Scientists have provided the first evidence of a hormone-based aging mechanism they suggest may promote long life in species ranging from roundworms to humans. The mechanism begins in the brain with a mutant gene that suppresses the release of hormones that prompt rapid aging.
This is the first evidence of the way this aging mechanism works, said lead investigator Marc Tatar, of Brown University. It appears that aging is hormonally regulated, with a brain-based pathway that affects general hormones that come from a pituitary-like system.
The researchers studied a gene with function in the brain and other cells, called an insulin-like receptor (InR). The gene is analogous to those in species from top to bottom of the animal kingdom.
Fly InR responds to a form of insulin. As a result, brain cells tell a thyroid- or pituitary-like system to release a second hormone called juvenile hormone. This compound circulates in the body, unleashing a chain of other events that trigger reproduction and rapid aging.
The researchers bred fruit flies with mutant InR. They believed the mutation suppressed the release of juvenile hormone, arresting the aging process. Indeed, the breeding experiment produced dwarf females with life spans extended by up to 85 percent. Dwarf males also resulted, but they were generally frail and most died by 20 days. Males that survived to 20 days had low subsequent death rates. To test whether mutant InR had suppressed juvenile hormone, the researchers administered juvenile hormone to treat the long-lived flies. The treatment restored typical life expectancy to the insects.