When a human gets really hungry, a handful of nuts, a nice tasty steak or a piece of trick may really hit the spot, but when a fruit fly gets hungry, a nibble of yeast will do the trick.
A question that ought to be asked is: why do we and those flies that invade our kitchens seek out foods that are full of protein when we are hungry? And what does that preference mean for the odds of living a longer life, whether it’s measured in decades for a human, or days for a fly?
As suggested for the first time by new research from the university of Michigan medical school team, a brain chemical may have a lot to do with both questions asked above.
U-M scientist Scott Pletcher, Ph.D., and his team demonstrate in a new paper in the journal eLife, the key role that the chemical called serotonin plays in the feeding habits and life spans of fruit flies. The first author of the paper is Jennifer Ro, Ph.D., who is now at Harvard Medical School.
Reward in the brain
Serotonin which is called the “reward” chemical is called so because when it is released in the brain in response to a action, it travels between brain cells and produces a sense of reward or even pleasure.
According to Pletcher and his team, it appears to play a key role in fruit flies’ strong tendency to seek out protein, not sugars, when they’ve been deprived of food for a while. This in other words means that it affects the value flies place on protein at that time which tells how flies figure out which foods contain protein in the first place.
How quickly the flies aged appears to be influenced by the brain-based reward that the flies get from eating protein. Flies lived far longer when that reward was blocked, but the flies ate just as much food as before. Just from blocking a single serotonin receptor found on the surface of only about 100 neurons in their brains, they lived twice as long.
Pletcher notes that the serotonin reward system in fruit flies is very similar to that in mammals including humans even though it is far too soon to apply their findings to our understanding of human feeding patterns or longevity.