Paul Breslin, Ph.D. - US grants

taste; sensory discrimination; physical chemical interaction; psychophysics; sodium chloride; hydrochloric acid; sucrose; ammonium chloride; sweetening agents; quinine; potassium chloride; solutions; human subject;

The minimal number of taste compounds (singly or mixed) that are necessary to match the taste of any other solution is not known. l define a group of compounds that match each other in taste as an "equivalence class". I propose to identify equivalence classes for the majority of this work using a technique called matching, which has seldom been used in taste psychophysics. This method provides a powerful tool to further our understanding of the organization of the taste system. Specifically I will ask whether the taste of one chemical solution may be rendered indistinguishable from the taste elicited by a different chemical solution by varying the strength and composition of one while holding the other constant. This psychophysical approach successfully described the psychophysical laws of color matching and determined the number of color vision coding pathways to be three (trichromacy). The parallel hypothesis for taste (N-geusia) will establish a framework for identifying and describing the psychophysical laws of taste matching and will also help identify the number of distinct coding pathways that encode signals for taste qualities. If the tastes of all sapid substances comprise one or more of the four qualities, then it should be possible to match compounds with complex tastes, like that of saccharin which is described as sweet and bitter, with mixtures of compounds that are more purely sweet and bitter. The ultimate ~goal of this project is to determine the extent to which different stimuli elicit unique qualities of taste, and in so doing, improve the understanding of the psychophysics of human taste sensation.

[unreadable] DESCRIPTION (provided by applicant): For sensory science in general, a major goal is to understand the relationships among perceptions and the underlying sensory mechanisms at various levels; that is, to assign psychological consequences to the functions of the genes associated with the sensory system. Within bitter taste alone, there are dozens, of genes specifically involved just with detecting bitterness The daunting task of ascribing function to these genes will require a multidisciplinary approach that combines genetics and genomics with studies of perception and physiology. The ultimate long-term goal of the proposed project is to identify genes associated with specific bitter-taste sensitivities. An essential initial step towards the goals, as outlined in this proposal, is to phenotype bitter taste perception and to rigorously establish reliable individual differences. Subjects will be screened using a broad array of forced-choice and scaling techniques that examine many bitter perceptual attributes. We have now identified two robust classes of individual differences in bitterness sensitivities: (i) people who show a specific bitter insensitivity for sucrose octaacetate (SOA) and (ii) people who are totally bitter blind with otherwise normal taste. Bitter blindness is a rare trait found in three individuals thus far. SOA insensitivity appears in approximately 30% the population at large. In the present proposal, we will psychophysically screen approximately 500 subjects to identify affected SOA-insensitive probands and age, gender and race matched unaffected controls. The extended families of identified SOA-insensitive probands will be examined. Relative risk ratios, family correlations, segregation analyses and environmental and medical history interviews will be conducted to determine the heritability and, if genetic, the mode of inheritance for SOA insensitivity. The SOA study also has the advantage of examining a human phenotype that parallels the well-characterized mouse SOA insensitivity phenotype. DNA samples will be collected from all subjects, with the intention that candidate genes will be screened for polymorphisms and family-based linkage analysis conducted on a candidate region of the genome. As a second goal, 5000 subjects will be screened to determine the prevalence of bitter blindness. This novel phenotype will require extensive analysis in order to understand its impact on the perceptual taste world of affected individuals. Bitter blind probands and age, race and gender matched normal controls will be phenotyped psychophysically in' greater detail in the laboratory. The analyses of these important taste traits have the potential to reveal principles of organization of taste coding as well as underlying taste genomics.

Clinical taste deficits are rare disorders in the general population that occur at a rate well below that of olfactory loss (see Core). The dearth of taste patients renders the study of taste disorders difficult and, consequently, their treatment problematic. Yet, there is one prominent exception to this generalization; over 90% of all head and neck cancer patients who receive radiation therapy (radiotherapy) experience substantial taste loss and alterations of food flavor perception. These changes are major contributors to decreased food intake, anorexia, and weight loss. They also contribute to a significant decrement in general quality of life and an increase in suffering. Neither the full impact of radiotherapy on taste perception, nor the exact bases for gustatory abnormalities associated with it, is known. Radiotherapy may chronically alter the gustatory epithelia via repeated inflammatory insult, subsequent fibrotic and anti-vascular sequellae, and/or by genetic alteration of the epithelial/gustatory regenerative cellular processes. The long-term goals of this muttidisciplinary research program are: (1) to carefully document the magnitude, quality, and course of taste perception changes resulting from radiotherapy; (2) to simultaneously document morphological, histological, and molecular changes in the gustatory system that follow radiotherapy and relate these to observed perceptual changes; (3) to determine whether long-term gustatory deficits and abnormalities are caused by repeated, accumulated inflammatory insult, radiation-induced genetic alteration of reconstructive cells and stem cells, and/or the epithelial sequellae of these events, in order to begin to understand the causes of these abnormalities. This understanding will yield insight into potential therapeutic interventions for patients. It is also anticipated that the results will consummate in the development of patient outcome profiles providing important prognostic information to patients and their physicians and, ultimately, improve patient care and quality of life. Finally, information about how insult from radiation treatment compromises taste function may provide new insights into fundamental processes underlying normal orosensory biology.

Principal Investigator/Program Director (Last, first, middle): Breslin, Paul, A. S. RESEARCH &RELATED Other Project Information 1. * Are Human Subjects Involved? l Yes m No 1.a. If YES to Human Subjects Is the IRB review Pending? m Yes l No IRB Approval Date: 02-23-2007 Exemption Number: 1 2 3 4 5 6 Human Subject Assurance Number 00003489 2. * Are Vertebrate Animals Used? m Yes l No 2.a. If YES to Vertebrate Animals Is the IACUC review Pending? m Yes m No IACUC Approval Date: Animal Welfare Assurance Number 3. * Is proprietary/privileged information m Yes l No included in the application? 4.a.* Does this project have an actual or potential impact on m Yes l No the environment? 4.b. If yes, please explain: 4.c. If this project has an actual or potential impact on the environment, has an exemption been authorized or an environmental assessment (EA) or environmental impact statement (EIS) been performed? m Yes m No 4.d. If yes, please explain: 5.a.* Does this project involve activities outside the U.S. or m Yes l No partnership with International Collaborators? 5.b. If yes, identify countries: 5.c. Optional Explanation: 6. * Project Summary/Abstract 0015-Umami_SUMMARY.pdf Mime Type: application/pdf 7. * Project Narrative 1073-Umami_Narrative.pdf Mime Type: application/pdf 8. Bibliography &References Cited 5081-References_Cited_v2.pdf Mime Type: application/pdf 9. Facilities &Other Resources 5037-Facilities_and_Other_Resources_UMimAMe IT.pydpfe: application/pdf 10. Equipment 7157-Equipment_and_Resources_UmamMi.ipmdef Type: application/pdf Tracking Number: Other Information Page 5 OMB Number: 4040-0001 Expiration Date: 04/30/2008 Principal Investigator/Program Director (Last, first, middle): Breslin, Paul, A. S. SUMMARY/ABSRACT The umami taste of amino acids (especially glutamate) and sweetness are the two appetitive taste qualities that are critical for our healthy attraction to protein and carbohydrate (energy) macronutrients. The likely evolutionary pressure for an appetitive protein taste system is our nutritional need: access to sources of dietary protein is essential for survival and kwashiorkor (dietary protein deficiency) is one of the leading causes of death in children in developing countries. Despite its importance in dietary selection, human umami taste remains one of the most poorly understood of the five taste qualities and its genetic and molecular determinants remain largely unknown. Three classes of glutamate receptors found within taste receptor cells have been associated with cell signaling in response to amino acids and ribonucleotides: (i) TAS1Rs, (ii) metabotropic-GluRs, and (iii) ionotropic-NMDA receptors. However, their respective roles in human umami taste perception are not known. The long term goal of the proposed work is to elucidate genetic and molecular mechanisms that are responsible for the human sensation of `umami'taste. The objectives of the proposed project are to clarify the roles of these three receptor classes, to identify other genes that may be involved with human umami taste perception, and to functionally test variant receptors associated with umami phenotypes. The specific Aims of this Proposal are: I. Identify variant genes and/or genome-wide loci associated with umami blindness. II. Characterize any umami perceptual phenotypes related to glutamate receptor SNPs. III. Define variant glutamate receptor stimulus-response functions in expression assays. Project Description Page 6

? DESCRIPTION (provided by applicant) There is overwhelming evidence that the sweet receptor subunits T1R2 and T1R3 are key to the sense of sweet taste in mice, as well as in humans. Despite the clear importance of T1R receptors to sweet taste, there is evidence that alternative pathways exist for detection or modulation of sweet taste. Commonalities among taste cells of tongue and taste-like endocrine cells of gut and pancreas make it plausible that intestinal-type sugar sensors (e.g., glucose transporters (GLUTs) and sodium-glucose co-transporters (SGLTs)) or pancreatic-type metabolic sensors (ATP-gated KATP channels) might also be present in taste cells and function in sweet sensation of sugars. The main goal of this project is to identify and characterize T1R- independent mechanisms used by human taste receptor cells to sense sugars and calories. We hypothesize that sugar transporters and metabolic sensors underlie T1R-independent sugar sensing in human taste receptor cells. We also hypothesize that metabolic responses of human taste cells contribute to the perception of sweet taste and help impart the stronger preference for nutritive over non-caloric sweeteners. We hypothesize further that metabolism of glucose transported into sweet-responsive human taste cells leads to elevated intracellular ATP that closes the taste cell's KATP channels, depolarizing the cell. We will test these hypotheses using histological and functional studies in cultured human taste receptor cells and taste psychophysical tests in human subjects. Together these studies will determine if sugar transporters and KATP channels are present and active in human taste cells and if they are likely to contribute to sugar sensing and oral reward in human subjects. If this metabolic sensor in the sweet taste system can be stimulated without adding calories, it could provide an effective means to help reduce excess sugar in the US diet, thereby reducing the risk of obesity and other diseases associated with overconsumption of calories.

Abstract Relatedness of Supplement Aim to Parent Grant In the parent grant, we use cultured human taste (HBO) cells, pioneered at Monell by Co-Investigator Hakan Ozdener, to probe the metabolic sweet taste signaling pathway. HBO cells provide a useful model for probing taste signaling in culture, but they have also been shown useful for investigating the pathophysiology of certain neurotrophic viral diseases (e.g. Zika virus; see Ozdener et al., 2020). Using HBO cells to accomplish the Supplement Aim will advance our understanding of the pathogenicity of SARS-CoV-2 and other viruses that adversely affect taste and olfaction. Although many studies have reported taste and olfactory loss in individuals with COVID-19 disease, the underlying mechanisms and cellular effects in taste cells are not well understood. Due to changes in taste function in patients with COVID-19, it will be of particular interest to the parent grant to know if the subset of sweet taste cells is susceptible to infection by SARS-CoV-2.