Adjusting a brain signalling pathway linked to insulin could be the key to longer life, say scientists.
Insulin is the vital hormone that tells the body how to regulate its use of sugar as fuel for cells.
Experiments with worms and flies have indicated that reducing insulin signalling lengthens lifespan. But in higher animals, including humans, this can lead to diabetes.
The new research, reported in the journal Science, suggests that a way round the problem might be to curb insulin signalling only in the brain.
Scientists used genetic engineering to interfere with insulin signalling in the brains of mice. They halved levels of a protein called Irs2 which carries the insulin signal within cells.
"To our surprise, all of the engineered mice lived longer," said Dr Akiko Taguchi, one of the scientists from Howard Hughes Medical Institute in Chevy Chase, Maryland, US.
Mice lacking Irs2 only in the brain lived 18% longer than normal.
Despite changes that might be expected to reduce lifespan, such as putting on weight and increased blood insulin levels, the mice appeared generally healthier. They remained more active as they aged, and their glucose metabolism resembled that of younger mice.
After eating, their brains had higher levels of a natural antioxidant that protects against damage by free radicals, highly reactive chemical agents which attack cells and DNA.
Dr Morris White, who runs the Boston laboratory where the research took place, said the findings could help explain why sensible diets and exercise are so beneficial. He also believes insulin-like signalling in the brain might promote age-related brain diseases. |
