Patients with hypogeusia show changes in expression of T2R taste receptor genes in their tongues

Objectives/Hypothesis: Taste receptor genes associated with bitterness belong to the T2R gene family. In this study, we compared the expression of genes of the T2R family in the tongues of patients with hypogeusia to those in healthy subjects and examined the possibility that T2R genes are involved in the pathogenesis of hypogeusia. Study Design: Prospective clinical and basic study. Methods: The control group consisted of 24 healthy people. The patient group consisted of 40 subjects with hypogeusia who were confirmed to have abnormally elevated taste thresholds including that of bitter taste. A tissue sample was collected from each individual by scraping the mucosa on the foliate papillae of the tongue. Total RNA was extracted from each sample and reverse transcribed. The expression of 10 T2R genes (TAS2R40, -R42, -R43, and -R48, and T2R3, -R8, -R9, -R10, -R13, and -R16) was evaluated by reverse transcriptase-polymerase chain reaction. Results: Comparison of the frequency of gene expression between the control group and patients with hypogeusia showed that the frequency of expression of six receptor genes were significantly reduced in the hypogeusia patients. In particular, TAS2R40 showed a significant and marked decrease in the frequency of expression regardless of the cause or severity of hypogeusia. Conclusions: Our results suggest that decreased expression of taste-associated genes may be involved in hypogeusia in humans. In addition, the evaluation of taste receptor gene expression may be useful clinically for an objective diagnosis of hypogeusia or to evaluate the severity of the disorder.