The sweet life is no metaphor for fruit flies, according to new research that finds the ability to sense certain tastes can alter the life span in these tiny insects.
Sweet tastes contributed to a longer life span, two new studies found, and bitter tastes to a premature death. And, oddly, flies that couldn't taste water lived 43 percent longer than flies that could.
Fruit flies (Drosophila melanogaster) are not the only organisms whose taste buds affect their life span. The nematode worm Caenorhabditis elegans also sees its life span shrink and stretch depending on its ability to detect various tastes. Researchers hope the findings in these research organisms will inform studies on human health.
"Our world is shaped by our sensory abilities that help us navigate our surroundings, and by dissecting how this affects aging, we can lay the groundwork for new ideas to improve our health," Joy Alcedo, a biologist at Wayne State University in Detroit, Michigan, who led one of the studies, said in a statement. [Extending Life: 7 Ways to Live Past 100]
Alcedo's study examined the effect of removing taste receptors from the legs, wings and mouthparts of fruit flies. Previous studies had found that turning off certain smell receptors in fruit flies alters their life spans, and Alcedo and colleagues wanted to know if the same was true for taste.
The researchers found that when they tested mutant flies bred to lack mouth taste receptors, the flies' life spans went up. But when the flies also lacked leg and wing receptors, the result was the opposite: lifespans went down. This indicated that taste receptors could influence life span both for better and for worse.
The researchers tested to see if the flies without receptors were altering their food intake, and found they were not. However, a chemical signal in the brain called dFOXO, which regulates the use of insulin, appeared to play a role, Alcedo and colleagues concluded in their study, detailed today (May 19) in the journal Proceedings of the National Academy of Sciences.
The results follow another study published on May 12 in the same journal, which looked at specific tastes in more detail. That study, conducted by many of the same researchers, found that flies bred to lack the ability to taste water increased their storage of fat and sugar, which in turn increased their life spans. The changes appeared to be adaptations to dry conditions, as flies that couldn't taste water were resistant to drying out and retained more water in their tissues than flies that could taste water.
The researchers aren't yet clear on why bitter and sweet tastes alter life span, but plan further study.
Taste buds are known to attract organisms to certain foods, ensuring that creatures are motivated to ingest nutrients, Scott Pletcher, a professor of molecular and integrative physiology at the University of Michigan and one of the authors of the May 12 study, said in a statement. The new findings point to an expanded role of taste buds, Pletcher said.
"It turns out that taste buds are doing more than we think," he said.