Impact of bitter taste receptor phenotype upon clinical presentation in chronic rhinosinusitis

TAS2R38 Bitter Taste Receptor Polymorphisms in Patients with Chronic Rhinosinusitis with Nasal Polyps Preliminary Data in Polish Population

Chronic rhinosinusitis (CRS) affects 5-12% of the general population, and the most challenging patients are those with nasal polyposis (CRSwNP). Its complexity, unpredictability, and difficulties in selecting a treatment plan individually for each patient prompted scientists to look for possible genetic causes of this disease. It was proven that single nucleotide polymorphisms (SNPs) in the TAS2R38 gene may affect the mobility and the activity of the ciliated epithelium of the upper respiratory tract what can contribute to individual differences in susceptibility to CRS. There are two common haplotypes: a "protective" type (PAV), and a "non-protective" type (AVI). CRS patients who are homozygous PAV/PAV are considered as less susceptible to the severe course of the disease, whereas patients with AVI/AVI haplotype are more vulnerable. The aim of this study was to examine TAS2R38 gene polymorphisms among CRSwNP patients and control group (N = 544) with the evaluation of the association between the distribution of studied polymorphic variants and the incidence as well as severity of CRSwNP in the study group. Whole blood samples from CRSwNP patients (N = 106) and the control group (N = 438) were analyzed for alleles of the TAS2R38 gene using real-time PCR single nucleotide polymorphism genotyping assays for rs713598, rs1726866, and rs10246939. PAV (SG: 41%; CG: 49%) and AVI (SG: 59%; CG: 51%) haplotypes were the only ones detected in the study. The AVI haplotypes were 1.5 times more frequent in the study group than in the control group (p = 0.0204; OR = 1.43). AVI/AVI individuals tended to have more severe symptoms in the VAS scale, less QoL in the SNOT-22 test, and a bigger nasal obstruction upon endoscopic examination. Patients with PAV/PAV were twice more likely to have minor changes in preoperative CT scans (p = 0.0158; OR = 2.1; Fi = 0.24). Our study confirmed that the PAV/PAV diplotype might have some protective properties and carrying the AVI haplotype might predispose to the development of CRSwNP.

Effect of Functional Endoscopic Sinus Surgery on Gustatory Function in Patients With Chronic Rhinosinusitis

OBJECTIVES

In this study, we investigated the effect of functional endoscopic sinus surgery (FESS) on gustatory function in patients with chronic rhinosinusitis (CRS).

METHODS

Forty-three patients with CRS who underwent FESS were included in this study. Prior to FESS and 3 months after surgery, the severity of rhinosinusitis was assessed using the Taiwanese version of the 22-item SNOT (SNOT-22), endoscopic examination, and acoustic rhinometry. The olfactory function was evaluated using the phenylethyl alcohol odor detection threshold test and the traditional Chinese version of the University of Pennsylvania Smell Identification Test, and the gustatory function was evaluated using the whole mouth suprathreshold taste test (WMTT) and the taste quad test (TQT). Subgroup analyses were performed based on CRS phenotypes and endotypes.

RESULTS

The SNOT-22 significantly improved 3 months after FESS for all patients with CRS. The endoscopic score and olfactory function significantly improved in patients with eosinophilic CRS and in patients with nasal polyps (CRSwNP). The WMTT sweet and bitter scores were significantly lower after FESS in CRSwNP, but the TQT sweet score was significantly higher in patients without nasal polyps. In addition, patients with noneosinophilic CRS had significantly decreased WMTT and salty scores 3 months after FESS.

CONCLUSION

Our results showed that the effect of FESS on gustatory function of patients with CRS was different with the different testing procedures, the association with nasal polyps, and the underlying inflammatory patterns.

Clinical Associations of Bitter Taste Perception and Bitter Taste Receptor Variants and the Potential for Personalized Healthcare

Bitter taste receptors (T2Rs) consist of 25 functional receptors that can be found in various types of cells throughout the human body with responses ranging from detecting bitter taste to suppressing pathogen-induced inflammation upon activation. Numerous studies have observed clinical associations with genetic or phenotypic variants in bitter taste receptors, most notably that of the receptor isoform T2R38. With genetic variants playing a role in the response of the body to bacterial quorum-sensing molecules, bacterial metabolites, medicinal agonists and nutrients, we examine how T2R polymorphisms, expression levels and bitter taste perception can lead to varying clinical associations. From these genetic and phenotypic differences, healthcare management can potentially be individualized through appropriately administering drugs with bitter masking to increase compliance; optimizing nutritional strategies and diets; avoiding the use of T2R agonists if this pathway is already activated from bacterial infections; adjusting drug regimens based on differing prognoses; or adjusting drug regimens based on T2R expression levels in the target cell type and bodily region.

Chronic Rhinosinusitis: T2r38 Genotyping and Nasal Cytology in Primary Ciliary Dyskinesia

OBJECTIVES

Chronic rhinosinusitis (CRS) is a major hallmark of primary ciliary dyskinesia (PCD). We investigated the possible correlation between some severity markers of CRS and several clinical features of the disease. We further studied the bitter taste receptor TAS2R38 polymorphisms to identify the genotypes associated with more severe disease.

METHODS

We included 39 adult PCD patients with (CRSwNP) and without nasal polyposis (CRSsNP); a sample for nasal cytology was obtained and clinical cytological grading (CCG) was determined. The SNOT-22 and Lund-Mackay scores were recorded. A sample of DNA was extracted from peripheral blood to investigate TAS2R38 polymorphisms.

RESULTS

CRSwNP patients had features of more severe disease: indeed, they had statistically significantly higher frequency of previous sinus surgery, higher SNOT-22, LM scores, and CCG than CRSsNP patients. Upon genotyping of TAS2R38 polymorphisms, we observed that the AVI-AVI genotype, associated to homozygous nonfunctional bitter TAS2R38 receptor, was more prevalent among CRSwNP (100%) than in CRSsNP patients (0%); furthermore, AVI-AVI subjects showed statistically significantly worse SNOT-22 and CCG scores than PAV-PAV and PAV-AVI subjects. The group of AVI-AVI patients also had more frequent respiratory exacerbations, Gram-negative infections, and Pseudomonas aeruginosa colonization than PAV-PAV and PAV-AVI patients.

CONCLUSION

Our findings indicate for the first time that PCD patients with CRSwNP display a more severe disease than those with CRSsNP. Genotyping of TAS2R38 polymorphisms demonstrated that in PCD patients, the AVI-AVI genotype is strikingly more prevalent among CRSwNP than in CRSsNP, while the PAV-PAV genotype might be protective against Gram-negative infections and respiratory exacerbations.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:248-254, 2023.

TAS2R38 Bitter Taste Receptor Expression in Chronic Rhinosinusitis with Nasal Polyps: New Data on Polypoid Tissue

Studies have shown differences in TAS2R38 receptor expression in patients with chronic rhinosinusitis (CRS) compared to healthy controls. Known agonists of TAS2R38 stimulate epithelial cells, leading to robust intracellular nitric oxide (NO) production, which damages bacterial membranes, enzymes, and DNA, but also increases ciliary beat frequency. In this study we examined, using qRT-PCR, the expression of TAS2R38 receptor in nasal polyps (NP) of patients with CRS (N = 107) and in inferior turbinate mucosa (ITM) of patients with CRS and controls (N = 39), and confronted it with clinical features and the severity of the disease. The expression was shown in 43 (50.00%) samples of ITM in the study group (N = 107), in 28 (71.79%) in the control group (N = 39) (p = 0.037), and in 43 (46.24%) of NP. There were no differences in levels of the expression in all analyzed tissues. Patients who rated their symptoms at 0–3 showed higher TAS2R38 expression in ITM in comparison to the patients with 8–10 points on the VAS scale (p = 0.020). A noticeable, however not significant, correlation between the TAS2R38 expression in ITM and the Lund–Mackay CT score was shown (p = 0.068; R = −0.28). Patients with coexisting asthma had significantly higher receptor expression in the NP (p = 0.012). Our study is the first to confirm the presence of the TAS2R38 receptor in NP. Expression of the TAS2R38 receptor is reduced in the sinonasal mucosa in patients with more advanced CRS with NP.

Taste receptors in CRS, what is the evidence?: a systematic review

BACKGROUND

Bitter (T2Rs) and sweet (T1Rs) taste receptors are involved in the innate immune response of the sinonasal cavity and associated with chronic rhinosinusitis (CRS). Growing evidence suggests extraoral taste receptors as relevant biomarkers, but current understanding is incomplete. This systematic review synthesizes current evidence of extraoral taste receptors in CRS.

METHODS

PubMed, Embase, Cochrane, Web of Science, and Scopus were reviewed in accordance with Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guidelines and included studies of genotypic and phenotypic T2R/T1R receptor status in CRS patients.

RESULTS

Twenty-two studies with 3,845 patients were included. Seventeen studies evaluated genotype and 10 evaluated taste phenotypes. Four of six studies examining the haplotype distribution of the T2R, TAS2R38, demonstrated increased AVI/AVI haplotype ("non-taster") frequency in CRS. Meanwhile, two studies demonstrated decreased bitter sensitivity in CRS with nasal polyposis (CRSwNP) while three other studies reported decreased bitter sensitivity only in CRS without nasal polyposis (CRSsNP). Findings regarding sweet sensitivity were mixed. Three studies with cystic fibrosis patients (n=1,393) were included. Studies investigating the association between clinical outcomes and TAS2R38 alleles were limited, but the nonfunctional combination of AVI/AVI was associated with increased utilization of sinus surgery and, in CRSsNP patients, with poorer improvement of symptoms postoperatively.

CONCLUSIONS

Both genotypic and phenotypic assessments of T2Rs suggest a potential association with CRS, particularly CRSsNP. However, limited evidence and mixed conclusions cloud the role of T2Rs in CRS. Future investigations should aim to increase diverse populations, broaden institutional diversity, examine T1Rs, and utilize uniform assessments. This article is protected by copyright. All rights reserved.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.

Divergent bitter and sweet taste perception intensity in chronic rhinosinusitis patients

BACKGROUND

Bitter and sweet taste receptors are present in the human upper airway, where they have roles in innate immunity. Previous studies have shown that 1 of the 25 bitter receptors, TAS2R38, responds to specific bacterial signaling molecules and evokes 1 type of a defense response in the upper airway, whereas ligands of sweet receptors suppress other types of defense responses.

METHODS

We examined whether other bitter taste receptors might also be involved in innate immunity by using sensory responses to bitter compounds that are not ligands of TAS2R38 (quinine and denatonium benzoate) to assess the sensitivity of other bitter receptors in chronic rhinosinusitis (CRS) patients. CRS patients with (n = 426) and without (n = 226) nasal polyps and controls (n = 356) rated the intensity of quinine, denatonium benzoate, phenylthiocarbamide (PTC; a ligand for TAS2R38), sucrose, and salt.

RESULTS

CRS patients rated the bitter compounds denatonium benzoate and quinine as less intense and sucrose as more intense than did controls (false discovery rate [FDR] <0.05) and CRS patients and controls did not differ in their ratings of salt (FDR >0.05). PTC bitter taste intensity differed between patient and control groups but were less marked than those previously reported. Though differences were statistically significant, overall effect sizes were small.

CONCLUSION

CRS patients report bitter stimuli as less intense but sweet stimuli as more intense than do control subjects. We speculate that taste responses may reflect the competence of sinonasal innate immunity mediated by taste receptor function, and thus a taste test may have potential for clinical utility in CRS patients.

Clinical Role of Extraoral Bitter Taste Receptors

Humans can recognise five basic tastes: sweet, sour, salty, bitter and umami. Sour and salty substances are linked to ion channels, while sweet, bitter and umami flavours are transmitted through receptors linked to the G protein (G protein-coupled receptors; GPCRs). There are two main types of GPCRs that transmit information about sweet, umami and bitter tastes-the Tas1r and TAS2R families. There are about 25 functional TAS2R genes coding bitter taste receptor proteins. They are found not only in the mouth and throat, but also in the intestines, brain, bladder and lower and upper respiratory tract. The determination of their purpose in these locations has become an inspiration for much research. Their presence has also been confirmed in breast cancer cells, ovarian cancer cells and neuroblastoma, revealing a promising new oncological marker. Polymorphisms of TAS2R38 have been proven to have an influence on the course of chronic rhinosinusitis and upper airway defensive mechanisms. TAS2R receptors mediate the bronchodilatory effect in human airway smooth muscle, which may lead to the creation of another medicine group used in asthma or chronic obstructive pulmonary disease. The discovery that functionally compromised TAS2R receptors negatively impact glucose homeostasis has produced a new area of diabetes research. In this article, we would like to focus on what facts have been already established in the matter of extraoral TAS2R receptors in humans.

A Systematic Review and Meta-Analysis of Taste Dysfunction in Chronic Rhinosinusitis

OBJECTIVES

Patients with chronic rhinosinusitis (CRS) often describe alterations in sense of taste. These complaints have historically been attributed to olfactory dysfunction; however, there is evidence of direct, objective, gustatory disturbances in the setting of CRS that are not thoroughly characterized. This study sought to investigate and summarize gustatory dysfunction experienced by patients with CRS.

METHODS

PubMed, EMBASE, Cochrane Library, Web of Science, and Scopus databases were reviewed following PRISMA guidelines. English language, original studies investigating objective taste in adult patients with CRS were included. A meta-analysis with inverse variance, random-effects model was performed.

RESULTS

Of 2750 studies screened, 11 articles with 471 unique patients were included. Patients with CRS exhibit worse gustatory function compared to healthy controls (standardized mean difference 0.94 [95% CI, 0.44-1.45]). Hypogeusia was identified in 32/95 (33.7%) patients from three studies that used methods with a validated definition of hypogeusia. Older age, male gender, and smoking history were associated with taste dysfunction, while objective gustatory and olfactory dysfunction were not correlated. Subjective taste and quality of life measures were also not associated with objective taste. The impact of sinus surgery on objective taste is unclear.

CONCLUSION

Approximately 34% of patients with CRS experience hypogeusia. Neither olfactory function nor subjective taste were associated with objective gustatory function. Given the substantial prevalence of taste dysfunction patients with CRS, there is significant potential for growth in understanding of pathogenesis, impact on quality of life, and potential treatment strategies of taste impairment in the CRS patient population.

LEVEL OF EVIDENCE

1 Laryngoscope, 131:482-489, 2021.

Personalized Medicine in Chronic Rhinosinusitis: Phenotypes, Endotypes, and Biomarkers

Chronic rhinosinusitis (CRS) is a heterogeneous disease process with a complex underlying cause. Improved understanding of CRS pathophysiology has facilitated new approaches to management of the patient with CRS that rely on targeting patient-specific characteristics and individual inflammatory pathways. A more personalized approach to care will ultimately incorporate a combination of phenotypic and endotypic classification systems to guide treatment. This review summarizes current evidence with respect to CRS phenotypes and endotypes, as well as the identification of potential biomarkers with potential to guide current and future treatment algorithms.