A new mouse study shows that reducing insulin signaling, specifically in the brain, boosts longevity. The findings help explain two seemingly contradictory observations: people with type 1 diabetes lack insulin-producing cells and must inject the peptide in order to stay healthy. But studies in mice and flies show that reducing insulin lengthens life span.

Scientists genetically engineered mice to dampen part of the insulin-signaling pathway in the brain. The mice lived longer, despite being overweight and having higher blood-glucose levels than normal mice--two characteristics associated with type 2 diabetes in humans.

Exercise and diet can mimic this effect by keeping the body sensitized to insulin, and therefore limiting the brain's exposure to the hormone. In the future, drugs that target this pathway in the brain might be one approach to stopping the diseases of aging. The findings also suggest that diabetes treatments should focus on sensitizing cells to insulin, rather than on boosting insulin levels all over the body.