Bitter taste receptor polymorphisms and human aging

Investigating the Potential Influence of TAS2R16 Genetic Variants and Protein Levels on Multiple Sclerosis Development

The study aimed to investigate the association between the TAS2R16 gene (rs860170, rs978739, rs1357949), TAS2R16 serum levels, and multiple sclerosis (MS). A total of 265 healthy control subjects and 218 MS patients were included in the study. Single nucleotide polymorphisms (SNPs) were tested by real-time polymerase chain reaction (RT-PCR). The serum concentration of TAS2R16 was measured using the ELISA method. Analyses revealed that the TAS2R16 rs860170 TT genotype was statistically significantly less frequent in the MS group than in the control group (p = 0.041), and the CC genotype was statistically significantly more frequent in the MS group than in the control group (p < 0.001). In the most robust (codominant) model, the CC genotype was found to increase the odds of MS by ~27-fold (p = 0.002), and each C allele increased the odds of MS by 1.8-fold (p < 0.001). Haplotype analysis of the rs860170, rs978739, and rs1357949 polymorphisms showed that the C-C-A haplotype was associated with a ~12-fold increased odds of MS occurrence (p = 0.02). Serum TAS2R16 levels were elevated in the MS group compared to control subjects (p = 0.014). Conclusions: The rs860170, rs978739, and rs1357949 polymorphisms demonstrated that the C-C-A haplotype and elevated TAS2R16 serum levels can promote the development of MS. These preliminary findings underscore the importance of specific genetic variants, such as rs860170, rs978739, and rs1357949, in MS risk. Additionally, elevated TAS2R16 serum levels in MS patients suggest a potential role in MS pathogenesis. These findings provide insights into the genetic and molecular mechanisms underlying MS and pave the way for personalized diagnostic and therapeutic strategies. Integrating genetic and serum biomarker data in MS research offers promising avenues for improving clinical outcomes and advancing precision medicine approaches in the future.

TAS2R38 haplotypes, COVID-19 infection, and symptomatology: a cross-sectional analysis of data from the Canadian Longitudinal Study on Aging

The TAS2R38 gene is well known for its function in bitter taste sensitivity, but evidence also suggests a role in innate immunity. TAS2R38 may be relevant in coronavirus disease 2019 (COVID-19), but research findings are inconsistent. The objective of this study was to explore whether common TAS2R38 haplotypes are associated with COVID-19 infection and symptomatology in the Canadian Longitudinal Study on Aging (CLSA). Data from the CLSA COVID-19 Questionnaire and Seroprevalence sub-studies were utilized with CLSA genetic data for common TAS2R38 haplotypes related to bitter taste sensitivity. Haplotypes were categorized into three diplotype groups: [P]AV homozygotes, [P]AV/[A]VI heterozygotes, and [A]VI homozygotes. No significant differences were observed between diplotypes and COVID-19 infection frequency. Among self-reported COVID-19 cases (n = 76), and in uncorrected exploratory analyses, heterozygotes were less likely to report experiencing sinus pain compared to [P]AV homozygotes. Among seroprevalence-confirmed cases (n = 177), [A]VI homozygotes were less likely to report experiencing a sore/scratchy throat compared to [P]AV homozygotes. However, both observations were non-significant upon correction for multiple testing. In this study, TAS2R38 haplotypes were not significantly associated with COVID-19 infection or symptomatology. Nevertheless, in light of some exploratory patterns and conflicting evidence, additional research is warranted to evaluate links between TAS2R38 and innate immunity.

Association of TAS2R16 gene (rs860170, rs978739, rs1357949) polymorphisms and TAS2R16 serum levels in patients with age-related macular degeneration

BACKGROUND

The aim of this study is to determine the association of TAS2R16 (rs860170, rs978739, rs1357949) gene polymorphisms and TAS2R16 serum levels in patients with the occurrence of age-related macular degeneration (AMD).

METHODS

Subjects with early AMD, subjects with exudative AMD, and healthy controls participated in the study. DNA was isolated by salting out leukocytes from peripheral venous blood. Single nucleotide polymorphisms (SNPs) were analysed by RT-PCR. TAS2R16 levels were determined by enzyme-linked immunosorbent assay (ELISA) using the Abbexa Human Taste Receptor Type 2 Member 16 (TAS2R16) ELISA kit. Statistical data analysis was performed using "IBM SPSS Statistics 27.0" and SNPstats statistical data analysis programmes.

RESULTS

The TAS2R16 rs860170 TT genotype is statistically significantly less frequent in the exudative AMD group than in the control group, whereas the TAS2R16 rs860170 C allele gene is statistically significantly more frequent in the exudative AMD group. Each C allele of TAS2R16 rs860170 is associated with a 2.8-fold increased probability of occurrence of exudative AMD. The C allele of TAS2R16 rs860170 is statistically significantly more frequent in men and women with exudative AMD than in the control group. The C allele of TAS2R16 rs860170 is associated with a 2.8-fold increased odds of occurrence of exudative AMD in women and a 2.9-fold increased odds of occurrence of exudative AMD in men. In TAS2R16 (rs860170, rs978739, and rs1357949), the T-T-A haplotype is associated with a 2.6-fold decreased likelihood of developing early AMD and the T-T-A haplotype is associated with a 3.2-fold decreased likelihood of developing early AMD in women. For TAS2R16 (rs860170, rs978739, and rs1357949), carriers of the T-T-G and T-T-A haplotypes are associated with a 2.2- and 3.2-fold decreased probability of exudative AMD, respectively. Individuals with the C-C-A haplotype are 9.2-fold more likely to develop exudative AMD. Specifically, the C-C-A haplotype is associated with a 9.3-fold increased likelihood of exudative AMD in men. In contrast, women with the T-T-A haplotype are 5.6-fold less likely to develop exudative AMD.

CONCLUSION

TAS2R16 plays an important role in the development of AMD.

Generalised Periodontitis: Examining TAS2R16 Serum Levels and Common Gene Polymorphisms (rs860170, rs978739, rs1357949)

The objective of this study was to evaluate and compare the associations between TAS2R16 serum levels and common gene rs860170, rs978739, and rs1357949 polymorphisms in patients affected by generalized periodontitis. The study enrolled 590 patients: 280 patients with periodontitis and 310 healthy controls as a reference group. Patients underwent periodontal examination and radiographic analysis to confirm the periodontitis diagnosis. Blood samples were collected, and the DNA salting-out method was used for DNA extraction from peripheral venous blood. Genotyping of TAS2R16 (rs860170, rs978739, and rs1357949) was performed using real-time polymerase chain reaction (RT-PCR), and serum level analysis was performed for both periodontitis-affected patients and reference group subjects. The analysis of TAS2R16 rs860170 (TT, CT, and CC) showed a statistically significant difference between generalized periodontitis and the reference group (41.8%, 58.2%, and 0% vs. 38.7%, 56.1%, and 5.2%, p < 0.001). TAS2R16 rs860170 (TT, CT, and CC) showed a statistically significant difference between males in generalized periodontitis and reference groups (38.4%, 61.6%, and 0% vs. 32.9%, 56.6%, and 10.5%, p = 0.002). Female-specific analysis showed that the TAS2R16 rs978739 C allele was more frequent in generalized periodontitis compared to the reference group (37.5% vs. 28.7%, p = 0.016). Subjects aged 70 years and older demonstrated a statistically significant difference in TAS2R16 rs860170 (TT, CT, and CC) between generalized periodontitis and the reference group (42.8%, 57.2%, and 0% vs. 38.6%, 53.8%, and 7.6%, p = 0.003). TAS2R16 serum levels were elevated in generalized periodontitis compared to the reference group (0.112 (0.06) ng/mL vs. 0.075 (0.03) ng/mL, p = 0.002). Females carrying the TAS2R16 rs978739 C allele were more prone to generalized periodontitis development. Associations were found between TAS2R16 rs860170 polymorphisms, elevated TAS2R16 serum levels, and generalized periodontitis development.

Cardiac human bitter taste receptors contain naturally occurring variants that alter function

Bitter taste receptors (T2R) are a subfamily of G protein-coupled receptors that enable humans to detect aversive and toxic substances. The ability to discern bitter compounds varies between individuals and is attributed mainly to naturally occurring T2R polymorphisms. T2Rs are also expressed in numerous non-gustatory tissues, including the heart, indicating potential contributions to cardiovascular physiology. In this study. T2Rs that have previously been identified in human cardiac tissues (T2Rs - 10, 14, 30, 31, 46 and 50) and their naturally occurring polymorphisms were functionally characterised. The ligand-dependent signaling responses of some T2R variants were completely abolished (T2R30 Leu252 and T2R46 Met228), whereas other receptor variants had moderate changes in their maximal response, but not potency, relative to wild type. Using a cAMP fluorescent biosensor, we reveal the productive coupling of T2R14, but not the T2R14 Phe201 variant, to endogenous Gαi. Modeling revealed that these variants resulted in altered interactions that generally affected ligand binding (T2R30 Leu252) or Gα protein interactions (T2R46 Met228 and T2R14 Phe201), rather than receptor structural stability. Interestingly, this study is the first to show a difference in signaling for T2R50 Tyr203 (rs1376251) which has been associated with cardiovascular disease. The observation of naturally occurring functional variation in the T2Rs with the greatest expression in the heart is important, as their discovery should prove useful in deciphering the role of T2Rs within the cardiovascular system.

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.

TAS2R38 polymorphisms, Helicobacter pylori infection and susceptibility to gastric cancer and premalignant gastric lesions

BACKGROUND

Gastric cancer is worldwide the fourth more common cancer type by incidence, and the third by mortality. We analyzed three missense variants of TAS2R38 gene: rs713598 (A49P), rs1726866 (V262A), and rs10246939 (I296V). These variants and their combination in haplotypes (proline, alanine and valine/tasters or alanine, valine and isoleucine/nontasters) and diplotypes are responsible for individual differences in bitter perception. The single-nucleotide polymorphisms and the related phenotypes are known to be associated with susceptibility to Gram-negative bacterial infections, such as Helicobacter pylori , and with risk of various cancer types. An association between intermediate tasters (as defined by TAS2R38 diplotypes) and increased risk of gastric cancer was reported in a Korean population.

METHODS

We analyzed 2616 individuals of Latin American origin, representing the whole spectrum of lesions from gastritis to gastric cancer.

RESULTS

Comparing cancer cases vs. noncancers we observed a decrease in risk associated with heterozygous carriers of rs10246939 ( P  = 0.006) and rs1726866 ( P  = 0.003) when compared with homozygotes of the more common allele. Also, the analysis of diplotypes/phenotypes reflected the same association, with super-tasters showing a borderline increased risk of developing gastric cancer compared to medium-tasters [odds ratio (OR) = 1.63; 95% confidence interval (CI), 1.04-2.56; P  = 0.033]. Also, nontasters showed an increased risk when compared to medium-tasters although not reaching statistical significance (OR = 1.58; 95% CI, 0.80-2.87; P  = 0.203). We also tested the interactions between the TAS2R38 genotypes and H. pylori cagA status in a subset of samples and found no interaction.

CONCLUSION

In conclusion, our results suggest only a modest contribution of TAS2R38 gene genetic variability in gastric cancer etiology.

Demographic history was a formative mechanism of the genetic structure for the taste receptor TAS2R16 in human populations inhabiting Africa's Sahel/Savannah Belt

OBJECTIVES

Mode of subsistence is an important factor influencing dietary habits and the genetic structure of various populations through differential intensity of gene flow and selection pressures. Previous studies suggest that in Africa Taste 2 Receptor Member 16 (TAS2R16), which encodes the 7-transmembrane receptor protein for bitterness, might also be under positive selection pressure.

METHODS

However, since sampling coverage of populations was limited, we created a new TAS2R16 population dataset from across the African Sahel/Savannah belt representing various local populations of differing subsistence modes, linguistic affiliations, and geographic provenience. We sequenced the TAS2R16 exon gene and analyzed 2250 haplotypes among 19 populations.

RESULTS

We found no evidence for selection as a driving force of genetic variation at this locus; instead, we discovered a highly significant correlation between TAS2R16 genetic and geographical distances based on provenience of the sampled populations, strongly suggesting that genetic drift most likely prevailed over positive selection at this specific locus. We also found significant correlations with other independent loci, mainly in sedentary farmers.

DISCUSSION

Our results do not support the notion that the genetic diversity of TAS2R16 in Sahelian populations was shaped by selective pressures. This could result from several alternative and not mutually exclusive mechanisms, of which the possibility that, due to the pleiotropic nature of TAS2R16, selective pressures on other traits could counterbalance those acting on bitter taste perception, or that the change of diet in the Neolithic generally relaxed selective pressure on this gene.

Bitter taste receptors protect against skin aging by inhibiting cellular senescence and enhancing wound healing

BACKGROUND/OBJECTIVES

Bitter taste receptors are taste signaling pathway mediators, and are also expressed and function in extra-gustatory organs. Skin aging affects the quality of life and may lead to medical issues. The purpose of this study was to better understand the anti-skin aging effects of bitter taste receptors in D-galactose (D-gal)-induced aged human keratinocytes, HaCaT cells.

MATERIALS/METHODS

Expressions of bitter taste receptors in HaCaT cells and mouse skin tissues were examined by polymerase chain reaction assay. Bitter taste receptor was overexpressed in HaCaT cells, and D-gal was treated to induce aging. We examined the effects of bitter taste receptors on aging by using β-galactosidase assay, wound healing assay, and Western blot assay.

RESULTS

TAS2R16 and TAS2R10 were expressed in HaCaT cells and were upregulated by D-gal treatment. TAS2R16 exerted protective effects against skin aging by regulating p53 and p21, antioxidant enzymes, the SIRT1/mechanistic target of rapamycin pathway, cell migration, and epithelial-mesenchymal transition markers. TAS2R10 was further examined to confirm a role of TAS2R16 in cellular senescence and wound healing in D-gal-induced aged HaCaT cells.

CONCLUSIONS

Our results suggest a novel potential preventive role of these receptors on skin aging by regulating cellular senescence and wound healing in human keratinocyte, HaCaT.

G protein-coupled receptors that influence lifespan of human and animal models

Humanity has always sought to live longer and for this, multiple strategies have been tried with varying results. In this sense, G protein-coupled receptors (GPCRs) may be a good option to try to prolong our life while maintaining good health since they have a substantial participation in a wide variety of processes of human pathophysiology and are one of the main therapeutic targets. In this way, we present the analysis of a series of GPCRs whose activity has been shown to affect the lifespan of animal and human models, and in which we put a special interest in describing the molecular mechanisms involved. Our compilation of data revealed that the mechanisms most involved in the role of GPCRs in lifespan are those that mimic dietary restriction, those related to insulin signaling and the AMPK and TOR pathways, and those that alter oxidative homeostasis and severe and/or chronic inflammation. We also discuss the possibility of using agonist or antagonist drugs, depending on the beneficial or harmful effects of each GPCR, in order to prolong people's lifespan and healthspan.

Pharmacological significance of extra-oral taste receptors

It has recently been shown that taste receptors, in addition to being present in the oral cavity, exist in various extra-oral organs and tissues such as the thyroid, lungs, skin, stomach, intestines, and pancreas. Although their physiological function is not yet fully understood, it appears that they can help regulate the body's homeostasis and provide an additional defense function against pathogens. Since the vast majority of drugs are bitter, the greatest pharmacological interest is in the bitter taste receptors. In this review, we describe how bitter taste 2 receptors (TAS2Rs) induce bronchodilation and mucociliary clearance in the airways, muscle relaxation in various tissues, inhibition of thyroid stimulating hormone (TSH) in thyrocytes, and release of glucagon-like peptide-1 (GLP-1) and ghrelin in the digestive system. In fact, substances such as dextromethorphan, chloroquine, methimazole and probably glimepiride, being agonists of TAS2Rs, lead to these effects. TAS2Rs and taste 1 receptors (TAS1R2/3) are G protein-coupled receptors (GPCR). TAS1R2/3 are responsible for sweet taste perception and may induce GLP-1 release and insulin secretion. Umami taste receptors, belonging to the same superfamily of receptors, perform a similar function with regard to insulin. The sour and salty taste receptors work in a similar way, both being channel receptors sensitive to amiloride. Finally, gene-protein coupled receptor 40 (GPR40) and GPR120 for fatty taste perception are also protein-coupled receptors and may induce GLP-1 secretion and insulin release, similar to those of other receptors belonging to the same superfamily.

An update on extra-oral bitter taste receptors

Bitter taste-sensing type 2 receptors (TAS2Rs or T2Rs), belonging to the subgroup of family A G-protein coupled receptors (GPCRs), are of crucial importance in the perception of bitterness. Although in the first instance, TAS2Rs were considered to be exclusively distributed in the apical microvilli of taste bud cells, numerous studies have detected these sensory receptor proteins in several extra-oral tissues, such as in pancreatic or ovarian tissues, as well as in their corresponding malignancies. Critical points of extra-oral TAS2Rs biology, such as their structure, roles, signaling transduction pathways, extensive mutational polymorphism, and molecular evolution, have been currently broadly studied. The TAS2R cascade, for instance, has been recently considered to be a pivotal modulator of a number of (patho)physiological processes, including adipogenesis or carcinogenesis. The latest advances in taste receptor biology further raise the possibility of utilizing TAS2Rs as a therapeutic target or as an informative index to predict treatment responses in various disorders. Thus, the focus of this review is to provide an update on the expression and molecular basis of TAS2Rs functions in distinct extra-oral tissues in health and disease. We shall also discuss the therapeutic potential of novel TAS2Rs targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles.

Taste receptor polymorphisms and longevity: a systematic review and meta-analysis

Bitter taste receptors (TAS2R) are involved in a variety of non-tasting physiological processes, including immune-inflammatory ones. Therefore, their genetic variations might influence various traits. In particular, in different populations of South Italy (Calabria, Cilento, and Sardinia), polymorphisms of TAS2R16 and TAS238 have been analysed in association with longevity with inconsistent results. A meta-analytic approach to quantitatively synthesize the possible effect of the previous variants and, possibly, to reconcile the inconsistencies has been used in the present paper. TAS2R38 variants in the Cilento population were also analysed for their possible association with longevity and the obtained data have been included in the relative meta-analysis. In population from Cilento no association was found between TAS2R38 and longevity, and no association was observed as well, performing the meta-analysis with data of the other studies. Concerning TAS2R16 gene, instead, the genotype associated with longevity in the Calabria population maintained its significance in the meta-analysis with data from Cilento population, that, alone, were not significant in the previously published study. In conclusion, our results suggest that TAS2R16 genotype variant is associated with longevity in South Italy.

Associations between chronic cigarette smoking and taste function: Results from the 2013-2014 national health and nutrition examination survey

We identified associations between cigarette-smoking and taste function in the U.S. NHANES 2013-2014. Adults ≥ 40 years (n = 2849, nearly half former or current smokers) rated whole-mouth and tongue-tip bitter (1 mM quinine) and salt (1 M NaCl, 0.32 M NaCl) intensities and reported smoking history (pack years, PY), dependence (time to first cigarette, TTFC) and menthol/non-menthol use. Perceived intensity on the tongue-tip averaged just below moderate for quinine and moderate to strong for 1 M NaCl. Current chronic smokers (≥ 20 PY) reported lower bitter and salty intensities on the tongue-tip (β: -2.0, 95% CI: -3.7 to -0.4 and β: -3.6, 95% CI: -6.9 to -0.3, respectively) than never smokers. Similarly, compared to never smokers, dependent current smokers (TTFC ≤ 30 min) and dependent chronic smokers (≥ 20 PY, TTFC ≤ 30 min) rated less bitter (β: -2.0, 95% CI: -4.0 to 0.1 and β: -2.9, 95% CI: -4.5 to -1.3, respectively) and salty (β: -5.3, 95% CI: -9.3 to -1.4 and β: -4.7, 95% CI: -8.6 to -0.7, respectively) intensities on the tongue-tip. Depressed tongue-tip intensity in dependent smokers (with/without chronicity) versus never smokers was significant in younger (40-65 years), but not older (> 65 years) adults. Former smokers, non-chronic/less dependent smokers, and menthol smokers were more likely to report elevated whole-mouth quinine and 1 M NaCl intensities. Tongue-tip and whole-mouth taste intensity concordance varied between smokers and never smokers-current dependent smokers were more likely to rate tongue-tip quinine and NaCl lower than their respective whole-mouth tastants (OR: 1.8, 95% CI: 1.0 to 3.1 and OR: 1.8, 95% CI: 1.1 to 2.8, respectively). In summary, these U.S. nationally-representative data show that current smoking with chronicity and/or dependence associates with lower tongue-tip intensity for bitter and salty stimuli. Smokers with greater exposure to nicotine and/or dependence showed greater risk of taste alterations, with implications for diet- and smoking-related health outcomes.

Polymorphic variants in Sweet and Umami taste receptor genes and birthweight

The first thousand days of life from conception have a significant impact on the health status with short, and long-term effects. Among several anthropometric and maternal lifestyle parameters birth weight plays a crucial role on the growth and neurological development of infants. Recent genome wide association studies (GWAS) have demonstrated a robust foetal and maternal genetic background of birth weight, however only a small proportion of the genetic hereditability has been already identified. Considering the extensive number of phenotypes on which they are involved, we focused on identifying the possible effect of genetic variants belonging to taste receptor genes and birthweight. In the human genome there are two taste receptors family the bitter receptors (TAS2Rs) and the sweet and umami receptors (TAS1Rs). In particular sweet perception is due to a heterodimeric receptor encoded by the TAS1R2 and the TAS1R3 gene, while the umami taste receptor is encoded by the TAS1R1 and the TAS1R3 genes. We observed that carriers of the T allele of the TAS1R1-rs4908932 SNPs showed an increase in birthweight compared to GG homozygotes Coeff: 87.40 (35.13-139.68) p-value = 0.001. The association remained significant after correction for multiple testing. TAS1R1-rs4908932 is a potentially functional SNP and is in linkage disequilibrium with another polymorphism that has been associated with BMI in adults showing the importance of this variant from the early stages of conception through all the adult life.

Ecological Sensing Through Taste and Chemosensation Mediates Inflammation: A Biological Anthropological Approach

Ecological sensing and inflammation have evolved to ensure optima between organism survival and reproductive success in different and changing environments. At the molecular level, ecological sensing consists of many types of receptors located in different tissues that orchestrate integrated responses (immune, neuroendocrine systems) to external and internal stimuli. This review describes emerging data on taste and chemosensory receptors, proposing them as broad ecological sensors and providing evidence that taste perception is shaped not only according to sense epitopes from nutrients but also in response to highly diverse external and internal stimuli. We apply a biological anthropological approach to examine how ecological sensing has been shaped by these stimuli through human evolution for complex interkingdom communication between a host and pathological and symbiotic bacteria, focusing on population-specific genetic diversity. We then focus on how these sensory receptors play a major role in inflammatory processes that form the basis of many modern common metabolic diseases such as obesity, type 2 diabetes, and aging. The impacts of human niche construction and cultural evolution in shaping environments are described with emphasis on consequent biological responsiveness.

Clinical Role of Extraoral Bitter Taste Receptors

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

A Bitter Taste in Your Heart

The human genome contains ∼29 bitter taste receptors (T2Rs), which are responsible for detecting thousands of bitter ligands, including toxic and aversive compounds. This sentinel function varies between individuals and is underpinned by naturally occurring T2R polymorphisms, which have also been associated with disease. Recent studies have reported the expression of T2Rs and their downstream signaling components within non-gustatory tissues, including the heart. Though the precise role of T2Rs in the heart remains unclear, evidence points toward a role in cardiac contractility and overall vascular tone. In this review, we summarize the extra-oral expression of T2Rs, focusing on evidence for expression in heart; we speculate on the range of potential ligands that may activate them; we define the possible signaling pathways they activate; and we argue that their discovery in heart predicts an, as yet, unappreciated cardiac physiology.

TAS2R38 bitter taste receptor and attainment of exceptional longevity

Bitter taste receptors play crucial roles in detecting bitter compounds not only in the oral cavity, but also in extraoral tissues where they are involved in a variety of non‒tasting physiological processes. On the other hand, disorders or modifications in the sensitivity or expression of these extraoral receptors can affect physiological functions. Here we evaluated the role of the bitter receptor TAS2R38 in attainment of longevity, since it has been widely associated with individual differences in taste perception, food preferences, diet, nutrition, immune responses and pathophysiological mechanisms. Differences in genotype distribution and haplotype frequency at the TAS2R38 gene between a cohort of centenarian and near-centenarian subjects and two control cohorts were determined. Results show in the centenarian cohort an increased frequency of subjects carrying the homozygous genotype for the functional variant of TAS2R38 (PAV/PAV) and a decreased frequency of those having homozygous genotype for the non-functional form (AVI/AVI), as compared to those determined in the two control cohorts. In conclusion, our data providing evidence of an association between genetic variants of TAS2R38 gene and human longevity, suggest that TAS2R38 bitter receptor can be involved in the molecular physiological mechanisms implied in the biological process of aging.

Dual binding mode of "bitter sugars" to their human bitter taste receptor target

The 25 human bitter taste receptors (hTAS2Rs) are responsible for detecting bitter molecules present in food, and they also play several physiological and pathological roles in extraoral compartments. Therefore, understanding their ligand specificity is important both for food research and for pharmacological applications. Here we provide a molecular insight into the exquisite molecular recognition of bitter β-glycopyranosides by one of the members of this receptor subclass, hTAS2R16. Most of its agonists have in common the presence of a β-glycopyranose unit along with an extremely structurally diverse aglycon moiety. This poses the question of how hTAS2R16 can recognize such a large number of "bitter sugars". By means of hybrid molecular mechanics/coarse grained molecular dynamics simulations, here we show that the three hTAS2R16 agonists salicin, arbutin and phenyl-β-D-glucopyranoside interact with the receptor through a previously unrecognized dual binding mode. Such mechanism may offer a seamless way to fit different aglycons inside the binding cavity, while maintaining the sugar bound, similar to the strategy used by several carbohydrate-binding lectins. Our prediction is validated a posteriori by comparison with mutagenesis data and also rationalizes a wealth of structure-activity relationship data. Therefore, our findings not only provide a deeper molecular characterization of the binding determinants for the three ligands studied here, but also give insights applicable to other hTAS2R16 agonists. Together with our results for other hTAS2Rs, this study paves the way to improve our overall understanding of the structural determinants of ligand specificity in bitter taste receptors.

Taste receptors, innate immunity and longevity: the case of TAS2R16 gene

Background

Innate immunity utilizes components of sensory signal transduction such as bitter and sweet taste receptors. In fact, empirical evidence has shown bitter and sweet taste receptors to be an integral component of antimicrobial immune response in upper respiratory tract infections. Since an efficient immune response plays a key role in the attainment of longevity, it is not surprising that the rs978739 polymorphism of the bitter taste receptor TAS2R16 gene has been shown to be associated with longevity in a population of 941 individuals ranging in age from 20 to 106 years from Calabria (Italy). There are many possible candidate genes for human longevity, however of the many genes tested, only APOE and FOXO3 survived to association in replication studies. So, it is necessary to validate in other studies genes proposed to be associated with longevity. Thus, we analysed the association of the quoted polymorphism in a population of long lived individuals (LLIs) and controls from another Italian population from Cilento.

Methods

The analysis has been performed on data previously obtained with genome-wide association study on a population of LLIs (age range 90–109 years) and young controls (age range 18–45 years) from Cilento (Italy).

Results

Statistical power calculations showed that the analysed cohort represented by 410 LLIs and 553 young controls was sufficiently powered to replicate the association between rs978739 and the longevity phenotype according to the effect size and frequencies described in the previous paper, under a dominant and additive genetic model. However, no evidence of association between rs978739 and the longevity phenotype was observed according to the additive or dominant model.

Conclusion

There are several reasons for the failure of the confirmation of a previous study. However, the differences between the two studies in terms of environment of the population adopted and of the criteria of inclusion have made difficult the replication of the findings.

Exceptional Human Longevity

Exceptional longevity represents an extreme phenotype. Current centenarians are survivors of a cohort who display delayed onset of age-related diseases and/or resistance to otherwise lethal illnesses occurring earlier in life. Characteristics of aging are heterogeneous, even among long-lived individuals. Associations between specific clinical or genetic biomarkers exist, but there is unlikely to be a single biomarker predictive of long life. Careful observations in the oldest old offer some empirical strategies that favor increased health span and life span, with implications for compression of disability, identification and implementation of lifestyle behaviors that promote independence, identification and measurement of more reliable markers associated with longevity, better guidance for appropriate health screenings, and promotion of anticipatory health discussions in the setting of more accurate prognostication. Comprehensive PubMed literature searches were performed, with an unbiased focus on mechanisms of longevity. Overall, the aggregate literature supports that the basis for exceptional longevity is multifactorial and involves disparate combinations of genes, environment, resiliency, and chance, all of which are influenced by culture and geography.

Interactions between Bitter Taste, Diet and Dysbiosis: Consequences for Appetite and Obesity

The type 2 family of taste receptors (T2Rs) detect and respond to bitter tastants. These receptors are expressed throughout the gastrointestinal (GI) tract, with location dependant roles. In the oral cavity, T2Rs are involved in the conscious perception of bitter tastants, while in the lower GI tract they have roles in chemoreception and regulation of GI function. Through these diverse roles, these receptors may be involved in modulating appetite and diet, with consequences for weight regulation and obesity. Interestingly, the concentration of T2Rs in the GI tract is greatest in the large intestine, the organ with the densest colonisation of bacteria. The gut microbiome has been the subject of intense research, as a plethora of roles linking microbiota to human health continue to be uncovered. Of particular interest is the microbial signature associated with obesity. Obesity is a leading health concern, and advances in our understanding of this disease are needed. Diet is a known modifiable factor in the development of obesity. However, diet only partially explains disease risk. Changes in microbial energy harvesting by the microbiota plays a role in obesity, and the composition of these energy harvesting populations may be controlled by taste receptors. This review explores T2Rs as a potential link between obesity and the human GI microbiome.

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.

Genes from the TAS1R and TAS2R Families of Taste Receptors: Looking for Signatures of Their Adaptive Role in Human Evolution

Taste perception is crucial in monitoring food intake and, hence, is thought to play a significant role in human evolution. To gain insights into possible adaptive signatures in genes encoding bitter, sweet, and umami taste receptors, we surveyed the available sequence variation data from the 1000 Genomes Project Phase 3 for TAS1R (TAS1R1-3) and TAS2R (TAS2R16 and TAS2R38) families. Our study demonstrated that genes from these two families have experienced contrasting evolutionary histories: While TAS1R1 and TAS1R3 showed worldwide evidence of positive selection, probably correlated with improved umami and sweet perception, the patterns of variation displayed by TAS2R16 and TAS2R38 were more consistent with scenarios of balancing selection that possibly conferred a heterozygous advantage associated with better capacity to perceive a wide range of bitter compounds. In TAS2R16, such adaptive events appear to have occurred restrictively in mainland Africa, whereas the strongest evidence in TAS2R38 was detected in Europe. Despite plausible associations between taste perception and the TAS1R and TAS2R selective signatures, we cannot discount other biological mechanisms as driving the evolutionary trajectories of those TAS1R and TAS2R members, especially given recent findings of taste receptors behaving as the products of pleiotropic genes involved in many functions outside the gustatory system.

Association between taste receptor (TAS) genes and the perception of wine characteristics

Several studies have suggested a possible relationship between polymorphic variants of the taste receptors genes and the acceptance, liking and intake of food and beverages. In the last decade investigators have attempted to link the individual ability to taste 6-n-propylthiouracil (PROP) and the sensations, such as astringency and bitterness, elicited by wine or its components, but with contradictory results. We have used the genotype instead of the phenotype (responsiveness to PROP or other tastants), to test the possible relation between genetic variability and the perception of wine characteristic in 528 subjects from Italy and the Czech Republic. We observed several interesting associations, among which the association between several TAS2R38 gene single nucleotide polymorphisms (P = 0.002) and the TAS2R16-rs6466849 polymorphism with wine sourness P = 0.0003). These associations were consistent in both populations, even though the country of origin was an important factor in the two models, thus indicating therefore that genetics alongside cultural factors also play a significant role in the individual liking of wine.

The Bitter Taste Receptor TAS2R16 Achieves High Specificity and Accommodates Diverse Glycoside Ligands by using a Two-faced Binding Pocket

Although bitter taste receptors (TAS2Rs) are important for human health, little is known of the determinants of ligand specificity. TAS2Rs such as TAS2R16 help define gustatory perception and dietary preferences that ultimately influence human health and disease. Each TAS2R must accommodate a broad diversity of chemical structures while simultaneously achieving high specificity so that diverse bitter toxins can be detected without all foods tasting bitter. However, how these G protein-coupled receptors achieve this balance is poorly understood. Here we used a comprehensive mutation library of human TAS2R16 to map its interactions with existing and novel agonists. We identified 13 TAS2R16 residues that contribute to ligand specificity and 38 residues whose mutation eliminated signal transduction by all ligands, providing a comprehensive assessment of how this GPCR binds and signals. Our data suggest a model in which hydrophobic residues on TM3 and TM7 form a broad ligand-binding pocket that can accommodate the diverse structural features of β-glycoside ligands while still achieving high specificity.

Genetic diversity of bitter taste receptor gene family in Sichuan domestic and Tibetan chicken populations

The sense of bitter taste plays a critical role in animals as it can help them to avoid intake of toxic and harmful substances. Previous research had revealed that chicken has only three bitter taste receptor genes (Tas2r1, Tas2r2 and Tas2r7). To better understand the genetic polymorphisms and importance of bitter taste receptor genes (Tas2rs) in chicken, here, we sequenced Tas2rs of 30 Sichuan domestic chickens and 30 Tibetan chickens. Thirteen single-nucleotide polymorphisms (SNPs) including three nonsynonymous mutations (m.359G>C, m.503C>A and m.583A>G) were detected in Tas2r1 (m. is the abbreviation for mutation); three SNPs were detected in Tas2r2, but none of them were missense mutation; eight SNPs were detected in Tas2r7 including six nonsynonymous substitutions (m.178G>A, m.421A>C, m.787C>T, m.832G>T, m.907A>T and m.943G>A). Tajima's D neutral test indicates that there is no population expansion in both populations, and the size of the population is relatively stable. All the three networks indicate that red jungle fowls share haplotypes with domestic chickens. In addition, we found that haplotypes H1 and HE1 were positively associated with high-altitude adaptation, whereas haplotypes H4 and HE4 showed a negative correlation with high-altitude adaptation in Tas2rs. Although, chicken has only three Tas2rs, our results showed that both Sichuan domestic chickens and Tibetan chickens have abundant haplotypes in Tas2rs, especially in Tas2r7, which might help chickens to recognize a wide variety of bitter-tasting compounds.

Extraoral bitter taste receptors in health and disease

Bitter taste receptors (TAS2Rs or T2Rs) belong to the superfamily of seven-transmembrane G protein-coupled receptors, which are the targets of >50% of drugs currently on the market. Canonically, T2Rs are located in taste buds of the tongue, where they initiate bitter taste perception. However, accumulating evidence indicates that T2Rs are widely expressed throughout the body and mediate diverse nontasting roles through various specialized mechanisms. It has also become apparent that T2Rs and their polymorphisms are associated with human disorders. In this review, we summarize the physiological and pathophysiological roles that extraoral T2Rs play in processes as diverse as innate immunity and reproduction, and the major challenges in this emerging field.

Gut Microbiota and a Selectively Bred Taste Phenotype: A Novel Model of Microbiome-Behavior Relationships

OBJECTIVES

The microbiota-gut-brain axis is increasingly implicated in obesity, anxiety, stress, and other health-related processes. Researchers have proposed that gut microbiota may influence dietary habits, and pathways through the microbiota-gut-brain axis make such a relationship feasible; however, few data bear on the hypothesis. As a first step in the development of a model system, the gut microbiome was examined in rat lines selectively outbred on a taste phenotype with biobehavioral profiles that have diverged with respect to energy regulation, anxiety, and stress.

METHODS

Occidental low and high-saccharin-consuming rats were assessed for body mass and chow, water, and saccharin intake; littermate controls had shared cages with rats in the experimental group but were not assessed. Cecum and colon microbial communities were profiled using Illumina 16S rRNA sequencing and multivariate analysis of microbial diversity and composition.

RESULTS

The saccharin phenotype was confirmed (low-saccharin-consuming rats, 0.7Δ% [0.9Δ%]; high-saccharin-consuming rats, 28.1Δ% [3.6Δ%]). Regardless of saccharin exposure, gut microbiota differed between lines in terms of overall community similarity and taxa at lower phylogenetic levels. Specifically, 16 genera in three phyla distinguished the lines at a 10% false discovery rate.

DISCUSSION

The study demonstrates for the first time that rodent lines created through selective pressure on taste and differing on functionally related correlates host different microbial communities. Whether the microbiota are causally related to the taste phenotype or its correlates remains to be determined. These findings encourage further inquiry on the relationship of the microbiome to taste, dietary habits, emotion, and health.

Bitter taste receptors: Extraoral roles in pathophysiology

Over the past decade tremendous progress has been made in understanding the functional role of bitter taste receptors (T2Rs) and bitter taste perception. This review will cover the recent advances made in identifying the role of T2Rs in pathophysiological states. T2Rs are widely expressed in various parts of human anatomy and have been shown to be involved in physiology of respiratory system, gastrointestinal tract and endocrine system. Empirical evidence has shown T2Rs to be an integral component of antimicrobial immune responses in upper respiratory tract infections. The studies on human airway smooth muscle cells have shown that a potent bitter tastant induced bronchodilatory effects mediated by bitter taste receptors. Clinical data suggests a role for T2R38 polymorphism in predisposition of individuals to chronic rhinosinusitis. The role of genetic variation in T2Rs and its impact on disease susceptibility have been investigated in various other disease risk factors such as alcohol dependence, head and neck cancers. Preliminary reports have demonstrated differential expression of functional T2Rs in breast cancer cell lines. Studies on the role of T2Rs in pathophysiology of diseases including chronic rhinosinusitis, asthma, cystic fibrosis, and cancer have been promising. However, research in this field is in its nascent stages, and more confirmatory studies on animal models and in clinical settings are required.

Receptor Polymorphism and Genomic Structure Interact to Shape Bitter Taste Perception

The ability to taste bitterness evolved to safeguard most animals, including humans, against potentially toxic substances, thereby leading to food rejection. Nonetheless, bitter perception is subject to individual variations due to the presence of genetic functional polymorphisms in bitter taste receptor (TAS2R) genes, such as the long-known association between genetic polymorphisms in TAS2R38 and bitter taste perception of phenylthiocarbamide. Yet, due to overlaps in specificities across receptors, such associations with a single TAS2R locus are uncommon. Therefore, to investigate more complex associations, we examined taste responses to six structurally diverse compounds (absinthin, amarogentin, cascarillin, grosheimin, quassin, and quinine) in a sample of the Caucasian population. By sequencing all bitter receptor loci, inferring long-range haplotypes, mapping their effects on phenotype variation, and characterizing functionally causal allelic variants, we deciphered at the molecular level how a subjects’ genotype for the whole-family of TAS2R genes shapes variation in bitter taste perception. Within each haplotype block implicated in phenotypic variation, we provided evidence for at least one locus harboring functional polymorphic alleles, e.g. one locus for sensitivity to amarogentin, one of the most bitter natural compounds known, and two loci for sensitivity to grosheimin, one of the bitter compounds of artichoke. Our analyses revealed also, besides simple associations, complex associations of bitterness sensitivity across TAS2R loci. Indeed, even if several putative loci harbored both high- and low-sensitivity alleles, phenotypic variation depended on linkage between these alleles. When sensitive alleles for bitter compounds were maintained in the same linkage phase, genetically driven perceptual differences were obvious, e.g. for grosheimin. On the contrary, when sensitive alleles were in opposite phase, only weak genotype-phenotype associations were seen, e.g. for absinthin, the bitter principle of the beverage absinth. These findings illustrate the extent to which genetic influences on taste are complex, yet arise from both receptor activation patterns and linkage structure among receptor genes.

Human bitter taste is believed to protect us from the ingestion of poisonous substances, thereby shaping food rejections. Bitter perception differs, however, across individuals, due to genetic variations in the ~25 bitter taste receptor (TAS2R) genes. A famous example known since the 1930s is the inherited bitter taste sensitivity to phenylthiocarbamide, which is associated with genetic polymorphisms in a single TAS2R gene. Yet, such simple receptor-substance associations do not reflect the full complexity of bitter perception, since individual bitter substances frequently activate several TAS2Rs. Here, we provide an in-depth analysis of the genetic variability influencing human bitter taste. While each study subject carried a different set of genetic polymorphisms, we found that most variations reside in just six blocks, each harboring only one to five haplotypes. Thus, besides simple associations between taste and TAS2R gene polymorphisms, we revealed complex associations dependent on linkage between several high- and low-sensitivity alleles. Indeed, subjects carried either sensitive or insensitive alleles for receptors sensitive to grosheimin, a bitter compound in artichoke, or at least one sensitive allele for receptors specific for absinthin, the bitter principle of absinth. In short, simple associations and complex genomic linkage determine sensitivity to selected dietary bitter compounds.

TAS2R bitter taste receptors regulate thyroid function

Dysregulation of thyroid hormones triiodothyronine and thyroxine (T3/T4) can impact metabolism, body composition, and development. Thus, it is critical to identify novel mechanisms that impact T3/T4 production. We found that type 2 taste receptors (TAS2Rs), which are activated by bitter-tasting compounds such as those found in many foods and pharmaceuticals, negatively regulate thyroid-stimulating hormone (TSH)-dependent Ca(2+) increases and TSH-dependent iodide efflux in thyrocytes. Immunohistochemical Tas2r-dependent reporter expression and real-time PCR analyses reveal that human and mouse thyrocytes and the Nthy-Ori 3-1 human thyrocyte line express several TAS2Rs. Five different agonists for thyrocyte-expressed TAS2Rs reduced TSH-dependent Ca(2+) release in Nthy-Ori 3-1 cells, but not basal Ca(2+) levels, in a dose-dependent manner. Ca(2+) responses were unaffected by 6-n-propylthiouracil, consistent with the expression of an unresponsive variant of its cognate receptor, TAS2R38, in these cells. TAS2R agonists also inhibited basal and TSH-dependent iodide efflux. Furthermore, a common TAS2R42 polymorphism is associated with increased serum T4 levels in a human cohort. Our findings indicate that TAS2Rs couple the detection of bitter-tasting compounds to changes in thyrocyte function and T3/T4 production. Thus, TAS2Rs may mediate a protective response to overingestion of toxic materials and could serve as new druggable targets for therapeutic treatment of hypo- or hyperthyroidism.

Origin and differential selection of allelic variation at TAS2R16 associated with salicin bitter taste sensitivity in Africa

Bitter taste perception influences human nutrition and health, and the genetic variation underlying this trait may play a role in disease susceptibility. To better understand the genetic architecture and patterns of phenotypic variability of bitter taste perception, we sequenced a 996 bp region, encompassing the coding exon of TAS2R16, a bitter taste receptor gene, in 595 individuals from 74 African populations and in 94 non-Africans from 11 populations. We also performed genotype-phenotype association analyses of threshold levels of sensitivity to salicin, a bitter anti-inflammatory compound, in 296 individuals from Central and East Africa. In addition, we characterized TAS2R16 mutants in vitro to investigate the effects of polymorphic loci identified at this locus on receptor function. Here, we report striking signatures of positive selection, including significant Fay and Wu's H statistics predominantly in East Africa, indicating strong local adaptation and greater genetic structure among African populations than expected under neutrality. Furthermore, we observed a "star-like" phylogeny for haplotypes with the derived allele at polymorphic site 516 associated with increased bitter taste perception that is consistent with a model of selection for "high-sensitivity" variation. In contrast, haplotypes carrying the "low-sensitivity" ancestral allele at site 516 showed evidence of strong purifying selection. We also demonstrated, for the first time, the functional effect of nonsynonymous variation at site 516 on salicin phenotypic variance in vivo in diverse Africans and showed that most other nonsynonymous substitutions have weak or no effect on cell surface expression in vitro, suggesting that one main polymorphism at TAS2R16 influences salicin recognition. Additionally, we detected geographic differences in levels of bitter taste perception in Africa not previously reported and infer an East African origin for high salicin sensitivity in human populations.

PTC bitter taste genetic polymorphism, food choices, physical growth in body height and body fat related traits among adolescent girls from Kangra Valley, Himachal Pradesh (India)

BACKGROUND

Bitter sensitivity among individuals and ethnic groups is partly due to polymorphic bitter taste receptor genes (TAS2Rs). PTC/PROP bitter taste responsiveness at locus TAS2R38 is a well-established index of individual variation in oral sensation that has been linked with predicting food liking and consumption. Previous studies suggest that the relationship between PTC/PROP and anthropometric traits remains controversial.

OBJECTIVES

To explore the role of TAS2R38 locus in taste choices, adolescent growth trend for body height, weight and fat patterning among girls and to evaluate their growth status.

MATERIALS AND METHODS

Cross-sectional data on 210 girls ranging in age from 11-18 years were collected from Palampur in the Kangra valley of Himachal Pradesh.

RESULTS

The proportion of PTC non-tasters was 19.52%. PTC tasters and non-tasters had some differences in their food choices and preferences. More sensitive PTC tasters had a low preference for raw cruciferous vegetables and bitter tasting foods (like bitter gourd) and beverages, while they had higher preference for sweet-tasting foods (p < 0.05). PTC tasters overtook their PTC non-taster counterparts from age 14 through 16 years in having higher mean average skinfold, percentage body fat, fat mass index and fat-free mass index. PTC non-tasters had higher mean stature than tasters through all age groups. PTC tasters had slightly higher mean body weight than tasters at age 11, but in later years the advantage was lost; the total gain among non-tasters through adolescence was higher (78.20%) than tasters (66.92%). PTC thresholds significantly and negatively correlated with body height.

CONCLUSIONS

TAS2R38 locus seems to have a role in food tastes, choices and preferences. Perceived bitterness of PTC/PROP thresholds were significantly and negatively correlated with body height and fat-free mass. These results, thus, tentatively suggest that the PTC non-taster gene may help in better absorption of calcium than its counter taster allele. Studies on differences in calcium metabolism between PTC tasters and non-tasters are needed to confirm these indications across cultures.