Associations between brain structure and perceived intensity of sweet and bitter tastes.
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ABSTRACT:
SUBMITTER: Hwang LD
PROVIDER: S-EPMC6470356 | biostudies-literature | 2019 May
REPOSITORIES: biostudies-literature
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Project description:Humans will eat almost anything, from caribou livers to rutabagas, but there are some types of foods, and their associated taste qualities, that are preferred by large groups of people regardless of culture or experience. When many choices are available, humans chose foods that taste good, that is, create pleasing sensations in the mouth. The concept of good taste for most people encompasses both flavor and texture of food, and these sensations merge with taste proper to form the concept of goodness. Although we acknowledge the universality of the goodness (sweet) or badness (bitter) of basic taste qualities, we also find that people differ, sometimes extremely so, in their ability to perceive and enjoy these qualities and, by extension, food and drink. The reasons for these differences among people are not clear but are probably due to a combination of experience beginning at an early age, perhaps in utero; learning, for example, as with conditioned taste aversions; sex and maturity; and perceptual differences that arise from genetic variation. In this review, we focus on individual variations that arise from genetic differences and review two domains of science: recent developments in the molecular biology of taste transduction, with a focus on the genes involved and second, studies that examine biological relatives to determine the heritability of taste perception. Because the receptors for sweet, savory (umami), and bitter have recently been discovered, we summarize what is known about their function by reviewing the effect of naturally occurring and man-made alleles of these receptors, their shape and function based on receptor modeling techniques, and how they differ across animal species that vary in their ability to taste certain qualities. We discuss this literature in the context of how taste genes may differ among people and give rise to individuated taste experience, and what is currently known about the genetic effects on taste perception in humans.
| S-EPMC1698869 | biostudies-literature
Project description:Recognition of sweet, bitter and umami tastes requires the non-vesicular release from taste bud cells of ATP, which acts as a neurotransmitter to activate afferent neural gustatory pathways. However, how ATP is released to fulfil this function is not fully understood. Here we show that calcium homeostasis modulator 1 (CALHM1), a voltage-gated ion channel, is indispensable for taste-stimuli-evoked ATP release from sweet-, bitter- and umami-sensing taste bud cells. Calhm1 knockout mice have severely impaired perceptions of sweet, bitter and umami compounds, whereas their recognition of sour and salty tastes remains mostly normal. Calhm1 deficiency affects taste perception without interfering with taste cell development or integrity. CALHM1 is expressed specifically in sweet/bitter/umami-sensing type?II taste bud cells. Its heterologous expression induces a novel ATP permeability that releases ATP from cells in response to manipulations that activate the CALHM1 ion channel. Knockout of Calhm1 strongly reduces voltage-gated currents in type?II cells and taste-evoked ATP release from taste buds without affecting the excitability of taste cells by taste stimuli. Thus, CALHM1 is a voltage-gated ATP-release channel required for sweet, bitter and umami taste perception.
| S-EPMC3600154 | biostudies-literature
Project description:BackgroundBitter 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.MethodsWe 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.ResultsCRS 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.ConclusionCRS 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.
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Project description:Taste preferences guide food choices and dietary behaviours, yet few studies have shown a relationship between sweet and savoury taste preference and differences in dietary intakes or energy consumed from different "taste clusters". We investigated differences in psycho-hedonic responses to sweet and savoury tastes and their association with energy intake, proportion of energy from macronutrients and energy intake from different "taste clusters". In addition, we evaluated correspondence between two methods to classify "sweet-liker" status and the overlap between sweet and savoury taste preferences. Psycho-hedonic responses to sweet and savoury tastes of female participants (n = 66) were captured via staircase paired preference and the "sweet-liker phenotype" classification method. Quantitative dietary energy and macronutrient intakes were measured using three-day food diary, and the relative contributions of specific taste clusters to energy intake were derived for each participant. All participants completed anthropometric assessments measuring body mass index (BMI) and adiposity. Results showed no association between sweet and savoury preferences with dietary energy or macronutrient intakes, though there was a trend towards higher sweet food consumption among "sweet-likers". A higher preference for savouriness was not associated with differences in daily energy intake, energy intake from protein, BMI or adiposity levels. There was little overlap in sweet and savoury preferences, suggesting a bi-modal split in taste preferences. "Sweet-likers" preferred a higher mean sucrose concentration than sweet "dislikers" (p < 0.001) indicating agreement between the two approaches. Future studies should consider comparing taste-liker differences using food choice tasks to address the current gap between taste preference measures and actual dietary behaviours.
| S-EPMC7555575 | biostudies-literature
Project description:The 25 human bitter taste receptors (TAS2Rs) are expressed on taste and extra-oral cells representing an integrated chemosensory system. The archetypal TAS2R14 is activated by > 150 topographically diverse agonists, raising the question of how this uncharacteristic accommodation is achieved for these GPCRs. We report the computationally derived structure of TAS2R14 with binding sites and energies for five highly diverse agonists. Remarkably, the binding pocket is the same for all five agonists. The energies derived from molecular dynamics are consistent with experiments determining signal transduction coefficients in live cells. TAS2R14 accommodates agonists through the breaking of a TMD3 H-bond instead of the prototypic strong salt bridge, a TMD1,2,7 interaction different from Class A GPCRs, and agonist-promoted TMD3 salt bridges for high affinity (which we confirmed by receptor mutagenesis). Thus, the broadly tuned TAS2Rs accommodate diverse agonists via a single (vs multiple) binding pocket through unique TM interactions for sensing disparate micro-environments.
| S-EPMC10121769 | biostudies-literature
Project description:The human gustatory cortex analyzes the chemosensory properties of tastants, particularly the quality, intensity, and affective valence, to determine whether a perceived substance should be ingested or rejected. Among previous studies, the spatial distribution of taste intensity-related activations within the human insula has been scarcely addressed. To spatially characterize a specialized or distributed nature of the cortical responses to taste intensities, a functional magnetic resonance imaging study was performed at 3 T in 44 healthy subjects where sweet and bitter tastants were administered at five increasing concentrations and cortex-based factorial and parametric analyses were performed. Two clusters in the right middle-posterior and left middle insula were found specialized for taste intensity processing, exhibiting a highly nonlinear profile across concentrations. Multiple clusters were found activated by sweet and bitter taste stimuli at most concentrations, in the anterior, middle-posterior, and inferior portion of the bilateral insula. Across these clusters, respectively, for the right and left insula, a superior-to-inferior and an anterior-to-posterior spatial gradient for high-to-low concentrations were observed for the most responsive intensity of both tastes. These findings may gather new insights regarding how the gustatory cortex is spatially organized during the perceptual processing of taste intensity for two basic tastants.
| S-EPMC6865662 | biostudies-literature
Project description:Taste is responsible for evaluating the nutritious content of food, guiding essential appetitive behaviours, preventing the ingestion of toxic substances, and helping to ensure the maintenance of a healthy diet. Sweet and bitter are two of the most salient sensory percepts for humans and other animals; sweet taste allows the identification of energy-rich nutrients whereas bitter warns against the intake of potentially noxious chemicals. In mammals, information from taste receptor cells in the tongue is transmitted through multiple neural stations to the primary gustatory cortex in the brain. Recent imaging studies have shown that sweet and bitter are represented in the primary gustatory cortex by neurons organized in a spatial map, with each taste quality encoded by distinct cortical fields. Here we demonstrate that by manipulating the brain fields representing sweet and bitter taste we directly control an animal's internal representation, sensory perception, and behavioural actions. These results substantiate the segregation of taste qualities in the cortex, expose the innate nature of appetitive and aversive taste responses, and illustrate the ability of gustatory cortex to recapitulate complex behaviours in the absence of sensory input.
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Project description:The objective of this study was to investigate the relationships between taste responsiveness and food liking in preadolescents. Model food samples of grapefruit juice (GF) and vegetable broth (VB) modified with four additions of sucrose and sodium chloride, respectively, were employed. Intensity perception for sweetness, sourness, and bitterness were measured in GF while saltiness and umami were measured in VB. The children (N = 148) also completed food choice, familiarity, stated liking and neophobia questionnaires. The test was conducted at school, with instructions provided remotely via video call. Four segments were defined differing in basic taste responsiveness. Segments and sucrose concentrations significantly affected liking for GF, while no significant effect of segments and sodium chloride concentrations occurred on liking for VB. An increasing sucrose concentration was positively associated with liking for GF only in the segment with low responsiveness to bitter and sour tastes. No significant differences across segments were found for food choice, familiarity, stated liking, and neophobia. Conclusively, relationships between taste responsiveness and liking are product and basic taste-dependent in addition to being subject-dependent. Strategies to improve acceptance by using sucrose as a suppressor for warning sensations of bitterness and sourness can be more or less effective depending on individual responsiveness to the basic tastes.
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Project description:Perceived intensities of sweetness and bitterness are correlated with one another and each is influenced by genetics. The extent to which these correlations share common genetic variation, however, remains unclear. In a mainly adolescent sample ( n = 1901, mean age 16.2 years), including 243 monozygotic (MZ) and 452 dizygotic (DZ) twin pairs, we estimated the covariance among the perceived intensities of 4 bitter compounds (6- n -propylthiouracil [PROP], sucrose octa-acetate, quinine, caffeine) and 4 sweeteners (the weighted mean ratings of glucose, fructose, neohesperidine dihydrochalcone, aspartame) with multivariate genetic modeling. The sweetness factor was moderately correlated with sucrose octa-acetate, quinine, and caffeine ( rp = 0.35-0.40). This was mainly due to a shared genetic factor ( rg = 0.46-0.51) that accounted for 17-37% of the variance in the 3 bitter compounds' ratings and 8% of the variance in general sweetness ratings. In contrast, an association between sweetness and PROP only became evident after adjusting for the TAS2R38 diplotype ( rp increased from 0.18 to 0.32) with the PROP genetic factor accounting for 6% of variance in sweetness. These genetic associations were not inflated by scale use bias, as the cross-trait correlations for both MZ and DZ twins were weak. There was also little evidence for mediation by cognition or behavioral factors. This suggests an overlap of genetic variance between perceptions of sweetness and bitterness from a variety of stimuli, which includes PROP when considering the TAS2R38 diplotype. The most likely sources of shared variation are within genes encoding post-receptor transduction mechanisms common to the various taste G protein-coupled receptors.
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Project description:Despite calls to incorporate population science into neuroimaging research, most studies recruit small, non-representative samples. Here, we examine whether sample composition influences age-related variation in global measurements of gray matter volume, thickness, and surface area. We apply sample weights to structural brain imaging data from a community-based sample of children aged 3-18 (N = 1162) to create a "weighted sample" that approximates the distribution of socioeconomic status, race/ethnicity, and sex in the U.S. Census. We compare associations between age and brain structure in this weighted sample to estimates from the original sample with no sample weights applied (i.e., unweighted). Compared to the unweighted sample, we observe earlier maturation of cortical and sub-cortical structures, and patterns of brain maturation that better reflect known developmental trajectories in the weighted sample. Our empirical demonstration of bias introduced by non-representative sampling in this neuroimaging cohort suggests that sample composition may influence understanding of fundamental neural processes.The influence of sample composition on human neuroimaging results is unknown. Here, the authors weight a large, community-based sample to better reflect the US population and describe how applying these sample weights changes conclusions about age-related variation in brain structure.
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