Sometimes it feels like the chocolate calls out to us when we feel stressed out or upset, and it does provide the comfort we seek. Now, researchers from the Monell Chemical Senses Center in Philadelphia may have discovered why this is. In a new study, receptors for stress-activated hormones (known as glucocorticoids (GCs)) have been found located in oral taste buds that are responsible for detecting sweet, umami and bitter tastes.
The research team, led by M. Rockwell Parker, PhD, has published their findings in the journal Neuroscience Letters.
According to the researchers, stress can increase the secretion of GCs, which then activate specialized GC receptors located inside of cells. Knowing that stress can have major effects on metabolism and food choice, the researchers used a mouse model to ask whether taste receptor cells contain these GC receptors.
"Sweet taste may be particularly affected by stress," says lead author M. Rockwell Parker, PhD, a chemical ecologist at Monell. "Our results may provide a molecular mechanism to help explain why some people eat more sugary foods when they are experiencing proper stress."
The findings revealed that the highest concentrations of GC receptors were found in Tas1r3 taste cells, which are sensitive to sweet and umami taste.
GC hormones act on cells via a multi-step process. After GCs bind to their receptors within target cells, the activated receptor complex moves, or translocates, to the cell nucleus, where it then influences gene expression and protein assembly.
To explore whether GC receptors in taste tissue are activated by stress, the researchers compared the proportion of taste cells with translocated receptors in stressed and non-stressed mice. Compared to controls, the stressed mice had a 77% increase of GC receptors within taste cell nuclei.
Together, the results suggested that sweet taste perception and intake, which are known to be altered by stress, may be specifically affected via secretion of GCs and subsequent activation of GC receptors in taste cells.
"Taste provides one of our initial evaluations of potential foods. If this sense can be directly affected by stress-related hormonal changes, our food interaction will likewise be altered," explains Parker.
He also noted that although stress is known to affect intake of salty foods, GC receptors were not found in cells thought to be responsible for detecting salty and sour tastes. One explanation, he said, is that stress may influence the processing of salt taste in the brain.
Implications of the findings extend beyond the oral taste system, as taste receptors are found throughout the body. Senior author and Monell molecular neurobiologist Robert Margolskee, MD, PhD, said, "Taste receptors in the gut and pancreas might also be influenced by stress, potentially impacting metabolism of sugars and other nutrients and affecting appetite."
Future studies will continue to explore how stress hormones act to affect the taste system.