Nikhil Prasad Fact checked by:Thailand Medical News Team Nov 16, 2024 1 month, 15 hours, 57 minutes ago
Medical News: For millions recovering from COVID-19, the virus leaves behind more than just memories of fever and fatigue. Many survivors report taste disturbances, particularly in the form of bitter taste dysfunction, a hallmark symptom of long COVID. Researchers from Indiana University School of Dentistry-USA and Purdue University-USA sought to uncover the biological roots of these symptoms, identifying key salivary proteins that may play a crucial role.
Long COVID Study Links Bitter Taste Loss to Reduced Salivary Proteins
Schematic representation of suggested mechanism for taste dysfunction in long COVID. In healthy people, non-lingual epithelial cells and taste cells exhibit a turnover of 14–21 days and 8–10 days, respectively. These cells constitute the oral exfoliome. In long COVID, the changes induced in the biofilm following CoV-2 infection mediate chronic inflammation and disrupt the balance between taste and non-taste cell proliferation and exfoliation, shifting the balance towards increased taste cells in the exfoliome, consequently leading to taste dysfunction. Representative positive taste cell marker cells are shown.
This
Medical News report dives into the findings of the study, revealing how reduced levels of proteins like gustin and statherin in saliva correlate with impaired taste perception in long COVID sufferers. These insights provide new avenues for understanding the condition and its impact on daily life.
Key Findings: Proteins That Define Taste
The study examined the role of salivary proteins, including gustin (also known as carbonic anhydrase VI) and statherin, in maintaining healthy taste functions. Gustin is known to regulate the environment around taste buds, while statherin contributes to biofilm formation, influencing oral health and sensory perception. Sonic hedgehog (SHH), another protein studied, helps regulate the proliferation and differentiation of taste cells.
Bitter Taste Dysfunction Dominates Long COVID Cohort
Researchers observed that among the 30 long COVID participants, bitter taste impairment was the most prevalent dysfunction. Approximately 26% of those who had COVID-19 more than once experienced bitter taste loss, compared to 16% of those with a single infection. Sweet taste dysfunction was also noted but was less frequent.
The findings also showed significantly lower gustin levels in participants with bitter taste loss, suggesting a direct link between protein concentration and taste sensitivity.
Salivary SHH and Cellular Turnover
Salivary SHH levels, while not statistically significant, showed a decline in individuals experiencing bitter taste dysfunction. SHH plays a critical role in maintaining taste cell turnover, and disruptions in this balance can lead to taste perception issues. Cellular analysis revealed an increased presence of epithelial cells in the saliva of long COVID sufferers, pointing to accelerated cell ex
foliation and a possible mechanism for taste dysfunction.
Inflammation and Immune Markers in Taste Alteration
The researchers also explored the role of inflammatory markers in the saliva of long COVID patients. Elevated levels of certain cytokines, such as IL-6 and IFN-γ, were detected alongside an increase in innate immune markers like sCD14. This suggests that ongoing inflammation, even after the acute phase of infection, might exacerbate taste dysfunction.
Interestingly, the bitter taste receptor gene TAS2R38 was expressed at higher levels in long COVID participants compared to controls. This gene is linked to the perception of bitter flavors and may play a role in the inflammation-induced taste alterations observed in the study.
What Does This Mean for Long COVID Patients?
Taste dysfunction, particularly the loss of bitter perception, can significantly impact quality of life. Foods may taste bland or unpalatable, leading to poor nutrition and further health complications. Understanding the biological underpinnings, as revealed by this study, opens pathways to developing targeted therapies or interventions.
For instance, boosting gustin levels in saliva or addressing inflammatory pathways could help restore normal taste function. Additionally, the study’s findings highlight the importance of oral health in managing long COVID symptoms, given the interplay between saliva, microbiota, and taste perception.
Study Limitations and Future Directions
While groundbreaking, the study has limitations. The small sample size means the findings should be interpreted cautiously. Researchers also noted the need for longitudinal studies to assess how taste dysfunction evolves over time in long COVID sufferers. Further exploration into the relationship between systemic inflammation and taste disturbances could provide deeper insights.
Conclusion: A Step Towards Recovery
This research underscores the intricate relationship between saliva and taste, shedding light on how long COVID disrupts this balance. By identifying reduced levels of gustin and SHH in saliva, the study not only explains the mechanism behind bitter taste dysfunction but also sets the stage for innovative treatments. These findings bring hope to those grappling with lingering symptoms, offering a path to reclaiming one of life’s simplest pleasures - flavor.
The study findings were published in the peer-reviewed Journal of Clinical Medicine.
https://www.mdpi.com/2077-0383/13/22/6816
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https://www.thailandmedical.news/news/bitter-and-sweet-taste-receptors-tas1rs-and-tas2r38-genetic-variations-play-a-role-in-covid-19-symptoms-and-severity
https://www.thailandmedical.news/news/breaking-medical-experts-say-that-anosmia-which-is-the-loss-of-smell-and-ageusia-which-is-loss-of-taste,-could-be-signs-of-covid-19-infection-
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