Genetic variation in TAS2R38 bitterness receptor is associated with body composition in Korean females

Bitterness-receptor gene TAS2R38 is associated with taste sensitivity and dietary behaviour, and is known to play a critical role in adiposity. However, evidence regarding body composition from a large cohort is lacking. This study aimed to ascertain whether TAS2R38 rs10246939 C > T bitterness genetic variation is associated with body composition in Korean individuals. The TAS2R38 rs10246939 genotypes, anthropometric measurements, and body composition of 1,843 males and 1,801 females from the Korean Genome and Epidemiology Study were analysed. Findings suggested that there was a significant difference in body fat components by TAS2R38 genotype. Furthermore, the bitterness genotype exhibited a positive association with adiposity markers in females. The TT genotype showed greater body mass index, body fat percentage, and degree of obesity than those with the C allele. However, such an association was not observed in males. In conclusion, this study suggests that TAS2R38 rs10246939 is associated with fat tissue markers in Korean females.

The Bittersweet Symphony of COVID-19: Associations between TAS1Rs and TAS2R38 Genetic Variations and COVID-19 Symptoms

The innate immune system is crucial in fighting SARS-CoV-2 infection, which is responsible for coronavirus disease 2019 (COVID-19). Therefore, deepening our understanding of the underlying immune response mechanisms is fundamental for the development of novel therapeutic strategies. The role of extra-oral bitter (TAS2Rs) and sweet (TAS1Rs) taste receptors in immune response regulation has yet to be fully understood. However, a few studies have investigated the association between taste receptor genes and COVID-19 symptom severity, with controversial results. Therefore, this study aims to deepen the relationship between COVID-19 symptom presence/severity and TAS1R and TAS2R38 (TAS2Rs member) genetic variations in a cohort of 196 COVID-19 patients. Statistical analyses detected significant associations between rs307355 of the TAS1R3 gene and the following COVID-19-related symptoms: chest pain and shortness of breath. Specifically, homozygous C/C patients are exposed to an increased risk of manifesting severe forms of chest pain (OR 8.11, 95% CI 2.26-51.99) and shortness of breath (OR 4.83, 95% CI 1.71-17.32) in comparison with T/C carriers. Finally, no significant associations between the TAS2R38 haplotype and the presence/severity of COVID-19 symptoms were detected. This study, taking advantage of a clinically and genetically characterised cohort of COVID-19 patients, revealed TAS1R3 gene involvement in determining COVID-19 symptom severity independently of TAS2R38 activity, thus providing novel insights into the role of TAS1Rs in regulating the immune response to viral infections.

An Investigation of TAS2R38 Haplotypes, Dietary Intake, and Risk Factors for Chronic Disease in the Canadian Longitudinal Study on Aging

BACKGROUND

Variation in common taste receptor type 2 member 38 (TAS2R38) haplotypes is associated with bitter-taste sensitivity, but associations with dietary intake and risk factors for chronic disease are inconsistent.

OBJECTIVES

To determine whether common TAS2R38 haplotypes are associated with dietary intake and risk factors for chronic disease using cross-sectional data from the Canadian Longitudinal Study on Aging (n = 26,090). Outcomes were assessed among the full sample and stratified by sex.

METHODS

Taster status was determined from TAS2R38 haplotypes, and the respondents were classified as supertasters, tasters, and nontasters. Primary outcome variables were the consumption frequencies of vegetables, sweet-tasting foods, alcoholic beverages, and visceral adiposity index (VAI). Secondary outcome variables were the individual VAI components. Multivariable regression models adjusted for sociodemographic and lifestyle factors were used to assess associations between the taster status and outcome variables.

RESULTS

Among the sample, 5655, 12,821, and 7614 respondents were classified as supertasters, tasters, and nontasters, respectively. Vegetable consumption was significantly higher among nontasters than among supertasters (1.23 ± 0.26 and 1.20 ± 0.22, respectively, P = 0.02). Among males, the consumption of sweet-tasting foods (0.40 ± 8.80 and 0.38 ± 7.55, P = 0.02) and green salad (0.35 ± 0.31 and 0.33 ± 0.27, P = 0.02) was also higher for nontasters than supertasters. Nontasters were more likely to be regular alcohol consumers compared with supertasters among the full sample (odds ratio [95% confidence interval]: 1.12 [1.03, 1.22]; P = 0.01) and among females (OR: 1.13; 95% CI: 1.01, 1.27; P = 0.04). No significant associations were observed between TAS2R38 haplotypes and VAI, although high-density lipoprotein cholesterol was significantly lower among supertasters than nontasters (1.45 ± 0.59 and 1.47 ± 0.63, respectively; P = 0.04).

CONCLUSIONS

Among middle- to older-aged adults, minor associations are observed between TAS2R38 haplotypes, dietary intake, and high-density lipoprotein cholesterol. Genetic predisposition to bitter-taste sensitivity is linked to diet; however, further research is needed to understand the relevance for chronic disease risk.

Consumer Liking of Turnip Cooked by Different Methods: The Influence of Sensory Profile and Consumer Bitter Taste Genotype

Brassica vegetables are bitter, predominantly because they contain bitter-tasting glucosinolates. Individuals with high bitter taste sensitivity are reported to have lower consumption of bitter vegetables. Studies reported that cooking methods can alter the sensory characteristics of vegetables, increasing acceptability. This study investigated consumer liking of turnip cooked by four methods (boiled-pureed, roasted, steamed-pureed and stir-fried) and related this to sensory characteristics. Additionally, this study examined the effect of the bitter taste genotype on taste perception and liking of the cooked turnip samples. Participants (n = 74) were recruited and the TAS2R38 genotype was measured. Liking, consumption intent, perception of bitterness and sweetness of turnip were evaluated. A sensory profile of the cooked turnip variants was also determined by a trained sensory panel. There were significant differences in the overall (p = 0.001) and taste (p = 0.002) liking between cooking methods. Turnip liking was increased when preparation led to sweeter taste profiles. The TAS2R38 genotype had a significant effect on bitter perception (p = 0.02) but did not significantly affect taste liking. In conclusion, the cooking method affected turnip liking, and the bitter perception in turnip was influenced by the TAS2R38 genotype. However, taste sensitivity did not predict turnip liking in this UK adult cohort.

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.

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.

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.

Analysis of Genetic Polymorphism of Bitter Taste Receptor TAS2R38 and TAS2R46, and Its Relationship with Eating and Drinking Habits in Japanese ToMMo Subjects

Human type 2 taste receptor (TAS2R) genes encode bitter-taste receptors that are activated by various bitter ligands. It has been said that TAS2R38 may detect bitter substances and then suppress their intake by controlling gustatory or digestive responses. The major haplotypes of TAS2R38 involve three non-synonymous, closely-linked single-nucleotide polymorphisms (SNPs), leading to three amino acid substitutions (A49P, V262A and I296V) and resulting in a PAV or AVI allele. The allele frequency of AVI/PAV was 0.42/0.58 in this study. The genotype frequency distributions of TAS2R38 were 18.32%, 46.95% and 33.95% for AVI/AVI, AVI/PAV and PAV/PAV, respectively, and were in Hardy-Weinberg equilibrium. Five haplotype combinations of minor alleles were identified: AVI/AAV, AVI/AVV, AAI/PAV, AVI/PVV, AVI/AAI, with corresponding frequencies of 0.49%, 0.10%, 0.10%, 0.05%, 0.05%, respectively, in 2,047 Japanese Tohoku Medical Megabank Organization (ToMMo) subjects (2KJPN). The 16 subjects with these minor alleles were excluded from the questionnaire analysis, which found no significant differences among the major TAS2R38 genotypes (AVI/AVI, AVI/PAV and PAV/PAV) in the intake frequency of cruciferous vegetables or in the frequency of drinking alcohol. This result differs from previous data using American and European subjects. This is the first study to analyze the relationship between TAS2R38 genotype and the eating and drinking habits of Japanese subjects. It was also shown that there were no relationships at all between the genetic polymorphism of TAS2R46 and the phenotypes such as clinical BMI, eating and drinking habits among the 3 genotypes of TAS2R46 (∗/∗, ∗/W, W/W) at position W250∗ (∗stop codon).

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.

Genetic variations in the bitter taste receptor gene TAS2R38 are related to cigarette smoking behavior in Han Chinese smokers

BACKGROUND

Smoking behavior is influenced by multiple genes, including the bitter taste gene TAS2R38. It has been reported that the correlation between TAS2R38 and smoking behavior has ethnicity-based differences. However, the TAS2R38 status in Chinese smokers is still unclear.

OBJECTIVE

This study aims to investigate the possible relationship between genetic variations in TAS2R38 (A49P, V262A and I296V) and smoking behaviors in the Han Chinese population.

METHODS

The haplotype analyses were performed and smoking behavior questionnaire was completed by 1271 individuals. Genetic association analyses for smoking behavior were analyzed using chi-square test. Further, for investigating the molecular mechanism of TAS2R38 variants effect on smoking behavior, we conducted TAS2R38-PAV and TAS2R38-AVI expression plasmids and tested the cellular calcium assay by cigarette smoke compounds stimulus in HEK293.

RESULTS

Significant associations of genetic variants within TAS2R38 were identified with smoking behavior. We found a higher PAV/PAV frequency than AVI/AVI in moderate and high nicotine dependence (FTND ≥ 4; X² = 4.611, 1 df, p = 0.032) and strong cigarette smoke flavor intensity preference (X² = 4.5383, 1 df, p = 0.033) in participants. Furthermore, in the in vitro cellular calcium assay, total particle matter (TPM), N-formylnornicotine and cotinine, existing in cigarette smoke, activated TAS2R38-PAV but not TAS2R38-AVI-transfected cells.

CONCLUSION

Our data highlights that genetic variations in TAS2R38 are related to smoking behavior, especially nicotine dependence and cigarette smoke flavor intensity preference. Our findings may encourage further consideration of the taste process to identify individuals susceptible to nicotine dependence, particularly Han Chinese smokers.

Does genetic variation in a bitter taste receptor gene alter early smoking behaviours in adolescents and young adults?

BACKGROUND AND AIMS

Variation in the TAS2R38 taste receptor gene alters the ability to taste bitter compounds. We tested whether TAS2R38 variation influences early smoking behaviours in adolescence, a critical period of acquisition when taste may influence the natural course of tobacco use.

DESIGN AND PARTICIPANTS

Observational study (Nicotine Dependence in Teens [NDIT]). Cox proportional hazards models were conducted using data from European ancestry adolescent participants who initiated smoking during follow-up (n = 219, i.e. incident smokers). In young adulthood, cross-sectional analyses were restricted to European ancestry self-reported current smokers at age 24 (n = 148).

SETTING

Montréal, Canada.

MEASUREMENTS

In adolescents, the rates of attaining early smoking milestones were estimated for tasters {PAV diplotypes (i.e. PAV/PAV or PAV/AVI)} versus non-tasters {AVI diplotype (i.e. AVI/AVI)}. In young adults, associations between tasting status and a nicotine intake biomarker (cotinine + 3'hydroxycotinine) and past-week cigarette consumption were assessed.

FINDINGS

Among incident smokers, similar rates to first whole cigarette were found between the diplotype groups (hazard ratio [HR], 1.05; 95% confidence interval (CI), 0.75-1.48; P = 0.765). However, smokers with the PAV (vs AVI) diplotypes attained monthly smoking more rapidly (HR, 1.55; 95% CI, 1.04-2.32; P = 0.033) and had faster conversion to three different measures of tobacco dependence (International Classification of Diseases: HR, 2.29; 95% CI, 0.99-5.28; P = 0.052; modified Fagerström Tolerance Questionnaire: HR, 3.02, 95% CI, 1.04-8.79; P = 0.043; Hooked on Nicotine Checklist: HR, 1.87; 95% CI, 0.98-3.60; P = 0.059). At age 24, those with PAV (vs AVI) diplotypes had higher mean cotinine + 3'hydroxycotinine (197 vs 143 ng/mL; P = 0.053).

CONCLUSIONS

Adolescents with a genetic variation increasing their ability to taste bitter compounds appear to escalate more quickly to monthly smoking and tobacco dependence during adolescence and have higher nicotine intake in young adulthood versus those without that genetic variation.

The influence of TAS2R38 bitter taste gene polymorphisms on obesity risk in three racially diverse groups

Objectives

Bitter taste perception affects food preference, eating behavior, and nutrient intake. The purpose of this study was to investigate the contribution of bitter taste gene polymorphisms to body fatness as measured by percentage of body fat.

Method

Three common single nucleotide polymorphisms (SNPs) of the TAS2R38 gene which result in amino acid changes in the protein (A49P, V262A, and I296V), were studied in three racially diverse groups: European Americans n = 313, African Americans n = 109, and Asians n = 234.

Results

The allele frequencies of the three SNPs were similar to previous studies. The rare haplotypes, AAI and AAV, were found in high prevalence in the African American subgroup (22.94%) and European American subgroup (6.07%). The PROP non taster; AVI/AVI diplotype was associated with a higher risk of obesity in European American and Asian but not African American subjects after age adjustment.

Conclusions

TAS2R38 polymorphisms could be associated with obesity development. In addition to taste perception, nutrient sensing and energy metabolism should be studied in relation to bitter taste receptors to confirm the association between genetic polymorphisms and body fatness. Genetic polymorphisms, race, gender, and environmental factors such as dietary patterns could all contribute to body fat.

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.

The Associations Between Bitter and Fat Taste Sensitivity, and Dietary Fat Intake: Are They Impacted by Genetic Predisposition?

A relationship between bitter and fat taste sensitivity, CD36 rs1761667 and TAS2R38 has been demonstrated. However, research is scarce and does not take diet into account. This study aimed to explore associations between genetics, fat and bitter taste sensitivity and dietary fat intake in healthy UK adults. A cross-sectional study was carried out on 88 Caucasian participants (49 females and 39 males aged 35 ± 1 years; body mass index 24.9 ± 0.5 kg/m2). Bitter taste sensitivity was assessed using phenylthiocarbamide (PTC) impregnated strips and the general Labeled Magnitude Scale. Fat taste sensitivity was assessed by the Ascending Forced Choice Triangle Procedure and dietary intake with a semi-quantitative food frequency questionnaire. Genotyping for rs713598, rs1726866, rs10246939, and rs1761667 was performed. Participants with TAS2R38 PAV/PAV diplotype perceived PTC strips as more bitter than groups carrying AVI haplotypes (AVI/AVI, P = 1 × 10-6; AVI/AAV, P = 0.029). CD36 rs1761667 was associated with fat taste sensitivity (P = 0.008). A negative correlation between bitter taste sensitivity and saturated fat intake was observed (rs = -0.256, P = 0.016). When combining the CD36 genotypes and TAS2R38 diplotypes into one variable, participants carrying both TAS2R38 AVI haplotype and CD36 A allele had a higher intake of saturated fat compared to carriers of CD36 GG genotype or TAS2R38 PAV/PAV and PAV/AAV diplotypes (13.8 ± 0.3 vs. 12.6 ± 0.5%TEI, P = 0.047) warranting further exploration in a larger cohort.

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.

Association of polymorphisms in genes involved in enamel formation, taste preference and immune response with early childhood caries in Saudi pre-school children

Dental caries is primarily elicited by modifiable factors such as inadequate oral hygiene, poor dietary practices and deficient fluoride exposure. However, there is a growing body of evidence suggesting the profound influence of genetic factors in dental caries susceptibility. The present study aimed to evaluate the association between single nucleotide polymorphisms (SNPs) in ENAM (rs12640848), MMP20 (rs1784418), TAS2R38 (rs713598), and LTF (rs4547741) genes and early childhood caries (ECC) in Saudi preschool children. This case-control study enrolled 360 Saudi preschool children (262 with ECC and 98 caries-free). Data on environmental factors were collected through a questionnaire. However, caries experience and oral hygiene data were obtained during clinical examination. Buccal swab samples were collected for DNA extraction and SNPs were genotyped using PCR and DNA sequencing. Children with ECC were compared to caries free children (control), then they were categorized into two categories based on ECC severity as follows; non-severe ECC (NS-ECC), and severe-ECC (S-ECC). Association between the SNPs, ECC, NS-ECC, and S-ECC was reported as an odds ratio (OR) with a 95% confidence interval (CI). The majority of the children (72.8%) exhibited ECC (31.7% NS-ECC and 41.1% S-ECC) with mean dmft of 4.20 ± 4.05. Multivariate analyses of environmental factors showed that nocturnal feeding was a risk factor for ECC (P = 0.008). Poor oral hygiene was also a risk factor for both NS-ECC and S-ECC (ECC: P < 0.0001, NS-ECC: P = 0.032 and S-ECC: P < 0.0001). Univariate analysis showed that the AG genotype of rs1784418 of MMP20 gene was protective against ECC (OR = 0.532; 95% CI = 0.316-0.897, P = 0.018) and against NS-ECC (OR = 0.436; 95% CI = 0.238-0.798, P = 0.007). When environmental risk factors for ECC were included as covariates during multivariate analysis, AG variant in rs1784418 of MMP20 gene remained less frequent in NS-ECC cases compared to controls with borderline significance (OR = 0.542; 95% CI = 0.285-1.033, P = 0.063). Our findings concluded that MMP20 rs1784418 SNP might be associated with protection against ECC in Saudi preschool children.

Expanding the role of bitter taste receptor in extra oral tissues: TAS2R38 is expressed in human adipocytes

Increasing evidence indicates that taste receptors mediate a variety of functions in extra-oral tissues. The present study investigated the expression of bitter taste receptor TAS2R38 in human adipocytes, the possible link with genetic background and the role of TAS2R38 in cell delipidation and lipid accumulation rate in vitro. Subcutaneous (SAT) and visceral (VAT) adipose tissues were collected in 32 obese and 18 lean subjects. The TAS2R38 gene expression and protein content were examined in whole tissues, differentiated adipocytes and stroma-vascular fraction cells (SVF). The P49A SNP of TAS2R38 gene was determined in each collected sample. The effect of two bitter agonists (6-n-propylthiouracil and quinine) was tested. TAS2R38 mRNA was more expressed in SAT and VAT of obese than lean subjects and the expression/protein content was greater in mature adipocytes. The expression levels were not linked to P49A variants. In in vitro differentiated adipocytes, bitter agonists induced a significant delipidation. Incubation with 6-n-propylthiouracil induced an inhibition of lipid accumulation rate together with an increase in TAS2R38 and a decrease in genes involved in adipocyte differentiation. In conclusion, TAS2R38 is more expressed in adipocytes of obese than lean subjects and is involved in differentiation and delipidation processes.

The effects of taste sensitivity and repeated taste exposure on children's intake and liking of turnip (Brassica rapa subsp. rapa); a bitter Brassica vegetable

Low consumption of vegetables in children is a concern around the world, hence approaches aimed at increasing intake are highly relevant. Previous studies have shown that repeated taste exposure is an effective strategy to increase vegetable acceptance. However, few studies have examined the effect of repeated taste exposure on children varying in bitter taste sensitivity. This study investigated the influence of taste genotypes and phenotypes on the effects of repeated taste exposure to a Brassica vegetable. 172 preschool children aged 3-5 years were recruited into this study. Turnip was selected as the target vegetable and parents completed a questionnaire to ensure unfamiliarity. During the intervention, children were exposed to steamed-pureed turnip for 10 days (once/day). Intake and liking were measured before, during and after the intervention, and a follow-up was done 3 months post-intervention. Taste genotypes (TAS2R38 and gustin (CA6) genotypes) and taste phenotypes (PROP taster status and fungiform papillae density) were determined. There was a significant effect of exposure shown by significant increases in intake (p < 0.001) and liking (p = 0.008) post-intervention; however, there were no significant effects of taste genotypes or phenotypes on intake and liking. In summary, repeated taste exposure is confirmed to be a good strategy to increase vegetable acceptance in children, regardless of bitter taste sensitivity.

The expression of bitter taste receptor TAS2R38 in patients with chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a frequent disease with high social impact and multifactorial pathogenesis. Recently, the bitter taste receptor TAS2R38 has been described to play a role in upper airway innate mucosal defense. The aim was to determine the localization and expression of the TAS2R38 in the selected cell lines and tissue collected from patient suffered from CRS as well as to correlate the results with clinical data. Moreover, the purpose was the estimation of the TAS2R38 distribution changes during acute and CRS. Forty-two patients undergoing nasal surgery were enrolled in the study. The TAS2R38 expression was assessed in the collected tissues using immunohistochemistry and immunocytochemistry methods. The western blot analysis was performed on human cell lines HeLa, MCF7, MDA-MB-231 to assess the location of the TAS2R38 protein. Moreover, the HeLa cell line was used as a model of acute inflammation induces by lipopolysaccharide. Immunohistochemistry analysis displayed a statistically significant difference of TAS2R38 level in the patients with CRS compared to healthy control and was different in CRS with and without nasal polyps. The results showed the abundance of TAS2R38 receptor in the cell nucleus in patients with CRS and cell lines. The variance in TAS2R38 receptor expression in two CRS types suggests their different pathogenesis. The first time in literature, we confirmed the presence of plasma membrane TAS2R38 receptor in the cell nuclei in CRS as well as in cell lines, what strongly suggests the different than membrane TAS2R38 function.

[Genetic Predisposition to Early Myocardial Infarction]

The aim of the study was to identify the features of the genetic structure of myocardial infarction (MI) susceptibility depending on age ("early MI" denoting individuals who had the first MI before the age of 60 years, and "late MI" the group of patients with the first "MI after 60 years"). A total of 355 patients were examined (n = 121 early MI and n = 234 late MI) and 285 residents of the Siberian region (as a control group). Genotyping of 58 single nucleotide variants (SNPs) was performed using mass spectrometry using the Agena (ex Sequenom) MassARRAY® System. Statistical analysis was performed using Statistica 8.0 ("StatSoft Inc.", USA), as well as the "stats" and "genetics" packages in the R environment. The regulatory potential of SNPs was evaluated using the rSNPBase online service (http://rsnp.psych.ac.cn/). eQTL loci were identified using data from the Genotype-Tissue Expression (GTEx) project (http://www.gtexportal.org/) and the Blood eQTL online service (https://genenetwork.nl/bloodeqtlbrowser/). The GG genotype of ITGA4 rs1143674, the CC genotype of CDKN2B-AS1 rs1333049, and the CC genotype of KIAA1462 rs3739998, are generally associated with MI. The AA genotype of ADAMDEC1 rs3765124 (OR = 2.03; 95% CI 1.23-3.33; p = 0.004) and the GG genotype of AQP2 rs2878771 (OR = 2.24; 95% CI 1.23-4.09; p = 0.006) are associated with the development of MI at an early age, and the TT genotype of TAS2R38 rs1726866 (OR = 1.82; 95% CI 1.11-2.89; p = 0.009) was the high-risk genotype for the late MI. Genetic variants associated with MI are regulatory SNP (rSNP) and affect the affinity of DNA binding to transcription factors, carry out post-transcriptional control of gene activity and change the level of gene expression in various tissues. Thus, early and late MI are based on both common genetic variants of ITGA4, CDKN2B-AS1, KIAA1462 genes and specific ones (ADAMDEC1 and AQP2 for early MI and TAS2R38 for late MI).

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.

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.

The roles of genes in the bitter taste

The aims of this review were to understand the roles of bitter taste genes in humans. Some of the peoples have the capacity to taste some chemical substance such as phenylthiocarbamide (PTC) while others cant not based on the dietary hazards and food preferences. There are two alleles responsible to express these phenotypes which are homozygous recessive. In human TAS2R38 genes located on the chromosome number 7 and consist of different nucleotide polymorphism that related to detection of the phenotype of different chemical compounds such as 6-n-propylthiouracil (PROP) and phenylthiocarbamide bitterness and this Gene is the member of the TAS2R genes which are eleven pseudogenes and twenty that has roles in many biological processes.

There are many factors that affect the bitter taste such as food, age, sex, and different diseases. The mechanism of food bitter taste and genotype of TAS2R38 until know not well understood due to that the proof of relation between bitter taste sensitivity and food is harmful. there are many different diseases can impact the influence of taste such as neoplasm and lifestyle such as consumption of alcohol along with the use of medication, head trauma, upper tract infections. On the other hand, A relation between TAS2R38 genotype and meal preferences has been observed among children, however, no associations have been mentioned among older adults. Some previous research proved some vital points that show an association between type 1 of diabetes and phenylthiocarbamide (PTC) but other studies cannot demonstrate that. However, of other disease such as obesity is controversial but other studies reported to the relationship between them.

Functional divergence of the bitter receptor TAS2R38 in Sulawesi macaques

ABSTRACT

Bitter perception is mediated by G protein-coupled receptors TAS2Rs and plays an important role in avoiding the ingestion of toxins by inducing innate avoidance behavior in mammals. One of the best-studied TAS2Rs is TAS2R38, which mediates the perception of the bitterness of synthetic phenylthiocarbamide (PTC). Previous studies of TAS2R38 have suggested that geographical separation enabled the independent divergence of bitter taste perception. The functional divergence of TAS2R38 in allopatric species has not been evaluated. We characterized the function of TAS2R38 in four allopatric species of Sulawesi macaques on Sulawesi Island. We found variation in PTC taste perception both within and across species. In most cases, TAS2R38 was sensitive to PTC, with functional divergence among species. We observed different truncated TAS2R38s that were not responsive to PTC in each species of Macaca nigra and M. nigrescens due to premature stop codons. Some variants of intact TAS2R38 with an amino acid substitution showed low sensitivity to PTC in M. tonkeana. Similarly, this intact TAS2R38 with PTC-low sensitivity has also been found in humans. We detected a shared haplotype in all four Sulawesi macaques, which may be the ancestral haplotype of Sulawesi macaques. In addition to shared haplotypes among Sulawesi macaques, other TAS2R38 haplotypes were species-specific. These results implied that the variation in TAS2R38 might be shaped by geographical patterns and local adaptation.

OPEN RESEARCH BADGES

This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.908jf3r.

Variation in the TAS2R38 Bitterness Receptor Gene Was Associated with Food Consumption and Obesity Risk in Koreans

Bitterness-sensing protein taste receptor type-2 member 38 (TAS2R38, T2R38) mediates taste perception and various physiological responses, including energy- and adiposity-related mechanisms. This study examined whether the genetic variant rs10246939 C > T in TAS2R38 was associated with food intake and body size as well as obesity risk. Data from the Korean Multi-Rural Communities Cohort study (1338 males and 2229 females) were analyzed to obtain the intake of six food groups, alcohol consumption, smoking status and anthropometric measurements, including height, weight, waist and hip circumference, and body mass index (BMI), according to the rs10246939 genotype. Findings suggested that females with the TT genotype consumed more fruit (adjusted p = 0.025) and had significantly higher body weights (adjusted p = 0.046) and BMIs (adjusted p = 0.003) than individuals with other genotypes. Having the TT genotype also increased the risk of obesity by 1.75-fold (95% confidence interval: 1.31–2.36) in females. The genetic variation had a minimal influence on the males’ dietary intake, but tended to increase the adiposity risk. In conclusion, TAS2R38 rs10246939 variation was associated with Koreans’ dietary intake and increased their risk of obesity. Although more detailed statistical analyses in the larger cohort are required, current study suggested that, as a genetic predictive marker, TAS2R38 bitterness receptor variations may have a large implication in obesity prevention and treatment.

TAS2R38 bitter taste genotype is associated with complementary feeding behavior in infants

Background

Genetically mediated sensitivity to bitter taste has been associated with food preferences and eating behavior in adults and children. The aim of this study was to assess the association between TAS2R38 bitter taste genotype and the first complementary food acceptance in infants.

Parents of healthy, breastfed, term-born infants were instructed, at discharge from the nursery, to feed their baby with a first complementary meal of 150 mL at 4 to 6 months of age. They recorded the day when the child ate the whole meal in a questionnaire. Additional data included food composition, breastfeeding duration, feeding practices, and growth at 6 months. Infants’ TAS2R38 genotypes were determined at birth, and infants were classified as “bitter-insensitive” (genotype AVI/AVI) and “bitter-sensitive” (genotypes AVI/PAV or PAV/PAV).

Results

One hundred seventy-six infants and their mothers were enrolled; completed data were available for 131/176 (74.4%) infants (gestational age 39.3 ± 1.1 weeks, birth weight 3390 ± 430 g). Bitter-insensitive were 45/131 (34.3%), and bitter-sensitive were 86/131 (65.6%). Thirty-one percent of bitter-insensitive infants consumed the whole complementary meal at first attempt, versus 13% of bitter-sensitive ones (p = 0.006). This difference was significant independently of confounding variables such as sex, breastfeeding, or foods used in the meal. Growth at 6 months did not differ between the two groups.

Conclusions

Differences in TAS2R38 bitter taste gene were associated with acceptance of the first complementary food in infants, suggesting a possible involvement in eating behavior at weaning.

Genotyping Analysis of Bitter-Taste Receptor Genes TAS2R38 and TAS2R46 in Japanese Patients with Gastrointestinal Cancers

Type-2 bitter-taste receptors (TAS2Rs) are important for the evaluation of food quality and the nutritional control in animals. Mutations in some TAS2Rs including TAS2R38 are known to increase susceptibility to various diseases. However, the involvement of TAS2Rs in cancers has not been well understood. We conducted a pilot study by genotyping two TAS2R genes, TAS2R38 and TAS2R46, in Japanese cancer patients diagnosed with the following types of cancer: biliary tract cancer, hepatocellular carcinoma, pancreatic cancer, colorectal cancer and gastric cancer. We selected the two TAS2Rs because they carry virtually non-functional alleles in human populations. We found that cancer risk is not associated with any TAS2R46 genotypes since there were no significant differences in genotype frequencies between cancer patients and controls. On the other hand, we confirmed that phenylthiocarbamide (PTC) non-tasters homozygous (AVI/AVI) for TAS2R38 were more frequent among Japanese cancer patients than those among controls as suggested in a previous study. The AVI/AVI genotype was therefore considered to increases cancer risk. In contrast, we also found that homozygous (PAV/PAV) PTC tasters are less frequent among cancer patients, suggesting that the PAV/PAV is a cancer resistant genotype that decreases cancer risk. Genotype frequencies for heterozygous AVI/PAV genotype were not significantly different between the two groups. It is suggested that the risk and resistance of cancers is antagonistically controlled by the two TAS2R38 alleles, PAV and AVI, rather than by the AVI allele alone.

In Vivo Biofilm Formation, Gram-Negative Infections and TAS2R38 Polymorphisms in CRSw NP Patients

OBJECTIVES

Among the predisposing factors implicated in the immune response to airway bacterial infections, genetic variations of the bitter taste receptor TAS2R38, which is expressed in the cilia of the human sinonasal epithelial cells, seem to be associated with susceptibility to chronic rhinosinusitis (CRS) and in vitro biofilm formation. Polymorphisms in TAS2R38 generate two common haplotypes: the nonfunctional AVI (Alanine, Valine, Isoleucine) and the functional PAV (Proline, Alanine, Valine) alleles, with the latter protecting against gram-negative sinonasal infections. The aim of this study is to investigate for the first time the relevance of TAS2R38 genetic variants in the susceptibility to bacterial infections associated with in vivo biofilm formation in chronic rhinosinusitis with nasal polyps (CRSwNP) patients.

STUDY DESIGN

A prospective study on 100 adult patients undergoing functional endoscopic sinus surgery (FESS) for CRSwNP.

METHODS

Propylthiouracile (PROP) testing and TAS2R38 genotyping were applied to characterize patients for receptor functionality. Sinonasal mucosa samples were processed for microbiological examination and biofilm detection.

RESULTS

The nonfunctional genotype is more frequent among CRS patients than in the general population (25% vs. 18.4%, P = 0.034). Airway gram-negative infections are primarily associated with the AVI haplotype (88.9% vs. 11.1% PAV/PAV-functional genotype, P = 0.023). Biofilm formation is prevalent in CRS patients with the AVI nontaster phenotype (62.5% vs. 33.3% PAV taster or supertaster phenotype, P = 0.05).

CONCLUSION

Our findings confirm an inverse correlation between TAS2R38 functionality and gram-negative infections in Italian patients with CRSwNP. In addition, for the first time we demonstrated a relationship between in vivo microbial biofilm and TAS2R38 receptor variants.

LEVEL OF EVIDENCE

2b. Laryngoscope, 128:E339-E345, 2018.

Variations in the bitterness perception-related genes TAS2R38 and CA6 modify the risk for colorectal cancer in Koreans

Bitterness perception is known to be an important factor in individuals' dietary behaviors and is also associated with the sensing of nutritious/noxious molecules for subsequent metabolic responses in multiple organs. Therefore, the genetic variation in bitterness sensing may be associated with diet-related diseases, including colorectal cancer (CRC). We investigated the influence of variations in the bitterness-sensing genes taste receptor type 2 member 38 (TAS2R38) and carbonic anhydrase 6 (CA6) on the consumption of food, tobacco and alcohol and the risk of CRC in Koreans. The study population consisted of 681 cases and 1361 controls, and their intake of vegetables, fruits, fiber, fat-food and sweets was analyzed. The genotypes for TAS2R38 A49P, V262A and I296V and CA6 rs2274333 A/G were assessed using the MassArray technique. Our findings suggested that the TAS2R38 diplotype, CA6 rs2274333 and their combined genotype had a negligible influence on dietary and alcohol intake. The combined TAS2R38-CA6 AVI/AVI-AA genotype was associated with higher tobacco consumption than the other genotypes in CRC cases only. However, the genetic variations were a significant risk factor for CRC. The TAS2R38 AVI/AVI diplotype and CA6 G allele were associated with a reduced risk of CRC. Moreover, when the combined genotypes of the subjects were analyzed, possessing both the variant diplotype/variant allele (AVI/AVI+G*) was associated with a greater reduction in the risk of CRC (adjusted OR = 0.49; 95%CI: 0.34-0.74). In summary, variations in the bitterness perception genes TAS2R38 and CA6 did not influence the examined food intake in Koreans. However, those genetic variants were a decisive modifying factor of CRC susceptibility.

Perceived 6-n-Propylthiouracil (PROP) Bitterness Is Associated with Dietary Sodium Intake in Female Japanese College Students

Despite the negative health consequences of a high sodium consumption, humans consume well above the recommended levels. This study examines whether or not the dietary intake of sodium was affected by individual variation of the perceived bitterness of 6-n-propylthiouracil (PROP), and examines the relationship between the perceived bitterness of PROP and the preferred NaCl concentration of broth. Female students (20-22 y old) were recruited from the university community. Genotypes of A49P and I296V polymorphism of the TAS2R38 bitter taste receptor were determined for each subject. Samples containing NaCl, PROP or broth in 5-mL portions were evaluated by sensory testing. The participants completed a food record for each diet. Our results indicate that the individuals perceiving PROP to be more bitter had consumed a greater amount of dietary sodium. In contrast, there was no significant positive correlation between an individual's perceived saltiness and the dietary sodium intake. Those who perceived PROP to be more bitter preferred a broth containing a higher concentration of NaCl. All of these correlations were apparent even after those subjects with TAS2R38 AI/AI homozygotes (PROP non-taster) had been excluded. In conclusion, the results of this study suggest that a factor affecting the bitter rating of PROP other than the AI/AI homozygotes of TAS2R38 contributes to the variation in sodium intake and the preference for salty food.

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.

The correlation of TAS2R38 gene variants with higher risk for chronic rhinosinusitis in Polish patients

BACKGROUND

Bitter taste receptors (T2Rs), especially T2R38s appear as innovative regulators of innate immunity in the respiratory system. The single nucleotide polymorphisms (SNPs) in TAS2R38 gene may contribute to individual differences in susceptibility to respiratory infections especially chronic rhinosinusitis (CRS). TAS2R38 genotypes distribution varies by geographic region, race and ethnicity. The aim of the preliminary study was the identification of SNPs in TAS2R38 encoding genes in Polish patients with CRS and finding potential correlation with CRS phenotypes.

MATERIAL AND METHODS

The preliminary study contained 20 CRS patients undergoing functional endoscopic sinus surgery (FESS). Fresh sinus mucosa (SM) was obtained during FESS in CRS patients. Patients were genotyped for TAS2R38 using Sanger method and the genotype occurrences of the clinically recalcitrant CRS cohort was evaluated. Analysis of TAS2R38 expression in SM of CRS patients was performed using immunohistochemistry (IHC).

RESULTS

T2R38 was highly expressed in SM of CRS patients. Patients with CRS demonstrated both common genotypes PAV, AVI. The heterozygotes frequency (AVI/PAV) was the highest. The protective genotype (PAV/PAV) was noticed in the lowest frequency and connected with lower average value of CT score compare to AVI/AVI genotypes (p=0.01).

CONCLUSIONS

The work presented in this study provides the hypothesis that airway bitter T2Rs are an innovative sphere of human respiratory innate protection. TAS2R38 polymorphism may influence the susceptibility to CRS. The AVI haplotypes are an independent risk factors for CRS. Additionally, the bitter taste receptors and related signalling pathways might create an unique group of therapeutic targets to treat CRS.

Is the Association Between Sweet and Bitter Perception due to Genetic Variation?

Perceived intensities of sweetness and bitterness are correlated with one another and each is influenced by genetics. The extent to which these correlations share common genetic variation, however, remains unclear. In a mainly adolescent sample ( n = 1901, mean age 16.2 years), including 243 monozygotic (MZ) and 452 dizygotic (DZ) twin pairs, we estimated the covariance among the perceived intensities of 4 bitter compounds (6- n -propylthiouracil [PROP], sucrose octa-acetate, quinine, caffeine) and 4 sweeteners (the weighted mean ratings of glucose, fructose, neohesperidine dihydrochalcone, aspartame) with multivariate genetic modeling. The sweetness factor was moderately correlated with sucrose octa-acetate, quinine, and caffeine ( rp = 0.35-0.40). This was mainly due to a shared genetic factor ( rg = 0.46-0.51) that accounted for 17-37% of the variance in the 3 bitter compounds' ratings and 8% of the variance in general sweetness ratings. In contrast, an association between sweetness and PROP only became evident after adjusting for the TAS2R38 diplotype ( rp increased from 0.18 to 0.32) with the PROP genetic factor accounting for 6% of variance in sweetness. These genetic associations were not inflated by scale use bias, as the cross-trait correlations for both MZ and DZ twins were weak. There was also little evidence for mediation by cognition or behavioral factors. This suggests an overlap of genetic variance between perceptions of sweetness and bitterness from a variety of stimuli, which includes PROP when considering the TAS2R38 diplotype. The most likely sources of shared variation are within genes encoding post-receptor transduction mechanisms common to the various taste G protein-coupled receptors.

Association of TAS2R38 variants with sweet food intake in children aged 1-6 years

We aimed at studying whether genetic variants of the TAS2R38 gene are associated with energy intake from sweet tasting foods, total energy and macronutrient intake and body weight in children. Children (n = 691) from five European countries were genotyped for the first variant site rs713598 of the TAS2R38 bitter receptor gene. Three-day dietary records were obtained yearly from one to six years of age. Foods were categorized in sweet and non-sweet-tasting. Mixed models were used to describe group differences in food and nutrient intake and BMI z-score over time. TAS2R38 genotype was related to energy intake from sweet tasting foods: Children with PP and PA genotype consumed an average 83 kJ/d (95% CI 21 to 146; p = 0.009) more sweet tasting foods than children with AA genotype and a mean 56 kJ/d (95% CI 15 to 98; p = 0.007) more energy from energy dense sweet products. Intake of sweet tasting foods was lower in girls than boys and differed between countries. TAS2R38 genotype was not associated with the intake of energy, macronutrients, sugar, single food groups and BMI z-score. Despite many other factors influencing food preference and intake in children, actual intake of sweet food items is associated with TAS2R38 genotype. Children with PP or PA genotype consume more (energy dense) sweet tasting foods.

Next generation semiconductor based sequencing of bitter taste receptor genes in different pig populations and association analysis using a selective DNA pool-seq approach

Taste perception in animals affects feed intake and may influence production traits. In particular, bitter is sensed by receptors encoded by the family of TAS2R genes. In this research, using a DNA pool-seq approach coupled with next generation semiconductor based target resequencing, we analysed nine porcine TAS2R genes (TAS2R1, TAS2R3, TAS2R4, TAS2R7, TAS2R9, TAS2R10, TAS2R16, TAS2R38 and TAS2R39) to identify variability and, at the same time, estimate single nucleotide polymorphism (SNP) allele frequencies in several populations and testing differences in an association analysis. Equimolar DNA pools were prepared for five pig breeds (Italian Duroc, Italian Landrace, Pietrain, Meishan and Casertana) and wild boars (5-10 individuals each) and for two groups of Italian Large White pigs with extreme and divergent back fat thickness (50 + 50 pigs). About 1.8 million reads were obtained by sequencing amplicons generated from these pools. A total of 125 SNPs were identified, of which 37 were missense mutations. Three of them (p.Ile53Phe and p.Trp85Leu in TAS2R4; p.Leu37Ser in TAS2R39) could have important effects on the function of these bitter taste receptors, based on in silico predictions. Variability in wild boars seems lower than that in domestic breeds potentially as a result of selective pressure in the wild towards defensive bitter taste perception. Three SNPs in TAS2R38 and TAS2R39 were significantly associated with back fat thickness. These results may be important to understand the complexity of taste perception and their associated effects that could be useful to develop nutrigenetic approaches in pig breeding and nutrition.

A potential trigger for pine mouth: a case of a homozygous phenylthiocarbamide taster

Pine mouth, also known as pine nut syndrome, is an uncommon dysgeusia that generally begins 12 to 48 hours after consuming pine nuts. It is characterized by a bitter metallic taste, usually amplified by the consumption of other foods, which lasts 2 to 4 weeks. Recent findings have correlated this disorder with the consumption of nuts of the species Pinus armandii, but no potential triggers or common underlying medical causes have been identified in individuals affected by this syndrome. We report a 23-year-old patient affected by pine mouth who also underwent a phenylthiocarbamide taste test and was found to be a taster for this compound. TAS2R38 genotyping demonstrated that this subject was a homozygous carrier of the proline-alanine-valine taster haplotype. We, therefore, hypothesize that homozygous phenylthiocarbamide taster status may be a potential contributor for pine mouth events. Although based on a single observation, this research suggests a connection between genetically determined bitter taste perception and the occurrence of pine nut dysgeusia events.

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

Background

The TAS2R38 gene is widely responsible for the well-known bimodal response to a family of bitter chemicals which includes 6-n-propylthiouracial (PROP). There are two common haplotypes of this gene, the recessive AVI and the dominant PAV, both of which are well studied. Conversely, the role of rare TAS2R38 haplotypes on bitter taste sensitivity has been notoriously difficult to study due to small sample sizes. Here we present PROP sensitivity data of 97 individuals that have been observed to carry rare haplotypes (AAV, AAI, PAI, PVI) of the TAS2R38 gene.

Results

Participants rated their bitter taste perception to a PROP filter disc then provided a buccal DNA sample from which the TAS2R38 gene was sequenced and analyzed. We found the prevalence of the PAV haplotype to be 42.3 %, AVI 53.1 %, AAV 2.5 %, AAI 1.2 %, PAI 0.8 % and PVI 0.1 %. We found that the AAI, AAV, and PAI haplotypes present intermediate taste sensitivity.

Conclusions

These data are further evidence that bitter taste sensitivity to PROP exists as a broad range, and not exclusively as nontasters, medium tasters, and supertasters.

An alternative laboratory designed to address ethical concerns associated with traditional TAS2R38 student genotyping

The TAS2R38 alleles that code for the PAV/AVI T2R38 proteins have long been viewed as benign taste receptor variants. However, recent studies have demonstrated an expanding and medically relevant role for TAS2R38. The AVI variant of T2R38 is associated with an increased risk of both colorectal cancer and Pseudomonas aeruginosa-associated sinus infection and T2R38 variants have been implicated in off-target drug responses. To address ethical concerns associated with continued student TAS2R38 gene testing, we developed an alternative to the traditional laboratory genotyping exercise. Instead of determining their own genotype, introductory level students isolated plasmid DNA containing a section of the human TAS2R38 gene from Escherichia coli. Following PCR-mediated amplification of a section of the TAS2R38 gene spanning the SNP at position 785, students determined their assigned genotype by restriction enzyme digestion and agarose gel electrophoresis. Using the course wide genotype and phenotype data, students found that there was an association between TAS2R38 genotype and the age of persistent P. aeruginosa acquisition in cystic fibrosis "patients." Assessment data demonstrated that students taking part in this new TAS2R38 laboratory activity made clear learning gains.

The gustin (CA6) gene polymorphism, rs2274333 (A/G), is associated with fungiform papilla density, whereas PROP bitterness is mostly due to TAS2R38 in an ethnically-mixed population

PROP responsiveness is associated with TAS2R38 haplotypes and fungiform papilla density. Recently, we showed that a polymorphism in the gene coding for the salivary trophic factor, gustin (CA6), affects PROP sensitivity by acting on cell growth and fungiform papillae maintenance, in a genetically homogeneous cohort. Since population homogeneity can lead to over estimation of gene effects, the primary aim of the present work was to confirm gustin's role in PROP bitterness intensity and fungiform papillae density in a genetically diverse population. Eighty subjects were genotyped for both genes by PCR techniques. PROP responsiveness was assessed by a filter paper method and fungiform papilla density was determined in each subject. As expected, PROP bitterness ratings were lower in individuals with the AVI/AVI diplotype of TAS2R38 than in individuals with PAV/PAV and PAV/AVI diplotypes. However, no differences in PROP bitterness among genotypes of the gustin gene, and no differences in the density of fungiform papillae related to TAS2R38 diplotype were found. In contrast, the density of fungiform papillae decreased as the number of minor (G) alleles at the gustin locus increased. In addition, the distribution of TAS2R38 genotypes within each gustin genotype group showed that the occurrence of recessive alleles at both loci was infrequent in the present sample compared to other populations. These findings confirm that papillae density is associated with gustin gene polymorphism, rs2274333 (A/G), in an ancestrally heterogeneous population, and suggest that variations in the frequency of allele combinations for these two genes could provide a salient explanation for discrepant findings for gustin gene effects across populations.

Crowdsourcing taste research: genetic and phenotypic predictors of bitter taste perception as a model

Understanding the influence of taste perception on food choice has captured the interest of academics, industry, and the general public, the latter as evidenced by the extent of popular media coverage and use of the term supertaster. Supertasters are highly sensitive to the bitter tastant propylthiouracil (PROP) and its chemical relative phenylthiocarbamide. The well-researched differences in taste sensitivity to these bitter chemicals are partially controlled by variation in the TAS2R38 gene; however, this variation alone does not explain the supertaster phenomenon. It has been suggested that density of papillae, which house taste buds, may explain supertasting. To address the unresolved role of papillae, we used crowdsourcing in the museum-based Genetics of Taste Lab. This community lab is uniquely situated to attract both a large population of human subjects and host a team of citizen scientists to research population-based questions about human genetics, taste, and health. Using this model, we find that PROP bitterness is not in any way predicted by papillae density. This result holds within the whole sample, when divided into major diplotypes, and when correcting for age, sex, and genotype. Furthermore, it holds when dividing participants into oft-used taster status groups. These data argue against the use of papillae density in predicting taste sensitivity and caution against imprecise use of the term supertaster. Furthermore, it supports a growing volume of evidence that sets the stage for hypergeusia, a reconceptualization of heightened oral sensitivity that is not based solely on PROP or papillae density. Finally, our model demonstrates how community-based research can serve as a unique venue for both study participation and citizen science that makes scientific research accessible and relevant to people’s everyday lives.