Extraoral expression and characterization of bitter taste receptors in Astyanax mexicanus (Mexican tetra fish).

The chemical senses of olfaction and taste are well developed in fish and play a vital role in its various activities such as navigation, mate recognition, and food detection. The small teleost fish Astyanax mexicanus consists of interfertile river-dwelling and cave-dwelling populations, referred to as "surface fish" and "cavefish" respectively. An important anatomical feature of cavefish is the lack of eyes leading them to be referred to as blind fish and suggesting an enhanced functional role for other senses such as taste. In this study, we characterize the expression of bitter taste receptors (T2Rs or Tas2Rs) in A. mexicanus and investigate their functionality in a heterologous expression system. The genome database of A. mexicanus (ensemble and NCBI) showed 7 Tas2Rs, among these Tas2R1, Tas2R3, Tas2R4, and Tas2R114 are well characterized in humans and mice but not in A. mexicanus. Therefore, the 4 Tas2Rs were selected for further analysis and their expression in A. mexicanus was confirmed by in situ hybridization and RT-PCR in early developmental stages. These Tas2Rs are expressed in various oral and extraoral organs (liver, fins, jaws, and gills) in A. mexicanus, and Tas2R1 has maximum expression and is localized throughout the fish body. Using the heterologous expression of A. mexicanus T2Rs in HEK293T cells coupled with cell-based calcium mobilization assays, we show that A. mexicanus T2Rs are activated by commonly used fish food and known bitter agonists, including quinine. This study provides novel insights into the extraoral expression of T2Rs in A. mexicanus and suggests their importance in extraoral food detection.

Denatonium benzoate bitter taste perception in chronic rhinosinusitis subgroups.

BACKGROUND: Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP), and aspirin-exacerbated respiratory disease (AERD) have varying levels of inflammation and disease severity. Solitary chemosensory cells (SCCs) are enriched in nasal polyps, are the primary source of interleukin 25 (IL-25) in upper airways, leading to type 2 inflammation, and are activated by bitter-tasting denatonium benzoate (DB). Thus, we sought to evaluate DB taste perception at a range of concentrations in order to identify 1 that most differentiates CRS subgroups from controls. METHODS: CRSsNP (n = 25), CRSwNP (n = 26), and AERD (n = 27) patients as well as controls (n = 25) tasted 6 DB concentrations in a fixed, random order, rating on a category scale of 0 (no intensity) to 12 (extremely intense). Sinonasal epithelial cultures were treated with and without denatonium and analyzed for IL-25 via flow cytometry. RESULTS: CRSsNP patients rated DB as significantly less intense than did controls at all concentrations: 5.62 × 10-9 M, 1.00 × 10-8 M, 1.78 × 10-8 M, 3.16 × 10-8 M, 5.62 × 10-8 M, and 1.00 × 10-7 M (all p < 0.0083). CRSwNP patients did not show significant differences from controls. AERD patients rated DB as significantly more intense than did controls at concentrations of 1.00 × 10-8 M and 3.16 × 10-8 M (p < 0.0083). In vitro data demonstrated significant increase in IL-25-positive cells after denatonium stimulation (n = 5), compared to control (n = 5) (p = 0.012). CONCLUSION: Our findings link in vitro DB stimulation of sinonasal tissue with increased IL-25 and show differential DB taste perception in CRS subgroups relative to the control group, with CRSsNP being hyposensitive and AERD being hypersensitive. We propose a concentration of 3.16 × 10-8 M for future study of clinical utility.

Divergent bitter and sweet taste perception intensity in chronic rhinosinusitis patients.

BACKGROUND: Bitter and sweet taste receptors are present in the human upper airway, where they have roles in innate immunity. Previous studies have shown that 1 of the 25 bitter receptors, TAS2R38, responds to specific bacterial signaling molecules and evokes 1 type of a defense response in the upper airway, whereas ligands of sweet receptors suppress other types of defense responses. METHODS: We examined whether other bitter taste receptors might also be involved in innate immunity by using sensory responses to bitter compounds that are not ligands of TAS2R38 (quinine and denatonium benzoate) to assess the sensitivity of other bitter receptors in chronic rhinosinusitis (CRS) patients. CRS patients with (n = 426) and without (n = 226) nasal polyps and controls (n = 356) rated the intensity of quinine, denatonium benzoate, phenylthiocarbamide (PTC; a ligand for TAS2R38), sucrose, and salt. RESULTS: CRS patients rated the bitter compounds denatonium benzoate and quinine as less intense and sucrose as more intense than did controls (false discovery rate [FDR] <0.05) and CRS patients and controls did not differ in their ratings of salt (FDR >0.05). PTC bitter taste intensity differed between patient and control groups but were less marked than those previously reported. Though differences were statistically significant, overall effect sizes were small. CONCLUSION: CRS patients report bitter stimuli as less intense but sweet stimuli as more intense than do control subjects. We speculate that taste responses may reflect the competence of sinonasal innate immunity mediated by taste receptor function, and thus a taste test may have potential for clinical utility in CRS patients.

Sensitive period for the acceptance of unpalatable flavors in the presence of a preexposed odor in infant rats.

It has been shown that exposure to familiar odors facilitate the acceptance of bitter flavors in preweanling rats, yet it unknown how long this phenomenon persists. This study assessed, in 9- or 15-day-old Wistar rats, the influence of a familiar scent (i.e., lemon) on the intake of and behavioral responsiveness (i.e., mouthing, paw lick, chin rub, head shake, among other taste reactivity responses) elicited by a 0.1% quinine solution. The results showed heightened quinine intake in 9-day-old rats that had been preexposed to the odor, when compared to non-preexposed controls. This result was replicated in Experiment 2, which also documented no alterations in behavioral responsiveness toward quinine in the 9-day-old rats, as a function of the pre-exposure. More importantly, 15-day-old rats exhibited no alterations in intake or behavioral responsiveness toward quinine as a function of odor pre-exposure. These results suggest that the effects of odor pre-exposure upon acceptance of bitter tastes may occur within a sensitive period for the acceptance of bitter food.

Metal Ions Activate the Human Taste Receptor TAS2R7.

Divalent and trivalent salts exhibit a complex taste profile. They are perceived as being astringent/drying, sour, bitter, and metallic. We hypothesized that human bitter-taste receptors may mediate some taste attributes of these salts. Using a cell-based functional assay, we found that TAS2R7 responds to a broad range of divalent and trivalent salts, including zinc, calcium, magnesium, copper, manganese, and aluminum, but not to potassium, suggesting TAS2R7 may act as a metal cation receptor mediating bitterness of divalent and trivalent salts. Molecular modeling and mutagenesis analysis identified 2 residues, H943.37 and E2647.32, in TAS2R7 that appear to be responsible for the interaction of TAS2R7 with metallic ions. Taste receptors are found in both oral and extraoral tissues. The responsiveness of TAS2R7 to various mineral salts suggests it may act as a broad sensor, similar to the calcium-sensing receptor, for biologically relevant metal cations in both oral and extraoral tissues.

Time-intensity and reaction-time methodology applied to the dynamic perception and liking of bitterness in relation to body mass index.

There are very few studies which have considered perception temporality when relating perceived intensity and hedonic responses in relation to body mass index (BMI; kg/cm2). The aim of the present study was to determine the relationship between BMI with the dynamic perception and liking of bitter tasting solutions. For this purpose, two different categories of bitter products were applied: 6-n-propilthiouracil (PROP) solutions (0.010, 0.032 and 0.060 mmol/L) and commercial beverages (coffee, yerba mate infusion and grapefruit juice). The proposed methodology to evaluate perception and hedonic response was based on the measurement of reaction-time (R-T) and multiple-sip time-intensity (T-I) registers in people with a high BMI (25 < BMI < 30; overweight group) and a normal BMI (<25; normal-weight control group). The multiple-sip evaluation to describe perception of PROP solutions and liking of beverages was used as a more ecologically valid laboratory methodology to simulate a situation of usual consumption. In this sense, working with a multiple-sip design helped confirm that bitter taste has a cumulative effect since in every case the sip effect was significant when evaluating the maximum intensity; this effect was more important as the bitterness increased. Regarding the body weight group comparisons, the normal BMI group perceived bitter taste more intensely and the time to react to it was shorter (faster reaction) for both PROP solutions and the three beverages. Interestingly, even though the high BMI group rated the bitter taste as less intense, they had a lower level of acceptance than normal BMI. This result suggests that the hedonic rather than the sensory component might be playing a crucial role in the perception of bitter taste in individuals with high BMI.

Influences of weight, age, gender, genetics, diseases, and ethnicity on bitterness perception: a narrative review of current methodological aspects

BACKGROUND: Bitterness perception seems to be related to an enhanced intake of dietary fat and to a tendency to the development of diseases such as obesity. However, the exact factors for this possible contribution still need to be better investigated. So, gustatory perception of the bitter taste is a promising area of study because of its importance regarding food choices and consequently feeding behavior. Therefore, this short review focused on recent papers reporting correlations between bitter taste, anthropometric variables, obesity and other chronic diseases, age, gender, ethnicity, and genetics. METHODS: A survey was performed in MEDLINE (PubMed) and Scielo from September 2015 to January 2017.Only review articles, observational studies and clinical trials published in English and Portuguese over the last15 years which met the objectives of the present study were considered. A total of 40 papers were evaluated. RESULTS: Two papers showed a positive correlation between bitter taste and obesity, one indicated that this correlation is influenced by the subject's age, one suggested a negative correlation, and two found no association. Age seems to be negatively correlated with the bitterness perceived, and female gender was associated with a stronger perception of bitterness. Genetics, mostly due to differences in TAS2R38 expression, influences sensitivity to the bitter taste, feeding behavior and also alcohol intake. Ethnicity, not only the subject's phenotypic or genotypic characteristics, seems to play a role in taste perception and nutritional diseases. CONCLUSIONS: Age, gender, genetics and ethnicity seem to play a role in bitterness perception. Data about associations between bitterness perception and anthropometrics are conflicting.

Docking and Molecular Dynamics of Steviol Glycoside-Human Bitter Receptor Interactions.

Stevia is one of the sweeteners with the greatest consumer demand because of its natural origin and minimal calorie content. Steviol glycosides (SG) are the main active compounds present in the leaves of Stevia rebaudiana and are responsible for its sweetness. However, recent in vitro studies in HEK 293 cells revealed that SG specifically activate the hT2R4 and hT2R14 bitter taste receptors, triggering this mouth feel. The objective of this study was to characterize the interaction of SG with these two receptors at the molecular level. The results showed that SG have only one site for orthosteric binding to these receptors. The binding free energy (ΔGbinding) between the receptor and SG was negatively correlated with SG bitterness intensity, for both hT2R4 (r = -0.95) and hT2R14 (r = -0.89). We also determined, by steered molecular dynamics simulations, that the force required to extract stevioside from the receptors was greater than that required for rebaudioside A, in accordance with the ΔG values obtained by molecular docking. Finally, we identified the loop responsible for the activation by SG of both receptors. As a whole, these results contribute to a better understanding of the resulting off-flavor perception of these natural sweeteners in foods and beverages, allowing for better prediction, and control, of the resulting bitterness.

Correlation of T2R38 taste phenotype and in vitro biofilm formation from nonpolypoid chronic rhinosinusitis patients.

BACKGROUND: Sinonasal biofilms have been demonstrated in specimens collected from chronic rhinosinusitis (CRS) patients. Mounting evidence suggests that biofilms contribute to therapeutically recalcitrant CRS. Recently, the bitter taste receptor T2R38 has been implicated in the regulation of the sinonasal mucosal innate immune response. TAS2R38 gene polymorphisms affect receptor functionality and contribute to variations seen in sinonasal innate defense as well as taste perception reflected in gustatory sensitivity to the bitter compound phenylthiocarbamide (PTC). In a population of CRS patients with active infection or inflammation, we sought to determine if a correlation between T2R38 phenotype and in vitro biofilm formation existed. METHODS: Endoscopically guided sinonasal swabs were obtained prospectively from CRS (±polyp) patients with evidence of persistent inflammation or mucopurulence. In vitro biofilm formation was assessed with a modified Calgary Biofilm Detection Assay. Patients' phenotypic (functional) expression of the bitter taste receptor T2R38 was evaluated with a taste test including the compound PTC. Linear regression was used to determine the level of significance between mean in vitro biofilm formation levels and mean PTC taste test intensity ratings across CRS patients. RESULTS: Sinonasal swabs were obtained from 59 patients, with 42 of the 59 samples demonstrating in vitro biofilm formation. Analysis revealed an inverse linear association between in vitro biofilm formation and PTC taste intensity ratings (p = 0.019) for all patients. This association was exclusively driven by nonpolypoid CRS patients (p = 0.0026). CONCLUSION: In vitro biofilm formation from sinonasal clinical isolates is inversely correlated with PTC taste sensitivity in nonpolypoid CRS patients.

T2R38 genotype is correlated with sinonasal quality of life in homozygous ΔF508 cystic fibrosis patients.

BACKGROUND: Chronic rhinosinusitis (CRS) is very prevalent in the cystic fibrosis (CF) patient population, and leads to high morbidity and markedly decreased quality of life (QOL). Identification of genetic markers that contribute to CRS symptoms in these patients can allow for risk stratification and tailoring of medical and surgical treatments. T2R38 is a bitter taste receptor expressed in the sinonasal tract, and nonfunctional alleles of this receptor have been implicated in treatment-refractory CRS in non-CF patients. The purpose of this study is to investigate the significance of T2R38 genotype in the variability of sinonasal QOL and CRS disease severity in a sample of CF patients. METHODS: ΔF508 homozygous CF patients were recruited from the University of Pennsylvania Cystic Fibrosis Center and were genotyped for the TAS2R38 locus. To assess sinonasal symptom severity, a 22-item Sino-Nasal Outcome Test (SNOT-22) was collected from each patient. Additional demographic and medical history data was obtained at the time of patient enrollment. RESULTS: A total of 49 ΔF508 homozygous CF patients aged 18 to 32 years were included in the final SNOT-22 score analysis. Individuals with 2 functional T2R38 alleles (PAV/PAV) had significantly lower SNOT-22 scores (n = 49, p < 0.05). On further breakdown of SNOT-22 subcategories, rhinologic symptoms specifically were less severe in PAV/PAV patients than patients with other genotypes (n = 47, p < 0.05). CONCLUSION: Our investigation indicates that T2R38 genotype correlates both with SNOT-22 scores and rhinologic-specific QOL in ΔF508 homozygous CF patients.

Phenylthiocarbamide taste sensitivity is associated with sinonasal symptoms in healthy adults.

BACKGROUND: The bitter taste receptor T2R38, expressed in the tongue and nasal epithelium, has been shown to trigger sinonasal innate immunity contributing to the prevention of gram-negative upper airway bacterial infections. Common polymorphisms of the T2R38 gene, correlating with bitter taste sensitivity to phenylthiocarbamide (PTC), have been linked to differences in sinonasal innate immune response, with specific genotypes significantly more common in medically recalcitrant chronic rhinosinusitis patients. The purpose of this study was to examine this association between T2R38 function and sinonasal infection or symptoms in a healthy population. METHODS: A survey of the frequency of sinus infections, as well as other nasal symptoms such as colds, allergies, and overall nasal quality of life (nQOL), was administered to healthy adult participants. nQOL was measured using a 0 to 3 scale of worsening symptoms. A PTC compound taste strip was administered with T2R38 taste sensitivity classified as extremely, somewhat, or not sensitive. RESULTS: Among 217 participants (55% female, 70% Caucasian, 42% age 21 to 25 years), 30% did not detect bitterness (nontasters), 34% were moderate tasters, and 36% were "supertasters," experiencing a strong, unpalatable bitterness. Supertasters were associated with less frequent sinus infections (p = 0.04), and PTC sensitivity was predictive of nasal symptoms: Supertasters had the best nQOL scores, followed by moderate tasters and nontasters (means: 0.65, 0.81, 1.00, respectively; p = 0.014 for trend). There were no significant associations with other variables. CONCLUSION: This study provides evidence that T2R38 functionality in the tongue correlates with nasal symptoms in healthy individuals.

Sensory characterization of commercial soluble coffees by Flash Profile / Caracterização sensorial de cafés solúveis comerciais por Perfil Flash

In todays competitive market, there is a lack of simple methods for sensory characterization of products. The Flash Profile is a combination of the Free Choice Profiling terms selection with a ranking method, based on the simultaneous presentation of all samples to be evaluated, providing a quick description and discrimination of a set of products. Thus, this study aimed to apply the Flash profile method on the characterization of commercial soluble coffees. Four soluble coffees selected by presenting diversity in the production process and composition were evaluated by 32 assessors in a single session. The coffee brews were prepared with 28 g of soluble coffee per 1000 mL of purified water, and added of 9.5 % sucrose. Initially, the whole set of samples were presented simultaneously for the glossary development. In individual discussion, each assessor was assisted on the elaboration of individual score sheet with the definition of each attribute. Subsequently, the four coffee beverages were presented simultaneously to the assessor, who ordered the samples in ascending order for the intensity of each attribute on its score sheet. The results were analyzed by Generalized Procrustes Analysis. The most relevant attributes in the description and discrimination of sweetened coffee brews were brown color, aroma and flavor of coffee, bitter taste, sweet taste and the presence of oil

Dentro do competitivo mercado atual, há demanda por métodos mais simples na descrição de produtos. O Perfil Flash (Flash Profile) é uma combinação do levantamento de atributos do Perfil Livre com um método de ordenação, baseado na apresentação simultânea de todas as amostras a serem avaliadas, proporcionando uma descrição e discriminação rápida de um conjunto de produtos. Dessa forma, o presente estudo visou empregar o método de Perfil Flash para caracterizar sensorialmente cafés solúveis comerciais. Quatro cafés solúveis selecionados por apresentar diversidade de processo e composição foram avaliados por 32 julgadores, em uma única sessão. As bebidas foram preparadas com 28 g de café solúvel para 1000 mL de água filtrada, e adicionadas de 9,5 % de sacarose. Primeiramente, todos os cafés foram apresentados simultaneamente aos julgadores para o desenvolvimento da lista de atributos. Em discussão individual, os julgadores foram assistidos na definição dos atributos e na elaboração da ficha de avaliação. Posteriormente, as quatro bebidas foram apresentadas simultaneamente ao julgador, que as ordenou em ordem crescente quanto à intensidade de cada atributo da sua ficha de avaliação. Os resultados foram avaliados por Análise Procrustes Generalizada. Os atributos mais relevantes na descrição e discriminação das bebidas de cafés adoçadas foram cor marrom, aroma e sabor de café, gosto

Sensory characterization of commercial soluble coffees by Flash Profile / Caracterização sensorial de cafés solúveis comerciais por Perfil Flash

In todays competitive market, there is a lack of simple methods for sensory characterization of products. The Flash Profile is a combination of the Free Choice Profiling terms selection with a ranking method, based on the simultaneous presentation of all samples to be evaluated, providing a quick description and discrimination of a set of products. Thus, this study aimed to apply the Flash profile method on the characterization of commercial soluble coffees. Four soluble coffees selected by presenting diversity in the production process and composition were evaluated by 32 assessors in a single session. The coffee brews were prepared with 28 g of soluble coffee per 1000 mL of purified water, and added of 9.5 % sucrose. Initially, the whole set of samples were presented simultaneously for the glossary development. In individual discussion, each assessor was assisted on the elaboration of individual score sheet with the definition of each attribute. Subsequently, the four coffee beverages were presented simultaneously to the assessor, who ordered the samples in ascending order for the intensity of each attribute on its score sheet. The results were analyzed by Generalized Procrustes Analysis. The most relevant attributes in the description and discrimination of sweetened coffee brews were brown color, aroma and flavor of coffee, bitter taste, sweet taste and the presence of oil

Dentro do competitivo mercado atual, há demanda por métodos mais simples na descrição de produtos. O Perfil Flash (Flash Profile) é uma combinação do levantamento de atributos do Perfil Livre com um método de ordenação, baseado na apresentação simultânea de todas as amostras a serem avaliadas, proporcionando uma descrição e discriminação rápida de um conjunto de produtos. Dessa forma, o presente estudo visou empregar o método de Perfil Flash para caracterizar sensorialmente cafés solúveis comerciais. Quatro cafés solúveis selecionados por apresentar diversidade de processo e composição foram avaliados por 32 julgadores, em uma única sessão. As bebidas foram preparadas com 28 g de café solúvel para 1000 mL de água filtrada, e adicionadas de 9,5 % de sacarose. Primeiramente, todos os cafés foram apresentados simultaneamente aos julgadores para o desenvolvimento da lista de atributos. Em discussão individual, os julgadores foram assistidos na definição dos atributos e na elaboração da ficha de avaliação. Posteriormente, as quatro bebidas foram apresentadas simultaneamente ao julgador, que as ordenou em ordem crescente quanto à intensidade de cada atributo da sua ficha de avaliação. Os resultados foram avaliados por Análise Procrustes Generalizada. Os atributos mais relevantes na descrição e discriminação das bebidas de cafés adoçadas foram cor marrom, aroma e sabor de café, gosto

Interação molecular entre alfa-ciclodextrina e triptofano / Alfa-ciclodextrin and tryptophan molecular interaction / Interacción molecular entre alfa-ciclodextrina y triptófano

O objetivo deste trabalho foi determinar a constante de formação do complexo de inclusão entre a alfa-ciclodextrina e o aminoácido triptofano. Para a determinação da constante de inclusão, foi utilizado o método competitivo do alaranjado de metila. O triptofano realiza interações moleculares com a alfa-ciclodextrina com constante de inclusão de 36,16 M-1. Estes resultados embasam o desenvolvimento de trabalhos de entrega metabólica de triptofano e a redução de gostos indesejados de proteínas hidrolisadas utilizadas na alimentação animal.

The objective of this research was to determine the inclusion constant between tryptophan and alpha-cyclodextrin (alpha-CD) by spectrophotometry based on methyl orange molecular probe. Tryptophan and alpha-CD showed molecular interaction with inclusion formation constants of 36.16 M-1. These results are important for the development of tryptophan metabolic delivery and reduction of the bitter taste from hydrolyzed proteins used to feed animals.

El objetivo de esta investigación fue determinar la constante de formación del complejo de inclusión entre alfa-ciclodextrina y triptófano. Para la determinación de la constante de inclusión, fue utilizado el método competitivo del naranja de metilo. El triptófano realiza interacciones moleculares con el alfa-ciclodextrina con constante de inclusión de 36,16 M-1. Estos resultados fundamentan el desarrollo de trabajos de entrega metabólica de triptófano y la reducción de gustos indeseados de proteínas hidrolizadas utilizadas en la alimentación animal.