Taste receptors for bitter substances are not only found on the tongue but also in the cells outside the oral cavity. As a new study at the Leibniz Institute for Food Systems Biology at the Technical University of Munich now shows, extraoral bitter taste receptors can also serve as endogenous sensors for bile acids.
This discovery suggests that, in addition to food components, endogenous components may have influenced the evolution of bitter taste receptors. In addition, the study provides new methods to assess the health effects of food ingredients in which bitter taste receptors are involved.
As taste sensors, bitter taste receptors serve to detect and avoid potential food toxins. Relatively recent findings also show that bitter taste receptors are also found in cells of the lungs, brain, and gastrointestinal tract, and in blood and sperm cells. A fact that suggests additional, less studied functions of the receptor are in the body, especially since the human body also produces bitter substances itself.
Based on these findings, the question arises whether bitter taste receptors evolved primarily as taste receptors or are more endogenous sensors that interact with endogenous bitters. component. The latter, of course, requires that the concentrations of endogenous components in the corresponding body fluid are sufficient to activate endogenous bitter taste receptors in extraoral tissues and cells.
Bile acids are endogenous bitter substances
Bile acids are a good example of endogenous bitter substances and are present in various body fluids. Therefore, a team led by Maik Behrens from the Leibniz Institute in Freising, Germany, investigated which of the approximately 25 human bitter taste receptor types respond to physiologically relevant concentrations of bile acid. For this purpose, the team used an established cellular test system and combined the experiments available with molecular modeling methods. The eight bile acids tested include primary, secondary, tertiary, and conjugated bile acids. The study was published in the journal Biology of Communication.
As the team showed, five types of bitter taste receptors responded to the bile acids tested. “In this context, the measured activation thresholds of the receptors are very consistent with the bile acid concentrations reported for human body fluids in the literature,” says Florian Ziegler, a doctoral student at the Leibniz Institute. contributed a lot to the study.
“Furthermore, we not only identified the binding of bile acids to the bitter taste receptor TAS2R1 through modeling studies but also reproduced the differences in the experimental activity data,” added Antonella Di Pizio, who heads the Molecular Modeling group at the Leibniz Institute.
Bile acids activate extraoral bitter taste receptors
“Our results suggest that there is a physiological relationship between bile acid and some extraoral bitter taste receptors and that the latter act as endogenous sensors of bile acid levels. They also support the hypothesis that not only external factors such as bitter food components influence the evolution of bitter taste receptors, but also endogenous ones,” said principal investigator Maik Behrens.
However, further studies are urgently needed to clarify the exact biological functions of extraoral receptors, continued the biologist. He added, “Gaining a deeper understanding of these functions will provide valuable insights into the potential health effects of food ingredients when they interact with the extraoral bitter taste receptor ligand system.”
More information:
Florian Ziegler et al, Physiological activation of human and mouse bitter taste receptors by bile acids, Biology of Communication (2023). DOI: 10.1038/s42003-023-04971-3
Provided by the Leibniz Institute for Food Systems Biology
Citation: Bitter taste receptors may serve as endogenous sensors for bile acids, study suggests (2023, July 3) retrieved 4 July 2023 from https://phys.org/news/2023-07-bitter-receptors -endogenous-sensors-bile. html
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