Brown scientists link reproduction, aging

PROVIDENCE – Biologists at Brown University have found new evidence of a link between reproduction and lifespan, showing that fruit flies live longer when they don’t produce germline stem cells – the cells that create eggs and sperm.
The research, described in the latest issue of the Proceedings of the National Academy of Sciences, offers a glimpse into the molecular processes behind a long-known connection between reproduction and lifespan.
“When reproduction is delayed, animals live longer. Why? Our research suggests that signals from the reproductive system can regulate aging in animals – including, possibly, humans,” said Thomas Flatt, a postdoctoral research associate in the Department of Ecology and Evolutionary Biology at Brown, in a news release.
Ten years ago, the biologist Cynthia Kenyon, of the University of California, San Francisco, showed that eliminating germline stem cells in roundworms extended their lifespan. This time, Flatt and Marc Tatar, a Brown professor and the senior scientist on the project, did the same to fruit flies, aiming to show this was a general principle in biology.
Flatt and Tatar over-activated a gene that controls germline stem cells in flies, eliminating the cells’ production. The sterile flies lived 20 to 50 percent longer than typical flies.
Based on previous research findings, Flatt and Tatar believed the sterile flies might live longer because they are insensitive to the effects of insulin, a life-shortening hormone. But they discovered the flies’ brains were actually producing more insulin. Their bodies, however, responded as if there were less insulin present.
The scientists said a possible explanation for that paradox is that the insects’ gonads – their ovaries or testes – reacted to the increased insulin production by producing a protein that acts like a sponge, binding to the insulin and blocking its signals throughout the body.
“This suggests that the gonad and the brain are in a synchronized hormonal feedback loop,” Tatar said. “It’s not just the brain affecting the gonad, but also the other way around.”
“We think that in mammals, a similar communication occurs between the brain and the gonad, communication which controls insulin signaling,” Flatt said. “And when insulin signaling is reduced, the body goes into a state of high repair. The body becomes more stress resistant. Tissues protect themselves really well – and that increases longevity.”
The research was funded by the National Institute on Aging, The Howard Hughes Medical Institute, the Ellison Medical Foundation, the Roche Research Foundation, and the Swiss National Science Foundation.