A gene called tobi (target of brain insulin) increases and decreases in level depending on the amount of protein and sugar present in flies, German researchers have found.
Tobi encodes an evolutionarily conserved a-glucosidase enzyme that converts stored glycogen into glucose.
The findings of this research might shed light on the way the insects' bodies and perhaps those of humans too, handle dietary extremes, including high-protein, low-carb diets like the Atkins.
In fact, the study led by Michael Pankratz of Forschungszentrum Karlsruhe in Germany, who is now at the Fritz Lipmann Institute, may provide new clues about the links between diet and life span.
"This gene is activated by high protein and repressed by sugarThe question is: Why would the body need such a mechanism for releasing glucose under specific dietary conditions," said Pankratz.
Also, Pankratz said that high-protein diet may lead to insulin release which stimulates cells to take in sugar from the bloodstream against common belief that insulin is only linked to sugar. As little to no sugar is coming in, this can lead to hypoglycemia, or low blood sugar. Thus, the body needs a second mechanism to release glucose from glycogen.
"We think this is what's happening [in the flies]. It's a sensitive mechanism for dealing with extreme dietary conditions," he said.
The researchers explained that in mammals, one of the most important systems for controlling metabolism consists of the antagonistic actions of insulin and glucagon, which is not strict since amino acids boost both insulin and glucagon secretion.
In the new study, the researchers were led to tobi by analyzing changes in gene activity in flies lacking insulin-producing cells. Also, tobi levels increased when flies consumed a protein-rich yeast paste and decreased when the insects ate a sugary concoction. This tobi expression pattern is quite similar to hormone glucagon in mammals and indicates that the gene may be controlled by an analogous hormone.
It was shown in previous studies that flies lacking insulin-producing cells (which also express lower tobi levels) live longer and this was also found to be true in the current study but only in flies fed the high-protein diet. However, tobi's exact role in life span will needs to be found out through further study.
"The current study indicates that proteins may have a greater effect than sugars on insulin signaling, and evidence is growing that quality and not only quantity of calories taken in has an influence on life span. Therefore, teasing apart the relative contributions of dietary proteins and sugars in insulin signaling should prove insightful," the researchers said.
The study is published in the recent issue of Cell Metabolism.