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Palmer RK. Why Taste Is Pharmacology. Handb Exp Pharmacol 2022; 275:1-31. [PMID: 35461405 DOI: 10.1007/164_2022_589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The chapter presents an argument supporting the view that taste, defined as the receptor-mediated signaling of taste cells and consequent sensory events, is proper subject matter for the field of pharmacology. The argument develops through a consideration of how the field of pharmacology itself is to be defined. Though its application toward the discovery and development of therapeutics is of obvious value, pharmacology nevertheless is a basic science committed to examining biological phenomena controlled by the selective interactions between chemicals - regardless of their sources or uses - and receptors. The basic science of pharmacology is founded on the theory of receptor occupancy, detailed here in the context of taste. The discussion then will turn to consideration of the measurement of human taste and how well the results agree with the predictions of receptor theory.
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2
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McCaughey SA. Variation in the gene Tas1r3 reveals complex temporal properties of mouse brainstem taste responses to sweeteners. Am J Physiol Regul Integr Comp Physiol 2021; 321:R751-R767. [PMID: 34523351 PMCID: PMC8616626 DOI: 10.1152/ajpregu.00001.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 09/08/2021] [Accepted: 09/09/2021] [Indexed: 11/22/2022]
Abstract
The gene Tas1r3 codes for the protein T1R3, which dimerizes with T1R2 to form a sweetener-binding receptor in taste cells. Tas1r3 influences sweetener preferences in mice, as shown by work with a 129.B6-Tas1r3 segregating congenic strain on a 129P3/J (129) genetic background; members of this strain vary in whether they do or do not have one copy of a donor fragment with the C57BL/6ByJ (B6) allele for Tas1r3 (B6/129 and 129/129 mice, respectively). Taste-evoked neural responses were measured in the nucleus of the solitary tract (NST), the first central gustatory relay, in B6/129 and 129/129 littermates, to examine how the activity dependent on the T1R2/T1R3 receptor is distributed across neurons and over time. Responses to sucrose were larger in B6/129 than in 129/129 mice, but only during a later, tonic response portion (>600 ms) sent to different cells than the earlier, phasic response. Similar results were found for artificial sweeteners, whose responses were best considered as complex spatiotemporal patterns. There were also group differences in burst firing of NST cells, with a significant positive correlation between bursting prevalence and sucrose response size in only the 129/129 group. The results indicate that sweetener transduction initially occurs through T1R3-independent mechanisms, after which the T1R2/T1R3 receptor initiates a separate, spatially distinct response, with the later period dominating sweet taste perceptions and driving sugar preferences. Furthermore, the current data suggest that burst firing is distributed across NST neurons nonrandomly and in a manner that may amplify weak incoming gustatory signals.
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Affiliation(s)
- Stuart A McCaughey
- Center for Medical Education, Ball State University, Muncie, Indiana
- Monell Chemical Senses Center, Philadelphia, Pennsylvania
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3
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Olvera Hernández S, Reyes Castro LA, Daher Abdi A, Mezo-González CE, Arredondo A, Zambrano E, Bolaños-Jiménez F. Adult rats from undernourished dams show sex-dependent impaired expression in taste papillae and hypothalamus of genes responsible for sweet and fat detection and signalling. Nutr Neurosci 2021; 25:2011-2022. [PMID: 33926365 DOI: 10.1080/1028415x.2021.1920678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AIM Individuals undernourished in utero or during early life are at high risk of developing obesity and metabolic disorders and show an increased preference for consuming sugary and fatty food. This study aimed at determining whether impaired taste detection and signalling in the lingual epithelium and the brain might contribute to this altered pattern of food intake. METHODS The preference for feeding fat and sweet food and the expression in circumvallate papillae and hypothalamus of genes coding for sweet and fat receptors and transducing pathways were evaluated in adult rats born to control or calorie-restricted dams. Expression in the hypothalamus and the brain's reward system of genes involved in the homeostatic and hedonic control of food intake was also determined. RESULTS Male and female undernourished animals exhibited increased expression in taste papillae and hypothalamus of T1R1, T1R2, CD36, gustducin, TRMP5 and PLC-β2 genes, all of which modulate sweet and fat detection and intracellular signalling. However, the severity of the effect was greater in females than in males. Moreover, male, but not female, undernourished rats consumed more standard and sweetened food than their control counterparts and presented increased hypothalamic AgRP and NPY mRNAs levels together with enhanced dopamine transporter and dopamine receptor D2 expression in the ventral tegmental area. CONCLUSIONS Maternal undernutrition induces sex-specific changes in food preferences and gene expression in taste papillae, hypothalamus and brain reward regions. The gene expression alterations in the male offspring are in line with their preference for consuming sugary and fatty food.
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Affiliation(s)
- Sandra Olvera Hernández
- UMR Physiologie des Adaptations Nutritionnelles, INRAE - Université de Nantes, 44096 Nantes France
| | - Luis Antonio Reyes Castro
- UMR Physiologie des Adaptations Nutritionnelles, INRAE - Université de Nantes, 44096 Nantes France.,Reproductive Biology Department, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, México
| | - Amran Daher Abdi
- UMR Physiologie des Adaptations Nutritionnelles, INRAE - Université de Nantes, 44096 Nantes France
| | | | | | - Elena Zambrano
- Reproductive Biology Department, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, México
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Lin C, Inoue M, Li X, Bosak NP, Ishiwatari Y, Tordoff MG, Beauchamp GK, Bachmanov AA, Reed DR. Genetics of mouse behavioral and peripheral neural responses to sucrose. Mamm Genome 2021; 32:51-69. [PMID: 33713179 DOI: 10.1007/s00335-021-09858-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 02/08/2021] [Indexed: 01/04/2023]
Abstract
Mice of the C57BL/6ByJ (B6) strain have higher consumption of sucrose, and stronger peripheral neural responses to it, than do mice of the 129P3/J (129) strain. To identify quantitative trait loci (QTLs) responsible for this strain difference and to evaluate the contribution of peripheral taste responsiveness to individual differences in sucrose intake, we produced an intercross (F2) of 627 mice, measured their sucrose consumption in two-bottle choice tests, recorded the electrophysiological activity of the chorda tympani nerve elicited by sucrose in a subset of F2 mice, and genotyped the mice with DNA markers distributed in every mouse chromosome. We confirmed a sucrose consumption QTL (Scon2, or Sac) on mouse chromosome (Chr) 4, harboring the Tas1r3 gene, which encodes the sweet taste receptor subunit TAS1R3 and affects both behavioral and neural responses to sucrose. For sucrose consumption, we also detected five new main-effect QTLs, Scon6 (Chr2), Scon7 (Chr5), Scon8 (Chr8), Scon3 (Chr9), and Scon9 (Chr15), and an epistatically interacting QTL pair Scon4 (Chr1) and Scon3 (Chr9). No additional QTLs for the taste nerve responses to sucrose were detected besides Scon2 (Tas1r3) on Chr4. Identification of the causal genes and variants for these sucrose consumption QTLs may point to novel mechanisms beyond peripheral taste sensitivity that could be harnessed to control obesity and diabetes.
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Affiliation(s)
- Cailu Lin
- Monell Chemical Senses Center, Philadelphia, PA, USA
| | - Masashi Inoue
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan
| | - Xia Li
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Sonora Quest Laboratories, Phoenix, AZ, USA
| | | | - Yutaka Ishiwatari
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Ajinomoto Co., Inc., Tokyo, Japan
| | | | | | - Alexander A Bachmanov
- Monell Chemical Senses Center, Philadelphia, PA, USA. .,GlaxoSmithKline, Collegeville, PA, USA.
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5
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Lin C, Tordoff MG, Li X, Bosak NP, Inoue M, Ishiwatari Y, Chen L, Beauchamp GK, Bachmanov AA, Reed DR. Genetic controls of Tas1r3-independent sucrose consumption in mice. Mamm Genome 2021; 32:70-93. [PMID: 33710367 DOI: 10.1007/s00335-021-09860-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 02/11/2021] [Indexed: 10/21/2022]
Abstract
We have previously used crosses between C57BL/6ByJ (B6) and 129P3/J (129) inbred strains to map a quantitative trait locus (QTL) on mouse chromosome (Chr) 4 that affects behavioral and neural responses to sucrose. We have named it the sucrose consumption QTL 2 (Scon2), and shown that it corresponds to the Tas1r3 gene, which encodes a sweet taste receptor subunit TAS1R3. To discover other sucrose consumption QTLs, we have intercrossed B6 inbred and 129.B6-Tas1r3 congenic mice to produce F2 hybrids, in which Scon2 (Tas1r3) does not segregate, and hence does not contribute to phenotypical variation. Chromosome mapping using this F2 intercross identified two main-effect QTLs, Scon3 (Chr9) and Scon10 (Chr14), and an epistatically interacting QTL pair Scon3 (Chr9)-Scon4 (Chr1). Using serial backcrosses, congenic and consomic strains, we conducted high-resolution mapping of Scon3 and Scon4 and analyzed their epistatic interactions. We used mice with different Scon3 or Scon4 genotypes to understand whether these two QTLs influence sucrose intake via gustatory or postoral mechanisms. These studies found no evidence for involvement of the taste mechanisms, but suggested involvement of energy metabolism. Mice with the B6 Scon4 genotype drank less sucrose in two-bottle tests, and also had a higher respiratory exchange ratio and lower energy expenditure under basal conditions (when they had only chow and water available). Our results provide evidence that Scon3 and Scon4 influence mouse-to-mouse variation in sucrose intake and that both likely act through a common postoral mechanism.
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Affiliation(s)
- Cailu Lin
- Monell Chemical Senses Center, Philadelphia, PA, USA
| | | | - Xia Li
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Sonora Quest Laboratories, Phoenix, AZ, USA
| | | | - Masashi Inoue
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan
| | - Yutaka Ishiwatari
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Ajinomoto Co. Inc, Tokyo, Japan
| | - Longhui Chen
- Monell Chemical Senses Center, Philadelphia, PA, USA.,Tannbach Capital, Hong Kong, China
| | | | - Alexander A Bachmanov
- Monell Chemical Senses Center, Philadelphia, PA, USA.,GlaxoSmithKline, Collegeville, PA, USA
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6
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Felgenhauer JL, Brune JE, Long ME, Manicone AM, Chang MY, Brabb TL, Altemeier WA, Frevert CW. Evaluation of Nutritional Gel Supplementation in C57BL/6J Mice Infected with Mouse-Adapted Influenza A/PR/8/34 Virus. Comp Med 2020; 70:471-486. [PMID: 33323164 PMCID: PMC7754200 DOI: 10.30802/aalas-cm-20-990138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 11/05/2019] [Accepted: 09/04/2020] [Indexed: 12/11/2022]
Abstract
Mice are a common animal model for the study of influenza virus A (IAV). IAV infection causes weight loss due to anorexia and dehydration, which can result in early removal of mice from a study when they reach a humane endpoint. To reduce the number of mice prematurely removed from an experiment, we assessed nutritional gel (NG) supplementation as a support strategy for mice infected with mouse-adapted Influenza A/Puerto Rico/8/34 (A/PR/8/34; H1N1) virus. We hypothesized that, compared with the standard of care (SOC), supplementation with NG would reduce weight loss and increase survival in mice infected with IAV without impacting the initial immune response to infection. To assess the effects of NG, male and female C57BL/6J mice were infected with IAV at low, intermediate, or high doses. When compared with SOC, mice given NG showed a significant decrease in the maximal percent weight loss at all viral doses in males and at the intermediate dose for females. Mice supplemented with NG had no deaths for either sex at the intermediate dose and a significant increase in survival in males at the high viral dose. Supplementation with NG did not alter the viral titer or the pulmonary recruitment of immune cells as measured by cell counts and flow cytometry of cells recovered in bronchoalveolar lavage (BAL) fluid in either sex. However, mice given NG had a significant reduction in IL6 and TNFα in BAL fluid and no significant differences in CCL2, IL4, IL10, CXCL1, CXCL2, and VEGF. The results of this study show that as compared with infected SOC mice, infected mice supplemented with NG have reduced weight loss and increased survival, with males showing a greater benefit. These results suggest that NG should be considered as a support strategy and indicate that sex is an important biologic variable in mice infected with IAV.
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Key Words
- iav, influenza a virus
- soc, standard of care
- ng, nutritional gel
- eud50, euthanasia dose 50
- ld50, lethal-dose 50
- pfu, plaque forming unit
- dpi, days post infection
- il6, interleukin 6
- sem, standard error of mean
- ns, no significance
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Affiliation(s)
- Jessica L Felgenhauer
- Department of Comparative Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Jourdan E Brune
- Department of Comparative Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Matthew E Long
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Anne M Manicone
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Mary Y Chang
- Department of Comparative Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Thea L Brabb
- Department of Comparative Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - William A Altemeier
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington
| | - Charles W Frevert
- Department of Comparative Medicine, University of Washington, Seattle, Washington; Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Washington, Seattle, Washington; Center for Lung Biology, University of Washington at South Lake Union, Seattle, Washington;,
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An alternative pathway for sweet sensation: possible mechanisms and physiological relevance. Pflugers Arch 2020; 472:1667-1691. [PMID: 33030576 DOI: 10.1007/s00424-020-02467-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/14/2020] [Accepted: 09/23/2020] [Indexed: 12/12/2022]
Abstract
Sweet substances are detected by taste-bud cells upon binding to the sweet-taste receptor, a T1R2/T1R3 heterodimeric G protein-coupled receptor. In addition, experiments with mouse models lacking the sweet-taste receptor or its downstream signaling components led to the proposal of a parallel "alternative pathway" that may serve as metabolic sensor and energy regulator. Indeed, these mice showed residual nerve responses and behavioral attraction to sugars and oligosaccharides but not to artificial sweeteners. In analogy to pancreatic β cells, such alternative mechanism, to sense glucose in sweet-sensitive taste cells, might involve glucose transporters and KATP channels. Their activation may induce depolarization-dependent Ca2+ signals and release of GLP-1, which binds to its receptors on intragemmal nerve fibers. Via unknown neuronal and/or endocrine mechanisms, this pathway may contribute to both, behavioral attraction and/or induction of cephalic-phase insulin release upon oral sweet stimulation. Here, we critically review the evidence for a parallel sweet-sensitive pathway, involved signaling mechanisms, neural processing, interactions with endocrine hormonal mechanisms, and its sensitivity to different stimuli. Finally, we propose its physiological role in detecting the energy content of food and preparing for digestion.
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8
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Allelic variation of the Tas1r3 taste receptor gene affects sweet taste responsiveness and metabolism of glucose in F1 mouse hybrids. PLoS One 2020; 15:e0235913. [PMID: 32673349 PMCID: PMC7365461 DOI: 10.1371/journal.pone.0235913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 06/25/2020] [Indexed: 11/25/2022] Open
Abstract
In mammals, inter- and intraspecies differences in consumption of sweeteners largely depend on allelic variation of the Tas1r3 gene (locus Sac) encoding the T1R3 protein, a sweet taste receptor subunit. To assess the influence of Tas1r3 polymorphisms on feeding behavior and metabolism, we examined the phenotype of F1 male hybrids obtained from crosses between the following inbred mouse strains: females from 129SvPasCrl (129S2) bearing the recessive Tas1r3 allele and males from either C57BL/6J (B6), carrying the dominant allele, or the Tas1r3-gene knockout strain C57BL/6J-Tas1r3tm1Rfm (B6-Tas1r3-/-). The hybrids 129S2B6F1 and 129S2B6-Tas1r3-/-F1 had identical background genotypes and different sets of Tas1r3 alleles. The effect of Tas1r3 hemizygosity was analyzed by comparing the parental strain B6 (Tas1r3 homozygote) and hemizygous F1 hybrids B6 × B6-Tas1r3-/-. Data showed that, in 129S2B6-Tas1r3-/-F1 hybrids, the reduction of glucose tolerance, along with lower consumption of and lower preference for sweeteners during the initial licking responses, is due to expression of the recessive Tas1r3 allele. Hemizygosity of Tas1r3 did not influence these behavioral and metabolic traits. However, the loss of the functional Tas1r3 allele was associated with a small decline in the long-term intake and preference for sweeteners and reduction of plasma insulin and body, liver, and fat mass.
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9
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Bacharach SZ, Calu DJ. Stability of individual differences in sucralose taste preference. PLoS One 2019; 14:e0216431. [PMID: 31086418 PMCID: PMC6516736 DOI: 10.1371/journal.pone.0216431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 04/21/2019] [Indexed: 11/19/2022] Open
Abstract
Outbred rats display variable preferences for bittersweet solutions, expressed as preference or avoidance of high concentrations of artificial sweeteners over water. This may reflect individual differences in appetitive/aversive conflict processing that may have predictive validity for disorders of motivation. Here we use a homecage two-bottle choice procedure to examine the test/retest stability and between-tastant consistency in sucralose preference to determine the reliability of bittersweet taste preference. Sucralose is a non-caloric artificial sweetener that is preferred by some rats and avoided by others. We sought to determine whether sucralose preference is consistent with preference of sucrose/quinine solutions that have known sweet and bitter taste qualities, respectively. We give fluid restricted rats 45-minutes homecage access to water and ascending concentrations of sucralose (SUCRA; 0.0025-10mM) or a compound solution of sucrose (116mM) + quinine (0.002-2mM) (SQ). We use a within-subject counterbalanced design (SUCRA or SQ testing) to determine preference of each bittersweet solution relative to water. We observed individual variability in preference for SUCRA and SQ, such that some rats preferred bittersweet solutions over water (preferring) while other rats preferred water over bittersweet solutions (avoiding). Within tastant, this preference remained stable across repeated testing. Between solutions, SUCRA preference scores correlated with SQ scores, suggesting consistent taste conflict processing for both bittersweet solutions. Population level analyses confirmed that preference generalizes across bittersweet solutions, and that rats' preferences for bittersweet solutions relative to water are stable over time. The test/retest and between-tastant reliability of this taste conflict screening procedure support the potential utility of this model for exploring individual variability in appetitive/aversive conflict processes mediating motivated behavior.
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Affiliation(s)
- Sam Z. Bacharach
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Donna J. Calu
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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Abstract
The study of taste has been guided throughout much of its history by the conceptual framework of psychophysics, where the focus was on quantification of the subjective experience of the taste sensations. By the mid-20th century, data from physiologic studies had accumulated sufficiently to assemble a model for the function of receptors that must mediate the initial stimulus of tastant molecules in contact with the tongue. But the study of taste as a receptor-mediated event did not gain momentum until decades later when the actual receptor proteins and attendant signaling mechanisms were identified and localized to the highly specialized taste-responsive cells of the tongue. With those discoveries a new opportunity to examine taste as a function of receptor activity has come into focus. Pharmacology is the science designed specifically for the experimental interrogation and quantitative characterization of receptor function at all levels of inquiry from molecules to behavior. This review covers the history of some of the major concepts that have shaped thinking and experimental approaches to taste, the seminal discoveries that have led to elucidation of receptors for taste, and how applying principles of receptor pharmacology can enhance understanding of the mechanisms of taste physiology and perception.
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Affiliation(s)
- R Kyle Palmer
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
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11
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Schier LA, Spector AC. The Functional and Neurobiological Properties of Bad Taste. Physiol Rev 2019; 99:605-663. [PMID: 30475657 PMCID: PMC6442928 DOI: 10.1152/physrev.00044.2017] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 05/18/2018] [Accepted: 06/30/2018] [Indexed: 12/12/2022] Open
Abstract
The gustatory system serves as a critical line of defense against ingesting harmful substances. Technological advances have fostered the characterization of peripheral receptors and have created opportunities for more selective manipulations of the nervous system, yet the neurobiological mechanisms underlying taste-based avoidance and aversion remain poorly understood. One conceptual obstacle stems from a lack of recognition that taste signals subserve several behavioral and physiological functions which likely engage partially segregated neural circuits. Moreover, although the gustatory system evolved to respond expediently to broad classes of biologically relevant chemicals, innate repertoires are often not in register with the actual consequences of a food. The mammalian brain exhibits tremendous flexibility; responses to taste can be modified in a specific manner according to bodily needs and the learned consequences of ingestion. Therefore, experimental strategies that distinguish between the functional properties of various taste-guided behaviors and link them to specific neural circuits need to be applied. Given the close relationship between the gustatory and visceroceptive systems, a full reckoning of the neural architecture of bad taste requires an understanding of how these respective sensory signals are integrated in the brain.
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Affiliation(s)
- Lindsey A Schier
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Alan C Spector
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
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12
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Murovets VO, Lukina EA, Zolotarev VA. The Effect of Tas1r3 Gene Polymorphism on Preference and Consumption of Sucrose and Low-Calorie Sweeteners in Interstrain Hybrid Mice of the First Filial Generation. J EVOL BIOCHEM PHYS+ 2018. [DOI: 10.1134/s0022093018030079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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McCaughey SA. Characterization of mouse chorda tympani responses evoked by stimulation of anterior or posterior fungiform taste papillae. Neurosci Res 2018; 141:43-51. [PMID: 29580888 DOI: 10.1016/j.neures.2018.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 02/18/2018] [Accepted: 03/22/2018] [Indexed: 11/30/2022]
Abstract
Different gustatory papilla types vary in their locations on the tongue. Distinctions have often made between types, but variation within fungiform papillae has seldom been explored. Here, regional differences in fungiform papillae were investigated by flowing solutions selectively over either an anterior fungiform (AF, tongue tip) or a posterior fungiform (PF, middle third) region as taste-evoked activity was measured in the chorda tympani nerve of C57BL/6J (B6) mice. Significantly larger responses were evoked by NaCl applied to the AF than PF region, and the ENaC blocker amiloride reduced the NaCl response size only for the former. Umami synergy, based on co-presenting MSG and IMP, was larger for the AF than PF region. The regions did not differ in response size to sour chemicals, but responses to l-lysine, l-arginine, sucrose, and tetrasodium pyrophosphate were larger for the AF than PF region. Thus, fungiform papillae on the tongue tip differed from those found further back in their transduction mechanisms for salty and umami compounds. Gustatory sensitivity also showed regional variation, albeit with a complex relationship to palatability and taste quality. Overall, the data support a regional organization for the mouse tongue, with different functional zones for the anterior, middle, and posterior thirds.
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Affiliation(s)
- Stuart A McCaughey
- Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, United States; Center for Medical Education, Ball State University, Muncie, IN, 47306, United States.
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14
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Blonde GD, Travers SP, Spector AC. Taste sensitivity to a mixture of monosodium glutamate and inosine 5'-monophosphate by mice lacking both subunits of the T1R1+T1R3 amino acid receptor. Am J Physiol Regul Integr Comp Physiol 2018; 314:R802-R810. [PMID: 29443544 DOI: 10.1152/ajpregu.00352.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The taste of l-glutamate and its synergism with 5'-ribonucleotides is thought to be primarily mediated through the T1R1+T1R3 heterodimer in some mammals, including rodents and humans. While knockout (KO) mice lacking either receptor subunit show impaired sensitivity to a range of monosodium glutamate (MSG) concentrations mixed with 2.5 mM inosine 5'-monophosphate (IMP) in amiloride, wild-type (WT) controls can detect this IMP concentration, hindering direct comparison between genotypes. Moreover, some residual sensitivity persists in the KO group, suggesting that the remaining subunit could maintain a limited degree of function. Here, C57BL/6J, 129X1/SvJ, and T1R1+T1R3 double KO mice ( n = 16 each to start the experiment) were trained in a two-response operant task in gustometers and then tested for their ability to discriminate 100 µM amiloride from MSG (starting with 0.6 M) and IMP (starting with 2.5 mM) in amiloride (MSG+I+A). Testing continued with successive dilutions of both MSG and IMP (in amiloride). The two WT strains were similarly sensitive to MSG+I+A ( P > 0.8). KO mice, however, were significantly impaired relative to either WT strain ( P < 0.01), although they were able to detect the highest concentrations. Thus, normal detectability of MSG+I+A requires an intact T1R1+T1R3 receptor, without regard for allelic variation in the T1R3 gene between the WT strains. Nevertheless, residual sensitivity by the T1R1+T1R3 KO mice demonstrates that a T1R-independent mechanism can contribute to the detectability of high concentrations of this prototypical umami compound stimulus.
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Affiliation(s)
- Ginger D Blonde
- Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Susan P Travers
- Division of Biosciences, College of Dentistry, Ohio State University , Columbus, Ohio
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
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15
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Eddy MC, Eschle BK, Delay ER. Comparison of the Tastes of L-Alanine and Monosodium Glutamate in C57BL/6J Wild Type and T1r3 Knockout Mice. Chem Senses 2017; 42:563-573. [PMID: 28605507 DOI: 10.1093/chemse/bjx037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2017] [Indexed: 11/12/2022] Open
Abstract
Previous research showed that L-alanine and monosodium L-glutamate elicit similar taste sensations in rats. This study reports the results of behavioral experiments designed to compare the taste capacity of C57BL/6J wild type and T1r3- mice for these 2 amino acids. In conditioned taste aversion (CTA) experiments, wild-type mice exhibited greater sensitivity than knockout mice for both L-amino acids, although knockout mice were clearly able to detect both amino acids at 50 mM and higher concentrations. Generalization of CTA between L-alanine and L-glutamate was bidirectionally equivalent for both mouse genotypes, indicating that both substances elicited similar tastes in both genotypes. This was verified by the discrimination experiments in which both mouse genotypes performed at or near chance levels at 75 and 150 mM. Above 150 mM, discrimination performance improved, suggesting the taste qualities of the 2 L-amino acids are not identical. No differences between knockout and wild-type mice in discrimination ability were detected. These results indicate that while the T1r3 receptor is important for tasting L-alanine and L-glutamate, other receptors are also important for tasting these amino acids.
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Affiliation(s)
- Meghan C Eddy
- Department of Biology and Vermont Chemical Senses Group, University of Vermont,109 Carrigan Drive, Burlington, VT 05405,USA
| | - Benjamin K Eschle
- Department of Biology and Vermont Chemical Senses Group, University of Vermont,109 Carrigan Drive, Burlington, VT 05405,USA
| | - Eugene R Delay
- Department of Biology and Vermont Chemical Senses Group, University of Vermont,109 Carrigan Drive, Burlington, VT 05405,USA
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16
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Smith KR, Spector AC. Detection of maltodextrin and its discrimination from sucrose are independent of the T1R2 + T1R3 heterodimer. Am J Physiol Regul Integr Comp Physiol 2017; 313:R450-R462. [PMID: 28768658 DOI: 10.1152/ajpregu.00049.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/11/2017] [Accepted: 07/24/2017] [Indexed: 12/25/2022]
Abstract
Maltodextrins, such as Maltrin and Polycose, are glucose polymer mixtures of varying chain lengths that are palatable to rodents. Although glucose and other sugars activate the T1R2 + T1R3 "sweet" taste receptor, recent evidence from T1R2- or T1R3-knockout (KO) mice suggests that maltodextrins, despite their glucose polymer composition, activate a separate receptor mechanism to generate a taste percept qualitatively distinguishable from that of sweeteners. However, explicit discrimination of maltodextrins from prototypical sweeteners has not yet been psychophysically tested in any murine model. Therefore, mice lacking T1R2 + T1R3 and wild-type controls were tested in a two-response taste discrimination task to determine whether maltodextrins are 1) detectable when both receptor subunits are absent and 2) perceptually distinct from that of sucrose irrespective of viscosity, intensity, and hedonics. Most KO mice displayed similar Polycose sensitivity as controls. However, some KO mice were only sensitive to the higher Polycose concentrations, implicating potential allelic variation in the putative polysaccharide receptor or downstream pathways unmasked by the absence of T1R2 + T1R3. Varied Maltrin and sucrose concentrations of approximately matched viscosities were then presented to render the oral somatosensory features, intensity, and hedonic value of the solutions irrelevant. Although both genotypes competently discriminated Maltrin from sucrose, performance was apparently driven by the different orosensory percepts of the two stimuli in control mice and the presence of a Maltrin but not sucrose orosensory cue in KO mice. These data support the proposed presence of an orosensory receptor mechanism that gives rise to a qualitatively distinguishable sensation from that of sucrose.
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Affiliation(s)
- Kimberly R Smith
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida
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17
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Guerra ML, Kalwat MA, McGlynn K, Cobb MH. Sucralose activates an ERK1/2-ribosomal protein S6 signaling axis. FEBS Open Bio 2017; 7:174-186. [PMID: 28174684 PMCID: PMC5292669 DOI: 10.1002/2211-5463.12172] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/13/2016] [Accepted: 11/28/2016] [Indexed: 12/20/2022] Open
Abstract
The sweetener sucralose can signal through its GPCR receptor to induce insulin secretion from pancreatic β cells, but the downstream signaling pathways involved are not well‐understood. Here we measure responses to sucralose, glucagon‐like peptide 1, and amino acids in MIN6 β cells. Our data suggest a signaling axis, whereby sucralose induces calcium and cAMP, activation of ERK1/2, and site‐specific phosphorylation of ribosomal protein S6. Interestingly, sucralose acted independently of mTORC1 or ribosomal S6 kinase (RSK). These results suggest that sweeteners like sucralose can influence β‐cell responses to secretagogues like glucose through metabolic as well as GPCR‐mediated pathways. Future investigation of novel sweet taste receptor signaling pathways in β cells will have implications for diabetes and other emergent fields involving these receptors.
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Affiliation(s)
- Marcy L Guerra
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA; Present address: Stem Synergy Therapeutics Nashville TN USA
| | - Michael A Kalwat
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
| | - Kathleen McGlynn
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
| | - Melanie H Cobb
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
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18
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Behavioral evidence that select carbohydrate stimuli activate T1R-independent receptor mechanisms. Appetite 2016; 122:26-31. [PMID: 28034739 DOI: 10.1016/j.appet.2016.12.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 12/22/2016] [Accepted: 12/22/2016] [Indexed: 01/21/2023]
Abstract
Three decades ago Tony Sclafani proposed the existence of a polysaccharide taste quality that was distinguishable from the taste generated by common sweeteners and that it was mediated by a separate receptor mechanism. Since that time, evidence has accumulated, including psychophysical studies conducted in our laboratory, buttressing this hypothesis. The use of knockout (KO) mice that lack functional T1R2 + T1R3 heterodimers, the principal taste receptor for sugars and other sweeteners, have been especially informative in this regard. Such KO mice display severely diminished electrophysiological and behavioral responsiveness to sugars, artificial sweeteners, and some amino acids, yet display only slightly impaired concentration-dependent responsiveness to a representative polysaccharide, Polycose. Moreover, although results from gene deletion experiments in the literature provide strong support for the primacy of the T1R2 + T1R3 heterodimer in the taste transduction of sugars and other sweeteners, there is also growing evidence suggesting that there may be T1R-independent receptor mechanism(s) activated by select sugars, especially glucose. The output of these latter receptor mechanisms appears to be channeled into brain circuits subserving various taste functions such as cephalic phase responses and ingestive motivation. This paper highlights some of the findings from our laboratory and others that lend support for this view, while emphasizing the importance of considering the multidimensional nature of taste function in the interpretation of outcomes from experiments involving manipulations of the gustatory system.
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19
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Robles CF, Johnson AW. Disruptions in effort-based decision-making and consummatory behavior following antagonism of the dopamine D2 receptor. Behav Brain Res 2016; 320:431-439. [PMID: 27984049 DOI: 10.1016/j.bbr.2016.10.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 01/22/2023]
Abstract
Dopamine is known to influence motivational processes, however the precise role of this neurotransmitter remains a contentious issue. In the current study we sought to further characterize dopamine signaling in reward-based decision-making and consummatory behavior in mice, via lateral ventricle infusion of the dopamine D2 receptor antagonist eticlopride. In Experiment 1, we examined effort-based decision-making, in which mice had a choice between one lever, where a single response led to the delivery of a low value reward (2% sucrose); and a second lever, which led to a higher value reward (20% sucrose) that gradually required more effort to obtain. As the response schedule for the high value reward became more strict, low dose (4μg in 0.5μl) central infusions of eticlopride biased preference away from the high value reward, and toward the lever that led to the low value reward. Similarly, a higher dose of eticlopride (8μg in 0.5μl) also disrupted choice responding for the high value reward, however it did so by increasing omissions. In Experiment 2, we assessed the effects of eticlopride on consumption of 20% sucrose. The antagonist led to a dose-dependent reduction in intake, and through an analysis of licking microstructure, it was revealed that this in part reflected a reduction in the motivation to engage in consummatory behavior, rather than alterations in the evaluation of the reward. These results suggest that disruptions in D2 receptor signaling reduce the willingness to engage in effortful operant responding and consumption of a desirable outcome.
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Affiliation(s)
- Cindee F Robles
- Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, United States
| | - Alexander W Johnson
- Department of Psychology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, United States.
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20
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Murray S, Tulloch A, Criscitelli K, Avena NM. Recent studies of the effects of sugars on brain systems involved in energy balance and reward: Relevance to low calorie sweeteners. Physiol Behav 2016; 164:504-508. [PMID: 27068180 PMCID: PMC5003688 DOI: 10.1016/j.physbeh.2016.04.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 04/02/2016] [Accepted: 04/04/2016] [Indexed: 12/29/2022]
Abstract
The alarmingly high rates of overweight and obesity pose a serious global health threat. Numerous factors can result in weight gain, one of which is excess consumption of caloric sweeteners. In an effort to aid weight loss efforts, many people have switched from caloric sweeteners to low calorie sweeteners, which provide sweet taste without the accompanying calories. In this review, we present an overview of the animal literature produced in the last 5years highlighting the effects of sugar consumption on neural pathways involved in energy balance regulation and reward processing. We also examine the latest evidence that is beginning to elucidate the effects of low calorie sweeteners on these neural pathways, as well as how homeostatic and hedonic systems interact in response to, or to influence, sugar consumption.
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Affiliation(s)
- Susan Murray
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10025, United States
| | - Alastair Tulloch
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10025, United States
| | - Kristen Criscitelli
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10025, United States
| | - Nicole M Avena
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10025, United States
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21
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Waksmonski JC, Koppel K. Variation in human sweet taste receptor may result in different levels of sweet intensity variability between sweet stimuli. Int J Food Sci Technol 2016. [DOI: 10.1111/ijfs.13174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- James C. Waksmonski
- The Sensory Analysis Center; Kansas State University; 1310 Research Park Dr Manhattan KS 66502 USA
| | - Kadri Koppel
- The Sensory Analysis Center; Kansas State University; 1310 Research Park Dr Manhattan KS 66502 USA
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22
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Bachmanov AA, Bosak NP, Glendinning JI, Inoue M, Li X, Manita S, McCaughey SA, Murata Y, Reed DR, Tordoff MG, Beauchamp GK. Genetics of Amino Acid Taste and Appetite. Adv Nutr 2016; 7:806S-22S. [PMID: 27422518 PMCID: PMC4942865 DOI: 10.3945/an.115.011270] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The consumption of amino acids by animals is controlled by both oral and postoral mechanisms. We used a genetic approach to investigate these mechanisms. Our studies have shown that inbred mouse strains differ in voluntary amino acid consumption, and these differences depend on sensory and nutritive properties of amino acids. Like humans, mice perceive some amino acids as having a sweet (sucrose-like) taste and others as having an umami (glutamate-like) taste. Mouse strain differences in the consumption of some sweet-tasting amino acids (d-phenylalanine, d-tryptophan, and l-proline) are associated with polymorphisms of a taste receptor, type 1, member 3 gene (Tas1r3), and involve differential peripheral taste responsiveness. Strain differences in the consumption of some other sweet-tasting amino acids (glycine, l-alanine, l-glutamine, and l-threonine) do not depend on Tas1r3 polymorphisms and so must be due to allelic variation in other, as yet unknown, genes involved in sweet taste. Strain differences in the consumption of l-glutamate may depend on postingestive rather than taste mechanisms. Thus, genes and physiologic mechanisms responsible for strain differences in the consumption of each amino acid depend on the nature of its taste and postingestive properties. Overall, mouse strain differences in amino acid taste and appetite have a complex genetic architecture. In addition to the Tas1r3 gene, these differences depend on other genes likely involved in determining the taste and postingestive effects of amino acids. The identification of these genes may lead to the discovery of novel mechanisms that regulate amino acid taste and appetite.
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Affiliation(s)
| | | | - John I Glendinning
- Department of Biology, Barnard College, Columbia University, New York, NY
| | - Masashi Inoue
- Monell Chemical Senses Center, Philadelphia, PA; Laboratory of Cellular Neurobiology, School of Life Sciences, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan
| | - Xia Li
- Monell Chemical Senses Center, Philadelphia, PA
| | - Satoshi Manita
- Monell Chemical Senses Center, Philadelphia, PA; Laboratory of Cellular Neurobiology, School of Life Sciences, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan
| | | | - Yuko Murata
- Monell Chemical Senses Center, Philadelphia, PA; National Research Institute of Fisheries Science, Yokohama, Japan; and
| | | | | | - Gary K Beauchamp
- Monell Chemical Senses Center, Philadelphia, PA; Department of Psychology and School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
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23
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Roebber JK, Izenwasser S, Chaudhari N. Cocaine decreases saccharin preference without altering sweet taste sensitivity. Pharmacol Biochem Behav 2015; 133:18-24. [PMID: 25812471 PMCID: PMC4430401 DOI: 10.1016/j.pbb.2015.03.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 03/10/2015] [Accepted: 03/16/2015] [Indexed: 10/23/2022]
Abstract
In rodents, saccharin consumption is suppressed when the sweet taste stimulus is paired with moderate doses of cocaine. Several hypotheses have been used to explain the seemingly contradictory effect of decreased consumption of a normally preferred substance following a highly rewarding drug. A common theme across these hypotheses is that saccharin is interpreted as less rewarding after cocaine pairing. We considered the alternative possibility that suppression is caused not by a change in reward circuitry, but rather by a change in taste detection, for instance by altering the afferent taste response and decreasing sensitivity to sweet taste stimuli. To evaluate this possibility, we measured saccharin taste sensitivity of mice before and after a standard cocaine-pairing paradigm. We measured taste sensitivity using a brief-access lickometer equipped with multiple concentrations of saccharin solution and established concentration-response curves before and after saccharin-cocaine pairing. Our results indicate that the EC50 for saccharin was unaltered following pairing. Instead, the avidity of licking saccharin, an indicator of motivation, was depressed. Latency to first-lick, a negative indicator of motivation, was also dramatically increased. Thus, our findings are consistent with the interpretation that saccharin-cocaine pairing results in devaluing of the sweet taste reward.
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Affiliation(s)
- Jennifer K Roebber
- Graduate Program in Neurosciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Sari Izenwasser
- Graduate Program in Neurosciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Nirupa Chaudhari
- Graduate Program in Neurosciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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24
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McCool BA, Chappell AM. Chronic intermittent ethanol inhalation increases ethanol self-administration in both C57BL/6J and DBA/2J mice. Alcohol 2015; 49:111-20. [PMID: 25659650 DOI: 10.1016/j.alcohol.2015.01.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/30/2014] [Accepted: 01/06/2015] [Indexed: 02/01/2023]
Abstract
Inbred mouse strains provide significant opportunities to understand the genetic mechanisms controlling ethanol-directed behaviors and neurobiology. They have been specifically employed to understand cellular mechanisms contributing to ethanol consumption, acute intoxication, and sensitivities to chronic effects. However, limited ethanol consumption by some strains has restricted our understanding of clinically relevant endpoints such as dependence-related ethanol intake. Previous work with a novel tastant-substitution procedure using monosodium glutamate (MSG or umami flavor) has shown that the procedure greatly enhances ethanol consumption by mouse strains that express limited drinking phenotypes using other methods. In the current study, we employ this MSG-substitution procedure to examine how ethanol dependence, induced with passive vapor inhalation, modifies ethanol drinking in C57BL/6J and DBA/2J mice. These strains represent 'high' and 'low' drinking phenotypes, respectively. We found that the MSG substitution greatly facilitates ethanol drinking in both strains, and likewise, ethanol dependence increased ethanol consumption regardless of strain. However, DBA/2J mice exhibited greater sensitivity dependence-enhanced drinking, as represented by consumption behaviors directed at lower ethanol concentrations and relative to baseline intake levels. DBA/2J mice also exhibited significant withdrawal-associated anxiety-like behavior while C57BL/6J mice did not. These findings suggest that the MSG-substitution procedure can be employed to examine dependence-enhanced ethanol consumption across a range of drinking phenotypes, and that C57BL/6J and DBA/2J mice may represent unique neurobehavioral pathways for developing dependence-enhanced ethanol consumption.
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25
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Duca FA, Swartz TD, Covasa M. Effect of diet on preference and intake of sucrose in obese prone and resistant rats. PLoS One 2014; 9:e111232. [PMID: 25329959 PMCID: PMC4203826 DOI: 10.1371/journal.pone.0111232] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/29/2014] [Indexed: 01/03/2023] Open
Abstract
Increased orosensory stimulation from palatable diets and decreased feedback from gut signals have been proposed as contributing factors to obesity development. Whether altered taste functions associated with obesity are common traits or acquired deficits to environmental factors, such as a high-energy (HE)-diet, however, is not clear. To address this, we examined preference and sensitivity of increasing concentrations of sucrose solutions in rats prone (OP) and resistant (OR) to obesity during chow and HE feeding and measured lingual gene expression of the sweet taste receptor T1R3. When chow-fed, OP rats exhibited reduced preference and acceptance of dilute sucrose solutions, sham-fed less sucrose compared to OR rats, and had reduced lingual T1R3 gene expression. HE-feeding abrogated differences in sucrose preference and intake and lingual T1R3 expression between phenotypes. Despite similar sucrose intakes however, OP rats consumed significantly more total calories during 48-h two-bottle testing compared to OR rats. The results demonstrate that OP rats have an innate deficit for sweet taste detection, as illustrated by a reduction in sensitivity to sweets and reduced T1R3 gene expression; however their hyperphagia and subsequent obesity during HE-feeding is most likely not due to altered consumption of sweets.
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Affiliation(s)
- Frank A. Duca
- UMR 1319 MICALIS, Institut National de la Recherche Agronomique, Centre de Recherche de Jouy-, Jouy-en-Josas, France
- AgroParisTech, Jouy-en-Josas, France
| | - Timothy D. Swartz
- UMR 1319 MICALIS, Institut National de la Recherche Agronomique, Centre de Recherche de Jouy-, Jouy-en-Josas, France
- AgroParisTech, Jouy-en-Josas, France
| | - Mihai Covasa
- UMR 1319 MICALIS, Institut National de la Recherche Agronomique, Centre de Recherche de Jouy-, Jouy-en-Josas, France
- AgroParisTech, Jouy-en-Josas, France
- Department of Basic Medical Sciences, College of Osteopathic Medicine, Western University of Health Sciences, Pomona, California, United States of America
- Department of Human Health and Development, University of Suceava, Suceava, Romania
- * E-mail:
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26
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Niimi K, Takahashi E. Differences in saccharin preference and genetic alterations of the Tas1r3 gene among senescence-accelerated mouse strains and their parental AKR/J strain. Physiol Behav 2014; 130:108-12. [PMID: 24726396 DOI: 10.1016/j.physbeh.2014.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Revised: 03/14/2014] [Accepted: 04/02/2014] [Indexed: 10/25/2022]
Abstract
The senescence-accelerated mouse (SAM) is used as an animal model of senescence acceleration and age-associated disorders. SAM is derived from unexpected crosses between the AKR/J and unknown mouse strains. There are nine senescence-prone (SAMP) strains and three senescence-resistant (SAMR) strains. Although SAMP strains exhibit strain-specific and age-related pathological changes, the genes responsible for the pathologic changes in SAMP strains have not been comprehensively identified. In the present study, we evaluated sweet taste perception using the two-bottle test. We compared genotypes of the taste related gene, Tas1r3, using SAM strains and the parental AKR/J strain. The two-bottle test revealed that SAMR1 (R1), SAMP6 (P6), SAMP8 (P8), and SAMP10 (P10) mice were saccharin-preferring strains, whereas AKR/J did not prefer saccharin. All genotypes of the R1, P6, P8, and P10 strains at the polymorphic sites in Tas1r3, which is known to influence saccharin preference, were identical to those of C57BL6/J, a well-known saccharin-preferring strain, and were completely different from those of the parental AKR/J strain. These genetic alterations in SAM strains appear to arise from an unknown strain that is thought to have been crossed with AKR/J initially.
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Affiliation(s)
- Kimie Niimi
- Support Unit for Animal Resources Development, Research Resources Center, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Eiki Takahashi
- Support Unit for Animal Resources Development, Research Resources Center, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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27
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Bachmanov AA, Bosak NP, Lin C, Matsumoto I, Ohmoto M, Reed DR, Nelson TM. Genetics of taste receptors. Curr Pharm Des 2014; 20:2669-83. [PMID: 23886383 PMCID: PMC4764331 DOI: 10.2174/13816128113199990566] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 07/24/2013] [Indexed: 12/19/2022]
Abstract
Taste receptors function as one of the interfaces between internal and external milieus. Taste receptors for sweet and umami (T1R [taste receptor, type 1]), bitter (T2R [taste receptor, type 2]), and salty (ENaC [epithelial sodium channel]) have been discovered in the recent years, but transduction mechanisms of sour taste and ENaC-independent salt taste are still poorly understood. In addition to these five main taste qualities, the taste system detects such noncanonical "tastes" as water, fat, and complex carbohydrates, but their reception mechanisms require further research. Variations in taste receptor genes between and within vertebrate species contribute to individual and species differences in taste-related behaviors. These variations are shaped by evolutionary forces and reflect species adaptations to their chemical environments and feeding ecology. Principles of drug discovery can be applied to taste receptors as targets in order to develop novel taste compounds to satisfy demand in better artificial sweeteners, enhancers of sugar and sodium taste, and blockers of bitterness of food ingredients and oral medications.
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28
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McCaughey SA, Glendinning JI. Experience with sugar modifies behavioral but not taste-evoked medullary responses to sweeteners in mice. Chem Senses 2013; 38:793-802. [PMID: 24084168 DOI: 10.1093/chemse/bjt046] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dietary exposure to sugars increases the preference for and intake of sugar solutions in mice. We used brief-access lick tests and multiunit electrophysiological recordings from the nucleus of the solitary tract (NST) to investigate the role of taste in diet-induced changes in sucrose responsiveness. We exposed C57BL/6J (B6) and 129X1/SvJ (129) mice to either a sucrose diet (chow, water, and a 500mM sucrose solution) or a control diet (chow and water) for 3 days. In B6 mice, exposure to the sucrose diet decreased the appetitive response (i.e., number of trials initiated) but had no effect on the consummatory response (i.e., rate of licking) to 500mM sucrose and 20mM saccharin. In 129 mice, exposure to the sucrose diet increased the appetitive response but had no effect on the consummatory response to the sweetener solutions. In the NST recordings, the B6 mice exhibited larger multiunit responses to sweeteners than 129 mice, but there was no effect of the sucrose diet in either strain. Our results indicate that sucrose exposure alters the appetitive response of B6 and 129 mice to sweeteners in diametrically opposed ways and that these changes are mediated by structures in the gustatory neuraxis above the NST (e.g., ventral forebrain).
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Affiliation(s)
- Stuart A McCaughey
- Department of Biology, Barnard College, Columbia University, 3009 Broadway, New York, NY 10027, USA.
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29
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Wauson EM, Lorente-Rodríguez A, Cobb MH. Minireview: Nutrient sensing by G protein-coupled receptors. Mol Endocrinol 2013; 27:1188-97. [PMID: 23820899 DOI: 10.1210/me.2013-1100] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are membrane proteins that recognize molecules in the extracellular milieu and transmit signals inside cells to regulate their behaviors. Ligands for many GPCRs are hormones or neurotransmitters that direct coordinated, stereotyped adaptive responses. Ligands for other GPCRs provide information to cells about the extracellular environment. Such information facilitates context-specific decision making that may be cell autonomous. Among ligands that are important for cellular decisions are amino acids, required for continued protein synthesis, as metabolic starting materials and energy sources. Amino acids are detected by a number of class C GPCRs. One cluster of amino acid-sensing class C GPCRs includes umami and sweet taste receptors, GPRC6A, and the calcium-sensing receptor. We have recently found that the umami taste receptor heterodimer T1R1/T1R3 is a sensor of amino acid availability that regulates the activity of the mammalian target of rapamycin. This review focuses on an array of findings on sensing amino acids and sweet molecules outside of neurons by this cluster of class C GPCRs and some of the physiologic processes regulated by them.
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Affiliation(s)
- Eric M Wauson
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA
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30
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Treesukosol Y, Spector AC. Orosensory detection of sucrose, maltose, and glucose is severely impaired in mice lacking T1R2 or T1R3, but Polycose sensitivity remains relatively normal. Am J Physiol Regul Integr Comp Physiol 2012; 303:R218-35. [PMID: 22621968 DOI: 10.1152/ajpregu.00089.2012] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Evidence in the literature supports the hypothesis that the T1R2+3 heterodimer binds to compounds that humans describe as sweet. Here, we assessed the necessity of the T1R2 and T1R3 subunits in the maintenance of normal taste sensitivity to carbohydrate stimuli. We trained and tested water-restricted T1R2 knockout (KO), T1R3 KO and their wild-type (WT) same-sex littermate controls in a two-response operant procedure to sample a fluid and differentially respond on the basis of whether the stimulus was water or a tastant. Correct responses were reinforced with water and incorrect responses were punished with a time-out. Testing was conducted with a modified descending method of limits procedure across daily 25-min sessions. Both KO groups displayed severely impaired performance and markedly decreased sensitivity when required to discriminate water from sucrose, glucose, or maltose. In contrast, when Polycose was tested, KO mice had normal EC(50) values for their psychometric functions, with some slight, but significant, impairment in performance. Sensitivity to NaCl did not differ between these mice and their WT controls. Our findings support the view that the T1R2+3 heterodimer is the principal receptor that mediates taste detection of natural sweeteners, but not of all carbohydrate stimuli. The combined presence of T1R2 and T1R3 appears unnecessary for the maintenance of relatively normal sensitivity to Polycose, at least in this task. Some detectability of sugars at high concentrations might be mediated by the putative polysaccharide taste receptor, the remaining T1R subunit forming either a homodimer or heteromer with another protein(s), or nontaste orosensory cues.
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Affiliation(s)
- Yada Treesukosol
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA
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Current and emerging concepts on the role of peripheral signals in the control of food intake and development of obesity. Br J Nutr 2012; 108:778-93. [PMID: 22409929 DOI: 10.1017/s0007114512000529] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The gastrointestinal peptides are classically known as short-term signals, primarily inducing satiation and/or satiety. However, accumulating evidence has broadened this view, and their role in long-term energy homeostasis and the development of obesity has been increasingly recognised. In the present review, the recent research involving the role of satiation signals, especially ghrelin, cholecystokinin, glucagon-like peptide 1 and peptide YY, in the development and treatment of obesity will be discussed. Their activity, interactions and release profile vary constantly with changes in dietary and energy influences, intestinal luminal environment, body weight and metabolic status. Manipulation of gut peptides and nutrient sensors in the oral and postoral compartments through diet and/or changes in gut microflora or using multi-hormone 'cocktail' therapy are among promising approaches aimed at reducing excess food consumption and body-weight gain.
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McCool BA, Chappell AM. Using monosodium glutamate to initiate ethanol self-administration in inbred mouse strains. Addict Biol 2012; 17:121-31. [PMID: 21054690 DOI: 10.1111/j.1369-1600.2010.00260.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Voluntary oral ethanol consumption in rodents is generally limited by strong taste-aversion in these species. Historically, this has been overcome by combining ethanol with a sweetener, typically sucrose or saccharine, and then slowly 'fading' away the sweetener. While useful in most instances, this approach has not proven as successful for some inbred strains of mice (e.g. DBA/2J) despite consistent evidence in the literature that these same strains express strong conditioned place preference for intraperitoneal- or intragastric-administered ethanol. Importantly, DBA/2J mice express a polymorphism in a 'sweet' taste receptor subunit gene that reduces the potency of sweet substances in these mice. We hypothesized that the presence of this polymorphism might help explain the contrasting behavioral findings of weak voluntary oral ethanol consumption following sucrose-fade yet robust conditioned place preference for ethanol in this strain. To test this, we compared ethanol consumption initiated by either a 'traditional' sucrose-fade or a fade from an alternative tastant, monosodium glutamate (MSG). We found that in both C57BL/6J and DBA/2J mice, the MSG-fade produced robust increases in home cage ethanol consumption relative to the traditional sucrose-fade. This increased ethanol intake following MSG-fade was evident across a range of ethanol concentrations. Our findings suggest the potential utility of the MSG-fade to establish stable voluntary oral ethanol consumption in mice, particularly ethanol 'non-preferring' strains such as DBA/2J and lend additional support to the notion that ethanol consumption in DBA/2J mice is limited by pronounced taste aversion.
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Affiliation(s)
- Brian A McCool
- Translational Center for the Neurobehavioral Study on Alcohol, Department of Physiology & Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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Behavioral evidence for a glucose polymer taste receptor that is independent of the T1R2+3 heterodimer in a mouse model. J Neurosci 2011; 31:13527-34. [PMID: 21940444 DOI: 10.1523/jneurosci.2179-11.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Although it is clear that the heterodimer formed by the T1R2 and T1R3 proteins serves as the primary taste receptor for sweeteners, there is growing evidence that responses to glucose polymers may be mediated by a different taste receptor. Here we report that although T1R2 knock-out (KO) and T1R3 KO mice displayed severely impaired responding to glucose, maltose, and maltotriose in an initial session of a brief-access taste test (5 s trials, 25 min sessions) relative to wild-type (WT) mice, they subsequently increased their licking as a function of concentration for maltose and maltotriose with continued testing, presumably due to associating weak oral cues with positive post-ingestive consequences. Interestingly, these KO mice displayed relatively normal concentration-dependent licking to Polycose, a mixture of glucose polymers, even in the first session. Importantly, the experience-dependent increase in responsiveness to the sugars observed with the T1R2 and T1R3 single KO mice was not statistically significant in the T1R2/3 double KO mice. The double KO mice, however, still displayed significant concentration-dependent responding to Polycose in the first test session, albeit lick rates were slightly lower than those seen for WT mice, perhaps because small amounts of glucose, maltose, and maltotriose found in Polycose were enhancing the signal in WT mice or because T1R2 or T1R3 can possibly heteromerize with another protein to form a fully functional glucose polymer receptor. These findings provide behavioral evidence that glucose polymers, with an optimal chain length greater than three glucose moieties, stimulate a taste receptor independent of the T1R2+3 heterodimer.
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Behavioral evidence for a glucose polymer taste receptor that is independent of the T1R2+3 heterodimer in a mouse model. J Neurosci 2011. [PMID: 21940444 DOI: 10.1523/jneurosci.2179‐11.2011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although it is clear that the heterodimer formed by the T1R2 and T1R3 proteins serves as the primary taste receptor for sweeteners, there is growing evidence that responses to glucose polymers may be mediated by a different taste receptor. Here we report that although T1R2 knock-out (KO) and T1R3 KO mice displayed severely impaired responding to glucose, maltose, and maltotriose in an initial session of a brief-access taste test (5 s trials, 25 min sessions) relative to wild-type (WT) mice, they subsequently increased their licking as a function of concentration for maltose and maltotriose with continued testing, presumably due to associating weak oral cues with positive post-ingestive consequences. Interestingly, these KO mice displayed relatively normal concentration-dependent licking to Polycose, a mixture of glucose polymers, even in the first session. Importantly, the experience-dependent increase in responsiveness to the sugars observed with the T1R2 and T1R3 single KO mice was not statistically significant in the T1R2/3 double KO mice. The double KO mice, however, still displayed significant concentration-dependent responding to Polycose in the first test session, albeit lick rates were slightly lower than those seen for WT mice, perhaps because small amounts of glucose, maltose, and maltotriose found in Polycose were enhancing the signal in WT mice or because T1R2 or T1R3 can possibly heteromerize with another protein to form a fully functional glucose polymer receptor. These findings provide behavioral evidence that glucose polymers, with an optimal chain length greater than three glucose moieties, stimulate a taste receptor independent of the T1R2+3 heterodimer.
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Abstract
PURPOSE OF REVIEW To review the recent work on potential mechanisms underlying a paradoxical positive association between the consumption of non-nutritive sweeteners (NNS) and weight gain. RECENT FINDINGS Several potential mechanisms, not mutually exclusive, are hypothesized. First, by dissociating sweetness from calories, NNS could interfere with physiological responses that control homeostasis. Second, by changing the intestinal environment, NNS could affect the microbiota and in turn trigger inflammatory processes that are associated with metabolic disorders. Third, by interacting with novel sweet-taste receptors discovered in the gut, NNS could affect glucose absorptive capacity and glucose homeostasis. The latter mechanism that has received the most attention recently. Some animal studies, but not all, found that NNS activate gut sweet-taste pathways that control incretin release and upregulate glucose transporters. Human studies found that, at least for healthy fasted individuals, the sole interaction of NNS with sweet-taste gut receptors is insufficient to elicit incretin responses. The reasons for discrepancy between different studies are unknown but could be related to the species of mammal tested and the dose of NNS used. SUMMARY Whether NNS are metabolically inactive, as previously assumed, is unclear. Further research on the potential effects of NNS on human metabolism is warranted.
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Affiliation(s)
- Marta Y Pepino
- School of Medicine, Washington University in St. Louis, St. Louis, Missouri 63110, USA.
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36
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Bachmanov AA, Bosak NP, Floriano WB, Inoue M, Li X, Lin C, Murovets VO, Reed DR, Zolotarev VA, Beauchamp GK. Genetics of sweet taste preferences. FLAVOUR FRAG J 2011; 26:286-294. [PMID: 21743773 PMCID: PMC3130742 DOI: 10.1002/ffj.2074] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sweet taste is a powerful factor influencing food acceptance. There is considerable variation in sweet taste perception and preferences within and among species. Although learning and homeostatic mechanisms contribute to this variation in sweet taste, much of it is genetically determined. Recent studies have shown that variation in the T1R genes contributes to within- and between-species differences in sweet taste. In addition, our ongoing studies using the mouse model demonstrate that a significant portion of variation in sweetener preferences depends on genes that are not involved in peripheral taste processing. These genes are likely involved in central mechanisms of sweet taste processing, reward and/or motivation. Genetic variation in sweet taste not only influences food choice and intake, but is also associated with proclivity to drink alcohol. Both peripheral and central mechanisms of sweet taste underlie correlation between sweet-liking and alcohol consumption in animal models and humans. All these data illustrate complex genetics of sweet taste preferences and its impact on human nutrition and health. Identification of genes responsible for within- and between-species variation in sweet taste can provide tools to better control food acceptance in humans and other animals.
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Affiliation(s)
| | | | - Wely B Floriano
- Department of Chemistry, Lakehead University, Thunder Bay, ON, Canada
| | - Masashi Inoue
- Laboratory of Cellular Neurobiology, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Xia Li
- Monell Chemical Senses Center, Philadelphia, PA, USA
| | - Cailu Lin
- Monell Chemical Senses Center, Philadelphia, PA, USA
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37
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Treesukosol Y, Smith KR, Spector AC. The functional role of the T1R family of receptors in sweet taste and feeding. Physiol Behav 2011; 105:14-26. [PMID: 21376068 DOI: 10.1016/j.physbeh.2011.02.030] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 02/17/2011] [Accepted: 02/17/2011] [Indexed: 01/02/2023]
Abstract
The discovery of the T1R family of Class C G protein-coupled receptors in the peripheral gustatory system a decade ago has been a tremendous advance for taste research, and its conceptual reach has extended to other organ systems. There are three proteins in the family, T1R1, T1R2, and T1R3, encoded by their respective genes, Tas1r1, Tas1r2, and Tas1r3. T1R2 combines with T1R3 to form a heterodimer that binds with sugars and other sweeteners. T1R3 also combines with T1R1 to form a heterodimer that binds with l-amino acids. These proteins are expressed not only in taste bud cells, but one or more of these T1Rs have also been identified in the nasal epithelium, gut, pancreas, liver, kidney, testes and brain in various mammalian species. Here we review current perspectives regarding the functional role of these receptors, concentrating on sweet taste and feeding. We also discuss behavioral findings suggesting that a glucose polymer mixture, Polycose, which rodents avidly prefer, appears to activate a receptor that does not depend on the combined expression of T1R2 and T1R3. In addition, although the T1Rs have been implicated as playing a role in glucose sensing, T1R2 knock-out (KO) and T1R3 KO mice display normal chow and fluid intake as well as normal body weight compared with same-sex littermate wild type (WT) controls. Moreover, regardless of whether they are fasted or not, these KO mice do not differ from their WT counterparts in their Polycose intake across a broad range of concentrations in 30-minute intake tests. The functional implications of these results and those in the literature are considered.
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Affiliation(s)
- Yada Treesukosol
- Department of Psychology and Program in Neuroscience, Florida State University, 1107 West Call Street, P.O. Box 3064301, Tallahassee FL 32306, USA
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38
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Sellier MJ, Reeb P, Marion-Poll F. Consumption of bitter alkaloids in Drosophila melanogaster in multiple-choice test conditions. Chem Senses 2010; 36:323-34. [PMID: 21173029 DOI: 10.1093/chemse/bjq133] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Drosophila melanogaster adapt their food consumption to their internal needs and avoid ingesting noxious molecules. Defects in the genes involved in these decisions induce behavioral alterations that are usually screened by monitoring flies feeding in 2-choice or in no-choice situations. Here, we introduce a new behavioral test in which groups of flies are given access to 6 capillary feeders (MultiCAFE) containing fructose mixed with a serial dilution of a test substance. Using quinine, we first showed that fly density, distance between capillaries, and order of presentation have a minor impact on the discrimination performances of the flies. Fly discrimination was also only marginally affected by the type of test (no-choice, binary, or multiple-choice). Interestingly, the feeding reduction was well correlated with a reduction of the firing elicited by the mixture in sugar-sensitive gustatory receptor neurons, suggesting that several mechanisms concur to allow flies to make their choices. In addition to quinine, flies exhibited marked dose-dependent aversions to the consumption of berberine, caffeine, lobeline, nicotine, papaverine, strychnine, and theophylline, which all taste bitter to humans. Thus, despite of the multiplicity of choices available, flies consistently avoid alkaloids mixed with a sugar solution, and their choices are strongly dependent on their taste system. The MultiCAFE assay represents an interesting alternative to other feeding tests, in that it allows monitoring of the absolute consumption while also requiring less flies and time to run than other assays.
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Affiliation(s)
- Marie-Jeanne Sellier
- Insitut National de la Recherche Agronomique, Département Santé des Plantes et Environnement, UMR 1272 Physiologie de l'Insecte, Versailles, France
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Glendinning JI, Beltran F, Benton L, Cheng S, Gieseke J, Gillman J, Spain HN. Taste does not determine daily intake of dilute sugar solutions in mice. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1333-41. [PMID: 20702804 DOI: 10.1152/ajpregu.00331.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When a rodent licks a sweet-tasting solution, taste circuits in the central nervous system that facilitate stimulus identification, motivate intake, and prepare the body for digestion are activated. Here, we asked whether taste also determines daily intake of sugar solutions in C57BL/6 mice. We tested several dilute concentrations of glucose (167, 250, and 333 mM) and fructose (167, 250, and 333 mM). In addition, we tested saccharin (38 mM), alone and in binary mixture with each of the sugar concentrations, to manipulate sweet taste intensity while holding caloric value constant. In experiment 1, we measured taste responsiveness to the sweetener solutions in two ways: chorda tympani nerve responses and short-term lick tests. For both measures, the mice exhibited the following relative magnitude of responsiveness: binary mixtures > saccharin > individual sugars. In experiment 2, we asked whether the taste measures reliably predicted daily intake of the sweetener solutions. No such relationship was observed. The glucose solutions elicited weak taste responses but high daily intakes, whereas the fructose solutions elicited weak taste responses and low daily intakes. On the other hand, the saccharin + glucose solutions elicited strong taste responses and high daily intakes, while the saccharin + fructose solutions elicited strong taste responses but low daily intakes. Overall, we found that 1) daily intake of the sweetener solutions varied independently of the magnitude of the taste responses and 2) the solutions containing glucose stimulated substantially higher daily intakes than did the solutions containing isomolar concentrations of fructose. Given prior work demonstrating greater postoral stimulation of feeding by glucose than fructose, we propose that the magnitude of postoral nutritive stimulation plays a more important role than does taste in determining daily intake of dilute sugar solutions.
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Affiliation(s)
- J I Glendinning
- Dept. of Biological Sciences, Barnard College, Columbia Univ., 3009 Broadway, New York, NY 10027, USA.
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40
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Nelson TM, Lopezjimenez ND, Tessarollo L, Inoue M, Bachmanov AA, Sullivan SL. Taste function in mice with a targeted mutation of the pkd1l3 gene. Chem Senses 2010; 35:565-77. [PMID: 20605874 DOI: 10.1093/chemse/bjq070] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Recent studies, both in vitro and in vivo, have suggested the involvement of the polycystic kidney disease-1 and -2 like genes, Pkd1l3 and Pkd2l1, in acid taste transduction. In mice, disruption of taste cells expressing PKD2L1 eliminates gustatory neural responses to acids. However, no previous data exist on taste responses in the absence of PKD1L3 or on behavioral responses in mice lacking either of these proteins. In order to assess the function of PKD1L3, we genetically engineered mice with a targeted mutation of the Pkd1l3 gene. We then examined taste responsiveness of mutant and wild-type mice using several different approaches. In separate groups of mice, we measured preference scores in 48-h 2-bottle tests, determined NaCl or citric acid taste thresholds using a conditioned taste aversion technique, and conducted electrophysiological recordings of activity in the chorda tympani and glossopharyngeal nerves. Multiple taste compounds representing all major taste qualities were used in the preference tests and nerve-recording experiments. We found no significant reduction in taste responsiveness in Pkd1l3 mutant mice in behavioral or electrophysiological tests when compared with wild-type controls. Therefore, further studies are needed to elucidate the function of PKD1L3 in taste bud cells.
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41
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Murovets VO, Zolotarev VA, Bachmanov AA. The role of the Sac locus in the alcohol taste preference in inbred mouse strains. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2010; 432:181-3. [PMID: 20665148 DOI: 10.1134/s001249661003004x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Indexed: 11/23/2022]
Affiliation(s)
- V O Murovets
- Pavlov Institute of Physiology, Russian Academy of Sciences, nab. Makarova 6, St. Petersburg, 199034, Russia
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42
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Glendinning JI, Breinager L, Kyrillou E, Lacuna K, Rocha R, Sclafani A. Differential effects of sucrose and fructose on dietary obesity in four mouse strains. Physiol Behav 2010; 101:331-43. [PMID: 20600198 DOI: 10.1016/j.physbeh.2010.06.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 06/03/2010] [Accepted: 06/08/2010] [Indexed: 01/14/2023]
Abstract
We examined sugar-induced obesity in mouse strains polymorphic for Tas1r3, a gene that codes for the T1R3 sugar taste receptor. The T1R3 receptor in the FVB and B6 strains has a higher affinity for sugars than that in the AKR and 129P3 strains. In Experiment 1, mice had 40days of access to lab chow plus water, sucrose (10 or 34%), or fructose (10 or 34%) solutions. The strains consumed more of the sucrose than isocaloric fructose solutions. The pattern of strain differences in caloric intake from the 10% sugar solutions was FVB>129P3=B6>AKR; and that from the 34% sugar solutions was FVB>129P3>B6>/=AKR. Despite consuming more sugar calories, the FVB mice resisted obesity altogether. The AKR and 129P3 mice became obese exclusively on the 34% sucrose diet, while the B6 mice did so on the 34% sucrose and 34% fructose diets. In Experiment 2, we compared total caloric intake from diets containing chow versus chow plus 34% sucrose. All strains consumed between 11 and 25% more calories from the sucrose-supplemented diet. In Experiment 3, we compared the oral acceptability of the sucrose and fructose solutions, using lick tests. All strains licked more avidly for the 10% sucrose solutions. The results indicate that in mice (a) Tas1r3 genotype does not predict sugar-induced hyperphagia or obesity; (b) sucrose solutions stimulate higher daily intakes than isocaloric fructose solutions; and (c) susceptibility to sugar-induced obesity varies with strain, sugar concentration and sugar type.
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Affiliation(s)
- John I Glendinning
- Department of Biological Sciences, Barnard College, Columbia University, New York, NY 10027, United States.
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43
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Mirotti L, Mucida D, de Sá-Rocha LC, Costa-Pinto FA, Russo M. Food aversion: a critical balance between allergen-specific IgE levels and taste preference. Brain Behav Immun 2010; 24:370-5. [PMID: 20035860 DOI: 10.1016/j.bbi.2009.12.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 12/02/2009] [Accepted: 12/17/2009] [Indexed: 11/18/2022] Open
Abstract
Animals sensitized to allergens change their feeding behavior and avoid drinking the otherwise preferred sweetened solutions containing the allergens. This phenomenon, known as food aversion, appears to be mediated by allergen-specific IgE antibodies. Here we investigated food aversion in BALB/c and C57BL/6 mice, which differ in their allergic responses to the allergen ovalbumin as well as in their preference for sweet taste. BALB/c mice present higher levels of IgE and a natural lower preference for sweet flavors when compared to C57BL/6 mice. Specifically, we studied a conflicting situation in which animals simultaneously experienced the aversive contact with the allergen and the attractive sweet taste of increasing concentrations of sucrose. We found that BALB/c mice were more prone to develop food aversion than C57BL/6 mice and that this aversive behavior could be abolished in both strains by increasing the palatability of the solution containing the allergen. In both strains food aversion was positively correlated with the levels of allergen-specific IgE antibodies and inversely correlated with their preference for sucrose sweetened solutions.
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Affiliation(s)
- Luciana Mirotti
- Department of Pathology, School of Veterinary Medicine, University of São Paulo, São Paulo SP, Brazil
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44
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Brasser SM, Norman MB, Lemon CH. T1r3 taste receptor involvement in gustatory neural responses to ethanol and oral ethanol preference. Physiol Genomics 2010; 41:232-43. [PMID: 20145204 DOI: 10.1152/physiolgenomics.00113.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elevated alcohol consumption is associated with enhanced preference for sweet substances across species and may be mediated by oral alcohol-induced activation of neurobiological substrates for sweet taste. Here, we directly examined the contribution of the T1r3 receptor protein, important for sweet taste detection in mammals, to ethanol intake and preference and the neural processing of ethanol taste by measuring behavioral and central neurophysiological responses to oral alcohol in T1r3 receptor-deficient mice and their C57BL/6J background strain. T1r3 knockout and wild-type mice were tested in behavioral preference assays for long-term voluntary intake of a broad concentration range of ethanol, sucrose, and quinine. For neurophysiological experiments, separate groups of mice of each genotype were anesthetized, and taste responses to ethanol and stimuli of different taste qualities were electrophysiologically recorded from gustatory neurons in the nucleus of the solitary tract. Mice lacking the T1r3 receptor were behaviorally indifferent to alcohol (i.e., ∼50% preference values) at concentrations typically preferred by wild-type mice (5-15%). Central neural taste responses to ethanol in T1r3-deficient mice were significantly lower compared with C57BL/6J controls, a strain for which oral ethanol stimulation produced a concentration-dependent activation of sweet-responsive NTS gustatory neurons. An attenuated difference in ethanol preference between knockouts and controls at concentrations >15% indicated that other sensory and/or postingestive effects of ethanol compete with sweet taste input at high concentrations. As expected, T1r3 knockouts exhibited strongly suppressed behavioral and neural taste responses to sweeteners but did not differ from wild-type mice in responses to prototypic salt, acid, or bitter stimuli. These data implicate the T1r3 receptor in the sensory detection and transduction of ethanol taste.
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Affiliation(s)
- Susan M Brasser
- Center for Behavioral Teratology, Department of Psychology, San Diego State University, San Diego, California
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45
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An analysis of licking microstructure in three strains of mice. Appetite 2009; 54:320-30. [PMID: 20006663 DOI: 10.1016/j.appet.2009.12.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2009] [Revised: 11/24/2009] [Accepted: 12/08/2009] [Indexed: 01/17/2023]
Abstract
Mouse models of feeding provide a useful tool for elucidating the molecular pathways of energy regulation. The majority of studies in mice have been limited to intake analyses conducted over extended periods of time, which fail to distinguish between a variety of factors that influence nutrient intake. Using licking microstructure analyses we examined both the size and number of licking bursts for water, polycose, sucrose and lecithin in three strains of mice (C57BL/6J, 129Sv/ImJ and C57129F1 hybrids), using pause criteria (250-500, >500 and >1000 ms) that have previously been described in the rat. Burst size and number varied both as a function of tastant concentration and mouse strain; however, these differences were most evident with the >1000 ms pause criterion. Consistent with previous reports, during water consumption C57 mice showed longer mean interlick intervals, a larger number of bursts but reduced burst size relative to the two other strains. F1 mice showed larger burst sizes for polycose, while C57 mice displayed a greater number of bursts for both polycose and sucrose. Both 129 and F1 mice were insensitive to sucrose concentration, whereas C57 mice showed attenuated lecithin intake influenced by a reduction in the size of bursts for this tastant. These results suggest that these strains of mice display differences in the pattern of licking that are most evident with the use of larger pause criteria. These differences in licking behavior might reflect influences of genetic background on pre- and post-ingestive factors controlling intake, the reinforcing properties of each tastant, or native differences in licking style.
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46
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Bachmanov AA, Inoue M, Ji H, Murata Y, Tordoff MG, Beauchamp GK. Glutamate taste and appetite in laboratory mice: physiologic and genetic analyses. Am J Clin Nutr 2009; 90:756S-763S. [PMID: 19571213 PMCID: PMC3136004 DOI: 10.3945/ajcn.2009.27462l] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
This article provides an overview of our studies of variation in voluntary glutamate consumption in mice. In 2-bottle preference tests, mice from the C57BL/6ByJ (B6) strain consume more monosodium l-glutamate (MSG) than do mice from the 129P3/J (129) strain. We used these mice to study physiologic and genetic mechanisms that underlie the strain differences in glutamate intake. Our genetic analyses showed that differences between B6 mice and 129 mice in MSG consumption are unrelated to strain variation in consumption of sodium or sweeteners and therefore are attributed to mechanisms specific for glutamate. These strain differences could be due to variation in responses to either taste or postingestive effects of glutamate. To examine the role of taste responsiveness, we measured MSG-evoked activity in gustatory nerves and showed that it is similar in B6 and 129 mice. On the other hand, strain-specific postingestive effects of glutamate were evident from our finding that exposure to MSG increases its consumption in B6 mice and decreases its consumption in 129 mice. We therefore examined whether B6 mice and 129 mice differ in postingestive metabolism of glutamate. We showed that, after intragastric administration of MSG, the MSG is preferentially metabolized through gluconeogenesis in B6 mice, whereas thermogenesis is the predominant process for 129 mice. We hypothesize that a process related to gluconeogenesis of the ingested glutamate generates the rewarding stimulus, which probably occurs in the liver before glucose enters the general circulation, and that the glutamate-induced postingestive thermogenesis generates an aversive stimulus. Our animal model studies raise the question of whether humans also vary in glutamate metabolism in a manner that influences their glutamate preference, consumption, and postingestive processing.
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Kidd M, Hauso Ø, Drozdov I, Gustafsson BI, Modlin IM. Delineation of the chemomechanosensory regulation of gastrin secretion using pure rodent G cells. Gastroenterology 2009; 137:231-41, 241.e1-10. [PMID: 19208342 DOI: 10.1053/j.gastro.2009.01.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 12/12/2008] [Accepted: 01/08/2009] [Indexed: 12/24/2022]
Abstract
BACKGROUND & AIMS Gastrin is a key regulator of gastric acid secretion. We aimed to isolate pure G cells to identify the mechanistic basis of luminal- and strain-mediated regulation. METHODS Using gradient centrifugation and fluorescence-activated cell sorting, rat G cells were prepared and luminal, neural, hormonal, and mechanical activation of secretion and signaling pathways studied. RESULTS Pure G-cell preparations (>97%) were isolated. Reverse-transcription polymerase chain reaction identified neural, hormonal, bacterial, and luminal G protein-coupled receptors, and immunostaining visualized specific sweet/bitter receptors and the tastant-associated G protein alpha-gustducin. Gastrin release was stimulated by forskolin (adenosine 3',5'-cyclic monophosphate [cAMP] inducer, 10 micromol/L; >3-fold), potentiated by 3-isobutyl-1-methylxanthine (IBMX; phosphodiesterase type 5 inhibitor and adenosine antagonist, 10 micromol/L) and phorbol myristate acetate (phorbol ester, 10 micromol/L), and inhibited by H-89 (protein kinase A inhibitor, 10 micromol/L), PD98059 (MEK1 inhibitor, 0.1 micromol/L), and wortmannin (phosphatidylinositol 3-kinase inhibitor, 1 nmol/L). Gastrin release was stimulated by neuronal G protein-coupled receptor ligands, pituitary adenylate cyclase-activating protein (20 pmol/L, >8-fold) and bombesin (0.1 micromol/L, 8-fold) through cAMP signaling. The tastants sucralose, glucose, caffeine, denatonium, and the vanilloid receptor activator capsaicin all stimulated secretion (>3-fold), as did bacterial lipopolysaccharides Salmonella enteritidis (0.24 nmol/L, 5-fold) greater than Helicobacter pylori (0.57 micromol/L, 3-fold). Secretion was associated with elevated cAMP levels (approximately 2-fold) and could be inhibited by H-89 and PD98059 and potentiated by IBMX and cholera toxin (250 microg/mL). Bacterially mediated secretion also involved activation of nuclear factor kappaB and the c-Jun-N-terminal kinase pathway. Mechanical strain stimulated (2-fold to 8-fold) gastrin release, and decreasing pH from 7.4 to 5.5 inhibited release. The adenosine receptor 2B antagonist MRS1754 inhibited mechanically induced gastrin release. CONCLUSIONS G cells are luminal sampling chemomechanosensory cells whose secretion is regulated by neural, hormonal, luminal, and mechanical factors through protein kinase A activation, cAMP signaling, and mitogen-activated protein kinase phosphorylation.
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Affiliation(s)
- Mark Kidd
- Gastrointestinal Pathobiology Research Group, Department of Gastroenterology, Yale University School of Medicine, New Haven, Connecticut 06520-8062, USA
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Lemon CH, Margolskee RF. Contribution of the T1r3 taste receptor to the response properties of central gustatory neurons. J Neurophysiol 2009; 101:2459-71. [PMID: 19279151 DOI: 10.1152/jn.90892.2008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
T1r3 is a critical subunit of T1r sweet taste receptors. Here we studied how the absence of T1r3 impacts responses to sweet stimuli by taste neurons in the nucleus tractus solitarius (NTS) of the mouse. The consequences bear on the multiplicity of sweet taste receptors and how T1r3 influences the distribution of central gustatory neurons. Taste responses to glycine, sucrose, NaCl, HCl, and quinine were electrophysiologically recorded from single NTS neurons in anesthetized T1r3 knockout (KO) and wild-type (WT) C57BL/6 mice. Other stimuli included l-proline, d-fructose, d-glucose, d-sorbitol, Na-saccharin, acesulfame-K, monosodium glutamate, NaNO(3), Na-acetate, citric acid, KCl, denatonium, and papaverine. Forty-one WT and 41 KO neurons were recorded. Relative to WT, KO responses to all sweet stimuli were significantly lower, although the degree of attenuation differed among stimuli, with near zero responses to sugars but salient residual activity to artificial sweeteners and glycine. Residual KO across-neuron responses to sweet stimuli were variably similar to nonsweet responses, as indexed by multivariate and correlation analyses. In some cases, this suggested that residual KO activity to "sweet" stimuli could be mediated by nonsweet taste receptors, implicating T1r3 receptors as primary contributors to NTS sweet processing. The influence of T1r3 on the distribution of NTS neurons was evaluated by comparing neuron types that emerged between WT and KO cells. Neurons tuned toward sweet stimuli composed 34% of the WT sample but did not appear among KO cells. Input from T1r3-containing receptors critically guides the normal development of NTS neurons oriented toward sweet tastants.
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Affiliation(s)
- Christian H Lemon
- Department of Anatomy, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
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Treesukosol Y, Blonde GD, Spector AC. T1R2 and T1R3 subunits are individually unnecessary for normal affective licking responses to Polycose: implications for saccharide taste receptors in mice. Am J Physiol Regul Integr Comp Physiol 2009; 296:R855-65. [PMID: 19158407 DOI: 10.1152/ajpregu.90869.2008] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The T1R2 and T1R3 proteins are expressed in taste receptor cells and form a heterodimer binding with compounds described as sweet by humans. We examined whether Polycose taste might be mediated through this heterodimer by testing T1R2 knockout (KO) and T1R3 KO mice and their wild-type (WT) littermate controls in a series of brief-access taste tests (25-min sessions with 5-s trials). Sucrose, Na-saccharin, and Polycose were each tested for three consecutive sessions with order of presentation varied among subgroups in a Latin-Square manner. Both KO groups displayed blunted licking responses and initiated significantly fewer trials of sucrose and Na-saccharin across a range of concentrations. KO mice tested after Polycose exposure demonstrated some degree of concentration-dependent licking of sucrose, likely attributable to learning related to prior postingestive experience. These results are consistent with prior findings in the literature, implicating the T1R2+3 heterodimer as the principal taste receptor for sweet-tasting ligands, and also provide support for the potential of postingestive experience to influence responding in the KO mice. In contrast, T1R2 KO and T1R3 KO mice displayed concentration-dependent licking responses to Polycose that tracked those of their WT controls and in some cases licked midrange concentrations more; the number of Polycose trials initiated overall did not differ between KO and WT mice. Thus, the T1R2 and T1R3 proteins are individually unnecessary for normal concentration-dependent licking of Polycose to be expressed in a brief-access test. Whether at least one of these T1R protein subunits is necessary for normal Polycose responsiveness remains untested. Alternatively, there may be a novel taste receptor(s) that mediates polysaccharide taste.
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Affiliation(s)
- Yada Treesukosol
- Dept. of Psychology, Florida State Univ., Tallahassee FL 32306-4301, USA.
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Wang H, Iguchi N, Rong Q, Zhou M, Ogunkorode M, Inoue M, Pribitkin EA, Bachmanov AA, Margolskee RF, Pfeifer K, Huang L. Expression of the voltage-gated potassium channel KCNQ1 in mammalian taste bud cells and the effect of its null-mutation on taste preferences. J Comp Neurol 2009; 512:384-98. [PMID: 19006182 PMCID: PMC2734193 DOI: 10.1002/cne.21899] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Vertebrate taste buds undergo continual cell turnover. To understand how the gustatory progenitor cells in the stratified lingual epithelium migrate and differentiate into different types of mature taste cells, we sought to identify genes that were selectively expressed in taste cells at different maturation stages. Here we report the expression of the voltage-gated potassium channel KCNQ1 in mammalian taste buds of mouse, rat, and human. Immunohistochemistry and nuclear staining showed that nearly all rodent and human taste cells express this channel. Double immunostaining with antibodies against type II and III taste cell markers validated the presence of KCNQ1 in these two types of cells. Co-localization studies with cytokeratin 14 indicated that KCNQ1 is also expressed in type IV basal precursor cells. Null mutation of the kcnq1 gene in mouse, however, did not alter the gross structure of taste buds or the expression of taste signaling molecules. Behavioral assays showed that the mutant mice display reduced preference to some umami substances, but not to any other taste compounds tested. Gustatory nerve recordings, however, were unable to detect any significant change in the integrated nerve responses of the mutant mice to umami stimuli. These results suggest that although it is expressed in nearly all taste bud cells, the function of KCNQ1 is not required for gross taste bud development or peripheral taste transduction pathways, and the reduced preference of kcnq1-null mice in the behavioral assays may be attributable to the deficiency in the central nervous system or other organs.
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Affiliation(s)
- Hong Wang
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Naoko Iguchi
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Qi Rong
- Laboratory of Mammalian Genes and Development, NICHD/NIH 9000, Rockville Pike, Bethesda, MD 20892, USA
| | - Minliang Zhou
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Martina Ogunkorode
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Masashi Inoue
- Department of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo, Japan
| | - Edmund A. Pribitkin
- Department of Otolaryngology-Head and Neck Surgery, Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107, USA
| | | | - Robert F. Margolskee
- Department of Neuroscience, Mount Sinai School of Medicine, 1425 Madison Avenue, New York, NY 10029, USA
| | - Karl Pfeifer
- Laboratory of Mammalian Genes and Development, NICHD/NIH 9000, Rockville Pike, Bethesda, MD 20892, USA
| | - Liquan Huang
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
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