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 Overview

• Status: Completed
• Conditions: Healthy

• Study Type: Observational
• Enrollment (Actual): 70

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19104
      • Monell Chemical Senses Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Adults of all races and both genders (N=100) will be involved in the proposed research. Typically, our population of subjects is approximately 45% African American, 45% Caucasian, 6% Hispanic, and 4% Asian. This increased representation of under-represented minorities in our subject populations is reflective of the greater Philadelphia region and has been achieved, in part, through our outreach efforts advertising in local newspapers throughout the city.

Description

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.

Study Plan

How is the study designed?

What is the study measuring?

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)

Collaborators and Investigators

• Sponsor: Monell Chemical Senses Center
• Collaborators: National Institute on Deafness and Other Communication Disorders (NIDCD)
• Investigators: Principal Investigator: Julie A. Mennella, PhD, Monell Chemical Senses Center

Publications and helpful links

General Publications

• Lipchock SV, Mennella JA, Spielman AI, Reed DR. Human bitter perception correlates with bitter receptor messenger RNA expression in taste cells. Am J Clin Nutr. 2013 Oct;98(4):1136-43. doi: 10.3945/ajcn.113.066688. Epub 2013 Sep 11.

Study record dates

Study Major Dates

• Study Start: July 1, 2011
• Primary Completion (Actual): June 1, 2013
• Study Completion (Actual): June 1, 2013

Study Registration Dates

• First Submitted: July 20, 2011
• First Submitted That Met QC Criteria: July 21, 2011
• First Posted (Estimate): July 22, 2011

Study Record Updates

• Last Update Posted (Actual): December 18, 2017
• Last Update Submitted That Met QC Criteria: December 14, 2017
• Last Verified: December 1, 2017

More Information

Terms related to this study

• Keywords: genetics; epigenetics; psychophysics; bitter taste; bitterness sensitivity
• Other Study ID Numbers: 813211; F32DC011975-01A1 (U.S. NIH Grant/Contract); R01DC011287-01 (U.S. NIH Grant/Contract)