The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38

Study Overview
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Brief Summary
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This single-site, within-subject, experimental study is designed to test the hypothesis that individuals express taste receptors differently and have different sensitivities to bitter taste samples, which results from uneven expression. Subjects will include 100 racially and ethnically diverse, healthy adults. All subjects will provide saliva samples for genetic analysis and undergo taste testing with common psychophysical stimuli. From the pool of 100 subjects, 36 subjects from the common heterozygous group (PAV/AVI) and two from each homozygous group (AVI/AVI, nontaster and PAV/PAV, taster) will be invited to return for two additional sessions. During both sessions the investigators will 1) measure bitterness thresholds for PROP, a common psychophysical stimulus; 2) measure bitterness perception of several vegetables; 3) obtain a saliva sample and 4) collect taste papillae. The investigators will then isolate DNA and RNA from the taste papillae and isolate DNA from saliva to evaluate molecular differences over time and between individuals and how it relates to taste psychophysics. All psychophysical and cellular measurements will be done during both sessions so that the investigators can determine how much variation is observed over a one-week time period in both cellular phenotype and psychophysical phenotype.

Official Title
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The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38

Conditions
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Healthy

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Key inclusion criteria include age 18-40 years; English speaking, and good health at the time of study participation. Exclusion Criteria: Key exclusion criteria include cigarette smoking, which alters taste perception, oral disease and subjects undergoing Coumadin therapy. Subjects showing signs of oral disease, including tongue lesions or xerostomia will be excluded from tongue biopsy and therefore excluded from the study. Subjects undergoing Coumadin therapy will be excluded from tongue biopsy due to the risk of bleeding, and therefore excluded from the study. Subjects will not be excluded because of economic status, gender, race or ethnicity.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Bitter taste thresholds | Thresholds for propylthiouracil (PROP) will be measured using modified Harris-Kalmus recognition thresholds. | 2 days of testing (2 hours each) | 
| Taste intensity and hedonic ratings of vegetables | Subjects will rate the intensity of five basic taste qualities (bitter, salt, sweet, sour, umami) and the liking of PROP, urea, quinine, caffeine, denatonium solutions and pureed vegetables using the general labelled magnitude scale (gLMS) | 3 days of testing (1-2 hours each) | 
| TAS2R Genotype | Genotype of several TAS2Rs will be determined from DNA extracted from a saliva sample. | 1 day of testing (1-1.5 hours) | 
| mRNA expression levels | Expression of taste and related genes will be determined from mRNA extracted from human taste tissue obtained via tongue biopsy. | 2 days of testing (2 hours each) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dietary habits | Subjects will complete a 24 hour diet recall on 2 days of testing. | 2 days (2 hours each) | 
| biometrics | Height, weight, blood pressure and bioimpedance measurements will be taken. | 1 day (1-1.5 hours) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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bitter taste, psychophysics, genetics, epigenetics, bitterness sensitivity