Clinical trial NCT01399944: The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38
Official title: The Molecular Basis for a Broad Range of Phenotypes Related to hTAS2R38
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Healthy
Keywords: bitter taste
psychophysics
genetics
epigenetics
bitterness sensitivity
Lead sponsor: Monell Chemical Senses Center
Sponsor class: OTHER
Collaborators: name: National Institute on Deafness and Other Communication Disorders (NIDCD)
First posted: 2011-07-22
Enrollment: 70
Sex: ALL
Minimum age (years): 18
Maximum age (years): 40
Standard ages: ADULT
Accepts healthy volunteers: yes
Observational model: CASE_ONLY
Time perspective: CROSS_SECTIONAL
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.

Brief summary: 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.


Eligibility criteria: 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.

Primary outcomes:
measure: Bitter taste thresholds
timeFrame: 2 days of testing (2 hours each)
measure: Taste intensity and hedonic ratings of vegetables
timeFrame: 3 days of testing (1-2 hours each)
measure: TAS2R Genotype
timeFrame: 1 day of testing (1-1.5 hours)
measure: mRNA expression levels
timeFrame: 2 days of testing (2 hours each)
Secondary outcomes:
measure: Dietary habits
timeFrame: 2 days (2 hours each)
measure: biometrics
timeFrame: 1 day (1-1.5 hours)
Other outcomes:
Locations:
city: Philadelphia
country: United States
facility: Monell Chemical Senses Center
state: Pennsylvania
Study officials:
affiliation: Monell Chemical Senses Center
name: Julie A. Mennella, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: 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.