Fibrosis is characterized by dysfunctional repair responses to tissue injury and occurs in a number of organs. Lung fibrosis is a potentially fatal respiratory disorder that affects millions of people worldwide, but effective therapeutic interventions have yet to be identified. New research shows that the activity of AMPK—a protein that regulates cellular metabolism—is lower than normal in humans and mice with lung fibrosis. Moreover, treatment with an AMPK-activating compound called metformin reduces lung fibrosis in mice. The findings demonstrate the potential of repurposing metformin, which is already approved for the treatment of type 2 diabetes, as a therapeutic strategy for progressive fibrotic disorders in humans. According to the authors, this is the first study to demonstrate that the resolution of lung fibrosis can be accelerated with a pharmacological intervention that targets cellular metabolism. The study, which was partly funded by NHLBI, was published in Nature Medicine.