinpointed the brain as a critical factor in metformin's action. Published in Science Advances, the study reveals that the drug's ability to lower blood sugar is linked to suppressing the Rap1 protein within the ventromedial hypothalamus.

Experiments with genetically engineered mice lacking Rap1 in this brain region showed no improvement in blood sugar when treated with low-dose metformin. Conversely, administering small amounts of metformin directly into the brains of diabetic mice, at doses thousands of times lower than oral intake, resulted in significant blood sugar reduction. This indicates a highly sensitive brain-based pathway.

Further analysis identified SF1 neurons in the ventromedial hypothalamus as key players, activated by metformin's brain-based action when Rap1 is present. This discovery shifts the understanding of metformin's efficacy, highlighting its potent effects at low concentrations in the brain, unlike the higher doses required for liver and intestinal responses. This opens avenues for developing targeted brain therapies for diabetes and may explain other known benefits of metformin, such as slowing brain aging.