A new study presents the first direct biological evidence that helps explain why some people remain tasteless long after recovering from Covid-19.
A team of researchers has identified specific changes in taste buds that may shed light on why a small number of patients maintain Difficulty sensing flavors long after a SARS-CoV-2 infection.
O, published in the magazine Chemical Sensesis the first to directly link persistent complaints of altered taste to measurable abnormalities within the cells responsible for detecting flavors.
To explore the origin of long-term taste disturbances, scientists from the University of Colorado Anschutz and two universities in Sweden analyzed 28 non-hospitalized people who reported changes in taste more than a year after having Covid-19.
According to the study authors, 8 out of 28 patients presented clearly abnormal results in taste tests, and 11 patients reported specific loss of taste. sweet, bitter and umami flavors. The salty and acidic flavors remained, to a large extent, preserved.
To better understand the biological basis of these symptoms, the team collected taste bud biopsies of 20 participants.
The team, led by Göran Hellekantresearcher at the University of Wisconsin and the Swedish University of Agricultural Sciences, found lower levels of messenger RNA (mRNA) in certain taste receptor cells.
This mRNA is needed to make a protein called PLCβ2which plays a central role in the transmission of taste signals associated with sweet, bitter and umami flavors.
“PLCβ2 functions as a molecular amplifier within taste cells,” he said. Thomas Fingerprofessor of cell biology at the University of Colorado Anschutz and corresponding author of the study.
“It strengthens the signal before it is transmitted to the brain. When levels decrease, the taste signal weakens”, adds the researcher, cited by .
Cells that detect salty and acidic tastes use different signaling mechanisms and do not depend on PLCβ2. This difference may explain why these flavors were, in general, little affected in the participants.
In addition to the molecular results obtained in the study, microscopic analysis revealed physical differences in taste buds of some patients. While several participants had typical-looking tissue under the microscope, others showed visible disorganization in the structure of the papillae.
“Some participants had normal-looking taste buds, while others had structural disorganization“, says Finger. “This suggests that both molecular and architectural changes may contribute to persistent taste dysfunction.”
Altogether, the results point to the possibility that prolonged taste disturbance results from a combination of faults in cell signaling and changes in tissue organization.
Under normal conditions, taste bud cells regenerate every two to four weeks. However, the study found evidence that, in some people, disruptions in underlying signaling pathways may last much longer.
Most people who lose their sense of taste during Covid-19 recover quickly. weeks or months. This research offers measurable biological evidence that helps explain why recovery may be slower in a smaller group of patients.
“Our results offer measurable evidence of long-term taste disturbance in some post-Covid patients, long after the virus has been eliminated,” the authors write.
The researchers emphasize that further work is needed to understand whether these molecular changes can be fully reversed and whether future treatments can help restore normal taste signaling.
