Specific odours that represent food or indicate danger trigger a small number of highly specialised sensory neurons that can alter an animal's lifespan and physiological profile, according to researchers at the University of Michigan, University of Houston, and Baylor College of Medicine.
Recent research in model organisms and in humans has shown that sensory experiences can impact a wide range of health-related characteristics including athletic performance, type II diabetes, and aging.
Nematode worms and fruit flies that were robbed of their ability to smell or taste, for example, lived substantially longer.
However, the specific odours and sensory receptors that control this effect on aging were unknown.
The researchers used molecular genetics in combination with behavioural and environmental manipulations, and successfully identified carbon dioxide (CO2) as the first well-defined odorant capable of altering physiology and affecting aging.
Flies incapable of smelling CO2 live longer than flies with normal olfactory capabilities.
They are also resistant to stress and have increased body fat. To many insects, including fruit flies, CO2 represents an ecologically important odour cue that indicates the presence of food (eg rotting fruit or animal blood) or neighbours in distress (it has been implicated as a stress pheromone).
The researchers previously showed that merely sensing one's normal food source is capable of reversing the health and longevity benefits that are associated with a low calorie diet.
They now establish that CO2 is responsible for this effect.
"We are working hard to understand how sensory perception affects health, and our new result really narrows the playing field. Somehow these 50 or so neurons, whose primary job it is to sense CO2, are capable of instigating changes that accelerate aging throughout the organism," said Scott Pletcher.
Sensory perception has been shown to impact aging in species that are separated by millions of years of evolution, suggesting that similar effects may be seen in humans.
"For us, it may not be the smell of yeast, for example, or the sensing of CO2 that affects how long we live, but it may be the perception of food or danger," said Pletcher.
If so, a clever program of controlled perceptual experience might form the basis of a simple yet powerful program of disease prevention and healthy aging.
The study has been published in the online, open-access journal PLoS Biology.
