Study of the Taste System PDF

Sandrine Chometton Center for Taste and Feeding Behavior (CSGA), Dijon Team « Sugars – Perception and Receptors (SuPeR) » Study of the Taste System Cutting-edge tools for studying the physiology of feeding behavior from animals to humans M2 P2Food Overview of...

Sandrine Chometton Center for Taste and Feeding Behavior (CSGA), Dijon Team « Sugars – Perception and Receptors (SuPeR) » Study of the Taste System Cutting-edge tools for studying the physiology of feeding behavior from animals to humans M2 P2Food Overview of the taste system Functions of the taste system - Perception of the taste quality and intensity (sensory- discriminative) - Motivation to facilitate or thwart ingestion - Physiological reflexes that prepare the body to appropriately handle ingested substances  Human Taste System Taste detectors Nervous signal Taste Circumvallate Foliate papillae buds Papillae Na+ Cl- Salivary Filiform Taste cells glands papillae Fungiform papillae Nerve Briand, L. (2017). La physiologie de la perception gustative. Pratiques en Nutrition, 13 (49), 10-13. Vallate papilla Human Taste System Conscious perception Thalamus Hypothalamus Hippocampus Solitatory tract nucleus Gustatory nerves Chorda tympani nerve Glossopharyngeal nerve Vagus nerve  Five primary taste qualities sensing of Physiological function diverse maturity of fruits, energy rich nutrients natural toxins bacterial contaminations (sugars) Sweet Bitter Sour Citric acid Fructose Caffeine Salty Umami “savory” Na+Cl- electrolyte Sodium source of A.A. balance chloride L-Glutamate (protein-rich food) The myth of the Tongue Map Amer Bitter Acide Sweet/ Sucré/Umami Umami Salé Salty (Chandrashekar et al., 2006)  ATP is released by type II cells -> we can analyze if there is a response to stimulus. Taste cells (Von Molitor et al., 2020) Two classes of taste detectors Sour Salty Sweet Bitter Umami Na+Cl- fructose L-glu citric acid sodium chloride caffeine a b g Ion channels G-protein coupled receptors (GPCRs) Otop1 ENaC T1R2/T1R3 25 25 Tas2Rs T1R1/T1R3 Briand, L., Salles, C. (2016). Taste perception and integration. Cell model I. Primary cells / tissue Isolated animal primary taste cells, taste buds, tongue epithelia and slices were used in combination with fluorescent dyes in ex vivo live imaging experiments for unravelling the intracellular signal transduction pathways and intercellular communication Fura-2: dual excitation single emission Ca2+ indicator, the ratio of fluorescent emission at the two excitation wavelenghts is directly related to the amount of intracellular Ca2+, detect physiological cytosolic Ca2+ concentrations CaO / CaG: especially when measuring fast Ca2+ changes such as voltage-gated Ca2+ currents generated by action potentials (fluorescent emission increases upon Ca2+ binding) (Von Molitor et al., 2020) I. Primary cells / tissue ATP-dependent fluorescence of a circumvallate taste bud and an isolated taste cell loaded with fura-2. (Baryshnikov et al., 2003) I. Primary cells / tissue Ca2+ response to local apical stimulation with the bitter compound quinine (CaG) (Caicedo et al., 2002) II. Recombinant systems Recombinant systems expressing taste receptors and downstream signaling molecules in non-taste cell lines were employed upon loading with chemical dyes in plate reader experiments to study receptor structure, binding sites, selectivity and sensitivity in high throughput. (Von Molitor et al., 2020)  Recombinant systems : there is a response for the red experiment. Increase of conc in sweet solution -> we can see at which conc we can see that we have II. Recombinant systems 50% of the max response. (Belloir et al., 2021) III. Biosensor cells Biosensor cells expressing specific neurotransmitter/hormone receptors were used upon loading with fluorescent dyes and juxtaposed to taste cells/tissue to monitor with live imaging experiments the release of neurotransmitters such as ATP, serotonin, noradrenaline, GABA and acetylcholine. Biosensor cells (BCs) are living cells that detect the presence and concentration of a certain analytical substance. (Von Molitor et al., 2020) III. Biosensor cells (Huang et al., 2007) III. Biosensor cells cbx = carbenoxolone (blocker of Px channels) (Huang et al., 2007) Rodent model I. The short-term two-bottle preference test Taste sensitivity Intake of a test fluid to that of the control fluid (Gaillard and Stratford, 2020) II. Brief-access taste test A: Sipper tubes B: Mobile bottle rack C: Mouse cage D: Motorized shutter (Gaillard and Stratford, 2020)  Brief-access taste test : we need the mice to drink to every bottle at least 2 times (as II. Brief-access taste test there are 7 bottles, it makes 14 times). Behavioral responses of a rodent to gustatory cues by minimizing post-ingestive and post-absorptive effects The licking behavior is measured by recording the number of licks and the interval between licks through a contact circuit. Specifically, an undetectable small current passes through the sipper tube. A change in capacitance is induced by the contact of the tongue on the sipper tube and is recorded through an analog-to-digital converter and computer system. Preference for specific taste (Gaillard and Stratford, 2020) II. Brief-access taste test (Gaillard and Stratford, 2020) III. Conditioned taste aversion Animals (including humans) will actively reject foods that previously made them feel ill Animals are especially proficient at detecting a taste that previously caused malaise at concentrations much lower than those behaviorally preferred Taste threshold (Gaillard and Stratford, 2020) III. Conditioned taste aversion (Gaillard and Stratford, 2020) III. Conditioned taste aversion (Gaillard and Stratford, 2020) III. Conditioned taste aversion Conditioned taste aversion vs Conditioned taste avoidance Taste become aversif after Taste is still good but avoidance to a malaise experience eat (allergic reaction for example) (https://www.labroots.com/trending/neuroscience/13373/conditioned-taste-aversion-cta) IV. Taste reactivity Ingestive = act of consumption - Mouth movements - Tongue protrusions - Paw licking Aversive = rejection - Gapes - Chin rubs - Forelimb flails - Head shakes (Schier and Spector, 2019)  V. Glucose tolerance test Physiological reflexes that prepare the body to appropriately handle ingested substances: Cephalic Phase of Insulin Release (CPIR) (Tonosaki et al, 2007)  V. Glucose tolerance test Sugars Sweet-tasting proteins Sucrose Glucose Brazzein (6.5 kDa) Monellin (10,7 kDa) Fructose Sweet … …. T1R2/T1R3 Amino acids Sweeteners D-tryptophan Saccharin Glycine (Glendinning et al, 2015) Acesulfame K … Sucralose … V. Glucose tolerance test Oral GTT Glucose Insulin Glucose-containing solution V. Glucose tolerance test Gavage GTT / Intraperitoneal Injection GTT Glucose Insulin  VI. Rodent model - Regular (food deprived, thirsty, diet experience, …) (Iizuka, 2022) (Chometton et al., 2022) LCS= Low Calory Sweetener. (Tsan, Chometton et al., 2022)  VI. Rodent model - Physiopathological state (obesity, diabetes, …) (Harnischfeger and Dando, 2021) (Gondivkar et al., 2009) VI. Rodent model (modified from Wszola et al., 2021) Chemical induction - Physiopathological state (obesity, diabetes, …) Genetically induced (Bastias-Perez et al., 2020) (Kottaisamy et al., 2021) VI. Rodent model - Modulation of lingual RNA / protein expression, receptor activity, … Circumvallate (CV) Fungiform (FF) Human studies I. Detection and Recognition Thresholds - Provide estimates of the lowest chemical concentration that can be perceived by an individual. - Detection threshold (DT): the substance can be discriminated from pure solvent in a forced choice task. - Recognition threshold (RT): the substance is both perceived and identifiable as having a specific perceptual quality. ✓ taste each sample for 5 s then spit, ✓ record whether there was: ❑ an absence of taste (water-like), ❑ taste identified but quality unknown, ❑ taste quality perceived. DT = the concentration at which the response ‘taste identified but quality unknown’ was selected. RT = the concentration at which the taste quality was correctly identified twice consecutively. (Webb et al., 2015) I.Bis Triangular taste detection threshold - Three-alternative forced-choice procedure ✓ Sets of three samples: 2 control (water) and 1 stimulus) ✓ Indicate which sample is different from the other two Correct identification of the stimulus sample at a given concentration three consecutive times = gustatory threshold II. Suprathreshold intensity ratings - This test occur at concentrations between the recognition threshold and the terminal threshold. - Intensity of the same stimulus can vary widely across individuals. ✓ taste each sample ✓ record their perceived overall intensity on a generalized labeled magnitude scale (Webb et al., 2015)  III. Quantification of fungiform papillae - Fungiform Papillae (FP) contain taste buds. - Chosen for quantification because of their abundance and location on the anterior tongue compared to foliate and circumvallate papillae. - Presumably, the more FP an individual has, a stronger signal is sent centrally from the FP, resulting in a more intense taste perception. ✓ dry and remove excess saliva from the front section of the tongue with a filter paper Circumvallate Foliate ✓ stain the anterior part of the tongue with a blue dye and a cotton tip papillae Papillae ✓ dry the front section of the tongue with a filter paper to remove the excess dye ✓ place a piece of paper with a 6-mm diameter cut-out circle over the dyed section ✓ take a photo and count Filiform papillae Fungiform papillae (Webb et al., 2015) IV. Gustatory evoked potentials (GEPs) FIGURE 1 | Schematic view of the taste delivery system. Water and taste solutions were driven through the system by compressed air (controlled through a manometer). Two parallel silicone tubes were used; one for water and the other for the taste solution. Switching between water and the taste solutions was performed by two electromagnetic valves controlled by an electronic device. Each subject put the two parallel tubes on the middle of his/her tongue in his/her mouth. Solutions were delivered to the tongue through a hole at the end of each tube. (Jacquin-Piques et al., 2016) IV. Gustatory evoked potentials (GEPs) Stimulus was delivered 20 times for 1 s each time. Each stimulus was separated by a 1-min interval in which water alone was delivered. Electroencephalogram (EEG) recording in the primary and secondary gustatory cortex. (Jacquin-Piques et al., 2016) IV. Gustatory evoked potentials (GEPs) - Initial latency: time between stimulus delivery and the onset of the increase in potential, - Amplitude of response: from positive to negative peaks = intensity of cerebral activation - Duration of the GEPs: between the end and the beginning (corresponding to the initial latency) of the GEP, - Positive peak: peak pointing down, and negative peak: peak pointing up P1 the first positive peak and N1 the higher negative peak = sensory cerebral response P2 the second positive peak = cognitive response (interpretation of the stimulus) (Jacquin-Piques et al., 2016)