Sexual frustration increases stress, hastens ageing and shortens life span in flies. When male flies sense female fly pheromones, they lose fat stores, are less able to cope with starvation and don’t live as long as unexposed males. Allowing the males to actually mate with females reverses these negative metabolic and ageing effects.
Since the energy required for mating and reproduction can itself affect ageing and longevity, this study was done by exposing male flies to other males that had been genetically engineered to express female pheromones. Or exposing females to females drenched in male pheromone. When flies were exposed to pheromones of the opposite sex, they didn’t live as long as unexposed flies. The way they metabolised fat was dramatically changed, as was their ability to deal with the stress of starvation. These effects were worse in the male than the female flies. The males still showed these changes even if they were only exposed to purified female pheromone and not pheromone-secreting animals. Removing the offending pheromones or the feminised males completely reversed these effects.
Flies have taste bristles on their mouthparts, legs, and wings. If males were altered so they could no longer taste, they were not affected by female pheromones. If taste was restored just on legs and wings, but not mouth, the pheromones again caused havoc. If the forelegs were removed, flies were again protected. So flies taste pheromones using their legs.
The clincher of this study was when the males that had tasted the female pheromone-secreting males were allowed to mate with females. The metabolic and ageing changes were completely reversed by a bit of hanky panky.
What does this have to do with human ageing? Well, Neuropeptide F was found to be essential for the pheromone effects in flies. When neurons that express neuropeptide F were activated in male flies, these flies had a shorter life span than untreated flies, even when they weren’t exposed to female pheromones. Pheromone exposure in flies altered many of the genes which control immunity, stress response and ageing. This may be through neuropeptide F. Humans have a similar molecule in our brains called neuropeptide Y. It regulates food intake and fat storage, and reduces anxiety, stress and pain perception. A similar signalling pathway may occur in humans through neuropeptide Y. So maybe hanky panky is keeping us young.