Anosmia and dysgeusia among COVID-19 patients are associated with low levels of serum Glucagon-like peptide 1 (GLP-1)

Purpose: Anosmia and dysgeusia (AD) are common among COVID-19 patients. These symptoms are not frequently associated with rhinorrhea or nasal congestion and the underlying mechanism is unclear. Previous reports suggested that Glucagon-like peptide-1 (GLP-1) signaling plays a role in the modulation of olfaction and geusia. We aimed to assess the correlation between GLP-1 and COVID-19-associated AD. Methods: Blood samples obtained from COVID-19 patients with and without AD were tested for serum GLP-1 levels using enzyme-linked immunosorbent assay (ELISA). A second control group comprised of COVID-19-negative volunteers. Results: Forty-nine subjects were included in the study. Nineteen were positive for COVID-19. Of the 19 patients, ten had AD and nine declined such complaints. Age and basic metabolic rate were similar among all study groups. Serum GLP-1 levels were significantly lower among patients with AD as compared with patients without AD and COVID-19-negative individuals (1820 pg/ml vs 3536 pg/ml vs 3014 pg/ml, respectively, p<0.02). Conclusion: COVID-19 patients who reported of AD had lower serum levels of GLP-1 as compared with those lacking AD symptoms and COVID-19-negative individuals. These results suggest that GLP-1 may be involved in the pathogenesis of AD. However, further larger scale studies should corroborate our findings