The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38
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.
|Study Design:||Observational Model: Case-Only
Time Perspective: Cross-Sectional
|Official Title:||The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38|
- Bitter taste thresholds [ Time Frame: 2 days of testing (2 hours each) ] [ Designated as safety issue: No ]Thresholds for propylthiouracil (PROP) will be measured using modified Harris-Kalmus recognition thresholds.
- Taste intensity and hedonic ratings of vegetables [ Time Frame: 3 days of testing (1-2 hours each) ] [ Designated as safety issue: No ]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)
- TAS2R Genotype [ Time Frame: 1 day of testing (1-1.5 hours) ] [ Designated as safety issue: No ]Genotype of several TAS2Rs will be determined from DNA extracted from a saliva sample.
- mRNA expression levels [ Time Frame: 2 days of testing (2 hours each) ] [ Designated as safety issue: No ]Expression of taste and related genes will be determined from mRNA extracted from human taste tissue obtained via tongue biopsy.
- Dietary habits [ Time Frame: 2 days (2 hours each) ] [ Designated as safety issue: No ]Subjects will complete a 24 hour diet recall on 2 days of testing.
- biometrics [ Time Frame: 1 day (1-1.5 hours) ] [ Designated as safety issue: No ]Height, weight, blood pressure and bioimpedance measurements will be taken.
Biospecimen Retention: Samples With DNA
Saliva and taste tissue will be collected from individuals enrolled in the study.
|Study Start Date:||July 2011|
|Estimated Study Completion Date:||June 2013|
|Estimated Primary Completion Date:||June 2013 (Final data collection date for primary outcome measure)|
|United States, Pennsylvania|
|Monell Chemical Senses Center|
|Philadelphia, Pennsylvania, United States, 19104|
|Principal Investigator:||Julie A. Mennella, PhD||Monell Chemical Senses Center|