An antidepressant used in humans can extend the life span of tiny worms by about 30 percent, according to a new finding that has intrigued scientists who study aging.
The worms, called C. elegans, normally live for just a couple of weeks. But Linda Buck, a scientist at the Fred Hutchinson Cancer Research Center in Seattle, wanted to see if she could use chemicals to make the worms live longer. So her lab bought a large, random assortment to try.
"The 100,000 chemicals that we bought were just diverse chemicals that were collected from many sources by a chemical company," Buck said. "We didn't even know what they were when we were testing them."
The lab ended up testing more than 80,000 chemicals. Each one was put into a small container of liquid that was home to about a dozen worms. Researchers in the lab then had to keep watch, to see how the tiny worms fared.
"They shake them up, and they shine some light on them, and so they look for movement," Buck said. "And that's how they decide whether they're alive or not."
In the journal Nature, the scientists report that more than 100 chemicals increased the worms' life span — sometimes by a lot. One of those substances turned out to be very similar to an antidepressant called mianserin. The lab found that mianserin could extend the worms' lives by about 30 percent.
Buck cautions that mianserin is not one of the commonly prescribed SSRIs (selective serotonin reuptake inhibitors), such as Prozac. Her lab tested several of those drugs and did not see any effect on the worms. She does not want people to think they should ask their doctors for mianserin, thinking it will make them live longer.
"I would not suggest that the drug has similar effects in humans. It could have the opposite effect, for all we know," she said. "I think it will be a long time before anyone can determine what the effects on humans might be."
Buck's lab wants to start by seeing if the drug will also extend the life of mammals, such as mice. She also hopes to discover exactly how the drug has its effect on worms.
There are some hints that the drug may be affecting brain chemistry in a way that makes the worms feel like they're starving. That's important because scientists have known for a long time that worms that really are starved live longer.
Caloric restriction also extends life in other animals, so it is of interest to scientists such as Leonard Guarente, a biologist at Massachusetts Institute of Technology who investigates aging. He said many researchers have been working to target specific genes involved in caloric restriction, but he appreciates that Buck has taken a totally different approach.
"The fact that they screened through this large chemical library is kind of a tour de force," Guarente said. "And the fact that they converged on something, and that it's something surprising, is really quite striking."
Guarente said it is too soon to know what the finding means, but he said studies like this one help to make the idea of a life-extending pill seem less far-out.