Scientists have found molecular and structural changes in the taste buds of people who have recovered from COVID-19. Researchers at the University of Colorado Anschutz Medical Campus, working with Swedish colleagues, have identified an explanation for prolonged taste loss after coronavirus infection, infohub.kz reports.
The study, published in the journal Chemical Senses, involved 28 people whose taste perception problems persisted for more than a year after recovery. None of the patients had been hospitalized during their illness.
Participants had difficulty recognizing sweet, bitter and umami tastes, while their sensitivity to salty and sour tastes remained unchanged. Analysis of taste bud tissue samples from 20 people showed reduced levels of the messenger RNA responsible for producing the PLCβ2 protein.
According to Professor Thomas Finger, the PLCβ2 protein acts as a molecular amplifier inside taste cells. It boosts the signal sent to the brain when sweet, bitter and umami tastes are detected. When this protein is in short supply, the transmitted impulses become too weak. Cells responsible for perceiving sour and salty tastes use other transmission mechanisms that do not depend on PLCβ2, so their function is not impaired.
In addition to molecular disruptions, microscopic examination revealed abnormalities in the physical structure and arrangement of cells in patients' taste buds. Taste bud cells normally regenerate every two to four weeks, but the defects identified may persist for much longer. The authors believe the findings represent the first measurable biological evidence of long-term damage to the taste perception system in people who have recovered from COVID-19.