Flies induced to be hungry, either by a specific diet or by brain stimulation, live longer.
- In flies, hunger was induced either by depriving them of branched-chain amino acids (BCAAs) or by stimulating their brain neurons associated with hunger.
- When insects ate a diet low in BCAAs throughout their lives, they lived longer.
- As for fruit flies exposed to red light, they also ate less and aged less quickly.
“Hunger modulates aging in Drosophila (i.e., three-millimeter flies)”, revealed scientists from the University of Michigan (USA). In order to reach this conclusion, they carried out a study published in the journal Science. “We sort of disentangled the effects of dietary restriction (on extending lifespan) from all the nutritional manipulations of the diet that researchers worked on for many years to say that they weren’t necessary. The perception of a lack of food is enough”, said Scott Pletcher, co-author of the work, in a statement.
Amino acid reduction induces a state of hunger that prolongs lifespan
As part of their research, the team induced starvation in flies in two ways. The first was to change the amount of branched-chain amino acid, or BCAA, in a snack, then let the flies feed freely on a buffet of yeast or sugary foods.
According to the results, flies fed the low branched chain amino acid snack consumed more yeast than sweet food compared to fruit flies fed the high BCAA snack. “This kind of preference for yeast over sugar is an indicator of craving-based hunger.”
According to the authors, this behavior is not caused by the calorie content of the snack, because these flies consumed more food and more total calories. When flies were on a low BCAA diet throughout their lives, they also lived much longer.
Creating an “insatiable hunger” that makes flies live longer
Next, the scientists used a technique called “optogenetics” to activate neurons associated with hunger in flies through exposure to red light. These fruit flies consumed twice as much food as the flies not exposed to the light stimulus. Insects exposed to red light also lived much longer. “We think we created a sort of insatiable hunger in the flies. Because of this, the flies lived longer,” explained Kristy Weaver, lead author of the study.
During their experiments, the team was also able to establish a link between the molecular mechanisms of hunger and changes in the epigenome of the neurons concerned. She identified that neurons respond to the presence or absence of a specific amino acid in the diet. These changes may affect the amount of specific genes expressed in fly brains and, therefore, their feeding behavior and aging. “We can think that the mechanisms discovered are likely to modulate food drives in other species”the researchers concluded.
