Rare haplotypes of the gene TAS2R38 confer bitter taste sensitivity in humans

Impact of TAS2R38 polymorphisms on nasal nitric oxide and Pseudomonas infections in primary ciliary dyskinesia: relation to genotype

OBJECTIVE

Primary ciliary dyskinesia (PCD) severity has been related to genotype and levels of nasal nitric oxide (nNO). The most common TAS2R38 haplotypes (PAV/PAV, PAV/AVI, AVI/AVI) encoding the bitter taste receptor can affect nNO levels and thus could play a role in the susceptibility to respiratory infections. We assessed the impact of these polymorphisms on nNO production and Pseudomonas aeruginosa (P.a.) infections in different PCD genotypes.

METHODS

Prospective, longitudinal, single-centre study in patients with PCD with known genotype and one of three TAS2R38 haplotypes evaluated for up to 10 years. We related nNO values to TAS2R38 haplotypes in all patients, and in the three most frequent genotypes (CCDC39/CCDC40, DNAH5, DNAH11). In the genetic group(s) with different mean trends of nNO in relation to the polymorphism, we evaluated longitudinal lung function as a clinical outcome measure. We also studied any associations between the prevalence of chronic P.a. infection and PAV alleles. Linear mixed-effects models were used to evaluate longitudinal associations.

RESULTS

119 patients with PCD underwent 1116 study visits. Only in the DNAH11 mutations group was there a mean trend of nNO production which was significantly higher in PAV/PAV than AVI/AVI haplotype (p=0.033), with a better trend in spirometric and plethysmographic parameters. In patients with DNAH11 mutations the PAV allele was also associated with a significantly reduced prevalence of chronic P.a.

INFECTION

CONCLUSION

TAS2R38 may be a modifier gene for PCD severity, but only in mild phenotype disease. Further study of TAS2R38 polymorphisms might enable new management strategies to prevent chronic P.a.

INFECTIONS

Association of the bitter taste genes TAS2R38 and CA6 and breast cancer risk; a case-control study of Polish women in Poland and Polish immigrants in USA

It is known that the perception of bitterness is mediated by type 2 bitter taste receptors (TAS2Rs). However, recent reports have suggested that the carbonic anhydrase 6 (CA6) gene may also influence bitterness sensing. Genetic variants in these genes could influence dietary intake of brassica vegetables, whose increased consumption has been observed in the literature, though inconsistently, to decrease breast cancer (BC) risk. We hypothesized that the estimated odds ratios (ORs) for the association between BC and taster diplotype (PAV/PAV) and/or genotype A/A, will be in the direction of increased BC risk, potentially due to reduced consumption of brassica vegetables. Using a case-control study of BC in Polish women in Poland (210 cases and 262 controls) and Polish immigrant women to USA (78 cases and 170 controls) we evaluated the association of the taster diplotypes in TAS2R38 gene and genotypes in the CA6 gene and BC risk in these two populations individually and jointly. No significant increase in risk was observed for the TAS2R38 PAV/PAV diplotype (tasters) in each population individually or in the joint population. For the CA6 gene, in the joint population, we observed an increased BC risk for the combined G/A and G/G genotypes (non-tasters) vs A/A (tasters), OR = 1.41 (95% CI 1.04-1.90, p = 0.026) which after adjustment for False Discovery Rate (FDR), was not significant at p≤0.05 level. However, for the joint population and for the combined genotype of the two genes AVI/AVI+G* (non-tasters) vs. PAV/*+A/A (tasters), we observed a significant increase in BC risk, OR = 1.77 (95%CI 1.47-2.74, p = 0.01), for the non-tasters, which remained significant after FDR adjustment. In conclusion for the joint population and the joint effect for the two bitter sensing genes, we observed an increase in BC risk for the bitterness non-tasters, association which is in the opposite direction to our original hypothesis.

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.

Characterization of the internal working-life exposome using minimally and non-invasive sampling methods - a narrative review

During recent years, we are moving away from the 'one exposure, one disease'-approach in occupational settings and towards a more comprehensive approach, taking into account the totality of exposures during a life course by using an exposome approach. Taking an exposome approach however is accompanied by many challenges, one of which, for example, relates to the collection of biological samples. Methods used for sample collection in occupational exposome studies should ideally be minimally invasive, while at the same time sensitive, and enable meaningful repeated sampling in a large population and over a longer time period. This might be hampered in specific situations e.g., people working in remote areas, during pandemics or with flexible work hours. In these situations, using self-sampling techniques might offer a solution. Therefore, our aim was to identify existing self-sampling techniques and to evaluate the applicability of these techniques in an occupational exposome context by conducting a literature review. We here present an overview of current self-sampling methodologies used to characterize the internal exposome. In addition, the use of different biological matrices was evaluated and subdivided based on their level of invasiveness and applicability in an occupational exposome context. In conclusion, this review and the overview of self-sampling techniques presented herein can serve as a guide in the design of future (occupational) exposome studies while circumventing sample collection challenges associated with exposome studies.

Association between Genetic Variation in the TAS2R38 Bitter Taste Receptor and Propylthiouracil Bitter Taste Thresholds among Adults Living in Japan Using the Modified 2AFC Procedure with the Quest Method

Individual taste sensitivity influences food preferences, nutritional control, and health, and differs greatly between individuals. The purpose of this study was to establish a method of measuring and quantifying an individual's taste sensitivity and to evaluate the relationship between taste variation and genetic polymorphisms in humans using agonist specificities of the bitter taste receptor gene, TAS2R38, with the bitter compound 6-n-propylthiouracil (PROP). We precisely detected the threshold of PROP bitter perception by conducting the modified two-alternative forced-choice (2AFC) procedure with the Bayesian staircase procedure of the QUEST method and examined genetic variation in TAS2R38 in a Japanese population. There were significant differences in PROP threshold between the three TAS2R38 genotype pairs for 79 subjects: PAV/PAV vs AVI/AVI, p < 0.001; PAV/AVI vs AVI/AVI, p < 0.001; and PAV/PAV vs PAV/AVI, p < 0.01. Our results quantified individual bitter perception as QUEST threshold values: the PROP bitter perception of individuals with the PAV/PAV or PAV/AVI genotypes was tens to fifty times more sensitive than that of an individual with the AVI/AVI genotype. Our analyses provide a basic model for the accurate estimation of taste thresholds using the modified 2AFC with the QUEST approach.

Influence of the TAS2R38 Gene Single Nucleotide Polymorphisms in Metabolism and Anthropometry in Thyroid Dysfunction

The gene TAS2R38 single nucleotide polymorphisms (SNPs-P49A, A262V and V296I) can condition bitter tasting by PAV (proline-alanine-valine) and non-bitter-tasting by AVI (alanine-valine-isoleucine) homozygosity. We evaluated this polymorphisms association with thyroid function, metabolism and anthropometry parameters determined by: Endpoint analysis (SNPs); DXA (fat mass-%, total fat mass-kg, lean mass-kg); Standard methods (lipid metabolism parameters, HbA1c-%, glycemia-mg/dL, insulinemia-µIU/mL, HOMA-IR, uricemia-mg/dL, calcemia-mg/dL and BMI-kg/m²); ELISA (leptinemia-ng/mL); Spectrophotometry (Angiotensin Converting Enzyme activity-UI/L). Statistics: SPSS program; OR [IC95%]; p < 0.05. Sample: 114 hypothyroid, 49 hyperthyroid, and 179 controls. An association between A262V-valine-valine and hypothyroidism/hyperthyroidism was verified (OR = 2.841; IC95% [1.726-4.676]), p < 0.001/OR = 8.915; IC95% [4.286-18.543]), p < 0.001). Protector effect from thyroid dysfunction: A262V-alanine-valine (OR = 0.467; IC95% [0.289-0.757], p = 0.002/OR = 0.132; IC95% [0.056-0.309], p < 0.001) and PAV (OR = 0.456; IC95% [0.282-0.737], p = 0.001/OR = 0.101; IC95% [0.041-0.250], p < 0.001). Higher parameter values associated with genotypes were: fat-mass-% (V296I-valine-isoleucine), lean-mass (P49A-proline-proline; PVI), leptin (AVI), HbA1c (A262V-alanine-valine) and lower values in lean-Mass (AVI; PVV), leptin (A262V-alanine-alanine), HbA1c (PVV), uricemia (V296I-valine-isoleucine), glycemia (A262V-alanine-alanine; AAV) and plasma triglycerides (PVV). In conclusion, TAS2R38 influences thyroid function, body composition and metabolism. Bitter taste perception (PAV) and the genotype A262V-alanine-valine can protect from thyroid dysfunction. AVV, PVV and genotype A262V-valine-valine may confer higher predisposition for thyroid dysfunction, particularly PVV for hyperthyroidism.

Automated identification of the genetic variants of TAS2R38 bitter taste receptor with supervised learning

Several studies were focused on the genetic ability to taste the bitter compound 6-n-propylthiouracil (PROP) to assess the inter-individual taste variability in humans, and its effect on food predilections, nutrition, and health. PROP taste sensitivity and that of other chemical molecules throughout the body are mediated by the bitter receptor TAS2R38, and their variability is significantly associated with TAS2R38 genetic variants. We recently automatically identified PROP phenotypes with high precision using Machine Learning (mL). Here we have used Supervised Learning (SL) algorithms to automatically identify TAS2R38 genotypes by using the biological features of eighty-four participants. The catBoost algorithm was the best-suited model for the automatic discrimination of the genotypes. It allowed us to automatically predict the identification of genotypes and precisely define the effectiveness and impact of each feature. The ratings of perceived intensity for PROP solutions (0.32 and 0.032 mM) and medium taster (MT) category were the most important features in training the model and understanding the difference between genotypes. Our findings suggest that SL may represent a trustworthy and objective tool for identifying TAS2R38 variants which, reducing the costs and times of molecular analysis, can find wide application in taste physiology and medicine studies.

Variations in the TAS2R38 gene among college students in Hubei

BACKGROUND

The bitter taste receptor gene TAS2R38 is a member of the human TAS2R gene family. Polymorphisms in TAS2R38 affect the ability to taste the bitterness of phenylthiourea (PTC) compounds, thus affecting an individual's food preference and health status.

METHODS

We investigated polymorphisms in the TAS2R38 gene and the sensitivity to PTC bitterness among healthy Chinese college students in Hubei province. The association of TAS2R38 polymorphisms and PTC sensitivity with body mass index (BMI), food preference, and health status was also analyzed. A total of 320 healthy college students were enrolled (male: 133, female: 187; aged 18-23 years). The threshold value method was used to measure the perception of PTC bitterness, and a questionnaire was used to analyze dietary preferences and health status. Polymerase chain reaction (PCR) was used to analyze polymorphisms at three common TAS2R38 loci (rs713598, rs1726866, and rs10246939).

RESULTS

In our study population, 65.00% of individuals had medium sensitivity to the bitterness of PTC; in contrast, 20.94% were highly sensitive to PTC bitterness, and 14.06% were not sensitive. For the TAS2R38 gene, the PAV/PAV and PAV/AAI diplotypes were the most common (42.19% and 40.63%, respectively), followed by the homozygous AVI/AVI (8.75%) and PAV/AVI (5.00%) diplotypes.

CONCLUSION

There was a significant correlation between the sensitivity to PTC bitterness and sex, but there was no correlation between the common diplotypes of TAS2R38 and gender. Polymorphisms in the TAS2R38 gene were associated with the preference for tea, but not with one's native place, BMI, health status, or other dietary preferences. There was no significant correlation between the perception of PTC bitterness and one's native place, BMI, dietary preference, or health status. We hope to find out the relationship between PTC sensitivity and TAS2R38 gene polymorphisms and dietary preference and health status of Chinese population through this study, providing relevant guidance and suggestions for dietary guidance and prevention of some chronic diseases in Chinese population.

Associations between Sweet Taste Sensitivity and Polymorphisms (SNPs) in the TAS1R2 and TAS1R3 Genes, Gender, PROP Taster Status, and Density of Fungiform Papillae in a Genetically Homogeneous Sardinian Cohort

Individual differences in sweet taste sensitivity can affect dietary preferences as well as nutritional status. Despite the lack of consensus, it is believed that sweet taste is impacted by genetic and environmental variables. Here we determined the effect of well-established factors influencing the general taste variability, such as gender and fungiform papillae density, specific genetic variants (SNPs of TAS1R2 and TAS1R3 receptors genes), and non-specific genetic factors (PROP phenotype and genotype), on the threshold and suprathreshold sweet taste sensitivity. Suprathreshold measurements showed that the sweet taste response increased in a dose-dependent manner, and this was related to PROP phenotype, gender, rs35874116 SNP in the TAS1R2 gene, and rs307355 SNP in the TAS1R3 gene. The threshold values and density of fungiform papillae exhibited a strong correlation, and both varied according to PROP phenotype. Our data confirm the role of PROP taste status in the sweet perception related to fungiform papilla density, show a higher sweet sensitivity in females who had lower BMI than males, and demonstrate for the first time the involvement of the rs35874116 SNP of TAS1R2 in the sweet taste sensitivity of normal weight subjects with body mass index (BMI) ranging from 20.2 to 24.8 kg/m2. These results may have an important impact on nutrition and health mostly in subjects with low taste ability for sweets and thus with high vulnerability to developing obesity or metabolic disease.

Impact of the Gut-Brain Hormonal Axis and Enteric Peptides in the Development of Food Neophobia in Children with Genetically Determined Hypersensitivity to the Bitter Taste

Objective: The aim of this prospective study was to determine the role of the gut-brain hormonal axis and the effect of the enteric peptides, as well as the role of genetically determined sensitivity to the bitter taste, on the development of child food neophobia (CFN). Methods: 114 children were enrolled in the study: 43 in food neophobia group (FNG), 21 In the control group (CG) and 50 in prospective group (PG). All patients were assessed with the child food neophobia scale (CFNS), underwent an oral 6-propylthiouracil (6-PROP) test, buccal swab for bitter-taste genotyping, anthropometric measurements, and were tested for serum levels of leptin, adiponectin, insulin-like growth factor-1(IGF-1), ghrelin, and neuropeptide Y (NPY), and complete blood count (CBC); measurements were taken from a blood sample after 4 h fasting. Results: Subjects from FNG were more often hypersensitive to bitter taste (6-PROP) than CG (p = 0.001). There was no correlation between the result of genetic analysis and CFNS (p = 0.197), nor the body mass index (BMI) at the age of 18–36 months (p = 0.946) found. Correlation between 6-PRO perception and genotype have not been confirmed (p = 0.064). The score of CFNS was positively related to the serum level of NPY (p = 0.03). BMI percentile was negatively related to serum level of NPY (p = 0.03), but positively related to leptin serum level (p = 0.027). Conclusions: Bitter taste sensitivity to 6-PROP plays an important role in the development of the CFN, but correlation between 6-PROP perception and genotype have not been confirmed. Children with food neophobia due to elevated serum NPY level should be constantly monitored in order to control the nutritional status at a later age.

Variation in TAS2R receptor genes explains differential bitterness of two common antibiotics

For pharmaceuticals to deliver their full benefits with maximum efficacy, patients need to follow recommended dosing schedules, in terms of amount and frequency. Unfortunately, the aversive taste of many drugs, especially bitterness, can reduce patient compliance in oral liquid formulations. Given common genetic differences in bitter taste receptor genes (TAS2Rs), some individuals may be at increased risk for poor compliance due to heightened bitterness that becomes a barrier to proper use. Here we report on the sensory profile of two antibiotics, chloramphenicol and ofloxacin, investigating whether bitterness intensity associates with nominally functional TAS2R variants. Participants (n = 143) rated suprathreshold intensity on a general Labeled Magnitude Scale (gLMS) for chloramphenicol and ofloxacin; propylthiouracil (PROP) was included as a control, given robust prior associations with TAS2R38 variants. The dominant sensation from chloramphenicol and ofloxacin was bitterness, falling just below “moderate” on a gLMS. TAS2R38 diplotype associated with variable bitterness of chloramphenicol and PROP, but not ofloxacin. The bitterness of ofloxacin associated with a TAS2R9 SNP (V187A). This pilot study provides novel evidence on differences in the bitterness from two antibiotics, which are associated with TAS2R variants. Improved understanding of individualized barriers to patient compliance, especially for oral formulations, can guide future efforts to optimize delivery systems for improved compliance.

Automated Classification of 6-n-Propylthiouracil Taster Status with Machine Learning

Several studies have used taste sensitivity to 6-n-propylthiouracil (PROP) to evaluate interindividual taste variability and its impact on food preferences, nutrition, and health. We used a supervised learning (SL) approach for the automatic identification of the PROP taster categories (super taster (ST); medium taster (MT); and non-taster (NT)) of 84 subjects (aged 18-40 years). Biological features determined from subjects were included for the training system. Results showed that SL enables the automatic identification of objective PROP taster status, with high precision (97%). The biological features were classified in order of importance in facilitating learning and as prediction factors. The ratings of perceived taste intensity for PROP paper disks (50 mM) and PROP solution (3.2 mM), along with fungiform papilla density, were the most important features, and high estimated values pushed toward ST prediction, while low values leaned toward NT prediction. Furthermore, TAS2R38 genotypes were significant features (AVI/AVI, PAV/PAV, and PAV/AVI to classify NTs, STs, and MTs, respectively). These results, in showing that the SL approach enables an automatic, immediate, scalable, and high-precision classification of PROP taster status, suggest that it may represent an objective and reliable tool in taste physiology studies, with applications ranging from basic science and medicine to food sciences.

Predominant Qualities Evoked by Quinine, Sucrose, and Capsaicin Associate With PROP Bitterness, but not TAS2R38 Genotype

Genetic variability in the ability to taste thiourea compounds has been studied for 80+ years. Over the last 3 decades, many studies have reported perceived intensity of concentrated propylthiouracil (PROP) associates with greater intensity from a broad range of stimuli, including nonbitter tastants, irritants, and retronasally delivered odorants. Thus, PROP phenotype has become a common measure of individual differences in orosensation. Much, but not all, of the phenotypic variation in PROP bitterness is explained by TAS2R38 polymorphisms. While differences in PROP bitterness are clearly due to genetic variation, mechanistically it is challenging to envision how this receptor (narrowly tuned to the N-C=S moiety) relates to overall orosensory response. Here, we report data for 200+ individuals who had been genotyped for TAS2R38 and phenotyped for PROP in a laboratory setting. Participants also reported the intensity of quinine, capsaicin, and sucrose on a general Labeled Magnitude Scale. Our data recapitulate earlier reports associating PROP bitterness with the intensity of the predominant qualities of sucrose, quinine, and capsaicin; however, we also find correlations between the intensities of sucrose, quinine, and capsaicin were much stronger with each other than with PROP. As expected, TAS2R38 diplotype did not associate with the intensity of sucrose, quinine, or capsaicin. The strength of PROP-capsaicin and PROP-sucrose relationships increased after grouping participants by TAS2R38 diplotype, with the greatest increases in association observed within homozygotes. Collectively, this suggests the suprathreshold intensity of PROP is a confounded phenotype that captures both genetic variation specific to N-C=S compounds and overall orosensation.

Allyl Isothiocyanate: A TAS2R38 Receptor-Dependent Immune Modulator at the Interface Between Personalized Medicine and Nutrition

Understanding individual responses to nutrition and medicine is of growing interest and importance. There is evidence that differences in bitter taste receptor (TAS2R) genes which give rise to two frequent haplotypes, TAS2R38-PAV (functional) and TAS2R38-AVI (non-functional), may impact inter-individual differences in health status. We here analyzed the relevance of the TAS2R38 receptor in the regulation of the human immune response using the TAS2R38 agonist allyl isothiocyanate (AITC) from Brassica plants. A differential response in calcium mobilization upon AITC treatment in leucocytes from healthy humans confirmed a relevance of TAS2R38 functionality, independent from cation channel TRPV1 or TRPA1 activation. We further identified a TAS2R38-dependence of MAPK and AKT signaling activity, bactericidal (toxicity against E. coli) and anti-inflammatory activity (TNF-alpha inhibition upon cell stimulation). These in vitro results were derived at relevant human plasma levels in the low micro molar range as shown here in a human intervention trial with AITC-containing food.

Changes of Taste, Smell and Eating Behavior in Patients Undergoing Bariatric Surgery: Associations with PROP Phenotypes and Polymorphisms in the Odorant-Binding Protein OBPIIa and CD36 Receptor Genes

Bariatric surgery is the most effective long-term treatment for severe obesity and related comorbidities. Although patients who underwent bariatric surgery report changes of taste and smell perception, results from sensory studies are discrepant and limited. Here, we assessed taste and smell functions in 51 patients before, one month, and six months after undergoing bariatric surgery. We used taste strip tests to assess gustatory function (including sweetness, saltiness, sourness, umaminess, bitterness and oleic acid, a fatty stimulus), the “Sniffin’ Sticks” test to assess olfactory identification and the 3-Factor Eating Questionnaire to assess eating behavior. We also explored associations between these phenotypes and flavor-related genes. Results showed an overall improvement in taste function (including increased sensitivity to oleic acid and the bitterness of 6-n-propylthiouracil (PROP)) and in olfactory function (which could be related to the increase in PROP and oleic acid sensitivity), an increase in cognitive restraint, and a decrease in disinhibition and hunger after bariatric surgery. These findings indicate that bariatric surgery can have a positive impact on olfactory and gustatory functions and eating behavior (with an important role of genetic factors, such PROP tasting), which in turn might contribute to the success of the intervention.

Credit for and Control of Research Outputs in Genomic Citizen Science

Citizen science encompasses activities with scientific objectives in which members of the public participate as more than passive research subjects from whom personal data or biospecimens are collected and analyzed by others. Citizen science is increasingly common in the biomedical sciences, including the fields of genetics and human genomics. Genomic citizen science initiatives are diverse and involve citizen scientists in collecting genetic data, solving genetic puzzles, and conducting experiments in community laboratories. At the same time that genomic citizen science is presenting new opportunities for individuals to participate in scientific discovery, it is also challenging norms regarding the manner in which scientific research outputs are managed. In this review, we present a typology of genomic citizen science initiatives, describe ethical and legal foundations for recognizing genomic citizen scientists' claims of credit for and control of research outputs, and detail how such claims are or might be addressed in practice across a variety of initiatives.

Cystic fibrosis transmembrane conductance regulator function, not TAS2R38 gene haplotypes, predict sinus surgery in children and young adults with cystic fibrosis

BACKGROUND

Chronic rhinosinusitis symptomatology begins in early childhood individuals with cystic fibrosis (CF). Cystic fibrosis transmembrane conductance regulator (CFTR) function contributes to sinus development and disease. Genetic variants of the bitter taste receptor TAS2R38 have been suggested to contribute to sinus disease severity in individuals without CF. Our objective was to explore whether functional TAS2R38 haplotypes and CFTR function are associated with sinus disease or the need for sinus surgery in individuals with CF.

METHODS

We conducted a retrospective study using prospectively collected data from the CF Twin-Sibling Study. The function of CFTR was assessed via chloride conductance. Genotyping of the TAS2R38 gene identified patients who were homozygous for the functional haplotype, heterozygous, or homozygous for nonfunctional haplotypes. Clustered multivariate logistic regression was performed, controlling for sex and family relationship.

RESULTS

A total of 1291 patients were evaluated. Patients with ≤1% CFTR function were 1.56 times more likely to require sinus surgery than those with >1% CFTR function (p = 0.049). CFTR function did not correlate significantly with the presence of sinus disease (p = 0.30). In addition, there were no statistically significant differences in diagnosis of sinus disease or need for sinus surgery between patients with functional and nonfunctional TAS2R38 haplotypes.

CONCLUSION

CFTR function correlates with need for sinus surgery, whereas TAS2R38 function does not appear to contribute to sinus disease or the need for sinus surgery in patients with CF.

Genes and Eating Preferences, Their Roles in Personalized Nutrition

At present, personalized diets, which take into account consumer genetic characteristics, are growing popular. Nutrigenetics studies the effect of gene variations on metabolism and nutrigenomics, which branches off further and investigates how nutrients and food compounds affect genes. This work deals with the mutations affecting the assimilation of metabolites, contributing to nutrigenetic studies. We searched for the genes responsible for eating preferences which allow for the tailoring of personalized diets. Presently, genetic nutrition is growing in demand, as it contributes to the prevention and/or rehabilitation of non-communicable diseases, both monogenic and polygenic. In this work, we showed single-nucleotide polymorphisms in genes-missense mutations that change the functions of coded proteins, resulting in a particular eating preferences or a disease. We studied the genes influencing food preferences-particularly those responsible for fats and carbohydrates absorption, food intolerance, metabolism of vitamins, taste sensations, oxidation of xenobiotics, eating preferences and food addiction. As a result, 34 genes were identified that affect eating preferences. Significant shortcomings were found in the methods/programs for developing personalized diets that are used today, and the weaknesses were revealed in the development of nutrigenetics (inconsistency of data on SNP genes, ignoring population genetics data, difficult information to understand consumer, etc.). Taking into account all the shortcomings, an approximate model was proposed in the review for selecting an appropriate personalized diet. In the future, it is planned to develop the proposed model for the compilation of individual diets.

TAS2R38 PAV Haplotype Predicts Vegetable Consumption in Community-Dwelling Caucasian Adults at Risk for Cardiovascular Disease

INTRODUCTION

A heart-healthy diet might reduce cardiovascular disease (CVD) risk. Genetic variants that affect taste are associated with food choices. This study aims to investigate the associations of the TAS2R38 haplotype with consumption of sodium, sugar, saturated fats, and vegetables.

HYPOTHESIS

We hypothesized that, compared to people who are alanine-valine-isoleucine (AVI) homozygous for the TAS2R38 gene, those who are heterozygous or homozygous for the proline-alanine-valine (PAV) haplotype would have (a) a higher intake of sodium, sugar, and saturated fat, and (b) a lower vegetable intake.

METHODS

DNA from participants at risk for CVD was genotyped, and participants were assigned to groups by haplotype. Intake for sodium, sugar, saturated fat, and vegetables was assessed using the Viocare Food Frequency Questionnaire. Intake was categorized as higher versus lower consumption, divided at the median, and examined by logistic regressions. All models controlled for age, sex, smoking status, body mass index, education level, and financial status.

RESULTS

The 175 participants had a mean age of 52 ± 13 years, 72.6% were female, 100% were Caucasian, 89.1% were overweight or obese, and 82.9% were nonsmokers. Participants with one or two PAVs were grouped together, as PAV is the dominant gene, and comprised a majority of the sample (80.6%). Haplotype did not predict intake of sodium, sugar, or saturated fats. Compared to AVI homozygotes, participants with PAV homozygous or heterozygous haplotype had lower odds of being in the higher vegetable intake group (95% CI [0.17, 0.92], p = .032).

CONCLUSIONS

PAV haplotype predicted lower consumption of vegetables. Variants of taste-related genes appear to play a role in food choices.

Donors, authors, and owners: how is genomic citizen science addressing interests in research outputs?

BACKGROUND

Citizen science is increasingly prevalent in the biomedical sciences, including the field of human genomics. Genomic citizen science initiatives present new opportunities to engage individuals in scientific discovery, but they also are provoking new questions regarding who owns the outputs of the research, including intangible ideas and discoveries and tangible writings, tools, technologies, and products. The legal and ethical claims of participants to research outputs become stronger-and also more likely to conflict with those of institution-based researchers and other stakeholders-as participants become more involved, quantitatively and qualitatively, in the research process. It is not yet known, however, how genomic citizen science initiatives are managing the interests of their participants in accessing and controlling research outputs in practice. To help fill this gap, we conducted an in-depth review of relevant policies and practices of U.S.-based genomic citizen science initiatives.

METHODS

We queried the peer-reviewed literature and grey literature to identify 22 genomic citizen science initiatives that satisfied six inclusion criteria. A data collection form was used to capture initiative features, policies, and practices relevant to participants' access to and control over research outputs.

RESULTS

This analysis revealed that the genomic citizen science landscape is diverse and includes many initiatives that do not have institutional affiliations. Two trends that are in apparent tension were identified: commercialization and operationalization of a philosophy of openness. While most initiatives supported participants' access to research outputs, including datasets and published findings, none supported participants' control over results via intellectual property, licensing, or commercialization rights. However, several initiatives disclaimed their own rights to profit from outputs.

CONCLUSIONS

There are opportunities for citizen science initiatives to incorporate more features that support participants' access to and control over research outputs, consistent with their specific objectives, operations, and technical capabilities.

Citizen science frontiers: Efficiency, engagement, and serendipitous discovery with human-machine systems

Citizen science has proved to be a unique and effective tool in helping science and society cope with the ever-growing data rates and volumes that characterize the modern research landscape. It also serves a critical role in engaging the public with research in a direct, authentic fashion and by doing so promotes a better understanding of the processes of science. To take full advantage of the onslaught of data being experienced across the disciplines, it is essential that citizen science platforms leverage the complementary strengths of humans and machines. This Perspectives piece explores the issues encountered in designing human-machine systems optimized for both efficiency and volunteer engagement, while striving to safeguard and encourage opportunities for serendipitous discovery. We discuss case studies from Zooniverse, a large online citizen science platform, and show that combining human and machine classifications can efficiently produce results superior to those of either one alone and how smart task allocation can lead to further efficiencies in the system. While these examples make clear the promise of human-machine integration within an online citizen science system, we then explore in detail how system design choices can inadvertently lower volunteer engagement, create exclusionary practices, and reduce opportunity for serendipitous discovery. Throughout we investigate the tensions that arise when designing a human-machine system serving the dual goals of carrying out research in the most efficient manner possible while empowering a broad community to authentically engage in this research.

Taste disorders are partly genetically determined: Role of the TAS2R38 gene, a pilot study

OBJECTIVES/HYPOTHESIS

Taste sensitivity varies greatly among individuals influencing eating behavior and health, consequently the disorders of this sense can affect the quality of life. The ability to perceive the bitter of thiourea compounds, such as phenylthiocarbamide (PTC), has been largely reported as a marker of the general taste sensitivity, food preferences, and health. PTC sensitivity is mediated by the TAS2R38 receptor and its genetic common variants. We study the role of the TAS2R38 receptor in taste disorders with the aim of understanding if these can be genetically determined.

STUDY DESIGN

Prospective cohort study.

METHODS

Differences in the PTC responsiveness between the patients cohort and healthy controls were assessed. All subjects received standardized tests for smell and taste function and were genotyped for the TAS2R38 gene.

RESULTS

PAV/PAV homozygous patients gave high PTC ratings, whereas PAV/AVI genotypes reported lower values, which are similar to those determined in AVI/AVI or rare genotypes. In addition, the patients cohort did not meet the Hardy-Weinberg equilibrium at the TAS2R38 locus, showing a very low frequency of subjects carrying the PAV/AVI diplotype. Independently, in healthy controls who were in equilibrium at the locus, PAV/PAV homozygous and heterozygous rated PTC bitterness higher compared to AVI/AVI or rare genotypes.

CONCLUSIONS

Our findings, by showing that an only taster haplotype (PAV) is not sufficient to evoke high responses of TAS2R38 receptor in patients with taste disorders, suggest that the genetic constitution may represent a risk factor for the development of taste disorders.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:E307-E312, 2019.

Human T2R38 Bitter Taste Receptor Expression in Resting and Activated Lymphocytes

The human G-protein-coupled bitter taste receptor T2R38 has recently been demonstrated to be expressed on peripheral blood neutrophils, monocytes and lymphocytes. To further define a potential contribution of the T2R38 receptor in adaptive immune response, the objective of this study was to analyze its expression in resting and activated lymphocytes and T cell subpopulations. Freshly isolated PBMC from healthy donors were used for expression analysis by flow cytometry. Quantum™ MESF beads were applied for quantification in absolute fluorescence units. Activation methods of T cells were anti-CD3/CD28, phytohaemagglutinin (PHA) or phorbol 12-myristate 13-acetate (PMA) together with ionomycin. Lymphocytes from young donors expressed higher levels of T2R38 compared to the elderly. CD3+ T cells expressed higher levels that CD19+ B cells. Receptor expression followed T cell activation with an upregulation within 24 h and a peak at 72 h. Higher levels of T2R38 were produced in lymphocytes by stimulation with anti-CD3/CD28 compared to PHA or PMA/ionomycin. Both subpopulations of CD4+ as well as CD8+ T cells were found to express the T2R38 receptor; this was higher in CD4+ than CD8+ cells; the amount of T2R38 in central and effector memory cells was higher as compared to naïve cells, although this was not statistically significant for CD8+ cells without prior activation by anti-CD3/CD28. Upon treatment of PBMC with the natural T2R38 agonist goitrin Calcium flux was activated in the lymphocyte population with functional T2R38 receptor at >20 μM which was completely blocked by phospholipase Cβ-2 inhibitor U73211. Further, goitrin selectively inhibited TNF-alpha secretion in PBMC with functional T2R38. This quantitative analysis of T2R38 expression in distinct PBMC subsets may provide a basis for understanding the significance of bitter compounds in immune modulation. Whether these findings can have implications for the treatment of inflammatory and immunologic disorders by bitter tasting pharmaceuticals or foods needs further investigation.

Self-reported Smoking Status, TAS2R38 Variants, and Propylthiouracil Phenotype: An Exploratory Crowdsourced Cohort Study

TAS2R38 gene variants, which confer sensitivity to specific bitter tastants (e.g., 6-n-propylthiouracil), have been repeatedly associated with lower alcohol use via greater bitterness perception, but research exploring TAS2R38 variation in relation to smoking shows mixed results. In both, the working hypothesis is that 1 or more copies of the functional allele increases bitterness and may provide a barrier to early use. Such a barrier to initiation may, conceivably, manifest as differential rates of current use across diplotypes. Here, an age-diverse convenience sample (n = 886) of Denver Museum of Nature and Science guests was used to explore cross-sectional relationships between TAS2R38 diplotype, self-reported tobacco use (current, former, never smokers), and a rapid measure of 6-n-propylthiouracil phenotype (bitterness of filter paper discs). TAS2R38 diplotypes were determined by Sanger sequencing. After excluding rare diplotypes, data from 814 participants were analyzed. A mix of current (~10%), former (25%), and never smokers (65%) were included. As expected, there was a relationship between TAS2R38 diplotype and 6-n-propylthiouracil bitterness. However, contrary to our hypothesis, there was no evidence of a relationship between diplotype and smoker status among participants with common TAS2R38 diplotypes. Notably, we observed a relationship between of 6-n-propylthiouracil bitterness and smoking status, but the effect was opposite of what was expected: current smokers perceived higher (not lower) bitterness than never smokers. When all the various factors (diplotype, age, sex, and smoking status) were included in ANOVA, all remained predictive of 6-n-propylthiouracil bitterness. Reasons for greater phenotypic bitterness among current smokers are unknown and merit further study.

TAS2R38 Predisposition to Bitter Taste Associated with Differential Changes in Vegetable Intake in Response to a Community-Based Dietary Intervention

Although vegetable consumption associates with decreased risk for a variety of diseases, few Americans meet dietary recommendations for vegetable intake. TAS2R38 encodes a taste receptor that confers bitter taste sensing from chemicals found in some vegetables. Common polymorphisms in TAS2R38 lead to coding substitutions that alter receptor function and result in the loss of bitter taste perception. Our study examined whether bitter taste perception TAS2R38 diplotypes associated with vegetable consumption in participants enrolled in either an enhanced or a minimal nutrition counseling intervention. DNA was isolated from the peripheral blood cells of study participants (N = 497) and analyzed for polymorphisms. Vegetable consumption was determined using the Block Fruit and Vegetable screener. We tested for differences in the frequency of vegetable consumption between intervention and genotype groups over time using mixed effects models. Baseline vegetable consumption frequency did not associate with bitter taste diplotypes (P = 0.937), however after six months of the intervention, we observed an interaction between bitter taste diplotypes and time (P = 0.046). Participants in the enhanced intervention increased their vegetable consumption frequency (P = 0.020) and within this intervention group, the bitter non-tasters and intermediate-bitter tasters had the largest increase in vegetable consumption. In contrast, in the minimal intervention group, the bitter tasting participants reported a decrease in vegetable consumption. Bitter-non tasters and intermediate-bitter tasters increased vegetable consumption in either intervention more than those who perceive bitterness. Future precision medicine applications could consider genetic variation in bitter taste perception genes when designing dietary interventions.

6-n-propylthiouracil taste disruption and TAS2R38 nontasting form in Parkinson's disease

BACKGROUND

The few studies that evaluated taste function in Parkinson's disease (PD) showed inconsistent results. The inherited ability to taste the bitter compound of 6-n-propylthiouracil has been considered to be a paradigm of general taste perception. 6-n-propylthiouracil taste perception is mediated by the TAS2R38 receptor, and reduced 6-n-propylthiouracil sensitivity has been associated with several diseases not typically related to taste function.

OBJECTIVES

We evaluated the 6-n-propylthiouracil taste perception and the TAS2R38 gene as genetic risk factors for the development of idiopathic PD in PD patients and healthy controls (HC).

METHODS

The 6-n-propylthiouracil taste perception was assessed by testing the responsiveness, and the ability to recognize, 6-n-propylthiouracil and sodium chloride. The participants were classified for 6-n-propylthiouracil taster status and genotyped for the TAS2R38 gene.

RESULTS

A significant increase in the frequency of participants classified as 6-n-propylthiouracil nontasters and a reduced ability to recognize bitter taste quality of 6-n-propylthiouracil were found in PD patients when compared with healthy controls. The results also showed that only 5% of PD patients had the homozygous genotype for the dominant tasting variant of TAS2R38, whereas most of them carried the recessive nontaster form and a high number had a rare variant.

CONCLUSIONS

Our results show that 6-n-propylthiouracil taster status and TAS2R38 locus are associated with PD. The 6-n-propylthiouracil test may therefore represent a novel, simple way to identify increased vulnerability to PD. Moreover, the presence of the nontasting form of TAS2R38 in PD may further substantiate that disease-associated taste disruption may represent a risk factor associated with the disease. © 2018 International Parkinson and Movement Disorder Society.

Factors Influencing the Phenotypic Characterization of the Oral Marker, PROP

In the last several decades, the genetic ability to taste the bitter compound, 6-n-propyltiouracil (PROP) has attracted considerable attention as a model for understanding individual differences in taste perception, and as an oral marker for food preferences and eating behavior that ultimately impacts nutritional status and health. However, some studies do not support this role. This review describes common factors that can influence the characterization of this phenotype including: (1) changes in taste sensitivity with increasing age; (2) gender differences in taste perception; and (3) effects of smoking and obesity. We suggest that attention to these factors during PROP screening could strengthen the associations between this phenotype and a variety of health outcomes ranging from variation in body composition to oral health and cancer risk.

Genetic variation in bitter taste receptor gene TAS2R38, PROP taster status and their association with body mass index and food preferences in Indian population

Polymorphisms in bitter taste receptor gene TAS2R38 alter the ability to sense the intensity of bitterness of phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP). Genetic variation in sensitivity towards PTC and PROP may affect food preferences and susceptibility to certain diseases. This is the first study aimed at investigating frequency and distribution of TAS2R38 haplotypes in an Indian cohort. Additionally, we studied the association of TAS2R38 and PROP taster status with BMI and food preference. Three hundred and ninety three healthy adults who were 19-55years of age were selected as a convenience sample from 4 geographical regions of India. Single nucleotide polymorphisms (SNPs) of TAS2R38 (rs713598, s1726866 and rs10246939) were analyzed using polymerase chain reaction-restriction fragment length polymorphism. The prevalence of PAV/PAV diplotype was 9.9% and that of AVI/AVI diplotype was 43.76% among this Indian population. PROP status was determined on the basis of its threshold concentration of detecting bitterness, as evaluated by one-solution test. The PROP status revealed 25.95% supertasters, 32.06% medium tasters and 41.98% non-tasters (NT). BMI neither significantly (p>0.05) correlated with TAS2R38 genotypes nor with PROP taster status. Food preferences did not significantly (p>0.05) correlate with TAS2R38 diplotypes or PROP phenotypes.

Intranasal Insulin Boosts Gustatory Sensitivity

Intranasal insulin has been the subject of attention not only with respect to enhancing memory processes, but also for its anorexic effects, as well as its effects on olfactory sensitivity. In the present study, the influence of intranasal insulin on gustatory sensitivity was investigated using intranasal applications of insulin or placebo in a double-blind manner alongside a control condition without any application. We hypothesised that, because it mediates satiety, intranasal insulin alters gustatory sensitivity, whereas placebo application and the control should not alter gustatory sensitivity. We did not expect the sensitivity to the different taste solutions to differ. Sweet, salty, bitter and sour liquids in four concentrations each were sprayed onto the tongue of healthy male subjects. Additionally, water with no taste was applied to enable calculation of taste sensitivity in terms of parameter d' of signal detection theory. The task of the subject was to identify the quality of the respective tastant. Gustatory sensitivity and blood parameters were evaluated using repeated-measures ANOVAs. Gustatory sensitivity (implying all tastants) improved significantly after intranasal insulin application compared to the application of placebo, although it did not reach significance compared to the control condition. Subjects performed best when detecting the sweet taste and worst when detecting the bitter taste. The blood parameters glucose, insulin, homeostatic model assessment and leptin did not differ with respect to insulin or placebo condition, nor did they differ regarding measurements preceding or following intranasal application, in confirmation of preserved peripheral euglycaemia during the experiment. Thus, it can be concluded that the application of intranasal insulin led to an improved gustatory sensitivity compared to placebo.

Genetic and environmental influences on food preferences in adolescence

BACKGROUND

Food preferences vary substantially among adults and children. Twin studies have established that genes and aspects of the shared family environment both play important roles in shaping children's food preferences. The transition from childhood to adulthood is characterized by large gains in independence, but the relative influences of genes and the environment on food preferences in late adolescence are unknown.

OBJECTIVE

The aim of this study was to quantify the contribution of genetic and environmental influences on food preferences in older adolescents.

DESIGN

Participants were 2865 twins aged 18-19 y from the TEDS (Twins Early Development Study), a large population-based cohort of British twins born during 1994-1996. Food preferences were measured by using a self-report questionnaire of 62 individual foods. Food items were categorized into 6 food groups (fruit, vegetables, meat or fish, dairy, starch foods, and snacks) by using factor analysis. Maximum likelihood structural equation modeling established genetic and environmental contributions to variations in preferences for each food group.

RESULTS

Genetic factors influenced a significant and substantial proportion of the variation in preference scores of all 6 food groups: vegetables (0.54; 95% CI: 0.47, 0.59), fruit (0.49; 95% CI: 0.43, 0.55), starchy foods (0.32; 95% CI: 0.24, 0.39), meat or fish (0.44; 95% CI: 0.38, 0.51), dairy (0.44; 95% CI: 0.37, 0.50), and snacks (0.43; 95% CI: 0.36, 0.49). Aspects of the environment that are not shared by 2 twins in a family explained all of the remaining variance in food preferences.

CONCLUSIONS

Food preferences had a moderate genetic basis in late adolescence, in keeping with findings in children. However, by this older age, the influence of the shared family environment had disappeared, and only aspects of the environment unique to each individual twin influenced food preferences. This finding suggests that shared environmental experiences that influence food preferences in childhood may not have effects that persist into adulthood.

Differential bitterness in capsaicin, piperine, and ethanol associates with polymorphisms in multiple bitter taste receptor genes

To date, the majority of research exploring associations with genetic variability in bitter taste receptors has understandably focused on compounds and foods that are predominantly or solely perceived as bitter. However, other chemosensory stimuli are also known to elicit bitterness as a secondary sensation. Here we investigated whether TAS2R variation explains individual differences in bitterness elicited by chemesthetic stimuli, including capsaicin, piperine and ethanol. We confirmed that capsaicin, piperine and ethanol elicit bitterness in addition to burning/stinging sensations. Variability in perceived bitterness of capsaicin and ethanol were significantly associated with TAS2R38 and TAS2R3/4/5 diplotypes. For TAS2R38, PAV homozygotes perceived greater bitterness from capsaicin and ethanol presented on circumvallate papillae, compared to heterozygotes and AVI homozygotes. For TAS2R3/4/5, CCCAGT homozygotes rated the greatest bitterness, compared to heterozygotes and TTGGAG homozygotes, for both ethanol and capsaicin when presented on circumvallate papillae. Additional work is needed to determine how these and other chemesthetic stimuli differ in bitterness perception across concentrations and presentation methods. Furthermore, it would be beneficial to determine which TAS2R receptors are activated in vitro by chemesthetic compounds.