Every cell has a sensor that keeps tabs on energy levels, the way a smart meter keeps tabs on the electricity in your house. When energy runs low, it switches to saver mode: the cell spends less and stores more. Scientists have long suspected that aging is tied to this sensor gradually losing its touch. Now there's a drug that essentially presses the sensor's button from the outside, making the cell think energy is scarce even though food keeps arriving as usual.
The drug is called MK-8722, and it was given to two kinds of animals: tiny worms and elderly mice. The worms that received it lived 13% longer than their counterparts without it. Crucially, they reproduced normally, so the extra lifespan didn't come at the cost of offspring. In mice that were 18 months old, roughly the human equivalent of 60, the drug slowed weight gain and kept blood sugar at youthful levels.
In the mice on the drug, daily metabolic swings stayed as sharp as they are in youth. Normally these rhythms blur with age: the body stops telling day from night, and metabolism drifts. The drug helped preserve that internal schedule. On top of that, levels of bile acids rose in the liver and kidneys, and one of them, lithocholic acid, is known for its rejuvenating effects.
So the pill mimics the effects of fasting without making the animal skip meals. That matters, because calorie restriction, though it does extend life, is hard to stick to and comes with side effects. If a safe drug can be built that flips the same switch, it could become a way to slow aging without grueling diets. That said, the mice on the drug showed slightly enlarged hearts and kidneys, and it's still unclear whether that's dangerous over the long haul.
The study confirms that the cellular energy sensor is one of the prime targets in the fight against aging. Someday doctors may prescribe drugs like this to older people to push back age-related disease. But first we need to know whether flipping that sensor for years on end is safe.
Lithocholic acid, whose levels rose in mice on MK-8722, was recently recognized as a powerful geroprotector: giving it to old mice reproduced many of the effects of calorie restriction and extended lifespan.
In Peter Watts's novel Blindsight, vampires have a super-efficient metabolism that lets them survive on minimal resources. AMPK activation, as in this work, is a step toward similar metabolic thrift, though without the vampire genes.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.