Fruit-fly find may pave way for human 'longevity'

For years, scientists have engineered fruit flies whose genes can be turned on and off by a synthetic hormone, allowing detailed studies of the effects of single genes on life span. Many of the genes have close relatives in humans.

Unfortunately, the hormone used to perform the studies turns out to be anything but neutral.

Researcher John Tower at the USC Dornsife College of Letters, Arts and Sciences and lab member Gary Landis grew suspicious of the hormone that they and others were using to activate the genes mifepristone, a synthetic chemical known to terminate pregnancy in humans.

Many studies have shown that reproduction shortens lifespan in flies and other organisms and so researchers wondered if the hormone they were using could be affecting reproduction in flies, and in turn their life span.

They discovered that flies exposed to the hormone laid only half the usual amount of eggs - and lived 68 percent longer, from a median age of 56 to 94 days.

The mifepristone had little or no effect on the life expectancy of female flies that had not mated, which had an even better overall survival rate and maximum lifespan.

Tower added that this opens up a new line of inquiry for longevity studies, and identifies candidate genes and mechanisms for regulating the trade-off between reproduction and lifespan that may be shared with humans.

Tower noted that it does, however, mean that their earlier longevity studies that relied on mifepristone as a gene switch will need to be reevaluated.

The findings appear online in the journal Aging.