Posts tagged taste cells
Articles and news from the latest research reports.
Stress hormone receptors localized in sweet taste cells
According to new research from the Monell Center, receptors for stress-activated hormones have been localized in oral taste cells responsible for detection of sweet, umami, and bitter. The findings suggest that these hormones, known as glucocorticoids, may act directly on taste receptor cells under conditions of stress to affect how these cells respond to sugars and certain other taste stimuli.
"Sweet taste may be particularly affected by stress," said 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 intense stress."
Glucocorticoid (GC) hormones affect the body by activating 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.
The findings, published online ahead of print in the journal Neuroscience Letters, revealed that GC receptors are present on the tongue, where they are specifically localized to the cells that contain receptors for sweet, umami and bitter taste. 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 percent increase of GC receptors within taste cell nuclei.
Together, the results suggest 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," said Parker.
Parker 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 sally and sour taste. One explanation, he said, is that stress may influence salt taste processing in the brain.
Implications of the findings extend beyond the oral taste system. Noting that 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.
(Source: eurekalert.org)
Monell scientists identify elusive taste stem cells
Scientists at the Monell Center have identified the location and certain genetic characteristics of taste stem cells on the tongue. The findings will facilitate techniques to grow and manipulate new functional taste cells for both clinical and research purposes.
"Cancer patients who have taste loss following radiation to the head and neck and elderly individuals with diminished taste function are just two populations who could benefit from the ability to activate adult taste stem cells," said Robert Margolskee, M.D., Ph.D., a molecular neurobiologist at Monell who is one of the study’s authors.
Taste cells are located in clusters called taste buds, which in turn are found in papillae, the raised bumps visible on the tongue’s surface.
Two types of taste cells contain chemical receptors that initiate perception of sweet, bitter, umami, salty, and sour taste qualities. A third type appears to serve as a supporting cell.
A remarkable characteristic of these sensory cells is that they regularly regenerate. All three taste cell types undergo frequent turnover, with an average lifespan of 10-16 days. As such, new taste cells must constantly be regenerated to replace cells that have died.
For decades, taste scientists have attempted to identify the stem or progenitor cells that spawn the different taste receptor cells. The elusive challenge also sought to establish whether one or several progenitors are involved and where they are located, whether in or near the taste bud.
Drawing on the strong physiological relationship between oral taste cells and endocrine (hormone producing) cells in the intestine, the Monell team used a marker for intestinal stem cells to probe for stem cells in taste tissue on the tongue.
Stains for the stem cell marker, known as Lgr5 (leucine-rich repeat-containing G-protein-coupled receptor 5), showed two patterns of expression in taste tissue. The first was a strong signal underlying taste papillae at the back of the tongue and the second was a weaker signal immediately underneath taste buds in those papillae.
The Monell scientists hypothesize that the two levels of expression could indicate two different populations of cells. The cells that more strongly express Lgr5 could be true taste stem cells, whereas those with weaker expression could represent those stem cells that have begun the transformation into functional taste cells.
Additional studies revealed that the Lgr5-expressing cells were capable of becoming any one of the three major taste cell types.
The findings are published online in the journal Stem Cells.
"This is just the tip of the iceberg," said senior author Peihua Jiang, Ph.D., also a Monell molecular neurobiologist. "Identification of these cells opens up a whole new area for studying taste cell renewal, and contributes to stem cell biology in general."
Future studies will focus on identifying the factors that program the Lgr5-expressing cells to differentiate into the different taste cell types, and explore how to grow these cells in culture, thus providing a renewable source of taste receptor cells for research and perhaps even clinical use.
(Image: Getty)