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Alterações do gosto provocadas pelo uso de derivados de platina têm sido descritos. Contudo, poucos estudos qualificam os gostos prejudicados e se essas alterações derivam exclusivamente da quimioterapia. Objetivo: avaliar as alterações dos gostos doce, azedo, salgado, amargo e umami, em pacientes recebendo quimioterapia com derivados de platina (QTx). Métodos: Foram estudados 43 sujeitos, 21 do grupo estudo e 22 do grupo controle, em dois tempos, antes do início da QTx e uma após dois ciclos de QTx. A ingestão alimentar habitual, Índice de massa corporal e força da preensão palmar por dinamometria e fadiga (através do pictograma da fadiga) foram avaliados para caracterizar o grupo estudado. Foram realizados testes gustativos com Taste Strips, para os 4 gostos e o umami foi estudado comparando por escala Likert a apreciação do gosto, utilizando alimento com e sem glutamato monossódico (GMS). A análise estatística foi realizada com análise de variância (ANOVA) de medidas repetidas, modelo mixto. Adotou-se como nível de significância p<=0,05. Resultados: O salgado e o azedo foram os gostos mais comprometidos no grupo estudo (p=0,001 e 0,05); assim como os receptores ionotrópicos (p=0,02) responsáveis pela identificação desses gostos. Houve diferença entre o T0 e T1 para índice de massa corporal (IMC), dinamometria e impacto nas atividades cotidianas, pelo pictograma da fadiga (p=0,008,0,009 e 0,006 respectivamente).Conclusão: esse achados sugerem que a doença parece exercer um papel importante na alteração de reconhecimento dos gostos, principalmente nos gostos salgado e azedo, identificados pelos receptores ionotrópicos, o que parece relacionar-se com as mudanças alimentares. Os quimioterápicos demostraram uma contribuição para comprometimento da funcionalidade e fadiga / Changes in taste caused by the use of platinum drugs have been described. However, few studies qualify prejudiced tastes and whether these changes are derived exclusively from chemotherapy. Methods: A total of 43 subjects, 21 from the study group and 22 from the control group, were studied in two times, with the aim of evaluating changes in sweet, sour, salty, bitter and umami tastes in patients receiving chemotherapy with platinum drugs (QTx) before the start of QTx, and one after two cycles of QTx. The usual dietary intake, body mass index (BMI) and handgrip strenght by dynamometry and fatigue (through the fatigue pictogram) were evaluated to characterize the group studied. Taste Strips tests were performed for all 4 tastes and umami was studied by comparing Likert\'s taste tasting using monosodium glutamate (GMS) food. Statistical analysis was performed with analysis of variance (ANOVA) of repeated measures, mixed model. It was adopted as significance level p<=0.05. Results: Salty and sour were the most affected tastes in the study group (p = 0.001 and 0.05); as well as the ionotropic receptors (p = 0.02) responsible for identifying these tastes. There was a difference between T0 and T1 for BMI, dynamometry and impact in daily activities, by the fatigue pictogram (p = 0.008,0,009 and 0.006 respectively). Conclusion: these findings suggest that the disease seems to play a role important in altering the recognition of tastes, especially in salty and sour tastes, identified by ionotropic receptors, which seems to be related to dietary changes. The platinun drugs demonstrated a contribution to impairment of functionality and fatigue

In humans, taste is one of the five senses, and helps in the recognition of nutritionally important and potentially harmful substances. It triggers innate behaviour to accept or reject food. Humans can sense five basic tastes, which are sweet, umami, bitter, salt and sour. The receptors that mediate bitter, sweet and umami tastes belong to the G protein-coupled receptor (GPCR) superfamily. A group of three receptors sense sweet and umami tastes, whereas bitter taste is sensed by 25 bitter taste receptors (referred as T2Rs). T2Rs are activated by structurally diverse natural and synthetic bitter compounds. Many common pharmaceutical compounds are bitter in taste and these are effective ligands for T2Rs. Recent finding of T2Rs in extra-oral tissues suggests these receptors are also involved in various physiological and pathophysiological processes. To understand the structure and function of these receptors, studies directed at elucidating their mechanisms of activation, and identification of novel ligands including bitter blockers (antagonists and inverse agonists), are required. To obtain mechanistic insights into the role of the highly conserved, and receptor specific residues, two bitter taste receptors (T2R1 and T2R4) were targeted. In this study, a combination of molecular, biochemical and pharmacological approaches were used to identify the amino acids and motifs, important for T2Rs to switch from inactive to active state. A hydrogen-bonding network between transmembrane (TM) helices 1-2-7 was identified as important for T2R activation. Alanine-scan mutagenesis of intracellular loops (ICLs) 2 and 3 identified T2R regions important for G protein binding, and receptor activation. A pharmacological method was developed, to screen potential bitter blockers for T2Rs. Using this method, three novel bitter blockers, which include two natural antagonists and one synthetic inverse agonist for T2R4, were discovered. The role of expression tags in enhancing T2R4 expression was also pursued. T2R4 expression on the cell surface was increased 2.5 fold, when its N-terminus was tagged with rhodopsin N-terminal 33 residues (Rho33- T2R4 chimera). In conclusion, work carried out provides novel insights into the mechanisms of T2R activation, and in the discovery of bitter blockers for T2R4.

Sweet taste receptors are primarily found in the oral cavity of the mammalian species. However, recent studies have shown that sweet taste receptors can be found in extraoral tissues such as the pancreas, intestines, and adipose tissue. Our lab has previously found that sweet taste receptors are down-regulated on the pancreas in the presence of high plasma glucose levels. In order to assess the possibility that sweet taste receptors respond to high levels of glucose by suppressing its expression, we wanted to see if they reacted similarly on the intestines. We found that intestinal sweet taste receptors are down regulated in the presence of a 24 hour high sucrose diet (60% sucrose), and a 7 day high sucrose diet in both wild type (WT) mice on the high sucrose diet, and T1R2-KO (lacking sweet taste receptors) mice. We also examined their glucose excursion levels, and found that these mice are lacking a normal response to dietary glucose via an oral glucose tolerance test (OGTT). This led us to conclude that the mice lacking sweet taste receptor expression exhibit abnormal glucose absorption, possibly indicating that sweet taste receptors regulate glucose absorption in the intestines.

The relationship between initial intracellular pH (pHi) and associated cell volume change was investigated by simultaneous measurement of pHi and cell volume with fluorescence imaging in polarized fungiform taste receptor cells (TRCs) loaded with BCECF in vitro. Ammonium pulses caused a brief, reversible alkalinization in pHi and induced cell swelling. Sodium-acetate pulses reversible decreased TRC pHi and induced cell shrinkage. Removal weak acids and return to Control Ringer's solution (CR) causedTRC pHi and volume to overshoot baseline levels before fully recovering. Replacing CR with zero-sodium solution resulted in irreversible acidification of TRC pHi and induced cell swelling. Addition of sodium allowed reversal of TRC pHi and volume and return to baseline levels. Treating TRCs with cytoskeleton inhibitors, phalloidin and cytochalasin, before acidic stimulation did not affect TRC pHi, but did result in an altered TRC volume change. I conclude that a decrease in TRC pHi induces cell shrinkage via the actin cytoskeleton. Cell shrinkage as a result of a change in pHi activates NHE1 to restore TRC pHi and volume.

Die Wahrnehmung von Geschmacksempfindungen beruht auf dem Zusammenspiel verschiedener Sinneseindrücke wie Schmecken, Riechen und Tasten. Diese Komplexität der gustatorischen Wahrnehmung erschwert die Beantwortung der Frage wie Geschmacksinformationen vom Mund ins Gehirn weitergeleitet, prozessiert und kodiert werden. Die Analysen zur neuronalen Prozessierung von Geschmacksinformationen erfolgten zumeist mit Bitterstimuli am Mausmodell. Zwar ist bekannt, dass das Genom der Maus für 35 funktionelle Bitterrezeptoren kodiert, jedoch war nur für zwei unter ihnen ein Ligand ermittelt worden. Um eine bessere Grundlage für tierexperimentelle Arbeiten zu schaffen, wurden 16 der 35 Bitterrezeptoren der Maus heterolog in HEK293T-Zellen exprimiert und in Calcium-Imaging-Experimenten funktionell charakterisiert. Die Daten belegen, dass das Funktionsspektrum der Bitterrezeptoren der Maus im Vergleich zum Menschen enger ist und widerlegen damit die Aussage, dass humane und murine orthologe Rezeptoren durch das gleiche Ligandenspektrum angesprochen werden. Die Interpretation von tierexperimentellen Daten und die Übertragbarkeit auf den Menschen werden folglich nicht nur durch die Komplexität des Geschmacks, sondern auch durch Speziesunterschiede verkompliziert. Die Komplexität des Geschmacks beruht u. a. auf der Tatsache, dass Geschmacksstoffe selten isoliert auftreten und daher eine Vielzahl an Informationen kodiert werden muss. Um solche geschmacksstoffassoziierten Stimuli in der Analyse der gustatorischen Kommunikationsbahnen auszuschließen, sollten Opsine, die durch Licht spezifischer Wellenlänge angeregt werden können, für die selektive Ersetzung von Geschmacksrezeptoren genutzt werden. Um die Funktionalität dieser angestrebten Knockout-Knockin-Modelle zu evaluieren, die eine Kopplung von Opsinen mit dem geschmacksspezifischen G-Protein Gustducin voraussetzte, wurden Oozyten vom Krallenfrosch Xenopus laevis mit dem Zwei-Elektroden-Spannungsklemm-Verfahren hinsichtlich dieser Interaktion analysiert. Der positiven Bewertung dieser Kopplung folgte die Erzeugung von drei Mauslinien, die in der kodierenden Region eines spezifischen Geschmacksrezeptors (Tas1r1, Tas1r2, Tas2r114) Photorezeptoren exprimierten. Durch RT-PCR-, In-situ-Hybridisierungs- und immunhistochemische Experimente konnte der erfolgreiche Knockout der Rezeptorgene und der Knockin der Opsine belegt werden. Der Nachweis der Funktionalität der Opsine im gustatorischen System wird Gegenstand zukünftiger Analysen sein. Bei erfolgreichem Beleg der Lichtempfindlichkeit von Geschmacksrezeptorzellen dieser Mausmodelle wäre ein System geschaffen, dass es ermöglichen würde, gustatorische neuronale Netzwerke und Hirnareale zu identifizieren, die auf einen reinen geschmacks- und qualitätsspezifischen Stimulus zurückzuführen wären. / Taste impression is based on the interaction of taste, smell and touch. To evaluate the nutritious content of food mammals possess five distinct taste qualities: sweet, bitter, umami (taste of amino acids), sour and salty. For bitter, sweet, and umami compounds taste signaling is initiated by binding of tastants to G protein-coupled receptors. The interactions of taste stimuli, usually watersoluble chemicals, with their cognate receptors lead to the activation of the G protein gustducin, which, in turn, initiates a signal resulting in the activation of gustatory afferents. However, details of gustatory signal transmission and processing as well as neural coding are only incompletely understood. This is partly due to the property of some tastants to elicit several sensations simultaneously, unspecific effects caused by the temperature, viscosity, osmolarity, and pH of the solvents, as well as by mechanical stimulation of the tongue during stimulus application. The analysis of gustatory processing of taste information are mainly based on mouse models after stimulation with bitter taste stimuli. Even though it is known that the mouse genome codes for 35 bitter taste receptor genes only few of them had been analysed so far. For better understanding and interpretation of animal experiments 16 mouse bitter receptors had been analysed by Calcium Imaging experiments with HEK293T cells. The data reveal that mouse bitter taste receptors are more narrow tuned than human bitter taste receptors, proving that the ligand spectra of murine and human orthologous receptors are not complient. In order to avoid the disturbing effects of solvents and stimulus application on the analysis of gustatory information transfer and processing, I employ an optogenetical approach to address this problem. For this purpose I generated three strains of gene-targeted mice in which the coding regions of the genes for the umami receptor subunit Tas1r1, the sweet receptor subunit Tas1r2 or the bitter taste receptor Tas2r114 have been replaced by the coding sequences of different opsins (photoreceptors of visual transduction) that are sensitive to light of various wavelengths. In these animals I should be able to activate sweet, bitter, or umami signalling by light avoiding any solvent effects. In initial experiments of this project I demonstrated that the various visual opsins indeed functionally couple to taste signal transduction pathway in oocyte expression system, generating basic knowledge and foundation for the generation of the gene-targeted animals. The knockout-knockin strategies have been successfully realized in the case of all three mouse models, revealed by RT-PCR, in situ hybridization and immunohistochemical analysis of taste papillae. All data confirm that the particular taste receptors have been replaced by the different opsins in taste cells. Further analysis concerning the functional consequences of opsin knockin and taste receptor knockout are part of prospective work.

Chez les animaux et en particulier les insectes, l’alimentation comprend une phase d’examen sensoriel qui précède l’ingestion, afin notamment d’éviter d’ingérer des substances toxiques. Cette détection fait intervenir des cellules spécialisées dans la détection de telles molécules, cellules qui sont généralement qualifiées de sensibles aux goûts « amers ». A l’aide d’observations électrophysiologiques et comportementales, nous avons abordé comment un insecte modèle, la drosophile, était capable de détecter des substances potentiellement toxiques mélangées à des sucres à l’aide de ses neurones gustatifs. Dans une première partie, nous avons étudié la détection de la L-canavanine, qui est un acide aminé non protéique. Cette molécule est toxique pour l’homme comme pour les animaux car elle est confondue par le métabolisme avec un acide aminé, la L-arginine, et intégrée à sa place dans les protéines. En utilisant des constructions génétiques et en particulier le système UAS-Gal4, nous avons montré que la Lcanavanine est détectée par des cellules gustatives qui expriment une protéine réceptrice GR66a, qui est impliquée dans la détection de nombreuses substances amères. Nous avons également montré que, contrairement à la caféine, la détection de L-canavanine nécessite des protéines Gαo fonctionnelles. Nous avons ensuite étudié les interactions sucré-amer. Dans un premier travail, nous avons montré que l’addition de Lcanavanine une solution sucrée n’altérait pas la détection des sucres, contrairement à la strychnine qui peut complètement supprimer la détection du sucre dans les cellules gustatives. Grâce à des ablations spécifiques des cellules détectant l’amer, nous avons pu montrer que cette inhibition était une propriété intrinsèque des cellules sensibles aux. sucres. Les cellules sensibles aux sucres auraient donc des sites récepteurs non identifiés, sensibles à certains ligands amers. Nous avons également abordé des interactions inverses, à savoir l’inhibition de la détection de substances amères par des sucres, en confrontant 4 substances amères (denatonium, berberine, caféine, umbelliferone) à 12 sucres. Les observations que nous avons réalisées montrent que certains sucres exercent un effet inhibiteur sur la détection des molécules amères testées. En utilisant des outils génétiques permettant l’ablation des cellules sensibles aux sucres, nous avons montré que cette inhibition est une propriété intrinsèque des cellules sensibles à l’amer. Cependant, cet effet inhibiteur est loin d’être aussi efficace que l’inhibition des substances amères sur la détection des sucres. Dans une dernière partie, nous avons évalué la modulation de la détection gustative à l’aide d’analogues d’une neuro-hormone, la leucokinine, connue pour ses effets sur la diurèse. Lorsqu’elle est mélangée à une solution sucrée, ces analogues inhibent la détection des sucres par les sensilles gustatives, à la fois chez le moustique Aedes aegypti et chez la drosophile. La détection de substances « amères » par les cellules gustatives de drosophiles implique donc deux voies de codage : l’une, spécifique, concerne des cellules dédiées à la détection des substances amères ; l’autre, moins spécifique, affecte les cellules dédiées à la détection des sucres. De manière réciproque, ces cellules dédiées à la détection des molécules sont affectées par la présence de ligands sucrés. Le codage des informations gustatives à la périphérie est donc un phénomène plus complexe qui nécessite d’étudier plus précisément la détection de composés en mélanges. / In most animals including insects, ingestion is preceded by a close examination of the food, for example in order to detect the presence of potentially noxious chemicals. This detection involves specialized gustatory cells, which are generally described as sensitive to “bitter” tastes. Using electrophysiology and behavioral observations, we studied how a model insect, Drosophila melanogaster, can detect potentially toxic substances (described here as “bitter”) when mixed with sugar molecules, with their gustatory neurons. In a first part, we studied how L-canavanine is detected. Lcanavanine is a pseudo amino acid, which is confounded with L-arginine by the metabolism. Proteins which include Lcanavanine are non-functional and this compound is toxic for animals including insects. Using genetic constructions based on the UAS-Gal4 expression system, we showed that Lcanavanine is detected by gustatory cells expressing a receptor protein, GR66a, which is specific to most cells capable of detecting bitter substances. We also showed that, contrary to caffeine, the detection of L-canavanine requires functional Gαo proteins. Then, we studied some aspects of the detection of mixtures of sweet and bitter molecules. In a first approach, we contributed to establish that L-canavanine does not impact sugar detection, while other chemicals like strychnine completely inhibit sugar detection. By using the UAS-Gal4 system to ablate bitter-sensitive cells, we could demonstrate that such inhibition is a specific property of sugar- sensitive cells. These cells should have thus receptors for bitter substances which have not been identified yet. We also examined the reverse interaction, which is a possible role of sweet molecules to inhibit the detection of bitter substances. We examined the detection of denatonium, berberine, caffeine and umbelliferone in the presence of 12 different sugars, using behavioral and electrophysiology observations. By using genetic construction to ablate sugar-sensitive cells, we found that the sugar inhibitory action is not due to the presence of sugar-sensitive cells. It should be noted, however that in our experimental conditions, this inhibitory action is less efficient than the inhibition of bitter upon sugar detection. In a last part, we examined the modulation of gustatory perception by analogs of leucokinine, which is a neuropeptide involved in the diuresis of insects. We show that these analogs, when mixed with sugars in solution, can inhibit sugar detection by gustatory sensilla, both in Aedes aegypti mosquitoes and in Drosophila. The detection of bitter molecules by gustatory neurons in Drosophila thus involves two main coding channels: one is specific, and involves gustatory cells dedicated to the detection of bitter molecules; the second one, less specific, is affecting cells which are dedicated to the detection of sugar molecules. Gustatory coding is thus a more complex phenomenon than previously thought on the basis of examining responses to single molecules, thus urging to study the responses of gustatory receptors to more complex and natural mixtures.

En mängd olika faktorer har visat sig påverka smakperceptionen. Ålder, fetma och den mikrobiellamiljön i munhålan är bara några exempel på omständigheter som kan resultera i smak-skillnader.Denna litteraturstudie syftar till att översiktligt granska de mekanismer som är involverade i munnenssmakuppfattning samt andra smakpåverkande faktorer såsom sjukdomar, kostvanor och oralametaboliter för att sedan utvärdera om samband existerar mellan dessa. Metabolismen som utförs avmikrober i saliv och tungfilm diskuteras också som potentiella variabler i smakuppfattningen, baseratpå att en adaption (smak-anpassning) i munhålan kan orsaka lägre detektionströsklar. Studienpresenterar smakförstärkarna miraculin och curculin, då dessa har en förmåga att förstärka sötasmaker genom modulering av smakreceptorerna. Alla dessa processer i munhålan är avgörande för attförstå komplexiteten i individers smakuppfattning. Den mikrobiella aktiviteten i munnen tyckspåverka smakperceptionen, därför uppmuntras ytterligare studier kring oral mikroflora och smak föratt vidare utvärdera dess korrelation. Insamlad information kan vara av relevans för biotekniskaändamål eller sensoriska tester. / Many different factors have been shown to influence taste perception. Age, obesity, olfactoryresponses, sensitivity to the chemical 6-n-propylthiouracil (PROP-sensitivity), and even the microbialcomposition of the oral cavity are just a few examples of circumstances related to taste differences.This literature review aims to briefly assess taste transduction mechanisms and other taste-affectingfactors such as disease, dietary patterns, and oral metabolites to evaluate if correlations exist. Themetabolites made by microbes present in saliva and tongue film are also being discussed as variablesin the subjectiveness of taste, suggesting that adaptation in the oral cavity is causing lower detectionthresholds for specific tastes. A section presenting flavor-enhancers exemplifies the ability ofparticular proteins to amplify sweet tastes through the modulation of sweet receptors. Excludingolfactory responses, these in-mouth processes are crucial to understanding the complexity of flavor.Microbial activity in the mouth appears to play a role in the individuality of taste. Since this is anemerging area of research, future studies will help identify and characterize the connections betweentaste and oral microbiota. Assembled information in this review could also be relevant forbiotechnical purposes or sensory tests.

Molécules du goût et odeurs se fixent sur des récepteurs dits gustatifs et olfactifs, présents dans la bouche et le nez. Ils sont donc en contact avec le monde environnant. Toutefois, on les trouve également dans des organes isolés de l’extérieur, comme le pancréas ou le cerveau, où ils ne sont plus impliqués dans la détection du non-soi. Ils y régulent la glycémie ou l’activation du système immunitaire. Dans le cerveau, leurs rôles demeurent mystérieux. Mon travail a consisté à déterminer: 1) si, et où les récepteurs gustatifs et olfactifs sont présents dans le cerveau humain, 2) quand, où et pourquoi les récepteurs olfactifs sont présents dans le cerveau de souris et 3) si une maladie comme Alzheimer peut modifier leur expression. Mes résultats montrent qu’ils sont présents dans l’ensemble du cerveau humain et particulièrement dans le «cerveau émotionnel». De plus, le cerveau de souris «Alzheimer» surexprime des récepteurs olfactifs, notamment dans les neurones. Le cerveau est donc capable de goûter et sentir son monde intérieur. On peut imaginer que ces récepteurs jouent un rôle dans la détection de la maladie et, qui sait, qu’ils participent à la lutte contre ses effets néfastes. / Taste molecules and odours bind to so-called gustatory and olfactory receptors present in the mouth and nose. They are therefore in contact with the surrounding world. However, they are also found in organs isolated from the outside, such as the pancreas or brain, where they are no longer involved in the detection of non-self. They regulate blood sugar levels or the activation of the immune system. In the brain, their roles remain mysterious. My work consisted in determining: 1) if, and where, taste and smell receptors are present in the human brain, 2) when, where and why smell receptors are present in the mouse brain, and 3) whether a disease like Alzheimer's can change their expression. My results show that they are present in the entire human brain and particularly in the "emotional brain". In addition, the brains of "Alzheimer" mice overexpress olfactory receptors, particularly in neurons. The brain is therefore able to taste and feel its inner world. It is conceivable that these receptors play a role in detecting the disease and, who knows, in combating its harmful effects.