Taste Physiology in Healthy, Normal-weight Volunteers

Study Overview
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Brief Summary
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Taste physiology describes five main taste qualities in humans: sweet, sour, salty, umami and bitter. The receptors found on the tongue are also found in the entire gut. The correlation of stimulation of these gut receptors and brain activity has not yet been examined. The objectives are to investigate the effect of different taste substances on i) regional brain activity and ii) satiation peptide release.

Official Title
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Taste Physiology in Healthy, Normal-weight Volunteers

Conditions
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Exploratory Behavior

Intervention / Treatment
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* Dietary Supplement: Single intragastric instillation of 200 mL tap water via nasogastric tube
* Dietary Supplement: Single intragastric instillation of 2 g citric acid in 200 mL tap water via nasogastric tube
* Dietary Supplement: Single intragastric instillation of 2 g salt in 200 mL tap water via nasogastric tube
* Dietary Supplement: Single intragastric instillation of 0.017 g quinine in 200 mL tap water via nasogastric tube
* Dietary Supplement: Single intragastric instillation of 1 g monosodium glutamate in 200 mL tap water via nasogastric tube
* Dietary Supplement: Single intragastric instillation of 25 g glucose in 200 mL tap water via nasogastric tube


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: right-handed healthy males Body-mass index of < 25 Age 18-45 years no drugs non-smoking Exclusion Criteria: Smoking Substance abuse Regular intake of medications (except for oral contraceptives) Medical or psychiatric illness, especially: diabetes, pace-maker, claustrophobia History of gastrointestinal disorders Food allergies, glutamate intolerance Body piercings that cannot be removed

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Male

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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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: 200 mL tap water<br>Single intragastric instillation of 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 200 mL tap water via nasogastric tube<br> <br> |
| Active Comparator: 2 g citric acid<br>Single intragastric instillation of 2 g citric acid in 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 2 g citric acid in 200 mL tap water via nasogastric tube<br> <br> |
| Active Comparator: 2 g salt<br>Single intragastric instillation of 2 g salt in 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 2 g salt in 200 mL tap water via nasogastric tube<br> <br> |
| Active Comparator: 0.017 g quinine<br>Single intragastric instillation of 0.017 g quinine in 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 0.017 g quinine in 200 mL tap water via nasogastric tube<br> <br> |
| Active Comparator: 1 g monosodium glutamate<br>Single intragastric instillation of 1 g monosodium glutamate in 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 1 g monosodium glutamate in 200 mL tap water via nasogastric tube<br> <br> |
| Active Comparator: 25 g glucose<br>Single intragastric instillation of 25 g glucose in 200 mL tap water via nasogastric tube | Dietary Supplement: Single intragastric instillation of 25 g glucose in 200 mL tap water via nasogastric tube<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| regional brain activity assessed by functional Magnetic Resonance Imaging (fMRI) | Changes in resting state functional connectivity | changes from baseline to one hour after treatment | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| gastrointestinal satiation peptide secretion | Unit of Measure: glucagon like peptide-1 (GLP-1) in pg/mL, peptide tyrosine tyrosine (PYY) in pg/mL and gastric inhibitory polypeptide (GIP) in pg/mL | changes from baseline to one hour after treatment | 
| glucose and insulin secretion | Unit of Measure: glucose in mmol/L, insulin in μU/mL | changes from baseline to one hour after treatment |